Progress Energy (PREX) 10-K/A 23 Feb 18 2017 FY Annual report (amended) Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Jan. 31, 2018	Jun. 30, 2017
Document Information [Line Items]
Document Type	10-K
Document Period End Date	Dec. 31, 2017
Amendment Flag	false
Entity Registrant Name	Duke Energy Corporation
Entity Central Index Key	1,326,160
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Well-known Seasoned Issuer	Yes
Entity Common Stock, Shares Outstanding		700,092,667
Entity Public Float			$ 58,468,482,557
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Trading Symbol	DUK
Duke Energy Carolinas [Member]
Document Information [Line Items]
Entity Registrant Name	Duke Energy Carolinas, LLC
Entity Central Index Key	30,371
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Well-known Seasoned Issuer	Yes
Progress Energy [Member]
Document Information [Line Items]
Entity Registrant Name	Progress Energy, Inc.
Entity Central Index Key	1,094,093
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Well-known Seasoned Issuer	No
Duke Energy Progress [Member]
Document Information [Line Items]
Entity Registrant Name	Duke Energy Progress, LLC
Entity Central Index Key	17,797
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Well-known Seasoned Issuer	Yes
Duke Energy Florida [Member]
Document Information [Line Items]
Entity Registrant Name	Duke Energy Florida, LLC
Entity Central Index Key	37,637
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Well-known Seasoned Issuer	Yes
Duke Energy Ohio [Member]
Document Information [Line Items]
Entity Registrant Name	Duke Energy Ohio, Inc.
Entity Central Index Key	20,290
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Well-known Seasoned Issuer	Yes
Duke Energy Indiana [Member]
Document Information [Line Items]
Entity Registrant Name	Duke Energy Indiana, LLC
Entity Central Index Key	81,020
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Well-known Seasoned Issuer	Yes
Piedmont Natural Gas [Member]
Document Information [Line Items]
Entity Registrant Name	Piedmont Natural Gas Company, Inc.
Entity Central Index Key	78,460
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Well-known Seasoned Issuer	Yes

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	2 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015	Oct. 31, 2015
Operating Revenues [Abstract]
Regulated electric		$ 21,177	$ 21,221		$ 21,379
Regulated natural gas		1,734	863		536
Nonregulated electric and other		654	659		456
Total operating revenues		23,565	22,743		22,371
Operating Expenses [Abstract]
Fuel used in electric generation and purchased power		6,350	6,625		7,355
Cost of natural gas		632	265		141
Operation, maintenance and other		5,788	6,085		5,539
Depreciation and amortization		3,527	3,294		3,053
Property and other taxes		1,233	1,142		1,129
Impairment charges		282	18		106
Total operating expenses		17,812	17,429		17,323
Gains on Sales of Other Assets and Other, net		28	27		30
Operating Income		5,781	5,341		5,078
Other Income and Expenses [Abstract]
Equity in earnings (losses) of unconsolidated affiliates		119	(15)		69
Other income and expenses, net		352	324		290
Total other income and expenses		471	309		359
Interest Expense		1,986	1,916		1,527
Income From Continuing Operations Before Income Taxes		4,266	3,734		3,910
Income Tax Expense from Continuing Operations		1,196	1,156		1,256
Income From Continuing Operations		3,070	2,578		2,654
(Loss) Income from Discontinued Operations, net of tax		(6)	(408)		177
Net Income		3,064	2,170		2,831
Less: Net Income Attributable to Noncontrolling Interests		5	18		15
Net Income Attributable to Parent		3,059	2,152		2,816
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Pension and OPEB adjustments		3	(11)		(13)
Net unrealized gain on cash flow hedges		2	17
Reclassification into earnings from cash flow hedges		8	13		9
Unrealized gains on available for sale securities		13	2		(6)
Other comprehensive income (loss), net of tax		26	715		(274)
Comprehensive Income		3,090	2,885		2,557
Less: Comprehensive Income Attributable to Noncontrolling Interests		5	20		4
Comprehensive Income Attributable to Parent		$ 3,085	$ 2,865		$ 2,553
Income from continuing operations attributable to parent common shareholders [Abstract]
Basic		$ 4.37	$ 3.71		$ 3.80
Diluted		4.37	3.71		3.80
(Loss) Income from discontinued operations attributable to Duke Energy Corporation common shareholders [Abstract]
Basic		(0.01)	(0.60)		0.25
Diluted		(0.01)	(0.60)		0.25
Net income attributable to Duke Energy Corporation common shareholders [Abstract]
Basic		4.36	3.11		4.05
Diluted		$ 4.36	$ 3.11		$ 4.05
Weighted average shares outstanding [Abstract]
Basic		700	691		694
Diluted		700	691		694
Duke Energy Carolinas [Member]
Operating Revenues [Abstract]
Total operating revenues		$ 7,302	$ 7,322		$ 7,229
Operating Expenses [Abstract]
Fuel used in electric generation and purchased power		1,822	1,797		1,881
Operation, maintenance and other		1,961	2,106		2,066
Depreciation and amortization		1,090	1,075		1,051
Property and other taxes		281	276		269
Impairment charges			1		1
Total operating expenses		5,154	5,255		5,268
Gains on Sales of Other Assets and Other, net		1	(5)		(1)
Operating Income		2,149	2,062		1,960
Other Income and Expenses [Abstract]
Other income and expenses, net		139	162		160
Total other income and expenses		139	162		160
Interest Expense		422	424		412
Income From Continuing Operations Before Income Taxes		1,866	1,800		1,708
Income Tax Expense from Continuing Operations		652	634		627
Net Income Attributable to Parent		1,214	1,166		1,081
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Reclassification into earnings from cash flow hedges		2	2		1
Unrealized gains on available for sale securities					1
Other comprehensive income (loss), net of tax		2	2		2
Comprehensive Income Attributable to Parent		1,216	1,168		1,083
Progress Energy [Member]
Operating Revenues [Abstract]
Total operating revenues		9,783	9,853		10,277
Operating Expenses [Abstract]
Fuel used in electric generation and purchased power		3,417	3,644		4,224
Operation, maintenance and other		2,220	2,386		2,298
Depreciation and amortization		1,285	1,213		1,116
Property and other taxes		503	487		492
Impairment charges		156	7		12
Total operating expenses		7,581	7,737		8,142
Gains on Sales of Other Assets and Other, net		26	25		25
Operating Income		2,228	2,141		2,160
Other Income and Expenses [Abstract]
Other income and expenses, net		128	114		97
Total other income and expenses		128	114		97
Interest Expense		824	689		670
Income From Continuing Operations Before Income Taxes		1,532	1,566		1,587
Income Tax Expense from Continuing Operations		264	527		522
Income From Continuing Operations		1,268	1,039		1,065
(Loss) Income from Discontinued Operations, net of tax			2		(3)
Net Income		1,268	1,041		1,062
Less: Net Income Attributable to Noncontrolling Interests		10	10		11
Net Income Attributable to Parent		1,258	1,031		1,051
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Pension and OPEB adjustments		4	1		(10)
Net unrealized gain on cash flow hedges		5
Reclassification into earnings from cash flow hedges			8		4
Unrealized gains on available for sale securities		4	1		(1)
Other comprehensive income (loss), net of tax		13	10		(7)
Comprehensive Income		1,281	1,051		1,055
Less: Comprehensive Income Attributable to Noncontrolling Interests		10	10		11
Comprehensive Income Attributable to Parent		1,271	1,041		1,044
Duke Energy Progress [Member]
Operating Revenues [Abstract]
Total operating revenues		5,129	5,277		5,290
Operating Expenses [Abstract]
Fuel used in electric generation and purchased power		1,609	1,830		2,029
Operation, maintenance and other		1,389	1,504		1,452
Depreciation and amortization		725	703		643
Property and other taxes		156	156		140
Impairment charges		19	1		5
Total operating expenses		3,898	4,194		4,269
Gains on Sales of Other Assets and Other, net		4	3		3
Operating Income		1,235	1,086		1,024
Other Income and Expenses [Abstract]
Other income and expenses, net		65	71		71
Total other income and expenses		65	71		71
Interest Expense		293	257		235
Income From Continuing Operations Before Income Taxes		1,007	900		860
Income Tax Expense from Continuing Operations		292	301		294
Net Income Attributable to Parent		715	599		566
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Comprehensive Income Attributable to Parent		715	599		566
Duke Energy Florida [Member]
Operating Revenues [Abstract]
Total operating revenues		4,646	4,568		4,977
Operating Expenses [Abstract]
Fuel used in electric generation and purchased power		1,808	1,814		2,195
Operation, maintenance and other		818	865		835
Depreciation and amortization		560	509		473
Property and other taxes		347	333		352
Impairment charges		138	6		7
Total operating expenses		3,671	3,527		3,862
Gains on Sales of Other Assets and Other, net		1
Operating Income		976	1,041		1,115
Other Income and Expenses [Abstract]
Other income and expenses, net		61	44		24
Total other income and expenses		61	44		24
Interest Expense		279	212		198
Income From Continuing Operations Before Income Taxes		758	873		941
Income Tax Expense from Continuing Operations		46	322		342
Net Income Attributable to Parent		712	551		599
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Unrealized gains on available for sale securities		3	1
Other comprehensive income (loss), net of tax		3	1
Comprehensive Income Attributable to Parent		715	552		599
Duke Energy Ohio [Member]
Operating Revenues [Abstract]
Regulated electric		1,373	1,410		1,331
Regulated natural gas		508	503		541
Nonregulated electric and other		42	31		33
Total operating revenues		1,923	1,944		1,905
Operating Expenses [Abstract]
Fuel used in electric generation and purchased power		369	442		446
Fuel used in electric generation and purchased power - nonregulated		58	51		47
Cost of natural gas		107	103		141
Operation, maintenance and other		524	512		495
Depreciation and amortization		261	233		227
Property and other taxes		278	258		254
Impairment charges		1
Total operating expenses		1,598	1,599		1,610
Gains on Sales of Other Assets and Other, net		1	2		8
Operating Income		326	347		303
Other Income and Expenses [Abstract]
Other income and expenses, net		17	9		6
Total other income and expenses		17	9		6
Interest Expense		91	86		79
Income From Continuing Operations Before Income Taxes		252	270		230
Income Tax Expense from Continuing Operations		59	78		81
Income From Continuing Operations		193	192		149
(Loss) Income from Discontinued Operations, net of tax		(1)	36		23
Net Income Attributable to Parent		192	228		172
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Comprehensive Income Attributable to Parent		192	228		172
Duke Energy Indiana [Member]
Operating Revenues [Abstract]
Total operating revenues		3,047	2,958		2,890
Operating Expenses [Abstract]
Fuel used in electric generation and purchased power		966	909		982
Operation, maintenance and other		733	723		682
Depreciation and amortization		458	496		434
Property and other taxes		76	58		61
Impairment charges		18	8		88
Total operating expenses		2,251	2,194		2,247
Gains on Sales of Other Assets and Other, net			1		1
Operating Income		796	765		644
Other Income and Expenses [Abstract]
Other income and expenses, net		37	22		11
Total other income and expenses		37	22		11
Interest Expense		178	181		176
Income From Continuing Operations Before Income Taxes		655	606		479
Income Tax Expense from Continuing Operations		301	225		163
Net Income Attributable to Parent		354	381		316
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Reclassification into earnings from cash flow hedges			(1)		(2)
Other comprehensive income (loss), net of tax			(1)		(2)
Comprehensive Income Attributable to Parent		354	$ 380		$ 314
Piedmont Natural Gas [Member]
Operating Revenues [Abstract]
Regulated natural gas	$ 320	1,319		$ 1,139		$ 1,372
Nonregulated electric and other	2	9		10		11
Total operating revenues	322	1,328		1,149		1,383
Operating Expenses [Abstract]
Cost of natural gas	144	524		391		644
Operation, maintenance and other	52	315		353		305
Depreciation and amortization	23	148		137		129
Property and other taxes	7	48		43		42
Impairment charges		7
Total operating expenses	226	1,042		924		1,120
Operating Income	96	286		225		263
Other Income and Expenses [Abstract]
Equity in earnings (losses) of unconsolidated affiliates	2	(6)		29		34
Gain on sale of unconsolidated affiliates				133
Other income and expenses, net				(1)		(1)
Total other income and expenses	2	(6)		161		33
Interest Expense	12	79		69		69
Income From Continuing Operations Before Income Taxes	86	201		317		227
Income Tax Expense from Continuing Operations	32	62		124		90
Net Income Attributable to Parent	54	139		193		137
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Net unrealized gain on cash flow hedges				(3)		(2)
Reclassification into earnings from cash flow hedges				4		1
Other comprehensive income (loss), net of tax				1		(1)
Comprehensive Income Attributable to Parent	$ 54	$ 139		$ 194		$ 136

Consolidated Statements of Ope3

Consolidated Statements of Operations (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	$ 3,085	$ 2,865	$ 2,553
Duke Energy Progress [Member]
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	715	599	566
Duke Energy Ohio [Member]
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	$ 192	$ 228	$ 172

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 3,064	$ 2,170	$ 2,831
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Foreign currency translation adjustments	0	694	(264)
Pension and OPEB adjustments	3	(11)	(13)
Net unrealized gains on cash flow hedges	2	17
Reclassification into earnings from cash flow hedges	8	13	9
Unrealized gains (losses) on available-for-sale securities	13	2	(6)
Other comprehensive income (loss), net of tax	26	715	(274)
Comprehensive Income	3,090	2,885	2,557
Less: Comprehensive Income Attributable to Noncontrolling Interests	5	20	4
Comprehensive Income Attributable to Parent	$ 3,085	$ 2,865	$ 2,553

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Current Assets [Abstract]
Cash and cash equivalents	$ 358	$ 392
Receivables (net of allowance for doubtful accounts)	779	751
Receivables of VIEs (net of allowance for doubtful accounts)	1,995	1,893
Inventory	3,250	3,522
Regulatory assets	1,437	1,023
Other	634	458
Total current assets	8,453	8,039
Property, Plant and Equipment [Abstract]
Cost	127,507	121,397
Accumulated depreciation and amortization	(41,537)	(39,406)
Generation facilities to be retired, net	421	529
Net property, plant and equipment	86,391	82,520
Other Noncurrent Assets
Goodwill	19,396	19,425
Regulatory assets	12,442	12,878
Nuclear decommissioning trust funds	7,097	6,205
Investments in equity method unconsolidated affiliates	1,175	925
Other	2,960	2,769
Total other noncurrent assets	43,070	42,202
Total Assets	137,914	132,761
Current Liabilities [Abstract]
Accounts payable	3,043	2,994
Notes payable and commercial paper	2,163	2,487
Taxes accrued	551	384
Interest accrued	525	503
Current maturities of long-term debt	3,244	2,319
Asset retirement obligations	689	411
Regulatory liabilities	402	409
Other	1,865	2,044
Total current liabilities	12,482	11,551
Long-Term Debt	49,035	45,576
Other Noncurrent Liabilities [Abstract]
Deferred income taxes	6,621	14,155
Asset retirement obligations	9,486	10,200
Regulatory liabilities	15,330	6,881
Accrued pension and other post-retirement benefit costs	1,103	1,111
Investment tax credits	539	493
Other	1,581	1,753
Total other noncurrent liabilities	34,660	34,593
Commitments and Contingencies
Equity [Abstract]
Common stock	1	1
Additional paid-in capital	38,792	38,741
Retained earnings	3,013	2,384
Accumulated other comprehensive (loss) income	(67)	(93)
Total Parent stockholders' equity	41,739	41,033
Noncontrolling interests	(2)	8
Total equity	41,737	41,041
Total Liabilities and Equity	137,914	132,761
Duke Energy Carolinas [Member]
Current Assets [Abstract]
Cash and cash equivalents	16	14
Receivables (net of allowance for doubtful accounts)	200	160
Receivables of VIEs (net of allowance for doubtful accounts)	640	645
Receivables from affiliated companies	95	163
Notes receivable from affiliated companies		66
Inventory	971	1,055
Regulatory assets	299	238
Other	19	37
Total current assets	2,240	2,378
Property, Plant and Equipment [Abstract]
Cost	42,939	41,127
Accumulated depreciation and amortization	(15,063)	(14,365)
Net property, plant and equipment	27,876	26,762
Other Noncurrent Assets
Regulatory assets	2,853	3,159
Nuclear decommissioning trust funds	3,772	3,273
Other	979	943
Total other noncurrent assets	7,604	7,375
Total Assets	37,720	36,515
Current Liabilities [Abstract]
Accounts payable	842	833
Accounts payable to affiliated companies	209	247
Notes payable to affiliated companies	104
Taxes accrued	234	143
Interest accrued	108	102
Current maturities of long-term debt	1,205	116
Asset retirement obligations	337	222
Regulatory liabilities	126	161
Other	486	468
Total current liabilities	3,651	2,292
Long-Term Debt	8,598	9,187
Long-Term Debt Payable to Affiliated Companies	300	300
Other Noncurrent Liabilities [Abstract]
Deferred income taxes	3,413	6,544
Asset retirement obligations	3,273	3,673
Regulatory liabilities	6,231	2,840
Accrued pension and other post-retirement benefit costs	95	97
Investment tax credits	232	203
Other	566	607
Total other noncurrent liabilities	13,810	13,964
Commitments and Contingencies
Equity [Abstract]
Member's equity	11,368	10,781
Accumulated other comprehensive (loss) income	(7)	(9)
Total member's equity	11,361	10,772
Total Liabilities and Equity	37,720	36,515
Progress Energy [Member]
Current Assets [Abstract]
Cash and cash equivalents	40	46
Receivables (net of allowance for doubtful accounts)	123	114
Receivables of VIEs (net of allowance for doubtful accounts)	780	692
Receivables from affiliated companies	31	106
Notes receivable from affiliated companies	240	80
Inventory	1,592	1,717
Regulatory assets	741	401
Other	334	148
Total current assets	3,881	3,304
Property, Plant and Equipment [Abstract]
Cost	47,323	44,864
Accumulated depreciation and amortization	(15,857)	(15,212)
Generation facilities to be retired, net	421	529
Net property, plant and equipment	31,887	30,181
Other Noncurrent Assets
Goodwill	3,655	3,655
Regulatory assets	6,010	5,722
Nuclear decommissioning trust funds	3,324	2,932
Other	931	856
Total other noncurrent assets	13,920	13,165
Total Assets	49,688	46,650
Current Liabilities [Abstract]
Accounts payable	1,006	1,003
Accounts payable to affiliated companies	251	348
Notes payable to affiliated companies	805	729
Taxes accrued	101	83
Interest accrued	212	201
Current maturities of long-term debt	771	778
Asset retirement obligations	295	189
Regulatory liabilities	213	189
Other	729	745
Total current liabilities	4,383	4,265
Long-Term Debt	16,916	15,590
Long-Term Debt Payable to Affiliated Companies	150	1,173
Other Noncurrent Liabilities [Abstract]
Deferred income taxes	3,502	5,246
Asset retirement obligations	5,119	5,286
Regulatory liabilities	5,306	2,395
Accrued pension and other post-retirement benefit costs	545	547
Other	302	341
Total other noncurrent liabilities	14,774	13,815
Commitments and Contingencies
Equity [Abstract]
Additional paid-in capital	9,143	8,094
Retained earnings	4,350	3,764
Accumulated other comprehensive (loss) income	(25)	(38)
Total Parent stockholders' equity	13,468	11,820
Noncontrolling interests	(3)	(13)
Total equity	13,465	11,807
Total Liabilities and Equity	49,688	46,650
Duke Energy Progress [Member]
Current Assets [Abstract]
Cash and cash equivalents	20	11
Receivables (net of allowance for doubtful accounts)	56	51
Receivables of VIEs (net of allowance for doubtful accounts)	459	404
Receivables from affiliated companies	3	5
Notes receivable from affiliated companies		165
Inventory	1,017	1,076
Regulatory assets	352	188
Other	97	57
Total current assets	2,004	1,957
Property, Plant and Equipment [Abstract]
Cost	29,583	28,419
Accumulated depreciation and amortization	(10,903)	(10,561)
Generation facilities to be retired, net	421	529
Net property, plant and equipment	19,101	18,387
Other Noncurrent Assets
Regulatory assets	3,507	3,243
Nuclear decommissioning trust funds	2,588	2,217
Other	599	525
Total other noncurrent assets	6,694	5,985
Total Assets	27,799	26,329
Current Liabilities [Abstract]
Accounts payable	402	589
Accounts payable to affiliated companies	179	227
Notes payable to affiliated companies	240
Taxes accrued	64	104
Interest accrued	102	102
Current maturities of long-term debt	3	452
Asset retirement obligations	295	189
Regulatory liabilities	139	158
Other	376	365
Total current liabilities	1,800	2,186
Long-Term Debt	7,204	6,409
Long-Term Debt Payable to Affiliated Companies	150	150
Other Noncurrent Liabilities [Abstract]
Deferred income taxes	1,883	3,323
Asset retirement obligations	4,378	4,508
Regulatory liabilities	3,999	1,946
Accrued pension and other post-retirement benefit costs	248	252
Investment tax credits	143	146
Other	45	51
Total other noncurrent liabilities	10,696	10,226
Equity [Abstract]
Total member's equity	7,949	7,358
Total Liabilities and Equity	27,799	26,329
Duke Energy Florida [Member]
Current Assets [Abstract]
Cash and cash equivalents	13	16
Receivables (net of allowance for doubtful accounts)	65	61
Receivables of VIEs (net of allowance for doubtful accounts)	321	288
Receivables from affiliated companies	2	5
Notes receivable from affiliated companies	313
Inventory	574	641
Regulatory assets	389	213
Other	86	125
Total current assets	1,763	1,349
Property, Plant and Equipment [Abstract]
Cost	17,730	16,434
Accumulated depreciation and amortization	(4,947)	(4,644)
Net property, plant and equipment	12,783	11,790
Other Noncurrent Assets
Regulatory assets	2,503	2,480
Nuclear decommissioning trust funds	736	715
Other	284	278
Total other noncurrent assets	3,523	3,473
Total Assets	18,069	16,612
Current Liabilities [Abstract]
Accounts payable	602	413
Accounts payable to affiliated companies	74	125
Notes payable to affiliated companies		297
Taxes accrued	34	33
Interest accrued	56	49
Current maturities of long-term debt	768	326
Regulatory liabilities	74	31
Other	334	352
Total current liabilities	1,942	1,626
Long-Term Debt	6,327	5,799
Other Noncurrent Liabilities [Abstract]
Deferred income taxes	1,761	2,694
Asset retirement obligations	742	778
Regulatory liabilities	1,307	448
Accrued pension and other post-retirement benefit costs	264	262
Other	108	105
Total other noncurrent liabilities	4,182	4,287
Equity [Abstract]
Member's equity	5,614	4,899
Accumulated other comprehensive (loss) income	4	1
Total member's equity	5,618	4,900
Total Liabilities and Equity	18,069	16,612
Duke Energy Ohio [Member]
Current Assets [Abstract]
Cash and cash equivalents	12	13
Receivables (net of allowance for doubtful accounts)	68	71
Receivables from affiliated companies	133	129
Notes receivable from affiliated companies	14	94
Inventory	133	137
Regulatory assets	49	37
Other	39	37
Total current assets	448	518
Property, Plant and Equipment [Abstract]
Cost	8,732	8,126
Accumulated depreciation and amortization	(2,691)	(2,579)
Net property, plant and equipment	6,041	5,547
Other Noncurrent Assets
Goodwill	920	920
Regulatory assets	445	520
Other	21	23
Total other noncurrent assets	1,386	1,463
Total Assets	7,875	7,528
Current Liabilities [Abstract]
Accounts payable	313	282
Accounts payable to affiliated companies	62	63
Notes payable to affiliated companies	29	16
Taxes accrued	190	178
Interest accrued	21	19
Current maturities of long-term debt	3	1
Asset retirement obligations	3
Regulatory liabilities	36	21
Other	71	91
Total current liabilities	728	671
Long-Term Debt	2,039	1,858
Long-Term Debt Payable to Affiliated Companies	25	25
Other Noncurrent Liabilities [Abstract]
Deferred income taxes	781	1,443
Asset retirement obligations	81	77
Regulatory liabilities	891	236
Accrued pension and other post-retirement benefit costs	59	56
Other	108	166
Total other noncurrent liabilities	1,920	1,978
Equity [Abstract]
Common stock	762	762
Additional paid-in capital	2,670	2,695
Retained earnings	(269)	(461)
Total Parent stockholders' equity	3,163	2,996
Total Liabilities and Equity	7,875	7,528
Duke Energy Indiana [Member]
Current Assets [Abstract]
Cash and cash equivalents	9	17
Receivables (net of allowance for doubtful accounts)	57	105
Receivables from affiliated companies	125	114
Notes receivable from affiliated companies		86
Inventory	450	504
Regulatory assets	165	149
Other	30	45
Total current assets	836	1,020
Property, Plant and Equipment [Abstract]
Cost	14,948	14,241
Accumulated depreciation and amortization	(4,662)	(4,317)
Net property, plant and equipment	10,286	9,924
Other Noncurrent Assets
Regulatory assets	978	1,073
Other	189	147
Total other noncurrent assets	1,167	1,220
Total Assets	12,289	12,164
Current Liabilities [Abstract]
Accounts payable	196	263
Accounts payable to affiliated companies	78	74
Notes payable to affiliated companies	161	0
Taxes accrued	95	31
Interest accrued	57	61
Current maturities of long-term debt	3	3
Asset retirement obligations	54
Regulatory liabilities	24	40
Other	104	93
Total current liabilities	772	565
Long-Term Debt	3,630	3,633
Long-Term Debt Payable to Affiliated Companies	150	150
Other Noncurrent Liabilities [Abstract]
Deferred income taxes	925	1,900
Asset retirement obligations	727	866
Regulatory liabilities	1,723	748
Accrued pension and other post-retirement benefit costs	76	71
Investment tax credits	147	137
Other	18	27
Total other noncurrent liabilities	3,616	3,749
Equity [Abstract]
Total member's equity	4,121	4,067
Total Liabilities and Equity	12,289	12,164
Piedmont Natural Gas [Member]
Current Assets [Abstract]
Cash and cash equivalents	19	25
Receivables (net of allowance for doubtful accounts)	275	232
Receivables from affiliated companies	7	7
Inventory	66	66
Regulatory assets	95	124
Other	52	21
Total current assets	514	475
Property, Plant and Equipment [Abstract]
Cost	6,725	6,174
Accumulated depreciation and amortization	(1,479)	(1,360)
Net property, plant and equipment	5,246	4,814
Other Noncurrent Assets
Goodwill	49	49
Regulatory assets	283	373
Investments in equity method unconsolidated affiliates	61	212
Other	65	21
Total other noncurrent assets	458	655
Total Assets	6,218	5,944
Current Liabilities [Abstract]
Accounts payable	125	155
Accounts payable to affiliated companies	13	8
Notes payable and commercial paper		330
Notes payable to affiliated companies	364
Taxes accrued	19	67
Interest accrued	31	33
Current maturities of long-term debt	250	35
Regulatory liabilities	3	0
Other	69	102
Total current liabilities	874	730
Long-Term Debt	1,787	1,786
Other Noncurrent Liabilities [Abstract]
Deferred income taxes	564	931
Asset retirement obligations	15	14
Regulatory liabilities	1,141	608
Accrued pension and other post-retirement benefit costs	5	14
Other	170	189
Total other noncurrent liabilities	1,895	1,756
Equity [Abstract]
Common stock	860	860
Retained earnings	802	812
Total Parent stockholders' equity	1,662	1,672
Total Liabilities and Equity	$ 6,218	$ 5,944

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Allowance for doubtful accounts - receivables	$ 14	$ 14
Regulatory assets	1,437	1,023
Regulatory assets, noncurrent	12,442	12,878
Other	634	458
Current maturities of long-term debt	3,244	2,319
Long-Term Debt	$ 49,035	$ 45,576
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	2,000,000,000	2,000,000,000
Common stock, shares outstanding	700,000,000	700,000,000
Variable Interest Entity [Member]
Allowance for doubtful accounts - receivables of VIEs	$ 54	$ 54
Regulatory assets	51	50
Regulatory assets, noncurrent	1,091	1,142
Current maturities of long-term debt	225	260
Long-Term Debt	4,306	3,587
Duke Energy Carolinas [Member]
Allowance for doubtful accounts - receivables	2	2
Regulatory assets	299	238
Regulatory assets, noncurrent	2,853	3,159
Other	19	37
Current maturities of long-term debt	1,205	116
Long-Term Debt	8,598	9,187
Duke Energy Carolinas [Member] | Variable Interest Entity [Member]
Allowance for doubtful accounts - receivables of VIEs	7	7
Progress Energy [Member]
Allowance for doubtful accounts - receivables	4	6
Regulatory assets	741	401
Regulatory assets, noncurrent	6,010	5,722
Other	334	148
Current maturities of long-term debt	771	778
Long-Term Debt	$ 16,916	$ 15,590
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	100	100
Common stock, shares outstanding	100	100
Progress Energy [Member] | Variable Interest Entity [Member]
Allowance for doubtful accounts - receivables of VIEs	$ 7	$ 7
Regulatory assets	51	50
Regulatory assets, noncurrent	1,091	1,142
Current maturities of long-term debt	53	62
Long-Term Debt	1,689	1,741
Duke Energy Progress [Member]
Allowance for doubtful accounts - receivables	1	4
Regulatory assets	352	188
Regulatory assets, noncurrent	3,507	3,243
Other	97	57
Current maturities of long-term debt	3	452
Long-Term Debt	7,204	6,409
Duke Energy Progress [Member] | Variable Interest Entity [Member]
Allowance for doubtful accounts - receivables of VIEs	5	5
Duke Energy Florida [Member]
Allowance for doubtful accounts - receivables	3	2
Regulatory assets	389	213
Regulatory assets, noncurrent	2,503	2,480
Other	86	125
Current maturities of long-term debt	768	326
Long-Term Debt	6,327	5,799
Duke Energy Florida [Member] | Variable Interest Entity [Member]
Allowance for doubtful accounts - receivables of VIEs	2	2
Regulatory assets	51	50
Regulatory assets, noncurrent	1,091	1,142
Other	40	53
Current maturities of long-term debt	53	62
Long-Term Debt	1,389	1,442
Duke Energy Ohio [Member]
Allowance for doubtful accounts - receivables	3	2
Regulatory assets	49	37
Regulatory assets, noncurrent	445	520
Other	39	37
Current maturities of long-term debt	3	1
Long-Term Debt	$ 2,039	$ 1,858
Common stock, par value	$ 8.50	$ 8.50
Common stock, shares authorized	120,000,000	120,000,000
Common stock, shares outstanding	90,000,000	90,000,000
Duke Energy Indiana [Member]
Allowance for doubtful accounts - receivables	$ 2	$ 1
Regulatory assets	165	149
Regulatory assets, noncurrent	978	1,073
Other	30	45
Current maturities of long-term debt	3	3
Long-Term Debt	3,630	3,633
Piedmont Natural Gas [Member]
Allowance for doubtful accounts - receivables	2	3
Regulatory assets	95	124
Regulatory assets, noncurrent	283	373
Other	52	21
Current maturities of long-term debt	250	35
Long-Term Debt	$ 1,787	$ 1,786
Common stock, shares authorized	100	100
Common stock, shares outstanding	100	100

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	2 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015	Oct. 31, 2015
CASH FLOWS FROM OPERATING ACTIVITIES [Abstract]
Net income		$ 3,064	$ 2,170		$ 2,831
Net Income Attributable to Parent		3,059	2,152		2,816
Adjustments to reconcile net income to net cash provided by operating activities: [Abstract]
Depreciation, amortization and accretion (including amortization of nuclear fuel)		4,046	3,880		3,613
Equity component of AFUDC		(237)	(200)		(164)
(Gains) losses on sales of other assets		(33)	477		(48)
Impairment charges		282	212		153
Deferred income taxes		1,433	900		1,244
Equity in (earnings) losses of unconsolidated affiliates		(119)	15		(69)
Accrued pension and other post-retirement benefit costs		8	21		71
Contributions to qualified pension plans		(19)	(155)		(302)
Payments for asset retirement obligations		(571)	(608)		(346)
(Increase) decrease in [Abstract]
Net realized and unrealized mark-to-market and hedging transactions		18	34		(29)
Receivables		(83)	(372)		383
Inventory		268	272		(237)
Other current assets		(388)	(220)		(65)
Increase (decrease) in [Abstract]
Accounts payable		(204)	296		(6)
Taxes accrued		149	236		(38)
Other current liabilities		(482)	182		168
Other assets		(438)	(186)		(216)
Other liabilities		(60)	(137)		(243)
Net cash provided by (used in) operating activities		6,634	6,817		6,700
CASH FLOWS FROM INVESTING ACTIVITIES [Abstract]
Capital expenditures		(8,052)	(7,901)		(6,766)
Contributions to equity method investments		(414)	(307)		(263)
Acquisitions, net of cash acquired		(13)	(4,778)		(1,334)
Return of investment capital		281	1		3
Purchases of available-for-sale securities		(4,071)	(5,153)		(4,037)
Proceeds from sales and maturities of available-for-sale securities		4,098	5,236		4,040
Proceeds from the sales of discontinued operations and other assets, net of cash divested			1,418		2,968
Change in Restricted Cash		(10)	(4)		191
Other		(269)	(45)		(79)
Net cash used in investing activities		(8,450)	(11,533)		(5,277)
CASH FLOWS FROM FINANCING ACTIVITIES [Abstract]
Proceeds from the issuance of long-term debt		6,909	9,238		2,955
Proceeds from Issuance of Common Stock			731		17
Payments for the redemption of long-term debt		(2,316)	(1,923)		(3,029)
Proceeds from issuance of short-term debt with original maturities greater than 90 days		319	2,081		379
Payments for the redemption of short-term debt with original maturities greater than 90 days		(272)	(2,166)		(931)
Notes payable and commercial paper		(409)	(1,362)		1,797
Dividends paid		(2,450)	(2,332)		(2,254)
Repurchase of common shares					(1,500)
Other		1	(16)		(36)
Net cash provided by (used in) financing activities		1,782	4,251		(2,602)
Changes in Cash and Cash Equivalents included in asses held for sale			474		1,099
Net (decrease) increase in cash and cash equivalents		(34)	9		(80)
Cash and cash equivalents at beginning of period		392	383		463
Cash and cash equivalents at end of period	$ 392	358	392		383
Supplemental Disclosures [Abstract]
Cash paid for interest, net of amount capitalized		1,963	1,794		1,607
Cash paid for (received from) income taxes		4	229		170
Significant Non-cash Transactions [Abstract]
Accrued capital expenditures		1,032	1,000		771
Duke Energy Carolinas [Member]
CASH FLOWS FROM OPERATING ACTIVITIES [Abstract]
Net Income Attributable to Parent		1,214	1,166		1,081
Adjustments to reconcile net income to net cash provided by operating activities: [Abstract]
Depreciation, amortization and accretion (including amortization of nuclear fuel)		1,409	1,382		1,361
Equity component of AFUDC		(106)	(102)		(96)
(Gains) losses on sales of other assets		(1)	5		1
Impairment charges			1		1
Deferred income taxes		410	470		397
Accrued pension and other post-retirement benefit costs		(4)	4		15
Contributions to qualified pension plans			(43)		(91)
Payments for asset retirement obligations		(271)	(287)		(167)
(Increase) decrease in [Abstract]
Net realized and unrealized mark-to-market and hedging transactions		9	5
Receivables		(9)	(76)		42
Receivables from affiliated companies		68	(56)		(32)
Inventory		78	215		(157)
Other current assets		7	67		(51)
Increase (decrease) in [Abstract]
Accounts payable		23	(69)		(4)
Accounts payable to affiliated companies		(38)	18		75
Taxes accrued		86	187		(128)
Other current liabilities		(161)	63		127
Other assets		(49)	20		76
Other liabilities		(31)	6		(77)
Net cash provided by (used in) operating activities		2,634	2,976		2,373
CASH FLOWS FROM INVESTING ACTIVITIES [Abstract]
Capital expenditures		(2,524)	(2,220)		(1,933)
Purchases of available-for-sale securities		(2,124)	(2,832)		(2,555)
Proceeds from sales and maturities of available-for-sale securities		2,128	2,832		2,555
Notes receivable from affiliated companies		66	97		(13)
Other		(109)	(83)		(35)
Net cash used in investing activities		(2,563)	(2,206)		(1,981)
CASH FLOWS FROM FINANCING ACTIVITIES [Abstract]
Proceeds from the issuance of long-term debt		569	1,587		516
Payments for the redemption of long-term debt		(116)	(356)		(506)
Notes payable to affiliated companies		104
Distributions to parent		(625)	(2,000)		(401)
Other		(1)			(1)
Net cash provided by (used in) financing activities		(69)	(769)		(392)
Net (decrease) increase in cash and cash equivalents		2	1		0
Cash and cash equivalents at beginning of period		14	13		13
Cash and cash equivalents at end of period	14	16	14		13
Supplemental Disclosures [Abstract]
Cash paid for interest, net of amount capitalized		398	393		389
Cash paid for (received from) income taxes		193	(60)		342
Significant Non-cash Transactions [Abstract]
Accrued capital expenditures		315	347		239
Progress Energy [Member]
CASH FLOWS FROM OPERATING ACTIVITIES [Abstract]
Net income		1,268	1,041		1,062
Net Income Attributable to Parent		1,258	1,031		1,051
Adjustments to reconcile net income to net cash provided by operating activities: [Abstract]
Depreciation, amortization and accretion (including amortization of nuclear fuel)		1,516	1,435		1,312
Equity component of AFUDC		(92)	(76)		(54)
(Gains) losses on sales of other assets		(28)	(34)		(31)
Impairment charges		156	7		12
Deferred income taxes		703	532		714
Accrued pension and other post-retirement benefit costs		(28)	(24)		(5)
Contributions to qualified pension plans			(43)		(83)
Payments for asset retirement obligations		(248)	(270)		(156)
(Increase) decrease in [Abstract]
Net realized and unrealized mark-to-market and hedging transactions			42		(6)
Receivables		(89)	7		105
Receivables from affiliated companies		71	211		(316)
Inventory		125	35		(67)
Other current assets		(384)	3		553
Increase (decrease) in [Abstract]
Accounts payable		(260)	252		(193)
Accounts payable to affiliated companies		(97)	37		108
Taxes accrued		17	15		(63)
Other current liabilities		(166)	(42)		136
Other assets		(301)	(248)		(167)
Other liabilities		(98)	(36)		(112)
Net cash provided by (used in) operating activities		2,065	2,844		2,749
CASH FLOWS FROM INVESTING ACTIVITIES [Abstract]
Capital expenditures		(3,152)	(3,306)		(2,698)
Asset acquisitions			(10)		(1,249)
Purchases of available-for-sale securities		(1,806)	(2,143)		(1,174)
Proceeds from sales and maturities of available-for-sale securities		1,824	2,187		1,211
Proceeds from insurance		7	58
Proceeds from the sale of nuclear fuel		20	20		102
Notes receivable from affiliated companies		(160)	(80)		220
Change in Restricted Cash		5	(6)
Other		(86)	47		(34)
Net cash used in investing activities		(3,348)	(3,233)		(3,622)
CASH FLOWS FROM FINANCING ACTIVITIES [Abstract]
Proceeds from the issuance of long-term debt		2,118	2,375		1,186
Payments for the redemption of long-term debt		(813)	(327)		(1,553)
Notes payable to affiliated companies		100	444		623
Capital contribution from parent					625
Dividends to parent		(124)	(2,098)
Other		(4)	(3)		(6)
Net cash provided by (used in) financing activities		1,277	391		875
Net (decrease) increase in cash and cash equivalents		(6)	2		2
Cash and cash equivalents at beginning of period		46	44		42
Cash and cash equivalents at end of period	46	40	46		44
Supplemental Disclosures [Abstract]
Cash paid for interest, net of amount capitalized		773	673		649
Cash paid for (received from) income taxes		(146)	(187)		(426)
Significant Non-cash Transactions [Abstract]
Accrued capital expenditures		391	317		329
Equitization of certain notes payable to affiliates		1,047
Dividend to parent related to a legal entity restructuring		547
Duke Energy Progress [Member]
CASH FLOWS FROM OPERATING ACTIVITIES [Abstract]
Net Income Attributable to Parent		715	599		566
Adjustments to reconcile net income to net cash provided by operating activities: [Abstract]
Depreciation, amortization and accretion (including amortization of nuclear fuel)		936	907		821
Equity component of AFUDC		(47)	(50)		(47)
(Gains) losses on sales of other assets		(5)	(6)		(7)
Impairment charges		19	1		5
Deferred income taxes		384	384		354
Accrued pension and other post-retirement benefit costs		(20)	(32)		(14)
Contributions to qualified pension plans			(24)		(42)
Payments for asset retirement obligations		(192)	(212)		(109)
(Increase) decrease in [Abstract]
Net realized and unrealized mark-to-market and hedging transactions		(4)	4		(3)
Receivables		(58)	(17)		43
Receivables from affiliated companies		2	11		(6)
Inventory		59	12		(50)
Other current assets		(75)	84		185
Increase (decrease) in [Abstract]
Accounts payable		(230)	181		(65)
Accounts payable to affiliated companies		(48)	37		70
Taxes accrued		(39)	90		(34)
Other current liabilities		(131)	114		76
Other assets		(53)	(163)		(83)
Other liabilities		(18)	12		(66)
Net cash provided by (used in) operating activities		1,195	1,932		1,594
CASH FLOWS FROM INVESTING ACTIVITIES [Abstract]
Capital expenditures		(1,715)	(1,733)		(1,669)
Asset acquisitions					(1,249)
Purchases of available-for-sale securities		(1,249)	(1,658)		(727)
Proceeds from sales and maturities of available-for-sale securities		1,207	1,615		672
Proceeds from insurance		4
Notes receivable from affiliated companies		165	(165)		237
Other		(55)	26		(30)
Net cash used in investing activities		(1,643)	(1,915)		(2,766)
CASH FLOWS FROM FINANCING ACTIVITIES [Abstract]
Proceeds from the issuance of long-term debt		812	505		1,186
Payments for the redemption of long-term debt		(470)	(15)		(991)
Notes payable to affiliated companies		240	(209)		359
Capital contribution from parent					626
Distributions to parent		(124)	(300)
Other		(1)	(2)		(2)
Net cash provided by (used in) financing activities		457	(21)		1,178
Net (decrease) increase in cash and cash equivalents		9	(4)		6
Cash and cash equivalents at beginning of period		11	15		9
Cash and cash equivalents at end of period	11	20	11		15
Supplemental Disclosures [Abstract]
Cash paid for interest, net of amount capitalized		291	248		218
Cash paid for (received from) income taxes		59	(287)		(197)
Significant Non-cash Transactions [Abstract]
Accrued capital expenditures		191	147		143
Duke Energy Florida [Member]
CASH FLOWS FROM OPERATING ACTIVITIES [Abstract]
Net Income Attributable to Parent		712	551		599
Adjustments to reconcile net income to net cash provided by operating activities: [Abstract]
Depreciation, amortization and accretion (including amortization of nuclear fuel)		570	516		480
Equity component of AFUDC		(45)	(26)		(7)
(Gains) losses on sales of other assets		(1)
Impairment charges		138	6		7
Deferred income taxes		245	224		348
Accrued pension and other post-retirement benefit costs		(13)	2		5
Contributions to qualified pension plans			(20)		(40)
Payments for asset retirement obligations		(56)	(58)		(47)
(Increase) decrease in [Abstract]
Net realized and unrealized mark-to-market and hedging transactions		5	38		(3)
Receivables		(38)	23		61
Receivables from affiliated companies			21		(44)
Inventory		66	23		(17)
Other current assets		(125)	(133)		116
Increase (decrease) in [Abstract]
Accounts payable		(32)	71		(127)
Accounts payable to affiliated companies		(51)	9		46
Taxes accrued		1	(117)		67
Other current liabilities		(37)	(149)		57
Other assets		(229)	(84)		(84)
Other liabilities		(82)	(53)		(44)
Net cash provided by (used in) operating activities		1,028	844		1,373
CASH FLOWS FROM INVESTING ACTIVITIES [Abstract]
Capital expenditures		(1,437)	(1,583)		(1,029)
Purchases of available-for-sale securities		(557)	(485)		(447)
Proceeds from sales and maturities of available-for-sale securities		617	572		538
Proceeds from insurance		4	58
Proceeds from the sale of nuclear fuel		20	20		102
Notes receivable from affiliated companies		(313)
Change in Restricted Cash			(6)
Other		(31)	21		(3)
Net cash used in investing activities		(1,697)	(1,403)		(839)
CASH FLOWS FROM FINANCING ACTIVITIES [Abstract]
Proceeds from the issuance of long-term debt		1,306	1,870
Payments for the redemption of long-term debt		(342)	(12)		(562)
Notes payable to affiliated companies		(297)	(516)		729
Dividends to parent					(350)
Distributions to parent			(775)		(350)
Other		(1)			(1)
Net cash provided by (used in) financing activities		666	567		(534)
Net (decrease) increase in cash and cash equivalents		(3)	8		0
Cash and cash equivalents at beginning of period		16	8		8
Cash and cash equivalents at end of period	16	13	16		8
Supplemental Disclosures [Abstract]
Cash paid for interest, net of amount capitalized		274	208		205
Cash paid for (received from) income taxes		(197)	216		(229)
Significant Non-cash Transactions [Abstract]
Accrued capital expenditures		199	170		186
Duke Energy Ohio [Member]
CASH FLOWS FROM OPERATING ACTIVITIES [Abstract]
Net Income Attributable to Parent		192	228		172
Adjustments to reconcile net income to net cash provided by operating activities: [Abstract]
Depreciation, amortization and accretion (including amortization of nuclear fuel)		265	237		230
Equity component of AFUDC		(11)	(6)		(3)
(Gains) losses on sales of other assets		(1)	(2)		(8)
Impairment charges		1			40
Deferred income taxes		90	55		206
Accrued pension and other post-retirement benefit costs		2	6		9
Contributions to qualified pension plans		(4)	(5)		(8)
Payments for asset retirement obligations		(7)	(5)		(4)
(Increase) decrease in [Abstract]
Net realized and unrealized mark-to-market and hedging transactions			(2)		(10)
Receivables		2	(4)		23
Receivables from affiliated companies		(4)	(36)		23
Inventory		6	(32)
Other current assets		(22)	79
Increase (decrease) in [Abstract]
Accounts payable		12	19		(1)
Accounts payable to affiliated companies		(1)	10		(21)
Taxes accrued		11	3		(21)
Other current liabilities		(19)	(54)		88
Other assets		(28)	(35)		25
Other liabilities		(5)	(31)		(73)
Net cash provided by (used in) operating activities		479	425		667
CASH FLOWS FROM INVESTING ACTIVITIES [Abstract]
Capital expenditures		(686)	(476)		(399)
Notes receivable from affiliated companies		80	(94)		145
Other		(41)	(30)		(15)
Net cash used in investing activities		(647)	(600)		(269)
CASH FLOWS FROM FINANCING ACTIVITIES [Abstract]
Proceeds from the issuance of long-term debt		182	341
Payments for the redemption of long-term debt		(2)	(53)		(157)
Notes payable to affiliated companies		13	(87)		(95)
Capital contribution from parent			9
Dividends to parent		(25)	(25)		(150)
Other		(1)	(2)		(2)
Net cash provided by (used in) financing activities		167	174		(404)
Net (decrease) increase in cash and cash equivalents		(1)	(1)		(6)
Cash and cash equivalents at beginning of period		13	14		20
Cash and cash equivalents at end of period	13	12	13		14
Supplemental Disclosures [Abstract]
Cash paid for interest, net of amount capitalized		85	81		76
Cash paid for (received from) income taxes		(8)	(46)		410
Significant Non-cash Transactions [Abstract]
Accrued capital expenditures		82	83		20
Distribution of membership interest of Duke Energy SAM, LLC to parent					1,912
Duke Energy Indiana [Member]
CASH FLOWS FROM OPERATING ACTIVITIES [Abstract]
Net Income Attributable to Parent		354	381		316
Adjustments to reconcile net income to net cash provided by operating activities: [Abstract]
Depreciation, amortization and accretion (including amortization of nuclear fuel)		462	499		439
Equity component of AFUDC		(28)	(16)		(11)
(Gains) losses on sales of other assets					(1)
Impairment charges		18	8		88
Deferred income taxes		152	213		262
Accrued pension and other post-retirement benefit costs		2	8		13
Contributions to qualified pension plans			(9)		(19)
Payments for asset retirement obligations		(45)	(46)		(19)
(Increase) decrease in [Abstract]
Receivables		59	(2)		(7)
Receivables from affiliated companies		(11)	(43)		44
Inventory		54	66		(21)
Other current assets		28	(67)		90
Increase (decrease) in [Abstract]
Accounts payable		(86)	8		33
Accounts payable to affiliated companies		4	(9)		25
Taxes accrued		64	(4)		35
Other current liabilities		(10)	(81)		26
Other assets		(28)	(27)		(82)
Other liabilities		(20)	(8)		(35)
Net cash provided by (used in) operating activities		969	871		1,176
CASH FLOWS FROM INVESTING ACTIVITIES [Abstract]
Capital expenditures		(840)	(755)		(690)
Purchases of available-for-sale securities		(20)	(14)		(9)
Proceeds from sales and maturities of available-for-sale securities		7	11		11
Proceeds from the sales of discontinued operations and other assets, net of cash divested					17
Notes receivable from affiliated companies		86	(3)		(83)
Other		(65)	32		(17)
Net cash used in investing activities		(832)	(729)		(771)
CASH FLOWS FROM FINANCING ACTIVITIES [Abstract]
Proceeds from the issuance of long-term debt			494
Payments for the redemption of long-term debt		(5)	(478)		(5)
Notes payable to affiliated companies		161			(71)
Dividends to parent					(326)
Distributions to parent		(300)	(149)
Other		(1)	(1)
Net cash provided by (used in) financing activities		(145)	(134)		(402)
Net (decrease) increase in cash and cash equivalents		(8)	8		3
Cash and cash equivalents at beginning of period		17	9		6
Cash and cash equivalents at end of period	17	9	17		9
Supplemental Disclosures [Abstract]
Cash paid for interest, net of amount capitalized		179	171		175
Cash paid for (received from) income taxes		117	(7)		(253)
Significant Non-cash Transactions [Abstract]
Accrued capital expenditures		125	99		$ 64
Piedmont Natural Gas [Member]
CASH FLOWS FROM OPERATING ACTIVITIES [Abstract]
Net Income Attributable to Parent	54	139		$ 193		$ 137
Adjustments to reconcile net income to net cash provided by operating activities: [Abstract]
Depreciation, amortization and accretion (including amortization of nuclear fuel)	25	151		148		140
(Gains) losses on sales of other assets				(133)
Impairment charges		7
Deferred income taxes	26	154		74		73
Equity in (earnings) losses of unconsolidated affiliates	(2)	6		(29)		(34)
Accrued pension and other post-retirement benefit costs	5	23		3		8
Contributions to qualified pension plans	(10)	(11)		(14)		(13)
Payments for asset retirement obligations	(1)			(6)		(6)
(Increase) decrease in [Abstract]
Receivables	(157)	(40)		12		3
Receivables from affiliated companies				(7)
Inventory	(11)			14		16
Other current assets	8	(20)		(98)		46
Increase (decrease) in [Abstract]
Accounts payable	35	(13)		6		(5)
Accounts payable to affiliated companies	4	5		6
Taxes accrued	(2)	(48)		38		4
Other current liabilities	2	(9)		28		(21)
Other assets	(7)	7		(107)		(5)
Other liabilities	5	(2)		180		29
Net cash provided by (used in) operating activities	(26)	349		308		372
CASH FLOWS FROM INVESTING ACTIVITIES [Abstract]
Capital expenditures	(113)	(585)		(522)		(444)
Contributions to equity method investments	(12)	(12)		(47)		(30)
Proceeds from the sales of other assets				175
Return of investment capital	1	2		18		2
Other	1	(6)		21		(5)
Net cash used in investing activities	(124)	(603)		(373)		(479)
CASH FLOWS FROM FINANCING ACTIVITIES [Abstract]
Proceeds from the issuance of long-term debt		250		295		148
Proceeds from Issuance of Common Stock				122		81
Payments for the redemption of long-term debt		(35)		(40)
Notes payable and commercial paper	185	(330)		(195)		(15)
Notes payable to affiliated companies		364
Dividends to parent	(27)
Dividends paid				(114)		(103)
Other		(1)
Net cash provided by (used in) financing activities	158	248		68		111
Net (decrease) increase in cash and cash equivalents	8	(6)		3		4
Cash and cash equivalents at beginning of period	17	25		14		10
Cash and cash equivalents at end of period	25	19	$ 25	17		14
Supplemental Disclosures [Abstract]
Cash paid for interest, net of amount capitalized	11	78		81		72
Cash paid for (received from) income taxes		(12)		(25)		3
Significant Non-cash Transactions [Abstract]
Accrued capital expenditures	$ 48	34		$ 63		$ 59
Transfer of ownership interest of certain equity method investees to parent		$ 149

Consolidated Statements of Equi

Consolidated Statements of Equity - USD ($) $ in Millions	Total	Common Stock [Member]	Additional Paid In Capital [Member]	Retained Earnings [Member]		Foreign Currency Translation Adjustments [Member]		Net Gains (Losses) on Cash Flow Hedges [Member]	Net Unrealized Gains (Losses) on Available-for-Sale Securities [Member]	Pension And OPEB Adjustments [Member]	Common Stockholders' Equity [Member]	Noncontrolling Interest [Member]		Duke Energy Carolinas [Member]	Duke Energy Carolinas [Member]Members Equity [Member]	Duke Energy Carolinas [Member]Net Gains (Losses) on Cash Flow Hedges [Member]	Duke Energy Carolinas [Member]Net Unrealized Gains (Losses) on Available-for-Sale Securities [Member]	Progress Energy [Member]	Progress Energy [Member]Additional Paid In Capital [Member]	Progress Energy [Member]Retained Earnings [Member]		Progress Energy [Member]Net Gains (Losses) on Cash Flow Hedges [Member]	Progress Energy [Member]Net Unrealized Gains (Losses) on Available-for-Sale Securities [Member]	Progress Energy [Member]Pension And OPEB Adjustments [Member]	Progress Energy [Member]Common Stockholders' Equity [Member]	Progress Energy [Member]Noncontrolling Interest [Member]	Duke Energy Progress [Member]	Duke Energy Progress [Member]Common Stock [Member]	Duke Energy Progress [Member]Retained Earnings [Member]	Duke Energy Progress [Member]Members Equity [Member]	Duke Energy Florida [Member]	Duke Energy Florida [Member]Common Stock [Member]	Duke Energy Florida [Member]Retained Earnings [Member]	Duke Energy Florida [Member]Members Equity [Member]	Duke Energy Florida [Member]Net Unrealized Gains (Losses) on Available-for-Sale Securities [Member]	Duke Energy Ohio [Member]	Duke Energy Ohio [Member]Common Stock [Member]	Duke Energy Ohio [Member]Additional Paid In Capital [Member]	Duke Energy Ohio [Member]Retained Earnings [Member]	Duke Energy Indiana [Member]	Duke Energy Indiana [Member]Common Stock [Member]	Duke Energy Indiana [Member]Additional Paid In Capital [Member]	Duke Energy Indiana [Member]Retained Earnings [Member]	Duke Energy Indiana [Member]Members Equity [Member]	Duke Energy Indiana [Member]Net Gains (Losses) on Cash Flow Hedges [Member]	Piedmont Natural Gas [Member]	Piedmont Natural Gas [Member]Common Stock [Member]	Piedmont Natural Gas [Member]Retained Earnings [Member]	Piedmont Natural Gas [Member]Net Gains (Losses) on Cash Flow Hedges [Member]
Beginning Balance (Attributable to Parent) at Oct. 31, 2014																																														$ 1,309	$ 637	$ 672
Net Income Attributable to Parent																																														137		137
Other comprehensive income (loss), net of tax																																														(1)			$ (1)
Common stock issuances, including dividend reinvestment and employee benefits																																														85	85
Expenses from issuance of common stock																																														(1)	(1)
Common stock dividends																																														(103)		(103)
Ending Balance (Attributable to Parent) at Oct. 31, 2015																																														1,426	721	706	(1)
Beginning Balance (parent) at Dec. 31, 2014	$ 40,899	$ 1	$ 39,405	$ 2,012		$ (439)		$ (59)	$ 3	$ (48)	$ 40,875	$ 24						$ 11,176	$ 7,467	$ 3,782		$ (35)	$ 1	$ (7)	$ 11,208	$ (32)
Beginning Members' Equity at Dec. 31, 2014														$ 10,924	$ 10,937	$ (12)	$ (1)
Beginning Balance (Attributable to Parent) at Dec. 31, 2014																											$ 5,867	$ 2,159	$ 3,708		$ 5,222	$ 1,762	$ 3,460			$ 4,674	$ 762	$ 4,782	$ (870)	$ 3,848	$ 1	$ 1,384	$ 2,460		$ 3
Balance (in shares) at Dec. 31, 2014		707,000,000
Net income	2,831			2,816							2,816	15						1,062		1,051					1,051	11
Net Income Attributable to Parent	2,816													1,081	1,081			1,051									566		355	$ 211	599		351	$ 248		172			172	316			316
Other comprehensive income (loss), net of tax	(274)					(253)		9	(6)	(13)	(263)	(11)		2		1	$ 1	(7)				4	(1)	(10)	(7)															(2)					(2)
Common stock issuances, including dividend reinvestment and employee benefits (in shares)		1,000,000
Common stock issuances, including dividend reinvestment and employee benefits	$ 63		63								63
Stock repurchase, shares	(19,800,000)	(20,000,000)
Stock repurchase	$ (1,500)		(1,500)								(1,500)
Common stock dividends	(2,254)			(2,254)							(2,254)																				(350)		(350)
Distributions/Dividends to parent														(401)	(401)																(350)			(350)		(150)		(150)		(326)			(326)
Distributions to noncontrolling interest in subsidiaries	(9)											(9)						(4)								(4)
Capital contribution from parent																		625	625						625		626			626
Distribution of membership interest of Duke Energy SAM, LLC to parent																																				(1,912)		(1,912)
Other	15			(10)							(10)	25	[1]					1		(2)					(2)	3		$ (2,159)	$ (4,063)	6,222		$ (1,762)	$ (3,461)	5,223
Balance (in shares) at Dec. 31, 2015		688,000,000
Ending Balance (parent) at Dec. 31, 2015	39,771	$ 1	37,968	2,564		(692)		(50)	(3)	(61)	39,727	44						12,853	8,092	4,831		(31)		(17)	12,875	(22)
Ending member's equity at Dec. 31, 2015														11,606	11,617	(11)											7,059			7,059	5,121			5,121
Ending Balance (Attributable to Parent) at Dec. 31, 2015																																				2,784	762	2,720	(698)	3,836	1	1,384	2,450		1
Beginning Balance (Attributable to Parent) at Oct. 31, 2015																																														1,426	721	706	(1)
Net Income Attributable to Parent																																														193		193
Other comprehensive income (loss), net of tax																																														1			$ 1
Common stock issuances, including dividend reinvestment and employee benefits																																														139	139
Common stock dividends																																														(114)		(114)
Ending Balance (Attributable to Parent) at Oct. 31, 2016																																														$ 1,645	860	785
Beginning Balance (Attributable to Parent) at Dec. 31, 2015																																				2,784	762	2,720	(698)	3,836	1	1,384	2,450		1
Net income	2,170			2,152							2,152	18						1,041		1,031					1,031	10
Net Income Attributable to Parent	2,152													1,166	1,166			1,031									599			599	551			551		228			228	381				$ 381
Other comprehensive income (loss), net of tax	715					$ 692	[2]	30	2	(11)	713	2		2		2		10				8	1	1	10						1				$ 1					(1)					$ (1)
Common stock issuances, including dividend reinvestment and employee benefits (in shares)		12,000,000
Common stock issuances, including dividend reinvestment and employee benefits	773		773								773
Common stock dividends	(2,332)			(2,332)							(2,332)
Distributions/Dividends to parent														(2,000)	(2,000)			(2,098)		(2,098)					(2,098)		(300)			(300)	(775)			(775)		(25)		(25)		(149)				(149)
Distributions to noncontrolling interest in subsidiaries	(6)											(6)						(1)								(1)
Capital contribution from parent																																				$ 9			9
Other	$ (50)											(50)	[3]	(2)	(2)			$ 2	2						2						2			2							$ (1)	$ (1,384)	$ (2,450)	3,835
Balance (in shares) at Dec. 31, 2016	700,000,000	700,000,000																100																		90,000,000										100
Ending Balance (parent) at Dec. 31, 2016	$ 41,041	$ 1	38,741	2,384				(20)	(1)	(72)	41,033	8						$ 11,807	8,094	3,764		(23)	1	(16)	11,820	(13)
Ending member's equity at Dec. 31, 2016														10,772	10,781	(9)											7,358			7,358	4,900			4,899	1					4,067				4,067
Ending Balance (Attributable to Parent) at Dec. 31, 2016	$ 41,033																	$ 11,820																		$ 2,996	762	2,695	(461)							$ 1,672	860	812
Beginning Balance (Attributable to Parent) at Oct. 31, 2016																																														1,645	860	785
Net Income Attributable to Parent																																														54		54
Distributions/Dividends to parent																																														$ (27)		(27)
Balance (in shares) at Dec. 31, 2016	700,000,000	700,000,000																100																		90,000,000										100
Ending Balance (parent) at Dec. 31, 2016	$ 41,041	$ 1	38,741	2,384				(20)	(1)	(72)	41,033	8						$ 11,807	8,094	3,764		(23)	1	(16)	11,820	(13)
Ending member's equity at Dec. 31, 2016														10,772	10,781	(9)											7,358			7,358	4,900			4,899	1					4,067				4,067
Ending Balance (Attributable to Parent) at Dec. 31, 2016	41,033																	11,820																		$ 2,996	762	2,695	(461)							$ 1,672	860	812
Net income	3,064			3,059							3,059	5						1,268		1,258					1,258	10
Net Income Attributable to Parent	3,059													1,214	1,214			1,258									715			715	712			712		192			192	354				354		139
Other comprehensive income (loss), net of tax	26							10	13	3	26			2		2		13				5	4	4	13						3				3
Common stock issuances, including dividend reinvestment and employee benefits	51		51								51
Common stock dividends	(2,450)			(2,450)							(2,450)
Distributions/Dividends to parent														(625)	(625)			(672)		(672)	[4]				(672)		(124)			(124)						$ (25)		(25)		(300)				(300)
Distributions to noncontrolling interest in subsidiaries	(2)											(2)
Equitization of certain notes payable to affiliates																		1,047	1,047						1,047
Other	$ 7			20	[5]						20	(13)	[5]	(2)	(2)			$ 2	2						2						3			3												$ (149)		(149)
Balance (in shares) at Dec. 31, 2017	700,000,000	700,000,000																100																		90,000,000										100
Ending Balance (parent) at Dec. 31, 2017	$ 41,737	$ 1	$ 38,792	$ 3,013				$ (10)	$ 12	$ (69)	$ 41,739	$ (2)						$ 13,465	$ 9,143	$ 4,350		$ (18)	$ 5	$ (12)	$ 13,468	$ (3)
Ending member's equity at Dec. 31, 2017														$ 11,361	$ 11,368	$ (7)											$ 7,949			$ 7,949	$ 5,618			$ 5,614	$ 4					$ 4,121				$ 4,121
Ending Balance (Attributable to Parent) at Dec. 31, 2017	$ 41,739																	$ 13,468																		$ 3,163	$ 762	$ 2,670	$ (269)							$ 1,662	$ 860	$ 802
[1]	Noncontrolling Interests amount is primarily related to the acquisitions of a majority interest in a provider of energy management systems and services for commercial customers and a solar company.
[2]	Foreign Currency Translation Adjustments amount includes $620 million of cumulative adjustment realized as a result of the sale of the Latin American generation business. See Note 2 to the Consolidated Financial Statements.
[3]	Noncontrolling Interests amount is primarily related to the sale of the Latin American generation business. See Note 2 to the Consolidated Financial Statements.
[4]	Includes a $547 million non-cash dividend related to a legal entity restructuring.
[5]	Retained Earnings relates to a cumulative-effect adjustment due to implementation of a new accounting standard related to stock-based compensation and the associated income taxes. See Note 1 to the Consolidated Financial Statements for additional information. Noncontrolling Interests relates to the purchase of remaining interest in REC Solar.

Consolidated Statements of Equ9

Consolidated Statements of Equity (Parenthetical) (Parentheticals) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Progress Energy [Member]
Non-cash dividend	$ 547
International Energy [Member]
Disposal Group, Including Discontinued Operation, Foreign Currency Translation Gains (Losses)		$ 620

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Index to Combined Notes To Consolidated Financial Statements The notes to the consolidated financial statements are a combined presentation. The following table indicates the registrants to which the notes apply. Applicable Notes Registrant 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Duke Energy Corporation • • • • • • • • • • • • • • • • • • • • • • • • Duke Energy Carolinas, LLC • • • • • • • • • • • • • • • • • • • • • Progress Energy, Inc. • • • • • • • • • • • • • • • • • • • • • Duke Energy Progress, LLC • • • • • • • • • • • • • • • • • • • • Duke Energy Florida, LLC • • • • • • • • • • • • • • • • • • • • Duke Energy Ohio, Inc. • • • • • • • • • • • • • • • • • • • • • Duke Energy Indiana, LLC • • • • • • • • • • • • • • • • • • • • • Piedmont Natural Gas Company, Inc. • • • • • • • • • • • • • • • • • • • • • • Tables within the notes may not sum across due to (i) Progress Energy's consolidation of Duke Energy Progress, Duke Energy Florida and other subsidiaries that are not registrants and (ii) subsidiaries that are not registrants but included in the consolidated Duke Energy balances. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Nature of Operations and Basis of Consolidation Duke Energy Corporation (collectively with its subsidiaries, Duke Energy) is an energy company headquartered in Charlotte, North Carolina, subject to regulation by the Federal Energy Regulatory Commission (FERC). Duke Energy operates in the United States (U.S.) primarily through its direct and indirect subsidiaries. Certain Duke Energy subsidiaries are also subsidiary registrants, including Duke Energy Carolinas, LLC (Duke Energy Carolinas); Progress Energy, Inc. (Progress Energy); Duke Energy Progress, LLC (Duke Energy Progress); Duke Energy Florida, LLC (Duke Energy Florida); Duke Energy Ohio, Inc. (Duke Energy Ohio); Duke Energy Indiana, LLC (Duke Energy Indiana) and Piedmont Natural Gas Company, Inc. (Piedmont). When discussing Duke Energy’s consolidated financial information, it necessarily includes the results of its seven separate subsidiary registrants (collectively referred to as the Subsidiary Registrants), which along with Duke Energy, are collectively referred to as the Duke Energy Registrants. In October 2016, Duke Energy completed the acquisition of Piedmont. Duke Energy's consolidated financial statements include Piedmont's results of operations and cash flows activity subsequent to the acquisition date. Effective November 1, 2016, Piedmont's fiscal year-end was changed from October 31 to December 31, the year-end of Duke Energy. A transition report was filed on Form 10-Q (Form 10-QT) as of December 31, 2016, for the transition period from November 1, 2016, to December 31, 2016. See Note 2 for additional information regarding the acquisition. In December 2016, Duke Energy completed an exit of the Latin American market to focus on its domestic regulated business, which was further bolstered by the acquisition of Piedmont. The sale of the International Energy business segment, excluding an equity method investment in National Methanol Company (NMC), was completed through two transactions including a sale of assets in Brazil to China Three Gorges (Luxembourg) Energy S.à.r.l. (CTG) and a sale of Duke Energy's remaining Latin American assets in Peru, Chile, Ecuador, Guatemala, El Salvador and Argentina to ISQ Enerlam Aggregator, L.P. and Enerlam (UK) Holding Ltd. (I Squared) (collectively, the International Disposal Group). See Note 2 for additional information on the sale of International Energy. The information in these combined notes relates to each of the Duke Energy Registrants as noted in the Index to Combined Notes to Consolidated Financial Statements. However, none of the Subsidiary Registrants make any representation as to information related solely to Duke Energy or the Subsidiary Registrants of Duke Energy other than itself. These Consolidated Financial Statements include, after eliminating intercompany transactions and balances, the accounts of the Duke Energy Registrants and subsidiaries where the respective Duke Energy Registrants have control. These Consolidated Financial Statements also reflect the Duke Energy Registrants’ proportionate share of certain jointly owned generation and transmission facilities. Substantially all of the Subsidiary Registrants' operations qualify for regulatory accounting. Duke Energy Carolinas is a regulated public utility primarily engaged in the generation, transmission, distribution and sale of electricity in portions of North Carolina and South Carolina. Duke Energy Carolinas is subject to the regulatory provisions of the North Carolina Utilities Commission (NCUC), Public Service Commission of South Carolina (PSCSC), U.S. Nuclear Regulatory Commission (NRC) and FERC. Progress Energy is a public utility holding company headquartered in Raleigh, North Carolina, subject to regulation by FERC. Progress Energy conducts operations through its wholly owned subsidiaries, Duke Energy Progress and Duke Energy Florida. Duke Energy Progress is a regulated public utility primarily engaged in the generation, transmission, distribution and sale of electricity in portions of North Carolina and South Carolina. Duke Energy Progress is subject to the regulatory provisions of the NCUC, PSCSC, NRC and FERC. Duke Energy Florida is a regulated public utility primarily engaged in the generation, transmission, distribution and sale of electricity in portions of Florida. Duke Energy Florida is subject to the regulatory provisions of the Florida Public Service Commission (FPSC), NRC and FERC. Duke Energy Ohio is a regulated public utility primarily engaged in the transmission and distribution of electricity in portions of Ohio and Kentucky, the generation and sale of electricity in portions of Kentucky and the transportation and sale of natural gas in portions of Ohio and Kentucky. Duke Energy Ohio conducts competitive auctions for retail electricity supply in Ohio whereby the energy price is recovered from retail customers and recorded in Operating Revenues on the Consolidated Statements of Operations and Comprehensive Income. Operations in Kentucky are conducted through its wholly owned subsidiary, Duke Energy Kentucky, Inc. (Duke Energy Kentucky). References herein to Duke Energy Ohio collectively include Duke Energy Ohio and its subsidiaries, unless otherwise noted. Duke Energy Ohio is subject to the regulatory provisions of the Public Utilities Commission of Ohio (PUCO), Kentucky Public Service Commission (KPSC) and FERC. On April 2, 2015, Duke Energy completed the sale of its nonregulated Midwest generation business, which sold power into wholesale energy markets, to a subsidiary of Dynegy Inc. (Dynegy). For further information about the sale of the Midwest Generation business, refer to Note 2 . Substantially all of Duke Energy Ohio's operations that remain after the sale qualify for regulatory accounting. Duke Energy Indiana is a regulated public utility primarily engaged in the generation, transmission, distribution and sale of electricity in portions of Indiana. Duke Energy Indiana is subject to the regulatory provisions of the Indiana Utility Regulatory Commission (IURC) and FERC. Piedmont is a regulated public utility primarily engaged in the distribution of natural gas in portions of North Carolina, South Carolina and Tennessee. Piedmont is subject to the regulatory provisions of the NCUC, PSCSC, Tennessee Public Utility Commission (TPUC) and FERC. Certain prior year amounts have been reclassified to conform to the current year presentation. Other Current Assets and Liabilities The following table provides a description of amounts included in Other within Current Assets or Current Liabilities that exceed 5 percent of total Current Assets or Current Liabilities on the Duke Energy Registrants' Consolidated Balance Sheets at either December 31, 2017 , or 2016 . December 31, (in millions) Location 2017 2016 Duke Energy Accrued compensation Current Liabilities $ 757 $ 765 Duke Energy Carolinas Accrued compensation Current Liabilities $ 252 $ 248 Customer deposits Current Liabilities 121 155 Progress Energy Income taxes receivable Current Assets $ 278 $ 19 Customer deposits Current Liabilities 338 363 Duke Energy Progress Customer deposits Current Liabilities $ 129 $ 141 Accrued compensation Current Liabilities 132 135 Duke Energy Florida Customer deposits Current Liabilities $ 208 $ 222 Duke Energy Ohio Income taxes receivable Current Assets $ 36 $ 16 Customer deposits Current Liabilities 46 62 Duke Energy Indiana Customer deposits Current Liabilities $ 45 $ 44 Piedmont Income taxes receivable Current Assets $ 43 $ 9 Discontinued Operations The results of operations of the International Disposal Group as well as Duke Energy Ohio's nonregulated Midwest Generation business and Duke Energy Retail Sales, LLC (collectively, Midwest Generation Disposal Group) have been classified as Discontinued Operations on Duke Energy's Consolidated Statements of Operations. Duke Energy has elected to present cash flows of discontinued operations combined with cash flows of continuing operations. Unless otherwise noted, the notes to these consolidated financial statements exclude amounts related to discontinued operations for all periods presented. See Note 2 for additional information. Amounts Attributable to Controlling Interests For the year ended December 31, 2017, the Loss From Discontinued Operations, net of tax on Duke Energy's Consolidated Statement of Operations is entirely attributable to controlling interest. The following table presents Net Income Attributable to Duke Energy Corporation for continuing operations and discontinued operations for the years ended December 31, 2016, and 2015. Year ended December 31, (in millions) 2016 2015 Income from Continuing Operations $ 2,578 $ 2,654 Income from Continuing Operations Attributable to Noncontrolling Interests 7 9 Income from Continuing Operations Attributable to Duke Energy Corporation $ 2,571 $ 2,645 (Loss) Income From Discontinued Operations, net of tax $ (408 ) $ 177 Income from Discontinued Operations Attributable to Noncontrolling Interests, net of tax 11 6 (Loss) Income From Discontinued Operations Attributable to Duke Energy Corporation, net of tax $ (419 ) $ 171 Net Income $ 2,170 $ 2,831 Net Income Attributable to Noncontrolling Interests 18 15 Net Income Attributable to Duke Energy Corporation $ 2,152 $ 2,816 Significant Accounting Policies Use of Estimates In preparing financial statements that conform to generally accepted accounting principles (GAAP) in the U.S., the Duke Energy Registrants must make estimates and assumptions that affect the reported amounts of assets and liabilities, the reported amounts of revenues and expenses and the disclosure of contingent assets and liabilities at the date of the financial statements. Actual results could differ from those estimates. Regulatory Accounting The majority of the Duke Energy Registrants’ operations are subject to price regulation for the sale of electricity and natural gas by state utility commissions or FERC. When prices are set on the basis of specific costs of the regulated operations and an effective franchise is in place such that sufficient natural gas or electric services can be sold to recover those costs, the Duke Energy Registrants apply regulatory accounting. Regulatory accounting changes the timing of the recognition of costs or revenues relative to a company that does not apply regulatory accounting. As a result, regulatory assets and regulatory liabilities are recognized on the Consolidated Balance Sheets. Regulatory assets and liabilities are amortized consistent with the treatment of the related cost in the ratemaking process. See Note 4 for further information. Regulatory accounting rules also require recognition of a disallowance (also called "impairment") loss if it becomes probable that part of the cost of a plant under construction (or a recently completed plant or an abandoned plant) will be disallowed for ratemaking purposes and a reasonable estimate of the amount of the disallowance can be made. These disallowances can require judgments on allowed future rate recovery. When it becomes probable that regulated generation, transmission or distribution assets will be abandoned, the cost of the asset is removed from plant in service. The value that may be retained as a regulatory asset on the balance sheet for the abandoned property is dependent upon amounts that may be recovered through regulated rates, including any return. As such, an impairment charge could be partially or fully offset by the establishment of a regulatory asset if rate recovery is probable. The impairment for a disallowance of costs for regulated plants under construction, recently completed or abandoned is based on discounted cash flows. Regulated Fuel and Purchased Gas Adjustment Clauses The Duke Energy Registrants utilize cost-tracking mechanisms, commonly referred to as fuel adjustment clauses or purchased gas adjustment clauses (PGA). These clauses allow for the recovery of fuel and fuel-related costs, portions of purchased power, natural gas costs and hedging costs through surcharges on customer rates. The difference between the costs incurred and the surcharge revenues is recorded either as an adjustment to Operating Revenues, Operating Expenses – Fuel used in electric generation or Operating Expenses – Cost of natural gas on the Consolidated Statements of Operations, with an off-setting impact on regulatory assets or liabilities. Cash and Cash Equivalents All highly liquid investments with maturities of three months or less at the date of acquisition are considered cash equivalents. Restricted Cash The Duke Energy Registrants have restricted cash related primarily to collateral assets, escrow deposits and variable interest entities (VIEs). Restricted cash balances are reflected in Other within Current Assets and in Other within Other Noncurrent Assets on the Consolidated Balance Sheets. At December 31, 2017 , and 2016 , Duke Energy had restricted cash totaling $147 million and $137 million , respectively. Inventory Inventory is used for operations and is recorded primarily using the average cost method. Inventory related to regulated operations is valued at historical cost. Inventory related to nonregulated operations is valued at the lower of cost or market. Materials and supplies are recorded as inventory when purchased and subsequently charged to expense or capitalized to property, plant and equipment when installed. Inventory, including excess or obsolete inventory, is written-down to the lower of cost or market value. Once inventory has been written-down, it creates a new cost basis for the inventory that is not subsequently written-up. Provisions for inventory write-offs were not material at December 31, 2017 , and 2016 . The components of inventory are presented in the tables below. December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Materials and supplies $ 2,293 $ 744 $ 1,118 $ 774 $ 343 $ 82 $ 309 $ 2 Coal 603 192 255 139 116 17 139 — Natural gas, oil and other 354 35 219 104 115 34 2 64 Total inventory $ 3,250 $ 971 $ 1,592 $ 1,017 $ 574 $ 133 $ 450 $ 66 December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Materials and supplies $ 2,374 $ 767 $ 1,167 $ 813 $ 354 $ 84 $ 312 $ 1 Coal 774 251 314 148 166 19 190 — Natural gas, oil and other 374 37 236 115 121 34 2 65 Total inventory $ 3,522 $ 1,055 $ 1,717 $ 1,076 $ 641 $ 137 $ 504 $ 66 Investments in Debt and Equity Securities The Duke Energy Registrants classify investments into two categories – trading and available-for-sale. Both categories are recorded at fair value on the Consolidated Balance Sheets. Realized and unrealized gains and losses on trading securities are included in earnings. For certain investments of regulated operations, such as substantially all of the Nuclear Decommissioning Trust Funds (NDTF), realized and unrealized gains and losses (including any other-than-temporary impairments (OTTIs)) on available-for-sale securities are recorded as a regulatory asset or liability. Otherwise, unrealized gains and losses are included in Accumulated Other Comprehensive Income (AOCI), unless other-than-temporarily impaired. OTTIs for equity securities and the credit loss portion of debt securities of nonregulated operations are included in earnings. Investments in debt and equity securities are classified as either current or noncurrent based on management’s intent and ability to sell these securities, taking into consideration current market liquidity. See Note 15 for further information. Goodwill and Intangible Assets Goodwill Effective with Piedmont's change in fiscal year end to December 31, as discussed above, Piedmont changed the date of its annual impairment testing of goodwill from October 31 to August 31 to align with the other Duke Energy Registrants. Duke Energy, Progress Energy, Duke Energy Ohio and Piedmont perform annual goodwill impairment tests as of August 31 each year at the reporting unit level, which is determined to be an operating segment or one level below. Duke Energy, Progress Energy, Duke Energy Ohio and Piedmont update these tests between annual tests if events or circumstances occur that would more likely than not reduce the fair value of a reporting unit below its carrying value. Intangible Assets Intangible assets are included in Other in Other Noncurrent Assets on the Consolidated Balance Sheets. Generally, intangible assets are amortized using an amortization method that reflects the pattern in which the economic benefits of the intangible asset are consumed or on a straight-line basis if that pattern is not readily determinable. Amortization of intangibles is reflected in Depreciation and amortization on the Consolidated Statements of Operations. Intangible assets are subject to impairment testing and if impaired, the carrying value is accordingly reduced. Emission allowances permit the holder of the allowance to emit certain gaseous byproducts of fossil fuel combustion, including sulfur dioxide (SO 2 ) and nitrogen oxide (NO X ). Allowances are issued by the U.S. Environmental Protection Agency (EPA) at zero cost and may also be bought and sold via third-party transactions. Allowances allocated to or acquired by the Duke Energy Registrants are held primarily for consumption. Carrying amounts for emission allowances are based on the cost to acquire the allowances or, in the case of a business combination, on the fair value assigned in the allocation of the purchase price of the acquired business. Emission allowances are expensed to Fuel used in electric generation and purchased power on the Consolidated Statements of Operations. Renewable energy certificates are used to measure compliance with renewable energy standards and are held primarily for consumption. See Note 11 for further information. Long-Lived Asset Impairments The Duke Energy Registrants evaluate long-lived assets, excluding goodwill, for impairment when circumstances indicate the carrying value of those assets may not be recoverable. An impairment exists when a long-lived asset’s carrying value exceeds the estimated undiscounted cash flows expected to result from the use and eventual disposition of the asset. The estimated cash flows may be based on alternative expected outcomes that are probability weighted. If the carrying value of the long-lived asset is not recoverable based on these estimated future undiscounted cash flows, the carrying value of the asset is written-down to its then-current estimated fair value and an impairment charge is recognized. The Duke Energy Registrants assess fair value of long-lived assets using various methods, including recent comparable third-party sales, internally developed discounted cash flow analysis and analysis from outside advisors. Triggering events to reassess cash flows may include, but are not limited to, significant changes in commodity prices, the condition of an asset or management’s interest in selling the asset. Property, Plant and Equipment Property, plant and equipment are stated at the lower of depreciated historical cost net of any disallowances or fair value, if impaired. The Duke Energy Registrants capitalize all construction-related direct labor and material costs, as well as indirect construction costs such as general engineering, taxes and financing costs. See “Allowance for Funds Used During Construction (AFUDC) and Interest Capitalized” for information on capitalized financing costs. Costs of renewals and betterments that extend the useful life of property, plant and equipment are also capitalized. The cost of repairs, replacements and major maintenance projects, which do not extend the useful life or increase the expected output of the asset, are expensed as incurred. Depreciation is generally computed over the estimated useful life of the asset using the composite straight-line method. Depreciation studies are conducted periodically to update composite rates and are approved by state utility commissions and/or the FERC when required. The composite weighted average depreciation rates, excluding nuclear fuel, are included in the table that follows. Years Ended December 31, 2017 2016 2015 Duke Energy 2.8 % 2.8 % 2.9 % Duke Energy Carolinas 2.8 % 2.8 % 2.8 % Progress Energy 2.6 % 2.7 % 2.6 % Duke Energy Progress 2.6 % 2.6 % 2.6 % Duke Energy Florida 2.8 % 2.8 % 2.7 % Duke Energy Ohio 2.8 % 2.6 % 2.7 % Duke Energy Indiana 3.0 % 3.1 % 3.0 % Piedmont (a) 2.3 % (a) Piedmont's weighted average depreciation rate was 2.4 percent , 2.4 percent , and 2.5 percent for the annualized two months ended December 31, 2016 and for the years ended October 31, 2016 and 2015, respectively. In general, when the Duke Energy Registrants retire regulated property, plant and equipment, the original cost plus the cost of retirement, less salvage value, is charged to accumulated depreciation. However, when it becomes probable the asset will be retired substantially in advance of its original expected useful life or is abandoned, the cost of the asset and the corresponding accumulated depreciation is recognized as a separate asset. If the asset is still in operation, the net amount is classified as Generation facilities to be retired, net on the Consolidated Balance Sheets. If the asset is no longer operating, the net amount is classified in Regulatory assets on the Consolidated Balance Sheets if deemed recoverable (see discussion of long-lived asset impairments above). When it becomes probable an asset will be abandoned, the cost of the asset and accumulated depreciation is reclassified to Regulatory assets on the Consolidated Balance Sheets for amounts recoverable in rates. The carrying value of the asset is based on historical cost if the Duke Energy Registrants are allowed to recover the remaining net book value and a return equal to at least the incremental borrowing rate. If not, an impairment is recognized to the extent the net book value of the asset exceeds the present value of future revenues discounted at the incremental borrowing rate. When the Duke Energy Registrants sell entire regulated operating units, or retire or sell nonregulated properties, the original cost and accumulated depreciation and amortization balances are removed from Property, Plant and Equipment on the Consolidated Balance Sheets. Any gain or loss is recorded in earnings, unless otherwise required by the applicable regulatory body. See Note 10 for further information. Nuclear Fuel Nuclear fuel is classified as Property, Plant and Equipment on the Consolidated Balance Sheets, except for Duke Energy Florida. Nuclear fuel amounts at Duke Energy Florida were reclassified to Regulatory assets pursuant to the Revised and Restated Stipulation and Settlement Agreement approved in November 2013 among Duke Energy Florida, the Florida Office of Public Counsel (Florida OPC) and other customer advocates (the 2013 Settlement). Nuclear fuel in the front-end fuel processing phase is considered work in progress and not amortized until placed in service. Amortization of nuclear fuel is included within Fuel used in electric generation and purchased power on the Consolidated Statements of Operations. Amortization is recorded using the units-of-production method. Allowance for Funds Used During Construction and Interest Capitalized For regulated operations, the debt and equity costs of financing the construction of property, plant and equipment are reflected as AFUDC and capitalized as a component of the cost of property, plant and equipment. AFUDC equity is reported on the Consolidated Statements of Operations as non-cash income in Other income and expenses, net. AFUDC debt is reported as a non-cash offset to Interest Expense. After construction is completed, the Duke Energy Registrants are permitted to recover these costs through their inclusion in rate base and the corresponding subsequent depreciation or amortization of those regulated assets. AFUDC equity, a permanent difference for income taxes, reduces the effective tax rate (ETR) when capitalized and increases the ETR when depreciated or amortized. See Note 22 for additional information. For nonregulated operations, interest is capitalized during the construction phase with an offsetting non-cash credit to Interest Expense on the Consolidated Statements of Operations. Asset Retirement Obligations Asset retirement obligations (AROs) are recognized for legal obligations associated with the retirement of property, plant and equipment. Substantially all AROs are related to regulated operations. When recording an ARO, the present value of the projected liability is recognized in the period in which it is incurred, if a reasonable estimate of fair value can be made. The liability is accreted over time. For operating plants, the present value of the liability is added to the cost of the associated asset and depreciated over the remaining life of the asset. For retired plants, the present value of the liability is recorded as a regulatory asset unless determined not to be recoverable. The present value of the initial obligation and subsequent updates are based on discounted cash flows, which include estimates regarding timing of future cash flows, selection of discount rates and cost escalation rates, among other factors. These estimates are subject to change. Depreciation expense is adjusted prospectively for any changes to the carrying amount of the associated asset. The Duke Energy Registrants receive amounts to fund the cost of the ARO for regulated operations through a combination of regulated revenues and earnings on the NDTF. As a result, amounts recovered in regulated revenues, earnings on the NDTF, accretion expense and depreciation of the associated asset are netted and deferred as a regulatory asset or liability. Obligations for nuclear decommissioning are based on site-specific cost studies. Duke Energy Carolinas and Duke Energy Progress assume prompt dismantlement of the nuclear facilities after operations are ceased. Duke Energy Florida assumes Crystal River Unit 3 Nuclear Plant (Crystal River Unit 3) will be placed into a safe storage configuration until eventual dismantlement is completed by 2074. Duke Energy Carolinas, Duke Energy Progress and Duke Energy Florida also assume that spent fuel will be stored on-site until such time that it can be transferred to a yet to be built U.S. Department of Energy (DOE) facility. Obligations for closure of ash basins are based upon discounted cash flows of estimated costs for site-specific plans, if known, or probability weightings of the potential closure methods if the closure plans are under development and multiple closure options are being considered and evaluated on a site-by-site basis. See Note 9 for additional information. Revenue Recognition and Unbilled Revenue Revenues on sales of electricity and natural gas are recognized when service is provided or the product is delivered. Unbilled revenues are recognized by applying customer billing rates to the estimated volumes of energy or natural gas delivered but not yet billed. Unbilled revenues can vary significantly from period to period as a result of seasonality, weather, customer usage patterns, customer mix, average price in effect for customer classes, timing of rendering customer bills and meter reading schedules, and the impact of weather normalization or margin decoupling mechanisms. Unbilled revenues are included within Receivables and Receivables of VIEs on the Consolidated Balance Sheets as shown in the following table. December 31, (in millions) 2017 2016 Duke Energy $ 944 $ 831 Duke Energy Carolinas 342 313 Progress Energy 228 161 Duke Energy Progress 143 102 Duke Energy Florida 85 59 Duke Energy Ohio 4 2 Duke Energy Indiana 21 32 Piedmont 86 77 Additionally, Duke Energy Ohio and Duke Energy Indiana sell, on a revolving basis, nearly all of their retail accounts receivable, including receivables for unbilled revenues, to an affiliate, Cinergy Receivables Company LLC (CRC) and account for the transfers of receivables as sales. Accordingly, the receivables sold are not reflected on the Consolidated Balance Sheets of Duke Energy Ohio and Duke Energy Indiana. See Note 17 for further information. These receivables for unbilled revenues are shown in the table below. December 31, (in millions) 2017 2016 Duke Energy Ohio $ 104 $ 97 Duke Energy Indiana 132 123 Allowance for Doubtful Accounts Allowances for doubtful accounts are presented in the following table. December 31, (in millions) 2017 2016 2015 Allowance for Doubtful Accounts Duke Energy $ 14 $ 14 $ 12 Duke Energy Carolinas 2 2 3 Progress Energy 4 6 6 Duke Energy Progress 1 4 4 Duke Energy Florida 3 2 2 Duke Energy Ohio 3 2 2 Duke Energy Indiana 2 1 1 Piedmont (a) 2 3 Allowance for Doubtful Accounts – VIEs Duke Energy $ 54 $ 54 $ 53 Duke Energy Carolinas 7 7 7 Progress Energy 7 7 8 Duke Energy Progress 5 5 5 Duke Energy Florida 2 2 3 (a) Piedmont's allowance for doubtful accounts was $2 million as of October 31, 2016, and 2015. Derivatives and Hedging Derivative and non-derivative instruments may be used in connection with commodity price and interest rate activities, including swaps, futures, forwards and options. All derivative instruments, except those that qualify for the normal purchase/normal sale (NPNS) exception, are recorded on the Consolidated Balance Sheets at fair value. Qualifying derivative instruments may be designated as either cash flow hedges or fair value hedges. Other derivative instruments (undesignated contracts) either have not been designated or do not qualify as hedges. The effective portion of the change in the fair value of cash flow hedges is recorded in AOCI. The effective portion of the change in the fair value of a fair value hedge is offset in net income by changes in the hedged item. For activity subject to regulatory accounting, gains and losses on derivative contracts are reflected as regulatory assets or liabilities and not as other comprehensive income or current period income. As a result, changes in fair value of these derivatives have no immediate earnings impact. Formal documentation, including transaction type and risk management strategy, is maintained for all contracts accounted for as a hedge. At inception and at least every three months thereafter, the hedge contract is assessed to see if it is highly effective in offsetting changes in cash flows or fair values of hedged items. See Note 14 for further information. Captive Insurance Reserves Duke Energy has captive insurance subsidiaries that provide coverage, on an indemnity basis, to the Subsidiary Registrants as well as certain third parties, on a limited basis, for financial losses, primarily related to property, workers’ compensation and general liability. Liabilities include provisions for estimated losses incurred but not yet reported (IBNR), as well as estimated provisions for known claims. IBNR reserve estimates are primarily based upon historical loss experience, industry data and other actuarial assumptions. Reserve estimates are adjusted in future periods as actual losses differ from experience. Duke Energy, through its captive insurance entities, also has reinsurance coverage with third parties for certain losses above a per occurrence and/or aggregate retention. Receivable

Acquisitions and Dispositions

Acquisitions and Dispositions	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Acquisitions and Dispositions	ACQUISITIONS AND DISPOSITIONS ACQUISITIONS The Duke Energy Registrants consolidate assets and liabilities from acquisitions as of the purchase date and include earnings from acquisitions in consolidated earnings after the purchase date. 2016 Acquisition of Piedmont Natural Gas On October 3, 2016, Duke Energy acquired all outstanding common stock of Piedmont for a total cash purchase price of $5.0 billion and assumed Piedmont's existing long-term debt, which had a fair value of approximately $2.0 billion at the time of the acquisition. The acquisition provides a foundation for Duke Energy to establish a broader, long-term strategic natural gas infrastructure platform to complement its existing natural gas pipeline investments and regulated natural gas business in the Midwest. In connection with the closing of the acquisition, Piedmont became a wholly owned subsidiary of Duke Energy. Purchase Price Allocation The purchase price allocation of the Piedmont acquisition is as follows: (in millions) Current assets $ 497 Property, plant and equipment, net 4,714 Goodwill 3,353 Other long-term assets 804 Total assets 9,368 Current liabilities, including current maturities of long-term debt 576 Long-term liabilities 1,790 Long-term debt 2,002 Total liabilities 4,368 Total purchase price $ 5,000 The fair value of Piedmont's assets and liabilities was determined based on significant estimates and assumptions that are judgmental in nature, including the amount and timing of projected future cash flows, discount rates reflecting risk inherent in the future cash flows and market prices of long-term debt. The majority of Piedmont’s operations are subject to the rate-setting authority of the NCUC, the PSCSC and the TPUC and are accounted for pursuant to accounting guidance for regulated operations. The rate-setting and cost recovery provisions currently in place for Piedmont’s regulated operations provide revenues derived from costs, including a return on investment of assets and liabilities included in rate base. Thus, the fair value of Piedmont's assets and liabilities subject to these rate-setting provisions approximates the pre-acquisition carrying values and does not reflect any net valuation adjustments. The significant assets and liabilities for which valuation adjustments were reflected within the purchase price allocation include the acquired equity method investments and long-term debt. The difference between the fair value and the pre-merger carrying values of long-term debt for regulated operations was recorded as a regulatory asset. The excess of the purchase price over the fair value of Piedmont's assets and liabilities on the acquisition date was recorded as goodwill. The goodwill reflects the value paid by Duke Energy primarily for establishing a broader, long-term strategic natural gas infrastructure growth platform, an improved risk profile and expected synergies resulting from the combined entities. Under Securities and Exchange Commission (SEC) regulations, Duke Energy elected not to apply push down accounting to the stand-alone Piedmont financial statements. Accounting Charges Related to the Acquisition Duke Energy incurred pretax non-recurring transaction and integration costs associated with the acquisition of $103 million , $439 million and $9 million for the years ended December 31, 2017, 2016 and 2015, respectively. Amounts recorded on the Consolidated Statements of Operations in 2017 were primarily system integration costs of $71 million related to combining the various operational and financial systems of Duke Energy and Piedmont, including a one-time software impairment resulting from planned accounting system and process integration. A $7 million charge was recorded within Impairment Charges, with the remaining $64 million recorded within Operation, maintenance and other. Amounts recorded in 2016 include: • Interest expense of $234 million related to the acquisition financing, including realized losses on forward-starting interest rate swaps of $190 million . See Note 14 for additional information on the swaps. • Charges of $104 million related to commitments made in conjunction with the transaction, including charitable contributions and a one-time bill credit to Piedmont customers. $10 million was recorded as a reduction in Operating Revenues, with the remaining $94 million recorded within Operation, maintenance and other. • Other transaction and integration costs of $101 million recorded to Operation, maintenance and other, including professional fees and severance. The majority of transition and integration activities are expected to be completed by the end of 2018. Pro Forma Financial Information The following unaudited pro forma financial information reflects the combined results of operations of Duke Energy and Piedmont as if the merger had occurred as of January 1, 2015. The pro forma financial information does not include potential cost savings, intercompany revenues, Piedmont’s earnings from a certain equity method investment sold immediately prior to the merger or non-recurring transaction and integration costs incurred by Duke Energy and Piedmont. The after-tax non-recurring transaction and integration costs incurred by Duke Energy and Piedmont were $279 million and $19 million for the years ended December 31, 2016, and 2015, respectively. This information has been presented for illustrative purposes only and is not necessarily indicative of the consolidated results of operations that would have been achieved or the future consolidated results of operations of Duke Energy. Years Ended December 31, (in millions) 2016 2015 Operating Revenues $ 23,504 $ 23,570 Net Income Attributable to Duke Energy Corporation 2,442 2,877 Piedmont's Earnings Piedmont's revenues and net income included in Duke Energy's Consolidated Statements of Operations for the year ended December 31, 2016, were $367 million and $20 million , respectively. Piedmont's revenues and net income for the year ended December 31, 2016, include the impact of non-recurring transaction costs of $10 million and $46 million , respectively. Acquisition Related Financings and Other Matters Duke Energy financed the Piedmont acquisition with a combination of debt and equity issuances and other cash sources, including: • $3.75 billion of long-term debt issued in August 2016. • $750 million borrowed under the $1.5 billion short-term loan facility in September 2016, which was repaid in December 2016. • 10.6 million shares of common stock issued in October 2016 for net cash proceeds of approximately $723 million . The $4.9 billion senior unsecured bridge financing facility (Bridge Facility) with Barclays Capital, Inc. (Barclays) was terminated following the issuance of the long-term debt. For additional information related to the debt and equity issuances, see Notes 6 and 18, respectively. For additional information regarding Duke Energy's and Piedmont's joint investment in Atlantic Coast Pipeline, LLC (ACP), see Note 4. DISPOSITIONS For the year ended December 31, 2017, the Loss from Discontinued Operations, net of tax, was immaterial. The following table summarizes the (Loss) Income from Discontinued Operations, net of tax recorded on Duke Energy's Consolidated Statements of Operations for the years ended December 31, 2016, and 2015: Years Ended December 31, (in millions) 2016 2015 International Energy Disposal Group $ (534 ) $ 157 Midwest Generation Disposal Group 36 33 Other (a) 90 (13 ) (Loss) Income from Discontinued Operations, net of tax $ (408 ) $ 177 (a) Relates to previously sold businesses not related to the Disposal Groups. The amount for 2016 represents an income tax benefit resulting from immaterial out of period deferred tax liability adjustments. The amount for 2015 includes indemnifications provided for certain legal, tax and environmental matters and foreign currency translation adjustments. 2016 Sale of International Energy In February 2016, Duke Energy announced it had initiated a process to divest its International Energy businesses, excluding the equity method investment in NMC (the International Disposal Group), and in October 2016, announced it had entered into two separate purchase and sale agreements to execute the divestiture. Both sales closed in December of 2016, resulting in available cash proceeds of $1.9 billion , excluding transaction costs. Proceeds were primarily used to reduce Duke Energy holding company (the parent) debt. Existing favorable tax attributes result in no immediate U.S. federal-level cash tax impacts. Details of each transaction are as follows: • On December 20, 2016, Duke Energy closed on the sale of its ownership interests in businesses in Argentina, Chile, Ecuador, El Salvador, Guatemala and Peru to I Squared Capital. The assets sold included approximately 2,230 MW of hydroelectric and natural gas generation capacity, transmission infrastructure and natural gas processing facilities. I Squared Capital purchased the businesses for an enterprise value of $1.2 billion . • On December 29, 2016, Duke Energy closed on the sale of its Brazilian business, which included approximately 2,090 MW of hydroelectric generation capacity, to CTG for an enterprise value of $1.2 billion . With the closing of the CTG deal, Duke Energy finalized its exit from the Latin American market. Assets Held For Sale and Discontinued Operations As a result of the transactions, the International Disposal Group was classified as held for sale and as discontinued operations in the fourth quarter of 2016. Interest expense directly associated with the International Disposal Group was allocated to discontinued operations. No interest from corporate level debt was allocated to discontinued operations. The following table presents the results of the International Disposal Group for the years ended December 31, 2016, and 2015, which are included in (Loss) Income from Discontinued Operations, net of tax in Duke Energy's Consolidated Statements of Operations. Years Ended December 31, (in millions) 2016 2015 Operating Revenues $ 988 $ 1,088 Fuel used in electric generation and purchased power 227 306 Cost of natural gas 43 53 Operation, maintenance and other 341 334 Depreciation and amortization (a) 62 92 Property and other taxes 15 7 Impairment charges (b) 194 13 (Loss) Gains on Sales of Other Assets and Other, net (3 ) 6 Other Income and Expenses, net 58 23 Interest Expense 82 85 Pretax loss on disposal (c) (514 ) — (Loss) Income before income taxes (d) (435 ) 227 Income tax expense (e)(f) 99 70 (Loss) Income from discontinued operations of the International Disposal Group $ (534 ) $ 157 (a) Upon meeting the criteria for assets held for sale, beginning in the fourth quarter of 2016 depreciation expense was ceased. (b) In conjunction with the advancements of marketing efforts during 2016, Duke Energy performed recoverability tests of the long-lived asset groups of International Energy. As a result, Duke Energy determined the carrying value of certain assets in Central America was not fully recoverable and recorded a pretax impairment charge of $194 million . The charge represents the excess of carrying value over the estimated fair value of the assets, which was based on a Level 3 Fair Value measurement that was primarily determined from the income approach using discounted cash flows but also considered market information obtained in 2016. (c) The pretax loss on disposal includes the recognition of cumulative foreign currency translation losses of $620 million as of the disposal date. See the Consolidated Statements of Changes in Equity for additional information. (d) Pretax (Loss) Income attributable to Duke Energy Corporation was $(445) million and $221 million for the years ended December 31, 2016 and 2015, respectively. (e) 2016 amount includes $126 million of income tax expense on the disposal, which primarily reflects in-country taxes incurred as a result of the sale. The after-tax loss on disposal was $640 million . (f) 2016 amount includes an income tax benefit of $95 million . See Note 22 , "Income Taxes," for additional information. Duke Energy has elected not to separately disclose discontinued operations on the Consolidated Statements of Cash Flows. The following table summarizes Duke Energy's cash flows from discontinued operations related to the International Disposal Group. Years Ended December 31, (in millions) 2016 2015 Cash flows provided by (used in): Operating activities $ 204 $ 248 Investing activities (434 ) 177 Other Sale Related Matters During 2017, Duke Energy provided certain transition services to CTG and I Squared Capital. Cash flows related to providing the transition services were not material as of December 31, 2017. All transition services related to the International Disposal Group ended in 2017. Additionally, Duke Energy will reimburse CTG and I Squared Capital for all tax obligations arising from the period preceding consummation on the transactions, totaling approximately $78 million . Duke Energy has not recorded any other liabilities, contingent liabilities or indemnifications related to the International Disposal Group. 2015 Midwest Generation Exit Duke Energy, through indirect subsidiaries, completed the sale of the Midwest Generation Disposal Group to a subsidiary of Dynegy on April 2, 2015, for approximately $2.8 billion in cash. The nonregulated Midwest generation business included generation facilities with approximately 5,900 MW of owned capacity located in Ohio, Pennsylvania and Illinois. On April 1, 2015, prior to the sale, Duke Energy Ohio distributed its indirect ownership interest in the nonregulated Midwest generation business to a subsidiary of Duke Energy Corporation. Duke Energy utilized a revolving credit agreement (RCA) to support the operations of the nonregulated Midwest generation business. Duke Energy Ohio had a power purchase agreement with the Midwest Generation Disposal Group for a portion of its standard service offer (SSO) supply requirement. The agreement and the SSO expired in May 2015. The results of operations of the Midwest Generation Disposal Group prior to the date of sale are classified as discontinued operations in the accompanying Consolidated Statements of Operations. Interest expense associated with the RCA was allocated to discontinued operations. No other interest expense related to corporate level debt was allocated to discontinued operations. Certain immaterial costs that were eliminated as a result of the sale remained in continuing operations. The following table summarizes the Midwest Generation Disposal Group activity recorded within discontinued operations. Duke Energy Duke Energy Ohio Years Ended December 31, Years Ended December 31, (in millions) 2016 2015 2016 2015 Operating Revenues $ — $ 543 $ — $ 412 Pretax Loss on disposal (a) — (45 ) — (52 ) Income (loss) before income taxes (b) $ — $ 59 $ — $ 44 Income tax (benefit) expense (c) (36 ) 26 (36 ) 21 Income (loss) from discontinued operations $ 36 $ 33 $ 36 $ 23 (a) The Loss on disposal includes impairments recorded to adjust the carrying amount of the assets to the estimated fair value of the business, based on the selling price to Dynegy less cost to sell. (b) 2015 amounts include the impact of an $81 million charge for the settlement agreement reached in a lawsuit related to the Midwest Generation Disposal Group. Refer to Note 5 for further information about the lawsuit. (c) 2016 amounts result from immaterial out of period deferred tax liability adjustments.

Business Segments

Business Segments	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Business Segments	BUSINESS SEGMENTS Operating segments are determined based on information used by the chief operating decision-maker in deciding how to allocate resources and evaluate the performance of the business. Duke Energy evaluates segment performance based on segment income. Segment income is defined as income from continuing operations net of income attributable to noncontrolling interests. Segment income, as discussed below, includes intercompany revenues and expenses that are eliminated on the Consolidated Financial Statements. Certain governance costs are allocated to each segment. In addition, direct interest expense and income taxes are included in segment income. Products and services are sold between affiliate companies and reportable segments of Duke Energy at cost. Segment assets as presented in the tables that follow exclude all intercompany assets. Duke Energy Duke Energy's segment structure includes the following segments: Electric Utilities and Infrastructure, Gas Utilities and Infrastructure and Commercial Renewables. The Electric Utilities and Infrastructure segment includes Duke Energy's regulated electric utilities in the Carolinas, Florida and the Midwest. The regulated electric utilities conduct operations through the Subsidiary Registrants that are substantially all regulated and, accordingly, qualify for regulatory accounting treatment. Electric Utilities and Infrastructure also includes Duke Energy's commercial electric transmission infrastructure investments. The Gas Utilities and Infrastructure segment includes Piedmont, Duke Energy's natural gas local distribution companies in Ohio and Kentucky, and Duke Energy's natural gas storage and midstream pipeline investments. Gas Utilities and Infrastructure's operations are substantially all regulated and, accordingly, qualify for regulatory accounting treatment. The Commercial Renewables segment is primarily comprised of nonregulated utility scale wind and solar generation assets located throughout the U.S. The remainder of Duke Energy’s operations is presented as Other, which is primarily comprised of corporate interest expense, unallocated corporate costs, contributions to the Duke Energy Foundation and the operations of Duke Energy’s wholly owned captive insurance subsidiary, Bison Insurance Company Limited (Bison). Other also includes Duke Energy's interest in NMC. See Note 12 for additional information on the investment in NMC. Business segment information is presented in the following tables. Segment assets presented exclude intercompany assets. Year Ended December 31, 2017 Electric Gas Total Utilities and Utilities and Commercial Reportable (in millions) Infrastructure Infrastructure Renewables Segments Other Eliminations Total Unaffiliated Revenues $ 21,300 $ 1,743 $ 460 $ 23,503 $ 62 $ — $ 23,565 Intersegment Revenues 31 93 — 124 76 (200 ) — Total Revenues $ 21,331 $ 1,836 $ 460 $ 23,627 $ 138 $ (200 ) $ 23,565 Interest Expense $ 1,240 $ 105 $ 87 $ 1,432 $ 574 $ (20 ) $ 1,986 Depreciation and amortization 3,010 231 155 3,396 131 — 3,527 Equity in earnings (losses) of unconsolidated affiliates 5 62 (5 ) 62 57 — 119 Income tax expense (benefit) (a) 1,355 116 (628 ) 843 353 — 1,196 Segment income (loss) (b)(c)(d) 3,210 319 441 3,970 (905 ) — 3,065 Add back noncontrolling interest component 5 Loss from discontinued operations, net of tax (6 ) Net income $ 3,064 Capital investments expenditures and acquisitions $ 7,024 $ 907 $ 92 $ 8,023 $ 175 $ — $ 8,198 Segment assets 119,423 11,462 4,156 135,041 2,685 188 137,914 (a) All segments include impacts of the Tax Cuts and Jobs Act (the Tax Act). Electric Utilities and Infrastructure includes a $231 million benefit, Gas Utilities and Infrastructure includes a $26 million benefit, Commercial Renewables includes a $442 million benefit and Other includes charges of $597 million . (b) Electric Utilities and Infrastructure includes after-tax regulatory settlement charges of $98 million . See Note 4 for additional information. (c) Commercial Renewables includes after-tax impairment charges of $74 million related to certain wind projects and the Energy Management Solutions reporting unit. See Notes 10 and 11 for additional information. (d) Other includes $64 million of after-tax costs to achieve the Piedmont merger. See Note 2 for additional information. Year Ended December 31, 2016 Electric Gas Total Utilities and Utilities and Commercial Reportable (in millions) Infrastructure Infrastructure Renewables Segments Other Eliminations Total Unaffiliated Revenues $ 21,336 $ 875 $ 484 $ 22,695 $ 48 $ — $ 22,743 Intersegment Revenues 30 26 — 56 69 (125 ) — Total Revenues $ 21,366 $ 901 $ 484 $ 22,751 $ 117 $ (125 ) $ 22,743 Interest Expense $ 1,136 $ 46 $ 53 $ 1,235 $ 693 $ (12 ) $ 1,916 Depreciation and amortization 2,897 115 130 3,142 152 — 3,294 Equity in earnings (losses) of unconsolidated affiliates (a) 5 19 (82 ) (58 ) 43 — (15 ) Income tax expense (benefit) 1,672 90 (160 ) 1,602 (446 ) — 1,156 Segment income (loss) (b)(c) 3,040 152 23 3,215 (645 ) 1 2,571 Add back noncontrolling interest component 7 Loss from discontinued operations, net of tax (d) (408 ) Net income $ 2,170 Capital investments expenditures and acquisitions (e) $ 6,649 $ 5,519 $ 857 $ 13,025 $ 190 $ — $ 13,215 Segment assets 114,993 10,760 4,377 130,130 2,443 188 132,761 (a) Commercial Renewables includes a pretax impairment charge of $71 million . See Note 12 for additional information. (b) Other includes $329 million of after-tax costs to achieve mergers. Refer to Note 2 for additional information on costs related to the Piedmont merger. (c) Other includes after-tax charges of $57 million related to cost savings initiatives. Refer to Note 19 for further information. (d) Includes a loss on sale of the International Disposal Group. Refer to Note 2 for further information. (e) Other includes $26 million of capital investments expenditures related to the International Disposal Group. Gas Utilities and Infrastructure includes the Piedmont acquisition of $5 billion . Refer to Note 2 for more information on the Piedmont acquisition. Year Ended December 31, 2015 Electric Gas Total Utilities and Utilities and Commercial Reportable (in millions) Infrastructure Infrastructure Renewables Segments Other Eliminations Total Unaffiliated Revenues $ 21,489 $ 536 $ 286 $ 22,311 $ 60 $ — $ 22,371 Intersegment Revenues 32 5 — 37 75 (112 ) — Total Revenues $ 21,521 $ 541 $ 286 $ 22,348 $ 135 $ (112 ) $ 22,371 Interest Expense $ 1,074 $ 25 $ 44 $ 1,143 $ 393 $ (9 ) $ 1,527 Depreciation and amortization 2,735 79 104 2,918 135 — 3,053 Equity in (losses) earnings of unconsolidated affiliates (2 ) 1 (6 ) (7 ) 76 — 69 Income tax expense (benefit) 1,602 44 (128 ) 1,518 (262 ) — 1,256 Segment income (loss) (a)(b)(c) 2,819 73 52 2,944 (299 ) — 2,645 Add back noncontrolling interest component 9 Income from discontinued operations, net of tax (d) 177 Net income $ 2,831 Capital investments expenditures and acquisitions (e) $ 6,852 $ 234 $ 1,019 $ 8,105 $ 258 $ — $ 8,363 Segment assets (f) 109,097 2,637 3,861 115,595 5,373 188 121,156 (a) Electric Utilities and Infrastructure includes an after-tax charge of $58 million related to the Edwardsport settlement. Refer to Note 4 for further information. (b) Other includes $60 million of after-tax costs to achieve mergers. (c) Other includes after-tax charges of $77 million related to cost savings initiatives. Refer to Note 19 for further information. (d) Includes the impact of a settlement agreement reached in a lawsuit related to the Midwest Generation Disposal Group. Refer to Note 5 for further information related to the lawsuit and Note 2 for further information on discontinued operations. (e) Other includes capital investment expenditures of $45 million related to the International Disposal Group. (f) Other includes Assets Held for Sale balances related to the International Disposal Group. Refer to Note 2 for further information. Geographical Information For the years ended December 31, 2017 , 2016 and 2015 , all assets and revenues from continuing operations are within the U.S. Major Customers For the year ended December 31, 2017, revenues from one customer of Duke Energy Progress are $521 million . Duke Energy Progress has one reportable segment, Electric Utilities and Infrastructure. No other subsidiary registrant has an individual customer representing more than 10 percent of its revenues. Products and Services The following table summarizes revenues of the reportable segments by type. Retail Wholesale Retail Total (in millions) Electric Electric Natural Gas Other Revenues 2017 Electric Utilities and Infrastructure $ 18,177 $ 2,104 $ — $ 1,050 $ 21,331 Gas Utilities and Infrastructure — — 1,732 104 1,836 Commercial Renewables — 375 — 85 460 Total Reportable Segments $ 18,177 $ 2,479 $ 1,732 $ 1,239 $ 23,627 2016 Electric Utilities and Infrastructure $ 18,338 $ 2,095 $ — $ 933 $ 21,366 Gas Utilities and Infrastructure — — 871 30 901 Commercial Renewables — 303 — 181 484 Total Reportable Segments $ 18,338 $ 2,398 $ 871 $ 1,144 $ 22,751 2015 Electric Utilities and Infrastructure $ 18,695 $ 2,014 $ — $ 812 $ 21,521 Gas Utilities and Infrastructure — — 546 (5 ) 541 Commercial Renewables — 245 — 41 286 Total Reportable Segments $ 18,695 $ 2,259 $ 546 $ 848 $ 22,348 Duke Energy Ohio Duke Energy Ohio has two reportable operating segments, Electric Utilities and Infrastructure and Gas Utilities and Infrastructure. Electric Utilities and Infrastructure transmits and distributes electricity in portions of Ohio and generates, distributes and sells electricity in portions of Northern Kentucky. Gas Utilities and Infrastructure transports and sells natural gas in portions of Ohio and Northern Kentucky. It conducts operations primarily through Duke Energy Ohio and its wholly owned subsidiary, Duke Energy Kentucky. The remainder of Duke Energy Ohio's operations is presented as Other, which is primarily comprised of governance costs allocated by its parent, Duke Energy, and revenues and expenses related to Duke Energy Ohio's contractual arrangement to buy power from OVEC's (Ohio Valley Electric Corporation) power plants. See Note 13 for additional information on related party transactions. For the years ended December 31, 2017 , 2016 and 2015 , all Duke Energy Ohio assets and revenues are within the U.S. Year Ended December 31, 2017 Electric Gas Total Utilities and Utilities and Reportable (in millions) Infrastructure Infrastructure Segments Other Eliminations Total Total revenues $ 1,373 $ 508 $ 1,881 $ 42 $ — $ 1,923 Interest expense $ 62 $ 28 $ 90 $ 1 $ — $ 91 Depreciation and amortization 178 83 261 $ — — 261 Income tax expense (benefit) 40 39 79 $ (20 ) — 59 Segment income (loss) 138 85 223 $ (30 ) — 193 Loss from discontinued operations, net of tax (1 ) Net income $ 192 Capital expenditures $ 491 $ 195 $ 686 $ — $ — $ 686 Segment assets 5,066 2,758 7,824 66 (15 ) 7,875 Year Ended December 31, 2016 Electric Gas Total Utilities and Utilities and Reportable (in millions) Infrastructure Infrastructure Segments Other Eliminations Total Total revenues $ 1,410 $ 503 $ 1,913 $ 31 $ — $ 1,944 Interest expense $ 58 $ 27 $ 85 $ 1 $ — $ 86 Depreciation and amortization 151 80 231 2 — 233 Income tax expense (benefit) 55 44 99 (21 ) — 78 Segment income (loss) 154 77 231 (39 ) — 192 Income from discontinued operations, net of tax 36 Net income $ 228 Capital expenditures $ 322 $ 154 $ 476 $ — $ — $ 476 Segment assets 4,782 2,696 7,478 62 (12 ) 7,528 Year Ended December 31, 2015 Electric Gas Total Utilities and Utilities and Reportable (in millions) Infrastructure Infrastructure Segments Other Eliminations Total Total revenues $ 1,331 $ 541 $ 1,872 $ 33 $ — $ 1,905 Interest expense $ 53 $ 25 $ 78 $ 1 $ — $ 79 Depreciation and amortization 147 79 226 1 — 227 Income tax expense (benefit) 59 45 104 (23 ) — 81 Segment income (loss) 118 73 191 (41 ) (1 ) 149 Income from discontinued operations, net of tax 23 Net income $ 172 Capital expenditures $ 264 $ 135 $ 399 $ — $ — $ 399 Segment assets 4,534 2,516 7,050 56 (9 ) 7,097

Regulatory Matters

Regulatory Matters	12 Months Ended
	Dec. 31, 2017
Regulated Operations [Abstract]
Regulatory Matters	REGULATORY MATTERS REGULATORY ASSETS AND LIABILITIES The Duke Energy Registrants record regulatory assets and liabilities that result from the ratemaking process. See Note 1 for further information. The following tables present the regulatory assets and liabilities recorded on the Consolidated Balance Sheets of Duke Energy and Progress Energy. See separate tables below for balances by individual registrant. Duke Energy Progress Energy December 31, December 31, (in millions) 2017 2016 2017 2016 Regulatory Assets AROs – coal ash $ 4,025 $ 3,761 $ 1,984 $ 1,830 AROs – nuclear and other 852 684 655 569 Accrued pension and OPEB 2,249 2,387 906 882 Retired generation facilities 480 534 386 422 Debt fair value adjustment 1,197 1,313 — — Net regulatory asset related to income taxes — 894 — 231 Storm cost deferrals 531 153 526 148 Nuclear asset securitized balance, net 1,142 1,193 1,142 1,193 Hedge costs deferrals 234 217 94 91 Derivatives – natural gas supply contracts 142 187 — — Demand side management (DSM)/Energy efficiency (EE) 530 407 281 278 Grid modernization 39 65 — — Vacation accrual 213 196 42 38 Deferred fuel and purchased power 507 156 349 111 Nuclear deferral 119 226 35 134 Post-in-service carrying costs (PISCC) and deferred operating expenses 366 413 38 42 Transmission expansion obligation 46 71 — — Manufactured gas plant (MGP) 91 99 — — Advanced metering infrastructure (AMI) 362 218 150 — NCEMPA deferrals 53 51 53 51 East Bend deferrals 45 32 — — Deferred pipeline integrity costs 54 36 — — Amounts due from customers 64 66 — — Other 538 542 110 103 Total regulatory assets 13,879 13,901 6,751 6,123 Less: current portion 1,437 1,023 741 401 Total noncurrent regulatory assets $ 12,442 $ 12,878 $ 6,010 $ 5,722 Regulatory Liabilities Costs of removal $ 5,968 $ 5,613 $ 2,537 $ 2,198 ARO – nuclear and other 806 461 — — Net regulatory liability related to income taxes 8,113 — 2,802 — Amounts to be refunded to customers 10 45 — — Storm reserve 20 83 — 60 Accrued pension and OPEB 146 174 — — Deferred fuel and purchased power 47 192 1 81 Other 622 722 179 245 Total regulatory liabilities 15,732 7,290 5,519 2,584 Less: current portion 402 409 213 189 Total noncurrent regulatory liabilities $ 15,330 $ 6,881 $ 5,306 $ 2,395 Descriptions of regulatory assets and liabilities summarized in the tables above and below follow. See tables below for recovery and amortization periods at the separate registrants. AROs – coal ash. Represents deferred depreciation and accretion related to the legal obligation to close ash basins. The costs are deferred until recovery treatment has been determined. See Notes 1 and 9 for additional information. AROs – nuclear and other. Represents regulatory assets or liabilities, including deferred depreciation and accretion, related to legal obligations associated with the future retirement of property, plant and equipment, excluding amounts related to coal ash. The AROs relate primarily to decommissioning nuclear power facilities. The amounts also include certain deferred gains and losses on NDTF investments. See Notes 1 and 9 for additional information. Accrued pension and OPEB. Accrued pension and other post-retirement benefit obligations (OPEB) represent regulatory assets and liabilities related to each of the Duke Energy Registrants’ respective shares of unrecognized actuarial gains and losses and unrecognized prior service cost and credit attributable to Duke Energy’s pension plans and OPEB plans. The regulatory asset or liability is amortized with the recognition of actuarial gains and losses and prior service cost and credit to net periodic benefit costs for pension and OPEB plans. The accrued pension and OPEB regulatory asset is expected to be recovered primarily over the average remaining service periods or life expectancies of employees covered by the benefit plans. See Note 21 for additional detail. Retired generation facilities. Represents amounts to be recovered for facilities that have been retired and are probable of recovery. Debt fair value adjustment. Purchase accounting adjustments recorded to state the carrying value of Progress Energy and Piedmont at fair value in connection with the 2012 and 2016 mergers, respectively. Amount is amortized over the life of the related debt. Net regulatory asset or liability related to income taxes. Amounts for all registrants include regulatory liabilities related primarily to impacts from the Tax Act. See Note 22 for additional information. Amounts have no immediate impact on rate base as regulatory assets are offset by deferred tax liabilities. Storm cost deferrals. Represents deferred incremental costs incurred related to extraordinary weather-related events. Nuclear asset securitized balance, net. Represents the balance associated with Crystal River Unit 3 retirement approved for recovery by the FPSC on September 15, 2015, and the upfront financing costs securitized in 2016 with issuance of the associated bonds. The regulatory asset balance is net of the AFUDC equity portion. Hedge costs and other deferrals. Amounts relate to unrealized gains and losses on derivatives recorded as a regulatory asset or liability, respectively, until the contracts are settled. Derivatives – natural gas supply contracts . Represents costs for certain long-dated, fixed quantity forward gas supply contracts, which are recoverable through PGA clauses. DSM/EE. Deferred costs related to various DSM and EE programs recoverable through various mechanisms. Grid modernization. Amounts represent deferred depreciation and operating expenses as well as carrying costs on the portion of capital expenditures placed in service but not yet reflected in retail rates as plant in service. Vacation accrual. Generally recovered within one year. Deferred fuel and purchased power. Represents certain energy-related costs that are recoverable or refundable as approved by the applicable regulatory body. Nuclear deferral. Includes amounts related to levelizing nuclear plant outage costs, which allows for the recognition of nuclear outage expenses over the refueling cycle rather than when the outage occurs, resulting in the deferral of operations and maintenance costs associated with refueling. Post-in-service carrying costs and deferred operating expenses. Represents deferred depreciation and operating expenses as well as carrying costs on the portion of capital expenditures placed in service but not yet reflected in retail rates as plant in service. Gasification services agreement buyout. The IURC authorized Duke Energy Indiana to recover costs incurred to buy out a gasification services agreement, including carrying costs through 2017. Transmission expansion obligation. Represents transmission expansion obligations related to Duke Energy Ohio’s withdrawal from Midcontinent Independent System Operator, Inc. (MISO). MGP. Represents remediation costs incurred at former MGP sites and the deferral of costs to be incurred at the East End and West End sites through 2019. AMI. Represents deferred costs related to the installation of AMI meters and remaining net book value of non-AMI meters to be replaced at Duke Energy Carolinas, net book value of existing meters at Duke Energy Florida , Duke Energy Progress and Duke Energy Ohio and expected future recovery of net book value of electromechanical meters that have been replaced with AMI meters at Duke Energy Indiana. NCEMPA deferrals. Represents retail allocated cost deferrals and returns associated with the additional ownership interest in assets acquired from NCEMPA in 2015. East Bend deferrals. Represents both deferred operating expenses and deferred depreciation as well as carrying costs on the portion of East Bend Generating Station (East Bend) that was acquired from Dayton Power and Light and that had been previously operated as a jointly owned facility. Deferred pipeline integrity costs. Represents pipeline integrity management costs in compliance with federal regulations recovered through a rider mechanism. Amounts due from customers. Relates primarily to margin decoupling and IMR recovery mechanisms. Costs of removal. Represents funds received from customers to cover the future removal of property, plant and equipment from retired or abandoned sites as property is retired. Also includes certain deferred gains on NDTF investments. Amounts to be refunded to customers. Represents required rate reductions to retail customers by the applicable regulatory body. Storm reserve. Amounts are used to offset future incurred costs for named storms as approved by regulatory commissions. RESTRICTIONS ON THE ABILITY OF CERTAIN SUBSIDIARIES TO MAKE DIVIDENDS, ADVANCES AND LOANS TO DUKE ENERGY As a condition to the approval of merger transactions, the NCUC, PSCSC, PUCO, KPSC and IURC imposed conditions on the ability of Duke Energy Carolinas, Duke Energy Progress, Duke Energy Ohio, Duke Energy Kentucky, Duke Energy Indiana and Piedmont to transfer funds to Duke Energy through loans or advances, as well as restricted amounts available to pay dividends to Duke Energy. Certain subsidiaries may transfer funds to the parent by obtaining approval of the respective state regulatory commissions. These conditions imposed restrictions on the ability of the public utility subsidiaries to pay cash dividends as discussed below. Duke Energy Progress and Duke Energy Florida also have restrictions imposed by their first mortgage bond indentures, which, in certain circumstances, limit their ability to make cash dividends or distributions on common stock. Amounts restricted as a result of these provisions were not material at December 31, 2017 . Additionally, certain other subsidiaries of Duke Energy have restrictions on their ability to dividend, loan or advance funds to Duke Energy due to specific legal or regulatory restrictions, including, but not limited to, minimum working capital and tangible net worth requirements. The restrictions discussed below were less than 25 percent of Duke Energy's and Progress Energy's net assets at December 31, 2017 . Duke Energy Carolinas Duke Energy Carolinas must limit cumulative distributions subsequent to mergers to (i) the amount of retained earnings on the day prior to the closing of the mergers, plus (ii) any future earnings recorded. Duke Energy Progress Duke Energy Progress must limit cumulative distributions subsequent to the mergers between Duke Energy and Progress Energy and Duke Energy and Piedmont to (i) the amount of retained earnings on the day prior to the closing of the respective mergers, plus (ii) any future earnings recorded. Duke Energy Ohio Duke Energy Ohio will not declare and pay dividends out of capital or unearned surplus without the prior authorization of the PUCO. Duke Energy Ohio received FERC and PUCO approval to pay dividends from its equity accounts that are reflective of the amount that it would have in its retained earnings account had push-down accounting for the Cinergy Corp. (Cinergy) merger not been applied to Duke Energy Ohio’s balance sheet. The conditions include a commitment from Duke Energy Ohio that equity, adjusted to remove the impacts of push-down accounting, will not fall below 30 percent of total capital. Duke Energy Kentucky is required to pay dividends solely out of retained earnings and to maintain a minimum of 35 percent equity in its capital structure. Duke Energy Indiana Duke Energy Indiana must limit cumulative distributions subsequent to the merger between Duke Energy and Cinergy to (i) the amount of retained earnings on the day prior to the closing of the merger, plus (ii) any future earnings recorded. In addition, Duke Energy Indiana will not declare and pay dividends out of capital or unearned surplus without prior authorization of the IURC. Piedmont Piedmont must limit cumulative distributions subsequent to the acquisition of Piedmont by Duke Energy to (i) the amount of retained earnings on the day prior to the closing of the merger, plus (ii) any future earnings recorded. RATE RELATED INFORMATION The NCUC, PSCSC, FPSC, IURC, PUCO, TPUC and KPSC approve rates for retail electric and natural gas services within their states. The FERC approves rates for electric sales to wholesale customers served under cost-based rates (excluding Ohio and Indiana), as well as sales of transmission service. The FERC also regulates certification and siting of new interstate natural gas pipeline projects. All Registrants Tax Act Impacts On December 22, 2017, President Trump signed the Tax Act into law, which, among other provisions, reduces the maximum federal corporate income tax rate from 35 percent to 21 percent, effective January 1, 2018. As a result of the Tax Act, the Subsidiary Registrants revalued their deferred tax assets and deferred tax liabilities, as of December 31, 2017, to account for the future impact of lower corporate tax rates on these deferred tax amounts. For the Subsidiary Registrants regulated operations, where the reduction is expected to be accounted for and applied to customers’ rates in future commission proceedings, including rate proceedings, the net remeasurement has been deferred as a regulatory liability. Each of the Subsidiary Registrant's regulatory commissions is reviewing the Tax Act to determine the potential impacts on customer rates. Beginning in January 2018, the Subsidiary Registrants will defer the estimated ongoing impacts of the Tax Act that are expected to be returned to customers. See Note 22 for additional information. Duke Energy Carolinas and Duke Energy Progress Ash Basin Closure Costs Deferral On December 30, 2016, Duke Energy Carolinas and Duke Energy Progress filed a joint petition with the NCUC seeking an accounting order authorizing deferral of certain costs incurred in connection with federal and state environmental remediation requirements related to the permanent closure of ash basins and other ash storage units at coal-fired generating facilities that have provided or are providing generation to customers located in North Carolina. Initial comments were received in March 2017, and reply comments were filed on April 19, 2017. The NCUC has consolidated Duke Energy Carolinas' and Duke Energy Progress’ coal ash deferral requests into their respective general rate case dockets for decision. See "2017 North Carolina Rate Case" sections below for additional discussion. Duke Energy Carolinas and Duke Energy Progress cannot predict the outcome of this matter. Duke Energy Carolinas Regulatory Assets and Liabilities The following tables present the regulatory assets and liabilities recorded on Duke Energy Carolinas' Consolidated Balance Sheets. December 31, Earns/Pays Recovery/Refund (in millions) 2017 2016 a Return Period Ends Regulatory Assets (a) AROs - coal ash $ 1,645 $ 1,536 (i) (b) AROs - nuclear and other — 9 Accrued pension and OPEB 410 481 (j) Retired generation facilities (c) 29 39 X 2023 Net regulatory asset related to income taxes (d) — 484 Hedge costs deferrals (c) 109 93 X 2041 DSM/EE 210 122 (h) (h) Vacation accrual 83 76 (e) 2018 Deferred fuel and purchased power 140 — (f) 2018 Nuclear deferral 84 92 2019 PISCC (c) 35 70 X (b) AMI 185 172 X (b) Other 222 223 (b) Total regulatory assets 3,152 3,397 Less: current portion 299 238 Total noncurrent regulatory assets $ 2,853 $ 3,159 Regulatory Liabilities (a) Costs of removal (c) $ 2,054 $ 2,015 X (g) ARO - nuclear and other 806 461 (b) Net regulatory liability related to income taxes (d) 3,028 — (b) Storm reserve (c) 20 22 (b) Accrued pension and OPEB 44 46 (j) Deferred fuel and purchased power 46 105 (f) 2018 Other 359 352 (b) Total regulatory liabilities 6,357 3,001 Less: current portion 126 161 Total noncurrent regulatory liabilities $ 6,231 $ 2,840 (a) Regulatory assets and liabilities are excluded from rate base unless otherwise noted. (b) The expected recovery or refund period varies or has not been determined. (c) Included in rate base. (d) Includes regulatory liabilities related to the change in the North Carolina tax rate discussed in Note 22 . (e) Earns a return on outstanding balance in North Carolina. (f) Pays interest on over-recovered costs in North Carolina. Includes certain purchased power costs in North Carolina and South Carolina and costs of distributed energy in South Carolina. (g) Recovered over the life of the associated assets. (h) Includes incentives on DSM/EE investments and is recovered through an annual rider mechanism. (i) Earns a debt return on coal ash expenditures for North Carolina and South Carolina retail customers. (j) Recovered primarily over the average remaining service periods or life expectancies of employees covered by the benefit plans. See Note 21 for additional detail. 2017 North Carolina Rate Case On August 25, 2017, Duke Energy Carolinas filed an application with the NCUC for a rate increase for retail customers of approximately $647 million , which represents an approximate 13.6 percent increase in annual base revenues. The rate increase is driven by capital investments subsequent to the previous base rate case, including grid improvement projects, AMI, investments in customer service technologies, costs of complying with coal combustion residuals (CCR) regulations and the North Carolina Coal Ash Management Act of 2014 (Coal Ash Act) and recovery of costs related to licensing and development of the William States Lee III Nuclear Station (Lee Nuclear Station) discussed below. On January 23, 2018, the North Carolina Public Staff filed testimony recommending an overall rate decrease of approximately $290 million . An evidentiary hearing is scheduled to begin on February 27, 2018, and a decision and revised customer rates are expected by mid-2018. Duke Energy Carolinas cannot predict the outcome of this matter. FERC Formula Rate Matter On July 31, 2017, Piedmont Municipal Power Agency (PMPA) filed a complaint with FERC against Duke Energy Carolinas alleging that Duke Energy Carolinas misapplied the formula rate under the purchase power agreement (PPA) between the parties by including regulatory amortization in its rates without FERC approval. Duke Energy Carolinas disagreed with PMPA as it believed it was properly applying its FERC filed rate. On February 15, 2018, FERC issued an order ruling in favor of PMPA and ordered Duke Energy Carolinas to refund to PMPA all amounts improperly collected under the PPA. Resolution of this matter is not expected to be material. Lincoln County Combustion Turbine On December 7, 2017, the NCUC issued an order approving a Certificate of Public Convenience and Necessity (CPCN) for Duke Energy Carolinas' proposed 402-megawatt (MW) simple cycle, advanced combustion turbine natural gas-fueled electric generating unit at its existing Lincoln County site. The CPCN also includes construction of related transmission and natural gas pipeline interconnection facilities. Construction is scheduled to begin in 2018 with an extended commissioning and validation period from 2020-2024 and an estimated commercial operation date in 2024. As a condition of the approval, Duke Energy Carolinas will not seek recovery of costs associated with the project until it is placed into commercial operation. Advanced Metering Infrastructure Deferral On July 12, 2016, the PSCSC issued an accounting order for Duke Energy Carolinas to defer the financial effects of depreciation expense incurred for the installation of AMI meters, the carrying costs on the investment at its weighted average cost of capital (WACC) and the carrying costs on the deferred costs at its WACC not to exceed $45 million . The decision also allows Duke Energy Carolinas to continue to depreciate the non-AMI meters to be replaced. Current retail rates will not change as a result of the decision and the ability of interested parties to challenge the reasonableness of expenditures in subsequent proceedings is not limited. William States Lee Combined Cycle Facility On April 9, 2014, the PSCSC granted Duke Energy Carolinas and North Carolina Electric Membership Corporation (NCEMC) a Certificate of Environmental Compatibility and Public Convenience and Necessity (CECPCN) for the construction and operation of a 750-MW combined-cycle natural gas-fired generating plant at Duke Energy Carolinas' existing William States Lee Generating Station in Anderson, South Carolina. Duke Energy Carolinas began construction in July 2015 and estimates a cost to build of $600 million for its share of the facility, including allowance for funds used during construction (AFUDC). The project is expected to be commercially available in the first quarter of 2018. NCEMC will own approximately 13 percent of the project. On July 3, 2014, the South Carolina Coastal Conservation League (SCCL) and Southern Alliance for Clean Energy (SACE) jointly filed a Notice of Appeal with the Court of Appeals of South Carolina (S.C. Court of Appeals) seeking the court's review of the PSCSC's decision, claiming the PSCSC did not properly consider a request related to a proposed solar facility prior to granting approval of the CECPCN. The S.C. Court of Appeals affirmed the PSCSC's decision on February 10, 2016, and on March 24, 2016, denied a request for rehearing filed by SCCL and SACE. On April 21, 2016, SCCL and SACE petitioned the South Carolina Supreme Court for review of the S.C. Court of Appeals decision. On March 24, 2017, the South Carolina Supreme Court denied the request for review, thus concluding the matter. Lee Nuclear Station In December 2007, Duke Energy Carolinas applied to the NRC for combined operating licenses (COLs) for two Westinghouse AP1000 reactors for the proposed William States Lee III Nuclear Station to be located at a site in Cherokee County, South Carolina. The NCUC and PSCSC concurred with the prudency of Duke Energy Carolinas incurring certain project development and preconstruction costs through several separately issued orders, although full cost recovery is not guaranteed. In December 2016, the NRC issued a COL for each reactor. Duke Energy Carolinas is not required to build the nuclear reactors as result of the COLs being issued. On March 29, 2017, Westinghouse filed for voluntary Chapter 11 bankruptcy in the U.S. Bankruptcy Court for the Southern District of New York. As part of its 2017 North Carolina Rate Case discussed above, Duke Energy Carolinas is seeking NCUC approval to cancel the development of the Lee Nuclear Station project due to the Westinghouse bankruptcy filing and other market activity and is requesting recovery of incurred licensing and development costs. Duke Energy Carolinas will maintain the license issued by the NRC in December 2016 as an option for potential future development. As of December 31, 2017 , Duke Energy Carolinas has incurred approximately $558 million of costs, including AFUDC, related to the project. These project costs are included in Net property, plant and equipment on Duke Energy Carolinas’ Consolidated Balance Sheets. Duke Energy Carolinas cannot predict the outcome of this matter. Duke Energy Progress Regulatory Assets and Liabilities The following tables present the regulatory assets and liabilities recorded on Duke Energy Progress' Consolidated Balance Sheets. December 31, Earns/Pays Recovery/Refund (in millions) 2017 2016 a Return Period Ends Regulatory Assets (a) AROs - coal ash $ 1,975 $ 1,822 (i) (b) AROs - nuclear and other 359 275 (c) Accrued pension and OPEB 430 423 (l) Retired generation facilities 170 165 X 2023 Net regulatory asset related to income taxes — 7 (d) Storm cost deferrals (e) 150 148 X (b) Hedge costs deferrals 64 66 (b) DSM/EE (f) 264 263 (j) 2018 Vacation accrual 42 38 2018 Deferred fuel and purchased power 130 24 (g) 2018 Nuclear deferral 35 38 2019 PISCC and deferred operating expenses 38 42 X 2054 AMI 75 — (b) NCEMPA deferrals 53 51 (h) 2042 Other 74 69 (b) Total regulatory assets 3,859 3,431 Less: current portion 352 188 Total noncurrent regulatory assets $ 3,507 $ 3,243 Regulatory Liabilities (a) Costs of removal $ 2,122 $ 1,840 X (k) Net regulatory liability related to income taxes 1,854 — (b) Deferred fuel and purchased power 1 64 (g) 2018 Other 161 200 (b) Total regulatory liabilities 4,138 2,104 Less: current portion 139 158 Total noncurrent regulatory liabilities $ 3,999 $ 1,946 (a) Regulatory assets and liabilities are excluded from rate base unless otherwise noted. (b) The expected recovery or refund period varies or has not been determined. (c) Recovery period for costs related to nuclear facilities runs through the decommissioning period of each unit. (d) Recovery over the life of the associated assets. Includes regulatory liabilities related to the change in the North Carolina tax rate discussed in Note 22 . (e) South Carolina storm costs are included in rate base. (f) Included in rate base. (g) Pays interest on over-recovered costs in North Carolina. Includes certain purchased power costs in North Carolina and South Carolina and costs of distributed energy in South Carolina. (h) South Carolina retail allocated costs are earning a return. (i) Earns a debt return on coal ash expenditures for North Carolina and South Carolina retail customers. (j) Includes incentives on DSM/EE investments. (k) Recovered over the life of the associated assets. (l) Recovered primarily over the average remaining service periods or life expectancies of employees covered by the benefit plans. See Note 21 for additional detail. 2017 North Carolina Rate Case On June 1, 2017, Duke Energy Progress filed an application with the NCUC for a rate increase for retail customers of approximately $477 million , which represented an approximate 14.9 percent increase in annual base revenues. Subsequent to the filing, Duke Energy Progress adjusted the requested amount to $420 million , representing an approximate 13 percent increase. The rate increase is driven by capital investments subsequent to the previous base rate case, costs of complying with CCR regulations and the Coal Ash Act, costs relating to storm recovery, investments in customer service technologies and recovery of costs associated with renewable purchased power. On November 22, 2017, Duke Energy Progress and the North Carolina Public Staff filed an Agreement and Stipulation of Partial Settlement resolving certain portions of the proceeding, pending NCUC approval. Terms of the settlement include a return on equity of 9.9 percent and a capital structure of 52 percent equity and 48 percent debt. As a result of the settlement, in 2017 Duke Energy Progress recorded pretax charges totaling approximately $25 million to Impairment charges and Operation, maintenance and other on the Consolidated Income Statements, principally related to disallowances from rate base of certain projects at the Mayo and Sutton plants. The settlement does not include agreement on portions of the rate case relating to recovery of deferred storm recovery costs and coal ash basin deferred costs, which will be decided by the NCUC separately. Taking into consideration the settled portions and Duke Energy Progress’ requested recovery of the non-settled portions, the requested rate increase is reduced to approximately $300 million . An evidentiary hearing ended December 7, 2017, and a decision and revised customer rates are expected in the first quarter of 2018. Duke Energy Progress cannot predict the outcome of this matter. Storm Cost Deferral Filings On December 16, 2016, Duke Energy Progress filed a petition with the NCUC requesting an accounting order to defer certain costs incurred in connection with response to Hurricane Matthew and other significant storms in 2016. The final estimate of incremental operation and maintenance and capital costs of $116 million was filed with the NCUC in September 2017. On March 15, 2017, the NCUC Public Staff filed comments supporting deferral of a portion of Duke Energy Progress’ requested amount. Duke Energy Progress filed reply comments on April 12, 2017. On July 10, 2017, the NCUC consolidated Duke Energy Progress' storm deferral request into the Duke Energy Progress rate case docket for decision. See "2017 North Carolina Rate Case" for additional discussion. As of December 31, 2017, Duke Energy Progress has approximately $77 million included in Regulatory assets on its Consolidated Balance Sheets. Duke Energy Progress cannot predict the outcome of this matter. On December 16, 2016, Duke Energy Progress filed a petition with the PSCSC requesting an accounting order to defer certain costs incurred related to repairs and restoration of service following Hurricane Matthew. The final estimate of incremental operation and maintenance and capital costs was approximately $74 million . In January 2017, the PSCSC approved the deferral request and issued an accounting order. As of December 31, 2017, Duke Energy Progress has approximately $73 million included in Regulatory assets on its Consolidated Balance Sheets. South Carolina Rate Case In December 2016, the PSCSC approved a rate case settlement agreement among the ORS (Office of Regulatory Staff), intervenors and Duke Energy Progress. Terms of the settlement agreement included an approximate $56 million increase in revenues over a two-year period. An increase of approximately $38 million in revenues was effective January 1, 2017, and an additional increase of approximately $18.5 million in revenues was effective January 1, 2018. Duke Energy Progress amortized approximately $18.5 million from the cost of removal reserve in 2017. Other settlement terms included a rate of return on equity of 10.1 percent , recovery of coal ash costs incurred from January 1, 2015, through June 30, 2016, over a 15 ‑year period and ongoing deferral of allocated ash basin closure costs from July 1, 2016, until the next base rate case. The settlement also provides that Duke Energy Progress will not seek an increase in rates in South Carolina to occur prior to 2019, with limited exceptions. Western Carolinas Modernization Plan On November 4, 2015, Duke Energy Progress announced a Western Carolinas Modernization Plan, which included retirement of the existing Asheville coal-fired plant, the construction of two 280 ‑ MW combined-cycle natural gas plants having dual fuel capability, with the option to build a third natural gas simple cycle unit in 2023 based upon the outcome of initiatives to reduce the region's power demand. The plan also included upgrades to existing transmission lines and substations, installation of solar generation and a pilot battery storage project. These investments will be made within the next seven years. Duke Energy Progress is also working with the local natural gas distribution company to upgrade an existing natural gas pipeline to serve the natural gas plant. On March 28, 2016, the NCUC issued an order approving a CPCN for the new combined-cycle natural gas plants, but denying the CPCN for the contingent simple cycle unit without prejudice to Duke Energy Progress to refile for approval in the future. On March 28, 2017, Duke Energy Progress filed an annual progress report for the construction of the combined-cycle plants with the NCUC, with an estimated cost of $893 million . Site preparation activities for the combined-cycle plants are underway and construction of these plants began in 2017, with an expected in-service date in late 2019. Duke Energy Progress plans to file for future approvals related to the proposed solar generation and pilot battery storage project. The carrying value of the 376 -MW Asheville coal-fired plant, including associated ash basin closure costs, of $385 million and $492 million are included in Generation facilities to be retired, net on Duke Energy Progress' Consolidated Balance Sheets as of December 31, 2017 , and 2016 , respectively. Shearon Harris Nuclear Plant Expansion In 2006, Duke Energy Progress selected a site at Harris to evaluate for possible future nuclear expansion. On February 19, 2008, Duke Energy Progress filed its COL application with the NRC for two Westinghouse AP1000 reactors at Harris, which the NRC docketed for review. On May 2, 2013, Duke Energy Progress filed a letter with the NRC requesting the NRC to suspend its review activities associated with the COL at the Harris site. The NCUC and PSCSC approved deferral of retail costs. Total deferred costs were approximately $47 million as of December 31, 2017, and are recorded in Regulatory assets on Duke Energy Progress’ Consolidated Balance Sheets. On November 17, 2016, the FERC approved Duke Energy Progress’ rate recovery request filing for the wholesale ratepayers’ share of the abandonment costs, including a debt only return to be recovered through r

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	COMMITMENTS AND CONTINGENCIES INSURANCE General Insurance The Duke Energy Registrants have insurance and reinsurance coverage either directly or through indemnification from Duke Energy’s captive insurance company, Bison, and its affiliates, consistent with companies engaged in similar commercial operations with similar type properties. The Duke Energy Registrants’ coverage includes (i) commercial general liability coverage for liabilities arising to third parties for bodily injury and property damage; (ii) workers’ compensation; (iii) automobile liability coverage; and (iv) property coverage for all real and personal property damage. Real and personal property damage coverage excludes electric transmission and distribution lines, but includes damages arising from boiler and machinery breakdowns, earthquakes, flood damage and extra expense, but not outage or replacement power coverage. All coverage is subject to certain deductibles or retentions, sublimits, exclusions, terms and conditions common for companies with similar types of operations. The Duke Energy Registrants self-insure their electric transmission and distribution lines against loss due to storm damage and other natural disasters. As discussed further in Note 4 , Duke Energy Florida maintains a storm damage reserve and has a regulatory mechanism to recover the cost of named storms on an expedited basis. The cost of the Duke Energy Registrants’ coverage can fluctuate from year to year reflecting claims history and conditions of the insurance and reinsurance markets. In the event of a loss, terms and amounts of insurance and reinsurance available might not be adequate to cover claims and other expenses incurred. Uninsured losses and other expenses, to the extent not recovered by other sources, could have a material effect on the Duke Energy Registrants’ results of operations, cash flows or financial position. Each company is responsible to the extent losses may be excluded or exceed limits of the coverage available. Nuclear Insurance Duke Energy Carolinas owns and operates the McGuire Nuclear Station (McGuire) and the Oconee Nuclear Station (Oconee) and operates and has a partial ownership interest in the Catawba Nuclear Station (Catawba). McGuire and Catawba each have two reactors. Oconee has three reactors. The other joint owners of Catawba reimburse Duke Energy Carolinas for certain expenses associated with nuclear insurance per the Catawba joint owner agreements. Duke Energy Progress owns and operates the Robinson Nuclear Plant (Robinson), Brunswick and Harris. Robinson and Harris each have one reactor. Brunswick has two reactors. Duke Energy Florida owns Crystal River Unit 3, which permanently ceased operation in 2013 and reached a SAFSTOR condition in January 2018 after the successful transfer of all used nuclear fuel assemblies to an onsite dry cask storage facility. In the event of a loss, terms and amounts of insurance available might not be adequate to cover property damage and other expenses incurred. Uninsured losses and other expenses, to the extent not recovered by other sources, could have a material effect on Duke Energy Carolinas’, Duke Energy Progress’ and Duke Energy Florida’s results of operations, cash flows or financial position. Each company is responsible to the extent losses may be excluded or exceed limits of the coverage available. Nuclear Liability Coverage The Price-Anderson Act requires owners of nuclear reactors to provide for public nuclear liability protection per nuclear incident up to a maximum total financial protection liability. The maximum total financial protection liability, which is approximately $13.4 billion , is subject to change every five years for inflation and for the number of licensed reactors. Total nuclear liability coverage consists of a combination of private primary nuclear liability insurance coverage and a mandatory industry risk-sharing program to provide for excess nuclear liability coverage above the maximum reasonably available private primary coverage. The U.S. Congress could impose revenue-raising measures on the nuclear industry to pay claims. Primary Liability Insurance Duke Energy Carolinas, Duke Energy Progress and Duke Energy Florida have purchased the maximum reasonably available private primary nuclear liability insurance as required by law, which is $450 million per station. Excess Liability Program This program provides $13 billion of coverage per incident through the Price-Anderson Act’s mandatory industrywide excess secondary financial protection program of risk pooling. This amount is the product of potential cumulative retrospective premium assessments of $127 million times the current 102 licensed commercial nuclear reactors in the U.S. Under this program, licensees could be assessed retrospective premiums to compensate for public nuclear liability damages in the event of a nuclear incident at any licensed facility in the U.S. Retrospective premiums may be assessed at a rate not to exceed $19 million per year per licensed reactor for each incident. The assessment may be subject to state premium taxes. Nuclear Property and Accidental Outage Coverage Duke Energy Carolinas, Duke Energy Progress and Duke Energy Florida are members of Nuclear Electric Insurance Limited (NEIL), an industry mutual insurance company, which provides property damage, nuclear accident decontamination and premature decommissioning insurance for each station for losses resulting from damage to its nuclear plants, either due to accidents or acts of terrorism. Additionally, NEIL provides accidental outage coverage for each station for losses in the event of a major accidental outage at an insured nuclear station. Pursuant to regulations of the NRC, each company’s property damage insurance policies provide that all proceeds from such insurance be applied, first, to place the plant in a safe and stable condition after a qualifying accident and second, to decontaminate the plant before any proceeds can be used for decommissioning, plant repair or restoration. Losses resulting from acts of terrorism are covered as common occurrences, such that if terrorist acts occur against one or more commercial nuclear power plants insured by NEIL within a 12-month period, they would be treated as one event and the owners of the plants where the act occurred would share one full limit of liability. The full limit of liability is currently $3.2 billion . NEIL sublimits the total aggregate for all of their policies for non-nuclear terrorist events to approximately $1.83 billion . Each nuclear facility has accident property damage, decontamination and premature decommissioning liability insurance from NEIL with limits of $1.5 billion , except for Crystal River Unit 3. Crystal River Unit 3’s limit is $50 million and is on an actual cash value basis. All nuclear facilities except for Catawba and Crystal River Unit 3 also share an additional $1.25 billion nuclear accident insurance limit above their dedicated underlying limit. This shared additional excess limit is not subject to reinstatement in the event of a loss. Catawba has a dedicated $1.25 billion of additional nuclear accident insurance limit above its dedicated underlying limit. Catawba and Oconee also have an additional $750 million of non-nuclear accident property damage limit. All coverages are subject to sublimits and significant deductibles. NEIL’s Accidental Outage policy provides some coverage, such as business interruption, for losses in the event of a major accident property damage outage of a nuclear unit. Coverage is provided on a weekly limit basis after a significant waiting period deductible and at 100 percent of the available weekly limits for 52 weeks and 80 percent of the available weekly limits for the next 110 weeks. Coverage is provided until these available weekly periods are met where the accidental outage policy limit will not exceed $490 million for McGuire and Catawba, $462 million for Brunswick, $448 million for Harris, $434 million for Oconee and $378 million for Robinson. NEIL sublimits the accidental outage recovery to the first 104 weeks of coverage not to exceed $328 million from non-nuclear accidental property damage. Coverage amounts decrease in the event more than one unit at a station is out of service due to a common accident. All coverages are subject to sublimits and significant deductibles. Potential Retroactive Premium Assessments In the event of NEIL losses, NEIL’s board of directors may assess member companies' retroactive premiums of amounts up to 10 times their annual premiums for up to six years after a loss. NEIL has never exercised this assessment. The maximum aggregate annual retrospective premium obligations for Duke Energy Carolinas, Duke Energy Progress and Duke Energy Florida are $146 million , $96 million and $1 million , respectively. Duke Energy Carolinas' maximum assessment amount includes 100 percent of potential obligations to NEIL for jointly owned reactors. Duke Energy Carolinas would seek reimbursement from the joint owners for their portion of these assessment amounts. ENVIRONMENTAL The Duke Energy Registrants are subject to federal, state and local regulations regarding air and water quality, hazardous and solid waste disposal and other environmental matters. These regulations can be changed from time to time, imposing new obligations on the Duke Energy Registrants. The following environmental matters impact all of the Duke Energy Registrants. Remediation Activities In addition to the ARO recorded as a result of various environmental regulations, discussed in Note 9 , the Duke Energy Registrants are responsible for environmental remediation at various sites. These include certain properties that are part of ongoing operations and sites formerly owned or used by Duke Energy entities. These sites are in various stages of investigation, remediation and monitoring. Managed in conjunction with relevant federal, state and local agencies, remediation activities vary based upon site conditions and location, remediation requirements, complexity and sharing of responsibility. If remediation activities involve joint and several liability provisions, strict liability, or cost recovery or contribution actions, the Duke Energy Registrants could potentially be held responsible for environmental impacts caused by other potentially responsible parties and may also benefit from insurance policies or contractual indemnities that cover some or all cleanup costs. Liabilities are recorded when losses become probable and are reasonably estimable. The total costs that may be incurred cannot be estimated because the extent of environmental impact, allocation among potentially responsible parties, remediation alternatives and/or regulatory decisions have not yet been determined at all sites. Additional costs associated with remediation activities are likely to be incurred in the future and could be significant. Costs are typically expensed as Operation, maintenance and other in the Consolidated Statements of Operations unless regulatory recovery of the costs is deemed probable. The following tables contain information regarding reserves for probable and estimable costs related to the various environmental sites. These reserves are recorded in Accounts payable within Current Liabilities and Other within Other Noncurrent Liabilities on the Consolidated Balance Sheets. Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Balance at December 31, 2014 $ 92 $ 10 $ 17 $ 5 $ 12 $ 54 $ 10 Provisions/adjustments 11 1 4 — 4 1 5 Cash reductions (9 ) (1 ) (4 ) (2 ) (2 ) (1 ) (3 ) Balance at December 31, 2015 94 10 17 3 14 54 12 Provisions/adjustments 19 4 7 2 4 7 1 Cash reductions (15 ) (4 ) (6 ) (2 ) (4 ) (2 ) (3 ) Balance at December 31, 2016 98 10 18 3 14 59 10 Provisions/adjustments 8 3 3 2 2 3 (4 ) Cash reductions (25 ) (3 ) (6 ) (2 ) (4 ) (15 ) (1 ) Balance at December 31, 2017 $ 81 $ 10 $ 15 $ 3 $ 12 $ 47 $ 5 As of December 31, 2016, October 31, 2016, 2015 and 2014, Piedmont's environmental reserve was $1 million . In 2017, a $1 million provision was recorded, resulting in a reserve balance of $2 million at December 31, 2017. Additional losses in excess of recorded reserves that could be incurred for the stages of investigation, remediation and monitoring for environmental sites that have been evaluated at this time are not material except as presented in the table below. (in millions) Duke Energy $ 56 Duke Energy Carolinas 19 Duke Energy Ohio 30 Piedmont 2 North Carolina and South Carolina Ash Basins In February 2014, a break in a stormwater pipe beneath an ash basin at Duke Energy Carolinas’ retired Dan River Steam Station caused a release of ash basin water and ash into the Dan River. Duke Energy Carolinas estimates 30,000 to 39,000 tons of ash and 24 million to 27 million gallons of basin water were released into the river. In July 2014, Duke Energy completed remediation work identified by the EPA and continues to cooperate with the EPA's civil enforcement process. Future costs related to the Dan River release, including future state or federal civil enforcement proceedings, future regulatory directives, natural resources damages, future claims or litigation and long-term environmental impact costs, cannot be reasonably estimated at this time. The North Carolina Department of Environmental Quality (NCDEQ) has historically assessed Duke Energy Carolinas and Duke Energy Progress with Notice of Violations (NOV) for violations that were most often resolved through satisfactory corrective actions and minor, if any, fines or penalties. Subsequent to the Dan River ash release, Duke Energy Carolinas and Duke Energy Progress have been served with a higher level of NOVs, including assessed penalties for violations at L.V. Sutton Combined Cycle Plant (Sutton) and Dan River Steam Station. Duke Energy Carolinas and Duke Energy Progress cannot predict whether the NCDEQ will assess future penalties related to existing unresolved NOVs and if such penalties would be material. See "NCDEQ Notices of Violation" section below for additional discussion. LITIGATION Duke Energy Duke Energy no longer has exposure to litigation matters related to the International Disposal Group as a result of the divestiture of the business in December 2016. See Note 2 for additional information related to the sale of International Energy. Ash Basin Shareholder Derivative Litigation Five shareholder derivative lawsuits were filed in Delaware Chancery Court relating to the release at Dan River and to the management of Duke Energy’s ash basins. On October 31, 2014, the five lawsuits were consolidated in a single proceeding titled In Re Duke Energy Corporation Coal Ash Derivative Litigation . On December 2, 2014, plaintiffs filed a Corrected Verified Consolidated Shareholder Derivative Complaint (Consolidated Complaint). The Consolidated Complaint names as defendants several current and former Duke Energy officers and directors (collectively, the “Duke Energy Defendants”). Duke Energy is named as a nominal defendant. The Consolidated Complaint alleges the Duke Energy Defendants breached their fiduciary duties by failing to adequately oversee Duke Energy’s ash basins and that these breaches of fiduciary duty may have contributed to the incident at Dan River and continued thereafter. The lawsuit also asserts claims against the Duke Energy Defendants for corporate waste (relating to the money Duke Energy has spent and will spend as a result of the fines, penalties and coal ash removal) and unjust enrichment (relating to the compensation and director remuneration that was received despite these alleged breaches of fiduciary duty). The lawsuit seeks both injunctive relief against Duke Energy and restitution from the Duke Energy Defendants. On January 21, 2015, the Duke Energy Defendants filed a Motion to Stay, which the court granted. The stay was lifted on March 24, 2016, after which plaintiffs filed an Amended Verified Consolidated Shareholder Derivative Complaint (Amended Complaint) making the same allegations as in the Consolidated Complaint. The Duke Energy Defendants filed a motion to dismiss the Amended Complaint on June 21, 2016, which was granted by the Court on December 14, 2016. Plaintiffs filed an appeal to the Delaware Supreme Court on January 9, 2017. Oral argument was held on September 27, 2017. On December 15, 2017, the Delaware Supreme Court affirmed the Chancery Court's order of dismissal. In addition to the above derivative complaints, in 2014, Duke Energy received two shareholder litigation demand letters. The letters alleged that the members of the Board of Directors and certain officers breached their fiduciary duties by allowing the company to illegally dispose of and store coal ash pollutants. One of the letters also alleged a breach of fiduciary duty in the decision-making relating to the leadership changes following the close of the Progress Energy merger in July 2012. By letter dated September 4, 2015, attorneys for the shareholders were informed that, on the recommendation of the Demand Review Committee formed to consider such matters, the Board of Directors concluded not to pursue potential claims against individuals. One of the shareholders, Mitchell Pinsly, sent a formal demand for records and Duke Energy has responded to this request. There was no follow-up after the records were provided; therefore, this matter has been resolved. On October 30, 2015, shareholder Saul Bresalier filed a shareholder derivative complaint (Bresalier Complaint) in the U.S. District Court for the District of Delaware. The lawsuit alleges that several current and former Duke Energy officers and directors (Bresalier Defendants) breached their fiduciary duties in connection with coal ash environmental issues, the post-merger change in Chief Executive Officer (CEO) and oversight of political contributions. Duke Energy is named as a nominal defendant. The Bresalier Complaint contends that the Demand Review Committee failed to appropriately consider the shareholder’s earlier demand for litigation and improperly decided not to pursue claims against the Bresalier Defendants. On March 30, 2017, the court granted Defendants’ Motion to Dismiss on the claims relating to coal ash environmental issues and political contributions. As discussed below, a settlement agreement was approved for the merger-related claims in the Bresalier Complaint, and those claims were dismissed. On September 8, 2017, Bresalier filed a notice of appeal to the U.S. Court of Appeals for the Third Circuit (Third Circuit Court) challenging the dismissal of his coal ash and political contribution claims. On January 19 2018, Bresalier filed a stipulation of dismissal, closing this case. Progress Energy Merger Shareholder Litigation Duke Energy, the 11 members of the Board of Directors who were also members of the pre-merger Board of Directors (Legacy Duke Energy Directors) and certain Duke Energy officers were defendants in a purported securities class-action lawsuit (Nieman v. Duke Energy Corporation, et al) . This lawsuit consolidated three lawsuits originally filed in July 2012. The plaintiffs alleged federal Securities Act of 1933 and Securities Exchange Act of 1934 (Exchange Act) claims based on allegations of materially false and misleading representations and omissions in the Registration Statement filed on July 7, 2011, and purportedly incorporated into other documents, all in connection with the post-merger change in CEO. On August 15, 2014, the parties reached an agreement in principle to settle the litigation. On March 10, 2015, the parties filed a Stipulation of Settlement and a Motion for Preliminary Approval of the Settlement. Under the terms of the agreement, Duke Energy agreed to pay $146 million to settle the claim. On April 22, 2015, Duke Energy made a payment of $25 million into the settlement escrow account. The remainder of $121 million was paid by insurers into the settlement escrow account. The final order approving the settlement was issued on November 2, 2015, thus closing the matter. On May 31, 2013, the Delaware Chancery Court consolidated four shareholder derivative lawsuits filed in 2012. The Court also appointed a lead plaintiff and counsel for plaintiffs and designated the case as In Re Duke Energy Corporation Derivative Litigation (Merger Chancery Litigation). The lawsuit names as defendants the Legacy Duke Energy Directors. Duke Energy is named as a nominal defendant. The case alleges claims for breach of fiduciary duties of loyalty and care in connection with the post-merger change in CEO. Two shareholder Derivative Complaints, filed in 2012 in federal district court in Delaware, were consolidated as Tansey v. Rogers, et al. The case alleges claims against the Legacy Duke Energy Directors for breach of fiduciary duty and waste of corporate assets, as well as claims under Section 14(a) and 20(a) of the Exchange Act. Duke Energy is named as a nominal defendant. On December 21, 2015, Plaintiff filed a Consolidated Amended Complaint asserting the same claims contained in the original complaints. The Legacy Duke Energy Directors have reached an agreement-in-principle to settle the Merger Chancery Litigation, conditioned on dismissal as well, of the Tansey v. Rogers, et al case and the merger related claims in the Bresalier Complaint discussed above, which was approved by the Delaware Chancery Court on July 13, 2017. The entire settlement amount was funded by insurance. The settlement amount, less court-approved attorney fees, totaled $20 million and was paid to Duke Energy in 2017. Duke Energy Carolinas and Duke Energy Progress Coal Ash Insurance Coverage Litigation In March 2017, Duke Energy Carolinas and Duke Energy Progress filed a civil action in North Carolina Superior Court against various insurance providers. The lawsuit seeks payment for coal ash-related liabilities covered by third-party liability insurance policies. The insurance policies were issued between 1971 and 1986 and provide third-party liability insurance for property damage. The civil action seeks damages for breach of contract and indemnification for costs arising from the Coal Ash Act and the EPA CCR rule at 15 coal-fired plants in North Carolina and South Carolina. Duke Energy Carolinas and Duke Energy Progress cannot predict the outcome of this matter. NCDEQ Notice of Violation On February 8, 2016, the NCDEQ assessed a penalty of approximately $6.8 million , including enforcement costs, against Duke Energy Carolinas related to stormwater pipes and associated discharges at the Dan River Steam Station. Duke Energy Carolinas recorded a charge in December 2015 for this penalty. In March 2016, Duke Energy Carolinas filed an appeal of this penalty. On September 23, 2016, Duke Energy Carolinas entered into a settlement agreement with the NCDEQ, without admission of liability, under which Duke Energy Carolinas agreed to a payment of $6 million to resolve allegations underlying the asserted civil penalty related to the Dan River coal ash release and a March 4, 2016, NOV alleging unpermitted discharges at the facility. NCDEQ State Enforcement Actions In the first quarter of 2013, Southern Environmental Law Center (SELC) sent notices of intent to sue Duke Energy Carolinas and Duke Energy Progress related to alleged Clean Water Act (CWA) violations from coal ash basins at two of their coal-fired power plants in North Carolina. The NCDEQ filed enforcement actions against Duke Energy Carolinas and Duke Energy Progress alleging violations of water discharge permits and North Carolina groundwater standards. The cases have been consolidated and are being heard before a single judge in the North Carolina Superior Court. On August 16, 2013, the NCDEQ filed an enforcement action against Duke Energy Carolinas and Duke Energy Progress related to their remaining plants in North Carolina alleging violations of the CWA and violations of the North Carolina groundwater standards. Both of these cases have been assigned to the judge handling the enforcement actions discussed above. SELC is representing several environmental groups who have been permitted to intervene in these cases. The court issued orders in 2016 granting Motions for Partial Summary Judgment for seven of the 14 North Carolina plants with coal ash basins named in the enforcement actions. On February 13, 2017, the court issued an order denying motions for partial summary judgment brought by both the environmental groups and Duke Energy Carolinas and Duke Energy Progress for the remaining seven plants. On March 15, 2017, Duke Energy Carolinas and Duke Energy Progress filed a Notice of Appeal to challenge the trial court’s order. The parties were unable to reach an agreement at mediation in April 2017. The parties submitted briefs to the court on remaining issues to be tried and a ruling is pending. On August 22, 2017, Duke Energy Carolinas and Duke Energy Progress filed a Petition for Discretionary Review, requesting the North Carolina Supreme Court to accept the appeal. On August 24, 2017, SELC filed a motion to dismiss the appeal. Duke Energy Carolinas' and Duke Energy Progress’ opening appellate briefs were filed on October 12, 2017, and briefing is now complete. Argument was held on February 8, 2018. It is not possible to predict any liability or estimate any damages Duke Energy Carolinas or Duke Energy Progress might incur in connection with these matters. Federal Citizens Suits On June 13, 2016, the Roanoke River Basin Association (RRBA) filed a federal citizen suit in the Middle District of North Carolina alleging unpermitted discharges to surface water and groundwater violations at the Mayo Plant. On August 19, 2016, Duke Energy Progress filed a Motion to Dismiss. On April 26, 2017, the court entered an order dismissing four of the claims in the federal citizen suit. Two claims relating to alleged violations of National Pollutant Discharge Elimination System (NPDES) permit provisions survived the motion to dismiss, and Duke Energy Progress filed its response on May 10, 2017. The parties are engaged in pre-trial discovery. Trial has been scheduled for July 9, 2018. On March 16, 2017, RRBA served Duke Energy Progress with a Notice of Intent to Sue under the CWA for alleged violations of effluent standards and limitations at the Roxboro Plant. In anticipation of litigation, Duke Energy Progress filed a Complaint for Declaratory Relief in the U.S. District Court for the Western District of Virginia on May 11, 2017, which was subsequently dismissed. On May 16, 2017, RRBA filed a federal citizen suit in the U.S. District Court for the Middle District of North Carolina which asserts two claims relating to alleged violations of NPDES permit provisions and one claim relating to the use of nearby water bodies. The parties are engaged in pre-trial discovery. Trial has been scheduled for October 1, 2018. On June 20, 2017, RRBA filed a federal citizen suit in the U.S. District Court for the Middle District of North Carolina challenging the closure plans at the Mayo Plant under the EPA CCR Rule. Duke Energy Progress filed a motion to dismiss, which was argued on January 30, 2018. On August 2, 2017, RRBA filed a federal citizen suit in the U.S. District Court for the Middle District of North Carolina challenging the closure plans at the Roxboro Plant under the EPA CCR Rule. Duke Energy Progress filed a motion to dismiss on October 2, 2017. On December 6, 2017, various parties filed a federal citizen suit in the U.S. District Court for the Middle District of North Carolina for alleged violations at Duke Energy Carolinas' Belews Creek Steam Station (Belews Creek) under the CWA. Duke Energy Carolinas filed a motion to dismiss on February 5, 2018. It is not possible to predict whether Duke Energy Carolinas or Duke Energy Progress will incur any liability or to estimate the damages, if any, they might incur in connection with these matters. Five previously filed cases involving the Riverbend, Cape Fear, H.F. Lee, Sutton and Buck plants have been dismissed or settled during 2016. Groundwater Contamination Claims Beginning in May 2015, a number of residents living in the vicinity of the North Carolina facilities with ash basins received letters from the NCDEQ advising them not to drink water from the private wells on their land tested by the NCDEQ as the samples were found to have certain substances at levels higher than the criteria set by the North Carolina Department of Health and Human Services (DHHS). Results of Comprehensive Site Assessments (CSAs) testing performed by Duke Energy under the Coal Ash Act have been consistent with historical data provided to state regulators over many years. The DHHS and NCDEQ sent follow-up letters on October 15, 2015, to residents near coal ash basins who have had their wells tested, stating that private well samplings at a considerable distance from coal ash basins, as well as some municipal water supplies, contain similar levels of vanadium and hexavalent chromium, which led investigators to believe these constituents are naturally occurring. In March 2016, DHHS rescinded the advisories. Duke Energy Carolinas and Duke Energy Progress have received formal demand letters from residents near Duke Energy Carolinas' and Duke Energy Progress' coal ash basins. The residents claim damages for nuisance and diminution in property value, among other things. The parties held three days of mediation discussions which ended at impasse. On January 6, 2017, Duke Energy Carolinas and Duke Energy Progress received the plaintiffs' notice of their intent to file suits should the matter not settle. The NCDEQ preliminarily approved Duke Energy’s permanent water solution plans on January 13, 2017, and as a result shortly thereafter, Duke Energy issued a press release, providing additional details regarding the homeowner compensation package. This package consists of three components: (i) a $5,000 goodwill payment to each eligible well owner to support the transition to a new water supply, (ii) where a public water supply is available and selected by the eligible well owner, a stipend to cover 25 years of water bills and (iii) the Property Value Protection Plan. The Property Value Protection Plan is a program offered by Duke Energy designed to guarantee eligible plant neighbors the fair market value of their residential property should they decide to sell their property during the time that the plan is offered. Duke Energy Carolinas and Duke Energy Progress recognized reserves of $19 million and $4 million , respectively. On August 23, 2017, a class-action suit was filed in Wake County Superior Court, North Carolina, against Duke Energy Carolinas and Duke Energy Progress on behalf of certain property owners living near coal ash impoundments at Allen, Asheville, Belews Creek, Buck, Cliffside, Lee, Marshall, Mayo and Roxboro. The class is defined as those who are well-eligible under the Coal Ash Act or those to whom Duke Energy has promised a permanent replacement water supply and seeks declaratory and injunctive relief, along with compensatory damages. Plaintiffs allege that Duke Energy’s improper maintenance of coal ash impoundments caused harm, particularly through groundwater contamination. Despite NCDEQ’s preliminary approval, Plaintiffs contend that Duke Energy’s proposed permanent water solutions plan fails to comply with the Coal Ash Act. On September 28, 2017, Duke Energy Carolinas and Duke Energy Progress filed a Motion to Dismiss and Motion to Strike the class designation. The parties entered into a Settlement Agreement on January 24, 2018, which resulted in the dismissal of the underlying class action on January 25, 2018. On September 14, 2017, a complaint was filed against Duke Energy Progress in New Hanover County Superior Court by a group of homeowners residing approximately 1 mile from Duke Energy Progress' Sutton Steam Plant. The homeowners allege that coal ash constituents have been migrating from ash impoundments at Sutton into their groundwater for decades and that in 2015, Duke Energy Progress discovered these releases of coal ash, but failed to notify any officials or neighbors and failed to take remedial action. The homeowners claim unspecified physical and mental injuries as a result of consuming their well water and seek actual damages for personal injury, medical monitoring and punitive damages. Duke Energy filed its Motion to Dismiss on October 27, 2017, and the hearing is schedule

Debt and Credit Facilities

Debt and Credit Facilities	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Debt and Credit Facilities	DEBT AND CREDIT FACILITIES Summary of Debt and Related Terms The following tables summarize outstanding debt. December 31, 2017 Weighted Average Duke Duke Duke Duke Duke Interest Duke Energy Progress Energy Energy Energy Energy (in millions) Rate Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Unsecured debt, maturing 2018-2073 4.17 % $ 20,409 $ 1,150 $ 3,950 $ — $ 550 $ 900 $ 411 $ 2,050 Secured debt, maturing 2018-2037 3.15 % 4,458 450 1,757 300 1,457 — — — First mortgage bonds, maturing 2018-2047 (a) 4.51 % 23,529 7,959 11,801 6,776 5,025 1,100 2,669 — Capital leases, maturing 2018-2051 (b) 4.55 % 1,000 61 269 139 129 5 11 — Tax-exempt bonds, maturing 2019-2041 (c) 3.23 % 941 243 48 48 — 77 572 — Notes payable and commercial paper (d) 1.57 % 2,788 — — — — — — — Money pool/intercompany borrowings — 404 955 390 — 54 311 364 Fair value hedge carrying value adjustment 6 6 — — — — — — Unamortized debt discount and premium, net (e) 1,582 (19 ) (30 ) (16 ) (10 ) (33 ) (9 ) (1 ) Unamortized debt issuance costs (f) (271 ) (47 ) (108 ) (40 ) (56 ) (7 ) (21 ) (12 ) Total debt 4.09 % $ 54,442 $ 10,207 $ 18,642 $ 7,597 $ 7,095 $ 2,096 $ 3,944 $ 2,401 Short-term notes payable and commercial paper (2,163 ) — — — — — — — Short-term money pool/intercompany borrowings — (104 ) (805 ) (240 ) — (29 ) (161 ) (364 ) Current maturities of long-term debt (g) (3,244 ) (1,205 ) (771 ) (3 ) (768 ) (3 ) (3 ) (250 ) Total long-term debt (g) $ 49,035 $ 8,898 $ 17,066 $ 7,354 $ 6,327 $ 2,064 $ 3,780 $ 1,787 (a) Substantially all electric utility property is mortgaged under mortgage bond indentures. (b) Duke Energy includes $81 million and $603 million of capital lease purchase accounting adjustments related to Duke Energy Progress and Duke Energy Florida, respectively, related to power purchase agreements that are not accounted for as capital leases in their respective financial statements because of grandfathering provisions in GAAP. (c) Substantially all tax-exempt bonds are secured by first mortgage bonds or letters of credit. (d) Includes $625 million that was classified as Long-Term Debt on the Consolidated Balance Sheets due to the existence of long-term credit facilities that backstop these commercial paper balances, along with Duke Energy’s ability and intent to refinance these balances on a long-term basis. The weighted average days to maturity for Duke Energy's commercial paper program was 14 days. (e) Duke Energy includes $1,509 million and $176 million in purchase accounting adjustments related to Progress Energy and Piedmont, respectively. (f) Duke Energy includes $47 million in purchase accounting adjustments primarily related to the merger with Progress Energy. (g) Refer to Note 17 for additional information on amounts from consolidated VIEs. December 31, 2016 Weighted Average Duke Duke Duke Duke Duke Interest Duke Energy Progress Energy Energy Energy Energy (in millions) Rate Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Unsecured debt, maturing 2017-2073 4.30 % $ 17,812 $ 1,150 $ 3,551 $ — $ 150 $ 810 $ 415 $ 1,835 Secured debt, maturing 2017-2037 2.60 % 3,909 425 1,819 300 1,519 — — — First mortgage bonds, maturing 2017-2046 (a) 4.61 % 21,879 7,410 10,800 6,425 4,375 1,000 2,669 — Capital leases, maturing 2018-2051 (b) 4.48 % 1,100 22 285 142 143 7 11 — Tax-exempt bonds, maturing 2017-2041 (c) 2.84 % 1,053 355 48 48 — 77 572 — Notes payable and commercial paper (d) 1.01 % 3,112 — — — — — — — Money pool/intercompany borrowings (e) — 300 1,902 150 297 41 150 — Fair value hedge carrying value adjustment 6 6 — — — — — — Unamortized debt discount and premium, net (f) 1,753 (20 ) (31 ) (16 ) (10 ) (28 ) (9 ) (1 ) Unamortized debt issuance costs (g) (242 ) (45 ) (104 ) (38 ) (52 ) (7 ) (22 ) (13 ) Total debt 4.07 % $ 50,382 $ 9,603 $ 18,270 $ 7,011 $ 6,422 $ 1,900 $ 3,786 $ 1,821 Short-term notes payable and commercial paper (2,487 ) — — — — — — — Short-term money pool/intercompany borrowings — — (729 ) — (297 ) (16 ) — — Current maturities of long-term debt (h) (2,319 ) (116 ) (778 ) (452 ) (326 ) (1 ) (3 ) (35 ) Total long-term debt (h) $ 45,576 $ 9,487 $ 16,763 $ 6,559 $ 5,799 $ 1,883 $ 3,783 $ 1,786 (a) Substantially all electric utility property is mortgaged under mortgage bond indentures. (b) Duke Energy includes $98 million and $670 million of capital lease purchase accounting adjustments related to Duke Energy Progress and Duke Energy Florida, respectively, related to power purchase agreements that are not accounted for as capital leases in their respective financial statements because of grandfathering provisions in GAAP. (c) Substantially all tax-exempt bonds are secured by first mortgage bonds or letters of credit. (d) Includes $625 million that was classified as Long-Term Debt on the Consolidated Balance Sheets due to the existence of long-term credit facilities that backstop these commercial paper balances, along with Duke Energy’s ability and intent to refinance these balances on a long-term basis. The weighted average days to maturity for Duke Energy and Piedmont's commercial paper programs were 14 days and eight days, respectively. (e) Progress Energy amount includes a $1 billion intercompany loan related to the sale of the International Disposal Group. See Note 2 for further discussion of the sale. (f) Duke Energy includes $1,653 million and $197 million purchase accounting adjustments related to the mergers with Progress Energy and Piedmont, respectively. (g) Duke Energy includes $53 million in purchase accounting adjustments primarily related to the merger with Progress Energy. (h) Refer to Note 17 for additional information on amounts from consolidated VIEs. Current Maturities of Long-Term Debt The following table shows the significant components of Current maturities of Long-Term Debt on the Consolidated Balance Sheets. The Duke Energy Registrants currently anticipate satisfying these obligations with cash on hand and proceeds from additional borrowings. (in millions) Maturity Date Interest Rate December 31, 2017 Unsecured Debt Duke Energy (Parent) June 2018 6.250 % $ 250 Duke Energy (Parent) June 2018 2.100 % 500 Piedmont December 2018 2.286 % (b) 250 First Mortgage Bonds Duke Energy Carolinas January 2018 5.250 % 400 Duke Energy Carolinas April 2018 5.100 % 300 Duke Energy Florida June 2018 5.650 % 500 Duke Energy Carolinas November 2018 7.000 % 500 Other (a) 544 Current maturities of long-term debt $ 3,244 (a) Includes capital lease obligations, amortizing debt and small bullet maturities. (b) Debt has a floating interest rate. Maturities and Call Options The following table shows the annual maturities of long-term debt for the next five years and thereafter. Amounts presented exclude short-term notes payable and commercial paper and money pool borrowings for the Subsidiary Registrants. December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy (a) Carolinas Energy Progress Florida Ohio Indiana Piedmont 2018 $ 3,244 $ 1,205 $ 771 $ 3 $ 768 $ 3 $ 3 $ 250 2019 3,563 6 2,191 903 490 548 61 — 2020 3,699 906 871 304 568 — 502 — 2021 3,760 502 1,472 602 371 48 69 159 2022 3,010 302 1,176 653 74 23 243 — Thereafter 33,271 7,182 11,356 4,892 4,824 1,445 2,905 1,628 Total long-term debt, including current maturities $ 50,547 $ 10,103 $ 17,837 $ 7,357 $ 7,095 $ 2,067 $ 3,783 $ 2,037 (a) Excludes $1,732 million in purchase accounting adjustments related to the Progress Energy merger and the Piedmont acquisition. The Duke Energy Registrants have the ability under certain debt facilities to call and repay the obligation prior to its scheduled maturity. Therefore, the actual timing of future cash repayments could be materially different than as presented above. Short-Term Obligations Classified as Long-Term Debt Tax-exempt bonds that may be put to the Duke Energy Registrants at the option of the holder and certain commercial paper issuances and money pool borrowings are classified as Long-Term Debt on the Consolidated Balance Sheets. These tax-exempt bonds, commercial paper issuances and money pool borrowings, which are short-term obligations by nature, are classified as long term due to Duke Energy’s intent and ability to utilize such borrowings as long-term financing. As Duke Energy’s Master Credit Facility and other bilateral letter of credit agreements have non-cancelable terms in excess of one year as of the balance sheet date, Duke Energy has the ability to refinance these short-term obligations on a long-term basis. The following tables show short-term obligations classified as long-term debt. December 31, 2017 Duke Duke Duke Duke Duke Energy Energy Energy Energy (in millions) Energy Carolinas Progress Ohio Indiana Tax-exempt bonds $ 312 $ — $ — $ 27 $ 285 Commercial paper (a) 625 300 150 25 150 Total $ 937 $ 300 $ 150 $ 52 $ 435 December 31, 2016 Duke Duke Duke Duke Duke Energy Energy Energy Energy (in millions) Energy Carolinas Progress Ohio Indiana Tax-exempt bonds $ 347 $ 35 $ — $ 27 $ 285 Commercial paper (a) 625 300 150 25 150 Total $ 972 $ 335 $ 150 $ 52 $ 435 (a) Progress Energy amounts are equal to Duke Energy Progress amounts. Summary of Significant Debt Issuances The following tables summarize significant debt issuances (in millions). Year Ended December 31, 2017 Duke Duke Duke Duke Duke Maturity Interest Duke Energy Energy Energy Energy Energy Issuance Date Date Rate Energy (Parent) Carolinas Progress Florida Ohio Unsecured Debt April 2017 (a) April 2025 3.364 % $ 420 $ 420 $ — $ — $ — $ — June 2017 (b) June 2020 2.100 % 330 330 — — — — August 2017 (c) August 2022 2.400 % 500 500 — — — — August 2017 (c) August 2027 3.150 % 750 750 — — — — August 2017 (c) August 2047 3.950 % 500 500 — — — — December 2017 (d) December 2019 (k) 2.100 % 400 — — — 400 — Secured Debt February 2017 (e) June 2034 4.120 % 587 — — — — — August 2017 (f) December 2036 4.110 % 233 — — — — — First Mortgage Bonds January 2017 (g) January 2020 1.850 % 250 — — — 250 — January 2017 (g) January 2027 3.200 % 650 — — — 650 — March 2017 (h) June 2046 3.700 % 100 — — — — 100 September 2017 (i) September 2020 1.500 % (l) 300 — — 300 — — September 2017 (i) September 2047 3.600 % 500 — — 500 — — November 2017 (j) December 2047 3.700 % 550 — 550 — — — Total issuances $ 6,070 $ 2,500 $ 550 $ 800 $ 1,300 $ 100 (a) Proceeds were used to refinance $400 million of unsecured debt at maturity and to repay a portion of outstanding commercial paper. (b) Debt issued to repay a portion of outstanding commercial paper. (c) Debt issued to repay at maturity $700 million of unsecured debt, to repay outstanding commercial paper and for general corporate purposes. (d) Debt issued to fund storm restoration costs related to Hurricane Irma and for general corporate purposes. (e) Portfolio financing of four Texas and Oklahoma wind facilities. Duke Energy pledged substantially all of the assets of these wind facilities and is nonrecourse to Duke Energy. Proceeds were used to reimburse Duke Energy for a portion of previously funded construction expenditures. (f) Portfolio financing of eight solar facilities located in California, Colorado and New Mexico. Duke Energy pledged substantially all of the assets of these solar facilities and is nonrecourse to Duke Energy. Proceeds were used to reimburse Duke Energy for a portion of previously funded construction expenditures. (g) Debt issued to fund capital expenditures for ongoing construction and capital maintenance, to repay a $250 million aggregate principal amount of bonds at maturity and for general corporate purposes. (h) Proceeds were used to fund capital expenditures for ongoing construction, capital maintenance and for general corporate purposes. (i) Debt issued to repay at maturity a $200 million aggregate principal amount of bonds at maturity, pay down intercompany short-term debt and for general corporate purposes, including capital expenditures. (j) Debt issued to refinance $400 million aggregate principal amount of bonds due January 2018, pay down intercompany short-term debt and for general corporate purposes. (k) Principal balance will be repaid in equal quarterly installments beginning in March 2018. (l) Debt issuance has a floating interest rate. Year Ended December 31, 2016 Duke Duke Duke Duke Duke Duke Maturity Interest Duke Energy Energy Energy Energy Energy Energy Issuance Date Date Rate Energy (Parent) Carolinas Progress Florida Ohio Indiana Unsecured Debt April 2016 (a) April 2023 2.875 % $ 350 $ 350 $ — $ — $ — $ — $ — August 2016 (b) September 2021 1.800 % 750 750 — — — — — August 2016 (b) September 2026 2.650 % 1,500 1,500 — — — — — August 2016 (b) September 2046 3.750 % 1,500 1,500 — — — — — Secured Debt June 2016 (c) March 2020 1.196 % 183 — — — 183 — — June 2016 (c) September 2022 1.731 % 150 — — — 150 — — June 2016 (c) September 2029 2.538 % 436 — — — 436 — — June 2016 (c) March 2033 2.858 % 250 — — — 250 — — June 2016 (c) September 2036 3.112 % 275 — — — 275 — — August 2016 (d) June 2034 2.747 % (i) 228 — — — — — — August 2016 (d) June 2020 2.747 % (i) 105 — — — — — — First Mortgage Bonds March 2016 (e) March 2023 2.500 % 500 — 500 — — — — March 2016 (e) March 2046 3.875 % 500 — 500 — — — — May 2016 (f) May 2046 3.750 % 500 — — — — — 500 June 2016 (e) June 2046 3.700 % 250 — — — — 250 — September 2016 (g) October 2046 3.400 % 600 — — — 600 — — September 2016 (e) October 2046 3.700 % 450 — — 450 — — — November 2016 (h) December 2046 2.950 % 600 — 600 — — — — Total issuances $ 9,127 $ 4,100 $ 1,600 $ 450 $ 1,894 $ 250 $ 500 (a) Proceeds were used to pay down outstanding commercial paper and for general corporate purposes. (b) Proceeds were used to finance a portion of the Piedmont acquisition. The $4.9 billion Bridge Facility was terminated following the issuance of this debt. See Note 2 for additional information on the Piedmont acquisition. (c) DEFPF issued nuclear-asset recovery bonds and used the proceeds to acquire nuclear-asset recovery property from its parent, Duke Energy Florida. The nuclear-asset recovery bonds are payable only from and secured by the nuclear asset-recovery property. DEFPF is consolidated for financial reporting purposes; however, the nuclear asset-recovery bonds do not constitute a debt, liability or other legal obligation of, or interest in, Duke Energy Florida or any of its affiliates other than DEFPF. The assets of DEFPF, including the nuclear-asset recovery property, are not available to pay creditors of Duke Energy Florida or any of its affiliates. Duke Energy Florida used the proceeds from the sale to repay short-term borrowings under the intercompany money pool borrowing arrangement and make an equity distribution of $649 million to the ultimate parent, Duke Energy (Parent), which repaid short-term borrowings. The nuclear-asset recovery bonds are sequential pay amortizing bonds. The maturity date above represents the scheduled final maturity date for the bonds. See Notes 4 and 17 for additional information. (d) Emerald State Solar, LLC, an indirect wholly owned subsidiary of Duke Energy entered into portfolio financing of approximately 22 North Carolina solar facilities. Tranche A of $228 million is secured by substantially all of the assets of the solar facilities and is nonrecourse to Duke Energy. Tranche B of $105 million is secured by an Equity Contribution Agreement with Duke Energy. Proceeds were used to reimburse Duke Energy for a portion of previously funded construction expenditures related to the Emerald State Solar, LLC portfolio. The initial interest rate on the loans was six months London Interbank Offered Rate (LIBOR) plus an applicable margin of 1.75 percent plus a 0.125 percent increase every three years thereafter. In connection with this debt issuance, Emerald State Solar, LLC entered into two interest rate swaps to convert the substantial majority of the loan interest payments from variable rates to fixed rates of approximately 1.81 percent for Tranche A and 1.38 percent for Tranche B, plus the applicable margin. See Note 14 for further information on the notional amounts of the interest rate swaps. (e) Proceeds were used to fund capital expenditures for ongoing construction, capital maintenance and for general corporate purposes. (f) Proceeds were used to repay $325 million of unsecured debt due June 2016, $150 million of first mortgage bonds due July 2016 and for general corporate purposes. (g) Proceeds were used to fund capital expenditures for ongoing construction, capital maintenance, to repay short-term borrowings under the intercompany money pool borrowing arrangement and for general corporate purposes. (h) Proceeds were used to repay at maturity $350 million aggregate principal amount of certain bonds due December 2016, as well as to fund capital expenditures for ongoing construction and capital maintenance and for general corporate purposes. (i) Debt issuance has a floating interest rate. In July 2016, Piedmont issued $300 million unsecured notes maturing in November 2046 with an interest rate of 3.64% . Piedmont has the option to redeem all or part of the notes before May 1, 2046, at a redemption price equal to the greater of a) 100% of the principal amount of the notes to be redeemed, and b) the sum of the present values of the remaining scheduled payments of principal and interest on the notes to be redeemed, discounted to the date of redemption on a semi-annual basis at the Treasury Rate as defined in the indenture, as supplemented, plus 25 basis points and any accrued and unpaid interest to the date of redemption. Piedmont has the option to redeem all or part of the notes on or after May 1, 2046, at 100% of the principal amounts plus any accrued and unpaid interest to the date of redemption. Piedmont used the proceeds to fund capital expenditures, to repay short-term borrowings under Piedmont's commercial paper program and for general corporate purposes. Available Credit Facilities In March 2017, Duke Energy amended its Master Credit Facility to increase its capacity from $7.5 billion to $8 billion , and to extend the termination date of the facility from January 30, 2020, to March 16, 2022. The amendment also added Piedmont as a borrower within the Master Credit Facility. Piedmont's separate $850 million credit facility was terminated in connection with the amendment. With the amendment, the Duke Energy Registrants, excluding Progress Energy (Parent), have borrowing capacity under the Master Credit Facility up to specified sublimits for each borrower. Duke Energy has the unilateral ability at any time to increase or decrease the borrowing sublimits of each borrower, subject to a maximum sublimit for each borrower. The amount available under the Master Credit Facility has been reduced to backstop issuances of commercial paper, certain letters of credit and variable-rate demand tax-exempt bonds that may be put to the Duke Energy Registrants at the option of the holder. Duke Energy Carolinas and Duke Energy Progress are also required to each maintain $250 million of available capacity under the Master Credit Facility as security to meet obligations under plea agreements reached with the U.S. Department of Justice in 2015 related to violations at North Carolina facilities with ash basins. In January 2018, Duke Energy further amended its Master Credit Facility with consenting lenders to extend $7.65 billion of our existing $8 billion Master Credit Facility by one year to March 16, 2023 . The table below includes the current borrowing sublimits and available capacity under these credit facilities. December 31, 2017 Duke Duke Duke Duke Duke Duke Duke Energy Energy Energy Energy Energy Energy (in millions) Energy (Parent) Carolinas Progress Florida Ohio Indiana Piedmont Facility size (a) $ 8,000 $ 2,850 $ 1,350 $ 1,250 $ 800 $ 450 $ 600 $ 700 Reduction to backstop issuances Commercial paper (b) (1,799 ) (561 ) (371 ) (314 ) — (45 ) (260 ) (248 ) Outstanding letters of credit (63 ) (54 ) (4 ) (2 ) (1 ) — — (2 ) Tax-exempt bonds (81 ) — — — — — (81 ) — Coal ash set-aside (500 ) — (250 ) (250 ) — — — — Available capacity $ 5,557 $ 2,235 $ 725 $ 684 $ 799 $ 405 $ 259 $ 450 (a) Represents the sublimit of each borrower. (b) Duke Energy issued $625 million of commercial paper and loaned the proceeds through the money pool to Duke Energy Carolinas, Duke Energy Progress, Duke Energy Ohio and Duke Energy Indiana. The balances are classified as Long-Term Debt Payable to Affiliated Companies in the Consolidated Balance Sheets. Three-Year Revolving Credit Facility In June 2017, Duke Energy (Parent) entered into a three -year $1.0 billion revolving credit facility (the Three Year Revolver). Borrowings under this facility will be used for general corporate purposes. As of December 31, 2017, $500 million has been drawn under the Three Year Revolver. This balance is classified as Long-Term Debt on Duke Energy's Consolidated Balance Sheets. Any undrawn commitments can be drawn, and borrowings can be prepaid, at any time throughout the term of the facility. The terms and conditions of the Three Year Revolver are generally consistent with those governing Duke Energy's Master Credit Facility. Piedmont Term Loan Facility In June 2017, Piedmont entered into an 18 -month term loan facility with commitments totaling $250 million (the Piedmont Term Loan). Borrowings under the facility will be used for general corporate purposes. As of December 31, 2017 , the entire $250 million has been drawn under the Piedmont Term Loan. This balance is classified as Long-Term Debt on Piedmont's Consolidated Balance Sheets. The terms and conditions of the Piedmont Term Loan are generally consistent with those governing Duke Energy's Master Credit Facility. Other Debt Matters In September 2016, Duke Energy filed a Registration statement (Form S-3) with the SEC. Under this Form S-3, which is uncapped, the Duke Energy Registrants, excluding Progress Energy, may issue debt and other securities in the future at amounts, prices and with terms to be determined at the time of future offerings. The registration statement was filed to replace a similar prior filing upon expiration of its three-year term and also allows for the issuance of common stock by Duke Energy. Duke Energy has an effective Form S-3 with the SEC to sell up to $3 billion of variable denomination floating-rate demand notes, called PremierNotes. The Form S-3 states that no more than $1.5 billion of the notes will be outstanding at any particular time. The notes are offered on a continuous basis and bear interest at a floating rate per annum determined by the Duke Energy PremierNotes Committee, or its designee, on a weekly basis. The interest rate payable on notes held by an investor may vary based on the principal amount of the investment. The notes have no stated maturity date, are non-transferable and may be redeemed in whole or in part by Duke Energy or at the investor’s option at any time. The balance as of December 31, 2017 , and 2016 was $986 million and $1,090 million , respectively. The notes are short-term debt obligations of Duke Energy and are reflected as Notes payable and commercial paper on Duke Energy’s Consolidated Balance Sheets. In January 2017, Duke Energy amended its Form S-3 to add Piedmont as a registrant and included in the amendment a prospectus for Piedmont under which it may issue debt securities in the same manner as other Duke Energy Registrants. Duke Energy guaranteed debt issued by Duke Energy Carolinas of $650 million and $762 million , respectively, as of December 31, 2017 , and 2016 . Money Pool The Subsidiary Registrants, excluding Progress Energy, are eligible to receive support for their short-term borrowing needs through participation with Duke Energy and certain of its subsidiaries in a money pool arrangement. Under this arrangement, those companies with short-term funds may provide short-term loans to affiliates participating in this arrangement. The money pool is structured such that the Subsidiary Registrants, excluding Progress Energy, separately manage their cash needs and working capital requirements. Accordingly, there is no net settlement of receivables and payables between money pool participants. Duke Energy (Parent), may loan funds to its participating subsidiaries, but may not borrow funds through the money pool. Accordingly, as the money pool activity is between Duke Energy and its wholly owned subsidiaries, all money pool balances are eliminated within Duke Energy’s Consolidated Balance Sheets. Money pool receivable balances are reflected within Notes receivable from affiliated companies on the Subsidiary Registrants’ Consolidated Balance Sheets. Money pool payable balances are reflected within either Notes payable to affiliated companies or Long-Term Debt Payable to Affiliated Companies on the Subsidiary Registrants’ Consolidated Balance Sheets. Restrictive Debt Covenants The Duke Energy Registrants’ debt and credit agreements contain various financial and other covenants. Duke Energy's Master Credit Facility contains a covenant requiring the debt-to-total capitalization ratio not to exceed 65 percent for each borrower, excluding Piedmont, and 70 percent for Piedmont. Failure to meet those covenants beyond applicable grace periods could result in accelerated due dates and/or termination of the agreements. As of December 31, 2017 , each of the Duke Energy Registrants was in compliance with all covenants related to their debt agreements. In addition, some credit agreements may allow for acceleration of payments or termination of the agreements due to nonpayment, or acceleration of other significant indebtedness of the borrower or some of its subsidiaries. None of the debt or credit agreements contain material adverse change clauses. Other Loans As of December 31, 2017 , and 2016 , Duke Energy had loans outstanding of $701 million , including $38 million at Duke Energy Progress and $661 million , including $39 million at Duke Energy Progress, respectively, against the cash surrender value of life insurance policies it owns on the lives of its executives. The amounts outstanding were carried as a reduction of the related cash surrender value that is included in Other within Investments and Other Assets on the Consolidated Balance Sheets.

Guarantees and Indemnifications

Guarantees and Indemnifications	12 Months Ended
	Dec. 31, 2017
Guarantees [Abstract]
Guarantees and Indemnifications	GUARANTEES AND INDEMNIFICATIONS Duke Energy and Progress Energy have various financial and performance guarantees and indemnifications, which are issued in the normal course of business. As discussed below, these contracts include performance guarantees, stand-by letters of credit, debt guarantees, surety bonds and indemnifications. Duke Energy and Progress Energy enter into these arrangements to facilitate commercial transactions with third parties by enhancing the value of the transaction to the third party. At December 31, 2017 , Duke Energy and Progress Energy do not believe conditions are likely for significant performance under these guarantees. To the extent liabilities are incurred as a result of the activities covered by the guarantees, such liabilities are included on the accompanying Consolidated Balance Sheets. On January 2, 2007, Duke Energy completed the spin-off of its natural gas businesses to shareholders. Guarantees issued by Duke Energy or its affiliates, or assigned to Duke Energy prior to the spin-off, remained with Duke Energy subsequent to the spin-off. Guarantees issued by Spectra Energy Capital, LLC (Spectra Capital) or its affiliates prior to the spin-off remained with Spectra Capital subsequent to the spin-off, except for guarantees that were later assigned to Duke Energy. Duke Energy has indemnified Spectra Capital against any losses incurred under certain of the guarantee obligations that remain with Spectra Capital. At December 31, 2017 , the maximum potential amount of future payments associated with these guarantees was $205 million , the majority of which expires by 2028. Duke Energy has issued performance guarantees to customers and other third parties that guarantee the payment and performance of other parties, including certain non-wholly owned entities, as well as guarantees of debt of certain non-consolidated entities and less than wholly owned consolidated entities. If such entities were to default on payments or performance, Duke Energy would be required under the guarantees to make payments on the obligations of the less than wholly owned entity. The maximum potential amount of future payments required under these guarantees as of December 31, 2017 , was $326 million . Of this amount, $11 million relates to guarantees issued on behalf of less than wholly owned consolidated entities, with the remainder related to guarantees issued on behalf of third parties and unconsolidated affiliates of Duke Energy. Of the guarantees noted above, $281 million of the guarantees expire between 2019 and 2030, with the remaining performance guarantees having no contractual expiration. In October 2017, ACP executed a $3.4 billion revolving credit facility with a stated maturity date of October 2021. Duke Energy entered into a guarantee agreement to support its share of the ACP revolving credit facility. Duke Energy's maximum exposure to loss under the terms of the guarantee is limited to 47 percent of the outstanding borrowings under the credit facility, which was $312 million as of December 31, 2017 . Duke Energy has guaranteed certain issuers of surety bonds, obligating itself to make payment upon the failure of a wholly owned and former non-wholly owned entity to honor its obligations to a third party. Under these arrangements, Duke Energy has payment obligations that are triggered by a draw by the third party or customer due to the failure of the wholly owned or former non-wholly owned entity to perform according to the terms of its underlying contract. At December 31, 2017 , Duke Energy had guaranteed $81 million of outstanding surety bonds, most of which have no set expiration. Duke Energy uses bank-issued stand-by letters of credit to secure the performance of wholly owned and non-wholly owned entities to a third party or customer. Under these arrangements, Duke Energy has payment obligations to the issuing bank that are triggered by a draw by the third party or customer due to the failure of the wholly owned or non-wholly owned entity to perform according to the terms of its underlying contract. At December 31, 2017 , Duke Energy had issued a total of $449 million in letters of credit, which expire between 2018 and 2022. The unused amount under these letters of credit was $66 million . Duke Energy and Progress Energy have issued indemnifications for certain asset performance, legal, tax and environmental matters to third parties, including indemnifications made in connection with sales of businesses. At December 31, 2017 , the estimated maximum exposure for these indemnifications was $89 million , most of which have no set expiration. For certain matters for which Progress Energy receives timely notice, indemnity obligations may extend beyond the notice period. Certain indemnifications related to discontinued operations have no limitations as to time or maximum potential future payments. Duke Energy recognized $21 million and $13 million , as of December 31, 2017 , and 2016 , respectively, primarily in Other within Other Noncurrent Liabilities on the Consolidated Balance Sheets, for the guarantees discussed above. As current estimates change, additional losses related to guarantees and indemnifications to third parties, which could be material, may be recorded by the Duke Energy Registrants in the future.

Joint Ownership of Generating a

Joint Ownership of Generating and Transmission Facilities	12 Months Ended
	Dec. 31, 2017
Joint Ownership Of Generating And Transmission Facilities [Abstract]
Joint Ownership of Generating and Transmission Facilities	JOINT OWNERSHIP OF GENERATING AND TRANSMISSION FACILITIES The Duke Energy Registrants maintain ownership interests in certain jointly owned generating and transmission facilities. The Duke Energy Registrants are entitled to a share of the generating capacity and output of each unit equal to their respective ownership interests. The Duke Energy Registrants pay their ownership share of additional construction costs, fuel inventory purchases and operating expenses. The Duke Energy Registrants share of revenues and operating costs of the jointly owned facilities is included within the corresponding line in the Consolidated Statements of Operations. Each participant in the jointly owned facilities must provide its own financing. The following table presents the Duke Energy Registrants' interest of jointly owned plant or facilities and amounts included on the Consolidated Balance Sheets. All facilities are operated by the Duke Energy Registrants and are included in the Electric Utilities and Infrastructure segment. December 31, 2017 Construction Ownership Property, Plant Accumulated Work in (in millions except for ownership interest) Interest and Equipment Depreciation Progress Duke Energy Carolinas Catawba Nuclear Station (units 1 and 2) (a) 19.25 % $ 927 $ 651 $ 19 Lee Combined Combustion Station (b) 86.67 % — — 552 Duke Energy Ohio Transmission facilities (c) Various 89 63 1 Duke Energy Indiana Gibson Station (unit 5) (d) 50.05 % 348 162 9 Vermillion Generating Station (e) 62.5 % 155 120 — Transmission and local facilities (d) Various 4,672 1,739 — (a) Jointly owned with North Carolina Municipal Power Agency Number 1, NCEMC and Piedmont Municipal Power Agency. (b) Jointly owned with NCEMC. (c) Jointly owned with America Electric Power Generation Resources and The Dayton Power and Light Company. (d) Jointly owned with Wabash Valley Power Association, Inc. (WVPA) and Indiana Municipal Power Agency. (e) Jointly owned with WVPA.

Asset Retirement Obligations

Asset Retirement Obligations	12 Months Ended
	Dec. 31, 2017
Asset Retirement Obligation [Abstract]
Asset Retirement Obligations	ASSET RETIREMENT OBLIGATIONS Duke Energy records an ARO when it has a legal obligation to incur retirement costs associated with the retirement of a long-lived asset and the obligation can be reasonably estimated. Certain assets of the Duke Energy Registrants’ have an indeterminate life, such as transmission and distribution facilities, and thus the fair value of the retirement obligation is not reasonably estimable. A liability for these AROs will be recorded when a fair value is determinable. The Duke Energy Registrants’ regulated operations accrue costs of removal for property that does not have an associated legal retirement obligation based on regulatory orders from state commissions. These costs of removal are recorded as a regulatory liability in accordance with regulatory accounting treatment. The Duke Energy Registrants do not accrue the estimated cost of removal for any nonregulated assets. See Note 4 for the estimated cost of removal for assets without an associated legal retirement obligation, which are included in Regulatory liabilities on the Consolidated Balance Sheets. The following table presents the AROs recorded on the Consolidated Balance Sheets. December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Decommissioning of nuclear power facilities (a) $ 5,371 $ 1,944 $ 3,246 $ 2,564 $ 681 $ — $ — $ — Closure of ash impoundments 4,525 1,629 2,094 2,075 19 39 763 — Other (b) 279 37 74 34 42 45 18 15 Total asset retirement obligation $ 10,175 $ 3,610 $ 5,414 $ 4,673 $ 742 $ 84 $ 781 $ 15 Less: current portion 689 337 295 295 — 3 54 — Total noncurrent asset retirement obligation $ 9,486 $ 3,273 $ 5,119 $ 4,378 $ 742 $ 81 $ 727 $ 15 (a) Duke Energy amount includes purchase accounting adjustments related to the merger with Progress Energy. (b) Primarily includes obligations related to asbestos removal. Duke Energy Ohio and Piedmont also include AROs related to the retirement of natural gas mains and services. Duke Energy includes AROs related to the removal of renewable energy generation assets. Nuclear Decommissioning Liability AROs related to nuclear decommissioning are based on site-specific cost studies. The NCUC, PSCSC and FPSC require updated cost estimates for decommissioning nuclear plants every five years. The following table summarizes information about the most recent site-specific nuclear decommissioning cost studies. Decommissioning costs in the table below are stated in 2013 or 2014 dollars, depending on the year of the cost study, and include costs to decommission plant components not subject to radioactive contamination. Annual Funding Decommissioning (in millions) Requirement (a) Costs (a)(b) Year of Cost Study Duke Energy $ 14 $ 8,150 2013 and 2014 Duke Energy Carolinas — 3,420 2013 Duke Energy Progress 14 3,550 2014 Duke Energy Florida — 1,180 2013 (a) Amounts for Progress Energy equal the sum of Duke Energy Progress and Duke Energy Florida. (b) Amounts include the Subsidiary Registrant's ownership interest in jointly owned reactors. Other joint owners are responsible for decommissioning costs related to their interest in the reactors. Nuclear Decommissioning Trust Funds Duke Energy Carolinas, Duke Energy Progress and Duke Energy Florida each maintain NDTFs that are intended to pay for the decommissioning costs of their respective nuclear power plants. The NDTF investments are managed and invested in accordance with applicable requirements of various regulatory bodies including the NRC, FERC, NCUC, PSCSC, FPSC and the Internal Revenue Service (IRS). Use of the NDTF investments is restricted to nuclear decommissioning activities including license termination, spent fuel and site restoration. The license termination and spent fuel obligations relate to contaminated decommissioning and are recorded as AROs. The site restoration obligation relates to non-contaminated decommissioning and is recorded to cost of removal within Regulatory liabilities on the Consolidated Balance Sheets. The following table presents the fair value of NDTF assets legally restricted for purposes of settling AROs associated with nuclear decommissioning. Duke Energy Florida is actively decommissioning Crystal River Unit 3 and was granted an exemption from the NRC which allows for use of the NDTF for all aspects of nuclear decommissioning. The entire balance of Duke Energy Florida's NDTF may be applied toward license termination, spent fuel and site restoration costs incurred to decommission Crystal River Unit 3. See Note 16 for additional information related to the fair value of the Duke Energy Registrants' NDTFs. December 31, (in millions) 2017 2016 Duke Energy $ 5,864 $ 5,099 Duke Energy Carolinas 3,321 2,882 Duke Energy Progress 2,543 2,217 Nuclear Operating Licenses Operating licenses for nuclear units are potentially subject to extension. The following table includes the current expiration of nuclear operating licenses. Unit Year of Expiration Duke Energy Carolinas Catawba Units 1 and 2 2043 McGuire Unit 1 2041 McGuire Unit 2 2043 Oconee Units 1 and 2 2033 Oconee Unit 3 2034 Duke Energy Progress Brunswick Unit 1 2036 Brunswick Unit 2 2034 Harris 2046 Robinson 2030 Duke Energy Florida has requested the NRC terminate the operating license for Crystal River Unit 3 as it permanently ceased operation in February 2013. In January 2018, Crystal River Unit 3 reached a SAFSTOR status. Closure of Ash Impoundments The Duke Energy Registrants are subject to state and federal regulations covering the closure of coal ash impoundments, including the EPA CCR rule and the Coal Ash Act, and other agreements. AROs recorded on the Duke Energy Registrants' Consolidated Balance Sheets include the legal obligation for closure of coal ash basins and the disposal of related ash as a result of these regulations and agreements. The Coal Ash Act, as amended, requires excavation of the Sutton, Riverbend and Dan River basins by August 1, 2019, and Asheville basins by August 1, 2022. Excavation at these sites may include a combination of transfer of coal ash to an engineered landfill or conversion for beneficial use. Basins at the H.F. Lee, Cape Fear and Weatherspoon sites are required to be closed through excavation no later than August 1, 2028. Excavation at these sites can include conversion of the basin to a lined industrial landfill, transfer of ash to an engineered landfill or conversion for beneficial use. The remaining basins are required to be closed no later than December 31, 2024, through conversion to a lined industrial landfill, transfer to an engineered landfill or conversion for beneficial use, unless certain dam improvement projects and alternative drinking water source projects are completed by October 15, 2018. Upon satisfactory completion of these projects, the closure deadline would be extended to December 31, 2029, and could include closure through the combination of a cap system and a groundwater monitoring system. The Coal Ash Act also required the installation and operation of three large-scale coal ash beneficiation projects to produce reprocessed ash for use in the concrete industry. Duke Energy selected the Buck, H.F. Lee and Cape Fear plants for these projects. Closure at these sites is required to be completed no later than December 31, 2029. The Coal Ash Act includes a variance procedure for compliance deadlines and other issues surrounding the management of CCR and CCR surface impoundments and prohibits cost recovery in customer rates for unlawful discharge of ash impoundment waters occurring after January 1, 2014. The Coal Ash Act leaves the decision on cost recovery determinations related to closure of ash impoundments to the normal ratemaking processes before utility regulatory commissions. Closure plans and all associated permits must be approved by NCDEQ before any closure work can begin. The EPA CCR rule establishes requirements regarding landfill design, structural integrity design and assessment criteria for surface impoundments, groundwater monitoring and protection procedures and other operational and reporting procedures to ensure the safe disposal and management of CCR. The EPA CCR rule has certain requirements which if not met could initiate impoundment closure and require closure completion within five years. The EPA CCR rule includes extension requirements, which if met could allow the extension of closure completion by up to 10 years. The ARO amount recorded on the Consolidated Balance Sheets is based upon estimated closure costs for impacted ash impoundments. The amount recorded represents the discounted cash flows for estimated closure costs based upon either specific closure plans or the probability weightings of the potential closure methods as evaluated on a site-by-site basis. Actual costs to be incurred will be dependent upon factors that vary from site to site. The most significant factors are the method and time frame of closure at the individual sites. Closure methods considered include removing the water from ash basins, consolidating material as necessary and capping the ash with a synthetic barrier, excavating and relocating the ash to a lined structural fill or lined landfill or recycling the ash for concrete or some other beneficial use. The ultimate method and timetable for closure will be in compliance with standards set by federal and state regulations and other agreements. The ARO amount will be adjusted as additional information is gained through the closure and post-closure process, including acceptance and approval of compliance approaches which may change management assumptions, and may result in a material change to the balance. See ARO Liability Rollforward section below for information on revisions made to the coal ash liability during 2017 and 2016. Asset retirement costs associated with the AROs for operating plants and retired plants are included in Net property, plant and equipment and Regulatory assets, respectively, on the Consolidated Balance Sheets. See Note 4 for additional information on Regulatory assets related to AROs. Cost recovery for future expenditures will be pursued through the normal ratemaking process with federal and state utility commissions, which permit recovery of necessary and prudently incurred costs associated with Duke Energy’s regulated operations. See Note 4 for additional information on recovery of coal ash costs. ARO Liability Rollforward During 2017 and 2016 , the Duke Energy Registrants updated coal ash ARO liability estimates based on additional site-specific information for the related costs, methods and timing of work to be performed. Actual closure costs incurred could be materially different from current estimates that form the basis of the recorded AROs. The following tables present changes in the liability associated with AROs. Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Balance at December 31, 2015 $ 10,249 $ 3,918 $ 5,369 $ 4,567 $ 802 $ 125 $ 525 Acquisitions (a) 22 — 2 — 2 — — Accretion expense (b) 400 187 230 194 35 5 24 Liabilities settled (c) (613 ) (287 ) (272 ) (212 ) (60 ) (5 ) (49 ) Liabilities incurred in the current year 51 — 3 3 — — 29 Revisions in estimates of cash flows 502 77 143 145 (1 ) (48 ) 337 Balance at December 31, 2016 10,611 3,895 5,475 4,697 778 77 866 Accretion expense (b) 435 184 228 195 33 3 32 Liabilities settled (c) (619 ) (282 ) (270 ) (204 ) (65 ) (7 ) (49 ) Liabilities incurred in the current year (d) 51 5 — — — 7 29 Revisions in estimates of cash flows (303 ) (192 ) (19 ) (15 ) (4 ) 4 (97 ) Balance at December 31, 2017 $ 10,175 $ 3,610 $ 5,414 $ 4,673 $ 742 $ 84 $ 781 (a) Duke Energy amount relates to the Piedmont acquisition. See Note 2 for additional information. (b) Substantially all accretion expense for the years ended December 31, 2017 , and 2016 relates to Duke Energy’s regulated electric operations and has been deferred in accordance with regulatory accounting treatment. (c) Amounts primarily relate to ash impoundment closures and nuclear decommissioning of Crystal River Unit 3. (d) Amounts primarily relate to AROs recorded as a result of state agency closure requirements at Duke Energy Indiana. (in millions) Piedmont Balance at October 31, 2015 $ 20 Accretion expense 1 Liabilities settled (7 ) Liabilities incurred in the current year 6 Revisions in estimates of cash flows (6 ) Balance at October 31, 2016 14 Liabilities settled (1 ) Liabilities incurred in the current year 1 Balance at December 31, 2016 14 Accretion expense 1 Liabilities settled (8 ) Liabilities incurred in the current year 8 Balance at December 31, 2017 $ 15

Property, Plant and Equipment

Property, Plant and Equipment	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	PROPERTY, PLANT AND EQUIPMENT The following tables summarize the property, plant and equipment for Duke Energy and its subsidiary registrants. December 31, 2017 Estimated Useful Duke Duke Duke Duke Duke Life Duke Energy Progress Energy Energy Energy Energy (in millions) (Years) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Land $ 1,559 $ 467 $ 767 $ 424 $ 343 $ 134 $ 111 $ 41 Plant – Regulated Electric generation, distribution and transmission 8-100 93,687 35,657 39,419 24,502 14,917 4,870 13,741 — Natural gas transmission and distribution 12-80 8,292 — — — — 2,559 — 5,733 Other buildings and improvements 15-100 1,936 647 652 316 336 243 240 154 Plant – Nonregulated Electric generation, distribution and transmission (a) 5-30 4,273 — — — — — — — Other buildings and improvements 25-35 465 — — — — — — — Nuclear fuel 3,680 2,120 1,560 1,560 — — — — Equipment 3-55 2,122 402 555 416 139 348 169 266 Construction in process 6,995 2,614 3,059 1,434 1,625 350 416 231 Other 3-40 4,498 1,032 1,311 931 370 228 271 300 Total property, plant and equipment (b)(e) 127,507 42,939 47,323 29,583 17,730 8,732 14,948 6,725 Total accumulated depreciation – regulated (c)(d)(e) (39,742 ) (15,063 ) (15,857 ) (10,903 ) (4,947 ) (2,691 ) (4,662 ) (1,479 ) Total accumulated depreciation – nonregulated (d)(e) (1,795 ) — — — — — — — Generation facilities to be retired, net 421 — 421 421 — — — — Total net property, plant and equipment $ 86,391 $ 27,876 $ 31,887 $ 19,101 $ 12,783 $ 6,041 $ 10,286 $ 5,246 (a) Includes a pretax impairment charge of $58 million on a wholly owned non-contracted wind project. See discussion below. (b) Includes capitalized leases of $1,294 million , $81 million , $272 million , $139 million , $133 million , $80 million and $35 million at Duke Energy, Duke Energy Carolinas, Progress Energy, Duke Energy Progress, Duke Energy Florida, Duke Energy Ohio and Duke Energy Indiana, respectively, primarily within Plant – Regulated. The Progress Energy, Duke Energy Progress and Duke Energy Florida amounts are net of $114 million , $11 million and $103 million , respectively, of accumulated amortization of capitalized leases. (c) Includes $2,113 million , $1,283 million , $831 million and $831 million of accumulated amortization of nuclear fuel at Duke Energy, Duke Energy Carolinas, Progress Energy and Duke Energy Progress, respectively. (d) Includes accumulated amortization of capitalized leases of $57 million , $11 million , $21 million and $9 million at Duke Energy, Duke Energy Carolinas, Duke Energy Ohio and Duke Energy Indiana, respectively. (e) Includes gross property, plant and equipment cost of consolidated VIEs of $3,941 million and accumulated depreciation of consolidated VIEs of $598 million at Duke Energy. December 31, 2016 Estimated Useful Duke Duke Duke Duke Duke Life Duke Energy Progress Energy Energy Energy Energy (in millions) (Years) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Land $ 1,501 $ 432 $ 735 $ 393 $ 342 $ 150 $ 106 $ 39 Plant – Regulated Electric generation, distribution and transmission 8-100 89,864 34,515 37,596 23,683 13,913 4,593 13,160 — Natural gas transmission and distribution 12-67 7,738 — — — — 2,456 — 5,282 Other buildings and improvements 15-100 1,692 502 634 293 341 211 197 148 Plant – Nonregulated Electric generation, distribution and transmission 5-30 4,298 — — — — — — — Other buildings and improvements 25-35 421 — — — — — — — Nuclear fuel 3,572 2,092 1,480 1,480 — — — — Equipment 3-38 1,941 358 505 378 127 338 156 260 Construction in process 6,186 2,324 2,708 1,329 1,379 206 396 210 Other 5-40 4,184 904 1,206 863 332 172 226 235 Total property, plant and equipment (a)(d) 121,397 41,127 44,864 28,419 16,434 8,126 14,241 6,174 Total accumulated depreciation – regulated (b)(c)(d) (37,831 ) (14,365 ) (15,212 ) (10,561 ) (4,644 ) (2,579 ) (4,317 ) (1,360 ) Total accumulated depreciation – nonregulated (c)(d) (1,575 ) — — — — — — — Generation facilities to be retired, net 529 — 529 529 — — — — Total net property, plant and equipment $ 82,520 $ 26,762 $ 30,181 $ 18,387 $ 11,790 $ 5,547 $ 9,924 $ 4,814 (a) Includes capitalized leases of $1,355 million , $40 million , $288 million , $142 million , $146 million , $81 million and $35 million at Duke Energy, Duke Energy Carolinas, Progress Energy, Duke Energy Progress, Duke Energy Florida, Duke Energy Ohio and Duke Energy Indiana, respectively, primarily within Plant – Regulated. The Progress Energy, Duke Energy Progress and Duke Energy Florida amounts are net of $99 million , $9 million and $90 million , respectively, of accumulated amortization of capitalized leases. (b) Includes $1,922 million , $1,192 million , $730 million and $730 million of accumulated amortization of nuclear fuel at Duke Energy, Duke Energy Carolinas, Progress Energy and Duke Energy Progress, respectively. (c) Includes accumulated amortization of capitalized leases of $50 million , $9 million , $19 million and $8 million at Duke Energy, Duke Energy Carolinas, Duke Energy Ohio and Duke Energy Indiana, respectively. (d) Includes gross property, plant and equipment cost of consolidated VIEs of $2,591 million and accumulated depreciation of consolidated VIEs of $411 million at Duke Energy. During the year ended December 31, 2017, Duke Energy recorded a pretax impairment charge of $69 million on a wholly owned non-contracted wind project. The impairment was recorded within Impairment charges on Duke Energy’s Consolidated Statements of Operations. $58 million of the impairment related to property, plant and equipment and $11 million of the impairment related to a net intangible asset; see Note 11 for additional information. The charge represents the excess carrying value over the estimated fair value of the project, which was based on a Level 3 Fair Value measurement that was determined from the income approach using discounted cash flows. The impairment was primarily due to the non-contracted wind project being located in a market that has experienced continued declining market pricing during 2017 and declining long-term forecasted energy and capacity prices, driven by low natural gas prices, additional renewable generation placed in service and lack of significant load growth. The following tables present capitalized interest, which includes the debt component of AFUDC. Years Ended December 31, (in millions) 2017 2016 2015 Duke Energy $ 128 $ 100 $ 98 Duke Energy Carolinas 45 38 38 Progress Energy 45 31 24 Duke Energy Progress 21 17 20 Duke Energy Florida 24 14 4 Duke Energy Ohio 10 8 10 Duke Energy Indiana 9 7 6 Year Ended Two Months Ended Years Ended October 31, (in millions) December 31, 2017 December 31, 2016 2016 2015 Piedmont $ 12 $ 2 $ 12 $ 11 Operating Leases Duke Energy's Commercial Renewables segment operates various renewable energy projects and sells the generated output to utilities, electric cooperatives, municipalities and commercial and industrial customers through long-term contracts. In certain situations, these long-term contracts and the associated renewable energy projects qualify as operating leases. Rental income from these leases is accounted for as Operating Revenues in the Consolidated Statements of Operations. There are no minimum lease payments as all payments are contingent based on actual electricity generated by the renewable energy projects. Contingent lease payments were $262 million , $216 million , and $172 million for the years ended December 31, 2017 , 2016 and 2015 . As of December 31, 2017 , renewable energy projects owned by Duke Energy and accounted for as operating leases had a cost basis of $3,153 million and accumulated depreciation of $459 million . These assets are principally classified as nonregulated electric generation and transmission assets.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	GOODWILL AND INTANGIBLE ASSETS Goodwill Duke Energy The following table presents goodwill by reportable operating segment for Duke Energy included on Duke Energy's Consolidated Balance Sheets at December 31, 2017 , and 2016 . Electric Utilities Gas Utilities Commercial (in millions) and Infrastructure and Infrastructure Renewables Total Goodwill Balance at December 31, 2016 $ 17,379 $ 1,924 $ 122 $ 19,425 Accumulated impairment charges (a) — — (29 ) (29 ) Goodwill at December 31, 2017 $ 17,379 $ 1,924 $ 93 $ 19,396 (a) Duke Energy evaluated the recoverability of goodwill during 2017 and recorded impairment charges of $29 million related to the Energy Management Solutions reporting unit within the Commercial Renewables segment. The fair value of the reporting unit was determined based on the market approach. Duke Energy Ohio Duke Energy Ohio's Goodwill balance of $920 million , allocated $596 million to Electric Utilities and Infrastructure and $324 million to Gas Utilities and Infrastructure, is presented net of accumulated impairment charges of $216 million on the Consolidated Balance Sheets at December 31, 2017 , and 2016 . Progress Energy Progress Energy's Goodwill is included in the Electric Utilities and Infrastructure operating segment and there are no accumulated impairment charges. Piedmont Piedmont's Goodwill is included in the Gas Utilities and Infrastructure operating segment and there are no accumulated impairment charges. Effective with Piedmont's fiscal year being changed to December 31, as discussed in Note 1 , Piedmont changed the date of its annual impairment testing of goodwill from October 31 to August 31 to align with the other Duke Energy Registrants. Impairment Testing Duke Energy, Progress Energy, Duke Energy Ohio and Piedmont are required to perform an annual goodwill impairment test as of the same date each year and, accordingly, perform their annual impairment testing of goodwill as of August 31. Duke Energy, Progress Energy, Duke Energy Ohio and Piedmont update their test between annual tests if events or circumstances occur that would more likely than not reduce the fair value of a reporting unit below its carrying value. Except for the Energy Management Solutions reporting unit, the fair value of all other reporting units for Duke Energy, Progress Energy, Duke Energy Ohio and Piedmont exceeded their respective carrying values at the date of the annual impairment analysis. Intangible Assets The following tables show the carrying amount and accumulated amortization of intangible assets included in Other within Other Noncurrent Assets on the Consolidated Balance Sheets of the Duke Energy Registrants at December 31, 2017 and 2016 . December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Emission allowances $ 19 $ 1 $ 5 $ 2 $ 3 $ — $ 13 $ — Renewable energy certificates 148 38 107 107 — 3 — — Natural gas, coal and power contracts 24 — — — — — 24 — Renewable operating and development projects 79 — — — — — — — Other 6 — — — — — — 3 Total gross carrying amounts 276 39 112 109 3 3 37 3 Accumulated amortization – natural gas, coal and power contracts (19 ) — — — — — (19 ) — Accumulated amortization – renewable operating and development projects (22 ) — — — — — — — Accumulated amortization – other (5 ) — — — — — — (3 ) Total accumulated amortization (46 ) — — — — — (19 ) (3 ) Total intangible assets, net $ 230 $ 39 $ 112 $ 109 $ 3 $ 3 $ 18 $ — December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Emission allowances $ 19 $ 1 $ 6 $ 2 $ 4 $ — $ 13 $ — Renewable energy certificates 125 36 84 84 — 4 — — Natural gas, coal and power contracts 24 — — — — — 24 — Renewable operating and development projects 97 — — — — — — — Other 6 — — — — — — 3 Total gross carrying amounts 271 37 90 86 4 4 37 3 Accumulated amortization – natural gas, coal and power contracts (17 ) — — — — — (17 ) — Accumulated amortization – renewable operating and development projects (23 ) — — — — — — — Accumulated amortization – other (5 ) — — — — — — (3 ) Total accumulated amortization (45 ) — — — — — (17 ) (3 ) Total intangible assets, net $ 226 $ 37 $ 90 $ 86 $ 4 $ 4 $ 20 $ — During the year ended December 31, 2017, Duke Energy recorded a pretax impairment charge of $69 million on a wholly owned non-contracted wind project. The impairment was recorded within Impairment charges on Duke Energy’s Consolidated Statements of Operations. $58 million of the impairment related to property, plant and equipment and $11 million of the impairment related to a net intangible asset that was recorded in 2007 when the project was acquired. Prior to the impairment, the gross amount of the intangible asset was $18 million and the accumulated amortization was $7 million . The intangible asset was fully impaired. See Note 10 for additional information. Amortization Expense The following table presents amortization expense for natural gas, coal and power contracts, renewable operating projects and other intangible assets. December 31, (in millions) 2017 2016 2015 Duke Energy $ 7 $ 6 $ 5 Duke Energy Indiana 1 1 1 The table below shows the expected amortization expense for the next five years for intangible assets as of December 31, 2017 . The expected amortization expense includes estimates of emission allowances consumption and estimates of consumption of commodities such as natural gas and coal under existing contracts, as well as estimated amortization related to renewable operating projects. The amortization amounts discussed below are estimates and actual amounts may differ from these estimates due to such factors as changes in consumption patterns, sales or impairments of emission allowances or other intangible assets, delays in the in-service dates of renewable assets, additional intangible acquisitions and other events. (in millions) 2018 2019 2020 2021 2022 Duke Energy $ 3 $ 2 $ 2 $ 2 $ 2 Duke Energy Indiana 1 — — — —

Investments in Unconsolidated A

Investments in Unconsolidated Affiliates	12 Months Ended
	Dec. 31, 2017
Equity Method Investments and Joint Ventures [Abstract]
Investment in Unconsolidated Affiliates	INVESTMENTS IN UNCONSOLIDATED AFFILIATES EQUITY METHOD INVESTMENTS Investments in domestic and international affiliates that are not controlled by Duke Energy, but over which it has significant influence, are accounted for using the equity method. The following table presents Duke Energy’s investments in unconsolidated affiliates accounted for under the equity method, as well as the respective equity in earnings, by segment. Years Ended December 31, 2017 2016 2015 Equity in Equity in Equity in (in millions) Investments earnings Investments earnings earnings Electric Utilities and Infrastructure $ 89 $ 5 $ 93 $ 5 $ (2 ) Gas Utilities and Infrastructure 763 62 566 19 1 Commercial Renewables 190 (5 ) 185 (82 ) (6 ) Other 133 57 81 43 76 Total $ 1,175 $ 119 $ 925 $ (15 ) $ 69 During the years ended December 31, 2017 , 2016 and 2015 , Duke Energy received distributions from equity investments of $13 million , $31 million and $104 million , respectively, which are included in Other assets within Cash Flows from Operating Activities on the Consolidated Statements of Cash Flows. During the year ended December 31, 2017, Duke Energy received distributions from equity investments of $281 million , which are included within Cash Flows from Investing Activities on the Consolidated Statements of Cash Flows. During the year ended December 31, 2017, the two months ended December 31, 2016 , and the years ended October 31, 2016, and 2015 , Piedmont received distributions from equity investments of $4 million , $1 million , $26 million and $25 million , respectively, which are included in Other assets within Cash Flows from Operating Activities and $2 million , $1 million , $18 million and $2 million , respectively, which are included within Cash Flows from Investing Activities on the Consolidated Statements of Cash Flows. Significant investments in affiliates accounted for under the equity method are discussed below. Electric Utilities and Infrastructure Duke Energy owns a 50 percent interest in Duke-American Transmission Co. (DATC) and in Pioneer Transmission, LLC (Pioneer), which build, own and operate electric transmission facilities in North America. Gas Utilities and Infrastructure The table below outlines Duke Energy's ownership interests in natural gas pipeline companies and natural gas storage facilities. Investment Amount (in millions) Ownership December 31, December 31, Entity Name Interest 2017 2016 Pipeline Investments Atlantic Coast Pipeline, LLC (a) 47 % $ 397 $ 265 Sabal Trail Transmission, LLC 7.5 % 219 140 Constitution Pipeline, LLC (a) 24 % 81 82 Cardinal Pipeline Company, LLC (b) 21.49 % 11 16 Storage Facilities Pine Needle LNG Company, LLC (b) 45 % 13 16 Hardy Storage Company, LLC (b) 50 % 42 47 Total Investments (c) $ 763 $ 566 (a) During the year ended December 31, 2017, Piedmont transferred its share of ownership interest in ACP and Constitution to a wholly owned subsidiary of Duke Energy at book value. (b) Piedmont owns the Cardinal, Pine Needle and Hardy Storage investments. (c) Duke Energy includes purchase accounting adjustments related to Piedmont. In October 2017, Duke Energy entered into a guarantee agreement to support its share of the ACP revolving credit facility. See Note 7 for additional information. As a result of the financing, ACP returned capital of $265 million to Duke Energy. Piedmont sold its 15 percent membership interest in SouthStar on October 3, 2016, for $160 million resulting in an after tax gain of $81 million during the year ended October 31, 2016. Piedmont's Equity in Earnings in SouthStar was $19 million for the years ended October 31, 2016, and 2015. For regulatory matters and other information on the ACP, Sabal Trail and Constitution investments, see Notes 4 and 17. Commercial Renewables In 2016, Duke Energy sold its interest in three of the Catamount Sweetwater, LLC wind farm projects. Duke Energy has a 47 percent ownership interest in each of the two other Catamount Sweetwater, LLC wind farm projects and 50 percent interest in DS Cornerstone, LLC, which owns wind farm projects in the U.S. Impairment of Equity Method Investments Duke Energy evaluated its investment in Constitution for OTTI as of December 31, 2017. Our impairment assessment uses a discounted cash flow income approach, including consideration of the severity and duration of any decline in fair value of our investment in the project. Our key inputs involve significant management judgments and estimates, including projections of the project’s cash flows, selection of a discount rate and probability weighting of potential outcomes of legal and regulatory proceedings. Based upon these estimates using information known as of December 31, 2017, the fair value of Duke Energy's investment in Constitution approximated its carrying value. As a result, Duke Energy did not recognize any impairment charge in the year ended December 31, 2017. However, due to the FERC’s January 2018 ruling and the resulting increase in uncertainty, Duke Energy is evaluating the potential to recognize a pretax impairment charge on its investment in Constitution during the first quarter of 2018 of up to the current carrying amount of the investment, net of salvage value and any cash and working capital returned. For additional information on the Constitution investment, see Note 4. During the year ended December 31, 2016, Duke Energy recorded an OTTI of certain wind project investments. The $71 million pretax impairment was recorded within Equity in earnings (losses) of unconsolidated affiliates on Duke Energy's Consolidated Statements of Operations. The other-than-temporary decline in value of these investments was primarily attributable to a sustained decline in market pricing where the wind investments are located, projected net losses for the projects and a reduction in the projected cash distribution to the class of investment owned by Duke Energy. Other Duke Energy owns a 17.5 percent indirect interest in NMC, which owns and operates a methanol and MTBE business in Jubail, Saudi Arabia. Duke Energy's economic ownership interest decreased from 25 percent to 17.5 percent with the successful startup of NMC's polyacetal production facility in 2017. Duke Energy retains 25 percent of the board representation and voting rights of NMC. The investment in NMC is accounted for under the equity method of accounting.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Related Party Transactions	RELATED PARTY TRANSACTIONS The Subsidiary Registrants engage in related party transactions in accordance with the applicable state and federal commission regulations. Refer to the Consolidated Balance Sheets of the Subsidiary Registrants for balances due to or due from related parties. Material amounts related to transactions with related parties included in the Consolidated Statements of Operations and Comprehensive Income are presented in the following table. Years Ended December 31, (in millions) 2017 2016 2015 Duke Energy Carolinas Corporate governance and shared service expenses (a) $ 858 $ 831 $ 914 Indemnification coverages (b) 23 22 24 JDA revenue (c) 49 38 51 JDA expense (c) 145 156 183 Intercompany natural gas purchases (d) 9 2 — Progress Energy Corporate governance and shared service expenses (a) $ 736 $ 710 $ 712 Indemnification coverages (b) 38 35 38 JDA revenue (c) 145 156 183 JDA expense (c) 49 38 51 Intercompany natural gas purchases (d) 77 19 — Duke Energy Progress Corporate governance and shared service expenses (a) $ 438 $ 397 $ 403 Indemnification coverages (b) 15 14 16 JDA revenue (c) 145 156 183 JDA expense (c) 49 38 51 Intercompany natural gas purchases (d) 77 19 — Duke Energy Florida Corporate governance and shared service expenses (a) $ 298 $ 313 $ 309 Indemnification coverages (b) 23 21 22 Duke Energy Ohio Corporate governance and shared service expenses (a) $ 363 $ 356 $ 342 Indemnification coverages (b) 5 5 6 Duke Energy Indiana Corporate governance and shared service expenses (a) $ 370 $ 366 $ 349 Indemnification coverages (b) 8 8 9 Piedmont Corporate governance and shared service expenses (a) $ 50 Indemnification coverages (b) 2 Intercompany natural gas sales (d) 86 (a) The Subsidiary Registrants are charged their proportionate share of corporate governance and other shared services costs, primarily related to human resources, employee benefits, information technology, legal and accounting fees, as well as other third-party costs. These amounts are primarily recorded in Operation, maintenance and other on the Consolidated Statements of Operations and Comprehensive Income. (b) The Subsidiary Registrants incur expenses related to certain indemnification coverages through Bison, Duke Energy’s wholly owned captive insurance subsidiary. These expenses are recorded in Operation, maintenance and other on the Consolidated Statements of Operations and Comprehensive Income. (c) Duke Energy Carolinas and Duke Energy Progress participate in a JDA, which allows the collective dispatch of power plants between the service territories to reduce customer rates. Revenues from the sale of power and expenses from the purchase of power pursuant to the JDA are recorded in Operating Revenues and Fuel used in electric generation and purchased power, respectively, on the Consolidated Statements of Operations and Comprehensive Income. (d) Piedmont provides long-term natural gas delivery service to certain Duke Energy Carolinas and Duke Energy Progress natural gas-fired generation facilities. Piedmont records the sales in Regulated natural gas revenues, and Duke Energy Carolinas and Duke Energy Progress record the related purchases in Fuel used in electric generation and purchased power on their respective Consolidated Statements of Operations and Comprehensive Income. The amounts are not eliminated in accordance with rate-based accounting regulations. For the two months ended December 31, 2016, and for sales made subsequent to the acquisition for the year ended October 31, 2016, Piedmont recorded $14 million and $7 million , respectively, of natural gas sales with Duke Energy. For sales made prior to the acquisition for the year ended October 31, 2016, and for the year ended October 31, 2015, Piedmont recorded $74 million and $83 million , respectively of natural gas sales with Duke Energy. In addition to the amounts presented above, the Subsidiary Registrants have other affiliate transactions, including rental of office space, participation in a money pool arrangement, other operational transactions and their proportionate share of certain charged expenses. See Note 6 for more information regarding money pool. These transactions of the Subsidiary Registrants were not material for the years ended December 31, 2017 , 2016 and 2015 . As discussed in Note 17 , certain trade receivables have been sold by Duke Energy Ohio and Duke Energy Indiana to CRC, an affiliate formed by a subsidiary of Duke Energy. The proceeds obtained from the sales of receivables are largely cash but do include a subordinated note from CRC for a portion of the purchase price. Refer to Note 2 for further information on the sale of the Midwest Generation Disposal Group. Equity Method Investments Piedmont has related party transactions as a customer of its equity method investments in natural gas storage and transportation facilities. The following table presents expenses that are included in Cost of natural gas on Piedmont's Consolidated Statements of Operations and Comprehensive Income. Year Ended December 31, Two Months Ended December 31, Years Ended October 31, (in millions) Type of expense 2017 2016 2016 2015 Cardinal Transportation Costs $ 8 $ 2 $ 9 $ 9 Pine Needle Natural Gas Storage Costs 8 2 11 11 Hardy Storage Natural Gas Storage Costs 9 2 9 9 Total $ 25 $ 6 $ 29 $ 29 Piedmont had accounts payable to its equity method investments of $2 million at December 31, 2017 , and 2016 related to these transactions. These amounts are included in Accounts payable on the Consolidated Balance Sheets. Intercompany Income Taxes Duke Energy and the Subsidiary Registrants file a consolidated federal income tax return and other state and jurisdictional returns. The Subsidiary Registrants have a tax sharing agreement with Duke Energy for the allocation of consolidated tax liabilities and benefits. Income taxes recorded represent amounts the Subsidiary Registrants would incur as separate C-Corporations. The following table includes the balance of intercompany income tax receivables and payables for the Subsidiary Registrants. Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Carolinas Energy Progress Florida Ohio Indiana Piedmont December 31, 2017 Intercompany income tax receivable $ — $ 168 $ — $ 44 $ 22 $ — $ 7 Intercompany income tax payable 44 — 21 — — 35 — December 31, 2016 Intercompany income tax receivable $ 1 $ — $ — $ 37 $ — $ — $ — Intercompany income tax payable — 37 90 — 1 3 38

Derivatives and Hedging

Derivatives and Hedging	12 Months Ended
	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives and Hedging	DERIVATIVES AND HEDGING The Duke Energy Registrants use commodity and interest rate contracts to manage commodity price risk and interest rate risk. The primary use of commodity derivatives is to hedge the generation portfolio against changes in the prices of electricity and natural gas. Piedmont enters into natural gas supply contracts to provide diversification, reliability and natural gas cost benefits to its customers. Interest rate swaps are used to manage interest rate risk associated with borrowings. All derivative instruments not identified as NPNS are recorded at fair value as assets or liabilities on the Consolidated Balance Sheets. Cash collateral related to derivative instruments executed under master netting arrangements is offset against the collateralized derivatives on the Consolidated Balance Sheets. The cash impacts of settled derivatives are recorded as operating activities on the Consolidated Statements of Cash Flows. INTEREST RATE RISK The Duke Energy Registrants are exposed to changes in interest rates as a result of their issuance or anticipated issuance of variable-rate and fixed-rate debt and commercial paper. Interest rate risk is managed by limiting variable-rate exposures to a percentage of total debt and by monitoring changes in interest rates. To manage risk associated with changes in interest rates, the Duke Energy Registrants may enter into interest rate swaps, U.S. Treasury lock agreements and other financial contracts. In anticipation of certain fixed-rate debt issuances, a series of forward-starting interest rate swaps may be executed to lock in components of current market interest rates. These instruments are later terminated prior to or upon the issuance of the corresponding debt. Cash Flow Hedges For a derivative designated as hedging the exposure to variable cash flows of a future transaction, referred to as a cash flow hedge, the effective portion of the derivative's gain or loss is initially reported as a component of other comprehensive income and subsequently reclassified into earnings once the future transaction impacts earnings. Amounts for interest rate contracts are reclassified to earnings as interest expense over the term of the related debt. See the Consolidated Statements of Changes in Equity for gains and losses reclassified out of AOCI for the years ended December 31, 2017 , and 2016 . Duke Energy's interest rate derivatives designated as hedges include interest rate swaps used to hedge existing debt within the Commercial Renewables business. Undesignated Contracts Undesignated contracts include contracts not designated as a hedge because they are accounted for under regulatory accounting and contracts that do not qualify for hedge accounting. Duke Energy’s interest rate swaps for its regulated operations employ regulatory accounting. With regulatory accounting, the mark-to-market gains or losses on the swaps are deferred as regulatory liabilities or regulatory assets, respectively. Regulatory assets and liabilities are amortized consistent with the treatment of the related costs in the ratemaking process. The accrual of interest on the swaps is recorded as Interest Expense. In August 2016, Duke Energy unwound $1.4 billion of forward-starting interest rate swaps associated with the Piedmont acquisition financing described in Note 6. The swaps were considered undesignated as they did not qualify for hedge accounting. Losses on the swaps of $190 million are included within Interest Expense on the Consolidated Statements of Operations for the year ended December 31, 2016. See Note 2 for additional information related to the Piedmont acquisition. The following tables show notional amounts of outstanding derivatives related to interest rate risk. December 31, 2017 Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Cash flow hedges (a) $ 660 $ — $ — $ — $ — $ — Undesignated contracts 927 400 500 250 250 27 Total notional amount $ 1,587 $ 400 $ 500 $ 250 $ 250 $ 27 December 31, 2016 Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Cash flow hedges (a) $ 750 $ — $ — $ — $ — $ — Undesignated contracts 927 400 500 250 250 27 Total notional amount $ 1,677 $ 400 $ 500 $ 250 $ 250 $ 27 (a) Duke Energy includes amounts related to consolidated VIEs of $660 million and $750 million at December 31, 2017 , and 2016 , respectively. During 2016, Duke Energy entered into interest rate swaps related to solar financing with an outstanding notional amount of $300 million , including $81 million of four-year swaps and $219 million of 18-year swaps, at December 31, 2016. See note 6 for additional information related to the solar facilities financing. COMMODITY PRICE RISK The Duke Energy Registrants are exposed to the impact of changes in the prices of electricity purchased and sold in bulk power markets and coal and natural gas purchases, including Piedmont's natural gas supply contracts. Exposure to commodity price risk is influenced by a number of factors including the term of contracts, the liquidity of markets and delivery locations. For the Subsidiary Registrants, bulk power electricity and coal and natural gas purchases flow through fuel adjustment clauses, formula based contracts or other cost sharing mechanisms. Differences between the costs included in rates and the incurred costs, including undesignated derivative contracts, are largely deferred as regulatory assets or regulatory liabilities. Piedmont policies allow for the use of financial instruments to hedge commodity price risks. The strategy and objective of these hedging programs are to use the financial instruments to reduce gas cost volatility for customers. Volumes The tables below include volumes of outstanding commodity derivatives. Amounts disclosed represent the absolute value of notional volumes of commodity contracts excluding NPNS. The Duke Energy Registrants have netted contractual amounts where offsetting purchase and sale contracts exist with identical delivery locations and times of delivery. Where all commodity positions are perfectly offset, no quantities are shown. December 31, 2017 Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy Carolinas Energy Progress Florida Indiana Piedmont Electricity (gigawatt-hours) 34 — — — — 34 — Natural gas (millions of dekatherms) 770 105 183 133 50 2 480 December 31, 2016 Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy Carolinas Energy Progress Florida Indiana Piedmont Electricity (gigawatt-hours) 147 — — — — 147 — Natural gas (millions of dekatherms) 890 91 269 118 151 1 529 LOCATION AND FAIR VALUE OF DERIVATIVE ASSETS AND LIABILITIES RECOGNIZED IN THE CONSOLIDATED BALANCE SHEETS The following tables show the fair value and balance sheet location of derivative instruments. Although derivatives subject to master netting arrangements are netted on the Consolidated Balance Sheets, the fair values presented below are shown gross and cash collateral on the derivatives has not been netted against the fair values shown. Derivative Assets December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Commodity Contracts Not Designated as Hedging Instruments Current $ 34 $ 2 $ 2 $ 1 $ 1 $ 1 $ 27 $ 2 Noncurrent 1 — 1 1 — — — — Total Derivative Assets – Commodity Contracts $ 35 $ 2 $ 3 $ 2 $ 1 $ 1 $ 27 $ 2 Interest Rate Contracts Designated as Hedging Instruments Current $ 1 $ — $ — $ — $ — $ — $ — $ — Noncurrent 15 — — — — — — — Total Derivative Assets – Interest Rate Contracts $ 16 $ — $ — $ — $ — $ — $ — $ — Total Derivative Assets $ 51 $ 2 $ 3 $ 2 $ 1 $ 1 $ 27 $ 2 Derivative Liabilities December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Commodity Contracts Not Designated as Hedging Instruments Current $ 36 $ 6 $ 18 $ 8 $ 10 $ — $ — $ 11 Noncurrent 146 4 10 4 — — — 131 Total Derivative Liabilities – Commodity Contracts $ 182 $ 10 $ 28 $ 12 $ 10 $ — $ — $ 142 Interest Rate Contracts Designated as Hedging Instruments Current $ 29 $ 25 $ — $ — $ — $ — $ — $ — Noncurrent 6 — — — — — — — Not Designated as Hedging Instruments Current 1 — 1 — — 1 — — Noncurrent 12 — 7 6 2 4 — — Total Derivative Liabilities – Interest Rate Contracts $ 48 $ 25 $ 8 $ 6 $ 2 $ 5 $ — $ — Total Derivative Liabilities $ 230 $ 35 $ 36 $ 18 $ 12 $ 5 $ — $ 142 Derivative Assets December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Commodity Contracts Not Designated as Hedging Instruments Current $ 108 $ 23 $ 61 $ 35 $ 26 $ 4 $ 16 $ 3 Noncurrent 32 10 21 10 11 1 — — Total Derivative Assets – Commodity Contracts $ 140 $ 33 $ 82 $ 45 $ 37 $ 5 $ 16 $ 3 Interest Rate Contracts Designated as Hedging Instruments Noncurrent $ 19 $ — $ — $ — $ — $ — $ — $ — Not Designated as Hedging Instruments Current 3 — 3 1 2 — — — Total Derivative Assets – Interest Rate Contracts $ 22 $ — $ 3 $ 1 $ 2 $ — $ — $ — Total Derivative Assets $ 162 $ 33 $ 85 $ 46 $ 39 $ 5 $ 16 $ 3 Derivative Liabilities December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Commodity Contracts Not Designated as Hedging Instruments Current $ 43 $ — $ 12 $ — $ 12 $ — $ 2 $ 35 Noncurrent 166 1 7 1 — — — 152 Total Derivative Liabilities – Commodity Contracts $ 209 $ 1 $ 19 $ 1 $ 12 $ — $ 2 $ 187 Interest Rate Contracts Designated as Hedging Instruments Current $ 8 $ — $ — $ — $ — $ — $ — $ — Noncurrent 8 — — — — — — — Not Designated as Hedging Instruments Current 1 — — — — 1 — — Noncurrent 26 15 6 6 — 5 — — Total Derivative Liabilities – Interest Rate Contracts $ 43 $ 15 $ 6 $ 6 $ — $ 6 $ — $ — Total Derivative Liabilities $ 252 $ 16 $ 25 $ 7 $ 12 $ 6 $ 2 $ 187 OFFSETTING ASSETS AND LIABILITIES The following tables present the line items on the Consolidated Balance Sheets where derivatives are reported. Substantially all of Duke Energy's outstanding derivative contracts are subject to enforceable master netting arrangements. The Gross amounts offset in the tables below show the effect of these netting arrangements on financial position and include collateral posted to offset the net position. The amounts shown are calculated by counterparty. Accounts receivable or accounts payable may also be available to offset exposures in the event of bankruptcy. These amounts are not included in the tables below. Derivative Assets December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Current Gross amounts recognized $ 35 $ 2 $ 2 $ 1 $ 1 $ 1 $ 27 $ 2 Gross amounts offset — — — — — — — — Net amounts presented in Current Assets: Other $ 35 $ 2 $ 2 $ 1 $ 1 $ 1 $ 27 $ 2 Noncurrent Gross amounts recognized $ 16 $ — $ 1 $ 1 $ — $ — $ — $ — Gross amounts offset — — — — — — — — Net amounts presented in Other Noncurrent Assets: Other $ 16 $ — $ 1 $ 1 $ — $ — $ — $ — Derivative Liabilities December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Current Gross amounts recognized $ 66 $ 31 $ 19 $ 8 $ 10 $ 1 $ — $ 11 Gross amounts offset (3 ) (2 ) (2 ) (2 ) — — — — Net amounts presented in Current Liabilities: Other $ 63 $ 29 $ 17 $ 6 $ 10 $ 1 $ — $ 11 Noncurrent Gross amounts recognized $ 164 $ 4 $ 17 $ 10 $ 2 $ 4 $ — $ 131 Gross amounts offset (1 ) — (1 ) (1 ) — — — — Net amounts presented in Other Noncurrent Liabilities: Other $ 163 $ 4 $ 16 $ 9 $ 2 $ 4 $ — $ 131 Derivative Assets December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Current Gross amounts recognized $ 111 $ 23 $ 64 $ 36 $ 28 $ 4 $ 16 $ 3 Gross amounts offset (11 ) — (11 ) — (11 ) — — — Net amounts presented in Current Assets: Other $ 100 $ 23 $ 53 $ 36 $ 17 $ 4 $ 16 $ 3 Noncurrent Gross amounts recognized $ 51 $ 10 $ 21 $ 10 $ 11 $ 1 $ — $ — Gross amounts offset (2 ) (1 ) (1 ) (1 ) — — — — Net amounts presented in Other Noncurrent Assets: Other $ 49 $ 9 $ 20 $ 9 $ 11 $ 1 $ — $ — Derivative Liabilities December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Current Gross amounts recognized $ 52 $ — $ 12 $ — $ 12 $ 1 $ 2 $ 35 Gross amounts offset (11 ) — (11 ) — (11 ) — — — Net amounts presented in Current Liabilities: Other $ 41 $ — $ 1 $ — $ 1 $ 1 $ 2 $ 35 Noncurrent Gross amounts recognized $ 200 $ 16 $ 13 $ 7 $ — $ 5 $ — $ 152 Gross amounts offset (2 ) (1 ) (1 ) (1 ) — — — — Net amounts presented in Other Noncurrent Liabilities: Other $ 198 $ 15 $ 12 $ 6 $ — $ 5 $ — $ 152 OBJECTIVE CREDIT CONTINGENT FEATURES Certain derivative contracts contain objective credit contingent features. These features include the requirement to post cash collateral or letters of credit if specific events occur, such as a credit rating downgrade below investment grade. The following tables show information with respect to derivative contracts that are in a net liability position and contain objective credit-risk-related payment provisions. December 31, 2017 Duke Duke Duke Duke Energy Progress Energy Energy (in millions) Energy Carolinas Energy Progress Florida Aggregate fair value of derivatives in a net liability position $ 59 $ 35 $ 25 $ 15 $ 10 Fair value of collateral already posted — — — — — Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered 59 35 25 15 10 December 31, 2016 Duke Duke Duke Duke Energy Progress Energy Energy (in millions) Energy Carolinas Energy Progress Florida Aggregate fair value of derivatives in a net liability position $ 34 $ 16 $ 18 $ 6 $ 12 Fair value of collateral already posted — — — — — Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered 34 16 18 6 12 The Duke Energy Registrants have elected to offset cash collateral and fair values of derivatives. For amounts to be netted, the derivative and cash collateral must be executed with the same counterparty under the same master netting arrangement.

Investments in Debt and Equity

Investments in Debt and Equity Securities	12 Months Ended
	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Investments in Debt and Equity Securities	INVESTMENTS IN DEBT AND EQUITY SECURITIES The Duke Energy Registrants classify their investments in debt and equity securities as either trading or available-for-sale. TRADING SECURITIES Piedmont's investments in debt and equity securities held in rabbi trusts associated with certain deferred compensation plans are classified as trading securities. The fair value of these investments was $1 million and $5 million as of December 31, 2017 , and 2016 , respectively. AVAILABLE-FOR-SALE (AFS) SECURITIES All other investments in debt and equity securities are classified as AFS. Duke Energy’s AFS securities are primarily comprised of investments held in (i) the nuclear decommissioning trust funds (NDTF) at Duke Energy Carolinas, Duke Energy Progress and Duke Energy Florida, (ii) grantor trusts at Duke Energy Progress, Duke Energy Florida and Duke Energy Indiana related to OPEB plans and (iii) Bison. Duke Energy classifies all other investments in debt and equity securities as long term, unless otherwise noted. Investment Trusts The investments within the NDTF investments and the Duke Energy Progress, Duke Energy Florida and Duke Energy Indiana grantor trusts (Investment Trusts) are managed by independent investment managers with discretion to buy, sell and invest pursuant to the objectives set forth by the trust agreements. The Duke Energy Registrants have limited oversight of the day-to-day management of these investments. As a result, the ability to hold investments in unrealized loss positions is outside the control of the Duke Energy Registrants. Accordingly, all unrealized losses associated with debt and equity securities within the Investment Trusts are considered OTTIs and are recognized immediately. Investments within the Investment Trusts generally qualify for regulatory accounting and accordingly realized and unrealized gains and losses are generally deferred as a regulatory asset or liability. Substantially all amounts of the Duke Energy Registrants' gross unrealized holding losses as of December 31, 2017 , and 2016 , are considered OTTIs on investments within Investment Trusts that have been recognized immediately as a regulatory asset. Other AFS Securities Unrealized gains and losses on all other AFS securities are included in other comprehensive income until realized, unless it is determined the carrying value of an investment is other-than-temporarily impaired. If an OTTI exists, the unrealized loss is included in earnings based on the criteria discussed below. The Duke Energy Registrants analyze all investment holdings each reporting period to determine whether a decline in fair value should be considered other-than-temporary. Criteria used to evaluate whether an impairment associated with equity securities is other-than-temporary includes, but is not limited to, (i) the length of time over which the market value has been lower than the cost basis of the investment, (ii) the percentage decline compared to the cost of the investment and (iii) management’s intent and ability to retain its investment for a period of time sufficient to allow for any anticipated recovery in market value. If a decline in fair value is determined to be other-than-temporary, the investment is written down to its fair value through a charge to earnings. If the entity does not have an intent to sell a debt security and it is not more likely than not management will be required to sell the debt security before the recovery of its cost basis, the impairment write-down to fair value would be recorded as a component of other comprehensive income, except for when it is determined a credit loss exists. In determining whether a credit loss exists, management considers, among other things, (i) the length of time and the extent to which the fair value has been less than the amortized cost basis, (ii) changes in the financial condition of the issuer of the security, or in the case of an asset backed security, the financial condition of the underlying loan obligors, (iii) consideration of underlying collateral and guarantees of amounts by government entities, (iv) ability of the issuer of the security to make scheduled interest or principal payments and (v) any changes to the rating of the security by rating agencies. If a credit loss exists, the amount of impairment write-down to fair value is split between credit loss and other factors. The amount related to credit loss is recognized in earnings. The amount related to other factors is recognized in other comprehensive income. There were no material credit losses as of December 31, 2017 , and 2016 . Other Investments amounts are recorded in Other within Other Noncurrent Assets on the Consolidated Balance Sheets. DUKE ENERGY The following table presents the estimated fair value of investments in AFS securities. December 31, 2017 December 31, 2016 Gross Gross Gross Gross Unrealized Unrealized Unrealized Unrealized Holding Holding Estimated Holding Holding Estimated (in millions) Gains Losses Fair Value Gains Losses (a) Fair Value NDTF Cash and cash equivalents $ — $ — $ 115 $ — $ — $ 111 Equity securities 2,805 27 4,914 2,092 54 4,106 Corporate debt securities 17 2 570 10 8 528 Municipal bonds 4 3 344 3 10 331 U.S. government bonds 11 7 1,027 10 8 984 Other debt securities — 1 118 — 3 124 Total NDTF $ 2,837 $ 40 $ 7,088 $ 2,115 $ 83 $ 6,184 Other Investments Cash and cash equivalents $ — $ — $ 15 $ — $ — $ 25 Equity securities 59 — 123 38 — 104 Corporate debt securities 1 — 57 1 1 66 Municipal bonds 2 1 83 2 1 82 U.S. government bonds — — 41 — 1 51 Other debt securities — 1 44 — 2 42 Total Other Investments $ 62 $ 2 $ 363 $ 41 $ 5 $ 370 Total Investments $ 2,899 $ 42 $ 7,451 $ 2,156 $ 88 $ 6,554 The table below summarizes the maturity date for debt securities. (in millions) December 31, 2017 Due in one year or less $ 117 Due after one through five years 552 Due after five through 10 years 554 Due after 10 years 1,061 Total $ 2,284 Realized gains and losses, which were determined on a specific identification basis, from sales of AFS securities were as follows. Years Ended December 31, (in millions) 2017 2016 2015 Realized gains $ 202 $ 246 $ 193 Realized losses 160 187 98 DUKE ENERGY CAROLINAS The following table presents the estimated fair value of investments in AFS securities. December 31, 2017 December 31, 2016 Gross Gross Gross Gross Unrealized Unrealized Unrealized Unrealized Holding Holding Estimated Holding Holding Estimated (in millions) Gains Losses Fair Value Gains Losses (a) Fair Value NDTF Cash and cash equivalents $ — $ — $ 32 $ — $ — $ 18 Equity securities 1,531 12 2,692 1,157 28 2,245 Corporate debt securities 9 2 359 5 6 354 Municipal bonds — 1 60 1 2 67 U.S. government bonds 3 4 503 2 5 458 Other debt securities — 1 112 — 3 116 Total NDTF $ 1,543 $ 20 $ 3,758 $ 1,165 $ 44 $ 3,258 Other Investments Other debt securities $ — $ — $ — $ — $ 1 $ 3 Total Other Investments $ — $ — $ — $ — $ 1 $ 3 Total Investments $ 1,543 $ 20 $ 3,758 $ 1,165 $ 45 $ 3,261 The table below summarizes the maturity date for debt securities. (in millions) December 31, 2017 Due in one year or less $ 9 Due after one through five years 204 Due after five through 10 years 300 Due after 10 years 521 Total $ 1,034 Realized gains and losses, which were determined on a specific identification basis, from sales of AFS securities were as follows. Years Ended December 31, (in millions) 2017 2016 2015 Realized gains $ 135 $ 157 $ 158 Realized losses 103 121 83 PROGRESS ENERGY The following table presents the estimated fair value of investments in AFS securities. December 31, 2017 December 31, 2016 Gross Gross Gross Gross Unrealized Unrealized Unrealized Unrealized Holding Holding Estimated Holding Holding Estimated (in millions) Gains Losses Fair Value Gains Losses (a) Fair Value NDTF Cash and cash equivalents $ — $ — $ 83 $ — $ — $ 93 Equity securities 1,274 15 2,222 935 26 1,861 Corporate debt securities 8 — 211 5 2 174 Municipal bonds 4 2 284 2 8 264 U.S. government bonds 8 3 524 8 3 526 Other debt securities — — 6 — — 8 Total NDTF $ 1,294 $ 20 $ 3,330 $ 950 $ 39 $ 2,926 Other Investments Cash and cash equivalents $ — $ — $ 12 $ — $ — $ 21 Municipal bonds 2 — 47 2 — 44 Total Other Investments $ 2 $ — $ 59 $ 2 $ — $ 65 Total Investments $ 1,296 $ 20 $ 3,389 $ 952 $ 39 $ 2,991 The table below summarizes the maturity date for debt securities. (in millions) December 31, 2017 Due in one year or less $ 94 Due after one through five years 301 Due after five through 10 years 203 Due after 10 years 474 Total $ 1,072 Realized gains and losses, which were determined on a specific identification basis, from sales of AFS securities were as follows. Years Ended December 31, (in millions) 2017 2016 2015 Realized gains $ 65 $ 84 $ 33 Realized losses 56 64 13 DUKE ENERGY PROGRESS The following table presents the estimated fair value of investments in AFS securities. December 31, 2017 December 31, 2016 Gross Gross Gross Gross Unrealized Unrealized Unrealized Unrealized Holding Holding Estimated Holding Holding Estimated (in millions) Gains Losses Fair Value Gains Losses (a) Fair Value NDTF Cash and cash equivalents $ — $ — $ 50 $ — $ — $ 45 Equity securities 980 12 1,795 704 21 1,505 Corporate debt securities 6 149 4 1 120 Municipal bonds 4 2 283 2 8 263 U.S. government bonds 5 2 310 5 2 275 Other debt securities — — 4 — — 5 Total NDTF $ 995 $ 16 $ 2,591 $ 715 $ 32 $ 2,213 Other Investments Cash and cash equivalents $ — $ — $ 1 $ — $ — $ 1 Total Other Investments $ — $ — $ 1 $ — $ — $ 1 Total Investments $ 995 $ 16 $ 2,592 $ 715 $ 32 $ 2,214 The table below summarizes the maturity date for debt securities. (in millions) December 31, 2017 Due in one year or less $ 21 Due after one through five years 219 Due after five through 10 years 146 Due after 10 years 360 Total $ 746 Realized gains and losses, which were determined on a specific identification basis, from sales of AFS securities were as follows. Years Ended December 31, (in millions) 2017 2016 2015 Realized gains $ 54 $ 71 $ 26 Realized losses 48 55 11 DUKE ENERGY FLORIDA The following table presents the estimated fair value of investments in AFS securities. December 31, 2017 December 31, 2016 Gross Gross Gross Gross Unrealized Unrealized Unrealized Unrealized Holding Holding Estimated Holding Holding Estimated (in millions) Gains Losses Fair Value Gains Losses (a) Fair Value NDTF Cash and cash equivalents $ — $ — $ 33 $ — $ — $ 48 Equity securities 294 3 427 231 5 356 Corporate debt securities 2 — 62 1 1 54 Municipal bonds — — 1 — — 1 U.S. government bonds 3 1 214 3 1 251 Other debt securities — — 2 — — 3 Total NDTF (a) $ 299 $ 4 $ 739 $ 235 $ 7 $ 713 Other Investments Cash and cash equivalents $ — $ — $ 1 $ — $ — $ 4 Municipal bonds 2 — 47 2 — 44 Total Other Investments $ 2 $ — $ 48 $ 2 $ — $ 48 Total Investments $ 301 $ 4 $ 787 $ 237 $ 7 $ 761 (a) During the year ended December 31, 2017 , Duke Energy Florida continued to receive reimbursements from the NDTF for costs related to ongoing decommissioning activity of the Crystal River Unit 3 nuclear plant. The table below summarizes the maturity date for debt securities. (in millions) December 31, 2017 Due in one year or less $ 73 Due after one through five years 82 Due after five through 10 years 57 Due after 10 years 114 Total $ 326 Realized gains and losses, which were determined on a specific identification basis, from sales of AFS securities were as follows. Years Ended December 31, (in millions) 2017 2016 2015 Realized gains $ 11 $ 13 $ 7 Realized losses 8 9 2 DUKE ENERGY INDIANA The following table presents the estimated fair value of investments in AFS securities. December 31, 2017 December 31, 2016 Gross Gross Gross Gross Unrealized Unrealized Unrealized Unrealized Holding Holding Estimated Holding Holding Estimated (in millions) Gains Losses Fair Value Gains Losses (a) Fair Value Other Investments Equity securities $ 49 $ — $ 97 $ 33 $ — $ 79 Corporate debt securities — — 3 — — 2 Municipal bonds — 1 28 — 1 28 U.S. government bonds — — — — — 1 Total Other Investments $ 49 $ 1 $ 128 $ 33 $ 1 $ 110 Total Investments $ 49 $ 1 $ 128 $ 33 $ 1 $ 110 The table below summarizes the maturity date for debt securities. (in millions) December 31, 2017 Due in one year or less $ 5 Due after one through five years 12 Due after five through 10 years 7 Due after 10 years 7 Total $ 31 Realized gains and losses, which were determined on a specific identification basis, from sales of AFS securities were insignificant for the years ended December 31, 2017 , 2016 and 2015 .

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements	FAIR VALUE MEASUREMENTS Fair value is the exchange price to sell an asset or transfer a liability in an orderly transaction between market participants at the measurement date. The fair value definition focuses on an exit price versus the acquisition cost. Fair value measurements use market data or assumptions market participants would use in pricing the asset or liability, including assumptions about risk and the risks inherent in the inputs to the valuation technique. These inputs may be readily observable, corroborated by market data, or generally unobservable. Valuation techniques maximize the use of observable inputs and minimize use of unobservable inputs. A midmarket pricing convention (the midpoint price between bid and ask prices) is permitted for use as a practical expedient. Fair value measurements are classified in three levels based on the fair value hierarchy: Level 1 – Unadjusted quoted prices in active markets for identical assets or liabilities that the reporting entity can access at the measurement date. An active market is one in which transactions for an asset or liability occur with sufficient frequency and volume to provide ongoing pricing information. Level 2 – A fair value measurement utilizing inputs other than quoted prices included in Level 1 that are observable, either directly or indirectly, for an asset or liability. Inputs include (i) quoted prices for similar assets or liabilities in active markets, (ii) quoted prices for identical or similar assets or liabilities in markets that are not active, and (iii) inputs other than quoted market prices that are observable for the asset or liability, such as interest rate curves and yield curves observable at commonly quoted intervals, volatilities and credit spreads. A Level 2 measurement cannot have more than an insignificant portion of its valuation based on unobservable inputs. Instruments in this category include non-exchange-traded derivatives, such as over-the-counter forwards, swaps and options; certain marketable debt securities; and financial instruments traded in less than active markets. Level 3 – Any fair value measurement which includes unobservable inputs for more than an insignificant portion of the valuation. These inputs may be used with internally developed methodologies that result in management’s best estimate of fair value. Level 3 measurements may include longer-term instruments that extend into periods in which observable inputs are not available. Not Categorized – Certain investments are not categorized within the Fair Value hierarchy. These investments are measured based on the fair value of the underlying investments but may not be readily redeemable at that fair value. Fair value accounting guidance permits entities to elect to measure certain financial instruments that are not required to be accounted for at fair value, such as equity method investments or the company’s own debt, at fair value. The Duke Energy Registrants have not elected to record any of these items at fair value. Transfers between levels represent assets or liabilities that were previously (i) categorized at a higher level for which the inputs to the estimate became less observable or (ii) classified at a lower level for which the inputs became more observable during the period. The Duke Energy Registrant’s policy is to recognize transfers between levels of the fair value hierarchy at the end of the period. There were no transfers between levels during the years ended December 31, 2017 , 2016 and 2015 . In addition, for Piedmont, there were no transfers between levels during the two months ended December 31, 2016, and the years ended October 31, 2016, and 2015. Valuation methods of the primary fair value measurements disclosed below are as follows. Investments in equity securities The majority of investments in equity securities are valued using Level 1 measurements. Investments in equity securities are typically valued at the closing price in the principal active market as of the last business day of the quarter. Principal active markets for equity prices include published exchanges such as the New York Stock Exchange (NYSE) and the NASDAQ Stock Market. Foreign equity prices are translated from their trading currency using the currency exchange rate in effect at the close of the principal active market. There was no after-hours market activity that was required to be reflected in the reported fair value measurements. Investments in debt securities Most investments in debt securities are valued using Level 2 measurements because the valuations use interest rate curves and credit spreads applied to the terms of the debt instrument (maturity and coupon interest rate) and consider the counterparty credit rating. If the market for a particular fixed-income security is relatively inactive or illiquid, the measurement is Level 3. Commodity derivatives Commodity derivatives with clearinghouses are classified as Level 1. Other commodity derivatives, including Piedmont's natural gas supply contracts, are primarily valued using internally developed discounted cash flow models that incorporate forward price, adjustments for liquidity (bid-ask spread) and credit or non-performance risk (after reflecting credit enhancements such as collateral) and are discounted to present value. Pricing inputs are derived from published exchange transaction prices and other observable data sources. In the absence of an active market, the last available price may be used. If forward price curves are not observable for the full term of the contract and the unobservable period had more than an insignificant impact on the valuation, the commodity derivative is classified as Level 3. In isolation, increases (decreases) in natural gas forward prices result in favorable (unfavorable) fair value adjustments for gas purchase contracts; and increases (decreases) in electricity forward prices result in unfavorable (favorable) fair value adjustments for electricity sales contracts. Duke Energy regularly evaluates and validates pricing inputs used to estimate the fair value of natural gas commodity contracts by a market participant price verification procedure. This procedure provides a comparison of internal forward commodity curves to market participant generated curves. Interest rate derivatives Most over-the-counter interest rate contract derivatives are valued using financial models that utilize observable inputs for similar instruments and are classified as Level 2. Inputs include forward interest rate curves, notional amounts, interest rates and credit quality of the counterparties. Other fair value considerations See Note 11 for a discussion of the valuation of goodwill and intangible assets. See Note 2 related to the acquisition of Piedmont in 2016 and the purchase of NCEMPA's ownership interests in certain generating assets in 2015. DUKE ENERGY The following tables provide recorded balances for assets and liabilities measured at fair value on a recurring basis on the Consolidated Balance Sheets. Derivative amounts in the table below for all Duke Energy Registrants exclude cash collateral, which is disclosed in Note 14 . See Note 15 for additional information related to investments by major security type for the Duke Energy Registrants. December 31, 2017 (in millions) Total Fair Value Level 1 Level 2 Level 3 Not Categorized NDTF equity securities $ 4,914 $ 4,840 $ — $ — $ 74 NDTF debt securities 2,174 635 1,539 — — Other AFS equity securities 123 123 — — — Other trading and AFS debt securities 241 57 184 — — Derivative assets 51 3 20 28 — Total assets 7,503 5,658 1,743 28 74 Derivative liabilities (230 ) (2 ) (86 ) (142 ) — Net assets (liabilities) $ 7,273 $ 5,656 $ 1,657 $ (114 ) $ 74 December 31, 2016 (in millions) Total Fair Value Level 1 Level 2 Level 3 Not Categorized NDTF equity securities $ 4,106 $ 4,029 $ — $ — $ 77 NDTF debt securities 2,078 632 1,446 — — Other trading and AFS equity securities 104 104 — — — Other trading and AFS debt securities 266 75 186 5 — Derivative assets 162 5 136 21 — Total assets 6,716 4,845 1,768 26 77 Derivative liabilities (252 ) (2 ) (63 ) (187 ) — Net assets $ 6,464 $ 4,843 $ 1,705 $ (161 ) $ 77 The following tables provide reconciliations of beginning and ending balances of assets and liabilities measured at fair value using Level 3 measurements. Amounts included in earnings for derivatives are primarily included in Cost of natural gas on the Duke Energy Registrants' Consolidated Statements of Operations and Comprehensive Income. Amounts included in changes of net assets on the Duke Energy Registrants' Consolidated Balance Sheets are included in regulatory assets or liabilities. All derivative assets and liabilities are presented on a net basis. December 31, 2017 December 31, 2016 (in millions) Investments Derivatives (net) Total Investments Derivatives (net) Total Balance at beginning of period $ 5 $ (166 ) $ (161 ) $ 5 $ 10 $ 15 Total pretax realized or unrealized gains included in comprehensive income 1 — 1 — — — Derivative liability resulting from the acquisition of Piedmont — — — — (187 ) (187 ) Purchases, sales, issuances and settlements: Purchases — 55 55 — 33 33 Sales (6 ) — (6 ) — — — Settlements — (47 ) (47 ) — (28 ) (28 ) Total gains included on the Consolidated Balance Sheet — 44 44 — 6 6 Balance at end of period $ — $ (114 ) $ (114 ) $ 5 $ (166 ) $ (161 ) DUKE ENERGY CAROLINAS The following tables provide recorded balances for assets and liabilities measured at fair value on a recurring basis on the Consolidated Balance Sheets. December 31, 2017 (in millions) Total Fair Value Level 1 Level 2 Level 3 Not Categorized NDTF equity securities $ 2,692 $ 2,618 $ — $ — $ 74 NDTF debt securities 1,066 204 862 — — Derivative assets 2 — 2 — — Total assets 3,760 2,822 864 — 74 Derivative liabilities (35 ) (1 ) (34 ) — — Net assets $ 3,725 $ 2,821 $ 830 $ — $ 74 December 31, 2016 (in millions) Total Fair Value Level 1 Level 2 Level 3 Not Categorized NDTF equity securities $ 2,245 $ 2,168 $ — $ — $ 77 NDTF debt securities 1,013 178 835 — — Other AFS debt securities 3 — — 3 — Derivative assets 33 — 33 — — Total assets 3,294 2,346 868 3 77 Derivative liabilities (16 ) — (16 ) — — Net assets $ 3,278 $ 2,346 $ 852 $ 3 $ 77 The following table provides reconciliations of beginning and ending balances of assets and liabilities measured at fair value using Level 3 measurements. Investments Years Ended December 31, (in millions) 2017 2016 Balance at beginning of period $ 3 $ 3 Total pretax realized or unrealized gains included in comprehensive income 1 — Purchases, sales, issuances and settlements: Sales (4 ) — Balance at end of period $ — $ 3 PROGRESS ENERGY The following table provides recorded balances for assets and liabilities measured at fair value on a recurring basis on the Consolidated Balance Sheets. December 31, 2017 December 31, 2016 (in millions) Total Fair Value Level 1 Level 2 Total Fair Value Level 1 Level 2 NDTF equity securities $ 2,222 $ 2,222 $ — $ 1,861 $ 1,861 $ — NDTF debt securities 1,108 431 677 1,065 454 611 Other AFS debt securities 59 12 47 65 21 44 Derivative assets 3 1 2 85 — 85 Total assets 3,392 2,666 726 3,076 2,336 740 Derivative liabilities (36 ) (1 ) (35 ) (25 ) — (25 ) Net assets $ 3,356 $ 2,665 $ 691 $ 3,051 $ 2,336 $ 715 DUKE ENERGY PROGRESS The following table provides recorded balances for assets and liabilities measured at fair value on a recurring basis on the Consolidated Balance Sheets. December 31, 2017 December 31, 2016 (in millions) Total Fair Value Level 1 Level 2 Total Fair Value Level 1 Level 2 NDTF equity securities $ 1,795 $ 1,795 $ — $ 1,505 $ 1,505 $ — NDTF debt securities 796 243 553 708 207 501 Other AFS debt securities 1 1 — 1 1 — Derivative assets 2 1 1 46 — 46 Total assets 2,594 2,040 554 2,260 1,713 547 Derivative liabilities (18 ) (1 ) (17 ) (7 ) — (7 ) Net assets $ 2,576 $ 2,039 $ 537 $ 2,253 $ 1,713 $ 540 DUKE ENERGY FLORIDA The following table provides recorded balances for assets and liabilities measured at fair value on a recurring basis on the Consolidated Balance Sheets. December 31, 2017 December 31, 2016 (in millions) Total Fair Value Level 1 Level 2 Total Fair Value Level 1 Level 2 NDTF equity securities $ 427 $ 427 $ — $ 356 $ 356 $ — NDTF debt securities 312 188 124 357 247 110 Other AFS debt securities 48 1 47 48 4 44 Derivative assets 1 — 1 39 — 39 Total assets 788 616 172 800 607 193 Derivative liabilities (12 ) — (12 ) (12 ) — (12 ) Net assets $ 776 $ 616 $ 160 $ 788 $ 607 $ 181 DUKE ENERGY OHIO The following table provides recorded balances for assets and liabilities measured at fair value on a recurring basis on the Consolidated Balance Sheets. December 31, 2017 December 31, 2016 (in millions) Total Fair Value Level 2 Level 3 Total Fair Value Level 2 Level 3 Derivative assets $ 1 $ — $ 1 $ 5 $ — $ 5 Derivative liabilities (5 ) (5 ) — (6 ) (6 ) — Net (liabilities) assets $ (4 ) $ (5 ) $ 1 $ (1 ) $ (6 ) $ 5 The following table provides a reconciliation of beginning and ending balances of assets and liabilities measured at fair value using Level 3 measurements. Derivatives (net) Years Ended December 31, (in millions) 2017 2016 Balance at beginning of period $ 5 $ 3 Purchases, sales, issuances and settlements: Purchases 3 5 Settlements (4 ) (5 ) Total gains included on the Consolidated Balance Sheet (3 ) 2 Balance at end of period $ 1 $ 5 DUKE ENERGY INDIANA The following table provides recorded balances for assets and liabilities measured at fair value on a recurring basis on the Consolidated Balance Sheets. December 31, 2017 December 31, 2016 (in millions) Total Fair Value Level 1 Level 2 Level 3 Total Fair Value Level 1 Level 2 Level 3 Other AFS equity securities $ 97 $ 97 $ — $ — $ 79 $ 79 $ — $ — Other AFS debt securities 31 — 31 — 31 — 31 — Derivative assets 27 — — 27 16 — — 16 Total assets 155 97 31 27 126 79 31 16 Derivative liabilities — — — — (2 ) (2 ) — — Net assets $ 155 $ 97 $ 31 $ 27 $ 124 $ 77 $ 31 $ 16 The following table provides a reconciliation of beginning and ending balances of assets and liabilities measured at fair value using Level 3 measurements. Derivatives (net) Years Ended December 31, (in millions) 2017 2016 Balance at beginning of period $ 16 $ 7 Purchases, sales, issuances and settlements: Purchases 52 29 Settlements (43 ) (24 ) Total gains included on the Consolidated Balance Sheet 2 4 Balance at end of period $ 27 $ 16 PIEDMONT The following table provides recorded balances for assets and liabilities measured at fair value on a recurring basis on the Consolidated Balance Sheets. December 31, 2017 December 31, 2016 (in millions) Total Fair Value Level 1 Level 3 Total Fair Value Level 1 Level 3 Other trading equity securities $ — $ — $ — $ 4 $ 4 $ — Other trading debt securities 1 1 — 1 1 — Derivative assets 2 2 — 3 3 — Total assets 3 3 — 8 8 — Derivative liabilities (142 ) — (142 ) (187 ) — (187 ) Net assets $ (139 ) $ 3 $ (142 ) $ (179 ) $ 8 $ (187 ) The following table provides a reconciliation of beginning and ending balances of assets and liabilities measured at fair value using Level 3 measurements. Derivatives (net) Year Ended Two Months Ended Year Ended (in millions) December 31, 2017 December 31, 2016 October 31, 2016 Balance at beginning of period $ (187 ) $ (188 ) $ — Total gains (losses) and settlements 45 1 (188 ) Balance at end of period $ (142 ) $ (187 ) $ (188 ) QUANTITATIVE INFORMATION ABOUT UNOBSERVABLE INPUTS The following tables include quantitative information about the Duke Energy Registrants' derivatives classified as Level 3. December 31, 2017 Fair Value Investment Type (in millions) Valuation Technique Unobservable Input Range Duke Energy Ohio FTRs $ 1 RTO auction pricing FTR price – per MWh $ 0.07 – $ 1.41 Duke Energy Indiana FTRs 27 RTO auction pricing FTR price – per MWh (0.77 ) – 7.44 Piedmont Natural gas contracts (142 ) Discounted cash flow Forward natural gas curves - price per MMBtu 2.10 – 2.88 Duke Energy Total Level 3 derivatives $ (114 ) December 31, 2016 Fair Value Investment Type (in millions) Valuation Technique Unobservable Input Range Duke Energy Ohio FTRs $ 5 RTO auction pricing FTR price – per MWh 0.77 – 3.52 Duke Energy Indiana FTRs 16 RTO auction pricing FTR price – per MWh (0.83 ) – 9.32 Piedmont Natural gas contracts (187 ) Discounted cash flow Forward natural gas curves - price per MMBtu 2.31 – 4.18 Duke Energy Total Level 3 derivatives $ (166 ) OTHER FAIR VALUE DISCLOSURES The fair value and book value of long-term debt, including current maturities, is summarized in the following table. Estimates determined are not necessarily indicative of amounts that could have been settled in current markets. Fair value of long-term debt uses Level 2 measurements. December 31, 2017 December 31, 2016 (in millions) Book Value Fair Value Book Value Fair Value Duke Energy $ 52,279 $ 55,331 $ 47,895 $ 49,161 Duke Energy Carolinas 10,103 11,372 9,603 10,494 Progress Energy 17,837 20,000 17,541 19,107 Duke Energy Progress 7,357 7,992 7,011 7,357 Duke Energy Florida 7,095 7,953 6,125 6,728 Duke Energy Ohio 2,067 2,249 1,884 2,020 Duke Energy Indiana 3,783 4,464 3,786 4,260 Piedmont 2,037 2,209 1,821 1,933 At both December 31, 2017 , and December 31, 2016 , fair value of cash and cash equivalents, accounts and notes receivable, accounts payable, notes payable and commercial paper and nonrecourse notes payable of VIEs are not materially different from their carrying amounts because of the short-term nature of these instruments and/or because the stated rates approximate market rates.

Variable Interest Entities

Variable Interest Entities	12 Months Ended
	Dec. 31, 2017
Variable Interest Entities [Abstract]
Variable Interest Entities	VARIABLE INTEREST ENTITIES A VIE is an entity that is evaluated for consolidation using more than a simple analysis of voting control. The analysis to determine whether an entity is a VIE considers contracts with an entity, credit support for an entity, the adequacy of the equity investment of an entity and the relationship of voting power to the amount of equity invested in an entity. This analysis is performed either upon the creation of a legal entity or upon the occurrence of an event requiring reevaluation, such as a significant change in an entity’s assets or activities. A qualitative analysis of control determines the party that consolidates a VIE. This assessment is based on (i) what party has the power to direct the activities of the VIE that most significantly impact its economic performance and (ii) what party has rights to receive benefits or is obligated to absorb losses that could potentially be significant to the VIE. The analysis of the party that consolidates a VIE is a continual reassessment. CONSOLIDATED VIEs The obligations of these VIEs discussed in the following paragraphs are nonrecourse to the Duke Energy Registrants. The registrants have no requirement to provide liquidity to, purchase assets of or guarantee performance of these VIEs unless noted in the following paragraphs. No financial support was provided to any of the consolidated VIEs during the years ended December 31, 2017 , 2016 and 2015 , or is expected to be provided in the future, that was not previously contractually required. Receivables Financing – DERF/DEPR/DEFR Duke Energy Receivables Finance Company, LLC (DERF), Duke Energy Progress Receivables, LLC (DEPR) and Duke Energy Florida Receivables, LLC (DEFR) are bankruptcy remote, special purpose subsidiaries of Duke Energy Carolinas, Duke Energy Progress and Duke Energy Florida, respectively. DERF, DEPR and DEFR are wholly owned limited liability companies with separate legal existence from their parent companies and their assets are not generally available to creditors of their parent companies. On a revolving basis, DERF, DEPR and DEFR buy certain accounts receivable arising from the sale of electricity and related services from their parent companies. DERF, DEPR and DEFR borrow amounts under credit facilities to buy these receivables. Borrowing availability from the credit facilities is limited to the amount of qualified receivables purchased. The sole source of funds to satisfy the related debt obligations is cash collections from the receivables. Amounts borrowed under the credit facilities are reflected on the Consolidated Balance Sheets as Long-Term Debt. The most significant activity that impacts the economic performance of DERF, DEPR and DEFR are the decisions made to manage delinquent receivables. Duke Energy Carolinas, Duke Energy Progress and Duke Energy Florida consolidate DERF, DEPR and DEFR, respectively, as they make those decisions. Receivables Financing – CRC CRC is a bankruptcy remote, special purpose entity indirectly owned by Duke Energy. On a revolving basis, CRC buys certain accounts receivable arising from the sale of electricity, natural gas and related services from Duke Energy Ohio and Duke Energy Indiana. CRC borrows amounts under a credit facility to buy the receivables from Duke Energy Ohio and Duke Energy Indiana. Borrowing availability from the credit facility is limited to the amount of qualified receivables sold to CRC. The sole source of funds to satisfy the related debt obligation is cash collections from the receivables. Amounts borrowed under the credit facility are reflected on Duke Energy's Consolidated Balance Sheets as Long-Term Debt. The proceeds Duke Energy Ohio and Duke Energy Indiana receive from the sale of receivables to CRC are typically 75 percent cash and 25 percent in the form of a subordinated note from CRC. The subordinated note is a retained interest in the receivables sold. Depending on collection experience, additional equity infusions to CRC may be required by Duke Energy to maintain a minimum equity balance of $3 million . CRC is considered a VIE because (i) equity capitalization is insufficient to support its operations, (ii) power to direct the activities that most significantly impact the economic performance of the entity are not performed by the equity holder and (iii) deficiencies in net worth of CRC are funded by Duke Energy. The most significant activities that impact the economic performance of CRC are decisions made to manage delinquent receivables. Duke Energy consolidates CRC as it makes these decisions. Neither Duke Energy Ohio nor Duke Energy Indiana consolidate CRC. Receivables Financing – Credit Facilities The following table outlines amounts and expiration dates of the credit facilities described above. Duke Energy Duke Energy Duke Energy Duke Energy Carolinas Progress Florida CRC DERF DEPR DEFR Expiration date December 2020 December 2020 February 2019 April 2019 Credit facility amount (in millions) $ 325 $ 450 $ 300 $ 225 Amounts borrowed at December 31, 2017 325 450 300 225 Amounts borrowed at December 31, 2016 325 425 300 225 Nuclear Asset-Recovery Bonds – DEFPF Duke Energy Florida Project Finance, LLC (DEFPF) is a bankruptcy remote, wholly owned special purpose subsidiary of Duke Energy Florida. DEFPF was formed in 2016 for the sole purpose of issuing nuclear asset-recovery bonds to finance Duke Energy Florida's unrecovered regulatory asset related to Crystal River Unit 3. In June 2016, DEFPF issued $1,294 million of senior secured bonds and used the proceeds to acquire nuclear asset-recovery property from Duke Energy Florida. The nuclear asset-recovery property acquired includes the right to impose, bill, collect and adjust a non-bypassable nuclear asset-recovery charge from all Duke Energy Florida retail customers until the bonds are paid in full and all financing costs have been recovered. The nuclear asset-recovery bonds are secured by the nuclear asset-recovery property and cash collections from the nuclear asset-recovery charges are the sole source of funds to satisfy the debt obligation. The bondholders have no recourse to Duke Energy Florida. For additional information see Notes 4 and 6 . DEFPF is considered a VIE primarily because the equity capitalization is insufficient to support its operations. Duke Energy Florida has the power to direct the significant activities of the VIE as described above and therefore Duke Energy Florida is considered the primary beneficiary and consolidates DEFPF. The following table summarizes the impact of DEFPF on Duke Energy Florida's Consolidated Balance Sheets. (in millions) December 31, 2017 December 31, 2016 Receivables of VIEs $ 4 $ 6 Regulatory Assets: Current 51 50 Current Assets: Other 40 53 Other Noncurrent Assets: Regulatory assets 1,091 1,142 Current Liabilities: Other 10 17 Current maturities of long-term debt 53 62 Long-Term Debt 1,164 1,217 Commercial Renewables Certain of Duke Energy’s renewable energy facilities are VIEs due to Duke Energy issuing guarantees for debt service and operations and maintenance reserves in support of debt financings. Assets are restricted and cannot be pledged as collateral or sold to third parties without prior approval of debt holders. The activities that most significantly impact the economic performance of these renewable energy facilities were decisions associated with siting, negotiating PPAs, engineering, procurement and construction and decisions associated with ongoing operations and maintenance-related activities. Duke Energy consolidates the entities as it is responsible for all of these decisions. The table below presents material balances reported on Duke Energy's Consolidated Balance Sheets related to renewables VIEs. (in millions) December 31, 2017 December 31, 2016 Current Assets: Other $ 174 $ 223 Property, plant and equipment, cost 3,923 3,419 Accumulated depreciation and amortization (591 ) (453 ) Current maturities of long-term debt 170 198 Long-Term Debt 1,700 1,097 Other Noncurrent Liabilities: Deferred income taxes (148 ) 275 Other Noncurrent Liabilities: Other 241 252 NON-CONSOLIDATED VIEs The following tables summarize the impact of non-consolidated VIEs on the Consolidated Balance Sheets. December 31, 2017 Duke Energy Duke Duke Pipeline Commercial Other Energy Energy (in millions) Investments Renewables VIEs (a) Total Ohio Indiana Receivables from affiliated companies $ — $ — $ — $ — $ 87 $ 106 Investments in equity method unconsolidated affiliates 697 180 42 919 — — Other noncurrent assets 17 — — 17 — — Total assets $ 714 $ 180 $ 42 $ 936 $ 87 $ 106 Taxes accrued (29 ) — — (29 ) — — Other current liabilities — — 4 4 — — Deferred income taxes 42 — — 42 — — Other noncurrent liabilities — — 12 12 — — Total liabilities $ 13 $ — $ 16 $ 29 $ — $ — Net assets $ 701 $ 180 $ 26 $ 907 $ 87 $ 106 (a) Duke Energy holds a 50 percent equity interest in Duke-American Transmission Company, LLC (DATC). As of December 31, 2016, DATC was considered a VIE due to having insufficient equity to finance its own activities without subordinated financial support. However, DATC is no longer considered a VIE based on sufficient equity to finance its own activities, and, therefore, is no longer considered a VIE as of December 31, 2017. Duke Energy's investment in DATC was $46 million at December 31, 2017. December 31, 2016 Duke Energy Duke Duke Pipeline Commercial Energy Energy (in millions) Investments Renewables Other Total Ohio Indiana Piedmont (a) Receivables from affiliated companies $ — $ — $ — $ — $ 82 $ 101 $ — Investments in equity method unconsolidated affiliates 487 174 90 751 — — 139 Other noncurrent assets 12 — — 12 — — — Total assets $ 499 $ 174 $ 90 $ 763 $ 82 $ 101 $ 139 Other current liabilities — — 3 3 — — — Other noncurrent liabilities — — 13 13 — — 4 Total liabilities $ — $ — $ 16 $ 16 $ — $ — $ 4 Net assets $ 499 $ 174 $ 74 $ 747 $ 82 $ 101 $ 135 (a) In April 2017, Piedmont transferred its non-consolidated VIE investments to a wholly owned subsidiary of Duke Energy. See Note 12 and the "Pipeline Investments" section below for additional detail. The Duke Energy Registrants are not aware of any situations where the maximum exposure to loss significantly exceeds the carrying values shown above except for the power purchase agreement with OVEC, which is discussed below, and various guarantees, some of which are reflected in the table above as Other noncurrent liabilities. For more information on various guarantees, refer to Note 7 . Pipeline Investments Duke Energy has investments in various joint ventures with pipeline projects currently under construction. These entities are considered VIEs due to having insufficient equity to finance their own activities without subordinated financial support. Duke Energy does not have the power to direct the activities that most significantly impact the economic performance, the obligation to absorb losses or the right to receive benefits of these VIEs and therefore does not consolidate these entities. The table below presents Duke Energy's ownership interest and investment balance in in these joint ventures. Investment Amount (in millions) Ownership December 31, December 31, Entity Name Interest 2017 2016 ACP 47 % $ 397 $ 265 Sabal Trail 7.5 % 219 140 Constitution 24 % 81 82 Total $ 697 $ 487 Commercial Renewables Duke Energy has investments in various renewable energy project entities. Some of these entities are VIEs due to Duke Energy issuing guarantees for debt service and operations and maintenance reserves in support of debt financings. Duke Energy does not consolidate these VIEs because power to direct and control key activities is shared jointly by Duke Energy and other owners. Other VIEs Duke Energy holds a 50 percent equity interest in Pioneer. Pioneer is considered a VIE due to having insufficient equity to finance their own activities without subordinated financial support. The activities that most significantly impact Pioneer's economic performance are decisions related to the development of new transmission facilities. The power to direct these activities is jointly and equally shared by Duke Energy and the other joint venture partner, American Electric Power, therefore Duke Energy does not consolidate Pioneer. OVEC Duke Energy Ohio’s 9 percent ownership interest in OVEC is considered a non-consolidated VIE due to having insufficient equity to finance their activities without subordinated financial support. As a counterparty to an inter-company power agreement (ICPA), Duke Energy Ohio has a contractual arrangement to buy power from OVEC’s power plants through June 2040 commensurate with its power participation ratio, which is equivalent to Duke Energy Ohio's ownership interest. Costs, including fuel, operating expenses, fixed costs, debt amortization, and interest expense are allocated to counterparties to the ICPA based on their power participation ratio. The value of the ICPA is subject to variability due to fluctuation in power prices and changes in OVEC's cost of business, including costs associated with its 2,256 MW of coal-fired generation capacity. Deterioration in the credit quality, or bankruptcy of one or more parties to the ICPA could increase the costs of OVEC. In addition, certain proposed environmental rulemaking could result in future increased cost allocations. CRC See discussion under Consolidated VIEs for additional information related to CRC. Amounts included in Receivables from affiliated companies in the above table for Duke Energy Ohio and Duke Energy Indiana reflect their retained interest in receivables sold to CRC. These subordinated notes held by Duke Energy Ohio and Duke Energy Indiana are stated at fair value. Carrying values of retained interests are determined by allocating carrying value of the receivables between assets sold and interests retained based on relative fair value. The allocated bases of the subordinated notes are not materially different than their face value because (i) the receivables generally turnover in less than two months, (ii) credit losses are reasonably predictable due to the broad customer base and lack of significant concentration and (iii) the equity in CRC is subordinate to all retained interests and thus would absorb losses first. The hypothetical effect on fair value of the retained interests assuming both a 10 percent and a 20 percent unfavorable variation in credit losses or discount rates is not material due to the short turnover of receivables and historically low credit loss history. Interest accrues to Duke Energy Ohio and Duke Energy Indiana on the retained interests using the acceptable yield method. This method generally approximates the stated rate on the notes since the allocated basis and the face value are nearly equivalent. An impairment charge is recorded against the carrying value of both retained interests and purchased beneficial interest whenever it is determined that an OTTI has occurred. Key assumptions used in estimating fair value are detailed in the following table. Duke Energy Ohio Duke Energy Indiana 2017 2016 2017 2016 Anticipated credit loss ratio 0.5 % 0.5 % 0.3 % 0.3 % Discount rate 2.1 % 1.5 % 2.1 % 1.5 % Receivable turnover rate 13.5 % 13.3 % 10.7 % 10.6 % The following table shows the gross and net receivables sold. Duke Energy Ohio Duke Energy Indiana (in millions) 2017 2016 2017 2016 Receivables sold $ 273 $ 267 $ 312 $ 306 Less: Retained interests 87 82 106 101 Net receivables sold $ 186 $ 185 $ 206 $ 205 The following table shows sales and cash flows related to receivables sold. Duke Energy Ohio Duke Energy Indiana Years Ended December 31, Years Ended December 31, (in millions) 2017 2016 2015 2017 2016 2015 Sales Receivables sold $ 1,879 $ 1,926 $ 1,963 $ 2,711 $ 2,635 $ 2,627 Loss recognized on sale 10 9 9 12 11 11 Cash Flows Cash proceeds from receivables sold 1,865 1,882 1,995 2,694 2,583 2,670 Collection fees received 1 1 1 1 1 1 Return received on retained interests 3 2 3 7 5 5 Cash flows from the sales of receivables are reflected within Cash Flows From Operating Activities on Duke Energy Ohio’s and Duke Energy Indiana’s Consolidated Statements of Cash Flows. Collection fees received in connection with servicing transferred accounts receivable are included in Operation, maintenance and other on Duke Energy Ohio’s and Duke Energy Indiana’s Consolidated Statements of Operations and Comprehensive Income. The loss recognized on sales of receivables is calculated monthly by multiplying receivables sold during the month by the required discount. The required discount is derived monthly utilizing a three-year weighted average formula that considers charge-off history, late charge history and turnover history on the sold receivables, as well as a component for the time value of money. The discount rate, or component for the time value of money, is the prior month-end LIBOR plus a fixed rate of 1.00 percent .

Common Stock

Common Stock	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Common Stock	COMMON STOCK Basic Earnings Per Share (EPS) is computed by dividing net income attributable to Duke Energy common stockholders, as adjusted for distributed and undistributed earnings allocated to participating securities, by the weighted average number of common shares outstanding during the period. Diluted EPS is computed by dividing net income attributable to Duke Energy common stockholders, as adjusted for distributed and undistributed earnings allocated to participating securities, by the diluted weighted average number of common shares outstanding during the period. Diluted EPS reflects the potential dilution that could occur if securities or other agreements to issue common shares, such as stock options and equity forward sale agreements, were exercised or settled. Duke Energy’s participating securities are restricted stock units that are entitled to dividends declared on Duke Energy common stock during the restricted stock unit’s vesting periods. The following table presents Duke Energy’s basic and diluted EPS calculations and reconciles the weighted average number of common stock outstanding to the diluted weighted average number of common stock outstanding. Years Ended December 31, (in millions, except per share amounts) 2017 2016 2015 Income from continuing operations attributable to Duke Energy common stockholders excluding impact of participating securities $ 3,059 $ 2,567 $ 2,640 Weighted average shares outstanding – basic 700 691 694 Weighted average shares outstanding – diluted 700 691 694 Earnings per share from continuing operations attributable to Duke Energy common stockholders Basic $ 4.37 $ 3.71 $ 3.80 Diluted $ 4.37 $ 3.71 $ 3.80 Potentially dilutive items excluded from the calculation (a) 2 2 2 Dividends declared per common share $ 3.49 $ 3.36 $ 3.24 (a) Performance stock awards were not included in the dilutive securities calculation because the performance measures related to the awards had not been met. Equity Distribution Agreement On February 20, 2018, Duke Energy filed a prospectus supplement and executed an Equity Distribution Agreement (the EDA) under which it may sell up to $1 billion of its common stock through an at-the-market offering program, including an equity forward sales component. The EDA was entered into with Wells Fargo Securities, LLC, Citigroup Global Markets Inc., and J.P. Morgan Securities LLC (the Agents). Under the terms of the EDA, Duke Energy may issue and sell, through either of the Agents, shares of common stock during the period ending September 23, 2019. In addition to the issuance and sales of shares by Duke Energy through the Agents, Duke Energy may enter into Equity Forward Agreements with affiliates of the Agents as Forward Purchasers. There were no transactions under the EDA from the time of execution of the EDA to the filing of this document. Stock Issuance In March 2016, Duke Energy marketed an equity offering of 10.6 million shares of common stock. In lieu of issuing equity at the time of the offering, Duke Energy entered into Equity Forwards with Barclays. The Equity Forwards required Duke Energy to either physically settle the transactions by issuing 10.6 million shares, or net settle in whole or in part through the delivery or receipt of cash or shares. On October 5, 2016, following the close of the Piedmont acquisition, Duke Energy physically settled the Equity Forwards in full by delivering 10.6 million shares of common stock in exchange for net cash proceeds of approximately $723 million . The net proceeds were used to finance a portion of the Piedmont acquisition. As a result of the acquisition, all of Piedmont's issued and outstanding stock became the issued and outstanding shares of a wholly owned subsidiary of Duke Energy. See Note 2 for additional information related to the Piedmont acquisition. Accelerated Stock Repurchase Program On April 6, 2015, Duke Energy entered into agreements with each of Goldman, Sachs & Co. and JPMorgan Chase Bank, National Association (the Dealers) to repurchase a total of $1.5 billion of Duke Energy common stock under an accelerated stock repurchase program (the ASR). Duke Energy made payments of $750 million to each of the Dealers and was delivered 16.6 million shares, with a total fair value of $1.275 billion , which represented approximately 85 percent of the total number of shares of Duke Energy common stock expected to be repurchased under the ASR. The company recorded the $1.5 billion payment as a reduction to common stock as of April 6, 2015. In June 2015, the Dealers delivered 3.2 million additional shares to Duke Energy to complete the ASR. Approximately 19.8 million shares, in total, were delivered to Duke Energy and retired under the ASR at an average price of $75.75 per share. The final number of shares repurchased was based upon the average of the daily volume weighted average stock prices of Duke Energy’s common stock during the term of the program, less a discount.

Severance

Severance	12 Months Ended
	Dec. 31, 2017
Restructuring and Related Activities [Abstract]
Severance	SEVERANCE As part of its strategic planning processes, Duke Energy implemented targeted cost savings initiatives during 2016 and 2015 aimed at reducing operations and maintenance expense. The initiatives included efforts to reduce costs through the standardization of processes and systems, leveraging technology and workforce optimization throughout the company. During 2016, Duke Energy and Piedmont announced severance plans covering certain eligible employees whose employment will be involuntarily terminated without cause as a result of Duke Energy's acquisition of Piedmont. These reductions continue to be implemented and are a part of the synergies expected to be realized with the acquisition. Refer to Note 2 for additional information on the Piedmont acquisition. Severance benefit costs for initiatives and plans discussed above were accrued for a total of approximately 100 employees in 2017, 600 employees in 2016 and 900 employees in 2015. The following table presents the direct and allocated severance and related expenses recorded by the Duke Energy Registrants. Amounts are included within Operation, maintenance and other on the Consolidated Statements of Operations. Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont (a) Year Ended December 31, 2017 $ 15 $ 2 $ 2 $ 1 $ 1 $ — $ 1 $ 9 Year Ended December 31, 2016 118 39 40 23 17 3 7 Year Ended December 31, 2015 142 93 36 28 8 2 6 (a) Piedmont severance benefit costs were $3 million for the two months ended December 31, 2016, and $19 million for the year ended October 31, 2016. Piedmont did not record any severance benefit costs for the year ended October 31, 2015. The table below presents the severance liability for past and ongoing severance plans including the plans described above. Amounts for Duke Energy Indiana and Duke Energy Ohio are not material. Duke Duke Duke Duke Energy Progress Energy Energy (in millions) Energy Carolinas Energy Progress Florida Piedmont Balance at December 31, 2016 $ 79 $ 13 $ 14 $ 6 $ 8 $ 20 Provision/Adjustments 17 2 — — — 9 Cash Reductions (77 ) (10 ) (12 ) (5 ) (8 ) (24 ) Balance at December 31, 2017 $ 19 $ 5 $ 2 $ 1 $ — $ 5

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	STOCK-BASED COMPENSATION The Duke Energy Corporation 2015 Long-Term Incentive Plan (the 2015 Plan) provides for the grant of stock-based compensation awards to employees and outside directors. The 2015 Plan reserves 10 million shares of common stock for issuance. Duke Energy has historically issued new shares upon exercising or vesting of share-based awards. However, Duke Energy may use a combination of new share issuances and open market repurchases for share-based awards that are exercised or vest in the future. Duke Energy has not determined with certainty the amount of such new share issuances or open market repurchases. The following table summarizes the total expense recognized by the Duke Energy Registrants, net of tax, for stock-based compensation. Years Ended December 31, (in millions) 2017 2016 2015 Duke Energy $ 43 $ 35 $ 38 Duke Energy Carolinas 15 12 14 Progress Energy 16 12 14 Duke Energy Progress 10 7 9 Duke Energy Florida 6 5 5 Duke Energy Ohio 3 2 2 Duke Energy Indiana 4 3 4 Piedmont (a) 3 (a) See discussion below for information on Piedmont's pre-merger stock-based compensation plans. Duke Energy's pretax stock-based compensation costs, the tax benefit associated with stock-based compensation expense and stock-based compensation costs capitalized are included in the following table. Years Ended December 31, (in millions) 2017 2016 2015 Restricted stock unit awards $ 41 $ 36 $ 38 Performance awards 27 19 23 Pretax stock-based compensation cost $ 68 $ 55 $ 61 Tax benefit associated with stock-based compensation expense $ 25 $ 20 $ 23 Stock-based compensation costs capitalized 4 2 3 RESTRICTED STOCK UNIT AWARDS Restricted stock unit (RSU) awards generally vest over periods from immediate to three years . Fair value amounts are based on the market price of Duke Energy's common stock on the grant date. The following table includes information related to restricted stock unit awards. Years Ended December 31, 2017 2016 2015 Shares awarded (in thousands) 583 684 524 Fair value (in millions) $ 47 $ 52 $ 41 The following table summarizes information about restricted stock unit awards outstanding. Weighted Average Shares Grant Date Fair Value (in thousands) (per share) Outstanding at December 31, 2016 1,139 $ 76 Granted 583 80 Vested (553 ) 76 Forfeited (48 ) 78 Outstanding at December 31, 2017 1,121 78 Restricted stock unit awards expected to vest 1,094 78 The total grant date fair value of shares vested during the years ended December 31, 2017 , 2016 and 2015 was $42 million , $38 million and $41 million , respectively. At December 31, 2017 , Duke Energy had $29 million of unrecognized compensation cost, which is expected to be recognized over a weighted average period of twenty-three months . PERFORMANCE AWARDS Stock-based performance awards generally vest after three years if performance targets are met. Performance awards granted in 2017 , 2016 and 2015 contain market conditions based on the total shareholder return (TSR) of Duke Energy stock relative to a predefined peer group (relative TSR). These awards are valued using a path-dependent model that incorporates expected relative TSR into the fair value determination of Duke Energy’s performance-based share awards. The model uses three-year historical volatilities and correlations for all companies in the predefined peer group, including Duke Energy, to simulate Duke Energy’s relative TSR as of the end of the performance period. For each simulation, Duke Energy’s relative TSR associated with the simulated stock price at the end of the performance period plus expected dividends within the period results in a value per share for the award portfolio. The average of these simulations is the expected portfolio value per share. Actual life to date results of Duke Energy’s relative TSR for each grant are incorporated within the model. For performance awards granted in 2017 , the model used a risk-free interest rate of 1.5 percent , which reflects the yield on three-year Treasury bonds as of the grant date, and an expected volatility of 17.2 percent based on Duke Energy's historical volatility over three years using daily stock prices. In addition to TSR, performance awards granted in 2017 and 2016 contain a performance condition based on Duke Energy's cumulative adjusted EPS. Performance awards granted in 2017 also contain a performance condition based on the total incident case rate, one of our key employee safety metrics. The actual number of shares issued will range from zero to 200 percent of target shares depending on the level of performance achieved. The following table includes information related to stock-based performance awards. Years Ended December 31, 2017 2016 2015 Shares granted assuming target performance (in thousands) 461 338 321 Fair value (in millions) $ 37 $ 25 $ 26 The following table summarizes information about stock-based performance awards outstanding and assumes payout at the target level. Weighted Average Shares Grant Date Fair Value (in thousands) (per share) Outstanding at December 31, 2016 862 $ 75 Granted 461 81 Forfeited (258 ) 69 Outstanding at December 31, 2017 1,065 79 Stock-based performance awards expected to vest 1,034 79 No performance awards vested during the year ended December 31, 2017 . The total grant date fair value of shares vested during the years ended December 31, 2016 and 2015 was $25 million and $26 million , respectively. At December 31, 2017 , Duke Energy had $34 million of unrecognized compensation cost, which is expected to be recognized over a weighted average period of twenty-three months . STOCK OPTIONS Stock options, when granted, have a maximum option term of 10 years and with an exercise price not less than the market price of Duke Energy's common stock on the grant date. There were no stock options granted or exercised during the year ended December 31, 2017 . There were no stock options outstanding at December 31, 2017 . The following table summarizes additional information related to stock options exercised and granted. Years Ended December 31, (in millions) 2016 2015 Intrinsic value of options exercised $ 1 $ 5 Tax benefit related to options exercised — 2 Cash received from options exercised 7 17 PIEDMONT Prior to Duke Energy's acquisition of Piedmont, Piedmont had an incentive compensation plan that had a series of three-year performance and RSU awards for eligible officers and other participants. The Agreement and Plan of Merger (Merger Agreement) between Duke Energy and Piedmont provided for the conversion of the 2014-2016 and 2015-2017 performance awards and the nonvested 2016 RSU award into the right to receive $60 cash per share upon the close of the transaction. In December 2015, Piedmont's board of directors authorized the accelerated vesting, payment and taxation of the 2014-2016 and 2015-2017 performance awards, as well as the 2016 RSU award, at the election of the participant. Substantially all participants elected to accelerate the settlement of these awards. As a result of the settlement of these awards, 194 thousand shares of Piedmont shares were issued to participants, net of shares withheld for applicable federal and state income taxes, at a closing price of $56.85 and a fair value of $11 million . The 2016-2018 performance award cycle was approved subsequent to the Merger Agreement and was converted into a Duke Energy RSU award as discussed above at the consummation of the acquisition. Piedmont's stock-based compensation costs and the tax benefit associated with stock-based compensation expense are included in the following table. Piedmont's stock-based compensation costs were not material for the two months ended December 31, 2016. Years Ended October 31, (in millions) 2016 2015 Pretax stock-based compensation cost $ 16 $ 14 Tax benefit associated with stock-based compensation expense 6 4 Net of tax stock-based compensation cost $ 10 $ 10

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Employee Benefit Plans	EMPLOYEE BENEFIT PLANS DEFINED BENEFIT RETIREMENT PLANS Duke Energy and certain subsidiaries maintain, and the Subsidiary Registrants participate in, qualified, non-contributory defined benefit retirement plans. The Duke Energy plans cover most employees using a cash balance formula. Under a cash balance formula, a plan participant accumulates a retirement benefit consisting of pay credits based upon a percentage of current eligible earnings, age or age and years of service and interest credits. Certain employees are eligible for benefits that use a final average earnings formula. Under these final average earnings formulas, a plan participant accumulates a retirement benefit equal to the sum of percentages of their (i) highest three-year, four-year, or five-year average earnings, (ii) highest three-year, four-year, or five-year average earnings in excess of covered compensation per year of participation (maximum of 35 years ), (iii) highest three-year average earnings times years of participation in excess of 35 years . Duke Energy also maintains, and the Subsidiary Registrants participate in, non-qualified, non-contributory defined benefit retirement plans that cover certain executives. The qualified and non-qualified, non-contributory defined benefit plans are closed to new participants. Duke Energy approved plan amendments to restructure its qualified non-contributory defined benefit retirement plans, effective January 1, 2018. The restructuring involved (i) the spin-off of the majority of inactive participants from two plans into a separate inactive plan and (ii) the merger of the active participant portions of such plans, along with a pension plan acquired as part of the Piedmont transaction, into a single active plan. Benefits offered to the plan participants remain unchanged except that the Piedmont plan's final average earnings formula was frozen as of December 31, 2017, and affected participants were moved into the active plan's cash balance formula. Actuarial gains and losses associated with the Inactive Plan will be amortized over the remaining life expectancy of the inactive participants. The longer amortization period is expected to lower Duke Energy's 2018 pretax qualified pension plan expense by approximately $33 million . Duke Energy uses a December 31 measurement date for its defined benefit retirement plan assets and obligations. Net periodic benefit costs disclosed in the tables below represent the cost of the respective benefit plan for the periods presented. However, portions of the net periodic benefit costs disclosed in the tables below have been capitalized as a component of property, plant and equipment. Amounts presented in the tables below for the Subsidiary Registrants represent the amounts of pension and other post-retirement benefit cost allocated by Duke Energy for employees of the Subsidiary Registrants. Additionally, the Subsidiary Registrants are allocated their proportionate share of pension and post-retirement benefit cost for employees of Duke Energy’s shared services affiliate that provide support to the Subsidiary Registrants. These allocated amounts are included in the governance and shared service costs discussed in Note 13 . Duke Energy’s policy is to fund amounts on an actuarial basis to provide assets sufficient to meet benefit payments to be paid to plan participants. The following table includes information related to the Duke Energy Registrants’ contributions to its qualified defined benefit pension plans. Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont (a) Anticipated Contributions: Total anticipated 2018 contributions $ 148 $ 46 $ 45 $ 25 $ 20 $ — $ 8 $ 7 Contributions made January 2, 2018 141 46 45 25 20 — 8 — Contributions to be made in 2018 $ 7 $ — $ — $ — $ — $ — $ — $ 7 Contributions Made: 2017 $ 19 $ — $ — $ — $ — $ 4 $ — $ 11 2016 155 43 43 24 20 5 9 2015 302 91 83 42 40 8 19 (a) Piedmont contributed $10 million to its U.S. qualified defined benefit pension plan during the two months ended December 31, 2016, and for each of the years ended October 31, 2016, and 2015, respectively. QUALIFIED PENSION PLANS Components of Net Periodic Pension Costs Year Ended December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Service cost $ 159 $ 48 $ 45 $ 26 $ 19 $ 4 $ 9 $ 10 Interest cost on projected benefit obligation 328 79 100 47 53 18 26 14 Expected return on plan assets (545 ) (142 ) (167 ) (82 ) (85 ) (27 ) (42 ) (24 ) Amortization of actuarial loss 146 31 52 23 29 5 12 11 Amortization of prior service credit (24 ) (8 ) (3 ) (2 ) (1 ) (1 ) (2 ) (2 ) Settlement charge 12 — — — — — — 12 Other 8 2 2 1 1 — 1 1 Net periodic pension costs (a)(b) $ 84 $ 10 $ 29 $ 13 $ 16 $ (1 ) $ 4 $ 22 Year Ended December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Service cost $ 147 $ 48 $ 42 $ 24 $ 19 $ 4 $ 9 Interest cost on projected benefit obligation 335 86 106 49 55 19 28 Expected return on plan assets (519 ) (142 ) (168 ) (82 ) (84 ) (27 ) (42 ) Amortization of actuarial loss 134 33 51 23 29 4 11 Amortization of prior service (credit) (17 ) (8 ) (3 ) (2 ) (1 ) — (1 ) Settlement charge 3 — — — — — — Other 8 2 3 1 1 1 1 Net periodic pension costs (a)(b) $ 91 $ 19 $ 31 $ 13 $ 19 $ 1 $ 6 Year Ended December 31, 2015 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Service cost $ 159 $ 50 $ 44 $ 23 $ 20 $ 4 $ 10 Interest cost on projected benefit obligation 324 83 104 48 54 18 27 Expected return on plan assets (516 ) (139 ) (171 ) (79 ) (87 ) (26 ) (42 ) Amortization of actuarial loss 166 39 65 33 31 7 13 Amortization of prior service (credit) cost (15 ) (7 ) (3 ) (2 ) (1 ) — 1 Other 8 2 3 1 1 — 1 Net periodic pension costs (a)(b) $ 126 $ 28 $ 42 $ 24 $ 18 $ 3 $ 10 (a) Duke Energy amounts exclude $7 million , $8 million and $9 million for the years ended December 2017 , 2016 and 2015 , respectively, of regulatory asset amortization resulting from purchase accounting adjustments associated with Duke Energy's merger with Cinergy in April 2006. (b) Duke Energy Ohio amounts exclude $3 million , $4 million and $4 million for the years ended December 2017 , 2016 and 2015 , respectively, of regulatory asset amortization resulting from purchase accounting adjustments associated with Duke Energy's merger with Cinergy in April 2006. Piedmont Two Months Ended Years Ended October 31, (in millions) December 31, 2016 2016 2015 Service cost $ 2 $ 11 $ 11 Interest cost on projected benefit obligation 2 9 12 Expected return on plan assets (4 ) (24 ) (24 ) Amortization of actuarial loss 2 8 9 Amortization of prior service credit (1 ) (2 ) (2 ) Settlement charge 3 — — Net periodic pension costs $ 4 $ 2 $ 6 Amounts Recognized in Accumulated Other Comprehensive Income and Regulatory Assets Year Ended December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Regulatory assets, net (decrease) increase $ (212 ) $ (70 ) $ (49 ) $ (37 ) $ (11 ) $ 9 $ (19 ) $ (64 ) Accumulated other comprehensive loss (income) Deferred income tax expense $ — — 3 — — — — — Prior year service cost arising during the year 1 — — — — — — — Amortization of prior year actuarial losses (7 ) — (7 ) — — — — — Net amount recognized in accumulated other comprehensive income $ (6 ) $ — $ (4 ) $ — $ — $ — $ — $ — Year Ended December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Regulatory assets, net increase $ 214 $ 4 $ 34 $ 18 $ 16 $ 2 $ 9 Accumulated other comprehensive (income) loss Deferred income tax expense $ 4 $ — $ — $ — $ — $ — $ — Prior year service credit arising during the year (2 ) — — — — — — Amortization of prior year actuarial losses (7 ) — (1 ) — — — — Net amount recognized in accumulated other comprehensive income $ (5 ) $ — $ (1 ) $ — $ — $ — $ — Piedmont's regulatory asset net increase was $34 million , $35 million and $20 million for the two months ended December 31, 2016, and for the years ended October 31, 2016, and 2015, respectively. Reconciliation of Funded Status to Net Amount Recognized Year Ended December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Change in Projected Benefit Obligation Obligation at prior measurement date $ 8,131 $ 1,952 $ 2,512 $ 1,158 $ 1,323 $ 447 $ 658 $ 344 Service cost 159 48 45 26 19 4 9 10 Interest cost 328 79 100 47 53 18 26 14 Actuarial loss 455 68 158 57 99 35 26 38 Transfers — 27 (32 ) (2 ) (15 ) 12 — — Plan amendments (61 ) — — — — — (61 ) Benefits paid (537 ) (145 ) (146 ) (75 ) (69 ) (37 ) (50 ) (5 ) Benefits paid - settlements (27 ) — — — — — — (27 ) Obligation at measurement date $ 8,448 $ 2,029 $ 2,637 $ 1,211 $ 1,410 $ 479 $ 669 $ 313 Accumulated Benefit Obligation at measurement date $ 8,369 $ 2,029 $ 2,601 $ 1,211 $ 1,375 $ 468 $ 652 $ 313 Change in Fair Value of Plan Assets Plan assets at prior measurement date $ 8,531 $ 2,225 $ 2,675 $ 1,290 $ 1,352 $ 428 $ 657 $ 346 Employer contributions 19 — — — — 4 — 11 Actual return on plan assets 1,017 265 317 153 161 51 77 43 Benefits paid (537 ) (145 ) (146 ) (75 ) (69 ) (37 ) (50 ) (5 ) Benefits paid - settlements (27 ) — — — — — — (27 ) Transfers — 27 (32 ) (2 ) (15 ) 12 — — Plan assets at measurement date $ 9,003 $ 2,372 $ 2,814 $ 1,366 $ 1,429 $ 458 $ 684 $ 368 Funded status of plan $ 555 $ 343 $ 177 $ 155 $ 19 $ (21 ) $ 15 $ 55 Year Ended December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Change in Projected Benefit Obligation Obligation at prior measurement date $ 7,727 $ 1,995 $ 2,451 $ 1,143 $ 1,276 $ 453 $ 649 Obligation assumed from acquisition 352 — — — — — — Service cost 147 48 42 24 19 4 9 Interest cost 335 86 106 49 55 19 28 Actuarial loss 307 46 111 52 57 13 41 Transfers — 14 (3 ) (3 ) — (3 ) — Plan amendments (52 ) (3 ) — — — (3 ) (15 ) Benefits paid (679 ) (234 ) (195 ) (107 ) (84 ) (36 ) (54 ) Impact of settlements (6 ) — — — — — — Obligation at measurement date $ 8,131 $ 1,952 $ 2,512 $ 1,158 $ 1,323 $ 447 $ 658 Accumulated Benefit Obligation at measurement date $ 8,006 $ 1,952 $ 2,479 $ 1,158 $ 1,290 $ 436 $ 649 Change in Fair Value of Plan Assets Plan assets at prior measurement date $ 8,136 $ 2,243 $ 2,640 $ 1,284 $ 1,321 $ 433 $ 655 Assets received from acquisition 343 — — — — — — Employer contributions 155 43 43 24 20 5 9 Actual return on plan assets 582 159 190 92 95 29 47 Benefits paid (679 ) (234 ) (195 ) (107 ) (84 ) (36 ) (54 ) Impact of settlements (6 ) — — — — — — Transfers — 14 (3 ) (3 ) — (3 ) — Plan assets at measurement date $ 8,531 $ 2,225 $ 2,675 $ 1,290 $ 1,352 $ 428 $ 657 Funded status of plan $ 400 $ 273 $ 163 $ 132 $ 29 $ (19 ) $ (1 ) Piedmont Two Months Ended Years Ended (in millions) December 31, 2016 October 31, 2016 Change in Projected Benefit Obligation Obligation at prior measurement date $ 352 $ 312 Service cost 2 11 Interest cost 2 9 Actuarial gain (5 ) 34 Benefits paid (1 ) (14 ) Impact of settlements (6 ) — Obligation at measurement date $ 344 $ 352 Accumulated Benefit Obligation at measurement date $ 289 $ 296 Change in Fair Value of Plan Assets Plan assets at prior measurement date $ 343 $ 329 Employer contributions 10 10 Actual return on plan assets — 18 Benefits paid (1 ) (14 ) Impact of settlements (6 ) — Plan assets at measurement date $ 346 $ 343 Funded status of plan $ 2 $ (9 ) Amounts Recognized in the Consolidated Balance Sheets December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Prefunded pension (a) $ 680 $ 343 $ 245 $ 155 $ 87 $ 8 $ 16 $ 55 Noncurrent pension liability (b) $ 125 $ — $ 68 $ — $ 68 $ 29 $ 1 $ — Net asset (liability) recognized $ 555 $ 343 $ 177 $ 155 $ 19 $ (21 ) $ 15 $ 55 Regulatory assets $ 1,886 $ 406 $ 756 $ 341 $ 415 $ 90 $ 152 $ 73 Accumulated other comprehensive (income) loss Deferred income tax benefit $ (41 ) $ — $ (3 ) $ — $ — $ — $ — $ — Prior service credit (5 ) — — — — — — — Net actuarial loss 116 — 9 — — — — — Net amounts recognized in accumulated other comprehensive loss $ 70 $ — $ 6 $ — $ — $ — $ — $ — Amounts to be recognized in net periodic pension costs in the next year Unrecognized net actuarial loss $ 132 $ 29 $ 44 $ 21 $ 23 $ 5 $ 7 $ 11 Unrecognized prior service credit (32 ) (8 ) (3 ) (2 ) (1 ) — (2 ) (9 ) December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Prefunded pension (a) $ 518 $ 273 $ 225 $ 132 $ 91 $ 6 $ — 3 Noncurrent pension liability (b) $ 118 $ — $ 62 $ — $ 62 $ 25 $ 1 — Net asset recognized $ 400 $ 273 $ 163 $ 132 $ 29 $ (19 ) $ (1 ) $ 3 Regulatory assets $ 2,098 $ 476 $ 805 $ 378 $ 426 $ 81 $ 171 $ 137 Accumulated other comprehensive (income) loss Deferred income tax benefit $ (41 ) $ — $ (6 ) $ — $ — $ — $ — $ — Prior service credit (6 ) — — — — — — — Net actuarial loss 123 — 16 — — — — — Net amounts recognized in accumulated other comprehensive loss $ 76 $ — $ 10 $ — $ — $ — $ — $ — Amounts to be recognized in net periodic pension costs in the next year Unrecognized net actuarial loss $ 147 $ 31 $ 52 $ 23 $ 29 $ 5 $ 8 $ 13 Unrecognized prior service credit $ (24 ) $ (8 ) $ (3 ) $ (2 ) $ (1 ) $ — $ (2 ) $ (2 ) (a) Included in Other within Other Noncurrent Assets on the Consolidated Balance Sheets. (b) Included in Accrued pension and other post-retirement benefit costs on the Consolidated Balance Sheets. Information for Plans with Accumulated Benefit Obligation in Excess of Plan Assets December 31, 2017 Duke Duke Duke Progress Energy Energy (in millions) Energy Energy Florida Ohio Projected benefit obligation $ 1,386 $ 718 $ 718 $ 337 Accumulated benefit obligation 1,326 683 683 326 Fair value of plan assets 1,260 650 650 308 December 31, 2016 Duke Duke Duke Progress Energy Energy (in millions) Energy Energy Florida Ohio Projected benefit obligation $ 1,299 $ 665 $ 665 $ 311 Accumulated benefit obligation 1,239 633 633 299 Fair value of plan assets 1,182 604 604 286 Assumptions Used for Pension Benefits Accounting The discount rate used to determine the current year pension obligation and following year’s pension expense is based on a bond selection-settlement portfolio approach. This approach develops a discount rate by selecting a portfolio of high quality corporate bonds that generate sufficient cash flow to provide for projected benefit payments of the plan. The selected bond portfolio is derived from a universe of non-callable corporate bonds rated Aa quality or higher. After the bond portfolio is selected, a single interest rate is determined that equates the present value of the plan’s projected benefit payments discounted at this rate with the market value of the bonds selected. The average remaining service period of active covered employees is 13 years for Duke Energy and Duke Energy Progress, 12 years for Duke Energy Carolinas, Progress Energy, and Duke Energy Florida, 14 years for Duke Energy Ohio and Duke Energy Indiana, and nine years for Piedmont. The following tables present the assumptions or range of assumptions used for pension benefit accounting. December 31, 2017 2016 2015 Benefit Obligations Discount rate 3.60% 4.10% 4.40% Salary increase 3.50 % – 4.00% 4.00 % – 4.50% 4.00 % – 4.40% Net Periodic Benefit Cost Discount rate 4.10% 4.40% 4.10% Salary increase 4.00 % – 4.50% 4.00 % – 4.40% 4.00 % – 4.40% Expected long-term rate of return on plan assets 6.50 % – 6.75% 6.50 % – 6.75% 6.50% Piedmont Two Months Ended Years Ended October 31, December 31, 2016 2016 2015 Benefit Obligations Discount rate 4.10 % 3.80 % 4.34 % Salary increase 4.50 % 4.05 % 4.07 % Net Periodic Benefit Cost Discount rate 3.80 % 4.34 % 4.13 % Salary increase 4.05 % 4.07 % 3.68 % Expected long-term rate of return on plan assets 6.75 % 7.25 % 7.50 % Expected Benefit Payments Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Years ending December 31, 2018 $ 642 $ 185 $ 161 $ 85 $ 75 $ 36 $ 47 $ 29 2019 644 185 164 86 77 36 46 26 2020 661 195 172 90 80 36 44 24 2021 666 194 175 93 81 37 44 24 2022 672 197 176 92 83 36 44 23 2023-2027 3,099 865 888 449 435 166 210 103 NON-QUALIFIED PENSION PLANS Components of Net Periodic Pension Costs Year Ended December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Service cost $ 2 $ 1 $ — $ — $ — $ — $ — $ — Interest cost on projected benefit obligation 13 1 5 1 2 — — — Amortization of actuarial loss 8 — 2 1 1 — — — Amortization of prior service credit (2 ) — — — — — — — Net periodic pension costs $ 21 $ 2 $ 7 $ 2 $ 3 $ — $ — $ — Year Ended December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Service cost $ 2 $ — $ — $ — $ — $ — $ — Interest cost on projected benefit obligation 14 1 5 1 2 — — Amortization of actuarial loss 8 1 1 1 1 — — Amortization of prior service credit (1 ) — — — — — — Net periodic pension costs $ 23 $ 2 $ 6 $ 2 $ 3 $ — $ — Year Ended December 31, 2015 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Service cost $ 3 $ — $ 1 $ — $ — $ — $ — Interest cost on projected benefit obligation 13 1 4 1 2 — — Amortization of actuarial loss 6 — 2 1 2 — 1 Amortization of prior service credit (1 ) — (1 ) — — — — Net periodic pension costs $ 21 $ 1 $ 6 $ 2 $ 4 $ — $ 1 Piedmont Years Ended October 31, (in millions) 2016 2015 Amortization of prior service cost $ — $ 1 Settlement charge 1 — Net periodic pension costs $ 1 $ 1 Amounts Recognized in Accumulated Other Comprehensive Income and Regulatory Assets and Liabilities Year Ended December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Regulatory assets, net (decrease) increase $ 5 $ (1 ) $ 3 $ 1 $ 2 $ — $ — $ — Accumulated other comprehensive (income) loss Deferred income tax benefit $ (1 ) $ — $ — $ — $ — $ — $ — $ — Actuarial loss arising during the year 2 — — — — — — — Net amount recognized in accumulated other comprehensive loss (income) $ 1 $ — $ — $ — $ — $ — $ — $ — Year Ended December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Regulatory assets, net (decrease) increase $ (3 ) $ (2 ) $ 2 $ 1 $ 1 $ — $ (1 ) Accumulated other comprehensive (income) loss Prior service credit arising during the year $ (1 ) $ — $ — $ — $ — $ — $ — Actuarial gains arising during the year 1 — — — — — — Net amount recognized in accumulated other comprehensive loss (income) $ — $ — $ — $ — $ — $ — $ — Reconciliation of Funded Status to Net Amount Recognized Year Ended December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Change in Projected Benefit Obligation Obligation at prior measurement date $ 332 $ 14 $ 114 $ 33 $ 46 $ 4 $ 3 $ 4 Service cost 2 1 — — — — — — Interest cost 13 1 5 1 2 — — — Actuarial losses (gains) 15 — 5 4 2 — — — Benefits paid (31 ) (2 ) (8 ) (3 ) (3 ) — — — Obligation at measurement date $ 331 $ 14 $ 116 $ 35 $ 47 $ 4 $ 3 $ 4 Accumulated Benefit Obligation at measurement date $ 331 $ 14 $ 116 $ 35 $ 47 $ 4 $ 3 $ 4 Change in Fair Value of Plan Assets Benefits paid $ (31 ) $ (2 ) $ (8 ) $ (3 ) $ (3 ) $ — $ — $ — Employer contributions 31 2 8 3 3 — — — Plan assets at measurement date $ — $ — $ — $ — $ — $ — $ — $ — Year Ended December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Change in Projected Benefit Obligation Obligation at prior measurement date $ 341 $ 16 $ 112 $ 33 $ 46 $ 4 $ 5 Obligation assumed from acquisition 5 — — — — — — Service cost 2 — — — — — — Interest cost 14 1 5 1 2 — — Actuarial losses (gains) 4 (1 ) 5 2 1 — (2 ) Plan amendments (2 ) — — — — — Benefits paid (32 ) (2 ) (8 ) (3 ) (3 ) — — Obligation at measurement date $ 332 $ 14 $ 114 $ 33 $ 46 $ 4 $ 3 Accumulated Benefit Obligation at measurement date $ 332 $ 14 $ 114 $ 33 $ 46 $ 4 $ 3 Change in Fair Value of Plan Assets Benefits paid $ (32 ) $ (2 ) $ (8 ) $ (3 ) $ (3 ) — — Employer contributions 32 2 8 3 3 — — Plan assets at measurement date $ — $ — $ — $ — $ — $ — $ — Piedmont Two Months Ended Years Ended (in millions) December 31, 2016 October 31, 2016 Change in Projected Benefit Obligation Obligation at prior measurement date $ 5 $ 6 Actuarial gain (1 ) — Impact of settlements — (1 ) Obligation at measurement date $ 4 $ 5 Accumulated Benefit Obligation at measurement date $ — $ 5 Change in Fair Value of Plan Assets Plan assets at prior measurement date $ — $ 1 Impact of settlements — (1 ) Plan assets at measurement date $ — $ — Amounts Recognized in the Consolidated Balance Sheets December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Current pension liability (a) $ 23 $ 2 $ 8 $ 3 $ 3 $ — $ — $ — Noncurrent pension liability (b) 308 12 108 32 44 4 3 4 Total accrued pension liability $ 331 $ 14 $ 116 $ 35 $ 47 $ 4 $ 3 $ 4 Regulatory assets $ 78 $ 4 $ 21 $ 8 $ 13 $ 1 $ — $ 1 Accumulated other comprehensive (income) loss Deferred income tax benefit $ (4 ) $ — $ (3 ) $ — $ — $ — $ — $ — Prior service credit (1 ) — — — — — — — Net actuarial loss 12 — 9 — — — — — Net amounts recognized in accumulated other comprehensive loss $ 7 $ — $ 6 $ — $ — $ — $ — $ — Amounts to be recognized in net periodic pension expense in the next year Unrecognized net actuarial loss $ 8 $ — $ 2 $ 1 $ 1 $ — $ — $ — Unrecognized prior service credit (2 ) — — — — — — — December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Current pension liability (a) $ 28 $ 2 $ 8 $ 2 $ 3 $ — $ — $ — Noncurrent pension liability (b) 304 12 106 31 43 4 3 4 Total accrued pension liability $ 332 $ 14 $ 114 $ 33 $ 46 $ 4 $ 3 $ 4 Regulatory assets $ 73 $ 5 $ 18 $ 7 $ 11 $ 1 $ — $ 1 Accumulated other comprehensive (income) loss Deferred income tax benefit $ (3 ) $ — $ (3 ) $ — $ — $ — $ — $ — Prior service credit (1 ) — — — — — — — Net actuarial loss 10 — 9 — — — — — Net amounts recognized in accumulated other comprehensive loss $ 6 $ — $ 6 $ — $ — $ — $ — $ — Amounts to be recognized in net periodic pension expense in the next year Unrecognized net actuarial loss $ 7 $ — $ 2 $ 1 $ 1 $ — $ — $ — Unrecognized prior service credit $ (2 ) $ — $ — $ — $ — $ — $ — $ — (a) Included in Other within Current Liabilities on the Consolidated Balance Sheets. (b) Included in Accrued pension and other post-retirement benefit costs on the Consolidated Balance Sheets. Information for Plans with Accumulated Benefit Obligation in Excess of Plan Assets December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Projected benefit obligation $ 331 $ 14 $ 116 $ 35 $ 47 $ 4 $ 3 $ 4 Accumulated benefit obligation 331 14 116 35 47 4 3 4 December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Projected benefit obligation $ 332 $ 14 $ 114 $ 33 $ 46 $ 4 $ 3 $ 4 Accumulated benefit obligation 332 14 114 33 46 4 3 4 Assumptions Used for Pension Benefits Accounting The discount rate used to determine the current year pension obligation and following year’s pension expense is based on a bond selection-settlement portfolio approach. This approach develops a discount rate by selecting a portfolio of high quality corporate bonds that generate sufficient cash flow to provide for projected benefit payments of the plan. The selected bond portfolio is derived from a universe of non-callable corporate bonds rated Aa quality or higher. After the bond portfolio is selected, a single interest rate is determined that equates the present value of the plan’s projected benefit payments discounted at this rate with the market value of the bonds selected. The average remaining service period of active covered employees is 11 years for Duke Energy and Duke Energy Progress, 14 years for Progress Energy, 15 years for Duke Energy Florida, eight years for Duke Energy Carolinas, Duke Energy Ohio, and Duke Energy Indiana, and nine years for Piedmont. The following tables present the assumptions used for pension benefit accounting. December 31, 2017 2016 2015 Benefit Obligations Discount rate 3.60 % 4.10 % 4.40 % Salary increase 3.50 % – 4.00 % 4.40 % 4.40 % Net Periodic Benefit Cost Discount rate 4.10 % 4.40 % 4.10 % Salary increase 4.40 % 4.40 % 4.40 % Piedmont Two Months Ended Years Ended October 31, December 31, 2016 2016 2015 Benefit Obligations Discount rate 4.10 % 3.80 % 3.85 % Net Periodic Benefit Cost Discount rate 3.80 % 3.85 % 3.69 % Expected Benefit Payments Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Years ending December 31, 2018 $ 23 $ 2 $ 8 $ 3 $ 3 $ — $ — $ — 2019 21 1 8 2 3 — — — 2020 21 1 8 2 3 — — — 2021 22 1 8 2 3 — — — 2022 25 1 8 2 3 — — — 2023-2027 117 6 36 11 15 1 1 2 OTHER POST-RETIREMENT BENEFIT PLANS Duke Energy provides, and the Subsidiary Registrants participate in, some health care and life insurance benefits for retired employees on a contributory and non-contributory basis. Employees are eligible for these benefits if they have met age and service requirements at retirement, as defined in the plans. The health care benefits include medical, dental and prescription drug coverage and are subject to certain limitations, such as deductibles and copayments. Duke Energy did not make any pre-funding contributions to its other post-retirement benefit plans during the years ended December 31, 2017 , 2016 or 2015 . Components of Net Periodic Other Post-Retirement Benefit Costs Year Ended December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Service cost $ 4 $ 1 $ — $ — $ — $ — $ — $ 1 Interest cost on accumulated post-retirement benefit obligation 34 8 13 7 6 1 3 1 Expected return on plan assets (14 ) (8 ) — — — — (1 ) (2 ) Amortization of actuarial loss (gain) 10 (2 ) 21 12 9 (2 ) (1 ) 1 Amortization of prior service credit (115 ) (10 ) (84 ) (54 ) (30 ) — (1 ) — Curtailment credit (c) $ (30 ) $ (4 ) $ (16 ) $ — $ (16 ) $ (2 ) $ (2 ) $ — Net periodic post-retirement benefit costs (a)(b) $ (111 ) $ (15 ) $ (66 ) $ (35 ) $ (31 ) $ (3 ) $ (2 ) $ 1 Year Ended December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Service cost $ 3 $ 1 $ 1 $ — $ 1 $ — $ — Interest cost on accumulated post-retirement benefit obligation 35 8 15 8 7 1 4 Expected return on plan assets (12 ) (8 ) — — — — (1 ) Amortization of actuarial loss (gain) 6 (3 ) 22 13 9 (2 ) (1 ) Amortization of prior service credit (141 ) (14 ) (103 ) (68 ) (35 ) — (1 ) Net periodic post-retirement benefit costs (a)(b) $ (109 ) $ (16 ) $ (65 ) $ (47 ) $ (18 ) $ (1 ) $ 1 Year Ended December 31, 2015 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Service cost $ 6 $ 1 $ 1 $ 1 $ 1 $ — $ 1 Interest cost on accumulated post-retirement benefit obligation 36 9 15 8 7 2 4 Expected return on plan assets (13 ) (8 ) — — — (1 ) (1 ) Amortization of actuarial loss (gain) 16 (2 ) 28 18 10 (2 ) (2 ) Amortization of prior service credit (140 ) (14 ) (102 ) (68 ) (35 ) — — Net periodic post-retirement benefit costs (a)(b) $ (95 ) $ (14 ) $ (58 ) $ (41 ) $ (17 ) $ (1 ) $ 2 (a) Duke Energy amounts exclude $7 million , $8 million and $10 million for the years ended December 2017 , 2016 and 2015 , respectively, of regulatory asset amortization resulting from purchase accounting adjustments associated with Duke Energy's merger with Cinergy in April 2006. (b) Duke Energy Ohio amounts exclude $2 million , $2 million and $3 million for the years ended December 2017 , 2016 and 2015 , respectively, of regulatory asset amortization resulting from purchase accounting adjustments associated with Duke Energy's merger with Cinergy in April 2006. (c) Curtailment credit resulted from a reduction in average future service of plan participants due to a plan amendment. Piedmont Years Ended October 31, (in millions) 2016 2015 Service cost $ 1 $ 1 Interest cost on projected benefit obligation 1 2 Expected return on plan assets (2 ) (2 ) Amortization of actuarial loss 1 — Net periodic pension costs $ 1 $ 1 Amounts Recognized in Accumulated Other Comprehensive Income and Regulatory Assets and Liabilities Year Ended December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Regulatory assets, net increase (decrease) $ 71 $ — $ 81 $ 42 $ 39 $ — $ (5 ) $ (11 ) Regulatory liabilities, net increase (decrease) $ (27 ) $ (2 ) $ — $ — $ — $ (3 ) $ (7 ) $ — Accumulated other comprehensive (income) loss Deferred income tax benefit $ (1 ) $ — $ — $ — $ — $ — $ — $ — Amortization of prior year prior service credit 3 — — — — — — — Net amount recognized in accumulated other comprehensive income $ 2 $ — $ — $ — $ — $ — $ — $ — Year Ended December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Regulatory assets, net increase (decrease) $ 53 $ — $ 47 $ 38 $ 9 $ — $ (6 ) Regulatory liabilities, net increase (decrease) $ (114 ) $ (22 ) $ (51 ) $ (25 ) $ (26 ) $ (2 ) $ (12 ) Accumulated other comprehensive (income) loss Deferred income tax benefit $ (2 ) $ — $ — $ — $ — $ — $ — Actuarial losses arising during the year 3 — — — — — — Amortization of prior year prior service credit 1 — 1 — — — — Net amount recognized in accumulated other comprehensive income $ 2 $ — $ 1 $ — $ — $ — $ — Piedmont's regulatory assets net decreased $1 million for the two months ended December 31, 2016, and increased $2 million and $1 million for the years ended October 31, 2016, and 2015, respectively. Reconciliation of Funded Status to Accrued Other Post-Retirement Benefit Costs Year Ended December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Change in Projected Benefit Obligation Accumulated post-retirement benefit obligation at prior measurement date $ 868 $ 201 $ 357 $ 191 $ 164 $ 32 $ 83 $ 39 Service cost 4 1 — — — — — 1 Interest cost 34 8 13 7 6 1 3 1 Plan participants' contributions 17 3 6 3 3 1 2 — Actuarial (gains) losses 4 (3 ) 4 1 3 — 3 1 Transfers — 2 (1 ) — (1 ) 1 — — Plan amendments (28 ) (5 ) (3 ) (1 ) (2 ) (2 ) (2 ) (9 ) Benefits paid (86 ) (18 ) (34 ) (17 ) (17 ) (3 ) (11 ) (1 ) Accumulated post-retirement benefit obligation at measurement date $ 813 $ 189 $ 342 $ 184 $ 156 $ 30 $ 78 $ 32 Change in Fair Value of Plan Assets Plan assets at prior measurement date $ 244 $ 137 $ 1 $ — $ — $ 7 $ 22 $ 29 Actual return on plan assets 25 15 1 — — 2 1 3 Benefits paid (86 ) (18 ) (34 ) (17 ) (17 ) (3 ) (11 ) (1 ) Employer contributions (reimbursements) 25 (4 ) 26 14 14 — (3 ) — Plan participants' contributions 17 3 6 3 3 1 2 — Plan assets at measurement date $ 225 $ 133 $ — $ — $ — $ 7 $ 11 $ 31 Year Ende

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	INCOME TAXES Tax Act On December 22, 2017, President Trump signed the Tax Act into law. Among other provisions, the Tax Act lowers the corporate federal income tax rate from 35 percent to 21 percent and eliminates bonus depreciation for regulated utilities, effective January 1, 2018. The Tax Act also could be amended or subject to technical correction, which could change the financial impacts that were recorded at December 31, 2017, or are expected to be recorded in future periods. The FERC and state utility commissions will determine the regulatory treatment of the impacts of the Tax Act for the Subsidiary Registrants. The Duke Energy Registrants’ future results of operations, financial condition and cash flows could be adversely impacted by the Tax Act, subsequent amendments or corrections or the actions of the FERC, state utility commissions or credit rating agencies related to the Tax Act. Duke Energy is reviewing orders to address the rate treatment of the Tax Act by each state utility commission in which the Subsidiary Registrants operate. See Note 4 for additional information. Beginning in January 2018, the Subsidiary Registrants will defer the estimated ongoing impacts of the Tax Act that are expected to be returned to customers. As a result of the Tax Act, Duke Energy revalued its existing deferred tax assets and deferred tax liabilities as of December 31, 2017, to account for the estimated future impact of lower corporate tax rates on these deferred tax amounts. For Duke Energy's regulated operations, where the reduction in the net accumulated deferred income tax (ADIT) liability is expected to be returned to customers in future rates, the net remeasurement has been deferred as a regulatory liability. The regulatory liability for income taxes includes the effect of the reduction of the net deferred tax liability including the tax gross-up of the excess accumulated deferred tax liabilities and the effect of the new tax rate on the previous regulatory asset for income taxes. Excess accumulated deferred income taxes are generally classified as either “protected” or “unprotected” under IRS rules. Protected excess ADIT, resulting from accumulated tax depreciation of public utility property, are required to utilize the average rate assumption method under the IRS normalization rules for determining the timing of the return to customers. The majority of the excess ADIT is related to protected amounts associated with public utility property. See Note 4 for additional information on the Tax Act's impact to the regulatory asset and liability accounts. On December 22, 2017, the SEC staff issued Staff Accounting Bulletin No. 118, Income Tax Accounting Implications of the Tax Cuts and Jobs Act (SAB 118), which provides guidance on accounting for the Tax Act’s impact. SAB 118 provides a measurement period, which in no case should extend beyond one year from the Tax Act enactment date, during which a company acting in good faith may complete the accounting for the impacts of the Tax Act under ASC Topic 740. In accordance with SAB 118, a company must reflect the income tax effects of the Tax Act in the reporting period in which the accounting under ASC Topic 740 is complete. To the extent that a company’s accounting for certain income tax effects of the Tax Act is incomplete, a company can determine a reasonable estimate for those effects and record a provisional estimate in the financial statements in the first reporting period in which a reasonable estimate can be determined. Duke Energy recorded a provisional net tax benefit of $112 million related to the Tax Act in the period ending December 31, 2017. This net benefit primarily consists of a net benefit of $534 million due to the remeasurement of deferred tax accounts to reflect the corporate rate reduction impact to net deferred tax balances, a net expense for the establishment of a valuation allowance related to foreign tax credits of $406 million and a transition tax on previously untaxed earnings and profits on foreign subsidiaries of $10 million . The majority of Duke Energy’s operations are regulated and it is expected that the Subsidiary Registrants will ultimately pass on the savings associated with the amount representing the remeasurement of deferred tax balances related to regulated operations to customers. Duke Energy recorded a regulatory liability of $8,313 million , representing the revaluation of those deferred tax balances. The Subsidiary Registrants continue to respond to requests from regulators in various jurisdictions to determine the timing and magnitude of savings they will pass on to customers. The net provisional charge from deferred tax remeasurement and assessment of valuation allowance is based on currently available information and interpretations which are continuing to evolve. Duke Energy continues to analyze additional information and guidance related to certain aspects of the Tax Act, such as limitations on the deductibility of interest and executive compensation, conformity or decoupling by state legislatures in response to the Tax Act, and the final determination of the net deferred tax liabilities subject to the remeasurement. The prospects of supplemental legislation or regulatory processes to address questions that arise because of the Tax Act, or evolving technical interpretations of the tax law, may also cause the final impact from the Tax Act to differ from the estimated amounts. Duke Energy continues to appropriately refine such amounts within the measurement period allowed by SAB 118, which will be completed no later than the fourth quarter of 2018. Income Tax Expense Components of Income Tax Expense Year Ended December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Current income taxes Federal $ (247 ) $ 221 $ (436 ) $ (95 ) $ (188 ) $ (37 ) $ 128 $ (90 ) State 4 20 (5 ) 2 (11 ) 2 21 (3 ) Foreign 3 — — — — — — — Total current income taxes (240 ) 241 (441 ) (93 ) (199 ) (35 ) 149 (93 ) Deferred income taxes Federal 1,344 381 664 378 194 99 138 147 State 102 35 44 10 51 (4 ) 14 8 Total deferred income taxes (a) (b) 1,446 416 708 388 245 95 152 155 Investment tax credit amortization (10 ) (5 ) (3 ) (3 ) — (1 ) — — Income tax expense from continuing operations 1,196 652 264 292 46 59 301 62 Tax benefit from discontinued operations (6 ) — — — — — — — Total income tax expense included in Consolidated Statements of Operations $ 1,190 $ 652 $ 264 $ 292 $ 46 $ 59 $ 301 $ 62 (a) Includes utilization of NOL (Net operating loss) carryforwards and tax credit carryforwards of $428 million at Duke Energy, $74 million at Progress Energy, $36 million at Duke Energy Florida, $17 million at Duke Energy Ohio, $42 million at Duke Energy Indiana and $79 million at Piedmont. In addition the total deferred income taxes Includes benefits of NOL carryforwards and tax credit carryforwards of $10 million at Duke Energy Carolinas and $1 million at Duke Energy Progress. (b) As a result of the Tax Act, Duke Energy's deferred tax assets and liabilities were revalued as of December 31, 2017. See the Statutory Rate Reconciliation section below for additional information on the Tax Act's impact on income tax expense. Year Ended December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Current income taxes Federal $ — $ 139 $ 15 $ (59 ) $ 76 $ (7 ) $ 7 State (15 ) 25 (19 ) (25 ) 22 (13 ) 6 Foreign 2 — — — — — — Total current income taxes (13 ) 164 (4 ) (84 ) 98 (20 ) 13 Deferred income taxes Federal 1,064 430 486 350 199 88 202 State 117 45 50 40 25 11 11 Total deferred income taxes (a) 1,181 475 536 390 224 99 213 Investment tax credit amortization (12 ) (5 ) (5 ) (5 ) — (1 ) (1 ) Income tax expense from continuing operations 1,156 634 527 301 322 78 225 Tax (benefit) expense from discontinued operations (30 ) — 1 — — (36 ) — Total income tax expense included in Consolidated Statements of Operations $ 1,126 $ 634 $ 528 $ 301 $ 322 $ 42 $ 225 (a) Includes benefits of NOL carryforwards and utilization of NOL and tax credit carryforwards of $648 million at Duke Energy, $4 million at Duke Energy Carolinas, $190 million at Progress Energy, $60 million at Duke Energy Progress, $49 million at Duke Energy Florida, $26 million at Duke Energy Ohio and $58 million at Duke Energy Indiana. Year Ended December 31, 2015 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Current income taxes Federal $ — $ 216 $ (193 ) $ (56 ) $ 1 $ (18 ) $ (86 ) State (12 ) 14 1 (4 ) (7 ) (1 ) (12 ) Foreign 4 — — — — — — Total current income taxes (8 ) 230 (192 ) (60 ) (6 ) (19 ) (98 ) Deferred income taxes Federal 1,097 345 694 334 290 96 245 State 181 57 27 27 58 5 17 Total deferred income taxes (a) 1,278 402 721 361 348 101 262 Investment tax credit amortization (14 ) (5 ) (7 ) (7 ) — (1 ) (1 ) Income tax expense from continuing operations 1,256 627 522 294 342 81 163 Tax expense (benefit) from discontinued operations 89 — (1 ) — — 22 — Total income tax expense included in Consolidated Statements of Operations $ 1,345 $ 627 $ 521 $ 294 $ 342 $ 103 $ 163 (a) Includes utilization of NOL carryforwards and tax credit carryforwards of $264 million at Duke Energy, $15 million at Duke Energy Carolinas, $119 million at Progress Energy, $21 million at Duke Energy Progress, $84 million at Duke Energy Florida, $3 million at Duke Energy Ohio and $45 million at Duke Energy Indiana. Piedmont Two Months Ended Years Ended October 31, (in millions) December 31, 2016 2016 2015 Current income taxes Federal $ 4 $ 27 $ (1 ) State (2 ) 12 1 Total current income taxes 2 39 — Deferred income taxes Federal 24 79 78 State 6 6 12 Total deferred income taxes (a)(b) 30 85 90 Total income tax expense from continuing operations included in Consolidated Statements of Operations $ 32 $ 124 $ 90 (a) Includes benefits of NOL and tax carryforwards of $17 million and $91 million for the two months ended December 31, 2016, and the year ended October 31, 2016, respectively. (b) Includes benefits and utilization of NOL carryforwards of $46 million for the year ended October 31, 2015. Duke Energy Income from Continuing Operations before Income Taxes Years Ended December 31, (in millions) 2017 2016 2015 Domestic (a) $ 4,207 $ 3,689 $ 3,831 Foreign 59 45 79 Income from continuing operations before income taxes $ 4,266 $ 3,734 $ 3,910 (a) Includes a $16 million expense in 2017 related to the Tax Act impact on equity earnings included within Equity in earnings (losses) of unconsolidated affiliates on the Consolidated Statement of Operations. Taxes on Foreign Earnings In February 2016, Duke Energy announced it had initiated a process to divest the International Disposal Group and, accordingly, no longer intended to indefinitely reinvest post-2014 undistributed foreign earnings. This change in the company's intent, combined with the extension of bonus depreciation by Congress in late 2015, allowed Duke Energy to more efficiently utilize foreign tax credits and reduce U.S. deferred tax liabilities associated with the historical unremitted foreign earnings by approximately $95 million during the year ended December 31, 2016. Due to the classification of the International Disposal Group as discontinued operations beginning in the fourth quarter of 2016, income tax amounts related to the International Disposal Group's foreign earnings are presented within (Loss) Income From Discontinued Operations, net of tax on the Consolidated Statements of Operations. In December 2016, Duke Energy closed on the sale of the International Disposal Group in two separate transactions to execute the divestiture. See Note 2 for additional information on the sale. Statutory Rate Reconciliation The following tables present a reconciliation of income tax expense at the U.S. federal statutory tax rate to the actual tax expense from continuing operations. Year Ended December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Income tax expense, computed at the statutory rate of 35 percent $ 1,493 $ 653 $ 536 $ 353 $ 265 $ 88 $ 229 $ 70 State income tax, net of federal income tax effect 69 36 25 8 26 (1 ) 23 3 AFUDC equity income (81 ) (37 ) (32 ) (17 ) (16 ) (4 ) (8 ) — Renewable energy production tax credits (132 ) — — — — — — — Tax Act (a) (112 ) 15 (246 ) (40 ) (226 ) (23 ) 55 (12 ) Tax true-up (52 ) (24 ) (19 ) (13 ) (7 ) (5 ) (6 ) — Other items, net 11 9 — 1 4 4 8 1 Income tax expense from continuing operations $ 1,196 $ 652 $ 264 $ 292 $ 46 $ 59 $ 301 $ 62 Effective tax rate 28.0 % 34.9 % 17.2 % 29.0 % 6.1 % 23.4 % 46.0 % 30.8 % (a) Amounts primarily include but are not limited to items that are excluded for ratemaking purposes related to abandoned or impaired assets, certain wholesale fixed rate contracts, remeasurement of nonregulated net deferred tax liabilities, Federal net operating losses, and valuation allowance on foreign tax credits. Year Ended December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Income tax expense, computed at the statutory rate of 35 percent $ 1,307 $ 630 $ 548 $ 315 $ 306 $ 95 $ 212 State income tax, net of federal income tax effect 64 46 20 10 30 (2 ) 11 AFUDC equity income (70 ) (36 ) (26 ) (17 ) (9 ) (2 ) (6 ) Renewable energy production tax credits (97 ) — — — — — — Audit adjustment 5 3 — — — — — Tax true-up (14 ) (14 ) (11 ) (3 ) (9 ) (16 ) 2 Other items, net (39 ) 5 (4 ) (4 ) 4 3 6 Income tax expense from continuing operations $ 1,156 $ 634 $ 527 $ 301 $ 322 $ 78 $ 225 Effective tax rate 31.0 % 35.2 % 33.7 % 33.4 % 36.9 % 28.9 % 37.1 % Year Ended December 31, 2015 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Income tax expense, computed at the statutory rate of 35 percent $ 1,369 $ 598 $ 555 $ 302 $ 330 $ 81 $ 168 State income tax, net of federal income tax effect 109 46 18 15 33 2 2 AFUDC equity income (58 ) (34 ) (19 ) (17 ) (3 ) (1 ) (4 ) Renewable energy production tax credits (72 ) — (1 ) — — — — Audit adjustment (22 ) — (23 ) 1 (24 ) — — Tax true-up 2 2 (3 ) (4 ) 2 (5 ) (9 ) Other items, net (72 ) 15 (5 ) (3 ) 4 4 6 Income tax expense from continuing operations $ 1,256 $ 627 $ 522 $ 294 $ 342 $ 81 $ 163 Effective tax rate 32.1 % 36.7 % 32.9 % 34.2 % 36.3 % 35.2 % 34.0 % Piedmont Two Months Ended Years Ended October 31, (in millions) December 31, 2016 2016 2015 Income tax expense, computed at the statutory rate of 35 percent $ 30 $ 111 $ 79 State income tax, net of federal income tax effect 1 11 9 Other items, net 1 2 2 Income tax expense from continuing operations $ 32 $ 124 $ 90 Effective tax rate 37.2 % 39.1 % 39.7 % Valuation allowances have been established for certain state NOL carryforwards and state income tax credits that reduce deferred tax assets to an amount that will be realized on a more-likely-than-not basis. The net change in the total valuation allowance is included in the State income tax, net of federal income tax effect in the above tables. DEFERRED TAXES Net Deferred Income Tax Liability Components December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Deferred credits and other liabilities $ 143 $ 33 $ 78 $ 23 $ 49 $ 11 $ 6 $ (5 ) Capital lease obligations 49 14 — — — — 2 — Pension, post-retirement and other employee benefits 295 (17 ) 111 44 60 14 18 (4 ) Progress Energy merger purchase accounting adjustments (a) 536 — — — — — — — Tax credits and NOL carryforwards 4,527 234 402 156 143 25 216 70 Regulatory liabilities and deferred credits — 222 — — — 65 — 61 Investments and other assets — — — — — — 1 18 Other 73 10 1 4 — — — — Valuation allowance (519 ) — (14 ) — — — — — Total deferred income tax assets 5,104 496 578 227 252 115 243 140 Investments and other assets (1,419 ) (849 ) (470 ) (289 ) (187 ) — (14 ) — Accelerated depreciation rates (9,216 ) (3,060 ) (2,803 ) (1,583 ) (1,257 ) (896 ) (966 ) (697 ) Regulatory assets and deferred debits, net (1,090 ) — (807 ) (238 ) (569 ) — (188 ) — Other — — — — — — — (7 ) Total deferred income tax liabilities (11,725 ) (3,909 ) (4,080 ) (2,110 ) (2,013 ) (896 ) (1,168 ) (704 ) Net deferred income tax liabilities $ (6,621 ) $ (3,413 ) $ (3,502 ) $ (1,883 ) $ (1,761 ) $ (781 ) $ (925 ) $ (564 ) (a) Primarily related to capital lease obligations and debt fair value adjustments. As noted above, as a result of the Tax Act, Duke Energy revalued its existing deferred tax assets and liabilities as of December 31, 2017, to account for the estimated future impact of lower corporate tax rates on these deferred amounts. The following table shows the decrease reflected in the net deferred income tax liabilities balance above: (in millions) December 31, 2017 Duke Energy $ 8,982 Duke Energy Carolinas 3,454 Progress Energy 3,282 Duke Energy Progress 1,882 Duke Energy Florida 1,420 Duke Energy Ohio 771 Duke Energy Indiana 1,053 Piedmont 521 The following table presents the expiration of tax credits and NOL carryforwards. December 31, 2017 (in millions) Amount Expiration Year Investment tax credits $ 1,406 2024 — 2037 Alternative minimum tax credits 1,147 Refundable by 2021 Federal NOL carryforwards 393 2022 — 2036 State NOL carryforwards and credits (a) 296 2018 — 2037 Foreign NOL carryforwards (b) 13 2027 — 2036 Foreign Tax Credits (c) 1,272 2024 — 2027 Total tax credits and NOL carryforwards 4,527 (a) A valuation allowance of $90 million has been recorded on the state NOL carryforwards, as presented in the Net Deferred Income Tax Liability Components table. (b) A valuation allowance of $13 million has been recorded on the foreign NOL carryforwards, as presented in the Net Deferred Income Tax Liability Components table. (c) A valuation allowance of $416 million has been recorded on the foreign tax credits, as presented in the Net Deferred Income Tax Liability Components table. December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Deferred credits and other liabilities $ 382 $ 66 $ 126 $ 40 $ 93 $ 21 $ 4 $ 71 Capital lease obligations 60 8 — — — — 1 — Pension, post-retirement and other employee benefits 561 16 199 91 96 22 37 10 Progress Energy merger purchase accounting adjustments (a) 918 — — — — — — — Tax credits and NOL carryforwards 4,682 192 1,165 222 232 49 278 192 Investments and other assets — — — — — 3 — — Other 205 16 35 8 — 5 9 45 Valuation allowance (96 ) — (12 ) — — — — (1 ) Total deferred income tax assets 6,712 298 1,513 361 421 100 329 317 Investments and other assets (1,892 ) (1,149 ) (597 ) (313 ) (297 ) — (21 ) (21 ) Accelerated depreciation rates (14,872 ) (4,664 ) (4,490 ) (2,479 ) (2,038 ) (1,404 ) (1,938 ) (1,080 ) Regulatory assets and deferred debits, net (4,103 ) (1,029 ) (1,672 ) (892 ) (780 ) (139 ) (270 ) (147 ) Total deferred income tax liabilities (20,867 ) (6,842 ) (6,759 ) (3,684 ) (3,115 ) (1,543 ) (2,229 ) (1,248 ) Net deferred income tax liabilities $ (14,155 ) $ (6,544 ) $ (5,246 ) $ (3,323 ) $ (2,694 ) $ (1,443 ) $ (1,900 ) $ (931 ) (a) Primarily related to capital lease obligations and debt fair value adjustments. On August 6, 2015, pursuant to N.C. Gen. Stat. 105-130.3C, the North Carolina Department of Revenue announced the North Carolina corporate income tax rate would be reduced from a statutory rate of 5.0 percent to 4.0 percent beginning January 1, 2016. Duke Energy and Piedmont recorded net reductions of approximately $95 million and $18 million to their North Carolina deferred tax liabilities in the third quarter of 2015. The significant majority of these deferred tax liability reductions were offset by recording a regulatory liability pending NCUC determination of the disposition of amounts related to Duke Energy Carolinas, Duke Energy Progress and Piedmont. The impact did not have a significant impact on the financial position, results of operation, or cash flows of Duke Energy, Duke Energy Carolinas, Progress Energy or Duke Energy Progress. On August 4, 2016, pursuant to N.C. Gen. Stat. 105-130.3C, the North Carolina Department of Revenue announced the North Carolina corporate income tax rate would be reduced from a statutory rate of 4.0 percent to 3.0 percent beginning January 1, 2017. Duke Energy and Piedmont recorded net reductions of approximately $80 million and $16 million to their North Carolina deferred tax liabilities in the third quarter of 2016. The significant majority of this deferred tax liability reduction was offset by recording a regulatory liability pending NCUC determination of the disposition of amounts related to Duke Energy Carolinas, Duke Energy Progress and Piedmont. The impact did not have a significant impact on the financial position, results of operation, or cash flows of Duke Energy, Duke Energy Carolinas, Progress Energy or Duke Energy Progress. On June 28, 2017, the North Carolina General Assembly amended N.C. Gen. Stat. 105-130.3, reducing the North Carolina corporate income tax rate from a statutory rate of 3.0 percent to 2.5 percent beginning January 1, 2019. Duke Energy recorded a net reduction of approximately $55 million to their North Carolina deferred tax liabilities in the second quarter of 2017. The significant majority of this deferred tax liability reduction was offset by recording a regulatory liability pending NCUC determination of the disposition of amounts related to Duke Energy Carolinas, Duke Energy Progress and Piedmont. The impact did not have a significant impact on the financial position, results of operation or cash flows of Duke Energy, Duke Energy Carolinas, Progress Energy or Duke Energy Progress. UNRECOGNIZED TAX BENEFITS The following tables present changes to unrecognized tax benefits. Year Ended December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Unrecognized tax benefits – January 1 $ 17 $ 1 $ 2 $ 2 $ 4 $ 4 $ — $ — Unrecognized tax benefits increases (decreases) Gross increases – tax positions in prior periods 12 4 3 3 1 1 1 3 Gross decreases – tax positions in prior periods (4 ) — — — — (4 ) — — Total changes 8 4 3 3 1 (3 ) 1 3 Unrecognized tax benefits – December 31 $ 25 $ 5 $ 5 $ 5 $ 5 $ 1 $ 1 $ 3 Year Ended December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Unrecognized tax benefits – January 1 $ 88 $ 72 $ 1 $ 3 $ — $ — $ 1 Unrecognized tax benefits increases (decreases) Gross increases – tax positions in prior periods — — — — 4 4 — Gross decreases – tax positions in prior periods (4 ) (4 ) (1 ) (1 ) — — — Decreases due to settlements (68 ) (67 ) — — — — (1 ) Reduction due to lapse of statute of limitations 1 — 2 — — — — Total changes (71 ) (71 ) 1 (1 ) 4 4 (1 ) Unrecognized tax benefits – December 31 $ 17 $ 1 $ 2 $ 2 $ 4 $ 4 $ — Year Ended December 31, 2015 Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Indiana Unrecognized tax benefits – January 1 $ 213 $ 160 $ 32 $ 23 $ 8 $ 1 Unrecognized tax benefits increases (decreases) Gross increases – tax positions in prior periods — — 1 1 — — Gross decreases – tax positions in prior periods (48 ) (45 ) — — — — Decreases due to settlements (45 ) (43 ) — — — — Reduction due to lapse of statute of limitations (32 ) — (32 ) (21 ) (8 ) — Total changes (125 ) (88 ) (31 ) (20 ) (8 ) — Unrecognized tax benefits – December 31 $ 88 $ 72 $ 1 $ 3 $ — $ 1 The following table includes additional information regarding the Duke Energy Registrants' unrecognized tax benefits at December 31, 2017. During the first quarter of 2018, Duke Energy recognized an approximate $8 million reduction and Duke Energy Carolinas recognized an approximate $1 million reduction in unrecognized tax benefits. No additional material reductions are expected in the next 12 months. December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Amount that if recognized, would affect the effective tax rate or regulatory liability (a) $ 15 $ 4 $ 7 $ 5 $ 1 $ 1 $ 1 $ 3 Amount that if recognized, would be recorded as a component of discontinued operations 7 — — — — 2 — — (a) Duke Energy, Duke Energy Carolinas, Progress Energy, Duke Energy Progress, Duke Energy Florida, Duke Energy Indiana and Piedmont are unable to estimate the specific amounts that would affect the effective tax rate versus the regulatory liability. OTHER TAX MATTERS The following tables include interest recognized in the Consolidated Statements of Operations and the Consolidated Balance Sheets. Year Ended December 31, 2017 Duke Duke Duke Duke Energy Progress Energy Energy (in millions) Energy Carolinas Energy Progress Florida Net interest income recognized related to income taxes $ — $ — $ 1 $ — $ 1 Net interest expense recognized related to income taxes — 2 — — — Interest payable related to income taxes 5 25 1 1 — Year Ended December 31, 2016 Duke Duke Duke Duke Energy Progress Energy Energy (in millions) Energy Carolinas Energy Progress Florida Net interest income recognized related to income taxes $ — $ — $ 1 $ — $ 2 Net interest expense recognized related to income taxes — 7 — — — Interest payable related to income taxes 4 23 1 1 — Year Ended December 31, 2015 Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Indiana Net interest income recognized related to income taxes $ 12 $ — $ 2 $ 2 $ 1 $ 1 Net interest expense recognized related to income taxes — 1 — — — — Interest receivable related to income taxes 3 — — — — 3 Interest payable related to income taxes — 14 — 1 — — Piedmont recognized $1 million in net interest income recognized related to income taxes in the Consolidated Statements of Operations for the year ended October 31, 2016. Duke Energy and its subsidiaries are no longer subject to U.S. federal examination for years before 2015. With few exceptions, Duke Energy and its subsidiaries are no longer subject to state, local or non-U.S. income tax examinations by tax authorities for years before 2015.

Other Income and Expenses, Net

Other Income and Expenses, Net	12 Months Ended
	Dec. 31, 2017
Other Income and Expenses [Abstract]
Other Income and Expenses, Net	OTHER INCOME AND EXPENSES, NET The components of Other income and expenses, net on the Consolidated Statements of Operations are as follows. Amounts for Piedmont were not material. Year Ended December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Interest income $ 13 $ 2 $ 6 $ 2 $ 5 $ 6 $ 8 AFUDC equity 237 106 92 47 45 11 28 Post in-service equity returns 40 28 12 12 — — — Nonoperating income, other 62 3 18 4 11 — 1 Other income and expense, net $ 352 $ 139 $ 128 $ 65 $ 61 $ 17 $ 37 Year Ended December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Interest income $ 21 $ 4 $ 4 $ 3 $ 2 $ 5 $ 6 AFUDC equity 200 102 76 50 26 6 16 Post in-service equity returns 67 55 12 12 — — — Nonoperating income (expense), other 36 1 22 6 16 (2 ) — Other income and expense, net $ 324 $ 162 $ 114 $ 71 $ 44 $ 9 $ 22 Year Ended December 31, 2015 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Interest income $ 20 $ 2 $ 4 $ 2 $ 2 $ 4 $ 6 AFUDC equity 164 96 54 47 7 3 11 Post in-service equity returns 73 60 13 13 — — — Nonoperating income (expense), other 33 2 26 9 15 (1 ) (6 ) Other income and expense, net $ 290 $ 160 $ 97 $ 71 $ 24 $ 6 $ 11

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	SUBSEQUENT EVENTS For information on subsequent events related to regulatory matters, commitments and contingencies, debt and credit facilities, investments in unconsolidated affiliates, variable interest entities and common stock see Notes 4, 5, 6, 12, 17 and 18, respectively.

Quarterly Financial Data (Unaud

Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Data (Unaudited)	QUARTERLY FINANCIAL DATA (UNAUDITED) DUKE ENERGY Quarterly EPS amounts may not sum to the full-year total due to changes in the weighted average number of common shares outstanding and rounding. First Second Third Fourth (in millions, except per share data) Quarter Quarter Quarter Quarter Total 2017 Operating revenues $ 5,729 $ 5,555 $ 6,482 $ 5,799 $ 23,565 Operating income 1,437 1,387 1,695 1,262 5,781 Income from continuing operations 717 691 957 705 3,070 Loss from discontinued operations, net of tax — (2 ) (2 ) (2 ) (6 ) Net income 717 689 955 703 3,064 Net income attributable to Duke Energy Corporation 716 686 954 703 3,059 Earnings per share: Income from continuing operations attributable to Duke Energy Corporation common stockholders Basic $ 1.02 $ 0.98 $ 1.36 $ 1.00 $ 4.37 Diluted $ 1.02 $ 0.98 $ 1.36 $ 1.00 $ 4.37 Loss from discontinued operations attributable to Duke Energy Corporation common stockholders Basic $ — $ — $ — $ — $ (0.01 ) Diluted $ — $ — $ — $ — $ (0.01 ) Net income attributable to Duke Energy Corporation common stockholders Basic $ 1.02 $ 0.98 $ 1.36 $ 1.00 $ 4.36 Diluted $ 1.02 $ 0.98 $ 1.36 $ 1.00 $ 4.36 2016 Operating revenues $ 5,377 $ 5,213 $ 6,576 $ 5,577 $ 22,743 Operating income 1,240 1,259 1,954 888 5,341 Income from continuing operations 577 624 1,001 376 2,578 Income (Loss) from discontinued operations, net of tax 122 (112 ) 180 (598 ) (408 ) Net income (loss) 699 512 1,181 (222 ) 2,170 Net income (loss) attributable to Duke Energy Corporation 694 509 1,176 (227 ) 2,152 Earnings per share: Income from continuing operations attributable to Duke Energy Corporation common stockholders Basic $ 0.83 $ 0.90 $ 1.44 $ 0.53 $ 3.71 Diluted $ 0.83 $ 0.90 $ 1.44 $ 0.53 $ 3.71 Income (Loss) from discontinued operations attributable to Duke Energy Corporation common stockholders Basic $ 0.18 $ (0.16 ) $ 0.26 $ (0.86 ) $ (0.60 ) Diluted $ 0.18 $ (0.16 ) $ 0.26 $ (0.86 ) $ (0.60 ) Net income (loss) attributable to Duke Energy Corporation common stockholders Basic $ 1.01 $ 0.74 $ 1.70 $ (0.33 ) $ 3.11 Diluted $ 1.01 $ 0.74 $ 1.70 $ (0.33 ) $ 3.11 The following table includes unusual or infrequently occurring items in each quarter during the two most recently completed fiscal years. All amounts discussed below are pretax. First Second Third Fourth (in millions) Quarter Quarter Quarter Quarter Total 2017 Costs to Achieve Piedmont Merger (see Note 2) $ (16 ) $ (30 ) $ (23 ) $ (34 ) $ (103 ) Regulatory Settlements (see Note 4) — — (135 ) (23 ) (158 ) Commercial Renewables Impairments (see Notes 10 and 11) — — (84 ) (18 ) (102 ) Impacts of the Tax Act (see Note 22) — — — 102 102 Total $ (16 ) $ (30 ) $ (242 ) $ 27 $ (261 ) 2016 Costs to Achieve Mergers (see Note 2) $ (120 ) $ (111 ) $ (84 ) $ (208 ) $ (523 ) Commercial Renewables Impairment (see Note 12) — — (71 ) — (71 ) Loss on Sale of International Disposal Group (see Note 2) — — — (514 ) (514 ) Impairment of Assets in Central America (see Note 2) — (194 ) — — (194 ) Cost Savings Initiatives (see Note 19) (20 ) (24 ) (19 ) (29 ) (92 ) Total $ (140 ) $ (329 ) $ (174 ) $ (751 ) $ (1,394 ) DUKE ENERGY CAROLINAS First Second Third Fourth (in millions) Quarter Quarter Quarter Quarter Total 2017 Operating revenues $ 1,716 $ 1,729 $ 2,136 $ 1,721 $ 7,302 Operating income 484 485 777 403 2,149 Net income 270 273 466 205 1,214 2016 Operating revenues $ 1,740 $ 1,675 $ 2,226 $ 1,681 $ 7,322 Operating income 481 464 815 302 2,062 Net income 271 261 494 140 1,166 The following table includes unusual or infrequently occurring items in each quarter during the two most recently completed fiscal years. All amounts discussed below are pretax. First Second Third Fourth (in millions) Quarter Quarter Quarter Quarter Total 2017 Costs to Achieve Piedmont Merger (see Note 2) $ (4 ) $ (6 ) $ (5 ) $ (5 ) $ (20 ) Impacts of the Tax Act (see Note 22) — — — (15 ) (15 ) Total $ (4 ) $ (6 ) $ (5 ) $ (20 ) $ (35 ) 2016 Costs to Achieve Mergers $ (11 ) $ (12 ) $ (13 ) $ (68 ) $ (104 ) Cost Savings Initiatives (see Note 19) (10 ) (10 ) (8 ) (11 ) (39 ) Total $ (21 ) $ (22 ) $ (21 ) $ (79 ) $ (143 ) PROGRESS ENERGY First Second Third Fourth (in millions) Quarter Quarter Quarter Quarter Total 2017 Operating revenues $ 2,179 $ 2,392 $ 2,864 $ 2,348 $ 9,783 Operating income 487 591 657 493 2,228 Net income 201 277 343 447 1,268 Net income attributable to Parent 199 274 341 444 1,258 2016 Operating revenues $ 2,332 $ 2,348 $ 2,965 $ 2,208 $ 9,853 Operating income 475 560 814 292 2,141 Income from continuing operations 212 274 449 104 1,039 Net income 212 274 449 106 1,041 Net income attributable to Parent 209 272 446 104 1,031 The following table includes unusual or infrequently occurring items in each quarter during the two most recently completed fiscal years. All amounts discussed below are pretax. First Second Third Fourth (in millions) Quarter Quarter Quarter Quarter Total 2017 Costs to Achieve Piedmont Merger (see Note 2) $ (4 ) $ (7 ) $ (6 ) $ (6 ) $ (23 ) Regulatory Settlements (see Note 4) — — (135 ) (23 ) (158 ) Impacts of the Tax Act (see Note 22) — — — 246 246 Total $ (4 ) $ (7 ) $ (141 ) $ 217 $ 65 2016 Costs to Achieve Mergers $ (7 ) $ (8 ) $ (10 ) $ (44 ) $ (69 ) Cost Savings Initiatives (see Note 19) (8 ) (8 ) (10 ) (14 ) (40 ) Total $ (15 ) $ (16 ) $ (20 ) $ (58 ) $ (109 ) DUKE ENERGY PROGRESS First Second Third Fourth (in millions) Quarter Quarter Quarter Quarter Total 2017 Operating revenues $ 1,219 $ 1,199 $ 1,460 $ 1,251 $ 5,129 Operating income 286 282 411 256 1,235 Net income 147 154 246 168 715 2016 Operating revenues $ 1,307 $ 1,213 $ 1,583 $ 1,174 $ 5,277 Operating income 258 255 438 135 1,086 Net income 137 131 271 60 599 The following table includes unusual or infrequently occurring items in each quarter during the two most recently completed fiscal years. All amounts discussed below are pretax. First Second Third Fourth (in millions) Quarter Quarter Quarter Quarter Total 2017 Costs to Achieve Piedmont Merger (see Note 2) $ (2 ) $ (4 ) $ (4 ) $ (4 ) $ (14 ) Regulatory Settlements (see Note 4) — — — (23 ) (23 ) Impacts of the Tax Act (see Note 22) — — — 40 40 Total $ (2 ) $ (4 ) $ (4 ) $ 13 $ 3 2016 Costs to Achieve Mergers $ (5 ) $ (5 ) $ (6 ) $ (40 ) $ (56 ) Cost Savings Initiatives (see Note 19) (5 ) (5 ) (7 ) (6 ) (23 ) Total $ (10 ) $ (10 ) $ (13 ) $ (46 ) $ (79 ) DUKE ENERGY FLORIDA First Second Third Fourth (in millions) Quarter Quarter Quarter Quarter Total 2017 Operating revenues $ 959 $ 1,191 $ 1,401 $ 1,095 $ 4,646 Operating income 196 306 240 234 976 Net income 90 158 120 344 712 2016 Operating revenues $ 1,024 $ 1,133 $ 1,381 $ 1,030 $ 4,568 Operating income 213 300 373 155 1,041 Net income 110 171 206 64 551 The following table includes unusual or infrequently occurring items in each quarter during the two most recently completed fiscal years. All amounts discussed below are pretax. First Second Third Fourth (in millions) Quarter Quarter Quarter Quarter Total 2017 Costs to Achieve Piedmont Merger (see Note 2) $ (2 ) $ (3 ) $ (2 ) $ (2 ) $ (9 ) Regulatory Settlements (see Note 4) — — (135 ) — (135 ) Impacts of the Tax Act (see Note 22) — — — 226 226 Total $ (2 ) $ (3 ) $ (137 ) $ 224 $ 82 2016 Costs to Achieve Mergers $ (2 ) $ (3 ) $ (4 ) $ (4 ) $ (13 ) Cost Savings Initiatives (see Note 19) (2 ) (3 ) (3 ) (9 ) (17 ) Total $ (4 ) $ (6 ) $ (7 ) $ (13 ) $ (30 ) DUKE ENERGY OHIO First Second Third Fourth (in millions) Quarter Quarter Quarter Quarter Total 2017 Operating revenues $ 518 $ 437 $ 471 $ 497 $ 1,923 Operating income 83 65 102 76 326 Loss from discontinued operations, net of tax — — (1 ) — (1 ) Net income 42 30 55 65 192 2016 Operating revenues $ 516 $ 428 $ 489 $ 511 $ 1,944 Operating income 96 55 106 90 347 Income from discontinued operations, net of tax 2 — 34 — 36 Net income 59 23 89 57 228 The following table includes unusual or infrequently occurring items in each quarter during the two most recently completed fiscal years. All amounts discussed below are pretax. First Second Third Fourth (in millions) Quarter Quarter Quarter Quarter Total 2017 Costs to Achieve Piedmont Merger (see Note 2) $ (1 ) $ (1 ) $ (2 ) $ (2 ) $ (6 ) Impacts of the Tax Act (see Note 22) — — — 23 23 Total $ (1 ) $ (1 ) $ (2 ) $ 21 $ 17 2016 Costs to Achieve Mergers $ (1 ) $ (1 ) $ (2 ) $ (2 ) $ (6 ) Cost Savings Initiatives (see Note 19) (1 ) (1 ) — (1 ) (3 ) Total $ (2 ) $ (2 ) $ (2 ) $ (3 ) $ (9 ) DUKE ENERGY INDIANA First Second Third Fourth (in millions) Quarter Quarter Quarter Quarter Total 2017 Operating revenues $ 758 $ 742 $ 802 $ 745 $ 3,047 Operating income 186 210 230 170 796 Net income 91 106 121 36 354 2016 Operating revenues $ 714 $ 702 $ 809 $ 733 $ 2,958 Operating income 176 174 239 176 765 Net income 95 85 129 72 381 The following table includes unusual or infrequently occurring items in each quarter during the two most recently completed fiscal years. All amounts discussed below are pretax. First Second Third Fourth (in millions) Quarter Quarter Quarter Quarter Total 2017 Costs to Achieve Piedmont Merger (see Note 2) $ (1 ) $ (2 ) $ (2 ) $ (1 ) $ (6 ) Impacts of the Tax Act (see Note 22) — — — (55 ) (55 ) Total $ (1 ) $ (2 ) $ (2 ) $ (56 ) $ (61 ) 2016 Costs to Achieve Mergers $ (1 ) $ (2 ) $ (3 ) $ (3 ) $ (9 ) Cost Savings Initiatives (see Note 19) (1 ) (4 ) (1 ) (1 ) (7 ) Total $ (2 ) $ (6 ) $ (4 ) $ (4 ) $ (16 ) PIEDMONT The following tables include data for Piedmont's fiscal years ending December 31, 2017, and October 31, 2016. First Second Third Fourth (in millions) Quarter Quarter Quarter Quarter Total 2017 Operating revenues $ 500 $ 201 $ 183 $ 444 $ 1,328 Operating income (loss) 170 5 (4 ) 115 286 Net income (loss) 95 (8 ) (11 ) 63 139 2016 Operating revenues $ 464 $ 353 $ 160 $ 172 $ 1,149 Operating income (loss) 171 104 — (50 ) 225 Net income (loss) 98 63 (7 ) 39 193 For the two months ended December 31, 2016, Piedmont's operating revenues, operating income, and net income were $322 million , $96 million and $54 million , respectively. The following table includes unusual or infrequently occurring items in each quarter during the two most recently completed fiscal years. All amounts discussed below are pretax. First Second Third Fourth (in millions) Quarter Quarter Quarter Quarter Total 2017 Costs to Achieve Piedmont Merger (see Note 2) $ (6 ) $ (13 ) $ (8 ) $ (19 ) $ (46 ) Impacts of the Tax Act (see Note 22) — — — 2 2 Total $ (6 ) $ (13 ) $ (8 ) $ (17 ) $ (44 ) 2016 Costs to Achieve Mergers $ (6 ) $ (2 ) $ (1 ) $ (53 ) $ (62 ) For the two months ended December 31, 2016, Piedmont's costs to achieve merger were $7 million .

Summary of Significant Accoun35

Summary of Significant Accounting Policies (Policy)	12 Months Ended
	Dec. 31, 2017
Policy Text Block [Line Items]
Nature of Operations and Basis of Consolidation	Nature of Operations and Basis of Consolidation Duke Energy Corporation (collectively with its subsidiaries, Duke Energy) is an energy company headquartered in Charlotte, North Carolina, subject to regulation by the Federal Energy Regulatory Commission (FERC). Duke Energy operates in the United States (U.S.) primarily through its direct and indirect subsidiaries. Certain Duke Energy subsidiaries are also subsidiary registrants, including Duke Energy Carolinas, LLC (Duke Energy Carolinas); Progress Energy, Inc. (Progress Energy); Duke Energy Progress, LLC (Duke Energy Progress); Duke Energy Florida, LLC (Duke Energy Florida); Duke Energy Ohio, Inc. (Duke Energy Ohio); Duke Energy Indiana, LLC (Duke Energy Indiana) and Piedmont Natural Gas Company, Inc. (Piedmont). When discussing Duke Energy’s consolidated financial information, it necessarily includes the results of its seven separate subsidiary registrants (collectively referred to as the Subsidiary Registrants), which along with Duke Energy, are collectively referred to as the Duke Energy Registrants. In October 2016, Duke Energy completed the acquisition of Piedmont. Duke Energy's consolidated financial statements include Piedmont's results of operations and cash flows activity subsequent to the acquisition date. Effective November 1, 2016, Piedmont's fiscal year-end was changed from October 31 to December 31, the year-end of Duke Energy. A transition report was filed on Form 10-Q (Form 10-QT) as of December 31, 2016, for the transition period from November 1, 2016, to December 31, 2016. See Note 2 for additional information regarding the acquisition. In December 2016, Duke Energy completed an exit of the Latin American market to focus on its domestic regulated business, which was further bolstered by the acquisition of Piedmont. The sale of the International Energy business segment, excluding an equity method investment in National Methanol Company (NMC), was completed through two transactions including a sale of assets in Brazil to China Three Gorges (Luxembourg) Energy S.à.r.l. (CTG) and a sale of Duke Energy's remaining Latin American assets in Peru, Chile, Ecuador, Guatemala, El Salvador and Argentina to ISQ Enerlam Aggregator, L.P. and Enerlam (UK) Holding Ltd. (I Squared) (collectively, the International Disposal Group). See Note 2 for additional information on the sale of International Energy. The information in these combined notes relates to each of the Duke Energy Registrants as noted in the Index to Combined Notes to Consolidated Financial Statements. However, none of the Subsidiary Registrants make any representation as to information related solely to Duke Energy or the Subsidiary Registrants of Duke Energy other than itself. These Consolidated Financial Statements include, after eliminating intercompany transactions and balances, the accounts of the Duke Energy Registrants and subsidiaries where the respective Duke Energy Registrants have control. These Consolidated Financial Statements also reflect the Duke Energy Registrants’ proportionate share of certain jointly owned generation and transmission facilities. Substantially all of the Subsidiary Registrants' operations qualify for regulatory accounting. Duke Energy Carolinas is a regulated public utility primarily engaged in the generation, transmission, distribution and sale of electricity in portions of North Carolina and South Carolina. Duke Energy Carolinas is subject to the regulatory provisions of the North Carolina Utilities Commission (NCUC), Public Service Commission of South Carolina (PSCSC), U.S. Nuclear Regulatory Commission (NRC) and FERC. Progress Energy is a public utility holding company headquartered in Raleigh, North Carolina, subject to regulation by FERC. Progress Energy conducts operations through its wholly owned subsidiaries, Duke Energy Progress and Duke Energy Florida. Duke Energy Progress is a regulated public utility primarily engaged in the generation, transmission, distribution and sale of electricity in portions of North Carolina and South Carolina. Duke Energy Progress is subject to the regulatory provisions of the NCUC, PSCSC, NRC and FERC. Duke Energy Florida is a regulated public utility primarily engaged in the generation, transmission, distribution and sale of electricity in portions of Florida. Duke Energy Florida is subject to the regulatory provisions of the Florida Public Service Commission (FPSC), NRC and FERC. Duke Energy Ohio is a regulated public utility primarily engaged in the transmission and distribution of electricity in portions of Ohio and Kentucky, the generation and sale of electricity in portions of Kentucky and the transportation and sale of natural gas in portions of Ohio and Kentucky. Duke Energy Ohio conducts competitive auctions for retail electricity supply in Ohio whereby the energy price is recovered from retail customers and recorded in Operating Revenues on the Consolidated Statements of Operations and Comprehensive Income. Operations in Kentucky are conducted through its wholly owned subsidiary, Duke Energy Kentucky, Inc. (Duke Energy Kentucky). References herein to Duke Energy Ohio collectively include Duke Energy Ohio and its subsidiaries, unless otherwise noted. Duke Energy Ohio is subject to the regulatory provisions of the Public Utilities Commission of Ohio (PUCO), Kentucky Public Service Commission (KPSC) and FERC. On April 2, 2015, Duke Energy completed the sale of its nonregulated Midwest generation business, which sold power into wholesale energy markets, to a subsidiary of Dynegy Inc. (Dynegy). For further information about the sale of the Midwest Generation business, refer to Note 2 . Substantially all of Duke Energy Ohio's operations that remain after the sale qualify for regulatory accounting. Duke Energy Indiana is a regulated public utility primarily engaged in the generation, transmission, distribution and sale of electricity in portions of Indiana. Duke Energy Indiana is subject to the regulatory provisions of the Indiana Utility Regulatory Commission (IURC) and FERC. Piedmont is a regulated public utility primarily engaged in the distribution of natural gas in portions of North Carolina, South Carolina and Tennessee. Piedmont is subject to the regulatory provisions of the NCUC, PSCSC, Tennessee Public Utility Commission (TPUC) and FERC. Certain prior year amounts have been reclassified to conform to the current year presentation.
Discontinued Operations	Discontinued Operations The results of operations of the International Disposal Group as well as Duke Energy Ohio's nonregulated Midwest Generation business and Duke Energy Retail Sales, LLC (collectively, Midwest Generation Disposal Group) have been classified as Discontinued Operations on Duke Energy's Consolidated Statements of Operations. Duke Energy has elected to present cash flows of discontinued operations combined with cash flows of continuing operations. Unless otherwise noted, the notes to these consolidated financial statements exclude amounts related to discontinued operations for all periods presented. See Note 2 for additional information.
Use of Estimates	Use of Estimates In preparing financial statements that conform to generally accepted accounting principles (GAAP) in the U.S., the Duke Energy Registrants must make estimates and assumptions that affect the reported amounts of assets and liabilities, the reported amounts of revenues and expenses and the disclosure of contingent assets and liabilities at the date of the financial statements. Actual results could differ from those estimates.
Regulatory Accounting	Regulatory Accounting The majority of the Duke Energy Registrants’ operations are subject to price regulation for the sale of electricity and natural gas by state utility commissions or FERC. When prices are set on the basis of specific costs of the regulated operations and an effective franchise is in place such that sufficient natural gas or electric services can be sold to recover those costs, the Duke Energy Registrants apply regulatory accounting. Regulatory accounting changes the timing of the recognition of costs or revenues relative to a company that does not apply regulatory accounting. As a result, regulatory assets and regulatory liabilities are recognized on the Consolidated Balance Sheets. Regulatory assets and liabilities are amortized consistent with the treatment of the related cost in the ratemaking process. See Note 4 for further information. Regulatory accounting rules also require recognition of a disallowance (also called "impairment") loss if it becomes probable that part of the cost of a plant under construction (or a recently completed plant or an abandoned plant) will be disallowed for ratemaking purposes and a reasonable estimate of the amount of the disallowance can be made. These disallowances can require judgments on allowed future rate recovery. When it becomes probable that regulated generation, transmission or distribution assets will be abandoned, the cost of the asset is removed from plant in service. The value that may be retained as a regulatory asset on the balance sheet for the abandoned property is dependent upon amounts that may be recovered through regulated rates, including any return. As such, an impairment charge could be partially or fully offset by the establishment of a regulatory asset if rate recovery is probable. The impairment for a disallowance of costs for regulated plants under construction, recently completed or abandoned is based on discounted cash flows.
Regulated Fuel Costs and Purchased Power	Regulated Fuel and Purchased Gas Adjustment Clauses The Duke Energy Registrants utilize cost-tracking mechanisms, commonly referred to as fuel adjustment clauses or purchased gas adjustment clauses (PGA). These clauses allow for the recovery of fuel and fuel-related costs, portions of purchased power, natural gas costs and hedging costs through surcharges on customer rates. The difference between the costs incurred and the surcharge revenues is recorded either as an adjustment to Operating Revenues, Operating Expenses – Fuel used in electric generation or Operating Expenses – Cost of natural gas on the Consolidated Statements of Operations, with an off-setting impact on regulatory assets or liabilities
Cash and Cash Equivalents	Cash and Cash Equivalents All highly liquid investments with maturities of three months or less at the date of acquisition are considered cash equivalents.
Restricted Cash	Restricted Cash The Duke Energy Registrants have restricted cash related primarily to collateral assets, escrow deposits and variable interest entities (VIEs). Restricted cash balances are reflected in Other within Current Assets and in Other within Other Noncurrent Assets on the Consolidated Balance Sheets. At December 31, 2017 , and 2016 , Duke Energy had restricted cash totaling $147 million and $137 million , respectively.
Inventory	Inventory Inventory is used for operations and is recorded primarily using the average cost method. Inventory related to regulated operations is valued at historical cost. Inventory related to nonregulated operations is valued at the lower of cost or market. Materials and supplies are recorded as inventory when purchased and subsequently charged to expense or capitalized to property, plant and equipment when installed. Inventory, including excess or obsolete inventory, is written-down to the lower of cost or market value. Once inventory has been written-down, it creates a new cost basis for the inventory that is not subsequently written-up. Provisions for inventory write-offs were not material at December 31, 2017 , and 2016 . The components of inventory are presented in the tables below.
Investments in Debt and Equity Securities	Investments in Debt and Equity Securities The Duke Energy Registrants classify investments into two categories – trading and available-for-sale. Both categories are recorded at fair value on the Consolidated Balance Sheets. Realized and unrealized gains and losses on trading securities are included in earnings. For certain investments of regulated operations, such as substantially all of the Nuclear Decommissioning Trust Funds (NDTF), realized and unrealized gains and losses (including any other-than-temporary impairments (OTTIs)) on available-for-sale securities are recorded as a regulatory asset or liability. Otherwise, unrealized gains and losses are included in Accumulated Other Comprehensive Income (AOCI), unless other-than-temporarily impaired. OTTIs for equity securities and the credit loss portion of debt securities of nonregulated operations are included in earnings. Investments in debt and equity securities are classified as either current or noncurrent based on management’s intent and ability to sell these securities, taking into consideration current market liquidity. See Note 15 for further information.
Goodwill and Intangible Assets	Goodwill and Intangible Assets Goodwill Effective with Piedmont's change in fiscal year end to December 31, as discussed above, Piedmont changed the date of its annual impairment testing of goodwill from October 31 to August 31 to align with the other Duke Energy Registrants. Duke Energy, Progress Energy, Duke Energy Ohio and Piedmont perform annual goodwill impairment tests as of August 31 each year at the reporting unit level, which is determined to be an operating segment or one level below. Duke Energy, Progress Energy, Duke Energy Ohio and Piedmont update these tests between annual tests if events or circumstances occur that would more likely than not reduce the fair value of a reporting unit below its carrying value. Intangible Assets Intangible assets are included in Other in Other Noncurrent Assets on the Consolidated Balance Sheets. Generally, intangible assets are amortized using an amortization method that reflects the pattern in which the economic benefits of the intangible asset are consumed or on a straight-line basis if that pattern is not readily determinable. Amortization of intangibles is reflected in Depreciation and amortization on the Consolidated Statements of Operations. Intangible assets are subject to impairment testing and if impaired, the carrying value is accordingly reduced. Emission allowances permit the holder of the allowance to emit certain gaseous byproducts of fossil fuel combustion, including sulfur dioxide (SO 2 ) and nitrogen oxide (NO X ). Allowances are issued by the U.S. Environmental Protection Agency (EPA) at zero cost and may also be bought and sold via third-party transactions. Allowances allocated to or acquired by the Duke Energy Registrants are held primarily for consumption. Carrying amounts for emission allowances are based on the cost to acquire the allowances or, in the case of a business combination, on the fair value assigned in the allocation of the purchase price of the acquired business. Emission allowances are expensed to Fuel used in electric generation and purchased power on the Consolidated Statements of Operations. Renewable energy certificates are used to measure compliance with renewable energy standards and are held primarily for consumption. See Note 11 for further information.
Long-Lived Asset Impairments	Long-Lived Asset Impairments The Duke Energy Registrants evaluate long-lived assets, excluding goodwill, for impairment when circumstances indicate the carrying value of those assets may not be recoverable. An impairment exists when a long-lived asset’s carrying value exceeds the estimated undiscounted cash flows expected to result from the use and eventual disposition of the asset. The estimated cash flows may be based on alternative expected outcomes that are probability weighted. If the carrying value of the long-lived asset is not recoverable based on these estimated future undiscounted cash flows, the carrying value of the asset is written-down to its then-current estimated fair value and an impairment charge is recognized. The Duke Energy Registrants assess fair value of long-lived assets using various methods, including recent comparable third-party sales, internally developed discounted cash flow analysis and analysis from outside advisors. Triggering events to reassess cash flows may include, but are not limited to, significant changes in commodity prices, the condition of an asset or management’s interest in selling the asset.
Property, Plant and Equipment	Property, Plant and Equipment Property, plant and equipment are stated at the lower of depreciated historical cost net of any disallowances or fair value, if impaired. The Duke Energy Registrants capitalize all construction-related direct labor and material costs, as well as indirect construction costs such as general engineering, taxes and financing costs. See “Allowance for Funds Used During Construction (AFUDC) and Interest Capitalized” for information on capitalized financing costs. Costs of renewals and betterments that extend the useful life of property, plant and equipment are also capitalized. The cost of repairs, replacements and major maintenance projects, which do not extend the useful life or increase the expected output of the asset, are expensed as incurred. Depreciation is generally computed over the estimated useful life of the asset using the composite straight-line method. Depreciation studies are conducted periodically to update composite rates and are approved by state utility commissions and/or the FERC when required. The composite weighted average depreciation rates, excluding nuclear fuel, are included in the table that follows. In general, when the Duke Energy Registrants retire regulated property, plant and equipment, the original cost plus the cost of retirement, less salvage value, is charged to accumulated depreciation. However, when it becomes probable the asset will be retired substantially in advance of its original expected useful life or is abandoned, the cost of the asset and the corresponding accumulated depreciation is recognized as a separate asset. If the asset is still in operation, the net amount is classified as Generation facilities to be retired, net on the Consolidated Balance Sheets. If the asset is no longer operating, the net amount is classified in Regulatory assets on the Consolidated Balance Sheets if deemed recoverable (see discussion of long-lived asset impairments above). When it becomes probable an asset will be abandoned, the cost of the asset and accumulated depreciation is reclassified to Regulatory assets on the Consolidated Balance Sheets for amounts recoverable in rates. The carrying value of the asset is based on historical cost if the Duke Energy Registrants are allowed to recover the remaining net book value and a return equal to at least the incremental borrowing rate. If not, an impairment is recognized to the extent the net book value of the asset exceeds the present value of future revenues discounted at the incremental borrowing rate. When the Duke Energy Registrants sell entire regulated operating units, or retire or sell nonregulated properties, the original cost and accumulated depreciation and amortization balances are removed from Property, Plant and Equipment on the Consolidated Balance Sheets. Any gain or loss is recorded in earnings, unless otherwise required by the applicable regulatory body. See Note 10 for further information.
Nuclear Fuel	Nuclear Fuel Nuclear fuel is classified as Property, Plant and Equipment on the Consolidated Balance Sheets, except for Duke Energy Florida. Nuclear fuel amounts at Duke Energy Florida were reclassified to Regulatory assets pursuant to the Revised and Restated Stipulation and Settlement Agreement approved in November 2013 among Duke Energy Florida, the Florida Office of Public Counsel (Florida OPC) and other customer advocates (the 2013 Settlement). Nuclear fuel in the front-end fuel processing phase is considered work in progress and not amortized until placed in service. Amortization of nuclear fuel is included within Fuel used in electric generation and purchased power on the Consolidated Statements of Operations. Amortization is recorded using the units-of-production method.
Allowance for Funds Used During Construction (AFUDC) and Interest Capitalized	Allowance for Funds Used During Construction and Interest Capitalized For regulated operations, the debt and equity costs of financing the construction of property, plant and equipment are reflected as AFUDC and capitalized as a component of the cost of property, plant and equipment. AFUDC equity is reported on the Consolidated Statements of Operations as non-cash income in Other income and expenses, net. AFUDC debt is reported as a non-cash offset to Interest Expense. After construction is completed, the Duke Energy Registrants are permitted to recover these costs through their inclusion in rate base and the corresponding subsequent depreciation or amortization of those regulated assets. AFUDC equity, a permanent difference for income taxes, reduces the effective tax rate (ETR) when capitalized and increases the ETR when depreciated or amortized. See Note 22 for additional information. For nonregulated operations, interest is capitalized during the construction phase with an offsetting non-cash credit to Interest Expense on the Consolidated Statements of Operations.
Asset Retirement Obligations	Asset Retirement Obligations Asset retirement obligations (AROs) are recognized for legal obligations associated with the retirement of property, plant and equipment. Substantially all AROs are related to regulated operations. When recording an ARO, the present value of the projected liability is recognized in the period in which it is incurred, if a reasonable estimate of fair value can be made. The liability is accreted over time. For operating plants, the present value of the liability is added to the cost of the associated asset and depreciated over the remaining life of the asset. For retired plants, the present value of the liability is recorded as a regulatory asset unless determined not to be recoverable. The present value of the initial obligation and subsequent updates are based on discounted cash flows, which include estimates regarding timing of future cash flows, selection of discount rates and cost escalation rates, among other factors. These estimates are subject to change. Depreciation expense is adjusted prospectively for any changes to the carrying amount of the associated asset. The Duke Energy Registrants receive amounts to fund the cost of the ARO for regulated operations through a combination of regulated revenues and earnings on the NDTF. As a result, amounts recovered in regulated revenues, earnings on the NDTF, accretion expense and depreciation of the associated asset are netted and deferred as a regulatory asset or liability. Obligations for nuclear decommissioning are based on site-specific cost studies. Duke Energy Carolinas and Duke Energy Progress assume prompt dismantlement of the nuclear facilities after operations are ceased. Duke Energy Florida assumes Crystal River Unit 3 Nuclear Plant (Crystal River Unit 3) will be placed into a safe storage configuration until eventual dismantlement is completed by 2074. Duke Energy Carolinas, Duke Energy Progress and Duke Energy Florida also assume that spent fuel will be stored on-site until such time that it can be transferred to a yet to be built U.S. Department of Energy (DOE) facility. Obligations for closure of ash basins are based upon discounted cash flows of estimated costs for site-specific plans, if known, or probability weightings of the potential closure methods if the closure plans are under development and multiple closure options are being considered and evaluated on a site-by-site basis. See Note 9 for additional information
Revenue Recognition and Unbilled Revenue	Revenue Recognition and Unbilled Revenue Revenues on sales of electricity and natural gas are recognized when service is provided or the product is delivered. Unbilled revenues are recognized by applying customer billing rates to the estimated volumes of energy or natural gas delivered but not yet billed. Unbilled revenues can vary significantly from period to period as a result of seasonality, weather, customer usage patterns, customer mix, average price in effect for customer classes, timing of rendering customer bills and meter reading schedules, and the impact of weather normalization or margin decoupling mechanisms.
Derivatives and Hedging	Derivatives and Hedging Derivative and non-derivative instruments may be used in connection with commodity price and interest rate activities, including swaps, futures, forwards and options. All derivative instruments, except those that qualify for the normal purchase/normal sale (NPNS) exception, are recorded on the Consolidated Balance Sheets at fair value. Qualifying derivative instruments may be designated as either cash flow hedges or fair value hedges. Other derivative instruments (undesignated contracts) either have not been designated or do not qualify as hedges. The effective portion of the change in the fair value of cash flow hedges is recorded in AOCI. The effective portion of the change in the fair value of a fair value hedge is offset in net income by changes in the hedged item. For activity subject to regulatory accounting, gains and losses on derivative contracts are reflected as regulatory assets or liabilities and not as other comprehensive income or current period income. As a result, changes in fair value of these derivatives have no immediate earnings impact. Formal documentation, including transaction type and risk management strategy, is maintained for all contracts accounted for as a hedge. At inception and at least every three months thereafter, the hedge contract is assessed to see if it is highly effective in offsetting changes in cash flows or fair values of hedged items. See Note 14 for further information.
Captive Insurance Reserves	Captive Insurance Reserves Duke Energy has captive insurance subsidiaries that provide coverage, on an indemnity basis, to the Subsidiary Registrants as well as certain third parties, on a limited basis, for financial losses, primarily related to property, workers’ compensation and general liability. Liabilities include provisions for estimated losses incurred but not yet reported (IBNR), as well as estimated provisions for known claims. IBNR reserve estimates are primarily based upon historical loss experience, industry data and other actuarial assumptions. Reserve estimates are adjusted in future periods as actual losses differ from experience. Duke Energy, through its captive insurance entities, also has reinsurance coverage with third parties for certain losses above a per occurrence and/or aggregate retention. Receivables for reinsurance coverage are recognized when realization is deemed probable.
Unamortized Debt Premium, Discount and Expense	Unamortized Debt Premium, Discount and Expense Premiums, discounts and expenses incurred with the issuance of outstanding long-term debt are amortized over the term of the debt issue. The gain or loss on extinguishment associated with refinancing higher-cost debt obligations in the regulated operations is amortized. Amortization expense is recorded as Interest Expense in the Consolidated Statements of Operations and is reflected as Depreciation, amortization and accretion within Net cash provided by operating activities on the Consolidated Statements of Cash Flows. Premiums, discounts and expenses are presented as an adjustment to the carrying value of the debt amount and included in Long-Term Debt on the Consolidated Balance Sheets presented.
Loss Contingencies and Environmental Liabilities	Loss Contingencies and Environmental Liabilities Contingent losses are recorded when it is probable a loss has occurred and can be reasonably estimated. When a range of the probable loss exists and no amount within the range is a better estimate than any other amount, the minimum amount in the range is recorded. Unless otherwise required by GAAP, legal fees are expensed as incurred. Environmental liabilities are recorded on an undiscounted basis when environmental remediation or other liabilities become probable and can be reasonably estimated. Environmental expenditures related to past operations that do not generate current or future revenues are expensed. Environmental expenditures related to operations that generate current or future revenues are expensed or capitalized, as appropriate. Certain environmental expenditures receive regulatory accounting treatment and are recorded as regulatory assets. See Notes 4 and 5 for further information.
Pension and Other Post-Retirement Benefit Plans	Pension and Other Post-Retirement Benefit Plans Duke Energy maintains qualified, non-qualified and other post-retirement benefit plans. Eligible employees of the Subsidiary Registrants participate in the respective qualified, non-qualified and other post-retirement benefit plans and the Subsidiary Registrants are allocated their proportionate share of benefit costs. See Note 21 for further information, including significant accounting policies associated with these plans.
Severance and Special Termination Benefits	Severance and Special Termination Benefits Duke Energy has severance plans under which, in general, the longer a terminated employee worked prior to termination the greater the amount of severance benefits. A liability for involuntary severance is recorded once an involuntary severance plan is committed to by management if involuntary severances are probable and can be reasonably estimated. For involuntary severance benefits incremental to its ongoing severance plan benefits, the fair value of the obligation is expensed at the communication date if there are no future service requirements or over the required future service period. From time to time, Duke Energy offers special termination benefits under voluntary severance programs. Special termination benefits are recorded immediately upon employee acceptance absent a significant retention period. Otherwise, the cost is recorded over the remaining service period. Employee acceptance of voluntary severance benefits is determined by management based on the facts and circumstances of the benefits being offered. See Note 19 for further information.
Guarantees	Guarantees If necessary, liabilities are recognized at the time of issuance or material modification of a guarantee for the estimated fair value of the obligation it assumes. Fair value is estimated using a probability-weighted approach. The obligation is reduced over the term of the guarantee or related contract in a systematic and rational method as risk is reduced. Any additional contingent loss for guarantee contracts subsequent to the initial recognition of a liability is accounted for and recognized at the time a loss is probable and can be reasonably estimated. See Note 7 for further information.
Stock-Based Compensation	Stock-Based Compensation Stock-based compensation represents costs related to stock-based awards granted to employees and Duke Energy Board of Directors (Board of Directors) members. Duke Energy recognizes stock-based compensation based upon the estimated fair value of awards, net of estimated forfeitures at the date of issuance. The recognition period for these costs begins at either the applicable service inception date or grant date and continues throughout the requisite service period. Compensation cost is recognized as expense or capitalized as a component of property, plant and equipment. See Note 20 for further information.
Income Taxes	Income Taxes Duke Energy and its subsidiaries file a consolidated federal income tax return and other state and foreign jurisdictional returns. The Subsidiary Registrants are parties to a tax-sharing agreement with Duke Energy. Income taxes recorded represent amounts the Subsidiary Registrants would incur as separate C-Corporations. Deferred income taxes have been provided for temporary differences between GAAP and tax bases of assets and liabilities because the differences create taxable or tax-deductible amounts for future periods. Investment tax credits (ITCs) associated with regulated operations are deferred and amortized as a reduction of income tax expense over the estimated useful lives of the related properties. Accumulated deferred income taxes are valued using the enacted tax rate expected to apply to taxable income in the periods in which the deferred tax asset or liability is expected to be settled or realized. In the event of a change in tax rates, deferred tax assets and liabilities are remeasured as of the enactment date of the new rate. To the extent that the change in the value of the deferred tax represents an obligation to customers, the impact of the remeasurement is deferred to a regulatory liability. Remaining impacts are recorded in income from continuing operations. Other impacts of the Tax Act have been recorded on a provisional basis, see Note 22, “Income Taxes,” for additional information. If Duke Energy's estimate of the tax effect of reversing temporary differences is not reflective of actual outcomes, is modified to reflect new developments or interpretations of the tax law, revised to incorporate new accounting principles, or changes in the expected timing or manner of the reversal then Duke Energy's results of operations could be impacted. Tax-related interest and penalties are recorded in Interest Expense and Other Income and Expenses, net in the Consolidated Statements of Operations. See Note 22 for further information.
Accounting for Renewable Energy Tax Credits and Cash Grants	Accounting for Renewable Energy Tax Credits When Duke Energy receives ITCs on wind or solar facilities, it reduces the basis of the property recorded on the Consolidated Balance Sheets by the amount of the ITC and, therefore, the ITC benefit is ultimately recognized in the statement of operations through reduced depreciation expense. Additionally, certain tax credits and government grants result in an initial tax depreciable base in excess of the book carrying value by an amount equal to one half of the ITC. Deferred tax benefits are recorded as a reduction to income tax expense in the period that the basis difference is created.
Excise Taxes	Excise Taxes Certain excise taxes levied by state or local governments are required to be paid even if not collected from the customer. These taxes are recognized on a gross basis. Otherwise, the taxes are accounted for net. Excise taxes accounted for on a gross basis within both Operating Revenues and Property and other taxes in the Consolidated Statements of Operations were as follows.
Dividend Restrictions and Unappropriated Retained Earnings	Dividend Restrictions and Unappropriated Retained Earnings Duke Energy does not have any legal, regulatory or other restrictions on paying common stock dividends to shareholders. However, as further described in Note 4 , due to conditions established by regulators in conjunction with merger transaction approvals, Duke Energy Carolinas, Duke Energy Progress, Duke Energy Ohio, Duke Energy Indiana and Piedmont have restrictions on paying dividends or otherwise advancing funds to Duke Energy. At December 31, 2017 , and 2016 , an insignificant amount of Duke Energy’s consolidated Retained earnings balance represents undistributed earnings of equity method investments.
New Accounting Standards	New Accounting Standards The new accounting standards adopted for 2017 and 2016 had no material impact on the presentation or results of operations, cash flows or financial position of the Duke Energy Registrants. The following accounting standards were adopted by the Duke Energy Registrants during 2017. Stock-Based Compensation and Income Taxes. In first quarter 2017, Duke Energy adopted Financial Accounting Standards Board (FASB) guidance, which revised the accounting for stock-based compensation and the associated income taxes. The adopted guidance changed certain aspects of accounting for stock-based payment awards to employees including the accounting for income taxes and classification on the Consolidated Statements of Cash Flows. The primary impact to Duke Energy as a result of implementing this guidance was a cumulative-effect adjustment to retained earnings for tax benefits not previously recognized and additional income tax expense for the 12 months ended December 31, 2017. See the Duke Energy Consolidated Statements of Changes in Equity for further information. Goodwill Impairment. In January 2017, the FASB issued revised guidance for the subsequent measurement of goodwill. Under the guidance, a company will recognize an impairment to goodwill for the amount by which a reporting unit's carrying value exceeds the reporting unit's fair value, not to exceed the amount of goodwill allocated to that reporting unit. Duke Energy early adopted this guidance for the 2017 annual goodwill impairment test. The following new accounting standards have been issued, but have not yet been adopted by the Duke Energy Registrants, as of December 31, 2017 . Revenue from Contracts with Customers . In May 2014, the FASB issued revised accounting guidance for revenue recognition from contracts with customers. The core principle of this guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The amendments in this update also require disclosure of sufficient information to allow users to understand the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. Duke Energy has identified material revenue streams, which served as the basis for accounting analysis and documentation of the impact of this guidance on revenue recognition. The accounting analysis included reviewing representative contracts and tariffs for each material revenue stream. Most of Duke Energy’s revenue will be in scope of the new guidance. The majority of our sales, including energy provided to residential customers, are from tariff offerings that provide natural gas or electricity without a defined contractual term ("at-will"). For such arrangements, revenue from contracts with customers will be equivalent to the electricity or natural gas supplied and billed in that period (including estimated billings). As such, there will not be a significant shift in the timing or pattern of revenue recognition for such sales. Also included in the accounting analysis was the evaluation of certain long-term revenue streams including electric wholesale contracts and renewables power purchase agreements (PPAs). For such arrangements, Duke Energy does not expect material changes to the pattern of revenue recognition on the registrants. In addition, Duke Energy has monitored the activities of the power and utilities industry revenue recognition task force including draft accounting positions released in October 2017 and the impact, if any, on Duke Energy’s specific contracts and conclusions. Potential revisions to processes, policies and controls, primarily related to evaluating supplemental disclosures required as a result of adopting this guidance, will be evaluated and implemented as necessary. Some revenue arrangements, such as alternative revenue programs and certain PPAs accounted for as leases, are excluded from the scope of the new revenue recognition guidance and, therefore, will be accounted for and evaluated for separate presentation and disclosure under other relevant accounting guidance. Duke Energy intends to use the modified retrospective method of adoption effective January 1, 2018. Under the modified retrospective method of adoption, prior year reported results are not restated and a cumulative-effect adjustment, if applicable, is recorded to retained earnings at January 1, 2018, as if the standard had always been in effect. In addition, disclosures, if applicable, include a comparison to what would have been reported for 2018 under the previous revenue recognition rules to assist financial statement users in understanding how revenue recognition has changed as a result of this standard and to facilitate comparability with prior year reported results, which are not restated under the modified retrospective approach as described above. Duke Energy will utilize certain practical expedients including applying this guidance to open contracts at the date of adoption and recognizing revenues for certain contracts under the invoice practical expedient, which allows revenue recognition to be consistent with invoiced amounts (including estimated billings) provided certain criteria are met, including consideration of whether the invoiced amounts reasonably represent the value provided to customers. While the adoption of this guidance is not expected to have a material impact on either the timing or amount of revenues recognized in Duke Energy's financial statements, Duke Energy anticipates additional disclosures around the nature, amount, timing and uncertainty of our revenues and cash flows arising from contracts with customers. Duke Energy continues to evaluate what information will be most useful for users of the financial statements, including information already provided in disclosures outside of the financial statement footnotes. These additional disclosures are expected to include the disaggregation of revenues by customer class. Financial Instruments Classification and Measurement. In January 2016, the FASB issued revised accounting guidance for the classification and measurement of financial instruments. Changes in the fair value of all equity securities will be required to be recorded in net income. Current GAAP allows some changes in fair value for available-for-sale equity securities to be recorded in AOCI. Additional disclosures will be required to present separately the financial assets and financial liabilities by measurement category and form of financial asset. An entity's equity investments that are accounted for under the equity method of accounting are not included within the scope of the new guidance. For Duke Energy, the revised accounting guidance is effective for interim and annual periods beginning January 1, 2018, by recording a cumulative effect adjustment to retained earnings as of January 1, 2018. This guidance is expected to have minimal impact on the Duke Energy Registrant's Consolidated Statements of Operations and Comprehensive Income as changes in the fair value of most of the Duke Energy Registrants' available-for-sale equity securities are deferred as regulatory assets or liabilities pursuant to accounting guidance for regulated operations. Leases. In February 2016, the FASB issued revised accounting guidance for leases. The core principle of this guidance is that a lessee should recognize the assets and liabilities that arise from leases on the balance sheet. For Duke Energy, this guidance is effective for interim and annual periods beginning January 1, 2019. The guidance is applied using a modified retrospective approach. Upon adoption, Duke Energy expects to elect the practical expedients, which would require no reassessment of whether existing contracts are or contain leases as well as no reassessment of lease classification for existing leases. Additionally, we expect to adopt the optional transition practical expedient allowing the entity not to reassess the accounting for land easements that currently exist at the adoption of the lease standard on January 1, 2019. Duke Energy is currently evaluating the financial statement impact of adopting this standard and is continuing to monitor industry implementation issues, including easements, pole attachments and renewable PPAs. Other than an expected increase in assets and liabilities, the ultimate impact of the new standard has not yet been determined. Significant system enhancements, including additional processes and controls, will be required to facilitate the identification, tracking and reporting of potential leases based upon requirements of the new lease standard. Duke Energy has begun the implementation of a third-party software tool to help with the adoption and ongoing accounting under the new standard. Statement of Cash Flows. In November 2016, the FASB issued revised accounting guidance to reduce diversity in practice for the presentation and classification of restricted cash on the statement of cash flows. Under the updated guidance, restricted cash and restricted cash equivalents will be included within beginning-of-period and end-of-period cash and cash equivalents on the statement of cash flows. For Duke Energy, this guidance is effective for the interim and annual periods beginning January 1, 2018. The guidance will be applied using a retrospective transition method to each period presented. Upon adoption by Duke Energy, the revised guidance will result in a change to the amount of cash and cash equivalents and restricted cash explained when reconciling the beginning-of-period and end-of-period total amounts shown on the Consolidated Statement of Cash Flows. Prior to adoption, the Duke Energy Registrants reflect changes in restricted cash within Cash Flows from Investing Activities and within Cash Flows from Operating Activities on the Consolidated Statement of Cash Flows. As a result of this change, our Cash and cash equivalents balance on the Consolidated Statement of Cash Flows as of December 31, 2017 will change by $147 million . Retirement Benefits. In March 2017, the FASB issued revised accounting guidance for the presentation of net periodic costs related to benefit plans. Current GAAP permits the aggregation of all the components of net periodic costs on the Consolidated Statement of Operations and does not require the disclosure of the location of net periodic costs on the Consolidated Statement of Operations. Under the amended guidance, the service cost component of net periodic costs must be included within Operating Income within the same line as other compensation expenses. All other components of net periodic costs must be outside of Operating Income. In addition, the updated guidance permits only the service cost component of net periodic costs to be capitalized to Inventory or Property, Plant and Equipment. This represents a change from current GAAP, which permits all components of net periodic costs to be capitalized. These amendments should be applied retrospectively for the presentation of the various components of net periodic costs and prospectively for the change in eligible costs to be capitalized. The guidance allows for a practical expedient that permits a company to use amounts disclosed in prior-period financial statements as the estimation basis for applying the retrospective presentation requirements. For Duke Energy, this guidance is effective for interim and annual periods beginning January 1, 2018. Duke Energy currently presents the total non-capitalized net periodic costs within Operation, maintenance and other on the Consolidated Statement of Operations. The adoption of this guidance will result in a retrospective change to reclassify the presentation of the non-service cost (benefit) components of net periodic costs to Other income and expenses. Duke Energy intends to utilize the practical expedient for retrospective presentation. The change in net periodic costs eligible for capitalization is applicable prospectively. Since Duke Energy’s service cost component is expected to be greater than the total net periodic costs, the change will result in increased capitalization of net periodic costs, higher Operation, maintenance and other and higher Other income and expenses. The resulting impact to Duke Energy is expected to be an immaterial increase in Net Income resulting from the limitation of eligible capitalization of net periodic costs to the service cost component, which is larger than the total net periodic costs.
Duke Energy Ohio [Member]
Policy Text Block [Line Items]
Revenue Recognition and Unbilled Revenue	Additionally, Duke Energy Ohio and Duke Energy Indiana sell, on a revolving basis, nearly all of their retail accounts receivable, including receivables for unbilled revenues, to an affiliate, Cinergy Receivables Company LLC (CRC) and account for the transfers of receivables as sales. Accordingly, the receivables sold are not reflected on the Consolidated Balance Sheets of Duke Energy Ohio and Duke Energy Indiana. See Note 17 for further information.
Duke Energy Indiana [Member]
Policy Text Block [Line Items]
Revenue Recognition and Unbilled Revenue	Additionally, Duke Energy Ohio and Duke Energy Indiana sell, on a revolving basis, nearly all of their retail accounts receivable, including receivables for unbilled revenues, to an affiliate, Cinergy Receivables Company LLC (CRC) and account for the transfers of receivables as sales. Accordingly, the receivables sold are not reflected on the Consolidated Balance Sheets of Duke Energy Ohio and Duke Energy Indiana. See Note 17 for further information.

Summary of Significant Accoun36

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2017
Organization And Basis Of Presentation [Line Items]
Schedule of Credit Losses for Financing Receivables, Current [Table Text Block]	Allowances for doubtful accounts are presented in the following table. December 31, (in millions) 2017 2016 2015 Allowance for Doubtful Accounts Duke Energy $ 14 $ 14 $ 12 Duke Energy Carolinas 2 2 3 Progress Energy 4 6 6 Duke Energy Progress 1 4 4 Duke Energy Florida 3 2 2 Duke Energy Ohio 3 2 2 Duke Energy Indiana 2 1 1 Piedmont (a) 2 3 Allowance for Doubtful Accounts – VIEs Duke Energy $ 54 $ 54 $ 53 Duke Energy Carolinas 7 7 7 Progress Energy 7 7 8 Duke Energy Progress 5 5 5 Duke Energy Florida 2 2 3 (a) Piedmont's allowance for doubtful accounts was $2 million as of October 31, 2016, and 2015.
Schedule of Current and Noncurrent Assets and Liabilities	The following table provides a description of amounts included in Other within Current Assets or Current Liabilities that exceed 5 percent of total Current Assets or Current Liabilities on the Duke Energy Registrants' Consolidated Balance Sheets at either December 31, 2017 , or 2016 . December 31, (in millions) Location 2017 2016 Duke Energy Accrued compensation Current Liabilities $ 757 $ 765 Duke Energy Carolinas Accrued compensation Current Liabilities $ 252 $ 248 Customer deposits Current Liabilities 121 155 Progress Energy Income taxes receivable Current Assets $ 278 $ 19 Customer deposits Current Liabilities 338 363 Duke Energy Progress Customer deposits Current Liabilities $ 129 $ 141 Accrued compensation Current Liabilities 132 135 Duke Energy Florida Customer deposits Current Liabilities $ 208 $ 222 Duke Energy Ohio Income taxes receivable Current Assets $ 36 $ 16 Customer deposits Current Liabilities 46 62 Duke Energy Indiana Customer deposits Current Liabilities $ 45 $ 44 Piedmont Income taxes receivable Current Assets $ 43 $ 9
Schedule of Net Income Amounts Attributable to Controlling Interests	The following table presents Net Income Attributable to Duke Energy Corporation for continuing operations and discontinued operations for the years ended December 31, 2016, and 2015. Year ended December 31, (in millions) 2016 2015 Income from Continuing Operations $ 2,578 $ 2,654 Income from Continuing Operations Attributable to Noncontrolling Interests 7 9 Income from Continuing Operations Attributable to Duke Energy Corporation $ 2,571 $ 2,645 (Loss) Income From Discontinued Operations, net of tax $ (408 ) $ 177 Income from Discontinued Operations Attributable to Noncontrolling Interests, net of tax 11 6 (Loss) Income From Discontinued Operations Attributable to Duke Energy Corporation, net of tax $ (419 ) $ 171 Net Income $ 2,170 $ 2,831 Net Income Attributable to Noncontrolling Interests 18 15 Net Income Attributable to Duke Energy Corporation $ 2,152 $ 2,816
Components Of Inventory	The components of inventory are presented in the tables below. December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Materials and supplies $ 2,293 $ 744 $ 1,118 $ 774 $ 343 $ 82 $ 309 $ 2 Coal 603 192 255 139 116 17 139 — Natural gas, oil and other 354 35 219 104 115 34 2 64 Total inventory $ 3,250 $ 971 $ 1,592 $ 1,017 $ 574 $ 133 $ 450 $ 66 December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Materials and supplies $ 2,374 $ 767 $ 1,167 $ 813 $ 354 $ 84 $ 312 $ 1 Coal 774 251 314 148 166 19 190 — Natural gas, oil and other 374 37 236 115 121 34 2 65 Total inventory $ 3,522 $ 1,055 $ 1,717 $ 1,076 $ 641 $ 137 $ 504 $ 66
Schedule Of Property, Plant And Equipment	The composite weighted average depreciation rates, excluding nuclear fuel, are included in the table that follows. Years Ended December 31, 2017 2016 2015 Duke Energy 2.8 % 2.8 % 2.9 % Duke Energy Carolinas 2.8 % 2.8 % 2.8 % Progress Energy 2.6 % 2.7 % 2.6 % Duke Energy Progress 2.6 % 2.6 % 2.6 % Duke Energy Florida 2.8 % 2.8 % 2.7 % Duke Energy Ohio 2.8 % 2.6 % 2.7 % Duke Energy Indiana 3.0 % 3.1 % 3.0 % Piedmont (a) 2.3 % (a) Piedmont's weighted average depreciation rate was 2.4 percent , 2.4 percent , and 2.5 percent for the annualized two months ended December 31, 2016 and for the years ended October 31, 2016 and 2015, respectively. The following tables summarize the property, plant and equipment for Duke Energy and its subsidiary registrants. December 31, 2017 Estimated Useful Duke Duke Duke Duke Duke Life Duke Energy Progress Energy Energy Energy Energy (in millions) (Years) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Land $ 1,559 $ 467 $ 767 $ 424 $ 343 $ 134 $ 111 $ 41 Plant – Regulated Electric generation, distribution and transmission 8-100 93,687 35,657 39,419 24,502 14,917 4,870 13,741 — Natural gas transmission and distribution 12-80 8,292 — — — — 2,559 — 5,733 Other buildings and improvements 15-100 1,936 647 652 316 336 243 240 154 Plant – Nonregulated Electric generation, distribution and transmission (a) 5-30 4,273 — — — — — — — Other buildings and improvements 25-35 465 — — — — — — — Nuclear fuel 3,680 2,120 1,560 1,560 — — — — Equipment 3-55 2,122 402 555 416 139 348 169 266 Construction in process 6,995 2,614 3,059 1,434 1,625 350 416 231 Other 3-40 4,498 1,032 1,311 931 370 228 271 300 Total property, plant and equipment (b)(e) 127,507 42,939 47,323 29,583 17,730 8,732 14,948 6,725 Total accumulated depreciation – regulated (c)(d)(e) (39,742 ) (15,063 ) (15,857 ) (10,903 ) (4,947 ) (2,691 ) (4,662 ) (1,479 ) Total accumulated depreciation – nonregulated (d)(e) (1,795 ) — — — — — — — Generation facilities to be retired, net 421 — 421 421 — — — — Total net property, plant and equipment $ 86,391 $ 27,876 $ 31,887 $ 19,101 $ 12,783 $ 6,041 $ 10,286 $ 5,246 (a) Includes a pretax impairment charge of $58 million on a wholly owned non-contracted wind project. See discussion below. (b) Includes capitalized leases of $1,294 million , $81 million , $272 million , $139 million , $133 million , $80 million and $35 million at Duke Energy, Duke Energy Carolinas, Progress Energy, Duke Energy Progress, Duke Energy Florida, Duke Energy Ohio and Duke Energy Indiana, respectively, primarily within Plant – Regulated. The Progress Energy, Duke Energy Progress and Duke Energy Florida amounts are net of $114 million , $11 million and $103 million , respectively, of accumulated amortization of capitalized leases. (c) Includes $2,113 million , $1,283 million , $831 million and $831 million of accumulated amortization of nuclear fuel at Duke Energy, Duke Energy Carolinas, Progress Energy and Duke Energy Progress, respectively. (d) Includes accumulated amortization of capitalized leases of $57 million , $11 million , $21 million and $9 million at Duke Energy, Duke Energy Carolinas, Duke Energy Ohio and Duke Energy Indiana, respectively. (e) Includes gross property, plant and equipment cost of consolidated VIEs of $3,941 million and accumulated depreciation of consolidated VIEs of $598 million at Duke Energy. December 31, 2016 Estimated Useful Duke Duke Duke Duke Duke Life Duke Energy Progress Energy Energy Energy Energy (in millions) (Years) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Land $ 1,501 $ 432 $ 735 $ 393 $ 342 $ 150 $ 106 $ 39 Plant – Regulated Electric generation, distribution and transmission 8-100 89,864 34,515 37,596 23,683 13,913 4,593 13,160 — Natural gas transmission and distribution 12-67 7,738 — — — — 2,456 — 5,282 Other buildings and improvements 15-100 1,692 502 634 293 341 211 197 148 Plant – Nonregulated Electric generation, distribution and transmission 5-30 4,298 — — — — — — — Other buildings and improvements 25-35 421 — — — — — — — Nuclear fuel 3,572 2,092 1,480 1,480 — — — — Equipment 3-38 1,941 358 505 378 127 338 156 260 Construction in process 6,186 2,324 2,708 1,329 1,379 206 396 210 Other 5-40 4,184 904 1,206 863 332 172 226 235 Total property, plant and equipment (a)(d) 121,397 41,127 44,864 28,419 16,434 8,126 14,241 6,174 Total accumulated depreciation – regulated (b)(c)(d) (37,831 ) (14,365 ) (15,212 ) (10,561 ) (4,644 ) (2,579 ) (4,317 ) (1,360 ) Total accumulated depreciation – nonregulated (c)(d) (1,575 ) — — — — — — — Generation facilities to be retired, net 529 — 529 529 — — — — Total net property, plant and equipment $ 82,520 $ 26,762 $ 30,181 $ 18,387 $ 11,790 $ 5,547 $ 9,924 $ 4,814 (a) Includes capitalized leases of $1,355 million , $40 million , $288 million , $142 million , $146 million , $81 million and $35 million at Duke Energy, Duke Energy Carolinas, Progress Energy, Duke Energy Progress, Duke Energy Florida, Duke Energy Ohio and Duke Energy Indiana, respectively, primarily within Plant – Regulated. The Progress Energy, Duke Energy Progress and Duke Energy Florida amounts are net of $99 million , $9 million and $90 million , respectively, of accumulated amortization of capitalized leases. (b) Includes $1,922 million , $1,192 million , $730 million and $730 million of accumulated amortization of nuclear fuel at Duke Energy, Duke Energy Carolinas, Progress Energy and Duke Energy Progress, respectively. (c) Includes accumulated amortization of capitalized leases of $50 million , $9 million , $19 million and $8 million at Duke Energy, Duke Energy Carolinas, Duke Energy Ohio and Duke Energy Indiana, respectively. (d) Includes gross property, plant and equipment cost of consolidated VIEs of $2,591 million and accumulated depreciation of consolidated VIEs of $411 million at Duke Energy.
Schedule of Excise Taxes	Excise taxes accounted for on a gross basis within both Operating Revenues and Property and other taxes in the Consolidated Statements of Operations were as follows. Years Ended December 31, (in millions) 2017 2016 2015 Duke Energy $ 376 $ 362 $ 396 Duke Energy Carolinas 36 31 31 Progress Energy 220 213 229 Duke Energy Progress 19 18 16 Duke Energy Florida 201 195 213 Duke Energy Ohio 98 100 102 Duke Energy Indiana 20 17 34 Piedmont (a) 2 (a) Piedmont's excise taxes were immaterial for the two months ended December 31, 2016, and $2 million for the years ended October 31, 2016, and 2015.
Unbilled Revenues [Member]
Organization And Basis Of Presentation [Line Items]
Schedule Of Unbilled Revenues Within Receivables and Restricted Receivables	Unbilled revenues are included within Receivables and Receivables of VIEs on the Consolidated Balance Sheets as shown in the following table. December 31, (in millions) 2017 2016 Duke Energy $ 944 $ 831 Duke Energy Carolinas 342 313 Progress Energy 228 161 Duke Energy Progress 143 102 Duke Energy Florida 85 59 Duke Energy Ohio 4 2 Duke Energy Indiana 21 32 Piedmont 86 77 Additionally, Duke Energy Ohio and Duke Energy Indiana sell, on a revolving basis, nearly all of their retail accounts receivable, including receivables for unbilled revenues, to an affiliate, Cinergy Receivables Company LLC (CRC) and account for the transfers of receivables as sales. Accordingly, the receivables sold are not reflected on the Consolidated Balance Sheets of Duke Energy Ohio and Duke Energy Indiana. See Note 17 for further information. These receivables for unbilled revenues are shown in the table below. December 31, (in millions) 2017 2016 Duke Energy Ohio $ 104 $ 97 Duke Energy Indiana 132 123

Acquisitions and Dispositions (

Acquisitions and Dispositions (Tables)	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Schedule of Recognized Identified Assets Acquired	The purchase price allocation of the Piedmont acquisition is as follows: (in millions) Current assets $ 497 Property, plant and equipment, net 4,714 Goodwill 3,353 Other long-term assets 804 Total assets 9,368 Current liabilities, including current maturities of long-term debt 576 Long-term liabilities 1,790 Long-term debt 2,002 Total liabilities 4,368 Total purchase price $ 5,000
Business Acquisition, Pro Forma Information	This information has been presented for illustrative purposes only and is not necessarily indicative of the consolidated results of operations that would have been achieved or the future consolidated results of operations of Duke Energy. Years Ended December 31, (in millions) 2016 2015 Operating Revenues $ 23,504 $ 23,570 Net Income Attributable to Duke Energy Corporation 2,442 2,877
Disposal Groups, Including Discontinued Operations	The following table summarizes the Midwest Generation Disposal Group activity recorded within discontinued operations. Duke Energy Duke Energy Ohio Years Ended December 31, Years Ended December 31, (in millions) 2016 2015 2016 2015 Operating Revenues $ — $ 543 $ — $ 412 Pretax Loss on disposal (a) — (45 ) — (52 ) Income (loss) before income taxes (b) $ — $ 59 $ — $ 44 Income tax (benefit) expense (c) (36 ) 26 (36 ) 21 Income (loss) from discontinued operations $ 36 $ 33 $ 36 $ 23 (a) The Loss on disposal includes impairments recorded to adjust the carrying amount of the assets to the estimated fair value of the business, based on the selling price to Dynegy less cost to sell. (b) 2015 amounts include the impact of an $81 million charge for the settlement agreement reached in a lawsuit related to the Midwest Generation Disposal Group. Refer to Note 5 for further information about the lawsuit. (c) 2016 amounts result from immaterial out of period deferred tax liability adjustments. The following table summarizes the (Loss) Income from Discontinued Operations, net of tax recorded on Duke Energy's Consolidated Statements of Operations for the years ended December 31, 2016, and 2015: Years Ended December 31, (in millions) 2016 2015 International Energy Disposal Group $ (534 ) $ 157 Midwest Generation Disposal Group 36 33 Other (a) 90 (13 ) (Loss) Income from Discontinued Operations, net of tax $ (408 ) $ 177 (a) Relates to previously sold businesses not related to the Disposal Groups. The amount for 2016 represents an income tax benefit resulting from immaterial out of period deferred tax liability adjustments. The amount for 2015 includes indemnifications provided for certain legal, tax and environmental matters and foreign currency translation adjustments. The following table presents the results of the International Disposal Group for the years ended December 31, 2016, and 2015, which are included in (Loss) Income from Discontinued Operations, net of tax in Duke Energy's Consolidated Statements of Operations. Years Ended December 31, (in millions) 2016 2015 Operating Revenues $ 988 $ 1,088 Fuel used in electric generation and purchased power 227 306 Cost of natural gas 43 53 Operation, maintenance and other 341 334 Depreciation and amortization (a) 62 92 Property and other taxes 15 7 Impairment charges (b) 194 13 (Loss) Gains on Sales of Other Assets and Other, net (3 ) 6 Other Income and Expenses, net 58 23 Interest Expense 82 85 Pretax loss on disposal (c) (514 ) — (Loss) Income before income taxes (d) (435 ) 227 Income tax expense (e)(f) 99 70 (Loss) Income from discontinued operations of the International Disposal Group $ (534 ) $ 157 (a) Upon meeting the criteria for assets held for sale, beginning in the fourth quarter of 2016 depreciation expense was ceased. (b) In conjunction with the advancements of marketing efforts during 2016, Duke Energy performed recoverability tests of the long-lived asset groups of International Energy. As a result, Duke Energy determined the carrying value of certain assets in Central America was not fully recoverable and recorded a pretax impairment charge of $194 million . The charge represents the excess of carrying value over the estimated fair value of the assets, which was based on a Level 3 Fair Value measurement that was primarily determined from the income approach using discounted cash flows but also considered market information obtained in 2016. (c) The pretax loss on disposal includes the recognition of cumulative foreign currency translation losses of $620 million as of the disposal date. See the Consolidated Statements of Changes in Equity for additional information. (d) Pretax (Loss) Income attributable to Duke Energy Corporation was $(445) million and $221 million for the years ended December 31, 2016 and 2015, respectively. (e) 2016 amount includes $126 million of income tax expense on the disposal, which primarily reflects in-country taxes incurred as a result of the sale. The after-tax loss on disposal was $640 million . (f) 2016 amount includes an income tax benefit of $95 million . See Note 22 , "Income Taxes," for additional information.
Schedule of Cash Flow, Supplemental Disclosures	The following table summarizes Duke Energy's cash flows from discontinued operations related to the International Disposal Group. Years Ended December 31, (in millions) 2016 2015 Cash flows provided by (used in): Operating activities $ 204 $ 248 Investing activities (434 ) 177

Business Segments (Tables)

Business Segments (Tables)	12 Months Ended
	Dec. 31, 2017
Segment Reporting Information [Line Items]
Business Segment Data	Business segment information is presented in the following tables. Segment assets presented exclude intercompany assets. Year Ended December 31, 2017 Electric Gas Total Utilities and Utilities and Commercial Reportable (in millions) Infrastructure Infrastructure Renewables Segments Other Eliminations Total Unaffiliated Revenues $ 21,300 $ 1,743 $ 460 $ 23,503 $ 62 $ — $ 23,565 Intersegment Revenues 31 93 — 124 76 (200 ) — Total Revenues $ 21,331 $ 1,836 $ 460 $ 23,627 $ 138 $ (200 ) $ 23,565 Interest Expense $ 1,240 $ 105 $ 87 $ 1,432 $ 574 $ (20 ) $ 1,986 Depreciation and amortization 3,010 231 155 3,396 131 — 3,527 Equity in earnings (losses) of unconsolidated affiliates 5 62 (5 ) 62 57 — 119 Income tax expense (benefit) (a) 1,355 116 (628 ) 843 353 — 1,196 Segment income (loss) (b)(c)(d) 3,210 319 441 3,970 (905 ) — 3,065 Add back noncontrolling interest component 5 Loss from discontinued operations, net of tax (6 ) Net income $ 3,064 Capital investments expenditures and acquisitions $ 7,024 $ 907 $ 92 $ 8,023 $ 175 $ — $ 8,198 Segment assets 119,423 11,462 4,156 135,041 2,685 188 137,914 (a) All segments include impacts of the Tax Cuts and Jobs Act (the Tax Act). Electric Utilities and Infrastructure includes a $231 million benefit, Gas Utilities and Infrastructure includes a $26 million benefit, Commercial Renewables includes a $442 million benefit and Other includes charges of $597 million . (b) Electric Utilities and Infrastructure includes after-tax regulatory settlement charges of $98 million . See Note 4 for additional information. (c) Commercial Renewables includes after-tax impairment charges of $74 million related to certain wind projects and the Energy Management Solutions reporting unit. See Notes 10 and 11 for additional information. (d) Other includes $64 million of after-tax costs to achieve the Piedmont merger. See Note 2 for additional information. Year Ended December 31, 2016 Electric Gas Total Utilities and Utilities and Commercial Reportable (in millions) Infrastructure Infrastructure Renewables Segments Other Eliminations Total Unaffiliated Revenues $ 21,336 $ 875 $ 484 $ 22,695 $ 48 $ — $ 22,743 Intersegment Revenues 30 26 — 56 69 (125 ) — Total Revenues $ 21,366 $ 901 $ 484 $ 22,751 $ 117 $ (125 ) $ 22,743 Interest Expense $ 1,136 $ 46 $ 53 $ 1,235 $ 693 $ (12 ) $ 1,916 Depreciation and amortization 2,897 115 130 3,142 152 — 3,294 Equity in earnings (losses) of unconsolidated affiliates (a) 5 19 (82 ) (58 ) 43 — (15 ) Income tax expense (benefit) 1,672 90 (160 ) 1,602 (446 ) — 1,156 Segment income (loss) (b)(c) 3,040 152 23 3,215 (645 ) 1 2,571 Add back noncontrolling interest component 7 Loss from discontinued operations, net of tax (d) (408 ) Net income $ 2,170 Capital investments expenditures and acquisitions (e) $ 6,649 $ 5,519 $ 857 $ 13,025 $ 190 $ — $ 13,215 Segment assets 114,993 10,760 4,377 130,130 2,443 188 132,761 (a) Commercial Renewables includes a pretax impairment charge of $71 million . See Note 12 for additional information. (b) Other includes $329 million of after-tax costs to achieve mergers. Refer to Note 2 for additional information on costs related to the Piedmont merger. (c) Other includes after-tax charges of $57 million related to cost savings initiatives. Refer to Note 19 for further information. (d) Includes a loss on sale of the International Disposal Group. Refer to Note 2 for further information. (e) Other includes $26 million of capital investments expenditures related to the International Disposal Group. Gas Utilities and Infrastructure includes the Piedmont acquisition of $5 billion . Refer to Note 2 for more information on the Piedmont acquisition. Year Ended December 31, 2015 Electric Gas Total Utilities and Utilities and Commercial Reportable (in millions) Infrastructure Infrastructure Renewables Segments Other Eliminations Total Unaffiliated Revenues $ 21,489 $ 536 $ 286 $ 22,311 $ 60 $ — $ 22,371 Intersegment Revenues 32 5 — 37 75 (112 ) — Total Revenues $ 21,521 $ 541 $ 286 $ 22,348 $ 135 $ (112 ) $ 22,371 Interest Expense $ 1,074 $ 25 $ 44 $ 1,143 $ 393 $ (9 ) $ 1,527 Depreciation and amortization 2,735 79 104 2,918 135 — 3,053 Equity in (losses) earnings of unconsolidated affiliates (2 ) 1 (6 ) (7 ) 76 — 69 Income tax expense (benefit) 1,602 44 (128 ) 1,518 (262 ) — 1,256 Segment income (loss) (a)(b)(c) 2,819 73 52 2,944 (299 ) — 2,645 Add back noncontrolling interest component 9 Income from discontinued operations, net of tax (d) 177 Net income $ 2,831 Capital investments expenditures and acquisitions (e) $ 6,852 $ 234 $ 1,019 $ 8,105 $ 258 $ — $ 8,363 Segment assets (f) 109,097 2,637 3,861 115,595 5,373 188 121,156 (a) Electric Utilities and Infrastructure includes an after-tax charge of $58 million related to the Edwardsport settlement. Refer to Note 4 for further information. (b) Other includes $60 million of after-tax costs to achieve mergers. (c) Other includes after-tax charges of $77 million related to cost savings initiatives. Refer to Note 19 for further information. (d) Includes the impact of a settlement agreement reached in a lawsuit related to the Midwest Generation Disposal Group. Refer to Note 5 for further information related to the lawsuit and Note 2 for further information on discontinued operations. (e) Other includes capital investment expenditures of $45 million related to the International Disposal Group. (f) Other includes Assets Held for Sale balances related to the International Disposal Group. Refer to Note 2 for further information.
Schedule of Revenue, By Products and Services	Products and Services The following table summarizes revenues of the reportable segments by type. Retail Wholesale Retail Total (in millions) Electric Electric Natural Gas Other Revenues 2017 Electric Utilities and Infrastructure $ 18,177 $ 2,104 $ — $ 1,050 $ 21,331 Gas Utilities and Infrastructure — — 1,732 104 1,836 Commercial Renewables — 375 — 85 460 Total Reportable Segments $ 18,177 $ 2,479 $ 1,732 $ 1,239 $ 23,627 2016 Electric Utilities and Infrastructure $ 18,338 $ 2,095 $ — $ 933 $ 21,366 Gas Utilities and Infrastructure — — 871 30 901 Commercial Renewables — 303 — 181 484 Total Reportable Segments $ 18,338 $ 2,398 $ 871 $ 1,144 $ 22,751 2015 Electric Utilities and Infrastructure $ 18,695 $ 2,014 $ — $ 812 $ 21,521 Gas Utilities and Infrastructure — — 546 (5 ) 541 Commercial Renewables — 245 — 41 286 Total Reportable Segments $ 18,695 $ 2,259 $ 546 $ 848 $ 22,348
Duke Energy Ohio [Member]
Segment Reporting Information [Line Items]
Business Segment Data	Year Ended December 31, 2017 Electric Gas Total Utilities and Utilities and Reportable (in millions) Infrastructure Infrastructure Segments Other Eliminations Total Total revenues $ 1,373 $ 508 $ 1,881 $ 42 $ — $ 1,923 Interest expense $ 62 $ 28 $ 90 $ 1 $ — $ 91 Depreciation and amortization 178 83 261 $ — — 261 Income tax expense (benefit) 40 39 79 $ (20 ) — 59 Segment income (loss) 138 85 223 $ (30 ) — 193 Loss from discontinued operations, net of tax (1 ) Net income $ 192 Capital expenditures $ 491 $ 195 $ 686 $ — $ — $ 686 Segment assets 5,066 2,758 7,824 66 (15 ) 7,875 Year Ended December 31, 2016 Electric Gas Total Utilities and Utilities and Reportable (in millions) Infrastructure Infrastructure Segments Other Eliminations Total Total revenues $ 1,410 $ 503 $ 1,913 $ 31 $ — $ 1,944 Interest expense $ 58 $ 27 $ 85 $ 1 $ — $ 86 Depreciation and amortization 151 80 231 2 — 233 Income tax expense (benefit) 55 44 99 (21 ) — 78 Segment income (loss) 154 77 231 (39 ) — 192 Income from discontinued operations, net of tax 36 Net income $ 228 Capital expenditures $ 322 $ 154 $ 476 $ — $ — $ 476 Segment assets 4,782 2,696 7,478 62 (12 ) 7,528 Year Ended December 31, 2015 Electric Gas Total Utilities and Utilities and Reportable (in millions) Infrastructure Infrastructure Segments Other Eliminations Total Total revenues $ 1,331 $ 541 $ 1,872 $ 33 $ — $ 1,905 Interest expense $ 53 $ 25 $ 78 $ 1 $ — $ 79 Depreciation and amortization 147 79 226 1 — 227 Income tax expense (benefit) 59 45 104 (23 ) — 81 Segment income (loss) 118 73 191 (41 ) (1 ) 149 Income from discontinued operations, net of tax 23 Net income $ 172 Capital expenditures $ 264 $ 135 $ 399 $ — $ — $ 399 Segment assets 4,534 2,516 7,050 56 (9 ) 7,097

Regulatory Matters (Tables)

Regulatory Matters (Tables)	12 Months Ended
	Dec. 31, 2017
Public Utilities, General Disclosures [Line Items]
Schedule of Regulatory Assets	The following tables present the regulatory assets and liabilities recorded on the Consolidated Balance Sheets of Duke Energy and Progress Energy. See separate tables below for balances by individual registrant. Duke Energy Progress Energy December 31, December 31, (in millions) 2017 2016 2017 2016 Regulatory Assets AROs – coal ash $ 4,025 $ 3,761 $ 1,984 $ 1,830 AROs – nuclear and other 852 684 655 569 Accrued pension and OPEB 2,249 2,387 906 882 Retired generation facilities 480 534 386 422 Debt fair value adjustment 1,197 1,313 — — Net regulatory asset related to income taxes — 894 — 231 Storm cost deferrals 531 153 526 148 Nuclear asset securitized balance, net 1,142 1,193 1,142 1,193 Hedge costs deferrals 234 217 94 91 Derivatives – natural gas supply contracts 142 187 — — Demand side management (DSM)/Energy efficiency (EE) 530 407 281 278 Grid modernization 39 65 — — Vacation accrual 213 196 42 38 Deferred fuel and purchased power 507 156 349 111 Nuclear deferral 119 226 35 134 Post-in-service carrying costs (PISCC) and deferred operating expenses 366 413 38 42 Transmission expansion obligation 46 71 — — Manufactured gas plant (MGP) 91 99 — — Advanced metering infrastructure (AMI) 362 218 150 — NCEMPA deferrals 53 51 53 51 East Bend deferrals 45 32 — — Deferred pipeline integrity costs 54 36 — — Amounts due from customers 64 66 — — Other 538 542 110 103 Total regulatory assets 13,879 13,901 6,751 6,123 Less: current portion 1,437 1,023 741 401 Total noncurrent regulatory assets $ 12,442 $ 12,878 $ 6,010 $ 5,722 Regulatory Liabilities Costs of removal $ 5,968 $ 5,613 $ 2,537 $ 2,198 ARO – nuclear and other 806 461 — — Net regulatory liability related to income taxes 8,113 — 2,802 — Amounts to be refunded to customers 10 45 — — Storm reserve 20 83 — 60 Accrued pension and OPEB 146 174 — — Deferred fuel and purchased power 47 192 1 81 Other 622 722 179 245 Total regulatory liabilities 15,732 7,290 5,519 2,584 Less: current portion 402 409 213 189 Total noncurrent regulatory liabilities $ 15,330 $ 6,881 $ 5,306 $ 2,395
Schedule Of Regulatory Liabilities	The following tables present the regulatory assets and liabilities recorded on the Consolidated Balance Sheets of Duke Energy and Progress Energy. See separate tables below for balances by individual registrant. Duke Energy Progress Energy December 31, December 31, (in millions) 2017 2016 2017 2016 Regulatory Assets AROs – coal ash $ 4,025 $ 3,761 $ 1,984 $ 1,830 AROs – nuclear and other 852 684 655 569 Accrued pension and OPEB 2,249 2,387 906 882 Retired generation facilities 480 534 386 422 Debt fair value adjustment 1,197 1,313 — — Net regulatory asset related to income taxes — 894 — 231 Storm cost deferrals 531 153 526 148 Nuclear asset securitized balance, net 1,142 1,193 1,142 1,193 Hedge costs deferrals 234 217 94 91 Derivatives – natural gas supply contracts 142 187 — — Demand side management (DSM)/Energy efficiency (EE) 530 407 281 278 Grid modernization 39 65 — — Vacation accrual 213 196 42 38 Deferred fuel and purchased power 507 156 349 111 Nuclear deferral 119 226 35 134 Post-in-service carrying costs (PISCC) and deferred operating expenses 366 413 38 42 Transmission expansion obligation 46 71 — — Manufactured gas plant (MGP) 91 99 — — Advanced metering infrastructure (AMI) 362 218 150 — NCEMPA deferrals 53 51 53 51 East Bend deferrals 45 32 — — Deferred pipeline integrity costs 54 36 — — Amounts due from customers 64 66 — — Other 538 542 110 103 Total regulatory assets 13,879 13,901 6,751 6,123 Less: current portion 1,437 1,023 741 401 Total noncurrent regulatory assets $ 12,442 $ 12,878 $ 6,010 $ 5,722 Regulatory Liabilities Costs of removal $ 5,968 $ 5,613 $ 2,537 $ 2,198 ARO – nuclear and other 806 461 — — Net regulatory liability related to income taxes 8,113 — 2,802 — Amounts to be refunded to customers 10 45 — — Storm reserve 20 83 — 60 Accrued pension and OPEB 146 174 — — Deferred fuel and purchased power 47 192 1 81 Other 622 722 179 245 Total regulatory liabilities 15,732 7,290 5,519 2,584 Less: current portion 402 409 213 189 Total noncurrent regulatory liabilities $ 15,330 $ 6,881 $ 5,306 $ 2,395
Schedule of Potential Plant Retirements	The table below contains the net carrying value of generating facilities planned for retirement or included in recent IRPs as evaluated for potential retirement due to a lack of requisite environmental control equipment. Dollar amounts in the table below are included in Net property, plant and equipment on the Consolidated Balance Sheets as of December 31, 2017 , and exclude capitalized asset retirement costs. Remaining Net Capacity Book Value (in MW) (in millions) Duke Energy Carolinas Allen Steam Station Units 1-3 (a) 585 $ 163 Progress Energy and Duke Energy Florida Crystal River Units 1 and 2 (b) 873 107 Duke Energy Indiana Gallagher Units 2 and 4 (c) 280 127 Total Duke Energy 1,738 $ 397 (a) Duke Energy Carolinas will retire Allen Steam Station Units 1 through 3 by December 31, 2024, as part of the resolution of a lawsuit involving alleged New Source Review violations. (b) Duke Energy Florida expects to retire these coal units by the end of 2018 to comply with environmental regulations. (c) Duke Energy Indiana committed to either retire or stop burning coal at Gallagher Units 2 and 4 by December 31, 2022, as part of the settlement of Edwardsport IGCC matters.
Duke Energy Carolinas [Member]
Public Utilities, General Disclosures [Line Items]
Schedule of Regulatory Assets	The following tables present the regulatory assets and liabilities recorded on Duke Energy Carolinas' Consolidated Balance Sheets. December 31, Earns/Pays Recovery/Refund (in millions) 2017 2016 a Return Period Ends Regulatory Assets (a) AROs - coal ash $ 1,645 $ 1,536 (i) (b) AROs - nuclear and other — 9 Accrued pension and OPEB 410 481 (j) Retired generation facilities (c) 29 39 X 2023 Net regulatory asset related to income taxes (d) — 484 Hedge costs deferrals (c) 109 93 X 2041 DSM/EE 210 122 (h) (h) Vacation accrual 83 76 (e) 2018 Deferred fuel and purchased power 140 — (f) 2018 Nuclear deferral 84 92 2019 PISCC (c) 35 70 X (b) AMI 185 172 X (b) Other 222 223 (b) Total regulatory assets 3,152 3,397 Less: current portion 299 238 Total noncurrent regulatory assets $ 2,853 $ 3,159 Regulatory Liabilities (a) Costs of removal (c) $ 2,054 $ 2,015 X (g) ARO - nuclear and other 806 461 (b) Net regulatory liability related to income taxes (d) 3,028 — (b) Storm reserve (c) 20 22 (b) Accrued pension and OPEB 44 46 (j) Deferred fuel and purchased power 46 105 (f) 2018 Other 359 352 (b) Total regulatory liabilities 6,357 3,001 Less: current portion 126 161 Total noncurrent regulatory liabilities $ 6,231 $ 2,840 (a) Regulatory assets and liabilities are excluded from rate base unless otherwise noted. (b) The expected recovery or refund period varies or has not been determined. (c) Included in rate base. (d) Includes regulatory liabilities related to the change in the North Carolina tax rate discussed in Note 22 . (e) Earns a return on outstanding balance in North Carolina. (f) Pays interest on over-recovered costs in North Carolina. Includes certain purchased power costs in North Carolina and South Carolina and costs of distributed energy in South Carolina. (g) Recovered over the life of the associated assets. (h) Includes incentives on DSM/EE investments and is recovered through an annual rider mechanism. (i) Earns a debt return on coal ash expenditures for North Carolina and South Carolina retail customers. (j) Recovered primarily over the average remaining service periods or life expectancies of employees covered by the benefit plans. See Note 21 for additional detail.
Schedule Of Regulatory Liabilities	The following tables present the regulatory assets and liabilities recorded on Duke Energy Carolinas' Consolidated Balance Sheets. December 31, Earns/Pays Recovery/Refund (in millions) 2017 2016 a Return Period Ends Regulatory Assets (a) AROs - coal ash $ 1,645 $ 1,536 (i) (b) AROs - nuclear and other — 9 Accrued pension and OPEB 410 481 (j) Retired generation facilities (c) 29 39 X 2023 Net regulatory asset related to income taxes (d) — 484 Hedge costs deferrals (c) 109 93 X 2041 DSM/EE 210 122 (h) (h) Vacation accrual 83 76 (e) 2018 Deferred fuel and purchased power 140 — (f) 2018 Nuclear deferral 84 92 2019 PISCC (c) 35 70 X (b) AMI 185 172 X (b) Other 222 223 (b) Total regulatory assets 3,152 3,397 Less: current portion 299 238 Total noncurrent regulatory assets $ 2,853 $ 3,159 Regulatory Liabilities (a) Costs of removal (c) $ 2,054 $ 2,015 X (g) ARO - nuclear and other 806 461 (b) Net regulatory liability related to income taxes (d) 3,028 — (b) Storm reserve (c) 20 22 (b) Accrued pension and OPEB 44 46 (j) Deferred fuel and purchased power 46 105 (f) 2018 Other 359 352 (b) Total regulatory liabilities 6,357 3,001 Less: current portion 126 161 Total noncurrent regulatory liabilities $ 6,231 $ 2,840 (a) Regulatory assets and liabilities are excluded from rate base unless otherwise noted. (b) The expected recovery or refund period varies or has not been determined. (c) Included in rate base. (d) Includes regulatory liabilities related to the change in the North Carolina tax rate discussed in Note 22 . (e) Earns a return on outstanding balance in North Carolina. (f) Pays interest on over-recovered costs in North Carolina. Includes certain purchased power costs in North Carolina and South Carolina and costs of distributed energy in South Carolina. (g) Recovered over the life of the associated assets. (h) Includes incentives on DSM/EE investments and is recovered through an annual rider mechanism. (i) Earns a debt return on coal ash expenditures for North Carolina and South Carolina retail customers. (j) Recovered primarily over the average remaining service periods or life expectancies of employees covered by the benefit plans. See Note 21 for additional detail.
Progress Energy [Member]
Public Utilities, General Disclosures [Line Items]
Schedule of Regulatory Assets	The following tables present the regulatory assets and liabilities recorded on the Consolidated Balance Sheets of Duke Energy and Progress Energy. See separate tables below for balances by individual registrant. Duke Energy Progress Energy December 31, December 31, (in millions) 2017 2016 2017 2016 Regulatory Assets AROs – coal ash $ 4,025 $ 3,761 $ 1,984 $ 1,830 AROs – nuclear and other 852 684 655 569 Accrued pension and OPEB 2,249 2,387 906 882 Retired generation facilities 480 534 386 422 Debt fair value adjustment 1,197 1,313 — — Net regulatory asset related to income taxes — 894 — 231 Storm cost deferrals 531 153 526 148 Nuclear asset securitized balance, net 1,142 1,193 1,142 1,193 Hedge costs deferrals 234 217 94 91 Derivatives – natural gas supply contracts 142 187 — — Demand side management (DSM)/Energy efficiency (EE) 530 407 281 278 Grid modernization 39 65 — — Vacation accrual 213 196 42 38 Deferred fuel and purchased power 507 156 349 111 Nuclear deferral 119 226 35 134 Post-in-service carrying costs (PISCC) and deferred operating expenses 366 413 38 42 Transmission expansion obligation 46 71 — — Manufactured gas plant (MGP) 91 99 — — Advanced metering infrastructure (AMI) 362 218 150 — NCEMPA deferrals 53 51 53 51 East Bend deferrals 45 32 — — Deferred pipeline integrity costs 54 36 — — Amounts due from customers 64 66 — — Other 538 542 110 103 Total regulatory assets 13,879 13,901 6,751 6,123 Less: current portion 1,437 1,023 741 401 Total noncurrent regulatory assets $ 12,442 $ 12,878 $ 6,010 $ 5,722 Regulatory Liabilities Costs of removal $ 5,968 $ 5,613 $ 2,537 $ 2,198 ARO – nuclear and other 806 461 — — Net regulatory liability related to income taxes 8,113 — 2,802 — Amounts to be refunded to customers 10 45 — — Storm reserve 20 83 — 60 Accrued pension and OPEB 146 174 — — Deferred fuel and purchased power 47 192 1 81 Other 622 722 179 245 Total regulatory liabilities 15,732 7,290 5,519 2,584 Less: current portion 402 409 213 189 Total noncurrent regulatory liabilities $ 15,330 $ 6,881 $ 5,306 $ 2,395
Schedule Of Regulatory Liabilities	The following tables present the regulatory assets and liabilities recorded on the Consolidated Balance Sheets of Duke Energy and Progress Energy. See separate tables below for balances by individual registrant. Duke Energy Progress Energy December 31, December 31, (in millions) 2017 2016 2017 2016 Regulatory Assets AROs – coal ash $ 4,025 $ 3,761 $ 1,984 $ 1,830 AROs – nuclear and other 852 684 655 569 Accrued pension and OPEB 2,249 2,387 906 882 Retired generation facilities 480 534 386 422 Debt fair value adjustment 1,197 1,313 — — Net regulatory asset related to income taxes — 894 — 231 Storm cost deferrals 531 153 526 148 Nuclear asset securitized balance, net 1,142 1,193 1,142 1,193 Hedge costs deferrals 234 217 94 91 Derivatives – natural gas supply contracts 142 187 — — Demand side management (DSM)/Energy efficiency (EE) 530 407 281 278 Grid modernization 39 65 — — Vacation accrual 213 196 42 38 Deferred fuel and purchased power 507 156 349 111 Nuclear deferral 119 226 35 134 Post-in-service carrying costs (PISCC) and deferred operating expenses 366 413 38 42 Transmission expansion obligation 46 71 — — Manufactured gas plant (MGP) 91 99 — — Advanced metering infrastructure (AMI) 362 218 150 — NCEMPA deferrals 53 51 53 51 East Bend deferrals 45 32 — — Deferred pipeline integrity costs 54 36 — — Amounts due from customers 64 66 — — Other 538 542 110 103 Total regulatory assets 13,879 13,901 6,751 6,123 Less: current portion 1,437 1,023 741 401 Total noncurrent regulatory assets $ 12,442 $ 12,878 $ 6,010 $ 5,722 Regulatory Liabilities Costs of removal $ 5,968 $ 5,613 $ 2,537 $ 2,198 ARO – nuclear and other 806 461 — — Net regulatory liability related to income taxes 8,113 — 2,802 — Amounts to be refunded to customers 10 45 — — Storm reserve 20 83 — 60 Accrued pension and OPEB 146 174 — — Deferred fuel and purchased power 47 192 1 81 Other 622 722 179 245 Total regulatory liabilities 15,732 7,290 5,519 2,584 Less: current portion 402 409 213 189 Total noncurrent regulatory liabilities $ 15,330 $ 6,881 $ 5,306 $ 2,395
Duke Energy Progress [Member]
Public Utilities, General Disclosures [Line Items]
Schedule of Regulatory Assets	The following tables present the regulatory assets and liabilities recorded on Duke Energy Progress' Consolidated Balance Sheets. December 31, Earns/Pays Recovery/Refund (in millions) 2017 2016 a Return Period Ends Regulatory Assets (a) AROs - coal ash $ 1,975 $ 1,822 (i) (b) AROs - nuclear and other 359 275 (c) Accrued pension and OPEB 430 423 (l) Retired generation facilities 170 165 X 2023 Net regulatory asset related to income taxes — 7 (d) Storm cost deferrals (e) 150 148 X (b) Hedge costs deferrals 64 66 (b) DSM/EE (f) 264 263 (j) 2018 Vacation accrual 42 38 2018 Deferred fuel and purchased power 130 24 (g) 2018 Nuclear deferral 35 38 2019 PISCC and deferred operating expenses 38 42 X 2054 AMI 75 — (b) NCEMPA deferrals 53 51 (h) 2042 Other 74 69 (b) Total regulatory assets 3,859 3,431 Less: current portion 352 188 Total noncurrent regulatory assets $ 3,507 $ 3,243 Regulatory Liabilities (a) Costs of removal $ 2,122 $ 1,840 X (k) Net regulatory liability related to income taxes 1,854 — (b) Deferred fuel and purchased power 1 64 (g) 2018 Other 161 200 (b) Total regulatory liabilities 4,138 2,104 Less: current portion 139 158 Total noncurrent regulatory liabilities $ 3,999 $ 1,946 (a) Regulatory assets and liabilities are excluded from rate base unless otherwise noted. (b) The expected recovery or refund period varies or has not been determined. (c) Recovery period for costs related to nuclear facilities runs through the decommissioning period of each unit. (d) Recovery over the life of the associated assets. Includes regulatory liabilities related to the change in the North Carolina tax rate discussed in Note 22 . (e) South Carolina storm costs are included in rate base. (f) Included in rate base. (g) Pays interest on over-recovered costs in North Carolina. Includes certain purchased power costs in North Carolina and South Carolina and costs of distributed energy in South Carolina. (h) South Carolina retail allocated costs are earning a return. (i) Earns a debt return on coal ash expenditures for North Carolina and South Carolina retail customers. (j) Includes incentives on DSM/EE investments. (k) Recovered over the life of the associated assets. (l) Recovered primarily over the average remaining service periods or life expectancies of employees covered by the benefit plans. See Note 21 for additional detail.
Schedule Of Regulatory Liabilities	The following tables present the regulatory assets and liabilities recorded on Duke Energy Progress' Consolidated Balance Sheets. December 31, Earns/Pays Recovery/Refund (in millions) 2017 2016 a Return Period Ends Regulatory Assets (a) AROs - coal ash $ 1,975 $ 1,822 (i) (b) AROs - nuclear and other 359 275 (c) Accrued pension and OPEB 430 423 (l) Retired generation facilities 170 165 X 2023 Net regulatory asset related to income taxes — 7 (d) Storm cost deferrals (e) 150 148 X (b) Hedge costs deferrals 64 66 (b) DSM/EE (f) 264 263 (j) 2018 Vacation accrual 42 38 2018 Deferred fuel and purchased power 130 24 (g) 2018 Nuclear deferral 35 38 2019 PISCC and deferred operating expenses 38 42 X 2054 AMI 75 — (b) NCEMPA deferrals 53 51 (h) 2042 Other 74 69 (b) Total regulatory assets 3,859 3,431 Less: current portion 352 188 Total noncurrent regulatory assets $ 3,507 $ 3,243 Regulatory Liabilities (a) Costs of removal $ 2,122 $ 1,840 X (k) Net regulatory liability related to income taxes 1,854 — (b) Deferred fuel and purchased power 1 64 (g) 2018 Other 161 200 (b) Total regulatory liabilities 4,138 2,104 Less: current portion 139 158 Total noncurrent regulatory liabilities $ 3,999 $ 1,946 (a) Regulatory assets and liabilities are excluded from rate base unless otherwise noted. (b) The expected recovery or refund period varies or has not been determined. (c) Recovery period for costs related to nuclear facilities runs through the decommissioning period of each unit. (d) Recovery over the life of the associated assets. Includes regulatory liabilities related to the change in the North Carolina tax rate discussed in Note 22 . (e) South Carolina storm costs are included in rate base. (f) Included in rate base. (g) Pays interest on over-recovered costs in North Carolina. Includes certain purchased power costs in North Carolina and South Carolina and costs of distributed energy in South Carolina. (h) South Carolina retail allocated costs are earning a return. (i) Earns a debt return on coal ash expenditures for North Carolina and South Carolina retail customers. (j) Includes incentives on DSM/EE investments. (k) Recovered over the life of the associated assets. (l) Recovered primarily over the average remaining service periods or life expectancies of employees covered by the benefit plans. See Note 21 for additional detail.
Duke Energy Florida [Member]
Public Utilities, General Disclosures [Line Items]
Schedule of Regulatory Assets	The following tables present the regulatory assets and liabilities recorded on Duke Energy Florida's Consolidated Balance Sheets. December 31, Earns/Pays Recovery/Refund (in millions) 2017 2016 a Return Period Ends Regulatory Assets (a) AROs - coal ash (c) $ 9 $ 8 X (b) AROs - nuclear and other (c) 296 294 X (b) Accrued pension and OPEB (c) 476 458 X (h) Retired generation facilities (c) 216 257 X (b) Net regulatory asset related to income taxes (c) — 224 X (d) Storm cost deferrals (c) 376 — (f) 2021 Nuclear asset securitized balance, net 1,142 1,193 2036 Hedge costs deferrals 30 25 2018 DSM/EE (c) 17 15 X 2018 Deferred fuel and purchased power (c) 219 87 (g) 2019 Nuclear deferral — 96 AMI (c) 75 — X 2032 Other 36 36 (b) Total regulatory assets 2,892 2,693 Less: current portion 389 213 Total noncurrent regulatory assets $ 2,503 $ 2,480 Regulatory Liabilities (a) Costs of removal (c) $ 415 $ 358 (e) (b) Net regulatory liability related to income taxes (c) 948 — (b) Storm reserve (c) — 60 Deferred fuel and purchased power (c) — 17 (g) Other 18 44 (b) Total regulatory liabilities 1,381 479 Less: current portion 74 31 Total noncurrent regulatory liabilities $ 1,307 $ 448 (a) Regulatory assets and liabilities are excluded from rate base unless otherwise noted. (b) The expected recovery or refund period varies or has not been determined. (c) Included in rate base. (d) Recovery over the life of the associated assets. (e) Certain costs earn a return. (f) Earns a debt return/interest once collections begin. (g) Earns commercial paper rate. (h) Recovered primarily over the average remaining service periods or life expectancies of employees covered by the benefit plans. See Note 21 for additional detail.
Schedule Of Regulatory Liabilities	The following tables present the regulatory assets and liabilities recorded on Duke Energy Florida's Consolidated Balance Sheets. December 31, Earns/Pays Recovery/Refund (in millions) 2017 2016 a Return Period Ends Regulatory Assets (a) AROs - coal ash (c) $ 9 $ 8 X (b) AROs - nuclear and other (c) 296 294 X (b) Accrued pension and OPEB (c) 476 458 X (h) Retired generation facilities (c) 216 257 X (b) Net regulatory asset related to income taxes (c) — 224 X (d) Storm cost deferrals (c) 376 — (f) 2021 Nuclear asset securitized balance, net 1,142 1,193 2036 Hedge costs deferrals 30 25 2018 DSM/EE (c) 17 15 X 2018 Deferred fuel and purchased power (c) 219 87 (g) 2019 Nuclear deferral — 96 AMI (c) 75 — X 2032 Other 36 36 (b) Total regulatory assets 2,892 2,693 Less: current portion 389 213 Total noncurrent regulatory assets $ 2,503 $ 2,480 Regulatory Liabilities (a) Costs of removal (c) $ 415 $ 358 (e) (b) Net regulatory liability related to income taxes (c) 948 — (b) Storm reserve (c) — 60 Deferred fuel and purchased power (c) — 17 (g) Other 18 44 (b) Total regulatory liabilities 1,381 479 Less: current portion 74 31 Total noncurrent regulatory liabilities $ 1,307 $ 448 (a) Regulatory assets and liabilities are excluded from rate base unless otherwise noted. (b) The expected recovery or refund period varies or has not been determined. (c) Included in rate base. (d) Recovery over the life of the associated assets. (e) Certain costs earn a return. (f) Earns a debt return/interest once collections begin. (g) Earns commercial paper rate. (h) Recovered primarily over the average remaining service periods or life expectancies of employees covered by the benefit plans. See Note 21 for additional detail.
Duke Energy Ohio [Member]
Public Utilities, General Disclosures [Line Items]
Schedule of Regulatory Assets	The following tables present the regulatory assets and liabilities recorded on Duke Energy Ohio's Consolidated Balance Sheets. December 31, Earns/Pays Recovery/Refund (in millions) 2017 2016 a Return Period Ends Regulatory Assets (a) AROs - coal ash $ 17 $ 12 X (b) Accrued pension and OPEB 139 135 (g) Net regulatory asset related to income taxes (c) — 63 (d) Storm cost deferrals 5 5 (b) Hedge costs deferrals 6 7 (b) DSM/EE 18 6 (f) (e) Grid modernization 39 65 X (e) Vacation accrual 5 4 2018 Deferred fuel and purchased power — 5 PISCC and deferred operating expenses (c) 19 20 X 2083 Transmission expansion obligation 50 71 (e) MGP 91 99 (b) AMI 6 — (b) East Bend deferrals 45 32 X (b) Deferred pipeline integrity costs 12 7 X (b) Other 42 26 (b) Total regulatory assets 494 557 Less: current portion 49 37 Total noncurrent regulatory assets $ 445 $ 520 Regulatory Liabilities (a) Costs of removal $ 189 $ 212 (d) Net regulatory liability related to income taxes 688 — (b) Accrued pension and OPEB 16 19 (g) Deferred fuel and purchased power — 6 Other 34 20 (b) Total regulatory liabilities 927 257 Less: current portion 36 21 Total noncurrent regulatory liabilities $ 891 $ 236 (a) Regulatory assets and liabilities are excluded from rate base unless otherwise noted. (b) The expected recovery or refund period varies or has not been determined. (c) Included in rate base. (d) Recovery over the life of the associated assets. (e) Recovered via a rider mechanism. (f) Includes incentives on DSM/EE investments. (g) Recovered primarily over the average remaining service periods or life expectancies of employees covered by the benefit plans. See Note 21 for additional detail.
Schedule Of Regulatory Liabilities	The following tables present the regulatory assets and liabilities recorded on Duke Energy Ohio's Consolidated Balance Sheets. December 31, Earns/Pays Recovery/Refund (in millions) 2017 2016 a Return Period Ends Regulatory Assets (a) AROs - coal ash $ 17 $ 12 X (b) Accrued pension and OPEB 139 135 (g) Net regulatory asset related to income taxes (c) — 63 (d) Storm cost deferrals 5 5 (b) Hedge costs deferrals 6 7 (b) DSM/EE 18 6 (f) (e) Grid modernization 39 65 X (e) Vacation accrual 5 4 2018 Deferred fuel and purchased power — 5 PISCC and deferred operating expenses (c) 19 20 X 2083 Transmission expansion obligation 50 71 (e) MGP 91 99 (b) AMI 6 — (b) East Bend deferrals 45 32 X (b) Deferred pipeline integrity costs 12 7 X (b) Other 42 26 (b) Total regulatory assets 494 557 Less: current portion 49 37 Total noncurrent regulatory assets $ 445 $ 520 Regulatory Liabilities (a) Costs of removal $ 189 $ 212 (d) Net regulatory liability related to income taxes 688 — (b) Accrued pension and OPEB 16 19 (g) Deferred fuel and purchased power — 6 Other 34 20 (b) Total regulatory liabilities 927 257 Less: current portion 36 21 Total noncurrent regulatory liabilities $ 891 $ 236 (a) Regulatory assets and liabilities are excluded from rate base unless otherwise noted. (b) The expected recovery or refund period varies or has not been determined. (c) Included in rate base. (d) Recovery over the life of the associated assets. (e) Recovered via a rider mechanism. (f) Includes incentives on DSM/EE investments. (g) Recovered primarily over the average remaining service periods or life expectancies of employees covered by the benefit plans. See Note 21 for additional detail.
Schedule of MISO Exit Fee Obligations	The following table provides a reconciliation of the beginning and ending balance of Duke Energy Ohio’s recorded liability for its exit obligation and share of MTEP costs, excluding MVP, recorded within Other in Current liabilities and Other in Other Noncurrent Liabilities on the Consolidated Balance Sheets. The retail portions of MTEP costs billed by MISO are recovered by Duke Energy Ohio through a non-bypassable rider. As of December 31, 2017 , and 2016 , $50 million and $71 million are recorded in Regulatory assets on Duke Energy Ohio's Consolidated Balance Sheets, respectively. Provisions/ Cash (in millions) December 31, 2016 Adjustments Reductions December 31, 2017 Duke Energy Ohio $ 90 $ (20 ) $ (4 ) $ 66
Duke Energy Indiana [Member]
Public Utilities, General Disclosures [Line Items]
Schedule of Regulatory Assets	The following tables present the regulatory assets and liabilities recorded on Duke Energy Indiana's Consolidated Balance Sheets. December 31, Earns/Pays Recovery/Refund (in millions) 2017 2016 a Return Period Ends Regulatory Assets (a) AROs - coal ash $ 380 $ 276 (b) Accrued pension and OPEB 197 222 (g) Retired generation facilities (c) 65 73 X 2025 Net regulatory asset related to income taxes — 119 (d) Hedge costs deferrals 25 26 (b) DSM/EE 21 — (e) (e) Vacation accrual 11 10 2018 Deferred fuel and purchased power 18 40 2018 PISCC and deferred operating expenses (c) 274 281 X (b) Gasification services agreement buyout (f) — 8 AMI (c) 21 46 X (b) Other 131 121 (b) Total regulatory assets 1,143 1,222 Less: current portion 165 149 Total noncurrent regulatory assets $ 978 $ 1,073 Regulatory Liabilities (a) Costs of removal $ 644 $ 660 (d) Net regulatory liability related to income taxes 998 — (b) Amounts to be refunded to customers 10 45 2018 Accrued pension and OPEB 64 72 (g) Other 31 11 (b) Total regulatory liabilities 1,747 788 Less: current portion 24 40 Total noncurrent regulatory liabilities $ 1,723 $ 748 (a) Regulatory assets and liabilities are excluded from rate base unless otherwise noted. (b) The expected recovery or refund period varies or has not been determined. (c) Included in rate base. (d) Recovery over the life of the associated assets. (e) Includes incentives on DSM/EE investments and is recovered through a tracker mechanism over a two-year period. (f) The IURC authorized Duke Energy Indiana to recover costs incurred to buy out a gasification services agreement, including carrying costs through 2017. (g) Recovered primarily over the average remaining service periods or life expectancies of employees covered by the benefit plans. See Note 21 for additional detail.
Schedule Of Regulatory Liabilities	The following tables present the regulatory assets and liabilities recorded on Duke Energy Indiana's Consolidated Balance Sheets. December 31, Earns/Pays Recovery/Refund (in millions) 2017 2016 a Return Period Ends Regulatory Assets (a) AROs - coal ash $ 380 $ 276 (b) Accrued pension and OPEB 197 222 (g) Retired generation facilities (c) 65 73 X 2025 Net regulatory asset related to income taxes — 119 (d) Hedge costs deferrals 25 26 (b) DSM/EE 21 — (e) (e) Vacation accrual 11 10 2018 Deferred fuel and purchased power 18 40 2018 PISCC and deferred operating expenses (c) 274 281 X (b) Gasification services agreement buyout (f) — 8 AMI (c) 21 46 X (b) Other 131 121 (b) Total regulatory assets 1,143 1,222 Less: current portion 165 149 Total noncurrent regulatory assets $ 978 $ 1,073 Regulatory Liabilities (a) Costs of removal $ 644 $ 660 (d) Net regulatory liability related to income taxes 998 — (b) Amounts to be refunded to customers 10 45 2018 Accrued pension and OPEB 64 72 (g) Other 31 11 (b) Total regulatory liabilities 1,747 788 Less: current portion 24 40 Total noncurrent regulatory liabilities $ 1,723 $ 748 (a) Regulatory assets and liabilities are excluded from rate base unless otherwise noted. (b) The expected recovery or refund period varies or has not been determined. (c) Included in rate base. (d) Recovery over the life of the associated assets. (e) Includes incentives on DSM/EE investments and is recovered through a tracker mechanism over a two-year period. (f) The IURC authorized Duke Energy Indiana to recover costs incurred to buy out a gasification services agreement, including carrying costs through 2017. (g) Recovered primarily over the average remaining service periods or life expectancies of employees covered by the benefit plans. See Note 21 for additional detail.
Piedmont Natural Gas [Member]
Public Utilities, General Disclosures [Line Items]
Schedule of Regulatory Assets	The following tables present the regulatory assets and liabilities recorded on Piedmont's Consolidated Balance Sheets. December 31, Earns/Pays Recovery/Refund (in millions) 2017 2016 a Return Period Ends Regulatory Assets (a) AROs - other $ 15 $ 14 (d) Accrued pension and OPEB (c) 91 166 (f) Derivatives - gas supply contracts 142 187 (e) Vacation accrual (c) 10 13 2018 Deferred pipeline integrity costs (c) 42 36 2018 Amount due from customers 64 66 X (b) Other 14 15 (b) Total regulatory assets 378 497 Less: current portion 95 124 Total noncurrent regulatory assets $ 283 $ 373 Regulatory Liabilities (a) Costs of removal $ 544 $ 528 (d) Net regulatory liability related to income taxes 597 80 (b) Other 3 — (b) Total regulatory liabilities 1,144 608 Less: current portion 3 — Total noncurrent regulatory liabilities $ 1,141 $ 608 (a) Regulatory assets and liabilities are excluded from rate base unless otherwise noted. (b) The expected recovery or refund period varies or has not been determined. (c) Included in rate base. (d) Recovery over the life of the associated assets. (e) Balance will fluctuate with changes in the market. Current contracts extend into 2031. (f) Recovered primarily over the average remaining service periods or life expectancies of employees covered by the benefit plans. See Note 21 for additional detail.
Schedule Of Regulatory Liabilities	The following tables present the regulatory assets and liabilities recorded on Piedmont's Consolidated Balance Sheets. December 31, Earns/Pays Recovery/Refund (in millions) 2017 2016 a Return Period Ends Regulatory Assets (a) AROs - other $ 15 $ 14 (d) Accrued pension and OPEB (c) 91 166 (f) Derivatives - gas supply contracts 142 187 (e) Vacation accrual (c) 10 13 2018 Deferred pipeline integrity costs (c) 42 36 2018 Amount due from customers 64 66 X (b) Other 14 15 (b) Total regulatory assets 378 497 Less: current portion 95 124 Total noncurrent regulatory assets $ 283 $ 373 Regulatory Liabilities (a) Costs of removal $ 544 $ 528 (d) Net regulatory liability related to income taxes 597 80 (b) Other 3 — (b) Total regulatory liabilities 1,144 608 Less: current portion 3 — Total noncurrent regulatory liabilities $ 1,141 $ 608 (a) Regulatory assets and liabilities are excluded from rate base unless otherwise noted. (b) The expected recovery or refund period varies or has not been determined. (c) Included in rate base. (d) Recovery over the life of the associated assets. (e) Balance will fluctuate with changes in the market. Current contracts extend into 2031. (f) Recovered primarily over the average remaining service periods or life expectancies of employees covered by the benefit plans. See Note 21 for additional detail.

Commitments and Contingencies (

Commitments and Contingencies (Table)	12 Months Ended
	Dec. 31, 2017
Valuation and Qualifying Accounts Disclosure [Line Items]
Schedule of Additional Possible Losses in Excess of Recorded Environmental Reserves	Additional losses in excess of recorded reserves that could be incurred for the stages of investigation, remediation and monitoring for environmental sites that have been evaluated at this time are not material except as presented in the table below. (in millions) Duke Energy $ 56 Duke Energy Carolinas 19 Duke Energy Ohio 30 Piedmont 2
Schedule of Legal Reserves	The table below presents recorded reserves based on management’s best estimate of probable loss for legal matters, excluding asbestos-related reserves and the exit obligation discussed above related to the termination of an EPC contract. Reserves are classified on the Consolidated Balance Sheets in Other within Other Noncurrent Liabilities and Accounts payable and Other within Current Liabilities. The reasonably possible range of loss in excess of recorded reserves is not material, other than as described above. December 31, (in millions) 2017 2016 Reserves for Legal Matters Duke Energy $ 88 $ 98 Duke Energy Carolinas 30 23 Progress Energy 55 59 Duke Energy Progress 13 14 Duke Energy Florida 24 28 Duke Energy Ohio — 4 Piedmont 2 2
Schedule of Purchase Power Obligations	The following table presents executory purchased power contracts with terms exceeding one year, excluding contracts classified as leases. Amounts at Duke Energy Ohio were immaterial. Minimum Purchase Amount at December 31, 2017 Contract (in millions) Expiration 2018 2019 2020 2021 2022 Thereafter Total Duke Energy Progress (a) 2019-2031 $ 68 $ 68 $ 51 $ 52 $ 30 $ 239 $ 508 Duke Energy Florida (b) 2021-2043 357 374 394 378 376 770 2,649 (a) Contracts represent between 15 percent and 100 percent of net plant output. (b) Contracts represent between 81 percent and 100 percent of net plant output.
Schedule of Natural Gas Supply Contract Commitments [Table Text Block]	The following table presents future unconditional purchase obligations under natural gas supply and capacity contracts as of December 31, 2017. (in millions) Duke Energy Duke Energy Ohio Piedmont 2018 $ 314 $ 37 $ 277 2019 280 28 252 2020 252 25 227 2021 249 26 223 2022 226 11 215 Thereafter 1,121 3 1,118 Total $ 2,442 $ 130 $ 2,312
Schedule of Operating Lease Rent Expense	The following tables present rental expense for operating leases. These amounts are included in Operation, maintenance and other on the Consolidated Statements of Operations. Years Ended December 31, (in millions) 2017 2016 2015 Duke Energy $ 241 $ 242 $ 313 Duke Energy Carolinas 44 45 41 Progress Energy 130 140 230 Duke Energy Progress 75 68 149 Duke Energy Florida 55 72 81 Duke Energy Ohio 15 16 13 Duke Energy Indiana 23 23 20 Year Ended Two Months Ended Years Ended October 31, (in millions) December 31, 2017 December 31, 2016 2016 2015 Piedmont $ 7 $ 1 $ 5 $ 5
Schedule of Future Minimum Rental Payments for Operating Leases	The following table presents future minimum lease payments under operating leases, which at inception had a non-cancelable term of more than one year. December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont 2018 $ 233 $ 36 $ 133 $ 77 $ 56 $ 20 $ 22 $ 6 2019 203 29 126 72 54 12 14 5 2020 183 25 117 62 55 10 10 5 2021 150 19 97 48 49 7 8 6 2022 135 16 90 42 48 4 5 6 Thereafter 882 52 525 344 181 5 7 16 Total $ 1,786 $ 177 $ 1,088 $ 645 $ 443 $ 58 $ 66 $ 44
Schedule of Future Minimum Lease Payments for Capital Leases	The following table presents future minimum lease payments under capital leases. December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana 2018 $ 168 $ 13 $ 46 $ 21 $ 25 $ 3 $ 2 2019 169 13 45 20 25 1 1 2020 174 13 47 21 26 — 1 2021 176 8 45 22 25 — 1 2022 169 8 45 21 24 — 1 Thereafter 745 109 323 227 95 — 38 Minimum annual payments 1,601 164 551 332 220 4 44 Less: amount representing interest (601 ) (103 ) (283 ) (192 ) (91 ) — (33 ) Total $ 1,000 $ 61 $ 268 $ 140 $ 129 $ 4 $ 11
Reserve for Environmental Costs [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Schedule of Legal Reserves	The following tables contain information regarding reserves for probable and estimable costs related to the various environmental sites. These reserves are recorded in Accounts payable within Current Liabilities and Other within Other Noncurrent Liabilities on the Consolidated Balance Sheets. Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Balance at December 31, 2014 $ 92 $ 10 $ 17 $ 5 $ 12 $ 54 $ 10 Provisions/adjustments 11 1 4 — 4 1 5 Cash reductions (9 ) (1 ) (4 ) (2 ) (2 ) (1 ) (3 ) Balance at December 31, 2015 94 10 17 3 14 54 12 Provisions/adjustments 19 4 7 2 4 7 1 Cash reductions (15 ) (4 ) (6 ) (2 ) (4 ) (2 ) (3 ) Balance at December 31, 2016 98 10 18 3 14 59 10 Provisions/adjustments 8 3 3 2 2 3 (4 ) Cash reductions (25 ) (3 ) (6 ) (2 ) (4 ) (15 ) (1 ) Balance at December 31, 2017 $ 81 $ 10 $ 15 $ 3 $ 12 $ 47 $ 5 As of December 31, 2016, October 31, 2016, 2015 and 2014, Piedmont's environmental reserve was $1 million . In 2017, a $1 million provision was recorded, resulting in a reserve balance of $2 million at December 31, 2017.

Debt and Credit Facilities (Tab

Debt and Credit Facilities (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Schedule of Debt	The following table shows the significant components of Current maturities of Long-Term Debt on the Consolidated Balance Sheets. The Duke Energy Registrants currently anticipate satisfying these obligations with cash on hand and proceeds from additional borrowings. (in millions) Maturity Date Interest Rate December 31, 2017 Unsecured Debt Duke Energy (Parent) June 2018 6.250 % $ 250 Duke Energy (Parent) June 2018 2.100 % 500 Piedmont December 2018 2.286 % (b) 250 First Mortgage Bonds Duke Energy Carolinas January 2018 5.250 % 400 Duke Energy Carolinas April 2018 5.100 % 300 Duke Energy Florida June 2018 5.650 % 500 Duke Energy Carolinas November 2018 7.000 % 500 Other (a) 544 Current maturities of long-term debt $ 3,244 (a) Includes capital lease obligations, amortizing debt and small bullet maturities. (b) Debt has a floating interest rate. The following tables summarize outstanding debt. December 31, 2017 Weighted Average Duke Duke Duke Duke Duke Interest Duke Energy Progress Energy Energy Energy Energy (in millions) Rate Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Unsecured debt, maturing 2018-2073 4.17 % $ 20,409 $ 1,150 $ 3,950 $ — $ 550 $ 900 $ 411 $ 2,050 Secured debt, maturing 2018-2037 3.15 % 4,458 450 1,757 300 1,457 — — — First mortgage bonds, maturing 2018-2047 (a) 4.51 % 23,529 7,959 11,801 6,776 5,025 1,100 2,669 — Capital leases, maturing 2018-2051 (b) 4.55 % 1,000 61 269 139 129 5 11 — Tax-exempt bonds, maturing 2019-2041 (c) 3.23 % 941 243 48 48 — 77 572 — Notes payable and commercial paper (d) 1.57 % 2,788 — — — — — — — Money pool/intercompany borrowings — 404 955 390 — 54 311 364 Fair value hedge carrying value adjustment 6 6 — — — — — — Unamortized debt discount and premium, net (e) 1,582 (19 ) (30 ) (16 ) (10 ) (33 ) (9 ) (1 ) Unamortized debt issuance costs (f) (271 ) (47 ) (108 ) (40 ) (56 ) (7 ) (21 ) (12 ) Total debt 4.09 % $ 54,442 $ 10,207 $ 18,642 $ 7,597 $ 7,095 $ 2,096 $ 3,944 $ 2,401 Short-term notes payable and commercial paper (2,163 ) — — — — — — — Short-term money pool/intercompany borrowings — (104 ) (805 ) (240 ) — (29 ) (161 ) (364 ) Current maturities of long-term debt (g) (3,244 ) (1,205 ) (771 ) (3 ) (768 ) (3 ) (3 ) (250 ) Total long-term debt (g) $ 49,035 $ 8,898 $ 17,066 $ 7,354 $ 6,327 $ 2,064 $ 3,780 $ 1,787 (a) Substantially all electric utility property is mortgaged under mortgage bond indentures. (b) Duke Energy includes $81 million and $603 million of capital lease purchase accounting adjustments related to Duke Energy Progress and Duke Energy Florida, respectively, related to power purchase agreements that are not accounted for as capital leases in their respective financial statements because of grandfathering provisions in GAAP. (c) Substantially all tax-exempt bonds are secured by first mortgage bonds or letters of credit. (d) Includes $625 million that was classified as Long-Term Debt on the Consolidated Balance Sheets due to the existence of long-term credit facilities that backstop these commercial paper balances, along with Duke Energy’s ability and intent to refinance these balances on a long-term basis. The weighted average days to maturity for Duke Energy's commercial paper program was 14 days. (e) Duke Energy includes $1,509 million and $176 million in purchase accounting adjustments related to Progress Energy and Piedmont, respectively. (f) Duke Energy includes $47 million in purchase accounting adjustments primarily related to the merger with Progress Energy. (g) Refer to Note 17 for additional information on amounts from consolidated VIEs. December 31, 2016 Weighted Average Duke Duke Duke Duke Duke Interest Duke Energy Progress Energy Energy Energy Energy (in millions) Rate Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Unsecured debt, maturing 2017-2073 4.30 % $ 17,812 $ 1,150 $ 3,551 $ — $ 150 $ 810 $ 415 $ 1,835 Secured debt, maturing 2017-2037 2.60 % 3,909 425 1,819 300 1,519 — — — First mortgage bonds, maturing 2017-2046 (a) 4.61 % 21,879 7,410 10,800 6,425 4,375 1,000 2,669 — Capital leases, maturing 2018-2051 (b) 4.48 % 1,100 22 285 142 143 7 11 — Tax-exempt bonds, maturing 2017-2041 (c) 2.84 % 1,053 355 48 48 — 77 572 — Notes payable and commercial paper (d) 1.01 % 3,112 — — — — — — — Money pool/intercompany borrowings (e) — 300 1,902 150 297 41 150 — Fair value hedge carrying value adjustment 6 6 — — — — — — Unamortized debt discount and premium, net (f) 1,753 (20 ) (31 ) (16 ) (10 ) (28 ) (9 ) (1 ) Unamortized debt issuance costs (g) (242 ) (45 ) (104 ) (38 ) (52 ) (7 ) (22 ) (13 ) Total debt 4.07 % $ 50,382 $ 9,603 $ 18,270 $ 7,011 $ 6,422 $ 1,900 $ 3,786 $ 1,821 Short-term notes payable and commercial paper (2,487 ) — — — — — — — Short-term money pool/intercompany borrowings — — (729 ) — (297 ) (16 ) — — Current maturities of long-term debt (h) (2,319 ) (116 ) (778 ) (452 ) (326 ) (1 ) (3 ) (35 ) Total long-term debt (h) $ 45,576 $ 9,487 $ 16,763 $ 6,559 $ 5,799 $ 1,883 $ 3,783 $ 1,786 (a) Substantially all electric utility property is mortgaged under mortgage bond indentures. (b) Duke Energy includes $98 million and $670 million of capital lease purchase accounting adjustments related to Duke Energy Progress and Duke Energy Florida, respectively, related to power purchase agreements that are not accounted for as capital leases in their respective financial statements because of grandfathering provisions in GAAP. (c) Substantially all tax-exempt bonds are secured by first mortgage bonds or letters of credit. (d) Includes $625 million that was classified as Long-Term Debt on the Consolidated Balance Sheets due to the existence of long-term credit facilities that backstop these commercial paper balances, along with Duke Energy’s ability and intent to refinance these balances on a long-term basis. The weighted average days to maturity for Duke Energy and Piedmont's commercial paper programs were 14 days and eight days, respectively. (e) Progress Energy amount includes a $1 billion intercompany loan related to the sale of the International Disposal Group. See Note 2 for further discussion of the sale. (f) Duke Energy includes $1,653 million and $197 million purchase accounting adjustments related to the mergers with Progress Energy and Piedmont, respectively. (g) Duke Energy includes $53 million in purchase accounting adjustments primarily related to the merger with Progress Energy. (h) Refer to Note 17 for additional information on amounts from consolidated VIEs. The following tables show short-term obligations classified as long-term debt. December 31, 2017 Duke Duke Duke Duke Duke Energy Energy Energy Energy (in millions) Energy Carolinas Progress Ohio Indiana Tax-exempt bonds $ 312 $ — $ — $ 27 $ 285 Commercial paper (a) 625 300 150 25 150 Total $ 937 $ 300 $ 150 $ 52 $ 435 December 31, 2016 Duke Duke Duke Duke Duke Energy Energy Energy Energy (in millions) Energy Carolinas Progress Ohio Indiana Tax-exempt bonds $ 347 $ 35 $ — $ 27 $ 285 Commercial paper (a) 625 300 150 25 150 Total $ 972 $ 335 $ 150 $ 52 $ 435 (a) Progress Energy amounts are equal to Duke Energy Progress amounts.
Schedule of Maturities of Long-term Debt	The following table shows the annual maturities of long-term debt for the next five years and thereafter. Amounts presented exclude short-term notes payable and commercial paper and money pool borrowings for the Subsidiary Registrants. December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy (a) Carolinas Energy Progress Florida Ohio Indiana Piedmont 2018 $ 3,244 $ 1,205 $ 771 $ 3 $ 768 $ 3 $ 3 $ 250 2019 3,563 6 2,191 903 490 548 61 — 2020 3,699 906 871 304 568 — 502 — 2021 3,760 502 1,472 602 371 48 69 159 2022 3,010 302 1,176 653 74 23 243 — Thereafter 33,271 7,182 11,356 4,892 4,824 1,445 2,905 1,628 Total long-term debt, including current maturities $ 50,547 $ 10,103 $ 17,837 $ 7,357 $ 7,095 $ 2,067 $ 3,783 $ 2,037 (a) Excludes $1,732 million in purchase accounting adjustments related to the Progress Energy merger and the Piedmont acquisition.
Schedule of Long-term Debt Instruments	The following tables summarize significant debt issuances (in millions). Year Ended December 31, 2017 Duke Duke Duke Duke Duke Maturity Interest Duke Energy Energy Energy Energy Energy Issuance Date Date Rate Energy (Parent) Carolinas Progress Florida Ohio Unsecured Debt April 2017 (a) April 2025 3.364 % $ 420 $ 420 $ — $ — $ — $ — June 2017 (b) June 2020 2.100 % 330 330 — — — — August 2017 (c) August 2022 2.400 % 500 500 — — — — August 2017 (c) August 2027 3.150 % 750 750 — — — — August 2017 (c) August 2047 3.950 % 500 500 — — — — December 2017 (d) December 2019 (k) 2.100 % 400 — — — 400 — Secured Debt February 2017 (e) June 2034 4.120 % 587 — — — — — August 2017 (f) December 2036 4.110 % 233 — — — — — First Mortgage Bonds January 2017 (g) January 2020 1.850 % 250 — — — 250 — January 2017 (g) January 2027 3.200 % 650 — — — 650 — March 2017 (h) June 2046 3.700 % 100 — — — — 100 September 2017 (i) September 2020 1.500 % (l) 300 — — 300 — — September 2017 (i) September 2047 3.600 % 500 — — 500 — — November 2017 (j) December 2047 3.700 % 550 — 550 — — — Total issuances $ 6,070 $ 2,500 $ 550 $ 800 $ 1,300 $ 100 (a) Proceeds were used to refinance $400 million of unsecured debt at maturity and to repay a portion of outstanding commercial paper. (b) Debt issued to repay a portion of outstanding commercial paper. (c) Debt issued to repay at maturity $700 million of unsecured debt, to repay outstanding commercial paper and for general corporate purposes. (d) Debt issued to fund storm restoration costs related to Hurricane Irma and for general corporate purposes. (e) Portfolio financing of four Texas and Oklahoma wind facilities. Duke Energy pledged substantially all of the assets of these wind facilities and is nonrecourse to Duke Energy. Proceeds were used to reimburse Duke Energy for a portion of previously funded construction expenditures. (f) Portfolio financing of eight solar facilities located in California, Colorado and New Mexico. Duke Energy pledged substantially all of the assets of these solar facilities and is nonrecourse to Duke Energy. Proceeds were used to reimburse Duke Energy for a portion of previously funded construction expenditures. (g) Debt issued to fund capital expenditures for ongoing construction and capital maintenance, to repay a $250 million aggregate principal amount of bonds at maturity and for general corporate purposes. (h) Proceeds were used to fund capital expenditures for ongoing construction, capital maintenance and for general corporate purposes. (i) Debt issued to repay at maturity a $200 million aggregate principal amount of bonds at maturity, pay down intercompany short-term debt and for general corporate purposes, including capital expenditures. (j) Debt issued to refinance $400 million aggregate principal amount of bonds due January 2018, pay down intercompany short-term debt and for general corporate purposes. (k) Principal balance will be repaid in equal quarterly installments beginning in March 2018. (l) Debt issuance has a floating interest rate. Year Ended December 31, 2016 Duke Duke Duke Duke Duke Duke Maturity Interest Duke Energy Energy Energy Energy Energy Energy Issuance Date Date Rate Energy (Parent) Carolinas Progress Florida Ohio Indiana Unsecured Debt April 2016 (a) April 2023 2.875 % $ 350 $ 350 $ — $ — $ — $ — $ — August 2016 (b) September 2021 1.800 % 750 750 — — — — — August 2016 (b) September 2026 2.650 % 1,500 1,500 — — — — — August 2016 (b) September 2046 3.750 % 1,500 1,500 — — — — — Secured Debt June 2016 (c) March 2020 1.196 % 183 — — — 183 — — June 2016 (c) September 2022 1.731 % 150 — — — 150 — — June 2016 (c) September 2029 2.538 % 436 — — — 436 — — June 2016 (c) March 2033 2.858 % 250 — — — 250 — — June 2016 (c) September 2036 3.112 % 275 — — — 275 — — August 2016 (d) June 2034 2.747 % (i) 228 — — — — — — August 2016 (d) June 2020 2.747 % (i) 105 — — — — — — First Mortgage Bonds March 2016 (e) March 2023 2.500 % 500 — 500 — — — — March 2016 (e) March 2046 3.875 % 500 — 500 — — — — May 2016 (f) May 2046 3.750 % 500 — — — — — 500 June 2016 (e) June 2046 3.700 % 250 — — — — 250 — September 2016 (g) October 2046 3.400 % 600 — — — 600 — — September 2016 (e) October 2046 3.700 % 450 — — 450 — — — November 2016 (h) December 2046 2.950 % 600 — 600 — — — — Total issuances $ 9,127 $ 4,100 $ 1,600 $ 450 $ 1,894 $ 250 $ 500 (a) Proceeds were used to pay down outstanding commercial paper and for general corporate purposes. (b) Proceeds were used to finance a portion of the Piedmont acquisition. The $4.9 billion Bridge Facility was terminated following the issuance of this debt. See Note 2 for additional information on the Piedmont acquisition. (c) DEFPF issued nuclear-asset recovery bonds and used the proceeds to acquire nuclear-asset recovery property from its parent, Duke Energy Florida. The nuclear-asset recovery bonds are payable only from and secured by the nuclear asset-recovery property. DEFPF is consolidated for financial reporting purposes; however, the nuclear asset-recovery bonds do not constitute a debt, liability or other legal obligation of, or interest in, Duke Energy Florida or any of its affiliates other than DEFPF. The assets of DEFPF, including the nuclear-asset recovery property, are not available to pay creditors of Duke Energy Florida or any of its affiliates. Duke Energy Florida used the proceeds from the sale to repay short-term borrowings under the intercompany money pool borrowing arrangement and make an equity distribution of $649 million to the ultimate parent, Duke Energy (Parent), which repaid short-term borrowings. The nuclear-asset recovery bonds are sequential pay amortizing bonds. The maturity date above represents the scheduled final maturity date for the bonds. See Notes 4 and 17 for additional information. (d) Emerald State Solar, LLC, an indirect wholly owned subsidiary of Duke Energy entered into portfolio financing of approximately 22 North Carolina solar facilities. Tranche A of $228 million is secured by substantially all of the assets of the solar facilities and is nonrecourse to Duke Energy. Tranche B of $105 million is secured by an Equity Contribution Agreement with Duke Energy. Proceeds were used to reimburse Duke Energy for a portion of previously funded construction expenditures related to the Emerald State Solar, LLC portfolio. The initial interest rate on the loans was six months London Interbank Offered Rate (LIBOR) plus an applicable margin of 1.75 percent plus a 0.125 percent increase every three years thereafter. In connection with this debt issuance, Emerald State Solar, LLC entered into two interest rate swaps to convert the substantial majority of the loan interest payments from variable rates to fixed rates of approximately 1.81 percent for Tranche A and 1.38 percent for Tranche B, plus the applicable margin. See Note 14 for further information on the notional amounts of the interest rate swaps. (e) Proceeds were used to fund capital expenditures for ongoing construction, capital maintenance and for general corporate purposes. (f) Proceeds were used to repay $325 million of unsecured debt due June 2016, $150 million of first mortgage bonds due July 2016 and for general corporate purposes. (g) Proceeds were used to fund capital expenditures for ongoing construction, capital maintenance, to repay short-term borrowings under the intercompany money pool borrowing arrangement and for general corporate purposes. (h) Proceeds were used to repay at maturity $350 million aggregate principal amount of certain bonds due December 2016, as well as to fund capital expenditures for ongoing construction and capital maintenance and for general corporate purposes. (i) Debt issuance has a floating interest rate.
Schedule Of Line Of Credit Facilities	December 31, 2017 Duke Duke Duke Duke Duke Duke Duke Energy Energy Energy Energy Energy Energy (in millions) Energy (Parent) Carolinas Progress Florida Ohio Indiana Piedmont Facility size (a) $ 8,000 $ 2,850 $ 1,350 $ 1,250 $ 800 $ 450 $ 600 $ 700 Reduction to backstop issuances Commercial paper (b) (1,799 ) (561 ) (371 ) (314 ) — (45 ) (260 ) (248 ) Outstanding letters of credit (63 ) (54 ) (4 ) (2 ) (1 ) — — (2 ) Tax-exempt bonds (81 ) — — — — — (81 ) — Coal ash set-aside (500 ) — (250 ) (250 ) — — — — Available capacity $ 5,557 $ 2,235 $ 725 $ 684 $ 799 $ 405 $ 259 $ 450 (a) Represents the sublimit of each borrower. (b) Duke Energy issued $625 million of commercial paper and loaned the proceeds through the money pool to Duke Energy Carolinas, Duke Energy Progress, Duke Energy Ohio and Duke Energy Indiana. The balances are classified as Long-Term Debt Payable to Affiliated Companies in the Consolidated Balance Sheets.

Joint Ownership of Generating42

Joint Ownership of Generating and Transmission Facilities (Tables)	12 Months Ended
	Dec. 31, 2017
Jointly Owned Utility Plant Interests [Line Items]
Schedule Joint Ownership of Generating and Transmission Facilities	The following table presents the Duke Energy Registrants' interest of jointly owned plant or facilities and amounts included on the Consolidated Balance Sheets. All facilities are operated by the Duke Energy Registrants and are included in the Electric Utilities and Infrastructure segment. December 31, 2017 Construction Ownership Property, Plant Accumulated Work in (in millions except for ownership interest) Interest and Equipment Depreciation Progress Duke Energy Carolinas Catawba Nuclear Station (units 1 and 2) (a) 19.25 % $ 927 $ 651 $ 19 Lee Combined Combustion Station (b) 86.67 % — — 552 Duke Energy Ohio Transmission facilities (c) Various 89 63 1 Duke Energy Indiana Gibson Station (unit 5) (d) 50.05 % 348 162 9 Vermillion Generating Station (e) 62.5 % 155 120 — Transmission and local facilities (d) Various 4,672 1,739 — (a) Jointly owned with North Carolina Municipal Power Agency Number 1, NCEMC and Piedmont Municipal Power Agency. (b) Jointly owned with NCEMC. (c) Jointly owned with America Electric Power Generation Resources and The Dayton Power and Light Company. (d) Jointly owned with Wabash Valley Power Association, Inc. (WVPA) and Indiana Municipal Power Agency. (e) Jointly owned with WVPA.

Asset Retirement Obligations (T

Asset Retirement Obligations (Tables)	12 Months Ended
	Dec. 31, 2017
Asset Retirement Obligations [Line Items]
Schedule of Asset Retirement Obligations by Category	The following table presents the AROs recorded on the Consolidated Balance Sheets. December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Decommissioning of nuclear power facilities (a) $ 5,371 $ 1,944 $ 3,246 $ 2,564 $ 681 $ — $ — $ — Closure of ash impoundments 4,525 1,629 2,094 2,075 19 39 763 — Other (b) 279 37 74 34 42 45 18 15 Total asset retirement obligation $ 10,175 $ 3,610 $ 5,414 $ 4,673 $ 742 $ 84 $ 781 $ 15 Less: current portion 689 337 295 295 — 3 54 — Total noncurrent asset retirement obligation $ 9,486 $ 3,273 $ 5,119 $ 4,378 $ 742 $ 81 $ 727 $ 15 (a) Duke Energy amount includes purchase accounting adjustments related to the merger with Progress Energy. (b) Primarily includes obligations related to asbestos removal. Duke Energy Ohio and Piedmont also include AROs related to the retirement of natural gas mains and services. Duke Energy includes AROs related to the removal of renewable energy generation assets.
Public Utilities General Disclosures	The following table summarizes information about the most recent site-specific nuclear decommissioning cost studies. Decommissioning costs in the table below are stated in 2013 or 2014 dollars, depending on the year of the cost study, and include costs to decommission plant components not subject to radioactive contamination. Annual Funding Decommissioning (in millions) Requirement (a) Costs (a)(b) Year of Cost Study Duke Energy $ 14 $ 8,150 2013 and 2014 Duke Energy Carolinas — 3,420 2013 Duke Energy Progress 14 3,550 2014 Duke Energy Florida — 1,180 2013 (a) Amounts for Progress Energy equal the sum of Duke Energy Progress and Duke Energy Florida. (b) Amounts include the Subsidiary Registrant's ownership interest in jointly owned reactors. Other joint owners are responsible for decommissioning costs related to their interest in the reactors. The following table presents the fair value of NDTF assets legally restricted for purposes of settling AROs associated with nuclear decommissioning. Duke Energy Florida is actively decommissioning Crystal River Unit 3 and was granted an exemption from the NRC which allows for use of the NDTF for all aspects of nuclear decommissioning. The entire balance of Duke Energy Florida's NDTF may be applied toward license termination, spent fuel and site restoration costs incurred to decommission Crystal River Unit 3. See Note 16 for additional information related to the fair value of the Duke Energy Registrants' NDTFs. December 31, (in millions) 2017 2016 Duke Energy $ 5,864 $ 5,099 Duke Energy Carolinas 3,321 2,882 Duke Energy Progress 2,543 2,217 The following table includes the current expiration of nuclear operating licenses. Unit Year of Expiration Duke Energy Carolinas Catawba Units 1 and 2 2043 McGuire Unit 1 2041 McGuire Unit 2 2043 Oconee Units 1 and 2 2033 Oconee Unit 3 2034 Duke Energy Progress Brunswick Unit 1 2036 Brunswick Unit 2 2034 Harris 2046 Robinson 2030
Rollforward Schedule of Asset Retirement Obligations	The following tables present changes in the liability associated with AROs. Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Balance at December 31, 2015 $ 10,249 $ 3,918 $ 5,369 $ 4,567 $ 802 $ 125 $ 525 Acquisitions (a) 22 — 2 — 2 — — Accretion expense (b) 400 187 230 194 35 5 24 Liabilities settled (c) (613 ) (287 ) (272 ) (212 ) (60 ) (5 ) (49 ) Liabilities incurred in the current year 51 — 3 3 — — 29 Revisions in estimates of cash flows 502 77 143 145 (1 ) (48 ) 337 Balance at December 31, 2016 10,611 3,895 5,475 4,697 778 77 866 Accretion expense (b) 435 184 228 195 33 3 32 Liabilities settled (c) (619 ) (282 ) (270 ) (204 ) (65 ) (7 ) (49 ) Liabilities incurred in the current year (d) 51 5 — — — 7 29 Revisions in estimates of cash flows (303 ) (192 ) (19 ) (15 ) (4 ) 4 (97 ) Balance at December 31, 2017 $ 10,175 $ 3,610 $ 5,414 $ 4,673 $ 742 $ 84 $ 781 (a) Duke Energy amount relates to the Piedmont acquisition. See Note 2 for additional information. (b) Substantially all accretion expense for the years ended December 31, 2017 , and 2016 relates to Duke Energy’s regulated electric operations and has been deferred in accordance with regulatory accounting treatment. (c) Amounts primarily relate to ash impoundment closures and nuclear decommissioning of Crystal River Unit 3. (d) Amounts primarily relate to AROs recorded as a result of state agency closure requirements at Duke Energy Indiana.
Piedmont Natural Gas [Member]
Asset Retirement Obligations [Line Items]
Rollforward Schedule of Asset Retirement Obligations	(in millions) Piedmont Balance at October 31, 2015 $ 20 Accretion expense 1 Liabilities settled (7 ) Liabilities incurred in the current year 6 Revisions in estimates of cash flows (6 ) Balance at October 31, 2016 14 Liabilities settled (1 ) Liabilities incurred in the current year 1 Balance at December 31, 2016 14 Accretion expense 1 Liabilities settled (8 ) Liabilities incurred in the current year 8 Balance at December 31, 2017 $ 15

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2017
Public Utility, Property, Plant and Equipment [Line Items]
Schedule Of Property, Plant And Equipment	The composite weighted average depreciation rates, excluding nuclear fuel, are included in the table that follows. Years Ended December 31, 2017 2016 2015 Duke Energy 2.8 % 2.8 % 2.9 % Duke Energy Carolinas 2.8 % 2.8 % 2.8 % Progress Energy 2.6 % 2.7 % 2.6 % Duke Energy Progress 2.6 % 2.6 % 2.6 % Duke Energy Florida 2.8 % 2.8 % 2.7 % Duke Energy Ohio 2.8 % 2.6 % 2.7 % Duke Energy Indiana 3.0 % 3.1 % 3.0 % Piedmont (a) 2.3 % (a) Piedmont's weighted average depreciation rate was 2.4 percent , 2.4 percent , and 2.5 percent for the annualized two months ended December 31, 2016 and for the years ended October 31, 2016 and 2015, respectively. The following tables summarize the property, plant and equipment for Duke Energy and its subsidiary registrants. December 31, 2017 Estimated Useful Duke Duke Duke Duke Duke Life Duke Energy Progress Energy Energy Energy Energy (in millions) (Years) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Land $ 1,559 $ 467 $ 767 $ 424 $ 343 $ 134 $ 111 $ 41 Plant – Regulated Electric generation, distribution and transmission 8-100 93,687 35,657 39,419 24,502 14,917 4,870 13,741 — Natural gas transmission and distribution 12-80 8,292 — — — — 2,559 — 5,733 Other buildings and improvements 15-100 1,936 647 652 316 336 243 240 154 Plant – Nonregulated Electric generation, distribution and transmission (a) 5-30 4,273 — — — — — — — Other buildings and improvements 25-35 465 — — — — — — — Nuclear fuel 3,680 2,120 1,560 1,560 — — — — Equipment 3-55 2,122 402 555 416 139 348 169 266 Construction in process 6,995 2,614 3,059 1,434 1,625 350 416 231 Other 3-40 4,498 1,032 1,311 931 370 228 271 300 Total property, plant and equipment (b)(e) 127,507 42,939 47,323 29,583 17,730 8,732 14,948 6,725 Total accumulated depreciation – regulated (c)(d)(e) (39,742 ) (15,063 ) (15,857 ) (10,903 ) (4,947 ) (2,691 ) (4,662 ) (1,479 ) Total accumulated depreciation – nonregulated (d)(e) (1,795 ) — — — — — — — Generation facilities to be retired, net 421 — 421 421 — — — — Total net property, plant and equipment $ 86,391 $ 27,876 $ 31,887 $ 19,101 $ 12,783 $ 6,041 $ 10,286 $ 5,246 (a) Includes a pretax impairment charge of $58 million on a wholly owned non-contracted wind project. See discussion below. (b) Includes capitalized leases of $1,294 million , $81 million , $272 million , $139 million , $133 million , $80 million and $35 million at Duke Energy, Duke Energy Carolinas, Progress Energy, Duke Energy Progress, Duke Energy Florida, Duke Energy Ohio and Duke Energy Indiana, respectively, primarily within Plant – Regulated. The Progress Energy, Duke Energy Progress and Duke Energy Florida amounts are net of $114 million , $11 million and $103 million , respectively, of accumulated amortization of capitalized leases. (c) Includes $2,113 million , $1,283 million , $831 million and $831 million of accumulated amortization of nuclear fuel at Duke Energy, Duke Energy Carolinas, Progress Energy and Duke Energy Progress, respectively. (d) Includes accumulated amortization of capitalized leases of $57 million , $11 million , $21 million and $9 million at Duke Energy, Duke Energy Carolinas, Duke Energy Ohio and Duke Energy Indiana, respectively. (e) Includes gross property, plant and equipment cost of consolidated VIEs of $3,941 million and accumulated depreciation of consolidated VIEs of $598 million at Duke Energy. December 31, 2016 Estimated Useful Duke Duke Duke Duke Duke Life Duke Energy Progress Energy Energy Energy Energy (in millions) (Years) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Land $ 1,501 $ 432 $ 735 $ 393 $ 342 $ 150 $ 106 $ 39 Plant – Regulated Electric generation, distribution and transmission 8-100 89,864 34,515 37,596 23,683 13,913 4,593 13,160 — Natural gas transmission and distribution 12-67 7,738 — — — — 2,456 — 5,282 Other buildings and improvements 15-100 1,692 502 634 293 341 211 197 148 Plant – Nonregulated Electric generation, distribution and transmission 5-30 4,298 — — — — — — — Other buildings and improvements 25-35 421 — — — — — — — Nuclear fuel 3,572 2,092 1,480 1,480 — — — — Equipment 3-38 1,941 358 505 378 127 338 156 260 Construction in process 6,186 2,324 2,708 1,329 1,379 206 396 210 Other 5-40 4,184 904 1,206 863 332 172 226 235 Total property, plant and equipment (a)(d) 121,397 41,127 44,864 28,419 16,434 8,126 14,241 6,174 Total accumulated depreciation – regulated (b)(c)(d) (37,831 ) (14,365 ) (15,212 ) (10,561 ) (4,644 ) (2,579 ) (4,317 ) (1,360 ) Total accumulated depreciation – nonregulated (c)(d) (1,575 ) — — — — — — — Generation facilities to be retired, net 529 — 529 529 — — — — Total net property, plant and equipment $ 82,520 $ 26,762 $ 30,181 $ 18,387 $ 11,790 $ 5,547 $ 9,924 $ 4,814 (a) Includes capitalized leases of $1,355 million , $40 million , $288 million , $142 million , $146 million , $81 million and $35 million at Duke Energy, Duke Energy Carolinas, Progress Energy, Duke Energy Progress, Duke Energy Florida, Duke Energy Ohio and Duke Energy Indiana, respectively, primarily within Plant – Regulated. The Progress Energy, Duke Energy Progress and Duke Energy Florida amounts are net of $99 million , $9 million and $90 million , respectively, of accumulated amortization of capitalized leases. (b) Includes $1,922 million , $1,192 million , $730 million and $730 million of accumulated amortization of nuclear fuel at Duke Energy, Duke Energy Carolinas, Progress Energy and Duke Energy Progress, respectively. (c) Includes accumulated amortization of capitalized leases of $50 million , $9 million , $19 million and $8 million at Duke Energy, Duke Energy Carolinas, Duke Energy Ohio and Duke Energy Indiana, respectively. (d) Includes gross property, plant and equipment cost of consolidated VIEs of $2,591 million and accumulated depreciation of consolidated VIEs of $411 million at Duke Energy.
Schedule Of Capitalized Interest	The following tables present capitalized interest, which includes the debt component of AFUDC. Years Ended December 31, (in millions) 2017 2016 2015 Duke Energy $ 128 $ 100 $ 98 Duke Energy Carolinas 45 38 38 Progress Energy 45 31 24 Duke Energy Progress 21 17 20 Duke Energy Florida 24 14 4 Duke Energy Ohio 10 8 10 Duke Energy Indiana 9 7 6 Year Ended Two Months Ended Years Ended October 31, (in millions) December 31, 2017 December 31, 2016 2016 2015 Piedmont $ 12 $ 2 $ 12 $ 11

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2017
Goodwill [Line Items]
Goodwill By Reportable Operating Segment	The following table presents goodwill by reportable operating segment for Duke Energy included on Duke Energy's Consolidated Balance Sheets at December 31, 2017 , and 2016 . Electric Utilities Gas Utilities Commercial (in millions) and Infrastructure and Infrastructure Renewables Total Goodwill Balance at December 31, 2016 $ 17,379 $ 1,924 $ 122 $ 19,425 Accumulated impairment charges (a) — — (29 ) (29 ) Goodwill at December 31, 2017 $ 17,379 $ 1,924 $ 93 $ 19,396 (a) Duke Energy evaluated the recoverability of goodwill during 2017 and recorded impairment charges of $29 million related to the Energy Management Solutions reporting unit within the Commercial Renewables segment. The fair value of the reporting unit was determined based on the market approach.
Schedule of Intangible Assets	The following tables show the carrying amount and accumulated amortization of intangible assets included in Other within Other Noncurrent Assets on the Consolidated Balance Sheets of the Duke Energy Registrants at December 31, 2017 and 2016 . December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Emission allowances $ 19 $ 1 $ 5 $ 2 $ 3 $ — $ 13 $ — Renewable energy certificates 148 38 107 107 — 3 — — Natural gas, coal and power contracts 24 — — — — — 24 — Renewable operating and development projects 79 — — — — — — — Other 6 — — — — — — 3 Total gross carrying amounts 276 39 112 109 3 3 37 3 Accumulated amortization – natural gas, coal and power contracts (19 ) — — — — — (19 ) — Accumulated amortization – renewable operating and development projects (22 ) — — — — — — — Accumulated amortization – other (5 ) — — — — — — (3 ) Total accumulated amortization (46 ) — — — — — (19 ) (3 ) Total intangible assets, net $ 230 $ 39 $ 112 $ 109 $ 3 $ 3 $ 18 $ — December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Emission allowances $ 19 $ 1 $ 6 $ 2 $ 4 $ — $ 13 $ — Renewable energy certificates 125 36 84 84 — 4 — — Natural gas, coal and power contracts 24 — — — — — 24 — Renewable operating and development projects 97 — — — — — — — Other 6 — — — — — — 3 Total gross carrying amounts 271 37 90 86 4 4 37 3 Accumulated amortization – natural gas, coal and power contracts (17 ) — — — — — (17 ) — Accumulated amortization – renewable operating and development projects (23 ) — — — — — — — Accumulated amortization – other (5 ) — — — — — — (3 ) Total accumulated amortization (45 ) — — — — — (17 ) (3 ) Total intangible assets, net $ 226 $ 37 $ 90 $ 86 $ 4 $ 4 $ 20 $ —
Schedule of Amortization Expense	The following table presents amortization expense for natural gas, coal and power contracts, renewable operating projects and other intangible assets. December 31, (in millions) 2017 2016 2015 Duke Energy $ 7 $ 6 $ 5 Duke Energy Indiana 1 1 1
Schedule of Expected Amortization Expense	The amortization amounts discussed below are estimates and actual amounts may differ from these estimates due to such factors as changes in consumption patterns, sales or impairments of emission allowances or other intangible assets, delays in the in-service dates of renewable assets, additional intangible acquisitions and other events. (in millions) 2018 2019 2020 2021 2022 Duke Energy $ 3 $ 2 $ 2 $ 2 $ 2 Duke Energy Indiana 1 — — — —

Investments in Unconsolidated46

Investments in Unconsolidated Affiliates (Tables)	12 Months Ended
	Dec. 31, 2017
Equity Method Investments and Joint Ventures [Abstract]
Investments in Equity Method Unconsolidated Affiliates	The table below outlines Duke Energy's ownership interests in natural gas pipeline companies and natural gas storage facilities. Investment Amount (in millions) Ownership December 31, December 31, Entity Name Interest 2017 2016 Pipeline Investments Atlantic Coast Pipeline, LLC (a) 47 % $ 397 $ 265 Sabal Trail Transmission, LLC 7.5 % 219 140 Constitution Pipeline, LLC (a) 24 % 81 82 Cardinal Pipeline Company, LLC (b) 21.49 % 11 16 Storage Facilities Pine Needle LNG Company, LLC (b) 45 % 13 16 Hardy Storage Company, LLC (b) 50 % 42 47 Total Investments (c) $ 763 $ 566 (a) During the year ended December 31, 2017, Piedmont transferred its share of ownership interest in ACP and Constitution to a wholly owned subsidiary of Duke Energy at book value. (b) Piedmont owns the Cardinal, Pine Needle and Hardy Storage investments. (c) Duke Energy includes purchase accounting adjustments related to Piedmont. The following table presents Duke Energy’s investments in unconsolidated affiliates accounted for under the equity method, as well as the respective equity in earnings, by segment. Years Ended December 31, 2017 2016 2015 Equity in Equity in Equity in (in millions) Investments earnings Investments earnings earnings Electric Utilities and Infrastructure $ 89 $ 5 $ 93 $ 5 $ (2 ) Gas Utilities and Infrastructure 763 62 566 19 1 Commercial Renewables 190 (5 ) 185 (82 ) (6 ) Other 133 57 81 43 76 Total $ 1,175 $ 119 $ 925 $ (15 ) $ 69

Related Party Transactions (Tab

Related Party Transactions (Tables)	12 Months Ended
	Dec. 31, 2017
Related Party Transaction [Line Items]
Related Party Transactions, Other Revenue and Expense	Material amounts related to transactions with related parties included in the Consolidated Statements of Operations and Comprehensive Income are presented in the following table. Years Ended December 31, (in millions) 2017 2016 2015 Duke Energy Carolinas Corporate governance and shared service expenses (a) $ 858 $ 831 $ 914 Indemnification coverages (b) 23 22 24 JDA revenue (c) 49 38 51 JDA expense (c) 145 156 183 Intercompany natural gas purchases (d) 9 2 — Progress Energy Corporate governance and shared service expenses (a) $ 736 $ 710 $ 712 Indemnification coverages (b) 38 35 38 JDA revenue (c) 145 156 183 JDA expense (c) 49 38 51 Intercompany natural gas purchases (d) 77 19 — Duke Energy Progress Corporate governance and shared service expenses (a) $ 438 $ 397 $ 403 Indemnification coverages (b) 15 14 16 JDA revenue (c) 145 156 183 JDA expense (c) 49 38 51 Intercompany natural gas purchases (d) 77 19 — Duke Energy Florida Corporate governance and shared service expenses (a) $ 298 $ 313 $ 309 Indemnification coverages (b) 23 21 22 Duke Energy Ohio Corporate governance and shared service expenses (a) $ 363 $ 356 $ 342 Indemnification coverages (b) 5 5 6 Duke Energy Indiana Corporate governance and shared service expenses (a) $ 370 $ 366 $ 349 Indemnification coverages (b) 8 8 9 Piedmont Corporate governance and shared service expenses (a) $ 50 Indemnification coverages (b) 2 Intercompany natural gas sales (d) 86 (a) The Subsidiary Registrants are charged their proportionate share of corporate governance and other shared services costs, primarily related to human resources, employee benefits, information technology, legal and accounting fees, as well as other third-party costs. These amounts are primarily recorded in Operation, maintenance and other on the Consolidated Statements of Operations and Comprehensive Income. (b) The Subsidiary Registrants incur expenses related to certain indemnification coverages through Bison, Duke Energy’s wholly owned captive insurance subsidiary. These expenses are recorded in Operation, maintenance and other on the Consolidated Statements of Operations and Comprehensive Income. (c) Duke Energy Carolinas and Duke Energy Progress participate in a JDA, which allows the collective dispatch of power plants between the service territories to reduce customer rates. Revenues from the sale of power and expenses from the purchase of power pursuant to the JDA are recorded in Operating Revenues and Fuel used in electric generation and purchased power, respectively, on the Consolidated Statements of Operations and Comprehensive Income. (d) Piedmont provides long-term natural gas delivery service to certain Duke Energy Carolinas and Duke Energy Progress natural gas-fired generation facilities. Piedmont records the sales in Regulated natural gas revenues, and Duke Energy Carolinas and Duke Energy Progress record the related purchases in Fuel used in electric generation and purchased power on their respective Consolidated Statements of Operations and Comprehensive Income. The amounts are not eliminated in accordance with rate-based accounting regulations. For the two months ended December 31, 2016, and for sales made subsequent to the acquisition for the year ended October 31, 2016, Piedmont recorded $14 million and $7 million , respectively, of natural gas sales with Duke Energy. For sales made prior to the acquisition for the year ended October 31, 2016, and for the year ended October 31, 2015, Piedmont recorded $74 million and $83 million , respectively of natural gas sales with Duke Energy.
Progress Energy [Member]
Related Party Transaction [Line Items]
Related Party Transactions, Other Revenue and Expense	Income taxes recorded represent amounts the Subsidiary Registrants would incur as separate C-Corporations. The following table includes the balance of intercompany income tax receivables and payables for the Subsidiary Registrants. Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Carolinas Energy Progress Florida Ohio Indiana Piedmont December 31, 2017 Intercompany income tax receivable $ — $ 168 $ — $ 44 $ 22 $ — $ 7 Intercompany income tax payable 44 — 21 — — 35 — December 31, 2016 Intercompany income tax receivable $ 1 $ — $ — $ 37 $ — $ — $ — Intercompany income tax payable — 37 90 — 1 3 38
Piedmont Natural Gas [Member]
Related Party Transaction [Line Items]
Related Party Transactions, Other Revenue and Expense	The following table presents expenses that are included in Cost of natural gas on Piedmont's Consolidated Statements of Operations and Comprehensive Income. Year Ended December 31, Two Months Ended December 31, Years Ended October 31, (in millions) Type of expense 2017 2016 2016 2015 Cardinal Transportation Costs $ 8 $ 2 $ 9 $ 9 Pine Needle Natural Gas Storage Costs 8 2 11 11 Hardy Storage Natural Gas Storage Costs 9 2 9 9 Total $ 25 $ 6 $ 29 $ 29 Piedmont had accounts payable to its equity method investments of $2 million at December 31, 2017 , and 2016 related to these transactions. These amounts are included in Accounts payable on the Consolidated Balance Sheets.

Derivatives and Hedging (Tables

Derivatives and Hedging (Tables)	12 Months Ended
	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Notional Amounts of Outstanding Derivative Positions	The following tables show notional amounts of outstanding derivatives related to interest rate risk. December 31, 2017 Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Cash flow hedges (a) $ 660 $ — $ — $ — $ — $ — Undesignated contracts 927 400 500 250 250 27 Total notional amount $ 1,587 $ 400 $ 500 $ 250 $ 250 $ 27 December 31, 2016 Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Cash flow hedges (a) $ 750 $ — $ — $ — $ — $ — Undesignated contracts 927 400 500 250 250 27 Total notional amount $ 1,677 $ 400 $ 500 $ 250 $ 250 $ 27 (a) Duke Energy includes amounts related to consolidated VIEs of $660 million and $750 million at December 31, 2017 , and 2016 , respectively. During 2016, Duke Energy entered into interest rate swaps related to solar financing with an outstanding notional amount of $300 million , including $81 million of four-year swaps and $219 million of 18-year swaps, at December 31, 2016. See note 6 for additional information related to the solar facilities financing. The tables below include volumes of outstanding commodity derivatives. Amounts disclosed represent the absolute value of notional volumes of commodity contracts excluding NPNS. The Duke Energy Registrants have netted contractual amounts where offsetting purchase and sale contracts exist with identical delivery locations and times of delivery. Where all commodity positions are perfectly offset, no quantities are shown. December 31, 2017 Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy Carolinas Energy Progress Florida Indiana Piedmont Electricity (gigawatt-hours) 34 — — — — 34 — Natural gas (millions of dekatherms) 770 105 183 133 50 2 480 December 31, 2016 Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy Carolinas Energy Progress Florida Indiana Piedmont Electricity (gigawatt-hours) 147 — — — — 147 — Natural gas (millions of dekatherms) 890 91 269 118 151 1 529
Location and Fair Value of Derivatives Recognized in the Consolidated Balance Sheets	The following tables show the fair value and balance sheet location of derivative instruments. Although derivatives subject to master netting arrangements are netted on the Consolidated Balance Sheets, the fair values presented below are shown gross and cash collateral on the derivatives has not been netted against the fair values shown. Derivative Assets December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Commodity Contracts Not Designated as Hedging Instruments Current $ 34 $ 2 $ 2 $ 1 $ 1 $ 1 $ 27 $ 2 Noncurrent 1 — 1 1 — — — — Total Derivative Assets – Commodity Contracts $ 35 $ 2 $ 3 $ 2 $ 1 $ 1 $ 27 $ 2 Interest Rate Contracts Designated as Hedging Instruments Current $ 1 $ — $ — $ — $ — $ — $ — $ — Noncurrent 15 — — — — — — — Total Derivative Assets – Interest Rate Contracts $ 16 $ — $ — $ — $ — $ — $ — $ — Total Derivative Assets $ 51 $ 2 $ 3 $ 2 $ 1 $ 1 $ 27 $ 2 Derivative Liabilities December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Commodity Contracts Not Designated as Hedging Instruments Current $ 36 $ 6 $ 18 $ 8 $ 10 $ — $ — $ 11 Noncurrent 146 4 10 4 — — — 131 Total Derivative Liabilities – Commodity Contracts $ 182 $ 10 $ 28 $ 12 $ 10 $ — $ — $ 142 Interest Rate Contracts Designated as Hedging Instruments Current $ 29 $ 25 $ — $ — $ — $ — $ — $ — Noncurrent 6 — — — — — — — Not Designated as Hedging Instruments Current 1 — 1 — — 1 — — Noncurrent 12 — 7 6 2 4 — — Total Derivative Liabilities – Interest Rate Contracts $ 48 $ 25 $ 8 $ 6 $ 2 $ 5 $ — $ — Total Derivative Liabilities $ 230 $ 35 $ 36 $ 18 $ 12 $ 5 $ — $ 142 Derivative Assets December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Commodity Contracts Not Designated as Hedging Instruments Current $ 108 $ 23 $ 61 $ 35 $ 26 $ 4 $ 16 $ 3 Noncurrent 32 10 21 10 11 1 — — Total Derivative Assets – Commodity Contracts $ 140 $ 33 $ 82 $ 45 $ 37 $ 5 $ 16 $ 3 Interest Rate Contracts Designated as Hedging Instruments Noncurrent $ 19 $ — $ — $ — $ — $ — $ — $ — Not Designated as Hedging Instruments Current 3 — 3 1 2 — — — Total Derivative Assets – Interest Rate Contracts $ 22 $ — $ 3 $ 1 $ 2 $ — $ — $ — Total Derivative Assets $ 162 $ 33 $ 85 $ 46 $ 39 $ 5 $ 16 $ 3 Derivative Liabilities December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Commodity Contracts Not Designated as Hedging Instruments Current $ 43 $ — $ 12 $ — $ 12 $ — $ 2 $ 35 Noncurrent 166 1 7 1 — — — 152 Total Derivative Liabilities – Commodity Contracts $ 209 $ 1 $ 19 $ 1 $ 12 $ — $ 2 $ 187 Interest Rate Contracts Designated as Hedging Instruments Current $ 8 $ — $ — $ — $ — $ — $ — $ — Noncurrent 8 — — — — — — — Not Designated as Hedging Instruments Current 1 — — — — 1 — — Noncurrent 26 15 6 6 — 5 — — Total Derivative Liabilities – Interest Rate Contracts $ 43 $ 15 $ 6 $ 6 $ — $ 6 $ — $ — Total Derivative Liabilities $ 252 $ 16 $ 25 $ 7 $ 12 $ 6 $ 2 $ 187
Offsetting Assets	Derivative Assets December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Current Gross amounts recognized $ 111 $ 23 $ 64 $ 36 $ 28 $ 4 $ 16 $ 3 Gross amounts offset (11 ) — (11 ) — (11 ) — — — Net amounts presented in Current Assets: Other $ 100 $ 23 $ 53 $ 36 $ 17 $ 4 $ 16 $ 3 Noncurrent Gross amounts recognized $ 51 $ 10 $ 21 $ 10 $ 11 $ 1 $ — $ — Gross amounts offset (2 ) (1 ) (1 ) (1 ) — — — — Net amounts presented in Other Noncurrent Assets: Other $ 49 $ 9 $ 20 $ 9 $ 11 $ 1 $ — $ — The following tables present the line items on the Consolidated Balance Sheets where derivatives are reported. Substantially all of Duke Energy's outstanding derivative contracts are subject to enforceable master netting arrangements. The Gross amounts offset in the tables below show the effect of these netting arrangements on financial position and include collateral posted to offset the net position. The amounts shown are calculated by counterparty. Accounts receivable or accounts payable may also be available to offset exposures in the event of bankruptcy. These amounts are not included in the tables below. Derivative Assets December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Current Gross amounts recognized $ 35 $ 2 $ 2 $ 1 $ 1 $ 1 $ 27 $ 2 Gross amounts offset — — — — — — — — Net amounts presented in Current Assets: Other $ 35 $ 2 $ 2 $ 1 $ 1 $ 1 $ 27 $ 2 Noncurrent Gross amounts recognized $ 16 $ — $ 1 $ 1 $ — $ — $ — $ — Gross amounts offset — — — — — — — — Net amounts presented in Other Noncurrent Assets: Other $ 16 $ — $ 1 $ 1 $ — $ — $ — $ —
Offsetting Liabilities	Derivative Liabilities December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Current Gross amounts recognized $ 52 $ — $ 12 $ — $ 12 $ 1 $ 2 $ 35 Gross amounts offset (11 ) — (11 ) — (11 ) — — — Net amounts presented in Current Liabilities: Other $ 41 $ — $ 1 $ — $ 1 $ 1 $ 2 $ 35 Noncurrent Gross amounts recognized $ 200 $ 16 $ 13 $ 7 $ — $ 5 $ — $ 152 Gross amounts offset (2 ) (1 ) (1 ) (1 ) — — — — Net amounts presented in Other Noncurrent Liabilities: Other $ 198 $ 15 $ 12 $ 6 $ — $ 5 $ — $ 152 Derivative Liabilities December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Current Gross amounts recognized $ 66 $ 31 $ 19 $ 8 $ 10 $ 1 $ — $ 11 Gross amounts offset (3 ) (2 ) (2 ) (2 ) — — — — Net amounts presented in Current Liabilities: Other $ 63 $ 29 $ 17 $ 6 $ 10 $ 1 $ — $ 11 Noncurrent Gross amounts recognized $ 164 $ 4 $ 17 $ 10 $ 2 $ 4 $ — $ 131 Gross amounts offset (1 ) — (1 ) (1 ) — — — — Net amounts presented in Other Noncurrent Liabilities: Other $ 163 $ 4 $ 16 $ 9 $ 2 $ 4 $ — $ 131
Derivative Contracts with Contingent Credit Features	The following tables show information with respect to derivative contracts that are in a net liability position and contain objective credit-risk-related payment provisions. December 31, 2017 Duke Duke Duke Duke Energy Progress Energy Energy (in millions) Energy Carolinas Energy Progress Florida Aggregate fair value of derivatives in a net liability position $ 59 $ 35 $ 25 $ 15 $ 10 Fair value of collateral already posted — — — — — Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered 59 35 25 15 10 December 31, 2016 Duke Duke Duke Duke Energy Progress Energy Energy (in millions) Energy Carolinas Energy Progress Florida Aggregate fair value of derivatives in a net liability position $ 34 $ 16 $ 18 $ 6 $ 12 Fair value of collateral already posted — — — — — Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered 34 16 18 6 12 The Duke Energy Registrants have elected to offset cash collateral and fair values of derivatives. For amounts to be netted, the derivative and cash collateral must be executed with the same counterparty under the same master netting arrangement.

Investments in Debt and Equit49

Investments in Debt and Equity Securities (Tables)	12 Months Ended
	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Available-For-Sale Investments	The following table presents the estimated fair value of investments in AFS securities. December 31, 2017 December 31, 2016 Gross Gross Gross Gross Unrealized Unrealized Unrealized Unrealized Holding Holding Estimated Holding Holding Estimated (in millions) Gains Losses Fair Value Gains Losses (a) Fair Value NDTF Cash and cash equivalents $ — $ — $ 115 $ — $ — $ 111 Equity securities 2,805 27 4,914 2,092 54 4,106 Corporate debt securities 17 2 570 10 8 528 Municipal bonds 4 3 344 3 10 331 U.S. government bonds 11 7 1,027 10 8 984 Other debt securities — 1 118 — 3 124 Total NDTF $ 2,837 $ 40 $ 7,088 $ 2,115 $ 83 $ 6,184 Other Investments Cash and cash equivalents $ — $ — $ 15 $ — $ — $ 25 Equity securities 59 — 123 38 — 104 Corporate debt securities 1 — 57 1 1 66 Municipal bonds 2 1 83 2 1 82 U.S. government bonds — — 41 — 1 51 Other debt securities — 1 44 — 2 42 Total Other Investments $ 62 $ 2 $ 363 $ 41 $ 5 $ 370 Total Investments $ 2,899 $ 42 $ 7,451 $ 2,156 $ 88 $ 6,554
Investments Classified by Contractual Maturity Date	The table below summarizes the maturity date for debt securities. (in millions) December 31, 2017 Due in one year or less $ 117 Due after one through five years 552 Due after five through 10 years 554 Due after 10 years 1,061 Total $ 2,284
Schedule of Realized Gain (Loss)	Realized gains and losses, which were determined on a specific identification basis, from sales of AFS securities were as follows. Years Ended December 31, (in millions) 2017 2016 2015 Realized gains $ 202 $ 246 $ 193 Realized losses 160 187 98
Duke Energy Carolinas [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-For-Sale Investments	The following table presents the estimated fair value of investments in AFS securities. December 31, 2017 December 31, 2016 Gross Gross Gross Gross Unrealized Unrealized Unrealized Unrealized Holding Holding Estimated Holding Holding Estimated (in millions) Gains Losses Fair Value Gains Losses (a) Fair Value NDTF Cash and cash equivalents $ — $ — $ 32 $ — $ — $ 18 Equity securities 1,531 12 2,692 1,157 28 2,245 Corporate debt securities 9 2 359 5 6 354 Municipal bonds — 1 60 1 2 67 U.S. government bonds 3 4 503 2 5 458 Other debt securities — 1 112 — 3 116 Total NDTF $ 1,543 $ 20 $ 3,758 $ 1,165 $ 44 $ 3,258 Other Investments Other debt securities $ — $ — $ — $ — $ 1 $ 3 Total Other Investments $ — $ — $ — $ — $ 1 $ 3 Total Investments $ 1,543 $ 20 $ 3,758 $ 1,165 $ 45 $ 3,261
Investments Classified by Contractual Maturity Date	The table below summarizes the maturity date for debt securities. (in millions) December 31, 2017 Due in one year or less $ 9 Due after one through five years 204 Due after five through 10 years 300 Due after 10 years 521 Total $ 1,034
Schedule of Realized Gain (Loss)	Realized gains and losses, which were determined on a specific identification basis, from sales of AFS securities were as follows. Years Ended December 31, (in millions) 2017 2016 2015 Realized gains $ 135 $ 157 $ 158 Realized losses 103 121 83
Progress Energy [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-For-Sale Investments	The following table presents the estimated fair value of investments in AFS securities. December 31, 2017 December 31, 2016 Gross Gross Gross Gross Unrealized Unrealized Unrealized Unrealized Holding Holding Estimated Holding Holding Estimated (in millions) Gains Losses Fair Value Gains Losses (a) Fair Value NDTF Cash and cash equivalents $ — $ — $ 83 $ — $ — $ 93 Equity securities 1,274 15 2,222 935 26 1,861 Corporate debt securities 8 — 211 5 2 174 Municipal bonds 4 2 284 2 8 264 U.S. government bonds 8 3 524 8 3 526 Other debt securities — — 6 — — 8 Total NDTF $ 1,294 $ 20 $ 3,330 $ 950 $ 39 $ 2,926 Other Investments Cash and cash equivalents $ — $ — $ 12 $ — $ — $ 21 Municipal bonds 2 — 47 2 — 44 Total Other Investments $ 2 $ — $ 59 $ 2 $ — $ 65 Total Investments $ 1,296 $ 20 $ 3,389 $ 952 $ 39 $ 2,991
Investments Classified by Contractual Maturity Date	The table below summarizes the maturity date for debt securities. (in millions) December 31, 2017 Due in one year or less $ 94 Due after one through five years 301 Due after five through 10 years 203 Due after 10 years 474 Total $ 1,072
Schedule of Realized Gain (Loss)	Realized gains and losses, which were determined on a specific identification basis, from sales of AFS securities were as follows. Years Ended December 31, (in millions) 2017 2016 2015 Realized gains $ 65 $ 84 $ 33 Realized losses 56 64 13
Duke Energy Progress [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-For-Sale Investments	The following table presents the estimated fair value of investments in AFS securities. December 31, 2017 December 31, 2016 Gross Gross Gross Gross Unrealized Unrealized Unrealized Unrealized Holding Holding Estimated Holding Holding Estimated (in millions) Gains Losses Fair Value Gains Losses (a) Fair Value NDTF Cash and cash equivalents $ — $ — $ 50 $ — $ — $ 45 Equity securities 980 12 1,795 704 21 1,505 Corporate debt securities 6 149 4 1 120 Municipal bonds 4 2 283 2 8 263 U.S. government bonds 5 2 310 5 2 275 Other debt securities — — 4 — — 5 Total NDTF $ 995 $ 16 $ 2,591 $ 715 $ 32 $ 2,213 Other Investments Cash and cash equivalents $ — $ — $ 1 $ — $ — $ 1 Total Other Investments $ — $ — $ 1 $ — $ — $ 1 Total Investments $ 995 $ 16 $ 2,592 $ 715 $ 32 $ 2,214
Investments Classified by Contractual Maturity Date	The table below summarizes the maturity date for debt securities. (in millions) December 31, 2017 Due in one year or less $ 21 Due after one through five years 219 Due after five through 10 years 146 Due after 10 years 360 Total $ 746
Schedule of Realized Gain (Loss)	Realized gains and losses, which were determined on a specific identification basis, from sales of AFS securities were as follows. Years Ended December 31, (in millions) 2017 2016 2015 Realized gains $ 54 $ 71 $ 26 Realized losses 48 55 11
Duke Energy Florida [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-For-Sale Investments	The following table presents the estimated fair value of investments in AFS securities. December 31, 2017 December 31, 2016 Gross Gross Gross Gross Unrealized Unrealized Unrealized Unrealized Holding Holding Estimated Holding Holding Estimated (in millions) Gains Losses Fair Value Gains Losses (a) Fair Value NDTF Cash and cash equivalents $ — $ — $ 33 $ — $ — $ 48 Equity securities 294 3 427 231 5 356 Corporate debt securities 2 — 62 1 1 54 Municipal bonds — — 1 — — 1 U.S. government bonds 3 1 214 3 1 251 Other debt securities — — 2 — — 3 Total NDTF (a) $ 299 $ 4 $ 739 $ 235 $ 7 $ 713 Other Investments Cash and cash equivalents $ — $ — $ 1 $ — $ — $ 4 Municipal bonds 2 — 47 2 — 44 Total Other Investments $ 2 $ — $ 48 $ 2 $ — $ 48 Total Investments $ 301 $ 4 $ 787 $ 237 $ 7 $ 761 (a) During the year ended December 31, 2017 , Duke Energy Florida continued to receive reimbursements from the NDTF for costs related to ongoing decommissioning activity of the Crystal River Unit 3 nuclear plant.
Investments Classified by Contractual Maturity Date	The table below summarizes the maturity date for debt securities. (in millions) December 31, 2017 Due in one year or less $ 73 Due after one through five years 82 Due after five through 10 years 57 Due after 10 years 114 Total $ 326
Schedule of Realized Gain (Loss)	Realized gains and losses, which were determined on a specific identification basis, from sales of AFS securities were as follows. Years Ended December 31, (in millions) 2017 2016 2015 Realized gains $ 11 $ 13 $ 7 Realized losses 8 9 2
Duke Energy Indiana [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-For-Sale Investments	The following table presents the estimated fair value of investments in AFS securities. December 31, 2017 December 31, 2016 Gross Gross Gross Gross Unrealized Unrealized Unrealized Unrealized Holding Holding Estimated Holding Holding Estimated (in millions) Gains Losses Fair Value Gains Losses (a) Fair Value Other Investments Equity securities $ 49 $ — $ 97 $ 33 $ — $ 79 Corporate debt securities — — 3 — — 2 Municipal bonds — 1 28 — 1 28 U.S. government bonds — — — — — 1 Total Other Investments $ 49 $ 1 $ 128 $ 33 $ 1 $ 110 Total Investments $ 49 $ 1 $ 128 $ 33 $ 1 $ 110
Investments Classified by Contractual Maturity Date	The table below summarizes the maturity date for debt securities. (in millions) December 31, 2017 Due in one year or less $ 5 Due after one through five years 12 Due after five through 10 years 7 Due after 10 years 7 Total $ 31

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurement Amounts For Assets And Liabilities	The following tables provide recorded balances for assets and liabilities measured at fair value on a recurring basis on the Consolidated Balance Sheets. Derivative amounts in the table below for all Duke Energy Registrants exclude cash collateral, which is disclosed in Note 14 . See Note 15 for additional information related to investments by major security type for the Duke Energy Registrants. December 31, 2017 (in millions) Total Fair Value Level 1 Level 2 Level 3 Not Categorized NDTF equity securities $ 4,914 $ 4,840 $ — $ — $ 74 NDTF debt securities 2,174 635 1,539 — — Other AFS equity securities 123 123 — — — Other trading and AFS debt securities 241 57 184 — — Derivative assets 51 3 20 28 — Total assets 7,503 5,658 1,743 28 74 Derivative liabilities (230 ) (2 ) (86 ) (142 ) — Net assets (liabilities) $ 7,273 $ 5,656 $ 1,657 $ (114 ) $ 74 December 31, 2016 (in millions) Total Fair Value Level 1 Level 2 Level 3 Not Categorized NDTF equity securities $ 4,106 $ 4,029 $ — $ — $ 77 NDTF debt securities 2,078 632 1,446 — — Other trading and AFS equity securities 104 104 — — — Other trading and AFS debt securities 266 75 186 5 — Derivative assets 162 5 136 21 — Total assets 6,716 4,845 1,768 26 77 Derivative liabilities (252 ) (2 ) (63 ) (187 ) — Net assets $ 6,464 $ 4,843 $ 1,705 $ (161 ) $ 77
Reconciliation Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Using Unobservable Inputs	The following tables provide reconciliations of beginning and ending balances of assets and liabilities measured at fair value using Level 3 measurements. Amounts included in earnings for derivatives are primarily included in Cost of natural gas on the Duke Energy Registrants' Consolidated Statements of Operations and Comprehensive Income. Amounts included in changes of net assets on the Duke Energy Registrants' Consolidated Balance Sheets are included in regulatory assets or liabilities. All derivative assets and liabilities are presented on a net basis. December 31, 2017 December 31, 2016 (in millions) Investments Derivatives (net) Total Investments Derivatives (net) Total Balance at beginning of period $ 5 $ (166 ) $ (161 ) $ 5 $ 10 $ 15 Total pretax realized or unrealized gains included in comprehensive income 1 — 1 — — — Derivative liability resulting from the acquisition of Piedmont — — — — (187 ) (187 ) Purchases, sales, issuances and settlements: Purchases — 55 55 — 33 33 Sales (6 ) — (6 ) — — — Settlements — (47 ) (47 ) — (28 ) (28 ) Total gains included on the Consolidated Balance Sheet — 44 44 — 6 6 Balance at end of period $ — $ (114 ) $ (114 ) $ 5 $ (166 ) $ (161 )
Quantitative Information Table - Level 3	The following tables include quantitative information about the Duke Energy Registrants' derivatives classified as Level 3. December 31, 2017 Fair Value Investment Type (in millions) Valuation Technique Unobservable Input Range Duke Energy Ohio FTRs $ 1 RTO auction pricing FTR price – per MWh $ 0.07 – $ 1.41 Duke Energy Indiana FTRs 27 RTO auction pricing FTR price – per MWh (0.77 ) – 7.44 Piedmont Natural gas contracts (142 ) Discounted cash flow Forward natural gas curves - price per MMBtu 2.10 – 2.88 Duke Energy Total Level 3 derivatives $ (114 ) December 31, 2016 Fair Value Investment Type (in millions) Valuation Technique Unobservable Input Range Duke Energy Ohio FTRs $ 5 RTO auction pricing FTR price – per MWh 0.77 – 3.52 Duke Energy Indiana FTRs 16 RTO auction pricing FTR price – per MWh (0.83 ) – 9.32 Piedmont Natural gas contracts (187 ) Discounted cash flow Forward natural gas curves - price per MMBtu 2.31 – 4.18 Duke Energy Total Level 3 derivatives $ (166 )
Schedule of Long-term debt Fair Value	The fair value and book value of long-term debt, including current maturities, is summarized in the following table. Estimates determined are not necessarily indicative of amounts that could have been settled in current markets. Fair value of long-term debt uses Level 2 measurements. December 31, 2017 December 31, 2016 (in millions) Book Value Fair Value Book Value Fair Value Duke Energy $ 52,279 $ 55,331 $ 47,895 $ 49,161 Duke Energy Carolinas 10,103 11,372 9,603 10,494 Progress Energy 17,837 20,000 17,541 19,107 Duke Energy Progress 7,357 7,992 7,011 7,357 Duke Energy Florida 7,095 7,953 6,125 6,728 Duke Energy Ohio 2,067 2,249 1,884 2,020 Duke Energy Indiana 3,783 4,464 3,786 4,260 Piedmont 2,037 2,209 1,821 1,933
Duke Energy Carolinas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurement Amounts For Assets And Liabilities	The following tables provide recorded balances for assets and liabilities measured at fair value on a recurring basis on the Consolidated Balance Sheets. December 31, 2017 (in millions) Total Fair Value Level 1 Level 2 Level 3 Not Categorized NDTF equity securities $ 2,692 $ 2,618 $ — $ — $ 74 NDTF debt securities 1,066 204 862 — — Derivative assets 2 — 2 — — Total assets 3,760 2,822 864 — 74 Derivative liabilities (35 ) (1 ) (34 ) — — Net assets $ 3,725 $ 2,821 $ 830 $ — $ 74 December 31, 2016 (in millions) Total Fair Value Level 1 Level 2 Level 3 Not Categorized NDTF equity securities $ 2,245 $ 2,168 $ — $ — $ 77 NDTF debt securities 1,013 178 835 — — Other AFS debt securities 3 — — 3 — Derivative assets 33 — 33 — — Total assets 3,294 2,346 868 3 77 Derivative liabilities (16 ) — (16 ) — — Net assets $ 3,278 $ 2,346 $ 852 $ 3 $ 77
Reconciliation Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Using Unobservable Inputs	The following table provides reconciliations of beginning and ending balances of assets and liabilities measured at fair value using Level 3 measurements. Investments Years Ended December 31, (in millions) 2017 2016 Balance at beginning of period $ 3 $ 3 Total pretax realized or unrealized gains included in comprehensive income 1 — Purchases, sales, issuances and settlements: Sales (4 ) — Balance at end of period $ — $ 3
Progress Energy [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurement Amounts For Assets And Liabilities	The following table provides recorded balances for assets and liabilities measured at fair value on a recurring basis on the Consolidated Balance Sheets. December 31, 2017 December 31, 2016 (in millions) Total Fair Value Level 1 Level 2 Total Fair Value Level 1 Level 2 NDTF equity securities $ 2,222 $ 2,222 $ — $ 1,861 $ 1,861 $ — NDTF debt securities 1,108 431 677 1,065 454 611 Other AFS debt securities 59 12 47 65 21 44 Derivative assets 3 1 2 85 — 85 Total assets 3,392 2,666 726 3,076 2,336 740 Derivative liabilities (36 ) (1 ) (35 ) (25 ) — (25 ) Net assets $ 3,356 $ 2,665 $ 691 $ 3,051 $ 2,336 $ 715
Duke Energy Progress [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurement Amounts For Assets And Liabilities	The following table provides recorded balances for assets and liabilities measured at fair value on a recurring basis on the Consolidated Balance Sheets. December 31, 2017 December 31, 2016 (in millions) Total Fair Value Level 1 Level 2 Total Fair Value Level 1 Level 2 NDTF equity securities $ 1,795 $ 1,795 $ — $ 1,505 $ 1,505 $ — NDTF debt securities 796 243 553 708 207 501 Other AFS debt securities 1 1 — 1 1 — Derivative assets 2 1 1 46 — 46 Total assets 2,594 2,040 554 2,260 1,713 547 Derivative liabilities (18 ) (1 ) (17 ) (7 ) — (7 ) Net assets $ 2,576 $ 2,039 $ 537 $ 2,253 $ 1,713 $ 540
Duke Energy Florida [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurement Amounts For Assets And Liabilities	The following table provides recorded balances for assets and liabilities measured at fair value on a recurring basis on the Consolidated Balance Sheets. December 31, 2017 December 31, 2016 (in millions) Total Fair Value Level 1 Level 2 Total Fair Value Level 1 Level 2 NDTF equity securities $ 427 $ 427 $ — $ 356 $ 356 $ — NDTF debt securities 312 188 124 357 247 110 Other AFS debt securities 48 1 47 48 4 44 Derivative assets 1 — 1 39 — 39 Total assets 788 616 172 800 607 193 Derivative liabilities (12 ) — (12 ) (12 ) — (12 ) Net assets $ 776 $ 616 $ 160 $ 788 $ 607 $ 181
Duke Energy Ohio [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurement Amounts For Assets And Liabilities	The following table provides recorded balances for assets and liabilities measured at fair value on a recurring basis on the Consolidated Balance Sheets. December 31, 2017 December 31, 2016 (in millions) Total Fair Value Level 2 Level 3 Total Fair Value Level 2 Level 3 Derivative assets $ 1 $ — $ 1 $ 5 $ — $ 5 Derivative liabilities (5 ) (5 ) — (6 ) (6 ) — Net (liabilities) assets $ (4 ) $ (5 ) $ 1 $ (1 ) $ (6 ) $ 5
Reconciliation Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Using Unobservable Inputs	The following table provides a reconciliation of beginning and ending balances of assets and liabilities measured at fair value using Level 3 measurements. Derivatives (net) Years Ended December 31, (in millions) 2017 2016 Balance at beginning of period $ 5 $ 3 Purchases, sales, issuances and settlements: Purchases 3 5 Settlements (4 ) (5 ) Total gains included on the Consolidated Balance Sheet (3 ) 2 Balance at end of period $ 1 $ 5
Duke Energy Indiana [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurement Amounts For Assets And Liabilities	The following table provides recorded balances for assets and liabilities measured at fair value on a recurring basis on the Consolidated Balance Sheets. December 31, 2017 December 31, 2016 (in millions) Total Fair Value Level 1 Level 2 Level 3 Total Fair Value Level 1 Level 2 Level 3 Other AFS equity securities $ 97 $ 97 $ — $ — $ 79 $ 79 $ — $ — Other AFS debt securities 31 — 31 — 31 — 31 — Derivative assets 27 — — 27 16 — — 16 Total assets 155 97 31 27 126 79 31 16 Derivative liabilities — — — — (2 ) (2 ) — — Net assets $ 155 $ 97 $ 31 $ 27 $ 124 $ 77 $ 31 $ 16
Reconciliation Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Using Unobservable Inputs	The following table provides a reconciliation of beginning and ending balances of assets and liabilities measured at fair value using Level 3 measurements. Derivatives (net) Years Ended December 31, (in millions) 2017 2016 Balance at beginning of period $ 16 $ 7 Purchases, sales, issuances and settlements: Purchases 52 29 Settlements (43 ) (24 ) Total gains included on the Consolidated Balance Sheet 2 4 Balance at end of period $ 27 $ 16
Piedmont Natural Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurement Amounts For Assets And Liabilities	The following table provides recorded balances for assets and liabilities measured at fair value on a recurring basis on the Consolidated Balance Sheets. December 31, 2017 December 31, 2016 (in millions) Total Fair Value Level 1 Level 3 Total Fair Value Level 1 Level 3 Other trading equity securities $ — $ — $ — $ 4 $ 4 $ — Other trading debt securities 1 1 — 1 1 — Derivative assets 2 2 — 3 3 — Total assets 3 3 — 8 8 — Derivative liabilities (142 ) — (142 ) (187 ) — (187 ) Net assets $ (139 ) $ 3 $ (142 ) $ (179 ) $ 8 $ (187 )
Reconciliation Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Using Unobservable Inputs	The following table provides a reconciliation of beginning and ending balances of assets and liabilities measured at fair value using Level 3 measurements. Derivatives (net) Year Ended Two Months Ended Year Ended (in millions) December 31, 2017 December 31, 2016 October 31, 2016 Balance at beginning of period $ (187 ) $ (188 ) $ — Total gains (losses) and settlements 45 1 (188 ) Balance at end of period $ (142 ) $ (187 ) $ (188 )

Variable Interest Entities (Tab

Variable Interest Entities (Tables)	12 Months Ended
	Dec. 31, 2017
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Schedule Of Variable Interest Entities	The following table outlines amounts and expiration dates of the credit facilities described above. Duke Energy Duke Energy Duke Energy Duke Energy Carolinas Progress Florida CRC DERF DEPR DEFR Expiration date December 2020 December 2020 February 2019 April 2019 Credit facility amount (in millions) $ 325 $ 450 $ 300 $ 225 Amounts borrowed at December 31, 2017 325 450 300 225 Amounts borrowed at December 31, 2016 325 425 300 225
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Schedule Of Variable Interest Entities	The following tables summarize the impact of non-consolidated VIEs on the Consolidated Balance Sheets. December 31, 2017 Duke Energy Duke Duke Pipeline Commercial Other Energy Energy (in millions) Investments Renewables VIEs (a) Total Ohio Indiana Receivables from affiliated companies $ — $ — $ — $ — $ 87 $ 106 Investments in equity method unconsolidated affiliates 697 180 42 919 — — Other noncurrent assets 17 — — 17 — — Total assets $ 714 $ 180 $ 42 $ 936 $ 87 $ 106 Taxes accrued (29 ) — — (29 ) — — Other current liabilities — — 4 4 — — Deferred income taxes 42 — — 42 — — Other noncurrent liabilities — — 12 12 — — Total liabilities $ 13 $ — $ 16 $ 29 $ — $ — Net assets $ 701 $ 180 $ 26 $ 907 $ 87 $ 106 (a) Duke Energy holds a 50 percent equity interest in Duke-American Transmission Company, LLC (DATC). As of December 31, 2016, DATC was considered a VIE due to having insufficient equity to finance its own activities without subordinated financial support. However, DATC is no longer considered a VIE based on sufficient equity to finance its own activities, and, therefore, is no longer considered a VIE as of December 31, 2017. Duke Energy's investment in DATC was $46 million at December 31, 2017. December 31, 2016 Duke Energy Duke Duke Pipeline Commercial Energy Energy (in millions) Investments Renewables Other Total Ohio Indiana Piedmont (a) Receivables from affiliated companies $ — $ — $ — $ — $ 82 $ 101 $ — Investments in equity method unconsolidated affiliates 487 174 90 751 — — 139 Other noncurrent assets 12 — — 12 — — — Total assets $ 499 $ 174 $ 90 $ 763 $ 82 $ 101 $ 139 Other current liabilities — — 3 3 — — — Other noncurrent liabilities — — 13 13 — — 4 Total liabilities $ — $ — $ 16 $ 16 $ — $ — $ 4 Net assets $ 499 $ 174 $ 74 $ 747 $ 82 $ 101 $ 135 (a) In April 2017, Piedmont transferred its non-consolidated VIE investments to a wholly owned subsidiary of Duke Energy. See Note 12 and the "Pipeline Investments" section below for additional detail.
DEFPF [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Schedule Of Variable Interest Entities	The following table summarizes the impact of DEFPF on Duke Energy Florida's Consolidated Balance Sheets. (in millions) December 31, 2017 December 31, 2016 Receivables of VIEs $ 4 $ 6 Regulatory Assets: Current 51 50 Current Assets: Other 40 53 Other Noncurrent Assets: Regulatory assets 1,091 1,142 Current Liabilities: Other 10 17 Current maturities of long-term debt 53 62 Long-Term Debt 1,164 1,217
Commercial Renewables [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Schedule Of Variable Interest Entities	Duke Energy consolidates the entities as it is responsible for all of these decisions. The table below presents material balances reported on Duke Energy's Consolidated Balance Sheets related to renewables VIEs. (in millions) December 31, 2017 December 31, 2016 Current Assets: Other $ 174 $ 223 Property, plant and equipment, cost 3,923 3,419 Accumulated depreciation and amortization (591 ) (453 ) Current maturities of long-term debt 170 198 Long-Term Debt 1,700 1,097 Other Noncurrent Liabilities: Deferred income taxes (148 ) 275 Other Noncurrent Liabilities: Other 241 252
Pipeline Investments [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Schedule Of Variable Interest Entities	The table below presents Duke Energy's ownership interest and investment balance in in these joint ventures. Investment Amount (in millions) Ownership December 31, December 31, Entity Name Interest 2017 2016 ACP 47 % $ 397 $ 265 Sabal Trail 7.5 % 219 140 Constitution 24 % 81 82 Total $ 697 $ 487
Cinergy Receivables [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Schedule Of Variable Interest Entities	Key assumptions used in estimating fair value are detailed in the following table. Duke Energy Ohio Duke Energy Indiana 2017 2016 2017 2016 Anticipated credit loss ratio 0.5 % 0.5 % 0.3 % 0.3 % Discount rate 2.1 % 1.5 % 2.1 % 1.5 % Receivable turnover rate 13.5 % 13.3 % 10.7 % 10.6 % The following table shows the gross and net receivables sold. Duke Energy Ohio Duke Energy Indiana (in millions) 2017 2016 2017 2016 Receivables sold $ 273 $ 267 $ 312 $ 306 Less: Retained interests 87 82 106 101 Net receivables sold $ 186 $ 185 $ 206 $ 205 The following table shows sales and cash flows related to receivables sold. Duke Energy Ohio Duke Energy Indiana Years Ended December 31, Years Ended December 31, (in millions) 2017 2016 2015 2017 2016 2015 Sales Receivables sold $ 1,879 $ 1,926 $ 1,963 $ 2,711 $ 2,635 $ 2,627 Loss recognized on sale 10 9 9 12 11 11 Cash Flows Cash proceeds from receivables sold 1,865 1,882 1,995 2,694 2,583 2,670 Collection fees received 1 1 1 1 1 1 Return received on retained interests 3 2 3 7 5 5

Common Stock (Tables)

Common Stock (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Schedule Of Earnings Per Share	The following table presents Duke Energy’s basic and diluted EPS calculations and reconciles the weighted average number of common stock outstanding to the diluted weighted average number of common stock outstanding. Years Ended December 31, (in millions, except per share amounts) 2017 2016 2015 Income from continuing operations attributable to Duke Energy common stockholders excluding impact of participating securities $ 3,059 $ 2,567 $ 2,640 Weighted average shares outstanding – basic 700 691 694 Weighted average shares outstanding – diluted 700 691 694 Earnings per share from continuing operations attributable to Duke Energy common stockholders Basic $ 4.37 $ 3.71 $ 3.80 Diluted $ 4.37 $ 3.71 $ 3.80 Potentially dilutive items excluded from the calculation (a) 2 2 2 Dividends declared per common share $ 3.49 $ 3.36 $ 3.24 (a) Performance stock awards were not included in the dilutive securities calculation because the performance measures related to the awards had not been met.

Severance (Tables)

Severance (Tables)	12 Months Ended
	Dec. 31, 2017
Restructuring Cost and Reserve [Line Items]
Schedule of Severance Expense	The following table presents the direct and allocated severance and related expenses recorded by the Duke Energy Registrants. Amounts are included within Operation, maintenance and other on the Consolidated Statements of Operations. Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont (a) Year Ended December 31, 2017 $ 15 $ 2 $ 2 $ 1 $ 1 $ — $ 1 $ 9 Year Ended December 31, 2016 118 39 40 23 17 3 7 Year Ended December 31, 2015 142 93 36 28 8 2 6 (a) Piedmont severance benefit costs were $3 million for the two months ended December 31, 2016, and $19 million for the year ended October 31, 2016. Piedmont did not record any severance benefit costs for the year ended October 31, 2015.
Schedule of Severance Liability	The table below presents the severance liability for past and ongoing severance plans including the plans described above. Amounts for Duke Energy Indiana and Duke Energy Ohio are not material. Duke Duke Duke Duke Energy Progress Energy Energy (in millions) Energy Carolinas Energy Progress Florida Piedmont Balance at December 31, 2016 $ 79 $ 13 $ 14 $ 6 $ 8 $ 20 Provision/Adjustments 17 2 — — — 9 Cash Reductions (77 ) (10 ) (12 ) (5 ) (8 ) (24 ) Balance at December 31, 2017 $ 19 $ 5 $ 2 $ 1 $ — $ 5

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule Of Total Stock-Based Compensation Expense, net of tax	The following table summarizes the total expense recognized by the Duke Energy Registrants, net of tax, for stock-based compensation. Years Ended December 31, (in millions) 2017 2016 2015 Duke Energy $ 43 $ 35 $ 38 Duke Energy Carolinas 15 12 14 Progress Energy 16 12 14 Duke Energy Progress 10 7 9 Duke Energy Florida 6 5 5 Duke Energy Ohio 3 2 2 Duke Energy Indiana 4 3 4 Piedmont (a) 3 (a) See discussion below for information on Piedmont's pre-merger stock-based compensation plans.
Schedule Of Stock-Based Compensation Expense	Duke Energy's pretax stock-based compensation costs, the tax benefit associated with stock-based compensation expense and stock-based compensation costs capitalized are included in the following table. Years Ended December 31, (in millions) 2017 2016 2015 Restricted stock unit awards $ 41 $ 36 $ 38 Performance awards 27 19 23 Pretax stock-based compensation cost $ 68 $ 55 $ 61 Tax benefit associated with stock-based compensation expense $ 25 $ 20 $ 23 Stock-based compensation costs capitalized 4 2 3
Schedule of Share-based Compensation, Restricted Stock Units Award Activity	The following table includes information related to restricted stock unit awards. Years Ended December 31, 2017 2016 2015 Shares awarded (in thousands) 583 684 524 Fair value (in millions) $ 47 $ 52 $ 41 The following table summarizes information about restricted stock unit awards outstanding. Weighted Average Shares Grant Date Fair Value (in thousands) (per share) Outstanding at December 31, 2016 1,139 $ 76 Granted 583 80 Vested (553 ) 76 Forfeited (48 ) 78 Outstanding at December 31, 2017 1,121 78 Restricted stock unit awards expected to vest 1,094 78
Schedule of Performance Awards	The following table includes information related to stock-based performance awards. Years Ended December 31, 2017 2016 2015 Shares granted assuming target performance (in thousands) 461 338 321 Fair value (in millions) $ 37 $ 25 $ 26
Schedule of Nonvested Performance-based Units Activity	The following table summarizes information about stock-based performance awards outstanding and assumes payout at the target level. Weighted Average Shares Grant Date Fair Value (in thousands) (per share) Outstanding at December 31, 2016 862 $ 75 Granted 461 81 Forfeited (258 ) 69 Outstanding at December 31, 2017 1,065 79 Stock-based performance awards expected to vest 1,034 79
Schedule of Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Exercises	The following table summarizes additional information related to stock options exercised and granted. Years Ended December 31, (in millions) 2016 2015 Intrinsic value of options exercised $ 1 $ 5 Tax benefit related to options exercised — 2 Cash received from options exercised 7 17
Piedmont Natural Gas [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule Of Stock-Based Compensation Expense	Piedmont's stock-based compensation costs and the tax benefit associated with stock-based compensation expense are included in the following table. Piedmont's stock-based compensation costs were not material for the two months ended December 31, 2016. Years Ended October 31, (in millions) 2016 2015 Pretax stock-based compensation cost $ 16 $ 14 Tax benefit associated with stock-based compensation expense 6 4 Net of tax stock-based compensation cost $ 10 $ 10

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Pension Plan Contributions	Duke Energy’s policy is to fund amounts on an actuarial basis to provide assets sufficient to meet benefit payments to be paid to plan participants. The following table includes information related to the Duke Energy Registrants’ contributions to its qualified defined benefit pension plans. Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont (a) Anticipated Contributions: Total anticipated 2018 contributions $ 148 $ 46 $ 45 $ 25 $ 20 $ — $ 8 $ 7 Contributions made January 2, 2018 141 46 45 25 20 — 8 — Contributions to be made in 2018 $ 7 $ — $ — $ — $ — $ — $ — $ 7 Contributions Made: 2017 $ 19 $ — $ — $ — $ — $ 4 $ — $ 11 2016 155 43 43 24 20 5 9 2015 302 91 83 42 40 8 19 (a) Piedmont contributed $10 million to its U.S. qualified defined benefit pension plan during the two months ended December 31, 2016, and for each of the years ended October 31, 2016, and 2015, respectively.
Fair Value and Allocation of Plan Assets	The following table presents target and actual asset allocations for the VEBA trusts at December 31, 2017 . Actual Allocation at Target December 31, Allocation 2017 2016 U.S. equity securities 32 % 41 % 39 % Non-US equity securities 6 % 8 % — % Real estate 2 % 2 % 2 % Debt securities 45 % 36 % 37 % Cash 15 % 13 % 22 % Total 100 % 100 % 100 % The following table includes the target asset allocations by asset class at December 31, 2017 , and the actual asset allocations for the Duke Energy Master Retirement Trust. Actual Allocation at Target December 31, Allocation 2017 2016 (a) U.S. equity securities 10 % 11 % 11 % Non-U.S. equity securities 8 % 8 % 8 % Global equity securities 10 % 10 % 10 % Global private equity securities 3 % 2 % 2 % Debt securities 63 % 63 % 63 % Hedge funds 2 % 2 % 2 % Real estate and cash 2 % 2 % 2 % Other global securities 2 % 2 % 2 % Total 100 % 100 % 100 % (a) Excludes Piedmont Pension Assets , which had a targeted asset allocation of 60 percent return-seeking and 40 percent liability hedging fixed-income. Actual asset allocations were 61 percent return-seeking and 39 percent liability hedging fixed-income at December 31, 2016. The following tables provide the fair value measurement amounts for VEBA trust assets. December 31, 2017 Total Fair (in millions) Value Level 2 Cash and cash equivalents $ 8 $ 8 Real estate 1 1 Equity securities 28 28 Debt securities 21 21 Total assets $ 58 $ 58 December 31, 2016 Total Fair (in millions) Value Level 2 Cash and cash equivalents $ 14 $ 14 Real estate 1 1 Equity securities 26 26 Debt securities 25 25 Total assets $ 66 $ 66 The following tables provide the fair value measurement amounts for the Duke Energy Master Retirement Trust qualified pension and other post-retirement assets. December 31, 2017 Total Fair Not (in millions) Value Level 1 Level 2 Level 3 Categorized (b) Equity securities $ 2,823 $ 1,976 $ — $ — 847 Corporate debt securities 4,694 — 4,694 — — Short-term investment funds 246 192 54 — — Partnership interests 137 — — — 137 Hedge funds 226 — — — 226 Real estate limited partnerships 135 — — — 135 U.S. government securities 762 — 762 — — Guaranteed investment contracts 28 — — 28 — Governments bonds – foreign 38 — 38 — — Cash 6 6 — — — Government and commercial mortgage backed securities 2 — 2 — — Net pending transactions and other investments 17 15 2 — — Total assets (a) $ 9,114 $ 2,189 $ 5,552 $ 28 $ 1,345 (a) Duke Energy Carolinas, Progress Energy, Duke Energy Progress, Duke Energy Florida, Duke Energy Ohio, Duke Energy Indiana, and Piedmont were allocated approximately 27 percent , 30 percent , 15 percent , 15 percent , 5 percent , 8 percent , and 4 percent , respectively, of the Duke Energy Master Retirement Trust at December 31, 2017 . Accordingly, all amounts included in the table above are allocable to the Subsidiary Registrants using these percentages. (b) Certain investments that are measured at fair value using the net asset value per share practical expedient have not been categorized in the fair value hierarchy. December 31, 2016 Total Fair Not (in millions) Value Level 1 Level 2 Level 3 Categorized (b) Equity securities $ 2,472 $ 1,677 $ 27 $ 9 759 Corporate debt securities 4,330 8 4,322 — — Short-term investment funds 476 211 265 — — Partnership interests 157 — — — 157 Hedge funds 232 — — — 232 Real estate limited partnerships 144 17 — — 127 U.S. government securities 734 — 734 — — Guaranteed investment contracts 29 — — 29 — Governments bonds – foreign 32 — 32 — — Cash 17 15 2 — — Net pending transactions and other investments 32 1 6 — 25 Total assets (a) $ 8,655 $ 1,929 $ 5,388 $ 38 $ 1,300 (a) Duke Energy Carolinas, Progress Energy, Duke Energy Progress, Duke Energy Florida, Duke Energy Ohio and Duke Energy Indiana were allocated approximately 27 percent , 30 percent , 15 percent , 15 percent , 5 percent and 8 percent , respectively, of the Duke Energy Master Retirement Trust and Piedmont's Pension assets at December 31, 2016 . Accordingly, all amounts included in the table above are allocable to the Subsidiary Registrants using these percentages. (b) Certain investments that are measured at fair value using the net asset value per share practical expedient have not been categorized in the fair value hierarchy.
Master Trust Level 3 Rollforward	The following table provides a reconciliation of beginning and ending balances of Duke Energy Master Retirement Trust qualified pension and other post-retirement assets and Piedmont Pension Assets at fair value on a recurring basis where the determination of fair value includes significant unobservable inputs (Level 3). (in millions) 2017 2016 Balance at January 1 $ 38 $ 31 Combination of Piedmont Pension Assets — 9 Sales (2 ) (2 ) Total gains (losses) and other, net 1 — Transfer of Level 3 assets to other classifications (9 ) — Balance at December 31 $ 28 $ 38
Employee Savings Plan Matching Contributions	The following table includes pretax employer matching contributions made by Duke Energy and expensed by the Subsidiary Registrants. Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont (a) Years ended December 31, 2017 $ 179 $ 61 $ 53 $ 37 $ 16 $ 3 $ 9 $ 7 2016 169 57 50 35 15 3 8 — 2015 159 54 48 34 13 3 7 — (a) Piedmont's pretax employer matching contributions were $1 million , $7 million and $7 million during the two months ended December 31, 2016 and for the years ended October 31, 2016 and 2015, respectively.
Pension Plan [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Components of Net Periodic Pension Costs	Components of Net Periodic Pension Costs Year Ended December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Service cost $ 159 $ 48 $ 45 $ 26 $ 19 $ 4 $ 9 $ 10 Interest cost on projected benefit obligation 328 79 100 47 53 18 26 14 Expected return on plan assets (545 ) (142 ) (167 ) (82 ) (85 ) (27 ) (42 ) (24 ) Amortization of actuarial loss 146 31 52 23 29 5 12 11 Amortization of prior service credit (24 ) (8 ) (3 ) (2 ) (1 ) (1 ) (2 ) (2 ) Settlement charge 12 — — — — — — 12 Other 8 2 2 1 1 — 1 1 Net periodic pension costs (a)(b) $ 84 $ 10 $ 29 $ 13 $ 16 $ (1 ) $ 4 $ 22 Year Ended December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Service cost $ 147 $ 48 $ 42 $ 24 $ 19 $ 4 $ 9 Interest cost on projected benefit obligation 335 86 106 49 55 19 28 Expected return on plan assets (519 ) (142 ) (168 ) (82 ) (84 ) (27 ) (42 ) Amortization of actuarial loss 134 33 51 23 29 4 11 Amortization of prior service (credit) (17 ) (8 ) (3 ) (2 ) (1 ) — (1 ) Settlement charge 3 — — — — — — Other 8 2 3 1 1 1 1 Net periodic pension costs (a)(b) $ 91 $ 19 $ 31 $ 13 $ 19 $ 1 $ 6 Year Ended December 31, 2015 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Service cost $ 159 $ 50 $ 44 $ 23 $ 20 $ 4 $ 10 Interest cost on projected benefit obligation 324 83 104 48 54 18 27 Expected return on plan assets (516 ) (139 ) (171 ) (79 ) (87 ) (26 ) (42 ) Amortization of actuarial loss 166 39 65 33 31 7 13 Amortization of prior service (credit) cost (15 ) (7 ) (3 ) (2 ) (1 ) — 1 Other 8 2 3 1 1 — 1 Net periodic pension costs (a)(b) $ 126 $ 28 $ 42 $ 24 $ 18 $ 3 $ 10 (a) Duke Energy amounts exclude $7 million , $8 million and $9 million for the years ended December 2017 , 2016 and 2015 , respectively, of regulatory asset amortization resulting from purchase accounting adjustments associated with Duke Energy's merger with Cinergy in April 2006. (b) Duke Energy Ohio amounts exclude $3 million , $4 million and $4 million for the years ended December 2017 , 2016 and 2015 , respectively, of regulatory asset amortization resulting from purchase accounting adjustments associated with Duke Energy's merger with Cinergy in April 2006.
Amounts Recognized in AOCI and Regulatory Assets and Liabilities	Amounts Recognized in Accumulated Other Comprehensive Income and Regulatory Assets Year Ended December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Regulatory assets, net (decrease) increase $ (212 ) $ (70 ) $ (49 ) $ (37 ) $ (11 ) $ 9 $ (19 ) $ (64 ) Accumulated other comprehensive loss (income) Deferred income tax expense $ — — 3 — — — — — Prior year service cost arising during the year 1 — — — — — — — Amortization of prior year actuarial losses (7 ) — (7 ) — — — — — Net amount recognized in accumulated other comprehensive income $ (6 ) $ — $ (4 ) $ — $ — $ — $ — $ — Year Ended December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Regulatory assets, net increase $ 214 $ 4 $ 34 $ 18 $ 16 $ 2 $ 9 Accumulated other comprehensive (income) loss Deferred income tax expense $ 4 $ — $ — $ — $ — $ — $ — Prior year service credit arising during the year (2 ) — — — — — — Amortization of prior year actuarial losses (7 ) — (1 ) — — — — Net amount recognized in accumulated other comprehensive income $ (5 ) $ — $ (1 ) $ — $ — $ — $ — Piedmont's regulatory asset net increase was $34 million , $35 million and $20 million for the two months ended December 31, 2016, and for the years ended October 31, 2016, and 2015, respectively.
Reconciliation of Funded Status to Net Amount Recognized	Reconciliation of Funded Status to Net Amount Recognized Year Ended December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Change in Projected Benefit Obligation Obligation at prior measurement date $ 8,131 $ 1,952 $ 2,512 $ 1,158 $ 1,323 $ 447 $ 658 $ 344 Service cost 159 48 45 26 19 4 9 10 Interest cost 328 79 100 47 53 18 26 14 Actuarial loss 455 68 158 57 99 35 26 38 Transfers — 27 (32 ) (2 ) (15 ) 12 — — Plan amendments (61 ) — — — — — (61 ) Benefits paid (537 ) (145 ) (146 ) (75 ) (69 ) (37 ) (50 ) (5 ) Benefits paid - settlements (27 ) — — — — — — (27 ) Obligation at measurement date $ 8,448 $ 2,029 $ 2,637 $ 1,211 $ 1,410 $ 479 $ 669 $ 313 Accumulated Benefit Obligation at measurement date $ 8,369 $ 2,029 $ 2,601 $ 1,211 $ 1,375 $ 468 $ 652 $ 313 Change in Fair Value of Plan Assets Plan assets at prior measurement date $ 8,531 $ 2,225 $ 2,675 $ 1,290 $ 1,352 $ 428 $ 657 $ 346 Employer contributions 19 — — — — 4 — 11 Actual return on plan assets 1,017 265 317 153 161 51 77 43 Benefits paid (537 ) (145 ) (146 ) (75 ) (69 ) (37 ) (50 ) (5 ) Benefits paid - settlements (27 ) — — — — — — (27 ) Transfers — 27 (32 ) (2 ) (15 ) 12 — — Plan assets at measurement date $ 9,003 $ 2,372 $ 2,814 $ 1,366 $ 1,429 $ 458 $ 684 $ 368 Funded status of plan $ 555 $ 343 $ 177 $ 155 $ 19 $ (21 ) $ 15 $ 55 Year Ended December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Change in Projected Benefit Obligation Obligation at prior measurement date $ 7,727 $ 1,995 $ 2,451 $ 1,143 $ 1,276 $ 453 $ 649 Obligation assumed from acquisition 352 — — — — — — Service cost 147 48 42 24 19 4 9 Interest cost 335 86 106 49 55 19 28 Actuarial loss 307 46 111 52 57 13 41 Transfers — 14 (3 ) (3 ) — (3 ) — Plan amendments (52 ) (3 ) — — — (3 ) (15 ) Benefits paid (679 ) (234 ) (195 ) (107 ) (84 ) (36 ) (54 ) Impact of settlements (6 ) — — — — — — Obligation at measurement date $ 8,131 $ 1,952 $ 2,512 $ 1,158 $ 1,323 $ 447 $ 658 Accumulated Benefit Obligation at measurement date $ 8,006 $ 1,952 $ 2,479 $ 1,158 $ 1,290 $ 436 $ 649 Change in Fair Value of Plan Assets Plan assets at prior measurement date $ 8,136 $ 2,243 $ 2,640 $ 1,284 $ 1,321 $ 433 $ 655 Assets received from acquisition 343 — — — — — — Employer contributions 155 43 43 24 20 5 9 Actual return on plan assets 582 159 190 92 95 29 47 Benefits paid (679 ) (234 ) (195 ) (107 ) (84 ) (36 ) (54 ) Impact of settlements (6 ) — — — — — — Transfers — 14 (3 ) (3 ) — (3 ) — Plan assets at measurement date $ 8,531 $ 2,225 $ 2,675 $ 1,290 $ 1,352 $ 428 $ 657 Funded status of plan $ 400 $ 273 $ 163 $ 132 $ 29 $ (19 ) $ (1 )
Amounts Recognized in the Consolidated Balance Sheet	Amounts Recognized in the Consolidated Balance Sheets December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Prefunded pension (a) $ 680 $ 343 $ 245 $ 155 $ 87 $ 8 $ 16 $ 55 Noncurrent pension liability (b) $ 125 $ — $ 68 $ — $ 68 $ 29 $ 1 $ — Net asset (liability) recognized $ 555 $ 343 $ 177 $ 155 $ 19 $ (21 ) $ 15 $ 55 Regulatory assets $ 1,886 $ 406 $ 756 $ 341 $ 415 $ 90 $ 152 $ 73 Accumulated other comprehensive (income) loss Deferred income tax benefit $ (41 ) $ — $ (3 ) $ — $ — $ — $ — $ — Prior service credit (5 ) — — — — — — — Net actuarial loss 116 — 9 — — — — — Net amounts recognized in accumulated other comprehensive loss $ 70 $ — $ 6 $ — $ — $ — $ — $ — Amounts to be recognized in net periodic pension costs in the next year Unrecognized net actuarial loss $ 132 $ 29 $ 44 $ 21 $ 23 $ 5 $ 7 $ 11 Unrecognized prior service credit (32 ) (8 ) (3 ) (2 ) (1 ) — (2 ) (9 ) December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Prefunded pension (a) $ 518 $ 273 $ 225 $ 132 $ 91 $ 6 $ — 3 Noncurrent pension liability (b) $ 118 $ — $ 62 $ — $ 62 $ 25 $ 1 — Net asset recognized $ 400 $ 273 $ 163 $ 132 $ 29 $ (19 ) $ (1 ) $ 3 Regulatory assets $ 2,098 $ 476 $ 805 $ 378 $ 426 $ 81 $ 171 $ 137 Accumulated other comprehensive (income) loss Deferred income tax benefit $ (41 ) $ — $ (6 ) $ — $ — $ — $ — $ — Prior service credit (6 ) — — — — — — — Net actuarial loss 123 — 16 — — — — — Net amounts recognized in accumulated other comprehensive loss $ 76 $ — $ 10 $ — $ — $ — $ — $ — Amounts to be recognized in net periodic pension costs in the next year Unrecognized net actuarial loss $ 147 $ 31 $ 52 $ 23 $ 29 $ 5 $ 8 $ 13 Unrecognized prior service credit $ (24 ) $ (8 ) $ (3 ) $ (2 ) $ (1 ) $ — $ (2 ) $ (2 ) (a) Included in Other within Other Noncurrent Assets on the Consolidated Balance Sheets. (b) Included in Accrued pension and other post-retirement benefit costs on the Consolidated Balance Sheets.
Information for Plans with Accumulated Benefit Obligation in Excess of Plan Assets	Information for Plans with Accumulated Benefit Obligation in Excess of Plan Assets December 31, 2017 Duke Duke Duke Progress Energy Energy (in millions) Energy Energy Florida Ohio Projected benefit obligation $ 1,386 $ 718 $ 718 $ 337 Accumulated benefit obligation 1,326 683 683 326 Fair value of plan assets 1,260 650 650 308 December 31, 2016 Duke Duke Duke Progress Energy Energy (in millions) Energy Energy Florida Ohio Projected benefit obligation $ 1,299 $ 665 $ 665 $ 311 Accumulated benefit obligation 1,239 633 633 299 Fair value of plan assets 1,182 604 604 286
Assumptions Used for Pension Benefits Accounting	The following tables present the assumptions or range of assumptions used for pension benefit accounting. December 31, 2017 2016 2015 Benefit Obligations Discount rate 3.60% 4.10% 4.40% Salary increase 3.50 % – 4.00% 4.00 % – 4.50% 4.00 % – 4.40% Net Periodic Benefit Cost Discount rate 4.10% 4.40% 4.10% Salary increase 4.00 % – 4.50% 4.00 % – 4.40% 4.00 % – 4.40% Expected long-term rate of return on plan assets 6.50 % – 6.75% 6.50 % – 6.75% 6.50%
Expected Benefit Payments	Expected Benefit Payments Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Years ending December 31, 2018 $ 642 $ 185 $ 161 $ 85 $ 75 $ 36 $ 47 $ 29 2019 644 185 164 86 77 36 46 26 2020 661 195 172 90 80 36 44 24 2021 666 194 175 93 81 37 44 24 2022 672 197 176 92 83 36 44 23 2023-2027 3,099 865 888 449 435 166 210 103
Pension Plan [Member] | Nonqualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Components of Net Periodic Pension Costs	Components of Net Periodic Pension Costs Year Ended December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Service cost $ 2 $ 1 $ — $ — $ — $ — $ — $ — Interest cost on projected benefit obligation 13 1 5 1 2 — — — Amortization of actuarial loss 8 — 2 1 1 — — — Amortization of prior service credit (2 ) — — — — — — — Net periodic pension costs $ 21 $ 2 $ 7 $ 2 $ 3 $ — $ — $ — Year Ended December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Service cost $ 2 $ — $ — $ — $ — $ — $ — Interest cost on projected benefit obligation 14 1 5 1 2 — — Amortization of actuarial loss 8 1 1 1 1 — — Amortization of prior service credit (1 ) — — — — — — Net periodic pension costs $ 23 $ 2 $ 6 $ 2 $ 3 $ — $ — Year Ended December 31, 2015 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Service cost $ 3 $ — $ 1 $ — $ — $ — $ — Interest cost on projected benefit obligation 13 1 4 1 2 — — Amortization of actuarial loss 6 — 2 1 2 — 1 Amortization of prior service credit (1 ) — (1 ) — — — — Net periodic pension costs $ 21 $ 1 $ 6 $ 2 $ 4 $ — $ 1
Amounts Recognized in AOCI and Regulatory Assets and Liabilities	Amounts Recognized in Accumulated Other Comprehensive Income and Regulatory Assets and Liabilities Year Ended December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Regulatory assets, net (decrease) increase $ 5 $ (1 ) $ 3 $ 1 $ 2 $ — $ — $ — Accumulated other comprehensive (income) loss Deferred income tax benefit $ (1 ) $ — $ — $ — $ — $ — $ — $ — Actuarial loss arising during the year 2 — — — — — — — Net amount recognized in accumulated other comprehensive loss (income) $ 1 $ — $ — $ — $ — $ — $ — $ — Year Ended December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Regulatory assets, net (decrease) increase $ (3 ) $ (2 ) $ 2 $ 1 $ 1 $ — $ (1 ) Accumulated other comprehensive (income) loss Prior service credit arising during the year $ (1 ) $ — $ — $ — $ — $ — $ — Actuarial gains arising during the year 1 — — — — — — Net amount recognized in accumulated other comprehensive loss (income) $ — $ — $ — $ — $ — $ — $ —
Reconciliation of Funded Status to Net Amount Recognized	Reconciliation of Funded Status to Net Amount Recognized Year Ended December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Change in Projected Benefit Obligation Obligation at prior measurement date $ 332 $ 14 $ 114 $ 33 $ 46 $ 4 $ 3 $ 4 Service cost 2 1 — — — — — — Interest cost 13 1 5 1 2 — — — Actuarial losses (gains) 15 — 5 4 2 — — — Benefits paid (31 ) (2 ) (8 ) (3 ) (3 ) — — — Obligation at measurement date $ 331 $ 14 $ 116 $ 35 $ 47 $ 4 $ 3 $ 4 Accumulated Benefit Obligation at measurement date $ 331 $ 14 $ 116 $ 35 $ 47 $ 4 $ 3 $ 4 Change in Fair Value of Plan Assets Benefits paid $ (31 ) $ (2 ) $ (8 ) $ (3 ) $ (3 ) $ — $ — $ — Employer contributions 31 2 8 3 3 — — — Plan assets at measurement date $ — $ — $ — $ — $ — $ — $ — $ — Year Ended December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Change in Projected Benefit Obligation Obligation at prior measurement date $ 341 $ 16 $ 112 $ 33 $ 46 $ 4 $ 5 Obligation assumed from acquisition 5 — — — — — — Service cost 2 — — — — — — Interest cost 14 1 5 1 2 — — Actuarial losses (gains) 4 (1 ) 5 2 1 — (2 ) Plan amendments (2 ) — — — — — Benefits paid (32 ) (2 ) (8 ) (3 ) (3 ) — — Obligation at measurement date $ 332 $ 14 $ 114 $ 33 $ 46 $ 4 $ 3 Accumulated Benefit Obligation at measurement date $ 332 $ 14 $ 114 $ 33 $ 46 $ 4 $ 3 Change in Fair Value of Plan Assets Benefits paid $ (32 ) $ (2 ) $ (8 ) $ (3 ) $ (3 ) — — Employer contributions 32 2 8 3 3 — — Plan assets at measurement date $ — $ — $ — $ — $ — $ — $ —
Amounts Recognized in the Consolidated Balance Sheet	Amounts Recognized in the Consolidated Balance Sheets December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Current pension liability (a) $ 23 $ 2 $ 8 $ 3 $ 3 $ — $ — $ — Noncurrent pension liability (b) 308 12 108 32 44 4 3 4 Total accrued pension liability $ 331 $ 14 $ 116 $ 35 $ 47 $ 4 $ 3 $ 4 Regulatory assets $ 78 $ 4 $ 21 $ 8 $ 13 $ 1 $ — $ 1 Accumulated other comprehensive (income) loss Deferred income tax benefit $ (4 ) $ — $ (3 ) $ — $ — $ — $ — $ — Prior service credit (1 ) — — — — — — — Net actuarial loss 12 — 9 — — — — — Net amounts recognized in accumulated other comprehensive loss $ 7 $ — $ 6 $ — $ — $ — $ — $ — Amounts to be recognized in net periodic pension expense in the next year Unrecognized net actuarial loss $ 8 $ — $ 2 $ 1 $ 1 $ — $ — $ — Unrecognized prior service credit (2 ) — — — — — — — December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Current pension liability (a) $ 28 $ 2 $ 8 $ 2 $ 3 $ — $ — $ — Noncurrent pension liability (b) 304 12 106 31 43 4 3 4 Total accrued pension liability $ 332 $ 14 $ 114 $ 33 $ 46 $ 4 $ 3 $ 4 Regulatory assets $ 73 $ 5 $ 18 $ 7 $ 11 $ 1 $ — $ 1 Accumulated other comprehensive (income) loss Deferred income tax benefit $ (3 ) $ — $ (3 ) $ — $ — $ — $ — $ — Prior service credit (1 ) — — — — — — — Net actuarial loss 10 — 9 — — — — — Net amounts recognized in accumulated other comprehensive loss $ 6 $ — $ 6 $ — $ — $ — $ — $ — Amounts to be recognized in net periodic pension expense in the next year Unrecognized net actuarial loss $ 7 $ — $ 2 $ 1 $ 1 $ — $ — $ — Unrecognized prior service credit $ (2 ) $ — $ — $ — $ — $ — $ — $ — (a) Included in Other within Current Liabilities on the Consolidated Balance Sheets. (b) Included in Accrued pension and other post-retirement benefit costs on the Consolidated Balance Sheets.
Information for Plans with Accumulated Benefit Obligation in Excess of Plan Assets	Information for Plans with Accumulated Benefit Obligation in Excess of Plan Assets December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Projected benefit obligation $ 331 $ 14 $ 116 $ 35 $ 47 $ 4 $ 3 $ 4 Accumulated benefit obligation 331 14 116 35 47 4 3 4 December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Projected benefit obligation $ 332 $ 14 $ 114 $ 33 $ 46 $ 4 $ 3 $ 4 Accumulated benefit obligation 332 14 114 33 46 4 3 4
Assumptions Used for Pension Benefits Accounting	The following tables present the assumptions used for pension benefit accounting. December 31, 2017 2016 2015 Benefit Obligations Discount rate 3.60 % 4.10 % 4.40 % Salary increase 3.50 % – 4.00 % 4.40 % 4.40 % Net Periodic Benefit Cost Discount rate 4.10 % 4.40 % 4.10 % Salary increase 4.40 % 4.40 % 4.40 %
Expected Benefit Payments	Expected Benefit Payments Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Years ending December 31, 2018 $ 23 $ 2 $ 8 $ 3 $ 3 $ — $ — $ — 2019 21 1 8 2 3 — — — 2020 21 1 8 2 3 — — — 2021 22 1 8 2 3 — — — 2022 25 1 8 2 3 — — — 2023-2027 117 6 36 11 15 1 1 2
Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Components of Net Periodic Pension Costs	Components of Net Periodic Other Post-Retirement Benefit Costs Year Ended December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Service cost $ 4 $ 1 $ — $ — $ — $ — $ — $ 1 Interest cost on accumulated post-retirement benefit obligation 34 8 13 7 6 1 3 1 Expected return on plan assets (14 ) (8 ) — — — — (1 ) (2 ) Amortization of actuarial loss (gain) 10 (2 ) 21 12 9 (2 ) (1 ) 1 Amortization of prior service credit (115 ) (10 ) (84 ) (54 ) (30 ) — (1 ) — Curtailment credit (c) $ (30 ) $ (4 ) $ (16 ) $ — $ (16 ) $ (2 ) $ (2 ) $ — Net periodic post-retirement benefit costs (a)(b) $ (111 ) $ (15 ) $ (66 ) $ (35 ) $ (31 ) $ (3 ) $ (2 ) $ 1 Year Ended December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Service cost $ 3 $ 1 $ 1 $ — $ 1 $ — $ — Interest cost on accumulated post-retirement benefit obligation 35 8 15 8 7 1 4 Expected return on plan assets (12 ) (8 ) — — — — (1 ) Amortization of actuarial loss (gain) 6 (3 ) 22 13 9 (2 ) (1 ) Amortization of prior service credit (141 ) (14 ) (103 ) (68 ) (35 ) — (1 ) Net periodic post-retirement benefit costs (a)(b) $ (109 ) $ (16 ) $ (65 ) $ (47 ) $ (18 ) $ (1 ) $ 1 Year Ended December 31, 2015 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Service cost $ 6 $ 1 $ 1 $ 1 $ 1 $ — $ 1 Interest cost on accumulated post-retirement benefit obligation 36 9 15 8 7 2 4 Expected return on plan assets (13 ) (8 ) — — — (1 ) (1 ) Amortization of actuarial loss (gain) 16 (2 ) 28 18 10 (2 ) (2 ) Amortization of prior service credit (140 ) (14 ) (102 ) (68 ) (35 ) — — Net periodic post-retirement benefit costs (a)(b) $ (95 ) $ (14 ) $ (58 ) $ (41 ) $ (17 ) $ (1 ) $ 2 (a) Duke Energy amounts exclude $7 million , $8 million and $10 million for the years ended December 2017 , 2016 and 2015 , respectively, of regulatory asset amortization resulting from purchase accounting adjustments associated with Duke Energy's merger with Cinergy in April 2006. (b) Duke Energy Ohio amounts exclude $2 million , $2 million and $3 million for the years ended December 2017 , 2016 and 2015 , respectively, of regulatory asset amortization resulting from purchase accounting adjustments associated with Duke Energy's merger with Cinergy in April 2006. (c) Curtailment credit resulted from a reduction in average future service of plan participants due to a plan amendment.
Amounts Recognized in AOCI and Regulatory Assets and Liabilities	Amounts Recognized in Accumulated Other Comprehensive Income and Regulatory Assets and Liabilities Year Ended December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Regulatory assets, net increase (decrease) $ 71 $ — $ 81 $ 42 $ 39 $ — $ (5 ) $ (11 ) Regulatory liabilities, net increase (decrease) $ (27 ) $ (2 ) $ — $ — $ — $ (3 ) $ (7 ) $ — Accumulated other comprehensive (income) loss Deferred income tax benefit $ (1 ) $ — $ — $ — $ — $ — $ — $ — Amortization of prior year prior service credit 3 — — — — — — — Net amount recognized in accumulated other comprehensive income $ 2 $ — $ — $ — $ — $ — $ — $ — Year Ended December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Regulatory assets, net increase (decrease) $ 53 $ — $ 47 $ 38 $ 9 $ — $ (6 ) Regulatory liabilities, net increase (decrease) $ (114 ) $ (22 ) $ (51 ) $ (25 ) $ (26 ) $ (2 ) $ (12 ) Accumulated other comprehensive (income) loss Deferred income tax benefit $ (2 ) $ — $ — $ — $ — $ — $ — Actuarial losses arising during the year 3 — — — — — — Amortization of prior year prior service credit 1 — 1 — — — — Net amount recognized in accumulated other comprehensive income $ 2 $ — $ 1 $ — $ — $ — $ — Piedmont's regulatory assets net decreased $1 million for the two months ended December 31, 2016, and increased $2 million and $1 million for the years ended October 31, 2016, and 2015, respectively.
Reconciliation of Funded Status to Net Amount Recognized	Reconciliation of Funded Status to Accrued Other Post-Retirement Benefit Costs Year Ended December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Change in Projected Benefit Obligation Accumulated post-retirement benefit obligation at prior measurement date $ 868 $ 201 $ 357 $ 191 $ 164 $ 32 $ 83 $ 39 Service cost 4 1 — — — — — 1 Interest cost 34 8 13 7 6 1 3 1 Plan participants' contributions 17 3 6 3 3 1 2 — Actuarial (gains) losses 4 (3 ) 4 1 3 — 3 1 Transfers — 2 (1 ) — (1 ) 1 — — Plan amendments (28 ) (5 ) (3 ) (1 ) (2 ) (2 ) (2 ) (9 ) Benefits paid (86 ) (18 ) (34 ) (17 ) (17 ) (3 ) (11 ) (1 ) Accumulated post-retirement benefit obligation at measurement date $ 813 $ 189 $ 342 $ 184 $ 156 $ 30 $ 78 $ 32 Change in Fair Value of Plan Assets Plan assets at prior measurement date $ 244 $ 137 $ 1 $ — $ — $ 7 $ 22 $ 29 Actual return on plan assets 25 15 1 — — 2 1 3 Benefits paid (86 ) (18 ) (34 ) (17 ) (17 ) (3 ) (11 ) (1 ) Employer contributions (reimbursements) 25 (4 ) 26 14 14 — (3 ) — Plan participants' contributions 17 3 6 3 3 1 2 — Plan assets at measurement date $ 225 $ 133 $ — $ — $ — $ 7 $ 11 $ 31 Year Ended December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Change in Projected Benefit Obligation Accumulated post-retirement benefit obligation at prior measurement date $ 828 $ 200 $ 354 $ 188 $ 164 $ 35 $ 87 Obligation assumed from acquisition 39 — — — — — — Service cost 3 1 1 — 1 — — Interest cost 35 8 15 8 7 1 4 Plan participants' contributions 19 3 7 4 3 1 2 Actuarial (gains) losses 33 5 16 8 8 — 3 Transfers — 1 — — — — — Plan amendments (1 ) — — — — (1 ) — Benefits paid (88 ) (17 ) (36 ) (17 ) (19 ) (4 ) (13 ) Accumulated post-retirement benefit obligation at measurement date $ 868 $ 201 $ 357 $ 191 $ 164 $ 32 $ 83 Change in Fair Value of Plan Assets Plan assets at prior measurement date $ 208 $ 134 $ — $ — $ 1 $ 8 $ 19 Assets received from acquisition 29 — — — — — — Actual return on plan assets 14 8 1 — — 1 2 Benefits paid (88 ) (17 ) (36 ) (17 ) (19 ) (4 ) (13 ) Employer contributions 62 9 29 13 15 1 12 Plan participants' contributions 19 3 7 4 3 1 2 Plan assets at measurement date $ 244 $ 137 $ 1 $ — $ — $ 7 $ 22
Amounts Recognized in the Consolidated Balance Sheet	Amounts Recognized in the Consolidated Balance Sheets December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Current post-retirement liability (a) $ 36 $ — $ 29 $ 15 $ 14 $ 2 $ — $ — Noncurrent post-retirement liability (b) 552 56 313 169 142 21 67 1 Total accrued post-retirement liability $ 588 $ 56 $ 342 $ 184 $ 156 $ 23 $ 67 $ 1 Regulatory assets $ 125 $ — $ 129 $ 80 $ 49 $ — $ 46 $ (4 ) Regulatory liabilities $ 147 $ 44 $ — $ — $ — $ 16 $ 64 $ — Accumulated other comprehensive (income) loss Deferred income tax expense $ 4 $ — $ — $ — $ — $ — $ — $ — Prior service credit (2 ) — — — — — — — Net actuarial gain (10 ) — — — — — — — Net amounts recognized in accumulated other comprehensive income $ (8 ) $ — $ — $ — $ — $ — $ — $ — Amounts to be recognized in net periodic pension expense in the next year Unrecognized net actuarial loss $ 5 $ 3 $ 1 $ — $ 1 $ — $ — $ — Unrecognized prior service credit (19 ) (5 ) (7 ) (1 ) (6 ) (1 ) (1 ) (2 ) December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Current post-retirement liability (a) $ 38 $ — $ 31 $ 17 $ 15 $ 2 $ — $ — Noncurrent post-retirement liability (b) 586 64 325 174 149 23 63 10 Total accrued post-retirement liability $ 624 $ 64 $ 356 $ 191 $ 164 $ 25 $ 63 $ 10 Regulatory assets $ 54 $ — $ 48 $ 38 $ 10 $ — $ 51 $ 7 Regulatory liabilities $ 174 $ 46 $ — $ — $ — $ 19 $ 71 $ — Accumulated other comprehensive (income) loss Deferred income tax expense $ 5 $ — $ — $ — $ — $ — $ — $ — Prior service credit (5 ) — — — — — — — Net actuarial gain (10 ) — — — — — — — Net amounts recognized in accumulated other comprehensive income $ (10 ) $ — $ — $ — $ — $ — $ — $ — Amounts to be recognized in net periodic pension expense in the next year Unrecognized net actuarial loss (gain) $ 10 $ (2 ) $ 21 $ 12 $ 9 $ (2 ) $ (6 ) $ — Unrecognized prior service credit (115 ) (10 ) (85 ) (55 ) (30 ) — (1 ) — (a) Included in Other within Current Liabilities on the Consolidated Balance Sheets. (b) Included in Accrued pension and other post-retirement benefit costs on the Consolidated Balance Sheets.
Assumptions Used for Pension Benefits Accounting	The following tables present the assumptions used for other post-retirement benefits accounting. December 31, 2017 2016 2015 Benefit Obligations Discount rate 3.60 % 4.10 % 4.40 % Net Periodic Benefit Cost Discount rate 4.10 % 4.40 % 4.10 % Expected long-term rate of return on plan assets 6.50 % 6.50 % 6.50 % Assumed tax rate 35 % 35 % 35 %
Assumed Health Care Cost Trend Rate	Assumed Health Care Cost Trend Rate December 31, 2017 2016 Health care cost trend rate assumed for next year 7.00 % 7.00 % Rate to which the cost trend is assumed to decline (the ultimate trend rate) 4.75 % 4.75 % Year that rate reaches ultimate trend 2024 2023
Sensitivity to Changes in Assumed Health Care Cost Trend Rates	Sensitivity to Changes in Assumed Health Care Cost Trend Rates Year Ended December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont 1-Percentage Point Increase Effect on total service and interest costs $ 1 $ — $ 1 $ 1 $ — $ — $ — $ — Effect on post-retirement benefit obligation 27 6 11 6 5 1 3 1 1-Percentage Point Decrease Effect on total service and interest costs (1 ) — — — — — — — Effect on post-retirement benefit obligation (24 ) (6 ) (10 ) (5 ) (5 ) (1 ) (2 ) (1 )
Expected Benefit Payments	Expected Benefit Payments Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Years ending December 31, 2018 $ 78 $ 17 $ 30 $ 16 $ 14 $ 3 $ 9 $ 2 2019 76 17 29 15 14 3 9 2 2020 73 17 29 15 14 3 8 2 2021 71 17 28 15 13 3 7 3 2022 68 17 27 14 13 3 7 3 2023 – 2027 290 70 117 63 54 12 29 13
Piedmont Natural Gas [Member] | Pension Plan [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Components of Net Periodic Pension Costs	Piedmont Two Months Ended Years Ended October 31, (in millions) December 31, 2016 2016 2015 Service cost $ 2 $ 11 $ 11 Interest cost on projected benefit obligation 2 9 12 Expected return on plan assets (4 ) (24 ) (24 ) Amortization of actuarial loss 2 8 9 Amortization of prior service credit (1 ) (2 ) (2 ) Settlement charge 3 — — Net periodic pension costs $ 4 $ 2 $ 6
Reconciliation of Funded Status to Net Amount Recognized	Piedmont Two Months Ended Years Ended (in millions) December 31, 2016 October 31, 2016 Change in Projected Benefit Obligation Obligation at prior measurement date $ 352 $ 312 Service cost 2 11 Interest cost 2 9 Actuarial gain (5 ) 34 Benefits paid (1 ) (14 ) Impact of settlements (6 ) — Obligation at measurement date $ 344 $ 352 Accumulated Benefit Obligation at measurement date $ 289 $ 296 Change in Fair Value of Plan Assets Plan assets at prior measurement date $ 343 $ 329 Employer contributions 10 10 Actual return on plan assets — 18 Benefits paid (1 ) (14 ) Impact of settlements (6 ) — Plan assets at measurement date $ 346 $ 343 Funded status of plan $ 2 $ (9 )
Assumptions Used for Pension Benefits Accounting	Piedmont Two Months Ended Years Ended October 31, December 31, 2016 2016 2015 Benefit Obligations Discount rate 4.10 % 3.80 % 4.34 % Salary increase 4.50 % 4.05 % 4.07 % Net Periodic Benefit Cost Discount rate 3.80 % 4.34 % 4.13 % Salary increase 4.05 % 4.07 % 3.68 % Expected long-term rate of return on plan assets 6.75 % 7.25 % 7.50 %
Piedmont Natural Gas [Member] | Pension Plan [Member] | Nonqualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Components of Net Periodic Pension Costs	Piedmont Years Ended October 31, (in millions) 2016 2015 Amortization of prior service cost $ — $ 1 Settlement charge 1 — Net periodic pension costs $ 1 $ 1
Reconciliation of Funded Status to Net Amount Recognized	Piedmont Two Months Ended Years Ended (in millions) December 31, 2016 October 31, 2016 Change in Projected Benefit Obligation Obligation at prior measurement date $ 5 $ 6 Actuarial gain (1 ) — Impact of settlements — (1 ) Obligation at measurement date $ 4 $ 5 Accumulated Benefit Obligation at measurement date $ — $ 5 Change in Fair Value of Plan Assets Plan assets at prior measurement date $ — $ 1 Impact of settlements — (1 ) Plan assets at measurement date $ — $ —
Assumptions Used for Pension Benefits Accounting	Piedmont Two Months Ended Years Ended October 31, December 31, 2016 2016 2015 Benefit Obligations Discount rate 4.10 % 3.80 % 3.85 % Net Periodic Benefit Cost Discount rate 3.80 % 3.85 % 3.69 %
Piedmont Natural Gas [Member] | Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Components of Net Periodic Pension Costs	Piedmont Years Ended October 31, (in millions) 2016 2015 Service cost $ 1 $ 1 Interest cost on projected benefit obligation 1 2 Expected return on plan assets (2 ) (2 ) Amortization of actuarial loss 1 — Net periodic pension costs $ 1 $ 1
Reconciliation of Funded Status to Net Amount Recognized	Piedmont Two Months Ended Years Ended (in millions) December 31, 2016 October 31, 2016 Change in Projected Benefit Obligation Accumulated post-retirement benefit obligation at prior measurement date $ 39 $ 38 Service cost — 1 Interest cost — 1 Actuarial gain — 2 Benefits paid — (3 ) Accumulated post-retirement benefit obligation at measurement date $ 39 $ 39 Change in Fair Value of Plan Assets Plan assets at prior measurement date $ 29 $ 28 Employer contributions — 3 Actual return on plan assets — 1 Benefits paid — (3 ) Plan assets at measurement date $ 29 $ 29

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Line Items]
Schedule of Components of Income Tax Expense (Benefit)	Components of Income Tax Expense Year Ended December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Current income taxes Federal $ (247 ) $ 221 $ (436 ) $ (95 ) $ (188 ) $ (37 ) $ 128 $ (90 ) State 4 20 (5 ) 2 (11 ) 2 21 (3 ) Foreign 3 — — — — — — — Total current income taxes (240 ) 241 (441 ) (93 ) (199 ) (35 ) 149 (93 ) Deferred income taxes Federal 1,344 381 664 378 194 99 138 147 State 102 35 44 10 51 (4 ) 14 8 Total deferred income taxes (a) (b) 1,446 416 708 388 245 95 152 155 Investment tax credit amortization (10 ) (5 ) (3 ) (3 ) — (1 ) — — Income tax expense from continuing operations 1,196 652 264 292 46 59 301 62 Tax benefit from discontinued operations (6 ) — — — — — — — Total income tax expense included in Consolidated Statements of Operations $ 1,190 $ 652 $ 264 $ 292 $ 46 $ 59 $ 301 $ 62 (a) Includes utilization of NOL (Net operating loss) carryforwards and tax credit carryforwards of $428 million at Duke Energy, $74 million at Progress Energy, $36 million at Duke Energy Florida, $17 million at Duke Energy Ohio, $42 million at Duke Energy Indiana and $79 million at Piedmont. In addition the total deferred income taxes Includes benefits of NOL carryforwards and tax credit carryforwards of $10 million at Duke Energy Carolinas and $1 million at Duke Energy Progress. (b) As a result of the Tax Act, Duke Energy's deferred tax assets and liabilities were revalued as of December 31, 2017. See the Statutory Rate Reconciliation section below for additional information on the Tax Act's impact on income tax expense. Year Ended December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Current income taxes Federal $ — $ 139 $ 15 $ (59 ) $ 76 $ (7 ) $ 7 State (15 ) 25 (19 ) (25 ) 22 (13 ) 6 Foreign 2 — — — — — — Total current income taxes (13 ) 164 (4 ) (84 ) 98 (20 ) 13 Deferred income taxes Federal 1,064 430 486 350 199 88 202 State 117 45 50 40 25 11 11 Total deferred income taxes (a) 1,181 475 536 390 224 99 213 Investment tax credit amortization (12 ) (5 ) (5 ) (5 ) — (1 ) (1 ) Income tax expense from continuing operations 1,156 634 527 301 322 78 225 Tax (benefit) expense from discontinued operations (30 ) — 1 — — (36 ) — Total income tax expense included in Consolidated Statements of Operations $ 1,126 $ 634 $ 528 $ 301 $ 322 $ 42 $ 225 (a) Includes benefits of NOL carryforwards and utilization of NOL and tax credit carryforwards of $648 million at Duke Energy, $4 million at Duke Energy Carolinas, $190 million at Progress Energy, $60 million at Duke Energy Progress, $49 million at Duke Energy Florida, $26 million at Duke Energy Ohio and $58 million at Duke Energy Indiana. Year Ended December 31, 2015 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Current income taxes Federal $ — $ 216 $ (193 ) $ (56 ) $ 1 $ (18 ) $ (86 ) State (12 ) 14 1 (4 ) (7 ) (1 ) (12 ) Foreign 4 — — — — — — Total current income taxes (8 ) 230 (192 ) (60 ) (6 ) (19 ) (98 ) Deferred income taxes Federal 1,097 345 694 334 290 96 245 State 181 57 27 27 58 5 17 Total deferred income taxes (a) 1,278 402 721 361 348 101 262 Investment tax credit amortization (14 ) (5 ) (7 ) (7 ) — (1 ) (1 ) Income tax expense from continuing operations 1,256 627 522 294 342 81 163 Tax expense (benefit) from discontinued operations 89 — (1 ) — — 22 — Total income tax expense included in Consolidated Statements of Operations $ 1,345 $ 627 $ 521 $ 294 $ 342 $ 103 $ 163 (a) Includes utilization of NOL carryforwards and tax credit carryforwards of $264 million at Duke Energy, $15 million at Duke Energy Carolinas, $119 million at Progress Energy, $21 million at Duke Energy Progress, $84 million at Duke Energy Florida, $3 million at Duke Energy Ohio and $45 million at Duke Energy Indiana.
Schedule of Income before Income Tax, Domestic and Foreign	Duke Energy Income from Continuing Operations before Income Taxes Years Ended December 31, (in millions) 2017 2016 2015 Domestic (a) $ 4,207 $ 3,689 $ 3,831 Foreign 59 45 79 Income from continuing operations before income taxes $ 4,266 $ 3,734 $ 3,910 (a) Includes a $16 million expense in 2017 related to the Tax Act impact on equity earnings included within Equity in earnings (losses) of unconsolidated affiliates on the Consolidated Statement of Operations.
Summary of Effective Tax Rates	The following tables present a reconciliation of income tax expense at the U.S. federal statutory tax rate to the actual tax expense from continuing operations. Year Ended December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Income tax expense, computed at the statutory rate of 35 percent $ 1,493 $ 653 $ 536 $ 353 $ 265 $ 88 $ 229 $ 70 State income tax, net of federal income tax effect 69 36 25 8 26 (1 ) 23 3 AFUDC equity income (81 ) (37 ) (32 ) (17 ) (16 ) (4 ) (8 ) — Renewable energy production tax credits (132 ) — — — — — — — Tax Act (a) (112 ) 15 (246 ) (40 ) (226 ) (23 ) 55 (12 ) Tax true-up (52 ) (24 ) (19 ) (13 ) (7 ) (5 ) (6 ) — Other items, net 11 9 — 1 4 4 8 1 Income tax expense from continuing operations $ 1,196 $ 652 $ 264 $ 292 $ 46 $ 59 $ 301 $ 62 Effective tax rate 28.0 % 34.9 % 17.2 % 29.0 % 6.1 % 23.4 % 46.0 % 30.8 % (a) Amounts primarily include but are not limited to items that are excluded for ratemaking purposes related to abandoned or impaired assets, certain wholesale fixed rate contracts, remeasurement of nonregulated net deferred tax liabilities, Federal net operating losses, and valuation allowance on foreign tax credits. Year Ended December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Income tax expense, computed at the statutory rate of 35 percent $ 1,307 $ 630 $ 548 $ 315 $ 306 $ 95 $ 212 State income tax, net of federal income tax effect 64 46 20 10 30 (2 ) 11 AFUDC equity income (70 ) (36 ) (26 ) (17 ) (9 ) (2 ) (6 ) Renewable energy production tax credits (97 ) — — — — — — Audit adjustment 5 3 — — — — — Tax true-up (14 ) (14 ) (11 ) (3 ) (9 ) (16 ) 2 Other items, net (39 ) 5 (4 ) (4 ) 4 3 6 Income tax expense from continuing operations $ 1,156 $ 634 $ 527 $ 301 $ 322 $ 78 $ 225 Effective tax rate 31.0 % 35.2 % 33.7 % 33.4 % 36.9 % 28.9 % 37.1 % Year Ended December 31, 2015 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Income tax expense, computed at the statutory rate of 35 percent $ 1,369 $ 598 $ 555 $ 302 $ 330 $ 81 $ 168 State income tax, net of federal income tax effect 109 46 18 15 33 2 2 AFUDC equity income (58 ) (34 ) (19 ) (17 ) (3 ) (1 ) (4 ) Renewable energy production tax credits (72 ) — (1 ) — — — — Audit adjustment (22 ) — (23 ) 1 (24 ) — — Tax true-up 2 2 (3 ) (4 ) 2 (5 ) (9 ) Other items, net (72 ) 15 (5 ) (3 ) 4 4 6 Income tax expense from continuing operations $ 1,256 $ 627 $ 522 $ 294 $ 342 $ 81 $ 163 Effective tax rate 32.1 % 36.7 % 32.9 % 34.2 % 36.3 % 35.2 % 34.0 %
Schedule of Deferred Tax Assets and Liabilities	December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Deferred credits and other liabilities $ 382 $ 66 $ 126 $ 40 $ 93 $ 21 $ 4 $ 71 Capital lease obligations 60 8 — — — — 1 — Pension, post-retirement and other employee benefits 561 16 199 91 96 22 37 10 Progress Energy merger purchase accounting adjustments (a) 918 — — — — — — — Tax credits and NOL carryforwards 4,682 192 1,165 222 232 49 278 192 Investments and other assets — — — — — 3 — — Other 205 16 35 8 — 5 9 45 Valuation allowance (96 ) — (12 ) — — — — (1 ) Total deferred income tax assets 6,712 298 1,513 361 421 100 329 317 Investments and other assets (1,892 ) (1,149 ) (597 ) (313 ) (297 ) — (21 ) (21 ) Accelerated depreciation rates (14,872 ) (4,664 ) (4,490 ) (2,479 ) (2,038 ) (1,404 ) (1,938 ) (1,080 ) Regulatory assets and deferred debits, net (4,103 ) (1,029 ) (1,672 ) (892 ) (780 ) (139 ) (270 ) (147 ) Total deferred income tax liabilities (20,867 ) (6,842 ) (6,759 ) (3,684 ) (3,115 ) (1,543 ) (2,229 ) (1,248 ) Net deferred income tax liabilities $ (14,155 ) $ (6,544 ) $ (5,246 ) $ (3,323 ) $ (2,694 ) $ (1,443 ) $ (1,900 ) $ (931 ) (a) Primarily related to capital lease obligations and debt fair value adjustments. Net Deferred Income Tax Liability Components December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Deferred credits and other liabilities $ 143 $ 33 $ 78 $ 23 $ 49 $ 11 $ 6 $ (5 ) Capital lease obligations 49 14 — — — — 2 — Pension, post-retirement and other employee benefits 295 (17 ) 111 44 60 14 18 (4 ) Progress Energy merger purchase accounting adjustments (a) 536 — — — — — — — Tax credits and NOL carryforwards 4,527 234 402 156 143 25 216 70 Regulatory liabilities and deferred credits — 222 — — — 65 — 61 Investments and other assets — — — — — — 1 18 Other 73 10 1 4 — — — — Valuation allowance (519 ) — (14 ) — — — — — Total deferred income tax assets 5,104 496 578 227 252 115 243 140 Investments and other assets (1,419 ) (849 ) (470 ) (289 ) (187 ) — (14 ) — Accelerated depreciation rates (9,216 ) (3,060 ) (2,803 ) (1,583 ) (1,257 ) (896 ) (966 ) (697 ) Regulatory assets and deferred debits, net (1,090 ) — (807 ) (238 ) (569 ) — (188 ) — Other — — — — — — — (7 ) Total deferred income tax liabilities (11,725 ) (3,909 ) (4,080 ) (2,110 ) (2,013 ) (896 ) (1,168 ) (704 ) Net deferred income tax liabilities $ (6,621 ) $ (3,413 ) $ (3,502 ) $ (1,883 ) $ (1,761 ) $ (781 ) $ (925 ) $ (564 ) (a) Primarily related to capital lease obligations and debt fair value adjustments. As noted above, as a result of the Tax Act, Duke Energy revalued its existing deferred tax assets and liabilities as of December 31, 2017, to account for the estimated future impact of lower corporate tax rates on these deferred amounts. The following table shows the decrease reflected in the net deferred income tax liabilities balance above: (in millions) December 31, 2017 Duke Energy $ 8,982 Duke Energy Carolinas 3,454 Progress Energy 3,282 Duke Energy Progress 1,882 Duke Energy Florida 1,420 Duke Energy Ohio 771 Duke Energy Indiana 1,053 Piedmont 521
Summary of Tax Credit Carryforwards	The following table presents the expiration of tax credits and NOL carryforwards. December 31, 2017 (in millions) Amount Expiration Year Investment tax credits $ 1,406 2024 — 2037 Alternative minimum tax credits 1,147 Refundable by 2021 Federal NOL carryforwards 393 2022 — 2036 State NOL carryforwards and credits (a) 296 2018 — 2037 Foreign NOL carryforwards (b) 13 2027 — 2036 Foreign Tax Credits (c) 1,272 2024 — 2027 Total tax credits and NOL carryforwards 4,527 (a) A valuation allowance of $90 million has been recorded on the state NOL carryforwards, as presented in the Net Deferred Income Tax Liability Components table. (b) A valuation allowance of $13 million has been recorded on the foreign NOL carryforwards, as presented in the Net Deferred Income Tax Liability Components table. (c) A valuation allowance of $416 million has been recorded on the foreign tax credits, as presented in the Net Deferred Income Tax Liability Components table.
Schedule of Unrecognized Tax Benefits Roll Forward	The following tables present changes to unrecognized tax benefits. Year Ended December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Unrecognized tax benefits – January 1 $ 17 $ 1 $ 2 $ 2 $ 4 $ 4 $ — $ — Unrecognized tax benefits increases (decreases) Gross increases – tax positions in prior periods 12 4 3 3 1 1 1 3 Gross decreases – tax positions in prior periods (4 ) — — — — (4 ) — — Total changes 8 4 3 3 1 (3 ) 1 3 Unrecognized tax benefits – December 31 $ 25 $ 5 $ 5 $ 5 $ 5 $ 1 $ 1 $ 3 Year Ended December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Unrecognized tax benefits – January 1 $ 88 $ 72 $ 1 $ 3 $ — $ — $ 1 Unrecognized tax benefits increases (decreases) Gross increases – tax positions in prior periods — — — — 4 4 — Gross decreases – tax positions in prior periods (4 ) (4 ) (1 ) (1 ) — — — Decreases due to settlements (68 ) (67 ) — — — — (1 ) Reduction due to lapse of statute of limitations 1 — 2 — — — — Total changes (71 ) (71 ) 1 (1 ) 4 4 (1 ) Unrecognized tax benefits – December 31 $ 17 $ 1 $ 2 $ 2 $ 4 $ 4 $ — Year Ended December 31, 2015 Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Indiana Unrecognized tax benefits – January 1 $ 213 $ 160 $ 32 $ 23 $ 8 $ 1 Unrecognized tax benefits increases (decreases) Gross increases – tax positions in prior periods — — 1 1 — — Gross decreases – tax positions in prior periods (48 ) (45 ) — — — — Decreases due to settlements (45 ) (43 ) — — — — Reduction due to lapse of statute of limitations (32 ) — (32 ) (21 ) (8 ) — Total changes (125 ) (88 ) (31 ) (20 ) (8 ) — Unrecognized tax benefits – December 31 $ 88 $ 72 $ 1 $ 3 $ — $ 1
Summary of Income Tax Contingencies	The following table includes additional information regarding the Duke Energy Registrants' unrecognized tax benefits at December 31, 2017. During the first quarter of 2018, Duke Energy recognized an approximate $8 million reduction and Duke Energy Carolinas recognized an approximate $1 million reduction in unrecognized tax benefits. No additional material reductions are expected in the next 12 months. December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Amount that if recognized, would affect the effective tax rate or regulatory liability (a) $ 15 $ 4 $ 7 $ 5 $ 1 $ 1 $ 1 $ 3 Amount that if recognized, would be recorded as a component of discontinued operations 7 — — — — 2 — — (a) Duke Energy, Duke Energy Carolinas, Progress Energy, Duke Energy Progress, Duke Energy Florida, Duke Energy Indiana and Piedmont are unable to estimate the specific amounts that would affect the effective tax rate versus the regulatory liability. The following tables include interest recognized in the Consolidated Statements of Operations and the Consolidated Balance Sheets. Year Ended December 31, 2017 Duke Duke Duke Duke Energy Progress Energy Energy (in millions) Energy Carolinas Energy Progress Florida Net interest income recognized related to income taxes $ — $ — $ 1 $ — $ 1 Net interest expense recognized related to income taxes — 2 — — — Interest payable related to income taxes 5 25 1 1 — Year Ended December 31, 2016 Duke Duke Duke Duke Energy Progress Energy Energy (in millions) Energy Carolinas Energy Progress Florida Net interest income recognized related to income taxes $ — $ — $ 1 $ — $ 2 Net interest expense recognized related to income taxes — 7 — — — Interest payable related to income taxes 4 23 1 1 — Year Ended December 31, 2015 Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Indiana Net interest income recognized related to income taxes $ 12 $ — $ 2 $ 2 $ 1 $ 1 Net interest expense recognized related to income taxes — 1 — — — — Interest receivable related to income taxes 3 — — — — 3 Interest payable related to income taxes — 14 — 1 — —
Piedmont Natural Gas [Member]
Income Tax Disclosure [Line Items]
Schedule of Components of Income Tax Expense (Benefit)	Piedmont Two Months Ended Years Ended October 31, (in millions) December 31, 2016 2016 2015 Current income taxes Federal $ 4 $ 27 $ (1 ) State (2 ) 12 1 Total current income taxes 2 39 — Deferred income taxes Federal 24 79 78 State 6 6 12 Total deferred income taxes (a)(b) 30 85 90 Total income tax expense from continuing operations included in Consolidated Statements of Operations $ 32 $ 124 $ 90 (a) Includes benefits of NOL and tax carryforwards of $17 million and $91 million for the two months ended December 31, 2016, and the year ended October 31, 2016, respectively. (b) Includes benefits and utilization of NOL carryforwards of $46 million for the year ended October 31, 2015.
Summary of Effective Tax Rates	Piedmont Two Months Ended Years Ended October 31, (in millions) December 31, 2016 2016 2015 Income tax expense, computed at the statutory rate of 35 percent $ 30 $ 111 $ 79 State income tax, net of federal income tax effect 1 11 9 Other items, net 1 2 2 Income tax expense from continuing operations $ 32 $ 124 $ 90 Effective tax rate 37.2 % 39.1 % 39.7 %

Other Income and Expenses, Net

Other Income and Expenses, Net (Tables)	12 Months Ended
	Dec. 31, 2017
Component Of Other Income Expense Nonoperating [Line Items]
Schedule of Other Income and Expenses, Net	The components of Other income and expenses, net on the Consolidated Statements of Operations are as follows. Amounts for Piedmont were not material. Year Ended December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Interest income $ 13 $ 2 $ 6 $ 2 $ 5 $ 6 $ 8 AFUDC equity 237 106 92 47 45 11 28 Post in-service equity returns 40 28 12 12 — — — Nonoperating income, other 62 3 18 4 11 — 1 Other income and expense, net $ 352 $ 139 $ 128 $ 65 $ 61 $ 17 $ 37 Year Ended December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Interest income $ 21 $ 4 $ 4 $ 3 $ 2 $ 5 $ 6 AFUDC equity 200 102 76 50 26 6 16 Post in-service equity returns 67 55 12 12 — — — Nonoperating income (expense), other 36 1 22 6 16 (2 ) — Other income and expense, net $ 324 $ 162 $ 114 $ 71 $ 44 $ 9 $ 22 Year Ended December 31, 2015 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Interest income $ 20 $ 2 $ 4 $ 2 $ 2 $ 4 $ 6 AFUDC equity 164 96 54 47 7 3 11 Post in-service equity returns 73 60 13 13 — — — Nonoperating income (expense), other 33 2 26 9 15 (1 ) (6 ) Other income and expense, net $ 290 $ 160 $ 97 $ 71 $ 24 $ 6 $ 11

Quarterly Financial Data (Una58

Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Line Items]
Schedule Of Quarterly Financial Information	Quarterly EPS amounts may not sum to the full-year total due to changes in the weighted average number of common shares outstanding and rounding. First Second Third Fourth (in millions, except per share data) Quarter Quarter Quarter Quarter Total 2017 Operating revenues $ 5,729 $ 5,555 $ 6,482 $ 5,799 $ 23,565 Operating income 1,437 1,387 1,695 1,262 5,781 Income from continuing operations 717 691 957 705 3,070 Loss from discontinued operations, net of tax — (2 ) (2 ) (2 ) (6 ) Net income 717 689 955 703 3,064 Net income attributable to Duke Energy Corporation 716 686 954 703 3,059 Earnings per share: Income from continuing operations attributable to Duke Energy Corporation common stockholders Basic $ 1.02 $ 0.98 $ 1.36 $ 1.00 $ 4.37 Diluted $ 1.02 $ 0.98 $ 1.36 $ 1.00 $ 4.37 Loss from discontinued operations attributable to Duke Energy Corporation common stockholders Basic $ — $ — $ — $ — $ (0.01 ) Diluted $ — $ — $ — $ — $ (0.01 ) Net income attributable to Duke Energy Corporation common stockholders Basic $ 1.02 $ 0.98 $ 1.36 $ 1.00 $ 4.36 Diluted $ 1.02 $ 0.98 $ 1.36 $ 1.00 $ 4.36 2016 Operating revenues $ 5,377 $ 5,213 $ 6,576 $ 5,577 $ 22,743 Operating income 1,240 1,259 1,954 888 5,341 Income from continuing operations 577 624 1,001 376 2,578 Income (Loss) from discontinued operations, net of tax 122 (112 ) 180 (598 ) (408 ) Net income (loss) 699 512 1,181 (222 ) 2,170 Net income (loss) attributable to Duke Energy Corporation 694 509 1,176 (227 ) 2,152 Earnings per share: Income from continuing operations attributable to Duke Energy Corporation common stockholders Basic $ 0.83 $ 0.90 $ 1.44 $ 0.53 $ 3.71 Diluted $ 0.83 $ 0.90 $ 1.44 $ 0.53 $ 3.71 Income (Loss) from discontinued operations attributable to Duke Energy Corporation common stockholders Basic $ 0.18 $ (0.16 ) $ 0.26 $ (0.86 ) $ (0.60 ) Diluted $ 0.18 $ (0.16 ) $ 0.26 $ (0.86 ) $ (0.60 ) Net income (loss) attributable to Duke Energy Corporation common stockholders Basic $ 1.01 $ 0.74 $ 1.70 $ (0.33 ) $ 3.11 Diluted $ 1.01 $ 0.74 $ 1.70 $ (0.33 ) $ 3.11
Schedule Of Unusual Or Infrequently Occurring Items	The following table includes unusual or infrequently occurring items in each quarter during the two most recently completed fiscal years. All amounts discussed below are pretax. First Second Third Fourth (in millions) Quarter Quarter Quarter Quarter Total 2017 Costs to Achieve Piedmont Merger (see Note 2) $ (16 ) $ (30 ) $ (23 ) $ (34 ) $ (103 ) Regulatory Settlements (see Note 4) — — (135 ) (23 ) (158 ) Commercial Renewables Impairments (see Notes 10 and 11) — — (84 ) (18 ) (102 ) Impacts of the Tax Act (see Note 22) — — — 102 102 Total $ (16 ) $ (30 ) $ (242 ) $ 27 $ (261 ) 2016 Costs to Achieve Mergers (see Note 2) $ (120 ) $ (111 ) $ (84 ) $ (208 ) $ (523 ) Commercial Renewables Impairment (see Note 12) — — (71 ) — (71 ) Loss on Sale of International Disposal Group (see Note 2) — — — (514 ) (514 ) Impairment of Assets in Central America (see Note 2) — (194 ) — — (194 ) Cost Savings Initiatives (see Note 19) (20 ) (24 ) (19 ) (29 ) (92 ) Total $ (140 ) $ (329 ) $ (174 ) $ (751 ) $ (1,394 )
Duke Energy Carolinas [Member]
Quarterly Financial Information Disclosure [Line Items]
Schedule Of Quarterly Financial Information	DUKE ENERGY CAROLINAS First Second Third Fourth (in millions) Quarter Quarter Quarter Quarter Total 2017 Operating revenues $ 1,716 $ 1,729 $ 2,136 $ 1,721 $ 7,302 Operating income 484 485 777 403 2,149 Net income 270 273 466 205 1,214 2016 Operating revenues $ 1,740 $ 1,675 $ 2,226 $ 1,681 $ 7,322 Operating income 481 464 815 302 2,062 Net income 271 261 494 140 1,166
Schedule Of Unusual Or Infrequently Occurring Items	The following table includes unusual or infrequently occurring items in each quarter during the two most recently completed fiscal years. All amounts discussed below are pretax. First Second Third Fourth (in millions) Quarter Quarter Quarter Quarter Total 2017 Costs to Achieve Piedmont Merger (see Note 2) $ (4 ) $ (6 ) $ (5 ) $ (5 ) $ (20 ) Impacts of the Tax Act (see Note 22) — — — (15 ) (15 ) Total $ (4 ) $ (6 ) $ (5 ) $ (20 ) $ (35 ) 2016 Costs to Achieve Mergers $ (11 ) $ (12 ) $ (13 ) $ (68 ) $ (104 ) Cost Savings Initiatives (see Note 19) (10 ) (10 ) (8 ) (11 ) (39 ) Total $ (21 ) $ (22 ) $ (21 ) $ (79 ) $ (143 )
Progress Energy [Member]
Quarterly Financial Information Disclosure [Line Items]
Schedule Of Quarterly Financial Information	PROGRESS ENERGY First Second Third Fourth (in millions) Quarter Quarter Quarter Quarter Total 2017 Operating revenues $ 2,179 $ 2,392 $ 2,864 $ 2,348 $ 9,783 Operating income 487 591 657 493 2,228 Net income 201 277 343 447 1,268 Net income attributable to Parent 199 274 341 444 1,258 2016 Operating revenues $ 2,332 $ 2,348 $ 2,965 $ 2,208 $ 9,853 Operating income 475 560 814 292 2,141 Income from continuing operations 212 274 449 104 1,039 Net income 212 274 449 106 1,041 Net income attributable to Parent 209 272 446 104 1,031
Schedule Of Unusual Or Infrequently Occurring Items	The following table includes unusual or infrequently occurring items in each quarter during the two most recently completed fiscal years. All amounts discussed below are pretax. First Second Third Fourth (in millions) Quarter Quarter Quarter Quarter Total 2017 Costs to Achieve Piedmont Merger (see Note 2) $ (4 ) $ (7 ) $ (6 ) $ (6 ) $ (23 ) Regulatory Settlements (see Note 4) — — (135 ) (23 ) (158 ) Impacts of the Tax Act (see Note 22) — — — 246 246 Total $ (4 ) $ (7 ) $ (141 ) $ 217 $ 65 2016 Costs to Achieve Mergers $ (7 ) $ (8 ) $ (10 ) $ (44 ) $ (69 ) Cost Savings Initiatives (see Note 19) (8 ) (8 ) (10 ) (14 ) (40 ) Total $ (15 ) $ (16 ) $ (20 ) $ (58 ) $ (109 )
Duke Energy Progress [Member]
Quarterly Financial Information Disclosure [Line Items]
Schedule Of Quarterly Financial Information	DUKE ENERGY PROGRESS First Second Third Fourth (in millions) Quarter Quarter Quarter Quarter Total 2017 Operating revenues $ 1,219 $ 1,199 $ 1,460 $ 1,251 $ 5,129 Operating income 286 282 411 256 1,235 Net income 147 154 246 168 715 2016 Operating revenues $ 1,307 $ 1,213 $ 1,583 $ 1,174 $ 5,277 Operating income 258 255 438 135 1,086 Net income 137 131 271 60 599
Schedule Of Unusual Or Infrequently Occurring Items	The following table includes unusual or infrequently occurring items in each quarter during the two most recently completed fiscal years. All amounts discussed below are pretax. First Second Third Fourth (in millions) Quarter Quarter Quarter Quarter Total 2017 Costs to Achieve Piedmont Merger (see Note 2) $ (2 ) $ (4 ) $ (4 ) $ (4 ) $ (14 ) Regulatory Settlements (see Note 4) — — — (23 ) (23 ) Impacts of the Tax Act (see Note 22) — — — 40 40 Total $ (2 ) $ (4 ) $ (4 ) $ 13 $ 3 2016 Costs to Achieve Mergers $ (5 ) $ (5 ) $ (6 ) $ (40 ) $ (56 ) Cost Savings Initiatives (see Note 19) (5 ) (5 ) (7 ) (6 ) (23 ) Total $ (10 ) $ (10 ) $ (13 ) $ (46 ) $ (79 )
Duke Energy Florida [Member]
Quarterly Financial Information Disclosure [Line Items]
Schedule Of Quarterly Financial Information	DUKE ENERGY FLORIDA First Second Third Fourth (in millions) Quarter Quarter Quarter Quarter Total 2017 Operating revenues $ 959 $ 1,191 $ 1,401 $ 1,095 $ 4,646 Operating income 196 306 240 234 976 Net income 90 158 120 344 712 2016 Operating revenues $ 1,024 $ 1,133 $ 1,381 $ 1,030 $ 4,568 Operating income 213 300 373 155 1,041 Net income 110 171 206 64 551
Schedule Of Unusual Or Infrequently Occurring Items	The following table includes unusual or infrequently occurring items in each quarter during the two most recently completed fiscal years. All amounts discussed below are pretax. First Second Third Fourth (in millions) Quarter Quarter Quarter Quarter Total 2017 Costs to Achieve Piedmont Merger (see Note 2) $ (2 ) $ (3 ) $ (2 ) $ (2 ) $ (9 ) Regulatory Settlements (see Note 4) — — (135 ) — (135 ) Impacts of the Tax Act (see Note 22) — — — 226 226 Total $ (2 ) $ (3 ) $ (137 ) $ 224 $ 82 2016 Costs to Achieve Mergers $ (2 ) $ (3 ) $ (4 ) $ (4 ) $ (13 ) Cost Savings Initiatives (see Note 19) (2 ) (3 ) (3 ) (9 ) (17 ) Total $ (4 ) $ (6 ) $ (7 ) $ (13 ) $ (30 )
Duke Energy Ohio [Member]
Quarterly Financial Information Disclosure [Line Items]
Schedule Of Quarterly Financial Information	DUKE ENERGY OHIO First Second Third Fourth (in millions) Quarter Quarter Quarter Quarter Total 2017 Operating revenues $ 518 $ 437 $ 471 $ 497 $ 1,923 Operating income 83 65 102 76 326 Loss from discontinued operations, net of tax — — (1 ) — (1 ) Net income 42 30 55 65 192 2016 Operating revenues $ 516 $ 428 $ 489 $ 511 $ 1,944 Operating income 96 55 106 90 347 Income from discontinued operations, net of tax 2 — 34 — 36 Net income 59 23 89 57 228
Schedule Of Unusual Or Infrequently Occurring Items	The following table includes unusual or infrequently occurring items in each quarter during the two most recently completed fiscal years. All amounts discussed below are pretax. First Second Third Fourth (in millions) Quarter Quarter Quarter Quarter Total 2017 Costs to Achieve Piedmont Merger (see Note 2) $ (1 ) $ (1 ) $ (2 ) $ (2 ) $ (6 ) Impacts of the Tax Act (see Note 22) — — — 23 23 Total $ (1 ) $ (1 ) $ (2 ) $ 21 $ 17 2016 Costs to Achieve Mergers $ (1 ) $ (1 ) $ (2 ) $ (2 ) $ (6 ) Cost Savings Initiatives (see Note 19) (1 ) (1 ) — (1 ) (3 ) Total $ (2 ) $ (2 ) $ (2 ) $ (3 ) $ (9 )
Duke Energy Indiana [Member]
Quarterly Financial Information Disclosure [Line Items]
Schedule Of Quarterly Financial Information	DUKE ENERGY INDIANA First Second Third Fourth (in millions) Quarter Quarter Quarter Quarter Total 2017 Operating revenues $ 758 $ 742 $ 802 $ 745 $ 3,047 Operating income 186 210 230 170 796 Net income 91 106 121 36 354 2016 Operating revenues $ 714 $ 702 $ 809 $ 733 $ 2,958 Operating income 176 174 239 176 765 Net income 95 85 129 72 381
Schedule Of Unusual Or Infrequently Occurring Items	The following table includes unusual or infrequently occurring items in each quarter during the two most recently completed fiscal years. All amounts discussed below are pretax. First Second Third Fourth (in millions) Quarter Quarter Quarter Quarter Total 2017 Costs to Achieve Piedmont Merger (see Note 2) $ (1 ) $ (2 ) $ (2 ) $ (1 ) $ (6 ) Impacts of the Tax Act (see Note 22) — — — (55 ) (55 ) Total $ (1 ) $ (2 ) $ (2 ) $ (56 ) $ (61 ) 2016 Costs to Achieve Mergers $ (1 ) $ (2 ) $ (3 ) $ (3 ) $ (9 ) Cost Savings Initiatives (see Note 19) (1 ) (4 ) (1 ) (1 ) (7 ) Total $ (2 ) $ (6 ) $ (4 ) $ (4 ) $ (16 )
Piedmont Natural Gas [Member]
Quarterly Financial Information Disclosure [Line Items]
Schedule Of Quarterly Financial Information	The following tables include data for Piedmont's fiscal years ending December 31, 2017, and October 31, 2016. First Second Third Fourth (in millions) Quarter Quarter Quarter Quarter Total 2017 Operating revenues $ 500 $ 201 $ 183 $ 444 $ 1,328 Operating income (loss) 170 5 (4 ) 115 286 Net income (loss) 95 (8 ) (11 ) 63 139 2016 Operating revenues $ 464 $ 353 $ 160 $ 172 $ 1,149 Operating income (loss) 171 104 — (50 ) 225 Net income (loss) 98 63 (7 ) 39 193 For the two months ended December 31, 2016, Piedmont's operating revenues, operating income, and net income were $322 million , $96 million and $54 million , respectively.
Schedule Of Unusual Or Infrequently Occurring Items	The following table includes unusual or infrequently occurring items in each quarter during the two most recently completed fiscal years. All amounts discussed below are pretax. First Second Third Fourth (in millions) Quarter Quarter Quarter Quarter Total 2017 Costs to Achieve Piedmont Merger (see Note 2) $ (6 ) $ (13 ) $ (8 ) $ (19 ) $ (46 ) Impacts of the Tax Act (see Note 22) — — — 2 2 Total $ (6 ) $ (13 ) $ (8 ) $ (17 ) $ (44 ) 2016 Costs to Achieve Mergers $ (6 ) $ (2 ) $ (1 ) $ (53 ) $ (62 ) For the two months ended December 31, 2016, Piedmont's costs to achieve merger were $7 million .

Summary of Significant Accoun59

Summary of Significant Accounting Policies (Narrative)(Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Restricted Cash [Abstract]
Restricted cash	$ 147	$ 137

Summary of Significant Accoun60

Summary of Significant Accounting Policies (Other Assets and Liabilities)(Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Current Liabilities, Other [Member]
Organization And Basis Of Presentation [Line Items]
Accrued compensation	$ 757	$ 765
Duke Energy Carolinas [Member] | Current Liabilities, Other [Member]
Organization And Basis Of Presentation [Line Items]
Customer deposits	121	155
Accrued compensation	252	248
Progress Energy [Member] | Current Assets, Other [Member]
Organization And Basis Of Presentation [Line Items]
Income taxes receivable	278	19
Progress Energy [Member] | Current Liabilities, Other [Member]
Organization And Basis Of Presentation [Line Items]
Customer deposits	338	363
Duke Energy Progress [Member] | Current Liabilities, Other [Member]
Organization And Basis Of Presentation [Line Items]
Customer deposits	129	141
Accrued compensation	132	135
Duke Energy Florida [Member] | Current Liabilities, Other [Member]
Organization And Basis Of Presentation [Line Items]
Customer deposits	208	222
Duke Energy Ohio [Member] | Current Assets, Other [Member]
Organization And Basis Of Presentation [Line Items]
Income taxes receivable	36	16
Duke Energy Ohio [Member] | Current Liabilities, Other [Member]
Organization And Basis Of Presentation [Line Items]
Customer deposits	46	62
Duke Energy Indiana [Member] | Current Liabilities, Other [Member]
Organization And Basis Of Presentation [Line Items]
Customer deposits	45	44
Piedmont Natural Gas [Member] | Current Assets, Other [Member]
Organization And Basis Of Presentation [Line Items]
Income taxes receivable	$ 43	$ 9

Summary of Significant Accoun61

Summary of Significant Accounting Policies (Amounts Attributable to Controlling Interests) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net Income (Loss) Attributable to Parent [Abstract]
Income (Loss) from Continuing Operations	$ 705	$ 957	$ 691	$ 717	$ 376	$ 1,001	$ 624	$ 577	$ 3,070	$ 2,578	$ 2,654
Income (Loss) from Continuing Operations Attributable to Noncontrolling Interests									5	7	9
Income (Loss) from Continuing Operations Attributable to Parent									3,065	2,571	2,645
Income (Loss) From Discontinued Operations, net of tax	(2)	(2)	(2)		(598)	180	(112)	122	(6)	(408)	177
Income (Loss) from Discontinued Operations Attributable to Noncontrolling Interest, net of tax										11	6
(Loss) Income from Discontinued Operations Attributable to Parent, net of tax										(419)	171
Net income (loss)	703	955	689	717	(222)	1,181	512	699	3,064	2,170	2,831
Net Income Attributable to Noncontrolling Interest									5	18	15
Net Income (Loss) Attributable to Parent	$ 703	$ 954	$ 686	$ 716	$ (227)	$ 1,176	$ 509	$ 694	$ 3,059	$ 2,152	$ 2,816

Summary of Significant Accoun62

Summary of Significant Accounting Policies (Inventory)(Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Public Utilities, Inventory [Line Items]
Materials and supplies	$ 2,293	$ 2,374
Coal	603	774
Natural gas, oil, other	354	374
Total inventory	3,250	3,522
Duke Energy Carolinas [Member]
Public Utilities, Inventory [Line Items]
Materials and supplies	744	767
Coal	192	251
Natural gas, oil, other	35	37
Total inventory	971	1,055
Progress Energy [Member]
Public Utilities, Inventory [Line Items]
Materials and supplies	1,118	1,167
Coal	255	314
Natural gas, oil, other	219	236
Total inventory	1,592	1,717
Duke Energy Progress [Member]
Public Utilities, Inventory [Line Items]
Materials and supplies	774	813
Coal	139	148
Natural gas, oil, other	104	115
Total inventory	1,017	1,076
Duke Energy Florida [Member]
Public Utilities, Inventory [Line Items]
Materials and supplies	343	354
Coal	116	166
Natural gas, oil, other	115	121
Total inventory	574	641
Duke Energy Ohio [Member]
Public Utilities, Inventory [Line Items]
Materials and supplies	82	84
Coal	17	19
Natural gas, oil, other	34	34
Total inventory	133	137
Duke Energy Indiana [Member]
Public Utilities, Inventory [Line Items]
Materials and supplies	309	312
Coal	139	190
Natural gas, oil, other	2	2
Total inventory	450	504
Piedmont Natural Gas [Member]
Public Utilities, Inventory [Line Items]
Materials and supplies	2	1
Natural gas, oil, other	64	65
Total inventory	$ 66	$ 66

Summary of Significant Accoun63

Summary of Significant Accounting Policies (Property, Plant and Equipment)(Details)	2 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015	Oct. 31, 2015
Public Utility, Property, Plant and Equipment [Line Items]
Weighted-average depreciation rate		2.80%	2.80%		2.90%
Duke Energy Carolinas [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Weighted-average depreciation rate		2.80%	2.80%		2.80%
Progress Energy [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Weighted-average depreciation rate		2.60%	2.70%		2.60%
Duke Energy Progress [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Weighted-average depreciation rate		2.60%	2.60%		2.60%
Duke Energy Florida [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Weighted-average depreciation rate		2.80%	2.80%		2.70%
Duke Energy Ohio [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Weighted-average depreciation rate		2.80%	2.60%		2.70%
Duke Energy Indiana [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Weighted-average depreciation rate		3.00%	3.10%		3.00%
Piedmont Natural Gas [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Weighted-average depreciation rate	2.40%	2.30%		2.40%		2.50%

Summary of Significant Accoun64

Summary of Significant Accounting Policies (Unbilled Revenues)(Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Organization And Basis Of Presentation [Line Items]
Unbilled receivables	$ 944	$ 831
Duke Energy Carolinas [Member]
Organization And Basis Of Presentation [Line Items]
Unbilled receivables	342	313
Progress Energy [Member]
Organization And Basis Of Presentation [Line Items]
Unbilled receivables	228	161
Duke Energy Progress [Member]
Organization And Basis Of Presentation [Line Items]
Unbilled receivables	143	102
Duke Energy Florida [Member]
Organization And Basis Of Presentation [Line Items]
Unbilled receivables	85	59
Duke Energy Ohio [Member]
Organization And Basis Of Presentation [Line Items]
Unbilled receivables	4	2
Duke Energy Indiana [Member]
Organization And Basis Of Presentation [Line Items]
Unbilled receivables	21	32
Piedmont Natural Gas [Member]
Organization And Basis Of Presentation [Line Items]
Unbilled receivables	86	77
Cinergy Receivables [Member] | Duke Energy Ohio [Member]
Organization And Basis Of Presentation [Line Items]
Unbilled receivables	104	97
Cinergy Receivables [Member] | Duke Energy Indiana [Member]
Organization And Basis Of Presentation [Line Items]
Unbilled receivables	$ 132	$ 123

Summary of Significant Accoun65

Summary of Significant Accounting Policies (Allowance for Doubtful Accounts)(Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015
Organization And Basis Of Presentation [Line Items]
Allowance for doubtful accounts - receivables	$ 14	$ 14		$ 12
Duke Energy Carolinas [Member]
Organization And Basis Of Presentation [Line Items]
Allowance for doubtful accounts - receivables	2	2		3
Progress Energy [Member]
Organization And Basis Of Presentation [Line Items]
Allowance for doubtful accounts - receivables	4	6		6
Duke Energy Progress [Member]
Organization And Basis Of Presentation [Line Items]
Allowance for doubtful accounts - receivables	1	4		4
Duke Energy Florida [Member]
Organization And Basis Of Presentation [Line Items]
Allowance for doubtful accounts - receivables	3	2		2
Duke Energy Ohio [Member]
Organization And Basis Of Presentation [Line Items]
Allowance for doubtful accounts - receivables	3	2		2
Duke Energy Indiana [Member]
Organization And Basis Of Presentation [Line Items]
Allowance for doubtful accounts - receivables	2	1		1
Piedmont Natural Gas [Member]
Organization And Basis Of Presentation [Line Items]
Allowance for doubtful accounts - receivables	2	3	$ 2	2
Variable Interest Entity [Member]
Organization And Basis Of Presentation [Line Items]
Allowance for doubtful accounts - receivables of VIEs	54	54		53
Variable Interest Entity [Member] | Duke Energy Carolinas [Member]
Organization And Basis Of Presentation [Line Items]
Allowance for doubtful accounts - receivables of VIEs	7	7		7
Variable Interest Entity [Member] | Progress Energy [Member]
Organization And Basis Of Presentation [Line Items]
Allowance for doubtful accounts - receivables of VIEs	7	7		8
Variable Interest Entity [Member] | Duke Energy Progress [Member]
Organization And Basis Of Presentation [Line Items]
Allowance for doubtful accounts - receivables of VIEs	5	5		5
Variable Interest Entity [Member] | Duke Energy Florida [Member]
Organization And Basis Of Presentation [Line Items]
Allowance for doubtful accounts - receivables of VIEs	$ 2	$ 2		$ 3

Summary of Significant Accoun66

Summary of Significant Accounting Policies (Excise Taxes)(Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015	Oct. 31, 2015
Organization And Basis Of Presentation [Line Items]
Excise taxes	$ 376	$ 362		$ 396
Duke Energy Carolinas [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes	36	31		31
Progress Energy [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes	220	213		229
Duke Energy Progress [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes	19	18		16
Duke Energy Florida [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes	201	195		213
Duke Energy Ohio [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes	98	100		102
Duke Energy Indiana [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes	20	$ 17		$ 34
Piedmont Natural Gas [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes	$ 2		$ 2		$ 2

Summary of Significant Accoun67

Summary of Significant Accounting Policies (New Accounting Standards) (Details) $ in Millions	Dec. 31, 2017USD ($)
Adjustments for New Accounting Pronouncement [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Potential Increase (Decrease) in Restricted Cash	$ 147

Acquisitions and Dispositions -

Acquisitions and Dispositions - Acquisitions (Narrative) (Details) - USD ($) shares in Millions, $ in Millions	Oct. 03, 2016	Oct. 31, 2016	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Aug. 31, 2016	Aug. 01, 2016
Business Acquisition [Line Items]
Business Combination, Integration Related Costs			$ 34	$ 23	$ 30	$ 16					$ 103
Asset Impairment Charges											282	$ 18	$ 106
Net Income (Loss) Attributable to Parent			703	954	686	716	$ (227)	$ 1,176	$ 509	$ 694	3,059	2,152	2,816
Long-term Debt			52,279				47,895				52,279	47,895
Asset retirement obligations assumed												22
Piedmont Natural Gas [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross	$ 5,000
Long-term debt assumed	$ 2,002
Business Combination, Integration Related Costs											103	439	9
Asset Impairment Charges											7
Business Combination, After Tax Integration Related Costs												279	19
Revenues												367
Net Income (Loss) Attributable to Parent												20
Long-term Debt														$ 3,750
Facility Size															$ 4,900
Common stock issuances, including dividend reinvestment and employee benefits (in shares)		10.6
Forward Contract Indexed to Issuer's Equity, Indexed Shares										10.6
Proceeds from Issuance or Sale of Equity		$ 723
Duke Energy Progress [Member]
Business Acquisition [Line Items]
Business Combination, Integration Related Costs			4	4	4	2					14
Asset Impairment Charges											19	1	5
Net Income (Loss) Attributable to Parent			168	$ 246	$ 154	$ 147	60	271	$ 131	$ 137	715	599	$ 566
Long-term Debt			$ 7,357				$ 7,011				7,357	7,011
Interest Rate Contract [Member] | Piedmont Natural Gas [Member]
Business Acquisition [Line Items]
Loss on Interest Rate Derivative Instruments Not Designated as Hedging Instruments												190
Sales [Member] | Piedmont Natural Gas [Member]
Business Acquisition [Line Items]
Business Combination, Integration Related Costs												10
Operating Expense [Member] | Piedmont Natural Gas [Member]
Business Acquisition [Line Items]
Business Combination, Integration Related Costs											64	101
Operating Income (Loss) [Member] | Piedmont Natural Gas [Member]
Business Acquisition [Line Items]
Business Combination, Integration Related Costs												46
Interest Expense [Member] | Piedmont Natural Gas [Member]
Business Acquisition [Line Items]
Business Combination, Integration Related Costs												234
August 2016 Term Loan Facility [Member] | Piedmont Natural Gas [Member]
Business Acquisition [Line Items]
Long-term Line of Credit								750
Facility Size								$ 1,500
Other Expense [Member] | Piedmont Natural Gas [Member]
Business Acquisition [Line Items]
Business Combination, Integration Related Costs											$ 71	104
Other Expense [Member] | Operating Expense [Member] | Piedmont Natural Gas [Member]
Business Acquisition [Line Items]
Business Combination, Integration Related Costs												94
Other Expense [Member] | Operating Income (Loss) [Member] | Piedmont Natural Gas [Member]
Business Acquisition [Line Items]
Business Combination, Integration Related Costs												$ 10

Acquisitions and Dispositions69

Acquisitions and Dispositions - Dispositions (Narrative) (Details) $ in Millions	Apr. 02, 2015USD ($)MW	Dec. 31, 2016USD ($)MW	Dec. 31, 2017USD ($)
International Energy [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from Divestiture of Businesses		$ 1,900
DEI Latin American [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Owned Plant Capacity | MW		2,230
Enterprise Value		$ 1,200
DEI Brazil Holdings [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Owned Plant Capacity | MW		2,090
Enterprise Value		$ 1,200
Duke Energy Ohio [Member] | Midwest Generation Business [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Owned Plant Capacity | MW	5,900
Proceeds from Divestiture of Businesses, Net of Cash Divested	$ 2,800
Obligations [Member] | International Energy [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Tax obligations			$ 78

Acquisitions and Dispositions70

Acquisitions and Dispositions (Purchase Price Allocation) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Oct. 03, 2016
Business Acquisition [Line Items]
Goodwill	$ 19,396	$ 19,425
Piedmont Natural Gas [Member]
Business Acquisition [Line Items]
Current assets			$ 497
Net property, plant and equipment			4,714
Goodwill			3,353
Other long-term assets			804
Total assets			9,368
Current liabilities, including current maturities of long-term debt			576
Long-term liabilities			1,790
Long-term debt			2,002
Total liabilities			4,368
Total purchase price			$ 5,000

Acquisitions and Dispositions71

Acquisitions and Dispositions (Pro Forma Information) (Details) - Piedmont Natural Gas [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Revenues	$ 23,504	$ 23,570
Net income attributable to Duke Energy Corporation	$ 2,442	$ 2,877

Acquisitions and Dispositions72

Acquisitions and Dispositions (Duke Energy Discontinued Operations) (Details) - USD ($) $ in Millions	3 Months Ended							12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income (Loss) From Discontinued Operations, net of tax	$ (2)	$ (2)	$ (2)	$ (598)	$ 180	$ (112)	$ 122	$ (6)	$ (408)	$ 177
International Energy [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income (Loss) From Discontinued Operations, net of tax									(534)	157
Midwest Generation Business [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income (Loss) From Discontinued Operations, net of tax									36	33
Other Disposal Groups [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income (Loss) From Discontinued Operations, net of tax									$ 90	$ (13)

Acquisitions and Dispositions73

Acquisitions and Dispositions (International Energy Discontinued Operations) (Details) - USD ($) $ in Millions	3 Months Ended							12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income tax expense (benefit)								$ (6)	$ (30)	$ 89
Income (Loss) From Discontinued Operations, net of tax	$ (2)	$ (2)	$ (2)	$ (598)	$ 180	$ (112)	$ 122	(6)	(408)	177
Asset Impairment Charges								$ 282	18	106
International Energy [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income (Loss) From Discontinued Operations, net of tax									(534)	157
Asset Impairment Charges									194
Cumulative foreign currency translation losses									620
Income (Loss) from Discontinued Operation, before Income Tax, Attributable to Parent									(445)	221
Income tax expense on disposal									126
After-tax loss on disposal									640
Previously Remitted Earnings [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income tax expense (benefit)									(95)
Previously Remitted Earnings [Member] | International Energy [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Foreign Income Tax Expense (Benefit), Continuing Operations									(95)
Discontinued Operations, Disposed of by Sale [Member] | International Energy [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Operating Revenues									988	1,088
Fuel used in electric generation and purchased power									227	306
Cost of natural gas									43	53
Operation, maintenance and other									341	334
Depreciation and amortization									62	92
Property and other taxes									15	7
Impairment charges									194	13
(Loss) Gains on Sales of Other Assets and Other, net									(3)	6
Other income and expenses, net									58	23
Interest Expense									82	85
Pretax loss on disposal									514
(Loss) Income before income taxes									(435)	227
Income tax expense (benefit)									$ 99	$ 70

Acquisitions and Dispositions74

Acquisitions and Dispositions (Cash Flow Statement) (Details) - International Energy [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Operating Activities	$ 204	$ 248
Investing Activities	$ (434)	$ 177

Acquisitions and Dispositions75

Acquisitions and Dispositions (Midwest Generation Exit) (Details) - USD ($) $ in Millions	3 Months Ended							12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income tax expense (benefit)								$ (6)	$ (30)	$ 89
Income (Loss) From Discontinued Operations, net of tax	$ (2)	$ (2)	$ (2)	$ (598)	$ 180	$ (112)	$ 122	(6)	(408)	177
Duke Energy Ohio [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income tax expense (benefit)									(36)	22
Income (Loss) From Discontinued Operations, net of tax		$ (1)			$ 34		$ 2	$ (1)	36	23
Midwest Generation Business [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Operating Revenues										543
Loss on disposition										(45)
Income (loss) before income taxes										59
Income tax expense (benefit)									(36)	26
Income (Loss) From Discontinued Operations, net of tax									36	33
Midwest Generation Business [Member] | Duke Energy Ohio [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Operating Revenues										412
Loss on disposition										(52)
Income (loss) before income taxes										44
Income tax expense (benefit)									(36)	21
Income (Loss) From Discontinued Operations, net of tax									$ 36	23
Antitrust Lawsuit [Member] | Duke Energy Ohio [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Litigation Settlement, Expense										81
Antitrust Lawsuit [Member] | Midwest Generation Business [Member] | Duke Energy Ohio [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Litigation Settlement, Expense										$ 81

Business Segments (Narrative) (

Business Segments (Narrative) (Details)	12 Months Ended
	Dec. 31, 2017segment
Duke Energy Ohio [Member]
Segment Reporting Information [Line Items]
Number of Reportable Segments	2

Business Segments (Business Seg

Business Segments (Business Segment Data) (Details) - USD ($) $ in Millions	Oct. 03, 2016	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information, Profit (Loss) [Abstract]
Revenues		$ 5,799	$ 6,482	$ 5,555	$ 5,729	$ 5,577	$ 6,576	$ 5,213	$ 5,377	$ 23,565	$ 22,743	$ 22,371
Interest expense										1,986	1,916	1,527
Depreciation and amortization										3,527	3,294	3,053
Equity in earnings (losses) of unconsolidated affiliates										119	(15)	69
Income tax expense (benefit) from continuing operations										1,196	1,156	1,256
Segment income (loss)										3,065	2,571	2,645
Add back noncontrolling interests component										5	7	9
(Loss) Income from Discontinued Operations, net of tax		(2)	(2)	(2)		(598)	180	(112)	122	(6)	(408)	177
Net income (loss)		703	955	689	717	(222)	1,181	512	699	3,064	2,170	2,831
Net Income (Loss) Attributable to Parent		703	954	686	716	(227)	1,176	509	694	3,059	2,152	2,816
Tax Act										(112)
Costs to achieve mergers, integration costs		34	23	30	16					103
Asset Impairment Charges										282	18	106
Costs to achieve mergers, acquisition costs						208	84	111	120		523
Segment Reporting Information Assets [Abstract]
Capital investments, expenditures and acquisitions										8,198	13,215	8,363
Segment assets		137,914				132,761				137,914	132,761	121,156
Duke Energy Ohio [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Revenues		497	471	437	518	511	489	428	516	1,923	1,944	1,905
Interest expense										91	86	79
Depreciation and amortization										261	233	227
Income tax expense (benefit) from continuing operations										59	78	81
Segment income (loss)										193	192	149
(Loss) Income from Discontinued Operations, net of tax			(1)				34		2	(1)	36	23
Net Income (Loss) Attributable to Parent		65	55	30	42	57	89	23	59	192	228	172
Tax Act		(23)								(23)
Costs to achieve mergers, integration costs		2	2	$ 1	$ 1					6
Asset Impairment Charges										1
Costs to achieve mergers, acquisition costs						2	$ 2	$ 1	$ 1		6
Segment Reporting Information Assets [Abstract]
Capital investments, expenditures and acquisitions										686	476	399
Segment assets		7,875				7,528				7,875	7,528	7,097
Piedmont Natural Gas [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Net Income (Loss) Attributable to Parent											20
Costs to achieve mergers, integration costs										103	439	9
Asset Impairment Charges										7
Segment Reporting Information Assets [Abstract]
Payments to Acquire Businesses, Gross	$ 5,000
International Energy [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
(Loss) Income from Discontinued Operations, net of tax											(534)	157
Asset Impairment Charges											194
Regulatory settlements [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Regulatory settlement charges		23								158
Asset Impairment Charges			$ 135
Electric Utilities and Infrastructure [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Revenues										21,300	21,336	21,489
Equity in earnings (losses) of unconsolidated affiliates										5	5	(2)
Tax Act										231
Electric Utilities and Infrastructure [Member] | Edwardsport IGCC Plant [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Regulatory settlement charges												58
Electric Utilities and Infrastructure [Member] | Regulatory settlements [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Regulatory settlement charges										98
Gas Utilities and Infrastructure [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Revenues										1,743	875	536
Equity in earnings (losses) of unconsolidated affiliates										62	19	1
Tax Act										26
Gas Utilities and Infrastructure [Member] | Piedmont Natural Gas [Member]
Segment Reporting Information Assets [Abstract]
Payments to Acquire Businesses, Gross	$ 5,000
Commercial Renewables [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Revenues										460	484	286
Equity in earnings (losses) of unconsolidated affiliates										(5)	(82)	(6)
Tax Act										442
Asset Impairment Charges, net of tax										74
Asset Impairment Charges											71
Other Segments [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Revenues										62	48	60
Tax Act										597
Costs to achieve mergers, acquisition costs										64	329	60
Cost Savings Initiative, Net of tax											57	77
Other Segments [Member] | International Energy [Member]
Segment Reporting Information Assets [Abstract]
Capital investments, expenditures and acquisitions											26	45
Total Reportable Segments [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Revenues										23,503	22,695	22,311
Operating Segments [Member] | Electric Utilities and Infrastructure [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Revenues										21,331	21,366	21,521
Interest expense										1,240	1,136	1,074
Depreciation and amortization										3,010	2,897	2,735
Equity in earnings (losses) of unconsolidated affiliates										5	5	(2)
Income tax expense (benefit) from continuing operations										1,355	1,672	1,602
Segment income (loss)										3,210	3,040	2,819
Segment Reporting Information Assets [Abstract]
Capital investments, expenditures and acquisitions										7,024	6,649	6,852
Segment assets		119,423				114,993				119,423	114,993	109,097
Operating Segments [Member] | Electric Utilities and Infrastructure [Member] | Duke Energy Ohio [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Revenues										1,373	1,410	1,331
Interest expense										62	58	53
Depreciation and amortization										178	151	147
Income tax expense (benefit) from continuing operations										40	55	59
Segment income (loss)										138	154	118
Segment Reporting Information Assets [Abstract]
Capital investments, expenditures and acquisitions										491	322	264
Segment assets		5,066				4,782				5,066	4,782	4,534
Operating Segments [Member] | Gas Utilities and Infrastructure [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Revenues										1,836	901	541
Interest expense										105	46	25
Depreciation and amortization										231	115	79
Equity in earnings (losses) of unconsolidated affiliates										62	19	1
Income tax expense (benefit) from continuing operations										116	90	44
Segment income (loss)										319	152	73
Segment Reporting Information Assets [Abstract]
Capital investments, expenditures and acquisitions										907	5,519	234
Segment assets		11,462				10,760				11,462	10,760	2,637
Operating Segments [Member] | Gas Utilities and Infrastructure [Member] | Duke Energy Ohio [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Revenues										508	503	541
Interest expense										28	27	25
Depreciation and amortization										83	80	79
Income tax expense (benefit) from continuing operations										39	44	45
Segment income (loss)										85	77	73
Segment Reporting Information Assets [Abstract]
Capital investments, expenditures and acquisitions										195	154	135
Segment assets		2,758				2,696				2,758	2,696	2,516
Operating Segments [Member] | Commercial Renewables [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Revenues										460	484	286
Interest expense										87	53	44
Depreciation and amortization										155	130	104
Equity in earnings (losses) of unconsolidated affiliates										(5)	(82)	(6)
Income tax expense (benefit) from continuing operations										(628)	(160)	(128)
Segment income (loss)										441	23	52
Segment Reporting Information Assets [Abstract]
Capital investments, expenditures and acquisitions										92	857	1,019
Segment assets		4,156				4,377				4,156	4,377	3,861
Operating Segments [Member] | Total Reportable Segments [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Revenues										23,627	22,751	22,348
Interest expense										1,432	1,235	1,143
Depreciation and amortization										3,396	3,142	2,918
Equity in earnings (losses) of unconsolidated affiliates										62	(58)	(7)
Income tax expense (benefit) from continuing operations										843	1,602	1,518
Segment income (loss)										3,970	3,215	2,944
Segment Reporting Information Assets [Abstract]
Capital investments, expenditures and acquisitions										8,023	13,025	8,105
Segment assets		135,041				130,130				135,041	130,130	115,595
Operating Segments [Member] | Total Reportable Segments [Member] | Duke Energy Ohio [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Revenues										1,881	1,913	1,872
Interest expense										90	85	78
Depreciation and amortization										261	231	226
Income tax expense (benefit) from continuing operations										79	99	104
Segment income (loss)										223	231	191
Segment Reporting Information Assets [Abstract]
Capital investments, expenditures and acquisitions										686	476	399
Segment assets		7,824				7,478				7,824	7,478	7,050
Intersegment Eliminations [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Revenues										(200)	(125)	(112)
Interest expense										(20)	(12)	(9)
Segment income (loss)											1
Segment Reporting Information Assets [Abstract]
Segment assets		188				188				188	188	188
Intersegment Eliminations [Member] | Duke Energy Ohio [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Segment income (loss)												(1)
Segment Reporting Information Assets [Abstract]
Segment assets		(15)				(12)				(15)	(12)	(9)
Intersegment Eliminations [Member] | Electric Utilities and Infrastructure [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Revenues										31	30	32
Intersegment Eliminations [Member] | Gas Utilities and Infrastructure [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Revenues										93	26	5
Intersegment Eliminations [Member] | Other Segments [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Revenues										76	69	75
Intersegment Eliminations [Member] | Total Reportable Segments [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Revenues										124	56	37
Corporate, Non-Segment [Member] | Other Segments [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Revenues										138	117	135
Interest expense										574	693	393
Depreciation and amortization										131	152	135
Equity in earnings (losses) of unconsolidated affiliates										57	43	76
Income tax expense (benefit) from continuing operations										353	(446)	(262)
Segment income (loss)										(905)	(645)	(299)
Segment Reporting Information Assets [Abstract]
Capital investments, expenditures and acquisitions										175	190	258
Segment assets		2,685				2,443				2,685	2,443	5,373
Corporate, Non-Segment [Member] | Other Segments [Member] | Duke Energy Ohio [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Revenues										42	31	33
Interest expense										1	1	1
Depreciation and amortization											2	1
Income tax expense (benefit) from continuing operations										(20)	(21)	(23)
Segment income (loss)										(30)	(39)	(41)
Segment Reporting Information Assets [Abstract]
Segment assets		$ 66				$ 62				$ 66	$ 62	$ 56

Business Segments (Major Custom

Business Segments (Major Customer Disclosure) (Details) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017USD ($)	Sep. 30, 2017USD ($)	Jun. 30, 2017USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Sep. 30, 2016USD ($)	Jun. 30, 2016USD ($)	Mar. 31, 2016USD ($)	Dec. 31, 2017USD ($)segment	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Revenue, Major Customer [Line Items]
Revenues	$ 5,799	$ 6,482	$ 5,555	$ 5,729	$ 5,577	$ 6,576	$ 5,213	$ 5,377	$ 23,565	$ 22,743	$ 22,371
Duke Energy Progress [Member]
Revenue, Major Customer [Line Items]
Revenues	$ 1,251	$ 1,460	$ 1,199	$ 1,219	$ 1,174	$ 1,583	$ 1,213	$ 1,307	$ 5,129	$ 5,277	$ 5,290
Number of Reportable Segments | segment									1
Major Customer 1 [Member] | Duke Energy Progress [Member]
Revenue, Major Customer [Line Items]
Revenues									$ 521

Business Segments (Schedule of

Business Segments (Schedule of Revenue, By Products and Services) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Revenues	$ 5,799	$ 6,482	$ 5,555	$ 5,729	$ 5,577	$ 6,576	$ 5,213	$ 5,377	$ 23,565	$ 22,743	$ 22,371
Electric Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Revenues									21,300	21,336	21,489
Gas Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Revenues									1,743	875	536
Commercial Renewables [Member]
Segment Reporting Information [Line Items]
Revenues									460	484	286
Total Reportable Segments [Member]
Segment Reporting Information [Line Items]
Revenues									23,503	22,695	22,311
Retail Electric [Member]
Segment Reporting Information [Line Items]
Revenues									18,177	18,338	18,695
Retail Electric [Member] | Electric Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Revenues									18,177	18,338	18,695
Wholesale Electric [Member]
Segment Reporting Information [Line Items]
Revenues									2,479	2,398	2,259
Wholesale Electric [Member] | Electric Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Revenues									2,104	2,095	2,014
Wholesale Electric [Member] | Commercial Renewables [Member]
Segment Reporting Information [Line Items]
Revenues									375	303	245
Retail Natural Gas [Member]
Segment Reporting Information [Line Items]
Revenues									1,732	871	546
Retail Natural Gas [Member] | Gas Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Revenues									1,732	871	546
Other Revenues [Member]
Segment Reporting Information [Line Items]
Revenues									1,239	1,144	848
Other Revenues [Member] | Electric Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Revenues									1,050	933	812
Other Revenues [Member] | Gas Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Revenues									104	30	(5)
Other Revenues [Member] | Commercial Renewables [Member]
Segment Reporting Information [Line Items]
Revenues									85	181	41
Operating Segments [Member] | Electric Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Revenues									21,331	21,366	21,521
Operating Segments [Member] | Gas Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Revenues									1,836	901	541
Operating Segments [Member] | Commercial Renewables [Member]
Segment Reporting Information [Line Items]
Revenues									460	484	286
Operating Segments [Member] | Total Reportable Segments [Member]
Segment Reporting Information [Line Items]
Revenues									$ 23,627	$ 22,751	$ 22,348

Regulatory Matters (Narrative)

Regulatory Matters (Narrative) (Details)	1 Months Ended	3 Months Ended	12 Months Ended
	Dec. 31, 2015USD ($)	Mar. 31, 2018USD ($)	Dec. 31, 2017USD ($)MW	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Jan. 17, 2017USD ($)	Jun. 30, 2016USD ($)
Public Utilities, General Disclosures [Line Items]
Net Asset Percentage Limit			25.00%
Regulatory assets, noncurrent			$ 12,442,000,000	$ 12,878,000,000
Net property, plant and equipment			86,391,000,000	82,520,000,000
Regulatory assets			13,879,000,000	13,901,000,000
Impairment charges			282,000,000	18,000,000	$ 106,000,000
Debt Instrument, Face Amount			6,070,000,000	9,127,000,000
Regulated Revenue			21,177,000,000	21,221,000,000	21,379,000,000
Generation Facilities To Be Retired [Member]
Public Utilities, General Disclosures [Line Items]
Net property, plant and equipment			$ 397,000,000
Capacity (in MW) | MW			1,738
Atlantic Coast Pipeline (ACP) [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage			47.00%
Long-term Purchase Commitment, Period			20 years
Sabal Trail Transmission Pipeline [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage			7.50%
Estimated capital cost			$ 3,200,000,000
Long-term Purchase Commitment, Period			25 years
Constitution Pipeline [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage			24.00%
Estimated Contributions			$ 229,000,000
Regulatory Clause Revenues, under-recovered [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			64,000,000	66,000,000
Accrued Pension And Post Retirement [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			2,249,000,000	2,387,000,000
Retired Generation Facilities [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			480,000,000	534,000,000
NCEMPA deferrals [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			53,000,000	51,000,000
Nuclear asset securitized balance, net [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			1,142,000,000	1,193,000,000
Nuclear Deferral [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			119,000,000	226,000,000
Minimum [Member] | Atlantic Coast Pipeline (ACP) [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost			6,000,000,000
Original estimated capital cost			5,000,000,000
Maximum [Member] | Atlantic Coast Pipeline (ACP) [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost			6,500,000,000
Original estimated capital cost			$ 5,500,000,000
Dominion Resources [Member] | Atlantic Coast Pipeline (ACP) [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage			48.00%
Southern Company Gas [Member] | Atlantic Coast Pipeline (ACP) [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage			5.00%
Enbridge Inc. [Member] | Sabal Trail Transmission Pipeline [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage			50.00%
NextEra Energy [Member] | Sabal Trail Transmission Pipeline [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage			42.50%
Williams Partners L.P. [Member] | Constitution Pipeline [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage			41.00%
Duke Energy Carolinas [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent			$ 2,853,000,000	3,159,000,000
Net property, plant and equipment			27,876,000,000	26,762,000,000
Regulatory assets			3,152,000,000	3,397,000,000
Impairment charges				1,000,000	1,000,000
Debt Instrument, Face Amount			$ 550,000,000	1,600,000,000
Duke Energy Carolinas [Member] | Atlantic Coast Pipeline (ACP) [Member]
Public Utilities, General Disclosures [Line Items]
Long-term Purchase Commitment, Period			20 years
Duke Energy Carolinas [Member] | Accrued Pension And Post Retirement [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			$ 410,000,000	481,000,000
Duke Energy Carolinas [Member] | Retired Generation Facilities [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			29,000,000	39,000,000
Duke Energy Carolinas [Member] | Nuclear Deferral [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			84,000,000	92,000,000
Duke Energy Carolinas [Member] | William States Lee Combined Cycle Facility [Member] | NCEMC [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost of new utility plant, including AFUDC			$ 600,000,000
Joint owner ownership percentage			13.00%
Duke Energy Carolinas [Member] | William State Lee III Nuclear Station [Member]
Public Utilities, General Disclosures [Line Items]
Net property, plant and equipment			$ 558,000,000
Duke Energy Carolinas [Member] | 2017 NC Rate Case [Member] | NCUC [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount			$ 647,000,000
Requested Rate Increase (Decrease), Percentage			13.60%
Duke Energy Carolinas [Member] | 2017 NC Rate Case [Member] | Subsequent Event [Member] | NCUC [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount		$ (290,000,000)
Duke Energy Carolinas [Member] | Advanced Metering Infrastructure Deferral [Member] | PSCSC [Member] | Maximum [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent			$ 45,000,000
Duke Energy Progress [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent			3,507,000,000	3,243,000,000
Net property, plant and equipment			19,101,000,000	18,387,000,000
Regulatory assets			3,859,000,000	3,431,000,000
Impairment charges			19,000,000	1,000,000	5,000,000
Debt Instrument, Face Amount			$ 800,000,000	450,000,000
Duke Energy Progress [Member] | Atlantic Coast Pipeline (ACP) [Member]
Public Utilities, General Disclosures [Line Items]
Long-term Purchase Commitment, Period			20 years
Duke Energy Progress [Member] | Accrued Pension And Post Retirement [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			$ 430,000,000	423,000,000
Duke Energy Progress [Member] | Retired Generation Facilities [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			170,000,000	165,000,000
Duke Energy Progress [Member] | NCEMPA deferrals [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			53,000,000	51,000,000
Duke Energy Progress [Member] | Nuclear Deferral [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			35,000,000	38,000,000
Duke Energy Progress [Member] | Asheville Plant [Member] | Generation Facilities To Be Retired [Member]
Public Utilities, General Disclosures [Line Items]
Net property, plant and equipment			$ 385,000,000	492,000,000
Capacity (in MW) | MW			376
Duke Energy Progress [Member] | Shearon Harris Nuclear Station [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent			$ 47,000,000
Wholesale Debt Return Amortization Period			15 years
Regulatory Noncurrent Asset, Amortization Period			8 years
Duke Energy Progress [Member] | 2017 NC Rate Case [Member] | NCUC [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount			$ 477,000,000
Requested Rate Increase (Decrease), Percentage			14.90%
Requested Rate Increase (Decrease), Amended, Amount			$ 420,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Percentage			13.00%
Requested Return on Equity, Percentage			9.90%
Public Utilities, Requested Equity Capital Structure, Percentage			52.00%
Public Utilities, Requested Debt Capital Structure, Percentage			48.00%
Utilities Operating Expense, Impairments			$ 25,000,000
Duke Energy Progress [Member] | 2017 NC Rate Case Unsettled Amount [Member] | NCUC [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amended, Amount			300,000,000
Duke Energy Progress [Member] | Storm Cost Deferrals [Member] | PSCSC [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			73,000,000
Deferred Storm and Property Reserve Deficiency, Noncurrent			74,000,000
Duke Energy Progress [Member] | Storm Cost Deferrals [Member] | NCUC [Member]
Public Utilities, General Disclosures [Line Items]
Estimated Storm Costs - Capital and Operation Maintenance			116,000,000
Regulatory assets			77,000,000
Duke Energy Progress [Member] | 2016 South Carolina Rate Case Settlement [Member] | PSCSC [Member]
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease) amount by state commission			$ 56,000,000
Approved return on equity percentage amount by state commission			10.10%
Regulatory Noncurrent Asset, Amortization Period			15 years
Duke Energy Progress [Member] | 2016 South Carolina Rate Case Settlement Year 1 Increase [Member] | PSCSC [Member]
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease) amount by state commission			$ 38,000,000
Duke Energy Progress [Member] | 2016 South Carolina Rate Case Settlement Year 2 Increase [Member] | PSCSC [Member]
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease) amount by state commission			18,500,000
Duke Energy Progress [Member] | 2016 South Carolina Rate Case Settlement Year 2 Offset [Member] | PSCSC [Member]
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease) amount by state commission			(18,500,000)
Duke Energy Progress [Member] | Western Carolinas Modernization Plan [Member] | NCUC [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost			893,000,000
Duke Energy Florida [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent			2,503,000,000	2,480,000,000
Net property, plant and equipment			12,783,000,000	11,790,000,000
Regulatory assets			2,892,000,000	2,693,000,000
Impairment charges			138,000,000	6,000,000	7,000,000
Debt Instrument, Face Amount			1,300,000,000	1,894,000,000
Duke Energy Florida [Member] | Accrued Pension And Post Retirement [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			476,000,000	458,000,000
Duke Energy Florida [Member] | Retired Generation Facilities [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			216,000,000	257,000,000
Duke Energy Florida [Member] | Nuclear asset securitized balance, net [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			1,142,000,000	1,193,000,000
Duke Energy Florida [Member] | Nuclear Deferral [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets				96,000,000
Duke Energy Florida [Member] | Citrus County Combined Cycle Facility [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost of new utility plant, including AFUDC			$ 1,500,000,000
Duke Energy Florida [Member] | Crystal River Unit 3 [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Noncurrent Asset, Amortization Period			20 years
Duke Energy Florida [Member] | Crystal River Unit 3 [Member] | ISFSI Projects [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent			$ 113,000,000
Approved return on equity percentage amount by state commission			7.35%
Duke Energy Florida [Member] | Crystal River Unit 3 [Member] | FPSC [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent	$ 1,283,000,000				1,283,000,000
Impairment charges					15,000,000
Duke Energy Florida [Member] | Crystal River Unit 3 [Member] | DEFPF [Member]
Public Utilities, General Disclosures [Line Items]
Debt Instrument, Face Amount							$ 1,294,000,000
Proceeds from Issuance of Debt				1,287,000,000
Duke Energy Florida [Member] | Storm Restoration Cost Recovery [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent			$ 376,000,000
Customers Experiencing Outages			1,300,000
Estimated Storm Costs - Capital and Operation Maintenance			$ 513,000,000
Allowed Storm Reserve			132,000,000
Duke Energy Florida [Member] | 2017 Second Revised and Restated Settlement [Member] | FPSC [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent			75,000,000
Approved rate increase (decrease) amount by state commission			$ 67,000,000
Approved return on equity percentage amount by state commission			9.50%
Regulatory Noncurrent Asset, Amortization Period			15 years
Impairment charges			$ 135,000,000
Duke Energy Florida [Member] | 2017 Second Revised and Restated Settlement [Member] | FPSC [Member] | Regulatory Clause Revenues, under-recovered [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			$ 196,000,000
Regulatory Noncurrent Asset, Amortization Period			24 months
Duke Energy Florida [Member] | Hines Chiller Uprate Project [Member] | FPSC [Member]
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease) amount by state commission			$ 19,000,000
Estimated capital cost			$ 150,000,000
Duke Energy Florida [Member] | Osprey Energy Center Acquisition [Member] | USDOJ [Member]
Public Utilities, General Disclosures [Line Items]
Other Commitment						$ 600,000
Duke Energy Florida [Member] | 2013 FPSC Settlement Agreement [Member]
Public Utilities, General Disclosures [Line Items]
Approved return on equity percentage amount by state commission			10.50%
Duke Energy Florida [Member] | 2013 FPSC Settlement Agreement [Member] | Crystal River Unit 3 [Member] | Original Uprate Project [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent			$ 87,000,000
Regulatory Noncurrent Asset, Amortization Period			7 years
Duke Energy Florida [Member] | Levy Nuclear Project [Member] | Levy Nuclear Station [Member] | FPSC [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount			$ 82,000,000
Duke Energy Ohio [Member]
Public Utilities, General Disclosures [Line Items]
Limit of Total Capital			30.00%
Regulatory assets, noncurrent			$ 445,000,000	520,000,000
Net property, plant and equipment			6,041,000,000	5,547,000,000
Regulatory assets			494,000,000	557,000,000
Impairment charges			1,000,000
Debt Instrument, Face Amount			100,000,000	250,000,000
Regulated Revenue			1,373,000,000	1,410,000,000	1,331,000,000
Duke Energy Ohio [Member] | Accrued Pension And Post Retirement [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			139,000,000	135,000,000
Duke Energy Ohio [Member] | RTO Realignment [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			$ 50,000,000	71,000,000
Approved MVP Proposals			17
MISO estimate of Duke Energy Ohio's MVP obligation			$ 2,700,000,000
Duke Energy Ohio [Member] | Duke Energy Kentucky Rate Case [Member] | KPSC [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount			$ 49,000,000
Requested Rate Increase (Decrease), Percentage			15.00%
Duke Energy Ohio [Member] | Woodsdale Station Fuel System [Member] | KPSC [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost			$ 55,000,000
Duke Energy Ohio [Member] | East Bend Coal Ash Basin Filing [Member] | KPSC [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost			93,000,000
Duke Energy Ohio [Member] | Electric Base Rate Case [Member] | PUCO [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount			$ 15,000,000
Requested Return on Equity, Percentage			10.40%
Duke Energy Ohio [Member] | Electric Base Rate Case [Member] | PUCO [Member] | Minimum [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount			$ (18,000,000)
Requested Return on Equity, Percentage			9.22%
Duke Energy Ohio [Member] | Electric Base Rate Case [Member] | PUCO [Member] | Maximum [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount			$ (29,000,000)
Requested Return on Equity, Percentage			10.24%
Duke Energy Ohio [Member] | Natural Gas Pipeline Extension [Member] | PUCO [Member]
Public Utilities, General Disclosures [Line Items]
Estimated Capital Cost Excluding AFUDC			$ 110,000,000
Duke Energy Ohio [Member] | Accelerated Natural Gas Service Line Replacement Rider | PUCO [Member]
Public Utilities, General Disclosures [Line Items]
Amount of Regulatory Costs Not yet Approved			240,000,000
Duke Energy Ohio [Member] | Energy Efficiency Cost Recovery Program [Member] | PUCO [Member]
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease) amount by state commission			56,000,000
Regulated Revenue	$ 20,000,000
Duke Energy Ohio [Member] | Energy Efficiency Cost Recovery Program [Member] | PUCO [Member] | Maximum [Member]
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease) amount by state commission			38,000,000
Duke Energy Ohio [Member] | Mgp Remediation [Member] | East End Site [Member] | PUCO [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			35,000,000
Duke Energy Ohio [Member] | Advanced Metering Infrastructure Project [Member] | KPSC [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent			6,000,000
Estimated capital cost			$ 49,000,000
Duke Energy Kentucky [Member]
Public Utilities, General Disclosures [Line Items]
Required Equity Capital Structure Percent			35.00%
Duke Energy Indiana [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent			$ 978,000,000	1,073,000,000
Net property, plant and equipment			10,286,000,000	9,924,000,000
Regulatory assets			1,143,000,000	1,222,000,000
Impairment charges			18,000,000	8,000,000	88,000,000
Debt Instrument, Face Amount				500,000,000
Duke Energy Indiana [Member] | Accrued Pension And Post Retirement [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			197,000,000	222,000,000
Duke Energy Indiana [Member] | Retired Generation Facilities [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			65,000,000	73,000,000
Duke Energy Indiana [Member] | Benton County Wind Farm Dispute [Member]
Public Utilities, General Disclosures [Line Items]
Litigation Settlement, Amount Awarded to Other Party			29,000,000
Duke Energy Indiana [Member] | Coal Combustion Residual Plan [Member] | IURC [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount			$ 380,000,000
Federal Mandate Costs Recovered Through Tracker Mechanism			80.00%
Federally Mandated Costs Recovered In Future Rate Case			20.00%
Percentage of Costs Recovered through Existing Rider			60.00%
Percentage Recovered Through Future Rate Case			40.00%
Long-term Debt Rate			4.73%
Duke Energy Indiana [Member] | Coal Combustion Residual Plan [Member] | IURC [Member] | Maximum [Member]
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease) amount by state commission			$ 365,000,000
Duke Energy Indiana [Member] | IGCC Rider Proceeding [Member] | Edwardsport IGCC Plant [Member] | IURC [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			152,000,000
Approved rate increase (decrease) amount by state commission			$ (87,500,000)
Regulatory Noncurrent Asset, Amortization Period			8 years
Legal Fees			$ 5,500,000
Utilities Operating Expense, Other					$ 93,000,000
Duke Energy Indiana [Member] | FERC Transmission Rates [Member] | Federal Energy Regulatory Commission [Member]
Public Utilities, General Disclosures [Line Items]
Approved return on equity percentage amount by state commission			12.38%
Approved Return on Equity Percentage Adder			0.50%
Duke Energy Indiana [Member] | FERC Complaint [Member] | Federal Energy Regulatory Commission [Member]
Public Utilities, General Disclosures [Line Items]
Requested Return on Equity, Percentage			8.67%
Duke Energy Indiana [Member] | FERC Complaint 1 [Member] | Federal Energy Regulatory Commission [Member]
Public Utilities, General Disclosures [Line Items]
Approved return on equity percentage amount by state commission			10.32%
Duke Energy Indiana [Member] | FERC Complaint 2 [Member] | Federal Energy Regulatory Commission [Member]
Public Utilities, General Disclosures [Line Items]
Requested Return on Equity, Percentage			9.70%
Duke Energy Indiana [Member] | Grid Infrastructure Improvement Plan [Member] | IURC [Member]
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease) amount by state commission			$ 1,400,000,000
Approved return on equity percentage amount by state commission			10.00%
Estimated capital cost			$ 1,800,000,000
Duke Energy Indiana [Member] | Advanced Metering Infrastructure Project [Member]
Public Utilities, General Disclosures [Line Items]
Net property, plant and equipment			21,000,000
Impairment charges			22,000,000	8,000,000
Piedmont Natural Gas [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent			283,000,000	373,000,000
Net property, plant and equipment			5,246,000,000	4,814,000,000
Regulatory assets			378,000,000	497,000,000
Impairment charges			7,000,000
Piedmont Natural Gas [Member] | Regulatory Clause Revenues, under-recovered [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			64,000,000	66,000,000
Piedmont Natural Gas [Member] | Accrued Pension And Post Retirement [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			$ 91,000,000	$ 166,000,000
Piedmont Natural Gas [Member] | South Carolina Rate Stabilization Adjustment Filing [Member] | PSCSC [Member]
Public Utilities, General Disclosures [Line Items]
Requested Return on Equity, Percentage			12.60%
Approved return on equity percentage amount by state commission			10.20%
Piedmont Natural Gas [Member] | NCUC IMR Petition Filed October 2017 [Member] | NCUC [Member]
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease) amount by state commission			$ 8,900,000
Piedmont Natural Gas [Member] | NCUC IMR Petition Filed May 2017 [Member] | NCUC [Member]
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease) amount by state commission			11,600,000
Piedmont Natural Gas [Member] | TPUC IMR Petition Filed November 2017 [Member] | TPUC [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount			3,300,000
Requested Rate Increase (Decrease), Amended, Amount			$ 400,000

Regulatory Matters (Schedule of

Regulatory Matters (Schedule of Regulatory Assets and Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Regulatory Assets Liabilities [Line Items]
Regulatory assets	$ 13,879	$ 13,901
Regulatory Assets, Current	1,437	1,023
Regulatory assets, noncurrent	12,442	12,878
Regulatory Liabilities	15,732	7,290
Regulatory Liability, Current	402	409
Regulatory Liability, Noncurrent	15,330	6,881
Costs of Removal [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	5,968	5,613
Asset retirement obligations - nuclear and other [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	806	461
Net regulatory liability related to income taxes [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	8,113
Amounts To Be Refunded to Customers [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	10	45
Storm cost deferrals [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	20	83
Accrued Pension And OPEB [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	146	174
Deferred Fuel and Purchased Power [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	47	192
Other [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	622	722
Asset retirement obligations - coal ash [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	4,025	3,761
Asset retirement obligations - nuclear and other [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	852	684
Accrued Pension And Post Retirement [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	2,249	2,387
Retired Generation Facilities [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	480	534
Debt Fair Value Adjustment [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	1,197	1,313
Net regulatory liability related to income taxes [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets		894
Storm cost deferrals [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	531	153
Nuclear asset securitized balance, net [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	1,142	1,193
Hedge costs deferrals [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	234	217
Derivatives - natural gas supply contracts [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	142	187
Demand Side Management And Energy Efficiency, Asset [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	530	407
Grid Modernization [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	39	65
Vacation accrual [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	213	196
Deferred Fuel and Purchased Power [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	507	156
Nuclear Deferral [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	119	226
Post In Service Carrying Costs And Deferred Operating Expense [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	366	413
Transmission Expansion Obligation [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	46	71
Manufactured Gas Plant [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	91	99
Advanced Metering Infrastructure [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	362	218
NCEMPA deferrals [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	53	51
East Bend deferrals [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	45	32
Deferred pipeline integrity [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	54	36
Amounts due from customers [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	64	66
Other [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	538	542
Duke Energy Carolinas [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	3,152	3,397
Regulatory Assets, Current	299	238
Regulatory assets, noncurrent	2,853	3,159
Regulatory Liabilities	6,357	3,001
Regulatory Liability, Current	126	161
Regulatory Liability, Noncurrent	6,231	2,840
Duke Energy Carolinas [Member] | Costs of Removal [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	2,054	2,015
Duke Energy Carolinas [Member] | Asset retirement obligations - nuclear and other [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	806	461
Duke Energy Carolinas [Member] | Net regulatory liability related to income taxes [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	3,028
Duke Energy Carolinas [Member] | Storm cost deferrals [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	20	22
Duke Energy Carolinas [Member] | Accrued Pension And OPEB [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	44	46
Duke Energy Carolinas [Member] | Deferred Fuel and Purchased Power [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	46	105
Duke Energy Carolinas [Member] | Other [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	359	352
Duke Energy Carolinas [Member] | Asset retirement obligations - coal ash [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	1,645	1,536
Duke Energy Carolinas [Member] | Asset retirement obligations - nuclear and other [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets		9
Duke Energy Carolinas [Member] | Accrued Pension And Post Retirement [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	410	481
Duke Energy Carolinas [Member] | Retired Generation Facilities [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	29	39
Duke Energy Carolinas [Member] | Net regulatory liability related to income taxes [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets		484
Duke Energy Carolinas [Member] | Hedge costs deferrals [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	109	93
Duke Energy Carolinas [Member] | Demand Side Management And Energy Efficiency, Asset [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	210	122
Duke Energy Carolinas [Member] | Vacation accrual [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	83	76
Duke Energy Carolinas [Member] | Deferred Fuel and Purchased Power [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	140
Duke Energy Carolinas [Member] | Nuclear Deferral [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	84	92
Duke Energy Carolinas [Member] | Post In Service Carrying Costs And Deferred Operating Expense [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	35	70
Duke Energy Carolinas [Member] | Advanced Metering Infrastructure [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	185	172
Duke Energy Carolinas [Member] | Other [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	222	223
Progress Energy [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	6,751	6,123
Regulatory Assets, Current	741	401
Regulatory assets, noncurrent	6,010	5,722
Regulatory Liabilities	5,519	2,584
Regulatory Liability, Current	213	189
Regulatory Liability, Noncurrent	5,306	2,395
Progress Energy [Member] | Costs of Removal [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	2,537	2,198
Progress Energy [Member] | Net regulatory liability related to income taxes [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	2,802
Progress Energy [Member] | Storm cost deferrals [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities		60
Progress Energy [Member] | Deferred Fuel and Purchased Power [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	1	81
Progress Energy [Member] | Other [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	179	245
Progress Energy [Member] | Asset retirement obligations - coal ash [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	1,984	1,830
Progress Energy [Member] | Asset retirement obligations - nuclear and other [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	655	569
Progress Energy [Member] | Accrued Pension And Post Retirement [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	906	882
Progress Energy [Member] | Retired Generation Facilities [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	386	422
Progress Energy [Member] | Net regulatory liability related to income taxes [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets		231
Progress Energy [Member] | Storm cost deferrals [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	526	148
Progress Energy [Member] | Nuclear asset securitized balance, net [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	1,142	1,193
Progress Energy [Member] | Hedge costs deferrals [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	94	91
Progress Energy [Member] | Demand Side Management And Energy Efficiency, Asset [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	281	278
Progress Energy [Member] | Vacation accrual [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	42	38
Progress Energy [Member] | Deferred Fuel and Purchased Power [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	349	111
Progress Energy [Member] | Nuclear Deferral [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	35	134
Progress Energy [Member] | Post In Service Carrying Costs And Deferred Operating Expense [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	38	42
Progress Energy [Member] | Advanced Metering Infrastructure [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	150
Progress Energy [Member] | NCEMPA deferrals [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	53	51
Progress Energy [Member] | Other [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	110	103
Duke Energy Progress [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	3,859	3,431
Regulatory Assets, Current	352	188
Regulatory assets, noncurrent	3,507	3,243
Regulatory Liabilities	4,138	2,104
Regulatory Liability, Current	139	158
Regulatory Liability, Noncurrent	3,999	1,946
Duke Energy Progress [Member] | Costs of Removal [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	2,122	1,840
Duke Energy Progress [Member] | Net regulatory liability related to income taxes [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	1,854
Duke Energy Progress [Member] | Deferred Fuel and Purchased Power [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	1	64
Duke Energy Progress [Member] | Other [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	161	200
Duke Energy Progress [Member] | Asset retirement obligations - coal ash [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	1,975	1,822
Duke Energy Progress [Member] | Asset retirement obligations - nuclear and other [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	359	275
Duke Energy Progress [Member] | Accrued Pension And Post Retirement [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	430	423
Duke Energy Progress [Member] | Retired Generation Facilities [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	170	165
Duke Energy Progress [Member] | Net regulatory liability related to income taxes [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets		7
Duke Energy Progress [Member] | Storm cost deferrals [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	150	148
Duke Energy Progress [Member] | Hedge costs deferrals [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	64	66
Duke Energy Progress [Member] | Demand Side Management And Energy Efficiency, Asset [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	264	263
Duke Energy Progress [Member] | Vacation accrual [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	42	38
Duke Energy Progress [Member] | Deferred Fuel and Purchased Power [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	130	24
Duke Energy Progress [Member] | Nuclear Deferral [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	35	38
Duke Energy Progress [Member] | Post In Service Carrying Costs And Deferred Operating Expense [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	38	42
Duke Energy Progress [Member] | Advanced Metering Infrastructure [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	75
Duke Energy Progress [Member] | NCEMPA deferrals [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	53	51
Duke Energy Progress [Member] | Other [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	74	69
Duke Energy Florida [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	2,892	2,693
Regulatory Assets, Current	389	213
Regulatory assets, noncurrent	2,503	2,480
Regulatory Liabilities	1,381	479
Regulatory Liability, Current	74	31
Regulatory Liability, Noncurrent	1,307	448
Duke Energy Florida [Member] | Costs of Removal [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	415	358
Duke Energy Florida [Member] | Net regulatory liability related to income taxes [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	948
Duke Energy Florida [Member] | Storm cost deferrals [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities		60
Duke Energy Florida [Member] | Deferred Fuel and Purchased Power [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities		17
Duke Energy Florida [Member] | Other [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	18	44
Duke Energy Florida [Member] | Asset retirement obligations - coal ash [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	9	8
Duke Energy Florida [Member] | Asset retirement obligations - nuclear and other [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	296	294
Duke Energy Florida [Member] | Accrued Pension And Post Retirement [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	476	458
Duke Energy Florida [Member] | Retired Generation Facilities [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	216	257
Duke Energy Florida [Member] | Net regulatory liability related to income taxes [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets		224
Duke Energy Florida [Member] | Storm cost deferrals [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	376
Duke Energy Florida [Member] | Nuclear asset securitized balance, net [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	1,142	1,193
Duke Energy Florida [Member] | Hedge costs deferrals [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	30	25
Duke Energy Florida [Member] | Demand Side Management And Energy Efficiency, Asset [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	17	15
Duke Energy Florida [Member] | Deferred Fuel and Purchased Power [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	219	87
Duke Energy Florida [Member] | Nuclear Deferral [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets		96
Duke Energy Florida [Member] | Advanced Metering Infrastructure [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	75
Duke Energy Florida [Member] | Other [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	36	36
Duke Energy Ohio [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	494	557
Regulatory Assets, Current	49	37
Regulatory assets, noncurrent	445	520
Regulatory Liabilities	927	257
Regulatory Liability, Current	36	21
Regulatory Liability, Noncurrent	891	236
Duke Energy Ohio [Member] | Costs of Removal [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	189	212
Duke Energy Ohio [Member] | Net regulatory liability related to income taxes [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	688
Duke Energy Ohio [Member] | Accrued Pension And OPEB [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	16	19
Duke Energy Ohio [Member] | Deferred Fuel and Purchased Power [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities		6
Duke Energy Ohio [Member] | Other [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	34	20
Duke Energy Ohio [Member] | Asset retirement obligations - coal ash [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	17	12
Duke Energy Ohio [Member] | Accrued Pension And Post Retirement [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	139	135
Duke Energy Ohio [Member] | Net regulatory liability related to income taxes [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets		63
Duke Energy Ohio [Member] | Storm cost deferrals [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	5	5
Duke Energy Ohio [Member] | Hedge costs deferrals [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	6	7
Duke Energy Ohio [Member] | Demand Side Management And Energy Efficiency, Asset [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	18	6
Duke Energy Ohio [Member] | Grid Modernization [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	39	65
Duke Energy Ohio [Member] | Vacation accrual [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	5	4
Duke Energy Ohio [Member] | Deferred Fuel and Purchased Power [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets		5
Duke Energy Ohio [Member] | Post In Service Carrying Costs And Deferred Operating Expense [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	19	20
Duke Energy Ohio [Member] | Transmission Expansion Obligation [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	50	71
Duke Energy Ohio [Member] | Manufactured Gas Plant [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	91	99
Duke Energy Ohio [Member] | Advanced Metering Infrastructure [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	6
Duke Energy Ohio [Member] | East Bend deferrals [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	45	32
Duke Energy Ohio [Member] | Deferred pipeline integrity [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	12	7
Duke Energy Ohio [Member] | Other [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	42	26
Duke Energy Indiana [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	1,143	1,222
Regulatory Assets, Current	165	149
Regulatory assets, noncurrent	978	1,073
Regulatory Liabilities	1,747	788
Regulatory Liability, Current	24	40
Regulatory Liability, Noncurrent	1,723	748
Duke Energy Indiana [Member] | Costs of Removal [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	644	660
Duke Energy Indiana [Member] | Net regulatory liability related to income taxes [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	998
Duke Energy Indiana [Member] | Amounts To Be Refunded to Customers [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	10	45
Duke Energy Indiana [Member] | Accrued Pension And OPEB [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	64	72
Duke Energy Indiana [Member] | Other [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	31	11
Duke Energy Indiana [Member] | Asset retirement obligations - coal ash [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	380	276
Duke Energy Indiana [Member] | Accrued Pension And Post Retirement [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	197	222
Duke Energy Indiana [Member] | Retired Generation Facilities [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	65	73
Duke Energy Indiana [Member] | Net regulatory liability related to income taxes [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets		119
Duke Energy Indiana [Member] | Hedge costs deferrals [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	25	26
Duke Energy Indiana [Member] | Demand Side Management And Energy Efficiency, Asset [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	21
Duke Energy Indiana [Member] | Vacation accrual [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	11	10
Duke Energy Indiana [Member] | Deferred Fuel and Purchased Power [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	18	40
Duke Energy Indiana [Member] | Post In Service Carrying Costs And Deferred Operating Expense [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	274	281
Duke Energy Indiana [Member] | Gasification Services Agreement Buyout Costs [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets		8
Duke Energy Indiana [Member] | Advanced Metering Infrastructure [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	21	46
Duke Energy Indiana [Member] | Other [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	131	121
Piedmont Natural Gas [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	378	497
Regulatory Assets, Current	95	124
Regulatory assets, noncurrent	283	373
Regulatory Liabilities	1,144	608
Regulatory Liability, Current	3	0
Regulatory Liability, Noncurrent	1,141	608
Piedmont Natural Gas [Member] | Costs of Removal [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	544	528
Piedmont Natural Gas [Member] | Net regulatory liability related to income taxes [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	597	80
Piedmont Natural Gas [Member] | Other [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory Liabilities	3	0
Piedmont Natural Gas [Member] | Asset retirement obligations - nuclear and other [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	15	14
Piedmont Natural Gas [Member] | Accrued Pension And Post Retirement [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	91	166
Piedmont Natural Gas [Member] | Derivatives - natural gas supply contracts [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	142	187
Piedmont Natural Gas [Member] | Vacation accrual [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	10	13
Piedmont Natural Gas [Member] | Deferred pipeline integrity [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	42	36
Piedmont Natural Gas [Member] | Amounts due from customers [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	64	66
Piedmont Natural Gas [Member] | Other [Member]
Regulatory Assets Liabilities [Line Items]
Regulatory assets	$ 14	$ 15

Regulatory Matters (Schedule 82

Regulatory Matters (Schedule of MISO Exit fees)(Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Restructuring Reserve [Roll Forward]
Balance, beginning of period	$ 79
Cash reductions	(77)
Balance, end of period	19
Total regulatory assets	13,879	$ 13,901
Duke Energy Ohio [Member]
Restructuring Reserve [Roll Forward]
Total regulatory assets	494	557
Duke Energy Ohio [Member] | RTO Realignment [Member]
Restructuring Reserve [Roll Forward]
Balance, beginning of period	90
Provisions/Adjustments	(20)
Cash reductions	(4)
Balance, end of period	66
Total regulatory assets	$ 50	$ 71

Regulatory Matters (Schedule 83

Regulatory Matters (Schedule of Net Carrying Value Of Facilities) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)MW	Dec. 31, 2016USD ($)
Public Utilities, General Disclosures [Line Items]
Net property, plant and equipment	$ 86,391	$ 82,520
Duke Energy Carolinas [Member]
Public Utilities, General Disclosures [Line Items]
Net property, plant and equipment	27,876	26,762
Progress Energy [Member]
Public Utilities, General Disclosures [Line Items]
Net property, plant and equipment	31,887	30,181
Duke Energy Florida [Member]
Public Utilities, General Disclosures [Line Items]
Net property, plant and equipment	12,783	11,790
Duke Energy Indiana [Member]
Public Utilities, General Disclosures [Line Items]
Net property, plant and equipment	10,286	9,924
Duke Energy Progress [Member]
Public Utilities, General Disclosures [Line Items]
Net property, plant and equipment	$ 19,101	$ 18,387
Generation Facilities To Be Retired [Member]
Public Utilities, General Disclosures [Line Items]
Capacity (in MW) | MW	1,738
Net property, plant and equipment	$ 397
Generation Facilities To Be Retired [Member] | Duke Energy Carolinas [Member] | Allen Steam Station Units 1-3 [Member]
Public Utilities, General Disclosures [Line Items]
Capacity (in MW) | MW	585
Net property, plant and equipment	$ 163
Generation Facilities To Be Retired [Member] | Progress Energy [Member] | Crystal River Units 1 and 2 [Member]
Public Utilities, General Disclosures [Line Items]
Capacity (in MW) | MW	873
Net property, plant and equipment	$ 107
Generation Facilities To Be Retired [Member] | Duke Energy Florida [Member] | Crystal River Units 1 and 2 [Member]
Public Utilities, General Disclosures [Line Items]
Capacity (in MW) | MW	873
Net property, plant and equipment	$ 107
Generation Facilities To Be Retired [Member] | Duke Energy Indiana [Member] | Gallagher Units 2 and 4 [Member]
Public Utilities, General Disclosures [Line Items]
Capacity (in MW) | MW	280
Net property, plant and equipment	$ 127

Commitments and Contingencies84

Commitments and Contingencies (Narrative) (Details) gal in Millions	Sep. 23, 2016USD ($)	Feb. 08, 2016USD ($)	Apr. 22, 2015USD ($)	Mar. 10, 2015USD ($)	Dec. 31, 2017USD ($)plantClaimsreactorT	Dec. 31, 2015USD ($)	Dec. 31, 2016USD ($)	Mar. 31, 2014USD ($)	Feb. 28, 2014galT
Insurance [Abstract]
Insured public liability limit per nuclear incident					$ 13,400,000,000
Excess nuclear liability program coverage					13,000,000,000
Pro rata assessment for each reactor owned for each incident exceeding public liability insurance					$ 127,000,000
Number of licensed nuclear reactors | reactor					102
Annual payment limit to pro rata assessments					$ 19,000,000
Industry aggregate limit					3,200,000,000
Sublimit for non-nuclear terrorist events					$ 1,830,000,000
Insurance Coverage Percentage Initial Weeks					100.00%
Accidental Outage Insurance Coverage Initial Weeks					365 days
Insurance Coverage Percentage Additional Weeks					80.00%
Accidental Outage Insurance Coverage Additional Weeks					770 days
Weeks of Sublimits for Accidental Outage Coverage					728 days
Sublimit accidental outage recovery					$ 328,000,000
Maximum Magnitude of Retroactive Premiums					10
Maximum Period for Retroactive Premium Assessment					6 years
Valuation and Qualifying Accounts [Abstract]
Reserves for legal matters					$ 88,000,000		$ 98,000,000
Progress Energy Merger Shareholder Litigation [Member]
Valuation and Qualifying Accounts [Abstract]
Payments for Legal Settlements			$ 25,000,000
Litigation Settlement Covered by Insurance			$ 121,000,000
Proceeds from Legal Settlements					$ 20,000,000
Litigation Settlement, Amount Awarded to Other Party				$ 146,000,000
Coal Ash Insurance Coverage Litigation [Member]
Valuation and Qualifying Accounts [Abstract]
Number of NC and SC Plants with Ash Basins | plant					15
NCDEQ State Enforcement Actions [Member]
Valuation and Qualifying Accounts [Abstract]
Facilities with Ash Basins | plant					14
Number of Plants with No Disputed Facts | plant					7
Number of Plants with Disputed Facts | plant					7
Groundwater Contamination Claims [Member]
Valuation and Qualifying Accounts [Abstract]
Goodwill Payment					$ 5,000
Water Bill Stipend Period					25 years
Duke Energy Carolinas [Member]
Insurance [Abstract]
Primary nuclear liability program coverage					$ 450,000,000
Max Retroactive Premium Assessments					146,000,000
Valuation and Qualifying Accounts [Abstract]
Reserves for legal matters					30,000,000		23,000,000
Duke Energy Carolinas [Member] | McGuire Nuclear Station [Member]
Insurance [Abstract]
Sublimit property damage losses					1,500,000,000
Additional nuclear accident limit					1,250,000,000
Accidental outage insurance coverage policy limit					490,000,000
Duke Energy Carolinas [Member] | Catawba Nuclear Station [Member]
Insurance [Abstract]
Sublimit property damage losses					1,500,000,000
Dedicated additional nuclear accident limit					1,250,000,000
Additional Non Nuclear Accident Limit					750,000,000
Accidental outage insurance coverage policy limit					$ 490,000,000
Potential Obligation percentage					100.00%
Duke Energy Carolinas [Member] | Oconee Nuclear Station [Member]
Insurance [Abstract]
Sublimit property damage losses					$ 1,500,000,000
Additional nuclear accident limit					1,250,000,000
Additional Non Nuclear Accident Limit					750,000,000
Accidental outage insurance coverage policy limit					434,000,000
Duke Energy Carolinas [Member] | North Carolina Ash Basins [Member] | Dan River [Member]
Valuation and Qualifying Accounts [Abstract]
Civil Penalty Assessed		$ 6,800,000
Litigation Settlement, Amount Awarded to Other Party	$ 6,000,000
Duke Energy Carolinas [Member] | North Carolina Ash Basins [Member] | Dan River [Member] | Minimum [Member]
Valuation and Qualifying Accounts [Abstract]
Estimated amount of ash released, in tons | T									30,000
Estimated amount of ash basin water released, in gallons | gal									24
Duke Energy Carolinas [Member] | North Carolina Ash Basins [Member] | Dan River [Member] | Maximum [Member]
Valuation and Qualifying Accounts [Abstract]
Estimated amount of ash released, in tons | T									39,000
Estimated amount of ash basin water released, in gallons | gal									27
Duke Energy Carolinas [Member] | Groundwater Contamination Claims [Member]
Valuation and Qualifying Accounts [Abstract]
Reserves for legal matters					19,000,000
Duke Energy Carolinas [Member] | Asbestos Issue [Member]
Valuation and Qualifying Accounts [Abstract]
Asbestos-related injuries and damages reserves					489,000,000		512,000,000
Reinsurance retention policy, excess retention, amount reinsured					797,000,000
Probable insurance recoveries					$ 585,000,000		587,000,000
Duke Energy Carolinas [Member] | Asbestos Issue [Member] | Non Malignant Asbestos Claim [Member]
Valuation and Qualifying Accounts [Abstract]
Loss contingency, pending claims, number | Claims					161
Asbestos-related injuries and damages reserves					$ 42,000,000
Duke Energy Carolinas [Member] | Asbestos Issue [Member] | Malignant Asbestos Claim [Member]
Valuation and Qualifying Accounts [Abstract]
Loss contingency, pending claims, number | Claims					54
Asbestos-related injuries and damages reserves					$ 16,000,000
Progress Energy [Member]
Valuation and Qualifying Accounts [Abstract]
Reserves for legal matters					55,000,000		59,000,000
Duke Energy Progress [Member]
Insurance [Abstract]
Primary nuclear liability program coverage					450,000,000
Max Retroactive Premium Assessments					96,000,000
Valuation and Qualifying Accounts [Abstract]
Reserves for legal matters					13,000,000		14,000,000
Duke Energy Progress [Member] | Robinson Nuclear Station [Member]
Insurance [Abstract]
Sublimit property damage losses					1,500,000,000
Additional nuclear accident limit					1,250,000,000
Accidental outage insurance coverage policy limit					378,000,000
Duke Energy Progress [Member] | Brunswick Nuclear Station [Member]
Insurance [Abstract]
Sublimit property damage losses					1,500,000,000
Additional nuclear accident limit					1,250,000,000
Accidental outage insurance coverage policy limit					462,000,000
Duke Energy Progress [Member] | Shearon Harris Nuclear Station [Member]
Insurance [Abstract]
Sublimit property damage losses					1,500,000,000
Additional nuclear accident limit					1,250,000,000
Accidental outage insurance coverage policy limit					448,000,000
Duke Energy Progress [Member] | Groundwater Contamination Claims [Member]
Valuation and Qualifying Accounts [Abstract]
Reserves for legal matters					4,000,000
Duke Energy Progress [Member] | Spent Nuclear Fuels [Member]
Valuation and Qualifying Accounts [Abstract]
Gain contingency, unrecorded amount					48,000,000
Litigation Settlement, Amount Awarded from Other Party					$ 48,000,000
Duke Energy Progress [Member] | Gypsum Supply Agreements [Member]
Valuation and Qualifying Accounts [Abstract]
Minimum Amount of Gypsum To Be Supplied | T					50,000
Duke Energy Florida [Member]
Insurance [Abstract]
Primary nuclear liability program coverage					$ 450,000,000
Max Retroactive Premium Assessments					1,000,000
Valuation and Qualifying Accounts [Abstract]
Reserves for legal matters					24,000,000		28,000,000
Duke Energy Florida [Member] | Crystal River Unit 3 [Member]
Insurance [Abstract]
Sublimit property damage losses					50,000,000
Duke Energy Florida [Member] | Spent Nuclear Fuels [Member]
Valuation and Qualifying Accounts [Abstract]
Gain contingency, unrecorded amount					25,000,000
Litigation Settlement, Amount Awarded from Other Party					21,000,000
Duke Energy Florida [Member] | Westinghouse Electric Company Litigation [Member]
Valuation and Qualifying Accounts [Abstract]
Gain contingency, unrecorded amount					54,000,000
Loss Contingency, Damages Sought, Original Amount					482,000,000			$ 510,000,000
Loss Contingency, Damages Awarded, Value					30,000,000
Gain Contingency, Dismissed Amount					54,000,000
Loss contingency, damages sought, value					424,000,000
Loss Contingency Damages Awarded and Interest, Value					34,000,000
Duke Energy Florida [Member] | MGP Cost Recovery Action [Member]
Valuation and Qualifying Accounts [Abstract]
Loss contingency, damages sought, value					43,000,000
Duke Energy Ohio [Member]
Valuation and Qualifying Accounts [Abstract]
Reserves for legal matters							4,000,000
Duke Energy Ohio [Member] | Antitrust Lawsuit [Member]
Valuation and Qualifying Accounts [Abstract]
Litigation Settlement, Amount Awarded to Other Party						$ 81,000,000
Litigation Settlement, Expense						$ 81,000,000
Piedmont Natural Gas [Member]
Valuation and Qualifying Accounts [Abstract]
Reserves for legal matters					$ 2,000,000		$ 2,000,000

Commitments and Contingencies85

Commitments and Contingencies (Schedule of Environmental Loss Contingencies)(Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015	Oct. 31, 2015	Oct. 31, 2014
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	$ 98	$ 94		$ 92
Provision/adjustments	8	19		11
Cash reductions	(25)	(15)		(9)
Ending balance	81	98		94
Duke Energy Carolinas [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	10	10		10
Provision/adjustments	3	4		1
Cash reductions	(3)	(4)		(1)
Ending balance	10	10		10
Progress Energy [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	18	17		17
Provision/adjustments	3	7		4
Cash reductions	(6)	(6)		(4)
Ending balance	15	18		17
Duke Energy Progress [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	3	3		5
Provision/adjustments	2	2
Cash reductions	(2)	(2)		(2)
Ending balance	3	3		3
Duke Energy Florida [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	14	14		12
Provision/adjustments	2	4		4
Cash reductions	(4)	(4)		(2)
Ending balance	12	14		14
Duke Energy Ohio [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	59	54		54
Provision/adjustments	3	7		1
Cash reductions	(15)	(2)		(1)
Ending balance	47	59		54
Duke Energy Indiana [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	10	12		10
Provision/adjustments	(4)	1		5
Cash reductions	(1)	(3)		(3)
Ending balance	5	10		$ 12
Piedmont Natural Gas [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	1		$ 1		$ 1
Provision/adjustments	1		0		0	$ 0
Ending balance	2	$ 1	$ 1		$ 1	$ 1
Environmental Reserves [Member]
Disclosure Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	56
Environmental Reserves [Member] | Duke Energy Carolinas [Member]
Disclosure Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	19
Environmental Reserves [Member] | Duke Energy Ohio [Member]
Disclosure Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	30
Environmental Reserves [Member] | Piedmont Natural Gas [Member]
Disclosure Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	$ 2

Commitments and Contingencies86

Commitments and Contingencies (Schedule of Legal Reserves) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Legal Reserves Details [Line Items]
Reserves for legal matters	$ 88	$ 98
Duke Energy Carolinas [Member]
Legal Reserves Details [Line Items]
Reserves for legal matters	30	23
Progress Energy [Member]
Legal Reserves Details [Line Items]
Reserves for legal matters	55	59
Duke Energy Progress [Member]
Legal Reserves Details [Line Items]
Reserves for legal matters	13	14
Duke Energy Florida [Member]
Legal Reserves Details [Line Items]
Reserves for legal matters	24	28
Duke Energy Ohio [Member]
Legal Reserves Details [Line Items]
Reserves for legal matters		4
Piedmont Natural Gas [Member]
Legal Reserves Details [Line Items]
Reserves for legal matters	$ 2	$ 2

Commitments and Contingencies87

Commitments and Contingencies (PurchPower)(Details) - Public Utilities Purchased Power [Member] $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)
Duke Energy Progress [Member]
Unconditional Purchase Obligations [Abstract]
2,018	$ 68
2,019	68
2,020	51
2,021	52
2,022	30
Thereafter	239
Total	$ 508
Duke Energy Progress [Member] | Minimum [Member]
Unconditional Purchase Obligations [Abstract]
Long-term Contract for Purchase of Electric Power, Date of Contract Expiration	2,019
Long-term Contract for Purchase of Electric Power, Share of Plant Output Being Purchased	15.00%
Duke Energy Progress [Member] | Maximum [Member]
Unconditional Purchase Obligations [Abstract]
Long-term Contract for Purchase of Electric Power, Date of Contract Expiration	2,031
Long-term Contract for Purchase of Electric Power, Share of Plant Output Being Purchased	100.00%
Duke Energy Florida [Member]
Unconditional Purchase Obligations [Abstract]
2,018	$ 357
2,019	374
2,020	394
2,021	378
2,022	376
Thereafter	770
Total	$ 2,649
Duke Energy Florida [Member] | Minimum [Member]
Unconditional Purchase Obligations [Abstract]
Long-term Contract for Purchase of Electric Power, Date of Contract Expiration	2,021
Long-term Contract for Purchase of Electric Power, Share of Plant Output Being Purchased	81.00%
Duke Energy Florida [Member] | Maximum [Member]
Unconditional Purchase Obligations [Abstract]
Long-term Contract for Purchase of Electric Power, Date of Contract Expiration	2,043
Long-term Contract for Purchase of Electric Power, Share of Plant Output Being Purchased	100.00%

Commitments and Contingencies88

Commitments and Contingencies (Gas Supply Contracts) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)
Natural Gas Supply and Capacity Contracts [Member]
Long-term Purchase Commitment [Line Items]
2,018	$ 314
2,019	280
2,020	252
2,021	249
2,022	226
Thereafter	1,121
Total	$ 2,442
Maximum [Member] | Pipeline and Storage Capacity Contracts [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Period	19 years
Maximum [Member] | Natural Gas Supply Contract Fixed Payments [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Period	3 years
Maximum [Member] | Natural Gas Supply Contract Commitment [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Period	15 years
Duke Energy Ohio [Member] | Natural Gas Supply and Capacity Contracts [Member]
Long-term Purchase Commitment [Line Items]
2,018	$ 37
2,019	28
2,020	25
2,021	26
2,022	11
Thereafter	3
Total	$ 130
Duke Energy Ohio [Member] | Maximum [Member] | Pipeline and Storage Capacity Contracts [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Period	19 years
Duke Energy Ohio [Member] | Maximum [Member] | Natural Gas Supply Contract Fixed Payments [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Period	3 years
Duke Energy Ohio [Member] | Maximum [Member] | Natural Gas Supply Contract Commitment [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Period	15 years
Piedmont Natural Gas [Member] | Natural Gas Supply and Capacity Contracts [Member]
Long-term Purchase Commitment [Line Items]
2,018	$ 277
2,019	252
2,020	227
2,021	223
2,022	215
Thereafter	1,118
Total	$ 2,312
Piedmont Natural Gas [Member] | Maximum [Member] | Pipeline and Storage Capacity Contracts [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Period	19 years
Piedmont Natural Gas [Member] | Maximum [Member] | Natural Gas Supply Contract Fixed Payments [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Period	3 years
Piedmont Natural Gas [Member] | Maximum [Member] | Natural Gas Supply Contract Commitment [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Period	15 years

Commitments and Contingencies89

Commitments and Contingencies (Future Minimum Payments for Operating and Capital Leases) (Details) - USD ($) $ in Millions	2 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015	Oct. 31, 2015
Operating Leased Assets
Rental expense on operating leases		$ 241	$ 242		$ 313
Operating Leases, Future Minimum Payments Due [Abstract]
2,018		233
2,019		203
2,020		183
2,021		150
2,022		135
Thereafter		882
Total future minimum lease payments		1,786
Capital Leases, Future Minimum Payments Due [Abstract]
2,018		168
2,019		169
2,020		174
2,021		176
2,022		169
Thereafter		745
Minimum annual payments		1,601
Less amount representing interest		(601)
Total		1,000
Duke Energy Carolinas [Member]
Operating Leased Assets
Rental expense on operating leases		44	45		41
Operating Leases, Future Minimum Payments Due [Abstract]
2,018		36
2,019		29
2,020		25
2,021		19
2,022		16
Thereafter		52
Total future minimum lease payments		177
Capital Leases, Future Minimum Payments Due [Abstract]
2,018		13
2,019		13
2,020		13
2,021		8
2,022		8
Thereafter		109
Minimum annual payments		164
Less amount representing interest		(103)
Total		61
Progress Energy [Member]
Operating Leased Assets
Rental expense on operating leases		130	140		230
Operating Leases, Future Minimum Payments Due [Abstract]
2,018		133
2,019		126
2,020		117
2,021		97
2,022		90
Thereafter		525
Total future minimum lease payments		1,088
Capital Leases, Future Minimum Payments Due [Abstract]
2,018		46
2,019		45
2,020		47
2,021		45
2,022		45
Thereafter		323
Minimum annual payments		551
Less amount representing interest		(283)
Total		268
Duke Energy Progress [Member]
Operating Leased Assets
Rental expense on operating leases		75	68		149
Operating Leases, Future Minimum Payments Due [Abstract]
2,018		77
2,019		72
2,020		62
2,021		48
2,022		42
Thereafter		344
Total future minimum lease payments		645
Capital Leases, Future Minimum Payments Due [Abstract]
2,018		21
2,019		20
2,020		21
2,021		22
2,022		21
Thereafter		227
Minimum annual payments		332
Less amount representing interest		(192)
Total		140
Duke Energy Florida [Member]
Operating Leased Assets
Rental expense on operating leases		55	72		81
Operating Leases, Future Minimum Payments Due [Abstract]
2,018		56
2,019		54
2,020		55
2,021		49
2,022		48
Thereafter		181
Total future minimum lease payments		443
Capital Leases, Future Minimum Payments Due [Abstract]
2,018		25
2,019		25
2,020		26
2,021		25
2,022		24
Thereafter		95
Minimum annual payments		220
Less amount representing interest		(91)
Total		129
Duke Energy Ohio [Member]
Operating Leased Assets
Rental expense on operating leases		15	16		13
Operating Leases, Future Minimum Payments Due [Abstract]
2,018		20
2,019		12
2,020		10
2,021		7
2,022		4
Thereafter		5
Total future minimum lease payments		58
Capital Leases, Future Minimum Payments Due [Abstract]
2,018		3
2,019		1
2,020		0
Minimum annual payments		4
Total		4
Duke Energy Indiana [Member]
Operating Leased Assets
Rental expense on operating leases		23	$ 23		$ 20
Operating Leases, Future Minimum Payments Due [Abstract]
2,018		22
2,019		14
2,020		10
2,021		8
2,022		5
Thereafter		7
Total future minimum lease payments		66
Capital Leases, Future Minimum Payments Due [Abstract]
2,018		2
2,019		1
2,020		1
2,021		1
2,022		1
Thereafter		38
Minimum annual payments		44
Less amount representing interest		(33)
Total		11
Piedmont Natural Gas [Member]
Operating Leased Assets
Rental expense on operating leases	$ 1	7		$ 5		$ 5
Operating Leases, Future Minimum Payments Due [Abstract]
2,018		6
2,019		5
2,020		5
2,021		6
2,022		6
Thereafter		16
Total future minimum lease payments		$ 44

Debt and Credit Facilities (Nar

Debt and Credit Facilities (Narrative) (Details)	1 Months Ended	12 Months Ended
	Jan. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Jun. 30, 2017USD ($)	Mar. 31, 2017USD ($)	Feb. 28, 2017USD ($)	Dec. 31, 2016USD ($)	Aug. 01, 2016USD ($)
Debt Instrument [Line Items]
Debt issuances		$ 6,070,000,000				$ 9,127,000,000
Other Debt Matters [Abstract]
Demand notes, maximum amount available for sale		3,000,000,000
Demand notes, maximum amount outstanding		1,500,000,000
Principal amount of demand notes		986,000,000				1,090,000,000
Subsidiary debt guaranteed by parent		650,000,000				762,000,000
Other Loans [Abstract]
Other loans outstanding against cash surrender value of life insurance policies		$ 701,000,000				661,000,000
Maximum [Member]
Restrictive Debt Covenants [Abstract]
Debt to total capitalization percentage, for each borrower		0.65
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Facility Size		$ 8,000,000,000		$ 8,000,000,000	$ 7,500,000,000
June 2017 Three Year Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Facility Size			$ 1,000,000,000
Debt Instrument, Term		3 years
Long-term Line of Credit		$ 500,000,000
Term Loan Proceeds		500,000,000
Subsequent Event [Member]
Debt Instrument [Line Items]
Amount Of Borrowing Capacity Extended With Consenting Lenders	$ 7,650,000,000
Line of credit facility, expiration date	Mar. 16, 2023
Duke Energy Carolinas [Member]
Debt Instrument [Line Items]
Debt issuances		$ 550,000,000				1,600,000,000
Duke Energy Carolinas [Member] | Maximum [Member]
Restrictive Debt Covenants [Abstract]
Debt to total capitalization percentage, for each borrower		0.65
Duke Energy Carolinas [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Facility Size		$ 1,350,000,000
Progress Energy [Member] | Maximum [Member]
Restrictive Debt Covenants [Abstract]
Debt to total capitalization percentage, for each borrower		0.65
Duke Energy Progress [Member]
Debt Instrument [Line Items]
Debt issuances		$ 800,000,000				450,000,000
Other Loans [Abstract]
Other loans outstanding against cash surrender value of life insurance policies		$ 38,000,000				39,000,000
Duke Energy Progress [Member] | Maximum [Member]
Restrictive Debt Covenants [Abstract]
Debt to total capitalization percentage, for each borrower		0.65
Duke Energy Progress [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Facility Size		$ 1,250,000,000
Duke Energy Florida [Member]
Debt Instrument [Line Items]
Debt issuances		$ 1,300,000,000				1,894,000,000
Duke Energy Florida [Member] | Maximum [Member]
Restrictive Debt Covenants [Abstract]
Debt to total capitalization percentage, for each borrower		0.65
Duke Energy Florida [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Facility Size		$ 800,000,000
Duke Energy Ohio [Member]
Debt Instrument [Line Items]
Debt issuances		$ 100,000,000				250,000,000
Duke Energy Ohio [Member] | Maximum [Member]
Restrictive Debt Covenants [Abstract]
Debt to total capitalization percentage, for each borrower		0.65
Duke Energy Ohio [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Facility Size		$ 450,000,000
Duke Energy Indiana [Member]
Debt Instrument [Line Items]
Debt issuances						$ 500,000,000
Duke Energy Indiana [Member] | Maximum [Member]
Restrictive Debt Covenants [Abstract]
Debt to total capitalization percentage, for each borrower		0.65
Duke Energy Indiana [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Facility Size		$ 600,000,000
Piedmont Natural Gas [Member] | Maximum [Member]
Restrictive Debt Covenants [Abstract]
Debt to total capitalization percentage, for each borrower		0.7
Piedmont Natural Gas [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Facility Size		$ 700,000,000			$ 850,000,000
Piedmont Natural Gas [Member] | June 2017 Piedmont Term Loan Facility [Member]
Debt Instrument [Line Items]
Facility Size			$ 250,000,000
Debt Instrument, Term		18 months
Long-term Line of Credit		$ 250,000,000
Term Loan Proceeds		250,000,000
Piedmont Natural Gas [Member]
Debt Instrument [Line Items]
Facility Size							$ 4,900,000,000
USDOJ [Member] | North Carolina Ash Basins [Member] | Duke Energy Carolinas [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Minimum Master Credit Facility Balance required		250,000,000
USDOJ [Member] | North Carolina Ash Basins [Member] | Duke Energy Progress [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Minimum Master Credit Facility Balance required		$ 250,000,000

Debt and Credit Facilities (Sum

Debt and Credit Facilities (Summary of Debt and Related Terms) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Unsecured Debt	$ 20,409,000,000	$ 17,812,000,000
Secured Debt	4,458,000,000	3,909,000,000
First mortgage bonds	23,529,000,000	21,879,000,000
Capital leases	1,000,000,000	1,100,000,000
Tax exempt bonds	941,000,000	1,053,000,000
Notes payable and commercial paper	2,788,000,000	3,112,000,000
Fair value hedge carrying value adjustment	6,000,000	6,000,000
Unamortized debt discount and premium, net	1,582,000,000	1,753,000,000
Unamortized debt issuance costs	(271,000,000)	(242,000,000)
Total debt	54,442,000,000	50,382,000,000
Short-term notes payable and commercial paper	(2,163,000,000)	(2,487,000,000)
Current maturities of long-term debt	(3,244,000,000)	(2,319,000,000)
Total long-term debt	$ 49,035,000,000	$ 45,576,000,000
Weighted-average rate	4.09%	4.07%
Short term obligations classified as long-term debt	$ 937,000,000	$ 972,000,000
Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date Range, Start	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument, Maturity Date Range, End	Dec. 31, 2073	Dec. 31, 2073
Weighted-average rate	4.17%	4.30%
Secured Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date Range, Start	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument, Maturity Date Range, End	Dec. 31, 2037	Dec. 31, 2037
Weighted-average rate	3.15%	2.60%
First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date Range, Start	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument, Maturity Date Range, End	Dec. 31, 2047	Dec. 31, 2046
Weighted-average rate	4.51%	4.61%
Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date Range, Start	Dec. 31, 2018	Dec. 31, 2018
Debt Instrument, Maturity Date Range, End	Dec. 31, 2051	Dec. 31, 2051
Weighted-average rate	4.55%	4.48%
Tax Exempt Bonds [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date Range, Start	Dec. 31, 2019	Dec. 31, 2017
Debt Instrument, Maturity Date Range, End	Dec. 31, 2041	Dec. 31, 2041
Weighted-average rate	3.23%	2.84%
Short term obligations classified as long-term debt	$ 312,000,000	$ 347,000,000
Commercial Paper [Member]
Debt Instrument [Line Items]
Short term obligations classified as long-term debt	$ 625,000,000	$ 625,000,000
Notes Payable And Commercial Paper [Member]
Debt Instrument [Line Items]
Weighted-average rate	1.57%	1.01%
Short term obligations classified as long-term debt	$ 625,000,000	$ 625,000,000
Weighted Average Days to Maturity	14 days	14 days
Parent Company [Member] | Purchase Accounting Adjustments [Member]
Debt Instrument [Line Items]
Unamortized debt issuance costs	$ 47,000,000	$ 53,000,000
Duke Energy Carolinas [Member]
Debt Instrument [Line Items]
Unsecured Debt	1,150,000,000	1,150,000,000
Secured Debt	450,000,000	425,000,000
First mortgage bonds	7,959,000,000	7,410,000,000
Capital leases	61,000,000	22,000,000
Tax exempt bonds	243,000,000	355,000,000
Money pool borrowings	404,000,000	300,000,000
Fair value hedge carrying value adjustment	6,000,000	6,000,000
Unamortized debt discount and premium, net	(19,000,000)	(20,000,000)
Unamortized debt issuance costs	(47,000,000)	(45,000,000)
Total debt	10,207,000,000	9,603,000,000
Short-term money pool borrowings	(104,000,000)
Current maturities of long-term debt	(1,205,000,000)	(116,000,000)
Total long-term debt	8,898,000,000	9,487,000,000
Short term obligations classified as long-term debt	300,000,000	335,000,000
Duke Energy Carolinas [Member] | Tax Exempt Bonds [Member]
Debt Instrument [Line Items]
Short term obligations classified as long-term debt		35,000,000
Duke Energy Carolinas [Member] | Commercial Paper [Member]
Debt Instrument [Line Items]
Short term obligations classified as long-term debt	300,000,000	300,000,000
Progress Energy [Member]
Debt Instrument [Line Items]
Unsecured Debt	3,950,000,000	3,551,000,000
Secured Debt	1,757,000,000	1,819,000,000
First mortgage bonds	11,801,000,000	10,800,000,000
Capital leases	269,000,000	285,000,000
Tax exempt bonds	48,000,000	48,000,000
Money pool borrowings	955,000,000	1,902,000,000
Unamortized debt discount and premium, net	(30,000,000)	(31,000,000)
Unamortized debt issuance costs	(108,000,000)	(104,000,000)
Total debt	18,642,000,000	18,270,000,000
Short-term money pool borrowings	(805,000,000)	(729,000,000)
Current maturities of long-term debt	(771,000,000)	(778,000,000)
Total long-term debt	17,066,000,000	16,763,000,000
Duke Energy Progress [Member]
Debt Instrument [Line Items]
Secured Debt	300,000,000	300,000,000
First mortgage bonds	6,776,000,000	6,425,000,000
Capital leases	139,000,000	142,000,000
Tax exempt bonds	48,000,000	48,000,000
Money pool borrowings	390,000,000	150,000,000
Unamortized debt discount and premium, net	(16,000,000)	(16,000,000)
Unamortized debt issuance costs	(40,000,000)	(38,000,000)
Total debt	7,597,000,000	7,011,000,000
Short-term money pool borrowings	(240,000,000)
Current maturities of long-term debt	(3,000,000)	(452,000,000)
Total long-term debt	7,354,000,000	6,559,000,000
Short term obligations classified as long-term debt	150,000,000	150,000,000
Duke Energy Progress [Member] | Commercial Paper [Member]
Debt Instrument [Line Items]
Short term obligations classified as long-term debt	150,000,000	150,000,000
Duke Energy Progress [Member] | Purchase Accounting Adjustments [Member]
Debt Instrument [Line Items]
Capital leases	81,000,000	98,000,000
Duke Energy Florida [Member]
Debt Instrument [Line Items]
Unsecured Debt	550,000,000	150,000,000
Secured Debt	1,457,000,000	1,519,000,000
First mortgage bonds	5,025,000,000	4,375,000,000
Capital leases	129,000,000	143,000,000
Money pool borrowings		297,000,000
Unamortized debt discount and premium, net	(10,000,000)	(10,000,000)
Unamortized debt issuance costs	(56,000,000)	(52,000,000)
Total debt	7,095,000,000	6,422,000,000
Short-term money pool borrowings		(297,000,000)
Current maturities of long-term debt	(768,000,000)	(326,000,000)
Total long-term debt	6,327,000,000	5,799,000,000
Duke Energy Florida [Member] | Purchase Accounting Adjustments [Member]
Debt Instrument [Line Items]
Capital leases	603,000,000	670,000,000
Duke Energy Ohio [Member]
Debt Instrument [Line Items]
Unsecured Debt	900,000,000	810,000,000
First mortgage bonds	1,100,000,000	1,000,000,000
Capital leases	5,000,000	7,000,000
Tax exempt bonds	77,000,000	77,000,000
Money pool borrowings	54,000,000	41,000,000
Unamortized debt discount and premium, net	(33,000,000)	(28,000,000)
Unamortized debt issuance costs	(7,000,000)	(7,000,000)
Total debt	2,096,000,000	1,900,000,000
Short-term money pool borrowings	(29,000,000)	(16,000,000)
Current maturities of long-term debt	(3,000,000)	(1,000,000)
Total long-term debt	2,064,000,000	1,883,000,000
Short term obligations classified as long-term debt	52,000,000	52,000,000
Duke Energy Ohio [Member] | Tax Exempt Bonds [Member]
Debt Instrument [Line Items]
Short term obligations classified as long-term debt	27,000,000	27,000,000
Duke Energy Ohio [Member] | Commercial Paper [Member]
Debt Instrument [Line Items]
Short term obligations classified as long-term debt	25,000,000	25,000,000
Duke Energy Indiana [Member]
Debt Instrument [Line Items]
Unsecured Debt	411,000,000	415,000,000
First mortgage bonds	2,669,000,000	2,669,000,000
Capital leases	11,000,000	11,000,000
Tax exempt bonds	572,000,000	572,000,000
Money pool borrowings	311,000,000	150,000,000
Unamortized debt discount and premium, net	(9,000,000)	(9,000,000)
Unamortized debt issuance costs	(21,000,000)	(22,000,000)
Total debt	3,944,000,000	3,786,000,000
Short-term money pool borrowings	(161,000,000)	0
Current maturities of long-term debt	(3,000,000)	(3,000,000)
Total long-term debt	3,780,000,000	3,783,000,000
Short term obligations classified as long-term debt	435,000,000	435,000,000
Duke Energy Indiana [Member] | Tax Exempt Bonds [Member]
Debt Instrument [Line Items]
Short term obligations classified as long-term debt	285,000,000	285,000,000
Duke Energy Indiana [Member] | Commercial Paper [Member]
Debt Instrument [Line Items]
Short term obligations classified as long-term debt	150,000,000	150,000,000
Piedmont Natural Gas [Member]
Debt Instrument [Line Items]
Unsecured Debt	2,050,000,000	1,835,000,000
Money pool borrowings	364,000,000
Unamortized debt discount and premium, net	(1,000,000)	(1,000,000)
Unamortized debt issuance costs	(12,000,000)	(13,000,000)
Total debt	2,401,000,000	1,821,000,000
Short-term notes payable and commercial paper		(330,000,000)
Short-term money pool borrowings	(364,000,000)
Current maturities of long-term debt	(250,000,000)	(35,000,000)
Total long-term debt	1,787,000,000	$ 1,786,000,000
Piedmont Natural Gas [Member] | Notes Payable And Commercial Paper [Member]
Debt Instrument [Line Items]
Weighted Average Days to Maturity		8 days
International Energy [Member] | Progress Energy [Member]
Debt Instrument [Line Items]
Money pool borrowings		$ 1,000,000,000
Piedmont Natural Gas [Member] | Purchase Accounting Adjustments [Member]
Debt Instrument [Line Items]
Unamortized debt discount and premium, net	176,000,000	197,000,000
Progress Energy [Member] | Purchase Accounting Adjustments [Member]
Debt Instrument [Line Items]
Unamortized debt discount and premium, net	$ 1,509,000,000	$ 1,653,000,000

Debt and Credit Facilities (S92

Debt and Credit Facilities (Summary of Debt Issuances) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Aug. 01, 2016	Jul. 31, 2016
Debt Instrument [Line Items]
Debt issuances	$ 6,070,000,000	$ 9,127,000,000
Piedmont Natural Gas [Member]
Debt Instrument [Line Items]
Facility Size				$ 4,900,000,000
April 2017 Debt Issuance, 3.364% Coupon [Member]
Debt Instrument [Line Items]
Interest rate	3.364%
April 2017 Debt Issuance, 3.364% Coupon [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt issuances	$ 420,000,000
June 2017 Debt Issuance, 2.100% Coupon [Member]
Debt Instrument [Line Items]
Interest rate	2.10%
June 2017 Debt Issuance, 2.100% Coupon [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt issuances	$ 330,000,000
August 2017 Debt Issuance 2.40% Coupon [Member]
Debt Instrument [Line Items]
Interest rate	2.40%
August 2017 Debt Issuance 2.40% Coupon [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt issuances	$ 500,000,000
August 2017 Debt Issuance, 3.150% Coupon [Member]
Debt Instrument [Line Items]
Interest rate	3.15%
August 2017 Debt Issuance, 3.150% Coupon [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt issuances	$ 750,000,000
August 2017 Debt Issuance, 3.950% Coupon [Member]
Debt Instrument [Line Items]
Interest rate	3.95%
August 2017 Debt Issuance, 3.950% Coupon [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt issuances	$ 500,000,000
December 2017 Debt Issuance, 2.100% Coupon [Member]
Debt Instrument [Line Items]
Interest rate	2.10%
December 2017 Debt Issuance, 2.100% Coupon [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt issuances	$ 400,000,000
February 2017 Debt Issuance, 4.120% Coupon [Member]
Debt Instrument [Line Items]
Interest rate	4.12%
February 2017 Debt Issuance, 4.120% Coupon [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Debt issuances	$ 587,000,000
August 2017 Debt Issuance, 4.110% Coupon [Member]
Debt Instrument [Line Items]
Interest rate	4.11%
August 2017 Debt Issuance, 4.110% Coupon [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Debt issuances	$ 233,000,000
January 2017 Debt Issuance, 1.850% Coupon [Member]
Debt Instrument [Line Items]
Interest rate	1.85%
January 2017 Debt Issuance, 1.850% Coupon [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt issuances	$ 250,000,000
January 2017 Debt Issuance, 3.200% Coupon [Member]
Debt Instrument [Line Items]
Interest rate	3.20%
January 2017 Debt Issuance, 3.200% Coupon [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt issuances	$ 650,000,000
March 2017 Debt Issuance, 3.700% Coupon [Member]
Debt Instrument [Line Items]
Interest rate	3.70%
March 2017 Debt Issuance, 3.700% Coupon [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt issuances	$ 100,000,000
September 2017 Debt Issuance, Floating Rate [Member]
Debt Instrument [Line Items]
Interest rate	1.50%
September 2017 Debt Issuance, Floating Rate [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt issuances	$ 300,000,000
September 2017 Debt Issuance, 3.600% Coupon [Member]
Debt Instrument [Line Items]
Interest rate	3.60%
September 2017 Debt Issuance, 3.600% Coupon [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt issuances	$ 500,000,000
November 2017 Debt Issuance, 3.700% Coupon [Member]
Debt Instrument [Line Items]
Interest rate	3.70%
November 2017 Debt Issuance, 3.700% Coupon [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt issuances	$ 550,000,000
April 2016 Debt Maturing April 2023 [Member]
Debt Instrument [Line Items]
Interest rate		2.875%
April 2016 Debt Maturing April 2023 [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt issuances		$ 350,000,000
August 2016 Debt Maturing September 2021 [Member]
Debt Instrument [Line Items]
Interest rate		1.80%
August 2016 Debt Maturing September 2021 [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt issuances		$ 750,000,000
August 2016 Debt Maturing September 2026 [Member]
Debt Instrument [Line Items]
Interest rate		2.65%
August 2016 Debt Maturing September 2026 [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt issuances		$ 1,500,000,000
August 2016 Debt Maturing September 2046 [Member]
Debt Instrument [Line Items]
Interest rate		3.75%
August 2016 Debt Maturing September 2046 [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt issuances		$ 1,500,000,000
June 2016 Debt Maturing March 2020 [Member]
Debt Instrument [Line Items]
Interest rate		1.196%
June 2016 Debt Maturing March 2020 [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Debt issuances		$ 183,000,000
June 2016 Debt Maturing September 2022 [Member]
Debt Instrument [Line Items]
Interest rate		1.731%
June 2016 Debt Maturing September 2022 [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Debt issuances		$ 150,000,000
June 2016 Debt Maturing September 2029 [Member]
Debt Instrument [Line Items]
Interest rate		2.538%
June 2016 Debt Maturing September 2029 [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Debt issuances		$ 436,000,000
June 2016 Debt Maturing March 2033 [Member]
Debt Instrument [Line Items]
Interest rate		2.858%
June 2016 Debt Maturing March 2033 [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Debt issuances		$ 250,000,000
June 2016 Debt Maturing September 2036 [Member]
Debt Instrument [Line Items]
Interest rate		3.112%
June 2016 Debt Maturing September 2036 [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Debt issuances		$ 275,000,000
Solar Facilities Financing [Member]
Debt Instrument [Line Items]
Fixed credit spread		1.75%
Debt Instrument, Interest Rate, Increase (Decrease)		0.125%
August 2016 Debt Tranche A Maturing June 2034 [Member]
Debt Instrument [Line Items]
Interest rate		2.747%
August 2016 Debt Tranche A Maturing June 2034 [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Debt issuances		$ 228,000,000
August 2016 Debt Tranche A Maturing June 2034 [Member] | Swap [Member]
Debt Instrument [Line Items]
Derivative, Fixed Interest Rate		1.81%
August 2016 Debt Tranche B Maturing June 2020 [Member]
Debt Instrument [Line Items]
Interest rate		2.747%
August 2016 Debt Tranche B Maturing June 2020 [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Debt issuances		$ 105,000,000
August 2016 Debt Tranche B Maturing June 2020 [Member] | Swap [Member]
Debt Instrument [Line Items]
Derivative, Fixed Interest Rate		1.38%
March 2016 Debt Maturing March 2023 [Member]
Debt Instrument [Line Items]
Interest rate		2.50%
March 2016 Debt Maturing March 2023 [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt issuances		$ 500,000,000
March 2016 Debt Maturing March 2046 [Member]
Debt Instrument [Line Items]
Interest rate		3.875%
March 2016 Debt Maturing March 2046 [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt issuances		$ 500,000,000
May 2016 Debt 2 Maturing May 2046 [Member]
Debt Instrument [Line Items]
Interest rate		3.75%
May 2016 Debt 2 Maturing May 2046 [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt issuances		$ 500,000,000
June 2016 Debt Maturing June 2046 [Member]
Debt Instrument [Line Items]
Interest rate		3.70%
June 2016 Debt Maturing June 2046 [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt issuances		$ 250,000,000
September 2016 Debt Maturing October 2046 3.4% [Member]
Debt Instrument [Line Items]
Interest rate		3.40%
September 2016 Debt Maturing October 2046 3.4% [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt issuances		$ 600,000,000
September 2016 Debt Maturing October 2046 3.7%[Member]
Debt Instrument [Line Items]
Interest rate		3.70%
September 2016 Debt Maturing October 2046 3.7%[Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt issuances		$ 450,000,000
November 2016 Debt Maturing December 2026 [Member]
Debt Instrument [Line Items]
Interest rate		2.95%
November 2016 Debt Maturing December 2026 [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt issuances		$ 600,000,000
Parent Company [Member]
Debt Instrument [Line Items]
Debt issuances	2,500,000,000	4,100,000,000
Parent Company [Member] | April 2017 Debt Issuance, 3.364% Coupon [Member]
Debt Instrument [Line Items]
Repayments of Debt	400,000,000
Parent Company [Member] | April 2017 Debt Issuance, 3.364% Coupon [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt issuances	420,000,000
Parent Company [Member] | June 2017 Debt Issuance, 2.100% Coupon [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt issuances	330,000,000
Parent Company [Member] | August 2017 Debt Issuance 2.40% Coupon [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt issuances	500,000,000
Parent Company [Member] | August 2017 Debt Issuance, 3.150% Coupon [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt issuances	750,000,000
Parent Company [Member] | August 2017 Debt Issuance, 3.950% Coupon [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt issuances	500,000,000
Parent Company [Member] | August 2017 Debt Issuances [Member]
Debt Instrument [Line Items]
Repayments of Debt	700,000,000
Parent Company [Member] | April 2016 Debt Maturing April 2023 [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt issuances		350,000,000
Parent Company [Member] | August 2016 Debt Maturing September 2021 [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt issuances		750,000,000
Parent Company [Member] | August 2016 Debt Maturing September 2026 [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt issuances		1,500,000,000
Parent Company [Member] | August 2016 Debt Maturing September 2046 [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt issuances		1,500,000,000
Duke Energy Carolinas [Member]
Debt Instrument [Line Items]
Debt issuances	550,000,000	1,600,000,000
Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Paid	625,000,000	2,000,000,000	$ 401,000,000
Duke Energy Carolinas [Member] | November 2017 Debt Issuance, 3.700% Coupon [Member]
Debt Instrument [Line Items]
Repayments of Debt	400,000,000
Duke Energy Carolinas [Member] | November 2017 Debt Issuance, 3.700% Coupon [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt issuances	550,000,000
Duke Energy Carolinas [Member] | March 2016 Debt Maturing March 2023 [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt issuances		500,000,000
Duke Energy Carolinas [Member] | March 2016 Debt Maturing March 2046 [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt issuances		500,000,000
Duke Energy Carolinas [Member] | November 2016 Debt Maturing December 2026 [Member]
Debt Instrument [Line Items]
Repayments of Debt		350,000,000
Duke Energy Carolinas [Member] | November 2016 Debt Maturing December 2026 [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt issuances		600,000,000
Duke Energy Progress [Member]
Debt Instrument [Line Items]
Debt issuances	800,000,000	450,000,000
Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Paid	124,000,000	300,000,000
Duke Energy Progress [Member] | September 2017 Debt Issuances [Member]
Debt Instrument [Line Items]
Repayments of Debt	200,000,000
Duke Energy Progress [Member] | September 2017 Debt Issuance, Floating Rate [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt issuances	300,000,000
Duke Energy Progress [Member] | September 2017 Debt Issuance, 3.600% Coupon [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt issuances	500,000,000
Duke Energy Progress [Member] | September 2016 Debt Maturing October 2046 3.7%[Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt issuances		450,000,000
Duke Energy Florida [Member]
Debt Instrument [Line Items]
Debt issuances	1,300,000,000	1,894,000,000
Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Paid		775,000,000	$ 350,000,000
Duke Energy Florida [Member] | December 2017 Debt Issuance, 2.100% Coupon [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt issuances	400,000,000
Duke Energy Florida [Member] | January 2017 Issuance First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Repayments of Debt	250,000,000
Duke Energy Florida [Member] | January 2017 Debt Issuance, 1.850% Coupon [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt issuances	250,000,000
Duke Energy Florida [Member] | January 2017 Debt Issuance, 3.200% Coupon [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt issuances	650,000,000
Duke Energy Florida [Member] | June 2016 Debt Maturing March 2020 [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Debt issuances		183,000,000
Duke Energy Florida [Member] | June 2016 Debt Maturing September 2022 [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Debt issuances		150,000,000
Duke Energy Florida [Member] | June 2016 Debt Maturing September 2029 [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Debt issuances		436,000,000
Duke Energy Florida [Member] | June 2016 Debt Maturing March 2033 [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Debt issuances		250,000,000
Duke Energy Florida [Member] | June 2016 Debt Maturing September 2036 [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Debt issuances		275,000,000
Duke Energy Florida [Member] | September 2016 Debt Maturing October 2046 3.4% [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt issuances		600,000,000
Duke Energy Florida [Member] | DEFPF [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Paid		649,000,000
Duke Energy Ohio [Member]
Debt Instrument [Line Items]
Debt issuances	100,000,000	250,000,000
Duke Energy Ohio [Member] | March 2017 Debt Issuance, 3.700% Coupon [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt issuances	100,000,000
Duke Energy Ohio [Member] | June 2016 Debt Maturing June 2046 [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt issuances		250,000,000
Duke Energy Indiana [Member]
Debt Instrument [Line Items]
Debt issuances		500,000,000
Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Paid	$ 300,000,000	149,000,000
Duke Energy Indiana [Member] | May 2016 Debt Maturing May 2046 [Member]
Debt Instrument [Line Items]
Repayments of Debt		325,000,000
Duke Energy Indiana [Member] | May 2016 Debt 2 Maturing May 2046 [Member]
Debt Instrument [Line Items]
Repayments of Debt		150,000,000
Duke Energy Indiana [Member] | May 2016 Debt 2 Maturing May 2046 [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt issuances		$ 500,000,000
Piedmont Natural Gas [Member] | July 2016 Debt Issuance 3.640% Coupon [Member]
Debt Instrument [Line Items]
Debt issuances					$ 300,000,000
Interest rate					3.64%
Fixed credit spread	0.25%
Piedmont Natural Gas [Member] | July 2016 Debt Issuance 3.640% Coupon [Member] | Debt Instrument, Redemption, Period One [Member]
Debt Instrument [Line Items]
Debt Instrument, Redemption Period, Start Date	Jul. 28, 2016
Debt Instrument, Redemption Period, End Date	Apr. 30, 2046
Debt Instrument, Redemption Price, Percentage	100.00%
Piedmont Natural Gas [Member] | July 2016 Debt Issuance 3.640% Coupon [Member] | Debt Instrument, Redemption, Period Two [Member]
Debt Instrument [Line Items]
Fixed credit spread	100.00%
Debt Instrument, Redemption Period, Start Date	May 1, 2046
Debt Instrument, Redemption Period, End Date	Oct. 31, 2046

Debt and Credit Facilities (Ann

Debt and Credit Facilities (Annual Maturities) (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Current Maturities Of Long Term Debt [Abstract]
Current maturities of long-term debt	$ 3,244,000,000	$ 2,319,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
2,018	3,244,000,000
2,019	3,563,000,000
2,020	3,699,000,000
2,021	3,760,000,000
2,022	3,010,000,000
Thereafter	33,271,000,000
Total long-term debt, including current maturities	50,547,000,000
Other Debt Obligations [Member]
Current Maturities Of Long Term Debt [Abstract]
Current maturities of long-term debt	544,000,000
Purchase Accounting Adjustments [Member]
Long-term Debt, Fiscal Year Maturity [Abstract]
Purchase accounting adjustments	$ (1,732,000,000)
Parent Company [Member] | Unsecured Debt Maturing June 2018, 6.250% Coupon [Member] | Unsecured Debt [Member]
Current Maturities Of Long Term Debt [Abstract]
Interest rate	6.25%
Current maturities of long-term debt	$ 250,000,000
Parent Company [Member] | Unsecured Debt Maturing June 2018, 2.100% Coupon [Member] | Unsecured Debt [Member]
Current Maturities Of Long Term Debt [Abstract]
Interest rate	2.10%
Current maturities of long-term debt	$ 500,000,000
Duke Energy Carolinas [Member]
Current Maturities Of Long Term Debt [Abstract]
Current maturities of long-term debt	1,205,000,000	116,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
2,018	1,205,000,000
2,019	6,000,000
2,020	906,000,000
2,021	502,000,000
2,022	302,000,000
Thereafter	7,182,000,000
Total long-term debt, including current maturities	$ 10,103,000,000
Duke Energy Carolinas [Member] | First Mortgage Bonds Maturing January 2018, 5.250% Coupon [Member] | First Mortgage Bonds [Member]
Current Maturities Of Long Term Debt [Abstract]
Interest rate	5.25%
Current maturities of long-term debt	$ 400,000,000
Duke Energy Carolinas [Member] | First Mortgage Bonds Maturing April 2018, 5.100% Coupon [Member] | First Mortgage Bonds [Member]
Current Maturities Of Long Term Debt [Abstract]
Interest rate	5.10%
Current maturities of long-term debt	$ 300,000,000
Duke Energy Carolinas [Member] | First Mortgage Bonds Maturing November 2018 7.000% Coupon [Member] | First Mortgage Bonds [Member]
Current Maturities Of Long Term Debt [Abstract]
Interest rate	7.00%
Current maturities of long-term debt	$ 500,000,000
Progress Energy [Member]
Current Maturities Of Long Term Debt [Abstract]
Current maturities of long-term debt	771,000,000	778,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
2,018	771,000,000
2,019	2,191,000,000
2,020	871,000,000
2,021	1,472,000,000
2,022	1,176,000,000
Thereafter	11,356,000,000
Total long-term debt, including current maturities	17,837,000,000
Duke Energy Progress [Member]
Current Maturities Of Long Term Debt [Abstract]
Current maturities of long-term debt	3,000,000	452,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
2,018	3,000,000
2,019	903,000,000
2,020	304,000,000
2,021	602,000,000
2,022	653,000,000
Thereafter	4,892,000,000
Total long-term debt, including current maturities	7,357,000,000
Duke Energy Florida [Member]
Current Maturities Of Long Term Debt [Abstract]
Current maturities of long-term debt	768,000,000	326,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
2,018	768,000,000
2,019	490,000,000
2,020	568,000,000
2,021	371,000,000
2,022	74,000,000
Thereafter	4,824,000,000
Total long-term debt, including current maturities	$ 7,095,000,000
Duke Energy Florida [Member] | First Mortgage Bonds Maturing June 2018, 5.650% Coupon [Member] | First Mortgage Bonds [Member]
Current Maturities Of Long Term Debt [Abstract]
Interest rate	5.65%
Current maturities of long-term debt	$ 500,000,000
Duke Energy Ohio [Member]
Current Maturities Of Long Term Debt [Abstract]
Current maturities of long-term debt	3,000,000	1,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
2,018	3,000,000
2,019	548,000,000
2,021	48,000,000
2,022	23,000,000
Thereafter	1,445,000,000
Total long-term debt, including current maturities	2,067,000,000
Duke Energy Indiana [Member]
Current Maturities Of Long Term Debt [Abstract]
Current maturities of long-term debt	3,000,000	3,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
2,018	3,000,000
2,019	61,000,000
2,020	502,000,000
2,021	69,000,000
2,022	243,000,000
Thereafter	2,905,000,000
Total long-term debt, including current maturities	3,783,000,000
Piedmont Natural Gas [Member]
Current Maturities Of Long Term Debt [Abstract]
Current maturities of long-term debt	250,000,000	$ 35,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
2,018	250,000,000
2,021	159,000,000
Thereafter	1,628,000,000
Total long-term debt, including current maturities	$ 2,037,000,000
Piedmont Natural Gas [Member] | Unsecured Debt Maturing December 2018 Variable Rate [Member] | Unsecured Debt [Member]
Current Maturities Of Long Term Debt [Abstract]
Interest rate	2.286%
Current maturities of long-term debt	$ 250,000,000

Debt and Credit Facilities (Sch

Debt and Credit Facilities (Schedule of Line of Credit Facilities) (Details) - USD ($)	Dec. 31, 2017	Mar. 31, 2017	Feb. 28, 2017	Dec. 31, 2016
Line of Credit Facility [Line Items]
Tax exempt bonds	$ (941,000,000)			$ (1,053,000,000)
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Facility Size	8,000,000,000	$ 8,000,000,000	$ 7,500,000,000
Commercial Paper	(1,799,000,000)
Outstanding letters of credit	(63,000,000)
Tax exempt bonds	(81,000,000)
Coal ash set-aside	(500,000,000)
Available capacity	5,557,000,000
Parent Company [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Facility Size	2,850,000,000
Commercial Paper	(561,000,000)
Outstanding letters of credit	(54,000,000)
Available capacity	2,235,000,000
Duke Energy Carolinas [Member]
Line of Credit Facility [Line Items]
Tax exempt bonds	(243,000,000)			(355,000,000)
Duke Energy Carolinas [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Facility Size	1,350,000,000
Commercial Paper	(371,000,000)
Outstanding letters of credit	(4,000,000)
Coal ash set-aside	(250,000,000)
Available capacity	725,000,000
Duke Energy Progress [Member]
Line of Credit Facility [Line Items]
Tax exempt bonds	(48,000,000)			(48,000,000)
Duke Energy Progress [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Facility Size	1,250,000,000
Commercial Paper	(314,000,000)
Outstanding letters of credit	(2,000,000)
Coal ash set-aside	(250,000,000)
Available capacity	684,000,000
Duke Energy Florida [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Facility Size	800,000,000
Outstanding letters of credit	(1,000,000)
Available capacity	799,000,000
Duke Energy Ohio [Member]
Line of Credit Facility [Line Items]
Tax exempt bonds	(77,000,000)			(77,000,000)
Duke Energy Ohio [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Facility Size	450,000,000
Commercial Paper	(45,000,000)
Available capacity	405,000,000
Duke Energy Indiana [Member]
Line of Credit Facility [Line Items]
Tax exempt bonds	(572,000,000)			$ (572,000,000)
Duke Energy Indiana [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Facility Size	600,000,000
Commercial Paper	(260,000,000)
Tax exempt bonds	(81,000,000)
Available capacity	259,000,000
Piedmont Natural Gas [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Facility Size	700,000,000		$ 850,000,000
Commercial Paper	(248,000,000)
Outstanding letters of credit	(2,000,000)
Available capacity	450,000,000
Proceeds Loaned To Subsidiary Registrants [Member] | Parent Company [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Commercial Paper	$ (625,000,000)

Guarantees and Indemnificatio95

Guarantees and Indemnifications(Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Oct. 31, 2017	Dec. 31, 2016
Guarantor Obligations [Line Items]
Unused letters of credit	$ 66
Face value of guarantees	21		$ 13
Atlantic Coast Pipeline [Member]
Guarantor Obligations [Line Items]
Equity Method Investment Line Of Credit Facility Maximum Borrowing Capacity		$ 3,400
Surety Bond [Member]
Guarantor Obligations [Line Items]
Maximum potential amount of future payments associated with guarantees	81
Standby Letters Of Credit [Member]
Guarantor Obligations [Line Items]
Maximum potential amount of future payments associated with guarantees	449
Performance Guarantee [Member]
Guarantor Obligations [Line Items]
Maximum potential of future amounts associated with guarantees with expiration dates	281
Performance Guarantee [Member] | Less Than Wholly Owned Entity [Member]
Guarantor Obligations [Line Items]
Maximum potential amount of future payments associated with guarantees	11
Performance Guarantee [Member] | Third Parties, Unconsolidated Affiliates and Less Than Wholly Owned Consolidated Entities [Member]
Guarantor Obligations [Line Items]
Maximum potential amount of future payments associated with guarantees	326
Financial Guarantee [Member] | Atlantic Coast Pipeline [Member]
Guarantor Obligations [Line Items]
Maximum potential amount of future payments associated with guarantees	$ 312
Guarantee Obligations Maximum Exposure Percentage	47.00%
Spectra Capital [Member] | Performance Guarantee [Member]
Guarantor Obligations [Line Items]
Maximum potential amount of future payments associated with guarantees	$ 205
Progress Energy [Member] | Indemnification Agreement [Member]
Guarantor Obligations [Line Items]
Maximum potential amount of future payments associated with guarantees	$ 89

Joint Ownership of Generating96

Joint Ownership of Generating and Transmission Facilities (Table) (Details) $ in Millions	Dec. 31, 2017USD ($)
Duke Energy Carolinas [Member] | Catawba Nuclear Station (Units 1 and 2) [Member]
Jointly Owned Utility Plant Interests [Line Items]
Ownership interest	19.25%
Property, plant, and equipment	$ 927
Accumulated depreciation	651
Construction work in progress	$ 19
Duke Energy Carolinas [Member] | Lee Combined Combustion Station [Member]
Jointly Owned Utility Plant Interests [Line Items]
Ownership interest	0.00%
Construction work in progress	$ 552
Duke Energy Ohio [Member] | Transmission [Member]
Jointly Owned Utility Plant Interests [Line Items]
Property, plant, and equipment	89
Accumulated depreciation	63
Construction work in progress	$ 1
Duke Energy Indiana [Member] | Gibson Station (Unit 5) [Member]
Jointly Owned Utility Plant Interests [Line Items]
Ownership interest	50.05%
Property, plant, and equipment	$ 348
Accumulated depreciation	162
Construction work in progress	$ 9
Duke Energy Indiana [Member] | Vermillion Generation Station [Member]
Jointly Owned Utility Plant Interests [Line Items]
Ownership interest	62.50%
Property, plant, and equipment	$ 155
Accumulated depreciation	120
Duke Energy Indiana [Member] | Transmission and local facilities [Member]
Jointly Owned Utility Plant Interests [Line Items]
Property, plant, and equipment	4,672
Accumulated depreciation	$ 1,739

Asset Retirement Obligations (R

Asset Retirement Obligations (Recorded on the Balance Sheet) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015	Oct. 31, 2015
Asset Retirement Obligation [Line Items]
Asset Retirement Obligation	$ 10,175	$ 10,611		$ 10,249
Asset Retirement Obligation, Current	689	411
Asset Retirement Obligations, Noncurrent	9,486	10,200
Decommissioning of Nuclear Power Facilities [Member]
Asset Retirement Obligation [Line Items]
Asset Retirement Obligation	5,371
Closure of Ash Impoundments [Member]
Asset Retirement Obligation [Line Items]
Asset Retirement Obligation	4,525
Other [Member]
Asset Retirement Obligation [Line Items]
Asset Retirement Obligation	279
Duke Energy Carolinas [Member]
Asset Retirement Obligation [Line Items]
Asset Retirement Obligation	3,610	3,895		3,918
Asset Retirement Obligation, Current	337	222
Asset Retirement Obligations, Noncurrent	3,273	3,673
Duke Energy Carolinas [Member] | Decommissioning of Nuclear Power Facilities [Member]
Asset Retirement Obligation [Line Items]
Asset Retirement Obligation	1,944
Duke Energy Carolinas [Member] | Closure of Ash Impoundments [Member]
Asset Retirement Obligation [Line Items]
Asset Retirement Obligation	1,629
Duke Energy Carolinas [Member] | Other [Member]
Asset Retirement Obligation [Line Items]
Asset Retirement Obligation	37
Progress Energy [Member]
Asset Retirement Obligation [Line Items]
Asset Retirement Obligation	5,414	5,475		5,369
Asset Retirement Obligation, Current	295	189
Asset Retirement Obligations, Noncurrent	5,119	5,286
Progress Energy [Member] | Decommissioning of Nuclear Power Facilities [Member]
Asset Retirement Obligation [Line Items]
Asset Retirement Obligation	3,246
Progress Energy [Member] | Closure of Ash Impoundments [Member]
Asset Retirement Obligation [Line Items]
Asset Retirement Obligation	2,094
Progress Energy [Member] | Other [Member]
Asset Retirement Obligation [Line Items]
Asset Retirement Obligation	74
Duke Energy Progress [Member]
Asset Retirement Obligation [Line Items]
Asset Retirement Obligation	4,673	4,697		4,567
Asset Retirement Obligation, Current	295	189
Asset Retirement Obligations, Noncurrent	4,378	4,508
Duke Energy Progress [Member] | Decommissioning of Nuclear Power Facilities [Member]
Asset Retirement Obligation [Line Items]
Asset Retirement Obligation	2,564
Duke Energy Progress [Member] | Closure of Ash Impoundments [Member]
Asset Retirement Obligation [Line Items]
Asset Retirement Obligation	2,075
Duke Energy Progress [Member] | Other [Member]
Asset Retirement Obligation [Line Items]
Asset Retirement Obligation	34
Duke Energy Florida [Member]
Asset Retirement Obligation [Line Items]
Asset Retirement Obligation	742	778		802
Asset Retirement Obligations, Noncurrent	742	778
Duke Energy Florida [Member] | Decommissioning of Nuclear Power Facilities [Member]
Asset Retirement Obligation [Line Items]
Asset Retirement Obligation	681
Duke Energy Florida [Member] | Closure of Ash Impoundments [Member]
Asset Retirement Obligation [Line Items]
Asset Retirement Obligation	19
Duke Energy Florida [Member] | Other [Member]
Asset Retirement Obligation [Line Items]
Asset Retirement Obligation	42
Duke Energy Ohio [Member]
Asset Retirement Obligation [Line Items]
Asset Retirement Obligation	84	77		125
Asset Retirement Obligation, Current	3
Asset Retirement Obligations, Noncurrent	81	77
Duke Energy Ohio [Member] | Closure of Ash Impoundments [Member]
Asset Retirement Obligation [Line Items]
Asset Retirement Obligation	39
Duke Energy Ohio [Member] | Other [Member]
Asset Retirement Obligation [Line Items]
Asset Retirement Obligation	45
Duke Energy Indiana [Member]
Asset Retirement Obligation [Line Items]
Asset Retirement Obligation	781	866		$ 525
Asset Retirement Obligation, Current	54
Asset Retirement Obligations, Noncurrent	727	866
Duke Energy Indiana [Member] | Closure of Ash Impoundments [Member]
Asset Retirement Obligation [Line Items]
Asset Retirement Obligation	763
Duke Energy Indiana [Member] | Other [Member]
Asset Retirement Obligation [Line Items]
Asset Retirement Obligation	18
Piedmont Natural Gas [Member]
Asset Retirement Obligation [Line Items]
Asset Retirement Obligation	15	14	$ 14		$ 20
Asset Retirement Obligations, Noncurrent	15	$ 14
Piedmont Natural Gas [Member] | Other [Member]
Asset Retirement Obligation [Line Items]
Asset Retirement Obligation	$ 15

Asset Retirement Obligations (N

Asset Retirement Obligations (NDTF Information)(Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
NDTF Information [Abstract]
Annual funding requirement	$ 14
Decommissioning costs	8,150
Legally restricted NDTF investments, fair value	5,864	$ 5,099
Duke Energy Carolinas [Member]
NDTF Information [Abstract]
Decommissioning costs	3,420
Legally restricted NDTF investments, fair value	3,321	2,882
Progress Energy [Member]
NDTF Information [Abstract]
Annual funding requirement	14
Decommissioning costs	4,730
Legally restricted NDTF investments, fair value	2,543	2,217
Duke Energy Progress [Member]
NDTF Information [Abstract]
Annual funding requirement	14
Decommissioning costs	3,550
Legally restricted NDTF investments, fair value	2,543	$ 2,217
Duke Energy Florida [Member]
NDTF Information [Abstract]
Decommissioning costs	$ 1,180

Asset Retirement Obligations 99

Asset Retirement Obligations (Nuclear Operating Licenses)(Details)	12 Months Ended
	Dec. 31, 2017
Duke Energy Carolinas [Member] | Catawba Units 1 and 2 [Member]
Asset Retirement Obligation [Line Items]
Year of expiration	2,043
Duke Energy Carolinas [Member] | McGuire Unit 1 [Member]
Asset Retirement Obligation [Line Items]
Year of expiration	2,041
Duke Energy Carolinas [Member] | McGuire Unit 2 [Member]
Asset Retirement Obligation [Line Items]
Year of expiration	2,043
Duke Energy Carolinas [Member] | Oconee Units 1 and 2 [Member]
Asset Retirement Obligation [Line Items]
Year of expiration	2,033
Duke Energy Carolinas [Member] | Oconee Unit 3 [Member]
Asset Retirement Obligation [Line Items]
Year of expiration	2,034
Duke Energy Progress [Member] | Brunswick Unit 1 [Member]
Asset Retirement Obligation [Line Items]
Year of expiration	2,036
Duke Energy Progress [Member] | Brunswick Unit 2 [Member]
Asset Retirement Obligation [Line Items]
Year of expiration	2,034
Duke Energy Progress [Member] | Shearon Harris Nuclear Station [Member]
Asset Retirement Obligation [Line Items]
Year of expiration	2,046
Duke Energy Progress [Member] | Robinson Nuclear Station [Member]
Asset Retirement Obligation [Line Items]
Year of expiration	2,030

Asset Retirement Obligations100

Asset Retirement Obligations (Rollforward)(Details) - USD ($) $ in Millions	2 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016
Asset Retirement Obligation [Line Items]
Beginning Balance		$ 10,611	$ 10,249
Acquisitions			22
Accretion expense		435	400
Liabilities settled		(619)	(613)
Liabilities incurred in the current year		51	51
Revisions in estimates of cash flows		(303)	502
Ending Balance	$ 10,611	10,175	10,611
Duke Energy Carolinas [Member]
Asset Retirement Obligation [Line Items]
Beginning Balance		3,895	3,918
Accretion expense		184	187
Liabilities settled		(282)	(287)
Liabilities incurred in the current year		5
Revisions in estimates of cash flows		(192)	77
Ending Balance	3,895	3,610	3,895
Progress Energy [Member]
Asset Retirement Obligation [Line Items]
Beginning Balance		5,475	5,369
Acquisitions			2
Accretion expense		228	230
Liabilities settled		(270)	(272)
Liabilities incurred in the current year			3
Revisions in estimates of cash flows		(19)	143
Ending Balance	5,475	5,414	5,475
Duke Energy Progress [Member]
Asset Retirement Obligation [Line Items]
Beginning Balance		4,697	4,567
Accretion expense		195	194
Liabilities settled		(204)	(212)
Liabilities incurred in the current year			3
Revisions in estimates of cash flows		(15)	145
Ending Balance	4,697	4,673	4,697
Duke Energy Florida [Member]
Asset Retirement Obligation [Line Items]
Beginning Balance		778	802
Acquisitions			2
Accretion expense		33	35
Liabilities settled		(65)	(60)
Revisions in estimates of cash flows		(4)	(1)
Ending Balance	778	742	778
Duke Energy Ohio [Member]
Asset Retirement Obligation [Line Items]
Beginning Balance		77	125
Accretion expense		3	5
Liabilities settled		(7)	(5)
Liabilities incurred in the current year		7
Revisions in estimates of cash flows		4	(48)
Ending Balance	77	84	77
Duke Energy Indiana [Member]
Asset Retirement Obligation [Line Items]
Beginning Balance		866	525
Accretion expense		32	24
Liabilities settled		(49)	(49)
Liabilities incurred in the current year		29	29
Revisions in estimates of cash flows		(97)	337
Ending Balance	866	781	866
Piedmont Natural Gas [Member]
Asset Retirement Obligation [Line Items]
Beginning Balance	14	14		$ 20
Accretion expense		1		1
Liabilities settled	(1)	(8)		(7)
Liabilities incurred in the current year	1	8		6
Revisions in estimates of cash flows				(6)
Ending Balance	$ 14	$ 15	$ 14	$ 14

Property, Plant and Equipmen101

Property, Plant and Equipment (Schedule Of Property, Plant and Equipment) (Details) - USD ($) $ in Millions	2 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015	Oct. 31, 2015
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Land	$ 1,501	$ 1,559	$ 1,501
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	4,184	4,498	4,184
Equipment	1,941	2,122	1,941
Construction in process	6,186	6,995	6,186
Total property, plant and equipment	121,397	127,507	121,397
Generation facilities to be retired, net	529	421	529
Total net property, plant and equipment	82,520	86,391	82,520
Asset Impairment Charges		282	18		$ 106
Capitalized leases	1,355	1,294	1,355
Accumulated amortization on capitalized leases	50	57	50
Capitalized Interest Costs [Abstract]
Capitalized interest		$ 128	100		98
Commercial Renewables [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Asset Impairment Charges			$ 71
Minimum [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Other, estimated useful life, in years		3 years	5 years
Equipment, estimated useful life, years		3 years	3 years
Maximum [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Other, estimated useful life, in years		40 years	40 years
Equipment, estimated useful life, years		55 years	38 years
Nuclear Fuel [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Nuclear fuel	3,572	$ 3,680	$ 3,572
Accumulated depreciation and amortization	(1,922)	(2,113)	(1,922)
Variable Interest Entity, Primary Beneficiary [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Total property, plant and equipment	2,591	3,941	2,591
Accumulated depreciation and amortization	(411)	(598)	(411)
Regulated Operation [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation and amortization	(37,831)	(39,742)	(37,831)
Regulated Operation [Member] | Electric Plant [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Plant - transmission and distribution	89,864	$ 93,687	$ 89,864
Regulated Operation [Member] | Electric Plant [Member] | Minimum [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Plant - transmission and distribution, estimated useful life, in years		8 years	8 years
Regulated Operation [Member] | Electric Plant [Member] | Maximum [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Plant - transmission and distribution, estimated useful life, in years		100 years	100 years
Regulated Operation [Member] | Natural Gas [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Plant - transmission and distribution	7,738	$ 8,292	$ 7,738
Regulated Operation [Member] | Natural Gas [Member] | Minimum [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Plant - transmission and distribution, estimated useful life, in years		12 years	12 years
Regulated Operation [Member] | Natural Gas [Member] | Maximum [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Plant - transmission and distribution, estimated useful life, in years		80 years	67 years
Regulated Operation [Member] | Other Buildings And Improvements [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	1,692	$ 1,936	$ 1,692
Regulated Operation [Member] | Other Buildings And Improvements [Member] | Minimum [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Other, estimated useful life, in years		15 years	15 years
Regulated Operation [Member] | Other Buildings And Improvements [Member] | Maximum [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Other, estimated useful life, in years		100 years	100 years
Nonregulated Operation [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation and amortization	(1,575)	$ (1,795)	$ (1,575)
Nonregulated Operation [Member] | Electric Plant [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Plant - transmission and distribution	4,298	$ 4,273	$ 4,298
Nonregulated Operation [Member] | Electric Plant [Member] | Minimum [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Plant - transmission and distribution, estimated useful life, in years		5 years	5 years
Nonregulated Operation [Member] | Electric Plant [Member] | Maximum [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Plant - transmission and distribution, estimated useful life, in years		30 years	30 years
Nonregulated Operation [Member] | Other Buildings And Improvements [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	421	$ 465	$ 421
Nonregulated Operation [Member] | Other Buildings And Improvements [Member] | Minimum [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Other, estimated useful life, in years		25 years	25 years
Nonregulated Operation [Member] | Other Buildings And Improvements [Member] | Maximum [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Other, estimated useful life, in years		35 years	35 years
Duke Energy Carolinas [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Land	432	$ 467	$ 432
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	904	1,032	904
Equipment	358	402	358
Construction in process	2,324	2,614	2,324
Total property, plant and equipment	41,127	42,939	41,127
Total net property, plant and equipment	26,762	27,876	26,762
Asset Impairment Charges			1		1
Capitalized leases	40	81	40
Accumulated amortization on capitalized leases	9	11	9
Capitalized Interest Costs [Abstract]
Capitalized interest		45	38		38
Duke Energy Carolinas [Member] | Nuclear Fuel [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Nuclear fuel	2,092	2,120	2,092
Accumulated depreciation and amortization	(1,192)	(1,283)	(1,192)
Duke Energy Carolinas [Member] | Regulated Operation [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation and amortization	(14,365)	(15,063)	(14,365)
Duke Energy Carolinas [Member] | Regulated Operation [Member] | Electric Plant [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Plant - transmission and distribution	34,515	35,657	34,515
Duke Energy Carolinas [Member] | Regulated Operation [Member] | Other Buildings And Improvements [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	502	647	502
Progress Energy [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Land	735	767	735
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	1,206	1,311	1,206
Equipment	505	555	505
Construction in process	2,708	3,059	2,708
Total property, plant and equipment	44,864	47,323	44,864
Generation facilities to be retired, net	529	421	529
Total net property, plant and equipment	30,181	31,887	30,181
Asset Impairment Charges		156	7		12
Capitalized leases net of accumulated amortization	288	272	288
Accumulated amortization on capitalized leases	99	114	99
Capitalized Interest Costs [Abstract]
Capitalized interest		45	31		24
Progress Energy [Member] | Nuclear Fuel [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Nuclear fuel	1,480	1,560	1,480
Accumulated depreciation and amortization	(730)	(831)	(730)
Progress Energy [Member] | Regulated Operation [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation and amortization	(15,212)	(15,857)	(15,212)
Progress Energy [Member] | Regulated Operation [Member] | Electric Plant [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Plant - transmission and distribution	37,596	39,419	37,596
Progress Energy [Member] | Regulated Operation [Member] | Other Buildings And Improvements [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	634	652	634
Duke Energy Progress [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Land	393	424	393
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	863	931	863
Equipment	378	416	378
Construction in process	1,329	1,434	1,329
Total property, plant and equipment	28,419	29,583	28,419
Generation facilities to be retired, net	529	421	529
Total net property, plant and equipment	18,387	19,101	18,387
Asset Impairment Charges		19	1		5
Capitalized leases net of accumulated amortization	142	139	142
Accumulated amortization on capitalized leases	9	11	9
Capitalized Interest Costs [Abstract]
Capitalized interest		21	17		20
Duke Energy Progress [Member] | Nuclear Fuel [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Nuclear fuel	1,480	1,560	1,480
Accumulated depreciation and amortization	(730)	(831)	(730)
Duke Energy Progress [Member] | Regulated Operation [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation and amortization	(10,561)	(10,903)	(10,561)
Duke Energy Progress [Member] | Regulated Operation [Member] | Electric Plant [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Plant - transmission and distribution	23,683	24,502	23,683
Duke Energy Progress [Member] | Regulated Operation [Member] | Other Buildings And Improvements [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	293	316	293
Duke Energy Florida [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Land	342	343	342
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	332	370	332
Equipment	127	139	127
Construction in process	1,379	1,625	1,379
Total property, plant and equipment	16,434	17,730	16,434
Total net property, plant and equipment	11,790	12,783	11,790
Asset Impairment Charges		138	6		7
Capitalized leases net of accumulated amortization	146	133	146
Accumulated amortization on capitalized leases	90	103	90
Capitalized Interest Costs [Abstract]
Capitalized interest		24	14		4
Duke Energy Florida [Member] | Regulated Operation [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation and amortization	(4,644)	(4,947)	(4,644)
Duke Energy Florida [Member] | Regulated Operation [Member] | Electric Plant [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Plant - transmission and distribution	13,913	14,917	13,913
Duke Energy Florida [Member] | Regulated Operation [Member] | Other Buildings And Improvements [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	341	336	341
Duke Energy Ohio [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Land	150	134	150
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	172	228	172
Equipment	338	348	338
Construction in process	206	350	206
Total property, plant and equipment	8,126	8,732	8,126
Total net property, plant and equipment	5,547	6,041	5,547
Asset Impairment Charges		1
Capitalized leases	81	80	81
Accumulated amortization on capitalized leases	19	21	19
Capitalized Interest Costs [Abstract]
Capitalized interest		10	8		10
Duke Energy Ohio [Member] | Regulated Operation [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation and amortization	(2,579)	(2,691)	(2,579)
Duke Energy Ohio [Member] | Regulated Operation [Member] | Electric Plant [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Plant - transmission and distribution	4,593	4,870	4,593
Duke Energy Ohio [Member] | Regulated Operation [Member] | Natural Gas [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Plant - transmission and distribution	2,456	2,559	2,456
Duke Energy Ohio [Member] | Regulated Operation [Member] | Other Buildings And Improvements [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	211	243	211
Duke Energy Indiana [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Land	106	111	106
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	226	271	226
Equipment	156	169	156
Construction in process	396	416	396
Total property, plant and equipment	14,241	14,948	14,241
Total net property, plant and equipment	9,924	10,286	9,924
Asset Impairment Charges		18	8		88
Capitalized leases	35	35	35
Accumulated amortization on capitalized leases	8	9	8
Capitalized Interest Costs [Abstract]
Capitalized interest		9	7		$ 6
Duke Energy Indiana [Member] | Regulated Operation [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation and amortization	(4,317)	(4,662)	(4,317)
Duke Energy Indiana [Member] | Regulated Operation [Member] | Electric Plant [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Plant - transmission and distribution	13,160	13,741	13,160
Duke Energy Indiana [Member] | Regulated Operation [Member] | Other Buildings And Improvements [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	197	240	197
Piedmont Natural Gas [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Land	39	41	39
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	235	300	235
Equipment	260	266	260
Construction in process	210	231	210
Total property, plant and equipment	6,174	6,725	6,174
Total net property, plant and equipment	4,814	5,246	4,814
Asset Impairment Charges		7
Capitalized Interest Costs [Abstract]
Capitalized interest	2	12		$ 12		$ 11
Piedmont Natural Gas [Member] | Regulated Operation [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation and amortization	(1,360)	(1,479)	(1,360)
Piedmont Natural Gas [Member] | Regulated Operation [Member] | Natural Gas [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Plant - transmission and distribution	5,282	5,733	5,282
Piedmont Natural Gas [Member] | Regulated Operation [Member] | Other Buildings And Improvements [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	$ 148	154	$ 148
Property, Plant and Equipment [Member] | Commercial Renewables [Member]
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Asset Impairment Charges		$ 58

Property, Plant and Equipmen102

Property, Plant and Equipment (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Asset Impairment Charges	$ 282	$ 18	$ 106
Commercial Renewables [Member]
Property, Plant and Equipment [Line Items]
Asset Impairment Charges		71
Property, Plant and Equipment [Member]
Property, Plant and Equipment [Line Items]
Asset Impairment Charges	58
Finite-Lived Intangible Assets [Member]
Property, Plant and Equipment [Line Items]
Asset Impairment Charges	11
Assets Leased to Others [Member] | Commercial Renewables [Member]
Property, Plant and Equipment [Line Items]
Contingent lease payments	262	$ 216	$ 172
Renewable energy projects	3,153
Accumulated depreciation and amortization	(459)
Wind Project [Member]
Property, Plant and Equipment [Line Items]
Asset Impairment Charges	$ 69

Goodwill and Intangible Asse103

Goodwill and Intangible Assets (Goodwill By Reportable Operating Segment) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Roll Forward]
Goodwill, balance at beginning of period	$ 19,425
Goodwill, Impaired, Accumulated Impairment Loss	(29)
Goodwill, balance at end of period	19,396
Electric Utilities and Infrastructure [Member]
Goodwill [Roll Forward]
Goodwill, balance at beginning of period	17,379
Goodwill, balance at end of period	17,379
Gas Utilities and Infrastructure [Member]
Goodwill [Roll Forward]
Goodwill, balance at beginning of period	1,924
Goodwill, balance at end of period	1,924
Commercial Renewables [Member]
Goodwill [Roll Forward]
Goodwill, balance at beginning of period	122
Goodwill, Impaired, Accumulated Impairment Loss	(29)
Goodwill, balance at end of period	93
Goodwill, Impairment Loss	29
Duke Energy Ohio [Member]
Goodwill [Roll Forward]
Goodwill, balance at beginning of period	920
Goodwill, Impaired, Accumulated Impairment Loss	(216)	$ (216)
Goodwill, balance at end of period	920
Duke Energy Ohio [Member] | Electric Utilities and Infrastructure [Member]
Goodwill [Roll Forward]
Goodwill, balance at beginning of period	596
Goodwill, balance at end of period	596
Duke Energy Ohio [Member] | Gas Utilities and Infrastructure [Member]
Goodwill [Roll Forward]
Goodwill, balance at beginning of period	324
Goodwill, balance at end of period	324
Progress Energy [Member]
Goodwill [Roll Forward]
Goodwill, balance at beginning of period	3,655
Goodwill, balance at end of period	3,655
Piedmont Natural Gas [Member]
Goodwill [Roll Forward]
Goodwill, balance at beginning of period	49
Goodwill, balance at end of period	$ 49

Goodwill and Intangible Asse104

Goodwill and Intangible Assets (Schedule of Intangible Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Asset Impairment Charges	$ 282	$ 18	$ 106
Finite-Lived Intangible Assets, Net [Abstract]
Gross carrying amount	276	271
Accumulated amortization	(46)	(45)
Total intangible assets, net	230	226
Amortization expense	7	6	5
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
2,017	3
2,018	2
2,019	2
2,020	2
2,021	2
Wind Project [Member]
Finite-Lived Intangible Assets [Line Items]
Asset Impairment Charges	69
Emission Allowances [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross carrying amount	19	19
Renewable Energy Certificates [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross carrying amount	148	125
Gas Coal And Power Contracts [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross carrying amount	24	24
Accumulated amortization	(19)	(17)
Renewable Operating and Development Projects [Member]
Finite-Lived Intangible Assets [Line Items]
Asset Impairment Charges	69
Finite-Lived Intangible Assets, Net [Abstract]
Gross carrying amount	79	97
Accumulated amortization	(22)	(23)
Renewable Operating and Development Projects [Member] | Property, Plant and Equipment [Member]
Finite-Lived Intangible Assets [Line Items]
Asset Impairment Charges	58
Renewable Operating and Development Projects [Member] | Finite-Lived Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Asset Impairment Charges	11
Renewable Operating and Development Projects [Member] | Wind Project [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross carrying amount		18
Accumulated amortization		(7)
Other Intangible Assets [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross carrying amount	6	6
Accumulated amortization	(5)	(5)
Duke Energy Carolinas [Member]
Finite-Lived Intangible Assets [Line Items]
Asset Impairment Charges		1	1
Finite-Lived Intangible Assets, Net [Abstract]
Gross carrying amount	39	37
Total intangible assets, net	39	37
Duke Energy Carolinas [Member] | Emission Allowances [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross carrying amount	1	1
Duke Energy Carolinas [Member] | Renewable Energy Certificates [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross carrying amount	38	36
Progress Energy [Member]
Finite-Lived Intangible Assets [Line Items]
Asset Impairment Charges	156	7	12
Finite-Lived Intangible Assets, Net [Abstract]
Gross carrying amount	112	90
Total intangible assets, net	112	90
Progress Energy [Member] | Emission Allowances [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross carrying amount	5	6
Progress Energy [Member] | Renewable Energy Certificates [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross carrying amount	107	84
Duke Energy Progress [Member]
Finite-Lived Intangible Assets [Line Items]
Asset Impairment Charges	19	1	5
Finite-Lived Intangible Assets, Net [Abstract]
Gross carrying amount	109	86
Total intangible assets, net	109	86
Duke Energy Progress [Member] | Emission Allowances [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross carrying amount	2	2
Duke Energy Progress [Member] | Renewable Energy Certificates [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross carrying amount	107	84
Duke Energy Florida [Member]
Finite-Lived Intangible Assets [Line Items]
Asset Impairment Charges	138	6	7
Finite-Lived Intangible Assets, Net [Abstract]
Gross carrying amount	3	4
Total intangible assets, net	3	4
Duke Energy Florida [Member] | Emission Allowances [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross carrying amount	3	4
Duke Energy Ohio [Member]
Finite-Lived Intangible Assets [Line Items]
Asset Impairment Charges	1
Finite-Lived Intangible Assets, Net [Abstract]
Gross carrying amount	3	4
Total intangible assets, net	3	4
Duke Energy Ohio [Member] | Emission Allowances [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross carrying amount	0
Duke Energy Ohio [Member] | Renewable Energy Certificates [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross carrying amount	3	4
Duke Energy Ohio [Member] | Other Intangible Assets [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross carrying amount	0
Accumulated amortization	0
Duke Energy Indiana [Member]
Finite-Lived Intangible Assets [Line Items]
Asset Impairment Charges	18	8	88
Finite-Lived Intangible Assets, Net [Abstract]
Gross carrying amount	37	37
Accumulated amortization	(19)	(17)
Total intangible assets, net	18	20
Amortization expense	1	1	$ 1
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
2,017	1
2,018	0
2,019	0
2,020	0
2,021	0
Duke Energy Indiana [Member] | Emission Allowances [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross carrying amount	13	13
Duke Energy Indiana [Member] | Gas Coal And Power Contracts [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross carrying amount	24	24
Accumulated amortization	(19)	(17)
Piedmont Natural Gas [Member]
Finite-Lived Intangible Assets [Line Items]
Asset Impairment Charges	7
Finite-Lived Intangible Assets, Net [Abstract]
Gross carrying amount	3	3
Accumulated amortization	(3)	(3)
Piedmont Natural Gas [Member] | Other Intangible Assets [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross carrying amount	3	3
Accumulated amortization	$ (3)	$ (3)

Investments in Unconsolidate105

Investments in Unconsolidated Affiliates (Narrative) (Details) - USD ($) $ in Millions	2 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015	Oct. 31, 2015	Oct. 03, 2016
Investments In Unconsolidated Affiliates [Line Items]
Distributions from equity investments		$ 13	$ 31		$ 104
Distributions from equity investments, return of capital		281	1		3
Income (Loss) from Equity Method Investments		119	(15)		69
Asset Impairment Charges		282	18		106
Atlantic Coast Pipeline [Member]
Investments In Unconsolidated Affiliates [Line Items]
Distributions from equity investments, return of capital		265
Electric Utilities and Infrastructure [Member]
Investments In Unconsolidated Affiliates [Line Items]
Income (Loss) from Equity Method Investments		$ 5	5		(2)
Electric Utilities and Infrastructure [Member] | Duke American Transmission Co. [Member]
Investments In Unconsolidated Affiliates [Line Items]
Equity method investment, ownership percentage		50.00%
Electric Utilities and Infrastructure [Member] | Pioneer Transmission [Member]
Investments In Unconsolidated Affiliates [Line Items]
Equity method investment, ownership percentage		50.00%
Gas Utilities and Infrastructure [Member]
Investments In Unconsolidated Affiliates [Line Items]
Income (Loss) from Equity Method Investments		$ 62	19		1
Gas Utilities and Infrastructure [Member] | Atlantic Coast Pipeline [Member]
Investments In Unconsolidated Affiliates [Line Items]
Equity method investment, ownership percentage		47.00%
Commercial Renewables [Member]
Investments In Unconsolidated Affiliates [Line Items]
Income (Loss) from Equity Method Investments		$ (5)	(82)		(6)
Asset Impairment Charges			71
Commercial Renewables [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Investments In Unconsolidated Affiliates [Line Items]
Asset Impairment Charges			71
Commercial Renewables [Member] | Sweetwater IV-V [Member]
Investments In Unconsolidated Affiliates [Line Items]
Equity method investment, ownership percentage		47.00%
Commercial Renewables [Member] | DS Cornerstone [Member]
Investments In Unconsolidated Affiliates [Line Items]
Equity method investment, ownership percentage		50.00%
Other [Member]
Investments In Unconsolidated Affiliates [Line Items]
Income (Loss) from Equity Method Investments		$ 57	$ 43		$ 76
Other [Member] | National Methanol Company [Member]
Investments In Unconsolidated Affiliates [Line Items]
Equity method investment, ownership percentage	25.00%	17.50%	25.00%
Board representation and voting rights, ownership percentage		25.00%
Piedmont Natural Gas [Member]
Investments In Unconsolidated Affiliates [Line Items]
Distributions from equity investments	$ 1	$ 4		$ 26		$ 25
Distributions from equity investments, return of capital	1	2		18		2
Income (Loss) from Equity Method Investments	$ 2	(6)		29		34
Asset Impairment Charges		$ 7
Piedmont Natural Gas [Member] | SouthStar [Member]
Investments In Unconsolidated Affiliates [Line Items]
Equity Method Investment Ownership Percentage Sold							15.00%
Proceeds from Sale of Equity Method Investments				160
Gain on Sale of Investments				81
Income (Loss) from Equity Method Investments				$ 19		$ 19

Investments in Unconsolidate106

Investments in Unconsolidated Affiliates (Investments in Equity Method Unconsolidated Affiliates) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Investments In Unconsolidated Affiliates [Line Items]
Investments in equity method unconsolidated affiliates	$ 1,175	$ 925
Equity in earnings (losses) of unconsolidated affiliates	119	(15)	$ 69
Electric Utilities and Infrastructure [Member]
Investments In Unconsolidated Affiliates [Line Items]
Investments in equity method unconsolidated affiliates	89	93
Equity in earnings (losses) of unconsolidated affiliates	5	5	(2)
Gas Utilities and Infrastructure [Member]
Investments In Unconsolidated Affiliates [Line Items]
Investments in equity method unconsolidated affiliates	763	566
Equity in earnings (losses) of unconsolidated affiliates	62	19	1
Commercial Renewables [Member]
Investments In Unconsolidated Affiliates [Line Items]
Investments in equity method unconsolidated affiliates	190	185
Equity in earnings (losses) of unconsolidated affiliates	(5)	(82)	(6)
Other [Member]
Investments In Unconsolidated Affiliates [Line Items]
Investments in equity method unconsolidated affiliates	133	81
Equity in earnings (losses) of unconsolidated affiliates	$ 57	$ 43	$ 76

Investments in Unconsolidate107

Investments in Unconsolidated Affiliates (Gas Utilities and Infrastructure Investments) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Investments In Unconsolidated Affiliates [Line Items]
Investments in equity method unconsolidated affiliates	$ 1,175	$ 925
Gas Utilities and Infrastructure [Member]
Investments In Unconsolidated Affiliates [Line Items]
Investments in equity method unconsolidated affiliates	$ 763	566
Atlantic Coast Pipeline [Member] | Gas Utilities and Infrastructure [Member]
Investments In Unconsolidated Affiliates [Line Items]
Equity Method Investment, Ownership Percentage	47.00%
Investments in equity method unconsolidated affiliates	$ 397	265
Sabal Trail Transmission Pipeline [Member] | Gas Utilities and Infrastructure [Member]
Investments In Unconsolidated Affiliates [Line Items]
Equity Method Investment, Ownership Percentage	7.50%
Investments in equity method unconsolidated affiliates	$ 219	140
Constitution Pipeline [Member] | Gas Utilities and Infrastructure [Member]
Investments In Unconsolidated Affiliates [Line Items]
Equity Method Investment, Ownership Percentage	24.00%
Investments in equity method unconsolidated affiliates	$ 81	82
Piedmont Natural Gas [Member]
Investments In Unconsolidated Affiliates [Line Items]
Investments in equity method unconsolidated affiliates	$ 61	212
Piedmont Natural Gas [Member] | Cardinal Pipeline Company, LLC [Member] | Gas Utilities and Infrastructure [Member]
Investments In Unconsolidated Affiliates [Line Items]
Equity Method Investment, Ownership Percentage	21.49%
Investments in equity method unconsolidated affiliates	$ 11	16
Piedmont Natural Gas [Member] | Pine Needle LNG Company, LLC [Member] | Gas Utilities and Infrastructure [Member]
Investments In Unconsolidated Affiliates [Line Items]
Equity Method Investment, Ownership Percentage	45.00%
Investments in equity method unconsolidated affiliates	$ 13	16
Piedmont Natural Gas [Member] | Hardy Storage Company, LLC [Member] | Gas Utilities and Infrastructure [Member]
Investments In Unconsolidated Affiliates [Line Items]
Equity Method Investment, Ownership Percentage	50.00%
Investments in equity method unconsolidated affiliates	$ 42	$ 47

Related Party Transactions (Oth

Related Party Transactions (Other Revenue and Expense) (Details) - USD ($) $ in Millions	1 Months Ended	2 Months Ended	12 Months Ended
	Oct. 31, 2016	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015	Oct. 31, 2015
Duke Energy Carolinas [Member] | Corporate Governance And Shared Service Expenses [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party			$ 858	$ 831		$ 914
Duke Energy Carolinas [Member] | Indemnification Coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party			23	22		24
Duke Energy Carolinas [Member] | Joint Dispatch Agreement (JDA) [Member] | Duke Energy Progress [Member]
Related Party Transaction [Line Items]
Related party transaction, other revenues from transactions with related party			49	38		51
Related party transaction, expenses from transactions with related party			145	156		183
Duke Energy Carolinas [Member] | Intercompany Natural Gas Transactions [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party			9	2
Progress Energy [Member] | Corporate Governance And Shared Service Expenses [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party			736	710		712
Progress Energy [Member] | Indemnification Coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party			38	35		38
Progress Energy [Member] | Joint Dispatch Agreement (JDA) [Member] | Duke Energy Carolinas [Member]
Related Party Transaction [Line Items]
Related party transaction, other revenues from transactions with related party			145	156		183
Related party transaction, expenses from transactions with related party			49	38		51
Progress Energy [Member] | Intercompany Natural Gas Transactions [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party			77	19
Duke Energy Progress [Member] | Corporate Governance And Shared Service Expenses [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party			438	397		403
Duke Energy Progress [Member] | Indemnification Coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party			15	14		16
Duke Energy Progress [Member] | Joint Dispatch Agreement (JDA) [Member] | Duke Energy Carolinas [Member]
Related Party Transaction [Line Items]
Related party transaction, other revenues from transactions with related party			145	156		183
Related party transaction, expenses from transactions with related party			49	38		51
Duke Energy Progress [Member] | Intercompany Natural Gas Transactions [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party			77	19
Duke Energy Florida [Member] | Corporate Governance And Shared Service Expenses [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party			298	313		309
Duke Energy Florida [Member] | Indemnification Coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party			23	21		22
Duke Energy Ohio [Member] | Corporate Governance And Shared Service Expenses [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party			363	356		342
Duke Energy Ohio [Member] | Indemnification Coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party			5	5		6
Duke Energy Indiana [Member] | Corporate Governance And Shared Service Expenses [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party			370	366		349
Duke Energy Indiana [Member] | Indemnification Coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party			8	$ 8		$ 9
Piedmont Natural Gas [Member] | Corporate Governance And Shared Service Expenses [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party			50
Piedmont Natural Gas [Member] | Indemnification Coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party			2
Piedmont Natural Gas [Member] | Intercompany Natural Gas Transactions [Member]
Related Party Transaction [Line Items]
Related party transaction, other revenues from transactions with related party	$ 7	$ 14			$ 74		$ 83
Piedmont Natural Gas [Member] | Intercompany Natural Gas Transactions [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, other revenues from transactions with related party			$ 86

Related Party Transactions (Equ

Related Party Transactions (Equity Method Investments) (Details) - Piedmont Natural Gas [Member] - Equity Method Investee [Member] - USD ($) $ in Millions	2 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Oct. 31, 2016	Oct. 31, 2015
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	$ 6	$ 25	$ 29	$ 29
Accounts Payable, Related Parties, Current	2	2
Cardinal Pipeline Company, LLC [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	2	8	9	9
Pine Needle LNG Company, LLC [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	2	8	11	11
Hardy Storage Company, LLC [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	$ 2	$ 9	$ 9	$ 9

Related Party Transactions (Int

Related Party Transactions (Intercompany Income Taxes) (Details) - Affiliated Entity [Member] - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Duke Energy Carolinas [Member]
Related Party Transaction [Line Items]
Accrued Income Taxes, Current	$ 44
Income taxes receivable, current		$ 1
Progress Energy [Member]
Related Party Transaction [Line Items]
Accrued Income Taxes, Current		37
Income taxes receivable, current	168
Duke Energy Progress [Member]
Related Party Transaction [Line Items]
Accrued Income Taxes, Current	21	90
Duke Energy Florida [Member]
Related Party Transaction [Line Items]
Income taxes receivable, current	44	37
Duke Energy Ohio [Member]
Related Party Transaction [Line Items]
Accrued Income Taxes, Current		1
Income taxes receivable, current	22
Duke Energy Indiana [Member]
Related Party Transaction [Line Items]
Accrued Income Taxes, Current	35	3
Piedmont Natural Gas [Member]
Related Party Transaction [Line Items]
Accrued Income Taxes, Current		$ 38
Income taxes receivable, current	$ 7

Derivatives and Hedging (Notion

Derivatives and Hedging (Notional Amounts of Derivative Instruments) (Details) Mcf in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)GWhMcf	Dec. 31, 2016USD ($)GWhMcf	Aug. 31, 2016USD ($)
Interest Rate Contract [Member]
Derivative [Line Items]
Notional Amount	$ 1,587	$ 1,677
Interest Rate Contract [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount	660	750
Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount	$ 927	$ 927
Commodity Contracts [Member] | Electricity [Member]
Derivative [Line Items]
Notional amount, energy measure, in gigawatt-hours | GWh	34	147
Commodity Contracts [Member] | Natural Gas [Member]
Derivative [Line Items]
Notional amount, volume in millions of decatherms | Mcf	770	890
Variable Interest Entity, Primary Beneficiary [Member] | Interest Rate Contract [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount	$ 660	$ 750
Piedmont Natural Gas [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Loss on Interest Rate Derivative Instruments Not Designated as Hedging Instruments		190
Piedmont Natural Gas [Member] | Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount			$ 1,400
Duke Energy Carolinas [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Notional Amount	400	400
Duke Energy Carolinas [Member] | Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount	$ 400	$ 400
Duke Energy Carolinas [Member] | Commodity Contracts [Member] | Natural Gas [Member]
Derivative [Line Items]
Notional amount, volume in millions of decatherms | Mcf	105	91
Progress Energy [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Notional Amount	$ 500	$ 500
Progress Energy [Member] | Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount	$ 500	$ 500
Progress Energy [Member] | Commodity Contracts [Member] | Natural Gas [Member]
Derivative [Line Items]
Notional amount, volume in millions of decatherms | Mcf	183	269
Duke Energy Progress [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Notional Amount	$ 250	$ 250
Duke Energy Progress [Member] | Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount	$ 250	$ 250
Duke Energy Progress [Member] | Commodity Contracts [Member] | Natural Gas [Member]
Derivative [Line Items]
Notional amount, volume in millions of decatherms | Mcf	133	118
Duke Energy Florida [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Notional Amount	$ 250	$ 250
Duke Energy Florida [Member] | Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount	$ 250	$ 250
Duke Energy Florida [Member] | Commodity Contracts [Member] | Natural Gas [Member]
Derivative [Line Items]
Notional amount, volume in millions of decatherms | Mcf	50	151
Duke Energy Ohio [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Notional Amount	$ 27	$ 27
Duke Energy Ohio [Member] | Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount	$ 27	$ 27
Duke Energy Indiana [Member] | Commodity Contracts [Member] | Electricity [Member]
Derivative [Line Items]
Notional amount, energy measure, in gigawatt-hours | GWh	34	147
Duke Energy Indiana [Member] | Commodity Contracts [Member] | Natural Gas [Member]
Derivative [Line Items]
Notional amount, volume in millions of decatherms | Mcf	2	1
Piedmont Natural Gas [Member] | Commodity Contracts [Member] | Natural Gas [Member]
Derivative [Line Items]
Notional amount, volume in millions of decatherms | Mcf	480	529
Commercial Renewables [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount		$ 300
Commercial Renewables [Member] | 4YearInterestRateContract [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount		81
Commercial Renewables [Member] | 18YearInterestRateContract [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount		$ 219

Derivatives and Hedging (Locati

Derivatives and Hedging (Location and Fair Value Amounts of Derivatives Reflected in the Consolidated Balance Sheets) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	$ 51	$ 162
Location and fair value amounts of derivatives (Liability)	230	252
Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	35	111
Other Noncurrent Assets [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	16	51
Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	66	52
Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	164	200
Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	35	140
Location and fair value amounts of derivatives (Liability)	182	209
Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	16	22
Location and fair value amounts of derivatives (Liability)	48	43
Designated as Hedging Instrument [Member] | Interest Rate Contract [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1
Designated as Hedging Instrument [Member] | Interest Rate Contract [Member] | Other Noncurrent Assets [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	15	19
Designated as Hedging Instrument [Member] | Interest Rate Contract [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	29	8
Designated as Hedging Instrument [Member] | Interest Rate Contract [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	6	8
Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	34	108
Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Noncurrent Assets [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	32
Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	36	43
Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	146	166
Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)		3
Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	1	1
Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	12	26
Duke Energy Carolinas [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	2	33
Location and fair value amounts of derivatives (Liability)	35	16
Duke Energy Carolinas [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	2	23
Duke Energy Carolinas [Member] | Other Noncurrent Assets [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)		10
Duke Energy Carolinas [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	31
Duke Energy Carolinas [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	4	16
Duke Energy Carolinas [Member] | Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	2	33
Location and fair value amounts of derivatives (Liability)	10	1
Duke Energy Carolinas [Member] | Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	25	15
Duke Energy Carolinas [Member] | Designated as Hedging Instrument [Member] | Interest Rate Contract [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	25
Duke Energy Carolinas [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	2	23
Duke Energy Carolinas [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Noncurrent Assets [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)		10
Duke Energy Carolinas [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	6
Duke Energy Carolinas [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	4	1
Duke Energy Carolinas [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)		15
Progress Energy [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	3	85
Location and fair value amounts of derivatives (Liability)	36	25
Progress Energy [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	2	64
Progress Energy [Member] | Other Noncurrent Assets [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	21
Progress Energy [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	19	12
Progress Energy [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	17	13
Progress Energy [Member] | Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	3	82
Location and fair value amounts of derivatives (Liability)	28	19
Progress Energy [Member] | Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)		3
Location and fair value amounts of derivatives (Liability)	8	6
Progress Energy [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	2	61
Progress Energy [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Noncurrent Assets [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	21
Progress Energy [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	18	12
Progress Energy [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	10	7
Progress Energy [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)		3
Progress Energy [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	1
Progress Energy [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	7	6
Duke Energy Progress [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	2	46
Location and fair value amounts of derivatives (Liability)	18	7
Duke Energy Progress [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	36
Duke Energy Progress [Member] | Other Noncurrent Assets [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	10
Duke Energy Progress [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	8
Duke Energy Progress [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	10	7
Duke Energy Progress [Member] | Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	2	45
Location and fair value amounts of derivatives (Liability)	12	1
Duke Energy Progress [Member] | Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)		1
Location and fair value amounts of derivatives (Liability)	6	6
Duke Energy Progress [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	35
Duke Energy Progress [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Noncurrent Assets [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	10
Duke Energy Progress [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	8
Duke Energy Progress [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	4	1
Duke Energy Progress [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)		1
Duke Energy Progress [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	6	6
Duke Energy Florida [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	39
Location and fair value amounts of derivatives (Liability)	12	12
Duke Energy Florida [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	28
Duke Energy Florida [Member] | Other Noncurrent Assets [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)		11
Duke Energy Florida [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	10	12
Duke Energy Florida [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	2
Duke Energy Florida [Member] | Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	37
Location and fair value amounts of derivatives (Liability)	10	12
Duke Energy Florida [Member] | Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)		2
Location and fair value amounts of derivatives (Liability)	2
Duke Energy Florida [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	26
Duke Energy Florida [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Noncurrent Assets [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)		11
Duke Energy Florida [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	10	12
Duke Energy Florida [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)		2
Duke Energy Florida [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	2
Duke Energy Ohio [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	5
Location and fair value amounts of derivatives (Liability)	5	6
Duke Energy Ohio [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	4
Duke Energy Ohio [Member] | Other Noncurrent Assets [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)		1
Duke Energy Ohio [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	1	1
Duke Energy Ohio [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	4	5
Duke Energy Ohio [Member] | Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	5
Duke Energy Ohio [Member] | Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	5	6
Duke Energy Ohio [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	4
Duke Energy Ohio [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Noncurrent Assets [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)		1
Duke Energy Ohio [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	1	1
Duke Energy Ohio [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	4	5
Duke Energy Indiana [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	27	16
Location and fair value amounts of derivatives (Liability)		2
Duke Energy Indiana [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	27	16
Duke Energy Indiana [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)		2
Duke Energy Indiana [Member] | Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	27	16
Location and fair value amounts of derivatives (Liability)		2
Duke Energy Indiana [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	27	16
Duke Energy Indiana [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)		2
Piedmont Natural Gas [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	2	3
Location and fair value amounts of derivatives (Liability)	142	187
Piedmont Natural Gas [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	2	3
Piedmont Natural Gas [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	11	35
Piedmont Natural Gas [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	131	152
Piedmont Natural Gas [Member] | Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	2	3
Location and fair value amounts of derivatives (Liability)	142	187
Piedmont Natural Gas [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	2	3
Piedmont Natural Gas [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Noncurrent Assets [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)
Piedmont Natural Gas [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	11	35
Piedmont Natural Gas [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	$ 131	$ 152

Derivatives and Hedging (Schedu

Derivatives and Hedging (Schedule of Offsetting Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Offsetting Assets [Line Items]
Gross amounts recognized	$ 51	$ 162
Net amounts presented on Balance Sheets	51	162
Current Assets, Other [Member]
Offsetting Assets [Line Items]
Gross amounts recognized	35	111
Gross amounts offset		(11)
Net amounts presented on Balance Sheets	35	100
Other Noncurrent Assets [Member]
Offsetting Assets [Line Items]
Gross amounts recognized	16	51
Gross amounts offset		(2)
Net amounts presented on Balance Sheets	16	49
Duke Energy Carolinas [Member]
Offsetting Assets [Line Items]
Gross amounts recognized	2	33
Net amounts presented on Balance Sheets	2	33
Duke Energy Carolinas [Member] | Current Assets, Other [Member]
Offsetting Assets [Line Items]
Gross amounts recognized	2	23
Net amounts presented on Balance Sheets	2	23
Duke Energy Carolinas [Member] | Other Noncurrent Assets [Member]
Offsetting Assets [Line Items]
Gross amounts recognized		10
Gross amounts offset		(1)
Net amounts presented on Balance Sheets		9
Progress Energy [Member]
Offsetting Assets [Line Items]
Gross amounts recognized	3	85
Net amounts presented on Balance Sheets	3	85
Progress Energy [Member] | Current Assets, Other [Member]
Offsetting Assets [Line Items]
Gross amounts recognized	2	64
Gross amounts offset		(11)
Net amounts presented on Balance Sheets	2	53
Progress Energy [Member] | Other Noncurrent Assets [Member]
Offsetting Assets [Line Items]
Gross amounts recognized	1	21
Gross amounts offset		(1)
Net amounts presented on Balance Sheets	1	20
Duke Energy Progress [Member]
Offsetting Assets [Line Items]
Gross amounts recognized	2	46
Net amounts presented on Balance Sheets	2	46
Duke Energy Progress [Member] | Current Assets, Other [Member]
Offsetting Assets [Line Items]
Gross amounts recognized	1	36
Net amounts presented on Balance Sheets	1	36
Duke Energy Progress [Member] | Other Noncurrent Assets [Member]
Offsetting Assets [Line Items]
Gross amounts recognized	1	10
Gross amounts offset		(1)
Net amounts presented on Balance Sheets	1	9
Duke Energy Florida [Member]
Offsetting Assets [Line Items]
Gross amounts recognized	1	39
Net amounts presented on Balance Sheets	1	39
Duke Energy Florida [Member] | Current Assets, Other [Member]
Offsetting Assets [Line Items]
Gross amounts recognized	1	28
Gross amounts offset		(11)
Net amounts presented on Balance Sheets	1	17
Duke Energy Florida [Member] | Other Noncurrent Assets [Member]
Offsetting Assets [Line Items]
Gross amounts recognized		11
Net amounts presented on Balance Sheets		11
Duke Energy Ohio [Member]
Offsetting Assets [Line Items]
Gross amounts recognized	1	5
Net amounts presented on Balance Sheets	1	5
Duke Energy Ohio [Member] | Current Assets, Other [Member]
Offsetting Assets [Line Items]
Gross amounts recognized	1	4
Net amounts presented on Balance Sheets	1	4
Duke Energy Ohio [Member] | Other Noncurrent Assets [Member]
Offsetting Assets [Line Items]
Gross amounts recognized		1
Net amounts presented on Balance Sheets		1
Duke Energy Indiana [Member]
Offsetting Assets [Line Items]
Gross amounts recognized	27	16
Net amounts presented on Balance Sheets	27	16
Duke Energy Indiana [Member] | Current Assets, Other [Member]
Offsetting Assets [Line Items]
Gross amounts recognized	27	16
Net amounts presented on Balance Sheets	27	16
Piedmont Natural Gas [Member]
Offsetting Assets [Line Items]
Gross amounts recognized	2	3
Net amounts presented on Balance Sheets	2	3
Piedmont Natural Gas [Member] | Current Assets, Other [Member]
Offsetting Assets [Line Items]
Gross amounts recognized	2	3
Net amounts presented on Balance Sheets	$ 2	$ 3

Derivatives and Hedging (Sch114

Derivatives and Hedging (Schedule of Offsetting Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Offsetting Liabilities [Line Items]
Gross amounts recognized	$ 230	$ 252
Net amounts presented on Balance Sheets	230	252
Other Current Liabilities [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	66	52
Gross amounts offset	(3)	(11)
Net amounts presented on Balance Sheets	63	41
Other Noncurrent Liabilities [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	164	200
Gross amounts offset	(1)	(2)
Net amounts presented on Balance Sheets	163	198
Duke Energy Carolinas [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	35	16
Net amounts presented on Balance Sheets	35	16
Duke Energy Carolinas [Member] | Other Current Liabilities [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	31
Gross amounts offset	(2)
Net amounts presented on Balance Sheets	29
Duke Energy Carolinas [Member] | Other Noncurrent Liabilities [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	4	16
Gross amounts offset		(1)
Net amounts presented on Balance Sheets	4	15
Progress Energy [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	36	25
Net amounts presented on Balance Sheets	36	25
Progress Energy [Member] | Other Current Liabilities [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	19	12
Gross amounts offset	(2)	(11)
Net amounts presented on Balance Sheets	17	1
Progress Energy [Member] | Other Noncurrent Liabilities [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	17	13
Gross amounts offset	(1)	(1)
Net amounts presented on Balance Sheets	16	12
Duke Energy Progress [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	18	7
Net amounts presented on Balance Sheets	18	7
Duke Energy Progress [Member] | Other Current Liabilities [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	8
Gross amounts offset	(2)
Net amounts presented on Balance Sheets	6
Duke Energy Progress [Member] | Other Noncurrent Liabilities [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	10	7
Gross amounts offset	(1)	(1)
Net amounts presented on Balance Sheets	9	6
Duke Energy Florida [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	12	12
Net amounts presented on Balance Sheets	12	12
Duke Energy Florida [Member] | Other Current Liabilities [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	10	12
Gross amounts offset		(11)
Net amounts presented on Balance Sheets	10	1
Duke Energy Florida [Member] | Other Noncurrent Liabilities [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	2
Net amounts presented on Balance Sheets	2
Duke Energy Ohio [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	5	6
Net amounts presented on Balance Sheets	5	6
Duke Energy Ohio [Member] | Other Current Liabilities [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	1	1
Net amounts presented on Balance Sheets	1	1
Duke Energy Ohio [Member] | Other Noncurrent Liabilities [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	4	5
Net amounts presented on Balance Sheets	4	5
Duke Energy Indiana [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized		2
Net amounts presented on Balance Sheets		2
Duke Energy Indiana [Member] | Other Current Liabilities [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized		2
Net amounts presented on Balance Sheets		2
Piedmont Natural Gas [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	142	187
Net amounts presented on Balance Sheets	142	187
Piedmont Natural Gas [Member] | Other Current Liabilities [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	11	35
Net amounts presented on Balance Sheets	11	35
Piedmont Natural Gas [Member] | Other Noncurrent Liabilities [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	131	152
Net amounts presented on Balance Sheets	$ 131	$ 152

Derivatives and Hedging (Deriva

Derivatives and Hedging (Derivative Instruments That Contain Credit-Risk Related Contingent Features and Cash Collateral) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Schedule Of Information Regarding Derivative Instruments That Contain Credit-Risk Related Contingent Features
Aggregate fair value of derivatives in a net liability position	$ 59	$ 34
Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered	59	34
Duke Energy Carolinas [Member]
Schedule Of Information Regarding Derivative Instruments That Contain Credit-Risk Related Contingent Features
Aggregate fair value of derivatives in a net liability position	35	16
Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered	35	16
Progress Energy [Member]
Schedule Of Information Regarding Derivative Instruments That Contain Credit-Risk Related Contingent Features
Aggregate fair value of derivatives in a net liability position	25	18
Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered	25	18
Duke Energy Progress [Member]
Schedule Of Information Regarding Derivative Instruments That Contain Credit-Risk Related Contingent Features
Aggregate fair value of derivatives in a net liability position	15	6
Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered	15	6
Duke Energy Florida [Member]
Schedule Of Information Regarding Derivative Instruments That Contain Credit-Risk Related Contingent Features
Aggregate fair value of derivatives in a net liability position	10	12
Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered	$ 10	$ 12

Investments in Debt and Equi116

Investments in Debt and Equity Securities (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Piedmont Natural Gas [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading Securities	$ 1	$ 5

Investments in Debt and Equi117

Investments in Debt and Equity Securities (Available-For-Sale Investments) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	$ 2,899	$ 2,156
Gross Unrealized Holding Losses	42	88
Estimated Fair Value	7,451	6,554
NDTF [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	2,837	2,115
Gross Unrealized Holding Losses	40	83
Estimated Fair Value	7,088	6,184
NDTF [Member] | Cash and Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value	115	111
NDTF [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	2,805	2,092
Gross Unrealized Holding Losses	27	54
Estimated Fair Value	4,914	4,106
NDTF [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	17	10
Gross Unrealized Holding Losses	2	8
Estimated Fair Value	570	528
NDTF [Member] | Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	4	3
Gross Unrealized Holding Losses	3	10
Estimated Fair Value	344	331
NDTF [Member] | US Treasury and Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	11	10
Gross Unrealized Holding Losses	7	8
Estimated Fair Value	1,027	984
NDTF [Member] | Other Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Losses	1	3
Estimated Fair Value	118	124
Other Classification [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	62	41
Gross Unrealized Holding Losses	2	5
Estimated Fair Value	363	370
Other Classification [Member] | Cash and Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value	15	25
Other Classification [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	59	38
Estimated Fair Value	123	104
Other Classification [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	1	1
Gross Unrealized Holding Losses		1
Estimated Fair Value	57	66
Other Classification [Member] | Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	2	2
Gross Unrealized Holding Losses	1	1
Estimated Fair Value	83	82
Other Classification [Member] | US Treasury and Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Losses		1
Estimated Fair Value	41	51
Other Classification [Member] | Other Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Losses	1	2
Estimated Fair Value	44	42
Duke Energy Carolinas [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	1,543	1,165
Gross Unrealized Holding Losses	20	45
Estimated Fair Value	3,758	3,261
Duke Energy Carolinas [Member] | NDTF [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	1,543	1,165
Gross Unrealized Holding Losses	20	44
Estimated Fair Value	3,758	3,258
Duke Energy Carolinas [Member] | NDTF [Member] | Cash and Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value	32	18
Duke Energy Carolinas [Member] | NDTF [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	1,531	1,157
Gross Unrealized Holding Losses	12	28
Estimated Fair Value	2,692	2,245
Duke Energy Carolinas [Member] | NDTF [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	9	5
Gross Unrealized Holding Losses	2	6
Estimated Fair Value	359	354
Duke Energy Carolinas [Member] | NDTF [Member] | Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains		1
Gross Unrealized Holding Losses	1	2
Estimated Fair Value	60	67
Duke Energy Carolinas [Member] | NDTF [Member] | US Treasury and Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	3	2
Gross Unrealized Holding Losses	4	5
Estimated Fair Value	503	458
Duke Energy Carolinas [Member] | NDTF [Member] | Other Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Losses	1	3
Estimated Fair Value	112	116
Duke Energy Carolinas [Member] | Other Classification [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Losses		1
Estimated Fair Value		3
Duke Energy Carolinas [Member] | Other Classification [Member] | Other Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Losses		1
Estimated Fair Value		3
Progress Energy [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	1,296	952
Gross Unrealized Holding Losses	20	39
Estimated Fair Value	3,389	2,991
Progress Energy [Member] | NDTF [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	1,294	950
Gross Unrealized Holding Losses	20	39
Estimated Fair Value	3,330	2,926
Progress Energy [Member] | NDTF [Member] | Cash and Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value	83	93
Progress Energy [Member] | NDTF [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	1,274	935
Gross Unrealized Holding Losses	15	26
Estimated Fair Value	2,222	1,861
Progress Energy [Member] | NDTF [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	8	5
Gross Unrealized Holding Losses		2
Estimated Fair Value	211	174
Progress Energy [Member] | NDTF [Member] | Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	4	2
Gross Unrealized Holding Losses	2	8
Estimated Fair Value	284	264
Progress Energy [Member] | NDTF [Member] | US Treasury and Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	8	8
Gross Unrealized Holding Losses	3	3
Estimated Fair Value	524	526
Progress Energy [Member] | NDTF [Member] | Other Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value	6	8
Progress Energy [Member] | Other Classification [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	2	2
Estimated Fair Value	59	65
Progress Energy [Member] | Other Classification [Member] | Cash and Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value	12	21
Progress Energy [Member] | Other Classification [Member] | Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	2	2
Estimated Fair Value	47	44
Duke Energy Progress [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	995	715
Gross Unrealized Holding Losses	16	32
Estimated Fair Value	2,592	2,214
Duke Energy Progress [Member] | NDTF [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	995	715
Gross Unrealized Holding Losses	16	32
Estimated Fair Value	2,591	2,213
Duke Energy Progress [Member] | NDTF [Member] | Cash and Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value	50	45
Duke Energy Progress [Member] | NDTF [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	980	704
Gross Unrealized Holding Losses	12	21
Estimated Fair Value	1,795	1,505
Duke Energy Progress [Member] | NDTF [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	6	4
Gross Unrealized Holding Losses		1
Estimated Fair Value	149	120
Duke Energy Progress [Member] | NDTF [Member] | Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	4	2
Gross Unrealized Holding Losses	2	8
Estimated Fair Value	283	263
Duke Energy Progress [Member] | NDTF [Member] | US Treasury and Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	5	5
Gross Unrealized Holding Losses	2	2
Estimated Fair Value	310	275
Duke Energy Progress [Member] | NDTF [Member] | Other Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value	4	5
Duke Energy Progress [Member] | Other Classification [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value	1	1
Duke Energy Progress [Member] | Other Classification [Member] | Cash and Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value	1	1
Duke Energy Florida [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	301	237
Gross Unrealized Holding Losses	4	7
Estimated Fair Value	787	761
Duke Energy Florida [Member] | NDTF [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	299	235
Gross Unrealized Holding Losses	4	7
Estimated Fair Value	739	713
Duke Energy Florida [Member] | NDTF [Member] | Cash and Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value	33	48
Duke Energy Florida [Member] | NDTF [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	294	231
Gross Unrealized Holding Losses	3	5
Estimated Fair Value	427	356
Duke Energy Florida [Member] | NDTF [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	2	1
Gross Unrealized Holding Losses		1
Estimated Fair Value	62	54
Duke Energy Florida [Member] | NDTF [Member] | Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value	1	1
Duke Energy Florida [Member] | NDTF [Member] | US Treasury and Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	3	3
Gross Unrealized Holding Losses	1	1
Estimated Fair Value	214	251
Duke Energy Florida [Member] | NDTF [Member] | Other Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value	2	3
Duke Energy Florida [Member] | Other Classification [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	2	2
Estimated Fair Value	48	48
Duke Energy Florida [Member] | Other Classification [Member] | Cash and Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value	1	4
Duke Energy Florida [Member] | Other Classification [Member] | Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	2	2
Estimated Fair Value	47	44
Duke Energy Indiana [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	49	33
Gross Unrealized Holding Losses	1	1
Estimated Fair Value	128	110
Duke Energy Indiana [Member] | Other Classification [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	49	33
Gross Unrealized Holding Losses	1	1
Estimated Fair Value	128	110
Duke Energy Indiana [Member] | Other Classification [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	49	33
Estimated Fair Value	97	79
Duke Energy Indiana [Member] | Other Classification [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value	3	2
Duke Energy Indiana [Member] | Other Classification [Member] | Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Losses	1	1
Estimated Fair Value	$ 28	28
Duke Energy Indiana [Member] | Other Classification [Member] | US Treasury and Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value		$ 1

Investments in Debt and Equi118

Investments in Debt and Equity Securities (Maturities) (Details) $ in Millions	Dec. 31, 2017USD ($)
Debt Instrument [Line Items]
Due in one year or less	$ 117
Due after one through five years	552
Due after five through ten years	554
Due after ten years	1,061
Total	2,284
Duke Energy Carolinas [Member]
Debt Instrument [Line Items]
Due in one year or less	9
Due after one through five years	204
Due after five through ten years	300
Due after ten years	521
Total	1,034
Progress Energy [Member]
Debt Instrument [Line Items]
Due in one year or less	94
Due after one through five years	301
Due after five through ten years	203
Due after ten years	474
Total	1,072
Duke Energy Progress [Member]
Debt Instrument [Line Items]
Due in one year or less	21
Due after one through five years	219
Due after five through ten years	146
Due after ten years	360
Total	746
Duke Energy Florida [Member]
Debt Instrument [Line Items]
Due in one year or less	73
Due after one through five years	82
Due after five through ten years	57
Due after ten years	114
Total	326
Duke Energy Indiana [Member]
Debt Instrument [Line Items]
Due in one year or less	5
Due after one through five years	12
Due after five through ten years	7
Due after ten years	7
Total	$ 31

Investments in Debt and Equi119

Investments in Debt and Equity Securities (Realized Gains and Losses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Realized gains	$ 202	$ 246	$ 193
Realized losses	160	187	98
Duke Energy Carolinas [Member]
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Realized gains	135	157	158
Realized losses	103	121	83
Progress Energy [Member]
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Realized gains	65	84	33
Realized losses	56	64	13
Duke Energy Progress [Member]
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Realized gains	54	71	26
Realized losses	48	55	11
Duke Energy Florida [Member]
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Realized gains	11	13	7
Realized losses	$ 8	$ 9	$ 2

Fair Value Measurements (Fair V

Fair Value Measurements (Fair Value Measurement Amounts for Assets and Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	$ 51	$ 162
Total assets	7,503	6,716
Derivative liabilities	(230)	(252)
Net assets (liabilities)	7,273	6,464
Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	3	5
Total assets	5,658	4,845
Derivative liabilities	(2)	(2)
Net assets (liabilities)	5,656	4,843
Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	20	136
Total assets	1,743	1,768
Derivative liabilities	(86)	(63)
Net assets (liabilities)	1,657	1,705
Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	28	21
Total assets	28	26
Derivative liabilities	(142)	(187)
Net assets (liabilities)	(114)	(161)
Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Alternative Investment, Fair Value Disclosure	74	77
Equity Securities [Member] | NDTF [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Alternative Investment, Fair Value Disclosure	74	77
Investments	4,914	4,106
Equity Securities [Member] | NDTF [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	4,840	4,029
Equity Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	123	104
Equity Securities [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	123	104
Debt Securities [Member] | NDTF [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	2,174	2,078
Debt Securities [Member] | NDTF [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	635	632
Debt Securities [Member] | NDTF [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1,539	1,446
Debt Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	241	266
Debt Securities [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	57	75
Debt Securities [Member] | Other Classification [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	184	186
Debt Securities [Member] | Other Classification [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		5
Duke Energy Carolinas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	2	33
Total assets	3,760	3,294
Derivative liabilities	(35)	(16)
Net assets (liabilities)	3,725	3,278
Duke Energy Carolinas [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0
Total assets	2,822	2,346
Derivative liabilities	(1)
Net assets (liabilities)	2,821	2,346
Duke Energy Carolinas [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	2	33
Total assets	864	868
Derivative liabilities	(34)	(16)
Net assets (liabilities)	830	852
Duke Energy Carolinas [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets		3
Net assets (liabilities)		3
Duke Energy Carolinas [Member] | Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Alternative Investment, Fair Value Disclosure	74	77
Duke Energy Carolinas [Member] | Equity Securities [Member] | NDTF [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Alternative Investment, Fair Value Disclosure	74	77
Investments	2,692	2,245
Duke Energy Carolinas [Member] | Equity Securities [Member] | NDTF [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	2,618	2,168
Duke Energy Carolinas [Member] | Debt Securities [Member] | NDTF [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1,066	1,013
Duke Energy Carolinas [Member] | Debt Securities [Member] | NDTF [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	204	178
Duke Energy Carolinas [Member] | Debt Securities [Member] | NDTF [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	862	835
Duke Energy Carolinas [Member] | Debt Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		3
Duke Energy Carolinas [Member] | Debt Securities [Member] | Other Classification [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		3
Progress Energy [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	3	85
Total assets	3,392	3,076
Derivative liabilities	(36)	(25)
Net assets (liabilities)	3,356	3,051
Progress Energy [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	1
Total assets	2,666	2,336
Derivative liabilities	(1)
Net assets (liabilities)	2,665	2,336
Progress Energy [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	2	85
Total assets	726	740
Derivative liabilities	(35)	(25)
Net assets (liabilities)	691	715
Progress Energy [Member] | Equity Securities [Member] | NDTF [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	2,222	1,861
Progress Energy [Member] | Equity Securities [Member] | NDTF [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	2,222	1,861
Progress Energy [Member] | Debt Securities [Member] | NDTF [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1,108	1,065
Progress Energy [Member] | Debt Securities [Member] | NDTF [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	431	454
Progress Energy [Member] | Debt Securities [Member] | NDTF [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	677	611
Progress Energy [Member] | Debt Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	59	65
Progress Energy [Member] | Debt Securities [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	12	21
Progress Energy [Member] | Debt Securities [Member] | Other Classification [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	47	44
Duke Energy Progress [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	2	46
Total assets	2,594	2,260
Derivative liabilities	(18)	(7)
Net assets (liabilities)	2,576	2,253
Duke Energy Progress [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	1
Total assets	2,040	1,713
Derivative liabilities	(1)
Net assets (liabilities)	2,039	1,713
Duke Energy Progress [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	1	46
Total assets	554	547
Derivative liabilities	(17)	(7)
Net assets (liabilities)	537	540
Duke Energy Progress [Member] | Equity Securities [Member] | NDTF [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1,795	1,505
Duke Energy Progress [Member] | Equity Securities [Member] | NDTF [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1,795	1,505
Duke Energy Progress [Member] | Debt Securities [Member] | NDTF [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	796	708
Duke Energy Progress [Member] | Debt Securities [Member] | NDTF [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	243	207
Duke Energy Progress [Member] | Debt Securities [Member] | NDTF [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	553	501
Duke Energy Progress [Member] | Debt Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1	1
Duke Energy Progress [Member] | Debt Securities [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1	1
Duke Energy Florida [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	1	39
Total assets	788	800
Derivative liabilities	(12)	(12)
Net assets (liabilities)	776	788
Duke Energy Florida [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	616	607
Net assets (liabilities)	616	607
Duke Energy Florida [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	1	39
Total assets	172	193
Derivative liabilities	(12)	(12)
Net assets (liabilities)	160	181
Duke Energy Florida [Member] | Equity Securities [Member] | NDTF [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	427	356
Duke Energy Florida [Member] | Equity Securities [Member] | NDTF [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	427	356
Duke Energy Florida [Member] | Debt Securities [Member] | NDTF [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	312	357
Duke Energy Florida [Member] | Debt Securities [Member] | NDTF [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	188	247
Duke Energy Florida [Member] | Debt Securities [Member] | NDTF [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	124	110
Duke Energy Florida [Member] | Debt Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	48	48
Duke Energy Florida [Member] | Debt Securities [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1	4
Duke Energy Florida [Member] | Debt Securities [Member] | Other Classification [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	47	44
Duke Energy Ohio [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	1	5
Derivative liabilities	(5)	(6)
Net assets (liabilities)	(4)	(1)
Duke Energy Ohio [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilities	(5)	(6)
Net assets (liabilities)	(5)	(6)
Duke Energy Ohio [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	1	5
Net assets (liabilities)	1	5
Duke Energy Indiana [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	27	16
Total assets	155	126
Derivative liabilities		(2)
Net assets (liabilities)	155	124
Duke Energy Indiana [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0
Total assets	97	79
Derivative liabilities	0	(2)
Net assets (liabilities)	97	77
Duke Energy Indiana [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	31	31
Net assets (liabilities)	31	31
Duke Energy Indiana [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	27	16
Total assets	27	16
Net assets (liabilities)	27	16
Duke Energy Indiana [Member] | Equity Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	97	79
Duke Energy Indiana [Member] | Equity Securities [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	97	79
Duke Energy Indiana [Member] | Debt Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	31	31
Duke Energy Indiana [Member] | Debt Securities [Member] | Other Classification [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	31	31
Piedmont Natural Gas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	2	3
Total assets	3	8
Derivative liabilities	(142)	(187)
Net assets (liabilities)	(139)	(179)
Piedmont Natural Gas [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	2	3
Total assets	3	8
Net assets (liabilities)	3	8
Piedmont Natural Gas [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilities	(142)	(187)
Net assets (liabilities)	(142)	(187)
Piedmont Natural Gas [Member] | Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		4
Piedmont Natural Gas [Member] | Equity Securities [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		4
Piedmont Natural Gas [Member] | Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1	1
Piedmont Natural Gas [Member] | Debt Securities [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	$ 1	$ 1

Fair Value Measurements (Reconc

Fair Value Measurements (Reconciliation of Assets and Liabilities Measured At Fair Value On A Recurring Basis Using Unobservable Inputs) (Details) - USD ($)	2 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015	Oct. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurement Transfers Between Activity Levels		$ 0	$ 0		$ 0
Investments
Beginning balance		5,000,000	5,000,000
Total pretax realized and unrealized gains included in comprehensive income		1,000,000
Sales		(6,000,000)
Ending balance	$ 5,000,000		5,000,000		5,000,000
Derivatives (net)
Beginning balance		(166,000,000)	10,000,000
Derivative Liability Resulting From Piedmont Acquisition			(187,000,000)
Purchases		55,000,000	33,000,000
Settlements		(47,000,000)	(28,000,000)
Total gains (losses) included on the Consolidated Balance Sheet		44,000,000	6,000,000
Ending balance	(166,000,000)	(114,000,000)	(166,000,000)		10,000,000
Investments and Derivatives, Net
Beginning balance		(161,000,000)	15,000,000
Total pretax realized or unrealized gains included in other comprehensive income		1,000,000
Derivative Liability Resulting From Piedmont Acquisition			(187,000,000)
Purchases		55,000,000	33,000,000
Sales		(6,000,000)
Settlements		(47,000,000)	(28,000,000)
Total gains (losses) included on the Consolidated Balance Sheet		44,000,000	6,000,000
Ending balance	(161,000,000)	(114,000,000)	(161,000,000)		15,000,000
Duke Energy Carolinas [Member]
Investments
Beginning balance		3,000,000	3,000,000
Total pretax realized and unrealized gains included in comprehensive income		1,000,000
Sales		(4,000,000)
Ending balance	3,000,000		3,000,000		3,000,000
Duke Energy Ohio [Member]
Derivatives (net)
Beginning balance		5,000,000	3,000,000
Purchases		3,000,000	5,000,000
Settlements		(4,000,000)	(5,000,000)
Total gains (losses) included on the Consolidated Balance Sheet		(3,000,000)	2,000,000
Ending balance	5,000,000	1,000,000	5,000,000		3,000,000
Duke Energy Indiana [Member]
Derivatives (net)
Beginning balance		16,000,000	7,000,000
Purchases		52,000,000	29,000,000
Settlements		(43,000,000)	(24,000,000)
Total gains (losses) included on the Consolidated Balance Sheet		2,000,000	4,000,000
Ending balance	16,000,000	27,000,000	16,000,000		$ 7,000,000
Piedmont Natural Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurement Transfers Between Activity Levels	0			$ 0		$ 0
Derivatives (net)
Beginning balance	(188,000,000)	(187,000,000)
Total gains (losses) and settlements	1,000,000	45,000,000		(188,000,000)
Ending balance	$ (187,000,000)	$ (142,000,000)	$ (187,000,000)	$ (188,000,000)

Fair Value Measurements (Quanti

Fair Value Measurements (Quantitative Level 3 Fair Value Disclosure - Assets) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)$ / MWh	Dec. 31, 2016USD ($)$ / MWh	Dec. 31, 2015USD ($)
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Net Derivative Asset (Liability)	$ (114)	$ (166)	$ 10
Duke Energy Ohio [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Net Derivative Asset (Liability)	1	5	3
Duke Energy Ohio [Member] | Financial Transmission Rights [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Net Derivative Asset (Liability)	$ 1	$ 5
Duke Energy Ohio [Member] | Financial Transmission Rights [Member] | Minimum [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Input Price Per Unit | $ / MWh	0.07	0.77
Duke Energy Ohio [Member] | Financial Transmission Rights [Member] | Maximum [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Input Price Per Unit | $ / MWh	1.41	3.52
Duke Energy Indiana [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Net Derivative Asset (Liability)	$ 27	$ 16	$ 7
Duke Energy Indiana [Member] | Financial Transmission Rights [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Net Derivative Asset (Liability)	$ 27	$ 16
Duke Energy Indiana [Member] | Financial Transmission Rights [Member] | Minimum [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Input Price Per Unit | $ / MWh	(0.77)	(0.83)
Duke Energy Indiana [Member] | Financial Transmission Rights [Member] | Maximum [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Input Price Per Unit | $ / MWh	7.44	9.32

Fair Value Measurements (Qua123

Fair Value Measurements (Quantitative Level 3 Fair Value Disclosures - Liabilities (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)$ / MMBTU	Dec. 31, 2016USD ($)$ / MMBTU	Oct. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Net Derivative Asset (Liability)	$ (114)	$ (166)		$ 10
Piedmont Natural Gas [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Net Derivative Asset (Liability)	(142)	(187)	$ (188)
Natural Gas, derivative liability [Member] | Discounted Cash Flow [Member] | Piedmont Natural Gas [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Net Derivative Asset (Liability)	$ (142)	$ (187)
Natural Gas, derivative liability [Member] | Minimum [Member] | Discounted Cash Flow [Member] | Piedmont Natural Gas [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Fair Value Input Price Per Unit | $ / MMBTU	2.10	2.31
Natural Gas, derivative liability [Member] | Maximum [Member] | Discounted Cash Flow [Member] | Piedmont Natural Gas [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Fair Value Input Price Per Unit | $ / MMBTU	2.88	4.18

Fair Value Measurements (Additi

Fair Value Measurements (Additional Fair Value Disclosure) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 52,279	$ 47,895
Long-term debt, fair value	55,331	49,161
Duke Energy Carolinas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	10,103	9,603
Long-term debt, fair value	11,372	10,494
Progress Energy [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	17,837	17,541
Long-term debt, fair value	20,000	19,107
Duke Energy Progress [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	7,357	7,011
Long-term debt, fair value	7,992	7,357
Duke Energy Florida [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	7,095	6,125
Long-term debt, fair value	7,953	6,728
Duke Energy Ohio [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	2,067	1,884
Long-term debt, fair value	2,249	2,020
Duke Energy Indiana [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	3,783	3,786
Long-term debt, fair value	4,464	4,260
Piedmont Natural Gas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	2,037	1,821
Long-term debt, fair value	$ 2,209	$ 1,933

Variable Interest Entities (Nar

Variable Interest Entities (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jun. 30, 2016
Variable Interest Entity [Line Items]
Debt Instrument, Face Amount	$ 6,070,000,000	$ 9,127,000,000
Asset Impairment Charges	282,000,000	18,000,000	$ 106,000,000
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Financial or Other Support, Amount	$ 0	0	0
Cinergy Receivables [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Percent of proceeds received as cash	75.00%
Percent of proceeds received as subordinated note	25.00%
Minimum Equity Balance required by Cinergy Receivables	$ 3,000,000
Pioneer Transmission [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity Ownership Interest	50.00%
Duke Energy Carolinas [Member]
Variable Interest Entity [Line Items]
Debt Instrument, Face Amount	$ 550,000,000	1,600,000,000
Asset Impairment Charges		1,000,000	1,000,000
Duke Energy Progress [Member]
Variable Interest Entity [Line Items]
Debt Instrument, Face Amount	800,000,000	450,000,000
Asset Impairment Charges	19,000,000	1,000,000	5,000,000
Duke Energy Florida [Member]
Variable Interest Entity [Line Items]
Debt Instrument, Face Amount	1,300,000,000	1,894,000,000
Asset Impairment Charges	138,000,000	6,000,000	7,000,000
Duke Energy Florida [Member] | DEFPF [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Debt Instrument, Face Amount				$ 1,294,000,000
Duke Energy Ohio [Member]
Variable Interest Entity [Line Items]
Debt Instrument, Face Amount	100,000,000	250,000,000
Asset Impairment Charges	$ 1,000,000
Duke Energy Ohio [Member] | Cinergy Receivables [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Fixed interest rate added to LIBOR to compute variable rate	1.00%
Duke Energy Ohio [Member] | OVEC [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity Ownership Interest	9.00%
Duke Energy Indiana [Member]
Variable Interest Entity [Line Items]
Debt Instrument, Face Amount		500,000,000
Asset Impairment Charges	$ 18,000,000	$ 8,000,000	$ 88,000,000
Duke Energy Indiana [Member] | Cinergy Receivables [Member]
Variable Interest Entity [Line Items]
Fixed interest rate added to LIBOR to compute variable rate	1.00%

Variable Interest Entities (Sch

Variable Interest Entities (Schedule of Accounts Receivable Securitizations)(Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Long-Term debt	$ 49,035	$ 45,576
Duke Energy Carolinas [Member]
Variable Interest Entity [Line Items]
Long-Term debt	8,598	9,187
Duke Energy Progress [Member]
Variable Interest Entity [Line Items]
Long-Term debt	7,204	6,409
Duke Energy Florida [Member]
Variable Interest Entity [Line Items]
Long-Term debt	$ 6,327	5,799
Cinergy Receivables [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Line of credit facility, expiration date	Dec. 1, 2020
Facility Size	$ 325
Long-Term debt	$ 325	325
DERF [Member] | Duke Energy Carolinas [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Line of credit facility, expiration date	Dec. 1, 2020
Facility Size	$ 450
Long-Term debt	$ 450	425
DEPR [Member] | Duke Energy Progress [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Line of credit facility, expiration date	Feb. 1, 2019
Facility Size	$ 300
Long-Term debt	$ 300	300
DEFR [Member] | Duke Energy Florida [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Line of credit facility, expiration date	Apr. 1, 2019
Facility Size	$ 225
Long-Term debt	$ 225	$ 225

Variable Interest Entities (Con

Variable Interest Entities (Consolidated VIEs) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Variable Interest Entity Consolidated Carrying Amount, Assets and Liabilities, Net [Abstract]
Cash and Cash Equivalents, at Carrying Value	$ 358	$ 392	$ 383	$ 463
Regulatory Assets, Current	1,437	1,023
Other current assets	634	458
Property, plant and equipment, cost	127,507	121,397
Accumulated depreciation and amortization	(41,537)	(39,406)
Regulatory assets, noncurrent	12,442	12,878
Investments and other assets	2,960	2,769
Accounts payable	3,043	2,994
Current maturities of long-term debt	3,244	2,319
Other current liabilities	1,865	2,044
Long-Term debt	49,035	45,576
Deferred income taxes	6,621	14,155
Asset retirement obligations	9,486	10,200
Other Liabilities	1,581	1,753
Duke Energy Carolinas [Member]
Variable Interest Entity Consolidated Carrying Amount, Assets and Liabilities, Net [Abstract]
Cash and Cash Equivalents, at Carrying Value	16	14	13	13
Regulatory Assets, Current	299	238
Other current assets	19	37
Property, plant and equipment, cost	42,939	41,127
Accumulated depreciation and amortization	(15,063)	(14,365)
Regulatory assets, noncurrent	2,853	3,159
Investments and other assets	979	943
Accounts payable	842	833
Current maturities of long-term debt	1,205	116
Other current liabilities	486	468
Long-Term debt	8,598	9,187
Deferred income taxes	3,413	6,544
Asset retirement obligations	3,273	3,673
Other Liabilities	566	607
Duke Energy Progress [Member]
Variable Interest Entity Consolidated Carrying Amount, Assets and Liabilities, Net [Abstract]
Cash and Cash Equivalents, at Carrying Value	20	11	15	9
Regulatory Assets, Current	352	188
Other current assets	97	57
Property, plant and equipment, cost	29,583	28,419
Accumulated depreciation and amortization	(10,903)	(10,561)
Regulatory assets, noncurrent	3,507	3,243
Investments and other assets	599	525
Accounts payable	402	589
Current maturities of long-term debt	3	452
Other current liabilities	376	365
Long-Term debt	7,204	6,409
Deferred income taxes	1,883	3,323
Asset retirement obligations	4,378	4,508
Other Liabilities	45	51
Duke Energy Florida [Member]
Variable Interest Entity Consolidated Carrying Amount, Assets and Liabilities, Net [Abstract]
Cash and Cash Equivalents, at Carrying Value	13	16	$ 8	$ 8
Regulatory Assets, Current	389	213
Other current assets	86	125
Property, plant and equipment, cost	17,730	16,434
Accumulated depreciation and amortization	(4,947)	(4,644)
Regulatory assets, noncurrent	2,503	2,480
Investments and other assets	284	278
Accounts payable	602	413
Current maturities of long-term debt	768	326
Other current liabilities	334	352
Long-Term debt	6,327	5,799
Deferred income taxes	1,761	2,694
Asset retirement obligations	742	778
Other Liabilities	108	105
DEFPF [Member] | Duke Energy Florida [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity Consolidated Carrying Amount, Assets and Liabilities, Net [Abstract]
Restricted receivables of VIEs	4	6
Regulatory Assets, Current	51	50
Other current assets	40	53
Regulatory assets, noncurrent	1,091	1,142
Current maturities of long-term debt	53	62
Other current liabilities	10	17
Long-Term debt	1,164	1,217
DERF [Member] | Duke Energy Carolinas [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity Consolidated Carrying Amount, Assets and Liabilities, Net [Abstract]
Long-Term debt	450	425
DEPR [Member] | Duke Energy Progress [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity Consolidated Carrying Amount, Assets and Liabilities, Net [Abstract]
Long-Term debt	300	300
DEFR [Member] | Duke Energy Florida [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity Consolidated Carrying Amount, Assets and Liabilities, Net [Abstract]
Long-Term debt	225	225
Cinergy Receivables [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity Consolidated Carrying Amount, Assets and Liabilities, Net [Abstract]
Long-Term debt	325	325
Commercial Renewables [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity Consolidated Carrying Amount, Assets and Liabilities, Net [Abstract]
Other current assets	174	223
Property, plant and equipment, cost	3,923	3,419
Accumulated depreciation and amortization	(591)	(453)
Current maturities of long-term debt	170	198
Long-Term debt	1,700	1,097
Deferred income taxes	(148)	275
Other Liabilities	$ 241	$ 252

Variable Interest Entities (128

Variable Interest Entities (Schedule of Non-Consolidated VIEs) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Investments in equity method unconsolidated affiliates	$ 1,175	$ 925
Investments and other assets	2,960	2,769
Taxes Payable, Current	551	384
Other current liabilities	1,865	2,044
Deferred Income Taxes and Other Tax Liabilities, Noncurrent	6,621	14,155
Other Liabilities	1,581	1,753
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Investments in equity method unconsolidated affiliates	919	751
Investments and other assets	17	12
Total assets	936	763
Taxes Payable, Current	(29)
Other current liabilities	4	3
Deferred Income Taxes and Other Tax Liabilities, Noncurrent	42
Other Liabilities	12	13
Total liabilities	29	16
Net assets of non-consolidated VIEs	907	747
Pipeline Investments [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Investments in equity method unconsolidated affiliates	697	487
Investments and other assets	17	12
Total assets	714	499
Taxes Payable, Current	(29)
Deferred Income Taxes and Other Tax Liabilities, Noncurrent	42
Total liabilities	13
Net assets of non-consolidated VIEs	701	499
Other VIEs [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Investments in equity method unconsolidated affiliates	42	90
Total assets	42	90
Other current liabilities	4	3
Other Liabilities	12	13
Total liabilities	16	16
Net assets of non-consolidated VIEs	26	74
Commercial Renewables [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Investments in equity method unconsolidated affiliates	180	174
Total assets	180	174
Net assets of non-consolidated VIEs	180	174
Duke Energy Ohio [Member]
Variable Interest Entity [Line Items]
Receivables from affiliated companies	133	129
Investments and other assets	21	23
Taxes Payable, Current	190	178
Other current liabilities	71	91
Deferred Income Taxes and Other Tax Liabilities, Noncurrent	781	1,443
Other Liabilities	108	166
Duke Energy Ohio [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Receivables from affiliated companies	87	82
Total assets	87	82
Net assets of non-consolidated VIEs	87	82
Duke Energy Indiana [Member]
Variable Interest Entity [Line Items]
Receivables from affiliated companies	125	114
Investments and other assets	189	147
Taxes Payable, Current	95	31
Other current liabilities	104	93
Deferred Income Taxes and Other Tax Liabilities, Noncurrent	925	1,900
Other Liabilities	18	27
Duke Energy Indiana [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Receivables from affiliated companies	106	101
Total assets	106	101
Net assets of non-consolidated VIEs	106	101
Piedmont Natural Gas [Member]
Variable Interest Entity [Line Items]
Receivables from affiliated companies	7	7
Investments in equity method unconsolidated affiliates	61	212
Investments and other assets	65	21
Taxes Payable, Current	19	67
Other current liabilities	69	102
Deferred Income Taxes and Other Tax Liabilities, Noncurrent	564	931
Other Liabilities	$ 170	189
Piedmont Natural Gas [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Investments in equity method unconsolidated affiliates		139
Total assets		139
Other Liabilities		4
Total liabilities		4
Net assets of non-consolidated VIEs		$ 135

Variable Interest Entities (Joi

Variable Interest Entities (Joint-Venture Ownership Information) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Investments In Unconsolidated Affiliates [Line Items]
Investments in equity method unconsolidated affiliates	$ 1,175	$ 925
Duke American Transmission Company [Member]
Investments In Unconsolidated Affiliates [Line Items]
Equity Method Investment, Ownership Percentage	50.00%
Investments in equity method unconsolidated affiliates	$ 46

Variable Interest Entities (130

Variable Interest Entities (Schedule of Non-Consolidated VIE Pipeline Investments) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Investments in equity method unconsolidated affiliates	$ 1,175	$ 925
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Investments in equity method unconsolidated affiliates	919	751
Piedmont Natural Gas [Member]
Variable Interest Entity [Line Items]
Investments in equity method unconsolidated affiliates	$ 61	212
Piedmont Natural Gas [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Investments in equity method unconsolidated affiliates		139
Constitution Pipeline [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage	24.00%
Investments in equity method unconsolidated affiliates	$ 81	82
Sabal Trail Transmission Pipeline [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage	7.50%
Investments in equity method unconsolidated affiliates	$ 219	140
Atlantic Coast Pipeline [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage	47.00%
Investments in equity method unconsolidated affiliates	$ 397	265
Pipeline Investments [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Investments in equity method unconsolidated affiliates	$ 697	$ 487

Variable Interest Entities (Fai

Variable Interest Entities (Fair Value Assumptions)(Details) - Cinergy Receivables [Member] - Variable Interest Entity, Not Primary Beneficiary [Member]	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Duke Energy Ohio [Member]
Variable Interest Entity [Line Items]
Anticipated credit loss ratio	0.50%	0.50%
Discount rate	2.10%	1.50%
Receivable turnover rate	13.50%	13.30%
Duke Energy Indiana [Member]
Variable Interest Entity [Line Items]
Anticipated credit loss ratio	0.30%	0.30%
Discount rate	2.10%	1.50%
Receivable turnover rate	10.70%	10.60%

Variable Interest Entities (Rec

Variable Interest Entities (Receivables Sold)(Details) - Variable Interest Entity, Not Primary Beneficiary [Member] - Cinergy Receivables [Member] - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Duke Energy Ohio [Member]
Variable Interest Entity [Line Items]
Receivables sold	$ 273	$ 267
Less: retained interests	87	82
Net receivables sold	186	185
Duke Energy Indiana [Member]
Variable Interest Entity [Line Items]
Receivables sold	312	306
Less: retained interests	106	101
Net receivables sold	$ 206	$ 205

Variable Interest Entities (Sal

Variable Interest Entities (Sales and Cash Flows)(Details) - Variable Interest Entity, Not Primary Beneficiary [Member] - Cinergy Receivables [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Duke Energy Ohio [Member]
Variable Interest Entity [Line Items]
Receivables sold	$ 1,879	$ 1,926	$ 1,963
Loss recognized on sale	10	9	9
Cash proceeds from receivables sold	1,865	1,882	1,995
Collection fees received	1	1	1
Return received on retained interests	3	2	3
Duke Energy Indiana [Member]
Variable Interest Entity [Line Items]
Receivables sold	2,711	2,635	2,627
Loss recognized on sale	12	11	11
Cash proceeds from receivables sold	2,694	2,583	2,670
Collection fees received	1	1	1
Return received on retained interests	$ 7	$ 5	$ 5

Common Stock (Earnings Per Shar

Common Stock (Earnings Per Share Data)(Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Income (Loss) from Continuing Operations, Net of Tax, Excluding Participating Securities									$ 3,059	$ 2,567	$ 2,640
Weighted Average Number of Shares Outstanding, Basic									700	691	694
Weighted Average Number of Shares Outstanding, Diluted									700	691	694
EPS, basic (usd per share)	$ 1	$ 1.36	$ 0.98	$ 1.02	$ 0.53	$ 1.44	$ 0.90	$ 0.83	$ 4.37	$ 3.71	$ 3.80
EPS, diluted (usd per share)	$ 1	$ 1.36	$ 0.98	$ 1.02	$ 0.53	$ 1.44	$ 0.90	$ 0.83	$ 4.37	$ 3.71	$ 3.80
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount									2	2	2
Dividends declared per share (usd per share)									$ 3.49	$ 3.36	$ 3.24

Common Stock (Accelerated Share

Common Stock (Accelerated Share Repurchase) (Details) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	1 Months Ended		12 Months Ended
	Jun. 30, 2015	Apr. 30, 2015	Dec. 31, 2015	Apr. 06, 2015
Accelerated Share Repurchases [Line Items]
Stock Repurchase Program, Authorized Amount		$ 1,500
Payments for Repurchase of Common Stock		$ 1,500	$ 1,500
Delivered shares from Dealers	3.2	16.6	19.8
Fair Market Value of Delivered Shares	$ 225	$ 1,275	$ 1,500
Percentage of ASR common stock received				85.00%
Accelerated Share Repurchases, Final Price Paid Per Share			$ 75.75
Goldman Sachs [Member]
Accelerated Share Repurchases [Line Items]
Payments for Repurchase of Common Stock		750
JPMorgan Chase [Member]
Accelerated Share Repurchases [Line Items]
Payments for Repurchase of Common Stock		$ 750

Common Stock (Equity Securities

Common Stock (Equity Securities Offering) (Details) - USD ($) shares in Millions, $ in Millions	Feb. 20, 2018	Oct. 31, 2016	Mar. 31, 2016
Piedmont Natural Gas [Member]
Forward Contract Indexed to Issuer's Equity [Line Items]
Shares offered			10.6
Settlement Alternatives, Shares			10.6
Common stock issuances, including dividend reinvestment and employee benefits (in shares)		10.6
Proceeds from Issuance or Sale of Equity		$ 723
Subsequent Event [Member]
Forward Contract Indexed to Issuer's Equity [Line Items]
Maximum value of shares to be issued under ATM program	$ 1,000

Severance (Narrative) (Details)

Severance (Narrative) (Details) - Employees	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restructuring and Related Activities [Abstract]
Number of eligible employees	100	600	900

Severance (Expenses) (Details)

Severance (Expenses) (Details) - USD ($)	2 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015	Oct. 31, 2015
Restructuring Cost and Reserve [Line Items]
Severance expense		$ 15,000,000	$ 118,000,000		$ 142,000,000
Duke Energy Carolinas [Member]
Restructuring Cost and Reserve [Line Items]
Severance expense		2,000,000	39,000,000		93,000,000
Progress Energy [Member]
Restructuring Cost and Reserve [Line Items]
Severance expense		2,000,000	40,000,000		36,000,000
Duke Energy Progress [Member]
Restructuring Cost and Reserve [Line Items]
Severance expense		1,000,000	23,000,000		28,000,000
Duke Energy Florida [Member]
Restructuring Cost and Reserve [Line Items]
Severance expense		1,000,000	17,000,000		8,000,000
Duke Energy Ohio [Member]
Restructuring Cost and Reserve [Line Items]
Severance expense			3,000,000		2,000,000
Duke Energy Indiana [Member]
Restructuring Cost and Reserve [Line Items]
Severance expense		1,000,000	$ 7,000,000		$ 6,000,000
Piedmont Natural Gas [Member]
Restructuring Cost and Reserve [Line Items]
Severance expense	$ 3,000,000	$ 9,000,000		$ 19,000,000		$ 0

Severance (Rollforward) (Detail

Severance (Rollforward) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)
Restructuring Reserve [Roll Forward]
Balance, beginning of period	$ 79
Provision/adjustments	17
Cash reductions	(77)
Balance, end of period	19
Duke Energy Carolinas [Member]
Restructuring Reserve [Roll Forward]
Balance, beginning of period	13
Provision/adjustments	2
Cash reductions	(10)
Balance, end of period	5
Progress Energy [Member]
Restructuring Reserve [Roll Forward]
Balance, beginning of period	14
Cash reductions	(12)
Balance, end of period	2
Duke Energy Progress [Member]
Restructuring Reserve [Roll Forward]
Balance, beginning of period	6
Cash reductions	(5)
Balance, end of period	1
Duke Energy Florida [Member]
Restructuring Reserve [Roll Forward]
Balance, beginning of period	8
Cash reductions	(8)
Piedmont Natural Gas [Member]
Restructuring Reserve [Roll Forward]
Balance, beginning of period	20
Provision/adjustments	9
Cash reductions	(24)
Balance, end of period	$ 5

Stock-Based Compensation (Narra

Stock-Based Compensation (Narrative) (Details) - USD ($) shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for awards to employees and outside directors	10,000
Restricted Stock Units Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value	$ 47,000,000	$ 52,000,000	$ 41,000,000
Total grant date fair value of shares vested	42,000,000	38,000,000	41,000,000
Unrecognized compensation cost	$ 29,000,000
Unrecognized compensation cost, period of recognition, years	23 months
Restricted Stock Units Awards [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	3 years
Performance Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value	$ 37,000,000	25,000,000	26,000,000
Risk Free Interest Rate	1.50%
Expected Volatility Rate	17.20%
Total grant date fair value of shares vested	$ 0	$ 25,000,000	$ 26,000,000
Unrecognized compensation cost	$ 34,000,000
Unrecognized compensation cost, period of recognition, years	23 months
Stock Options [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum option term, years	10 years
Piedmont Natural Gas [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Issued			194
Fair value			$ 11,000,000

Stock-Based Compensation (Sched

Stock-Based Compensation (Schedule of Stock-Based Compensation Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015	Oct. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense, Net of Tax	$ 43	$ 35	$ 10	$ 38	$ 10
Pretax stock-based compensation expense	68	55	16	61	14
Tax benefit associated with stock-based compensation expense	25	20	$ 6	23	$ 4
Stock-based compensation costs capitalized	4	2		3
Restricted Stock Units Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pretax stock-based compensation expense	41	36		38
Performance Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pretax stock-based compensation expense	27	19		23
Duke Energy Carolinas [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense, Net of Tax	15	12		14
Progress Energy [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense, Net of Tax	16	12		14
Duke Energy Progress [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense, Net of Tax	10	7		9
Duke Energy Florida [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense, Net of Tax	6	5		5
Duke Energy Ohio [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense, Net of Tax	3	2		2
Duke Energy Indiana [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense, Net of Tax	4	$ 3		$ 4
Piedmont Natural Gas [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense, Net of Tax	$ 3

Stock-Based Compensation (Summa

Stock-Based Compensation (Summary of Stock Awards Outstanding) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restricted Stock Units Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding at beginning of period	1,139
Granted	583	684	524
Vested	(553)
Forfeited	(48)
Outstanding at end of period	1,121	1,139
Stock awards expected to vest	1,094
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Weighted average fair value at beginning of period	$ 76
Granted	80
Vested	76
Forfeited	78
Weighted average fair value at end of period	78	$ 76
Weighted average fair value of awards expected to vest	$ 78
Share Based Compensation Grants In Period Fair Value	$ 47	$ 52	$ 41
Performance Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding at beginning of period	862
Granted	461	338	321
Forfeited	(258)
Outstanding at end of period	1,065	862
Stock awards expected to vest	1,034
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Weighted average fair value at beginning of period	$ 75
Granted	81
Forfeited	69
Weighted average fair value at end of period	79	$ 75
Weighted average fair value of awards expected to vest	$ 79
Share Based Compensation Grants In Period Fair Value	$ 37	$ 25	$ 26
Piedmont Natural Gas [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures			194
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Share Based Compensation Grants In Period Fair Value			$ 11

Stock-Based Compensation (Stock

Stock-Based Compensation (Stock Options) (Details) - Stock Options [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Schedule Of Information Related To Stock Options [Abstract]
Intrinsic value of options exercised	$ 1	$ 5
Tax benefit related to options execised		2
Cash received from options exercised	$ 7	$ 17

Employee Benefit Plans (Narrati

Employee Benefit Plans (Narrative) (Details) - USD ($) $ in Millions	2 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015	Oct. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Impact of plan conversion on next year's net periodic benefit cost		$ 33
Maximum years of participation		35 years
Master Trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected long-term rate of return on plan assets		6.50%
Fair value of securities on loan	$ 156	$ 195	$ 156
Pension Plan [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		13 years
Expected long-term rate of return on plan assets					6.50%
Pension Plan [Member] | Nonqualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		11 years
Pension Plan [Member] | Master Trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Master trust allocation percentage		98.00%
Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		9 years
Expected long-term rate of return on plan assets		6.50%	6.50%		6.50%
Other Post-Retirement Benefit Plans [Member] | Master Trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Master trust allocation percentage		2.00%
Duke Energy Carolinas [Member] | Pension Plan [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		12 years
Duke Energy Carolinas [Member] | Pension Plan [Member] | Nonqualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		8 years
Duke Energy Carolinas [Member] | Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		8 years
Progress Energy [Member] | Pension Plan [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		12 years
Progress Energy [Member] | Pension Plan [Member] | Nonqualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		14 years
Progress Energy [Member] | Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		6 years
Duke Energy Progress [Member] | Pension Plan [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		13 years
Duke Energy Progress [Member] | Pension Plan [Member] | Nonqualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		11 years
Duke Energy Progress [Member] | Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		6 years
Duke Energy Florida [Member] | Pension Plan [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		12 years
Duke Energy Florida [Member] | Pension Plan [Member] | Nonqualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		15 years
Duke Energy Florida [Member] | Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		7 years
Duke Energy Ohio [Member] | Pension Plan [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		14 years
Duke Energy Ohio [Member] | Pension Plan [Member] | Nonqualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		8 years
Duke Energy Ohio [Member] | Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		7 years
Duke Energy Indiana [Member] | Pension Plan [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		14 years
Duke Energy Indiana [Member] | Pension Plan [Member] | Nonqualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		8 years
Duke Energy Indiana [Member] | Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		6 years
Piedmont Natural Gas [Member] | Pension Plan [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		9 years
Expected long-term rate of return on plan assets	6.75%			7.25%		7.50%
Piedmont Natural Gas [Member] | Pension Plan [Member] | Nonqualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		9 years
Piedmont Natural Gas [Member] | Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		7 years
Expected long-term rate of return on plan assets	6.75%			7.25%		7.50%

Employee Benefit Plans (Contrib

Employee Benefit Plans (Contributions to Defined Benefit Pension Plans) (Details) - Pension Plan [Member] - USD ($) $ in Millions	Jan. 02, 2018	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015	Oct. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Anticipated contribution			$ 148
Employer contributions			19	$ 155		$ 302
Duke Energy Carolinas [Member]
Defined Benefit Plan Disclosure [Line Items]
Anticipated contribution			46
Employer contributions				43		91
Progress Energy [Member]
Defined Benefit Plan Disclosure [Line Items]
Anticipated contribution			45
Employer contributions				43		83
Duke Energy Progress [Member]
Defined Benefit Plan Disclosure [Line Items]
Anticipated contribution			25
Employer contributions				24		42
Duke Energy Florida [Member]
Defined Benefit Plan Disclosure [Line Items]
Anticipated contribution			20
Employer contributions				20		40
Duke Energy Ohio [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions			4	5		8
Duke Energy Indiana [Member]
Defined Benefit Plan Disclosure [Line Items]
Anticipated contribution			8
Employer contributions				9		19
Piedmont Natural Gas [Member]
Defined Benefit Plan Disclosure [Line Items]
Anticipated contribution			7
Employer contributions		$ 10	$ 11		$ 10		$ 10
Subsequent Event [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 141
Anticipated contributions remainder of 2018	7
Subsequent Event [Member] | Duke Energy Carolinas [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	46
Subsequent Event [Member] | Progress Energy [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	45
Subsequent Event [Member] | Duke Energy Progress [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	25
Subsequent Event [Member] | Duke Energy Florida [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	20
Subsequent Event [Member] | Duke Energy Indiana [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	8
Subsequent Event [Member] | Piedmont Natural Gas [Member]
Defined Benefit Plan Disclosure [Line Items]
Anticipated contributions remainder of 2018	$ 7

Employee Benefit Plans (Compone

Employee Benefit Plans (Components of Net Periodic Pension Costs) (Details) - USD ($) $ in Millions	2 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015	Oct. 31, 2015
Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Amortization of Regulatory Asset		$ 7	$ 8		$ 9
Pension Plan [Member] | Qualified Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		159	147		159
Interest cost		328	335		324
Expected return on plan assets		(545)	(519)		(516)
Amortization of actuarial loss (gain)		146	134		166
Amortization of prior service cost (credit)		(24)	(17)		(15)
Settlement charge		12	3
Other		8	8		8
Net periodic costs		84	91		126
Pension Plan [Member] | Nonqualified Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		2	2		3
Interest cost		13	14		13
Amortization of actuarial loss (gain)		8	8		6
Amortization of prior service cost (credit)		(2)	(1)		(1)
Net periodic costs		21	23		21
Pension Plan [Member] | Duke Energy Carolinas [Member] | Qualified Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		48	48		50
Interest cost		79	86		83
Expected return on plan assets		(142)	(142)		(139)
Amortization of actuarial loss (gain)		31	33		39
Amortization of prior service cost (credit)		(8)	(8)		(7)
Other		2	2		2
Net periodic costs		10	19		28
Pension Plan [Member] | Duke Energy Carolinas [Member] | Nonqualified Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		1
Interest cost		1	1		1
Amortization of actuarial loss (gain)			1
Net periodic costs		2	2		1
Pension Plan [Member] | Progress Energy [Member] | Qualified Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		45	42		44
Interest cost		100	106		104
Expected return on plan assets		(167)	(168)		(171)
Amortization of actuarial loss (gain)		52	51		65
Amortization of prior service cost (credit)		(3)	(3)		(3)
Other		2	3		3
Net periodic costs		29	31		42
Pension Plan [Member] | Progress Energy [Member] | Nonqualified Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost					1
Interest cost		5	5		4
Amortization of actuarial loss (gain)		2	1		2
Amortization of prior service cost (credit)					(1)
Net periodic costs		7	6		6
Pension Plan [Member] | Duke Energy Progress [Member] | Qualified Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		26	24		23
Interest cost		47	49		48
Expected return on plan assets		(82)	(82)		(79)
Amortization of actuarial loss (gain)		23	23		33
Amortization of prior service cost (credit)		(2)	(2)		(2)
Other		1	1		1
Net periodic costs		13	13		24
Pension Plan [Member] | Duke Energy Progress [Member] | Nonqualified Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost		1	1		1
Amortization of actuarial loss (gain)		1	1		1
Net periodic costs		2	2		2
Pension Plan [Member] | Duke Energy Florida [Member] | Qualified Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		19	19		20
Interest cost		53	55		54
Expected return on plan assets		(85)	(84)		(87)
Amortization of actuarial loss (gain)		29	29		31
Amortization of prior service cost (credit)		(1)	(1)		(1)
Other		1	1		1
Net periodic costs		16	19		18
Pension Plan [Member] | Duke Energy Florida [Member] | Nonqualified Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost		2	2		2
Amortization of actuarial loss (gain)		1	1		2
Net periodic costs		3	3		4
Pension Plan [Member] | Duke Energy Ohio [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Amortization of Regulatory Asset		3	4		4
Pension Plan [Member] | Duke Energy Ohio [Member] | Qualified Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		4	4		4
Interest cost		18	19		18
Expected return on plan assets		(27)	(27)		(26)
Amortization of actuarial loss (gain)		5	4		7
Amortization of prior service cost (credit)		(1)
Other			1
Net periodic costs		(1)	1		3
Pension Plan [Member] | Duke Energy Indiana [Member] | Qualified Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		9	9		10
Interest cost		26	28		27
Expected return on plan assets		(42)	(42)		(42)
Amortization of actuarial loss (gain)		12	11		13
Amortization of prior service cost (credit)		(2)	(1)		1
Other		1	1		1
Net periodic costs		4	6		10
Pension Plan [Member] | Duke Energy Indiana [Member] | Nonqualified Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Amortization of actuarial loss (gain)					1
Net periodic costs					1
Pension Plan [Member] | Piedmont Natural Gas [Member] | Qualified Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 2	10		$ 11		$ 11
Interest cost	2	14		9		12
Expected return on plan assets	(4)	(24)		(24)		(24)
Amortization of actuarial loss (gain)	2	11		8		9
Amortization of prior service cost (credit)	(1)	(2)		(2)		(2)
Settlement charge	3	12
Other		1
Net periodic costs	$ 4	22		2		6
Pension Plan [Member] | Piedmont Natural Gas [Member] | Nonqualified Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Amortization of prior service cost (credit)						1
Settlement charge				1
Net periodic costs				1		1
Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		4	3		6
Interest cost		34	35		36
Expected return on plan assets		(14)	(12)		(13)
Amortization of actuarial loss (gain)		10	6		16
Amortization of prior service cost (credit)		(115)	(141)		(140)
Curtailment credit		(30)
Net periodic costs		(111)	(109)		(95)
Amortization of Regulatory Asset		7	8		10
Other Post-Retirement Benefit Plans [Member] | Duke Energy Carolinas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		1	1		1
Interest cost		8	8		9
Expected return on plan assets		(8)	(8)		(8)
Amortization of actuarial loss (gain)		(2)	(3)		(2)
Amortization of prior service cost (credit)		(10)	(14)		(14)
Curtailment credit		(4)
Net periodic costs		(15)	(16)		(14)
Other Post-Retirement Benefit Plans [Member] | Progress Energy [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost			1		1
Interest cost		13	15		15
Amortization of actuarial loss (gain)		21	22		28
Amortization of prior service cost (credit)		(84)	(103)		(102)
Curtailment credit		(16)
Net periodic costs		(66)	(65)		(58)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Progress [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost					1
Interest cost		7	8		8
Amortization of actuarial loss (gain)		12	13		18
Amortization of prior service cost (credit)		(54)	(68)		(68)
Net periodic costs		(35)	(47)		(41)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Florida [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost			1		1
Interest cost		6	7		7
Amortization of actuarial loss (gain)		9	9		10
Amortization of prior service cost (credit)		(30)	(35)		(35)
Curtailment credit		(16)
Net periodic costs		(31)	(18)		(17)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Ohio [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost		1	1		2
Expected return on plan assets					(1)
Amortization of actuarial loss (gain)		(2)	(2)		(2)
Curtailment credit		(2)
Net periodic costs		(3)	(1)		(1)
Amortization of Regulatory Asset		2	2		3
Other Post-Retirement Benefit Plans [Member] | Duke Energy Indiana [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost					1
Interest cost		3	4		4
Expected return on plan assets		(1)	(1)		(1)
Amortization of actuarial loss (gain)		(1)	(1)		(2)
Amortization of prior service cost (credit)		(1)	(1)
Curtailment credit		(2)
Net periodic costs		(2)	$ 1		$ 2
Other Post-Retirement Benefit Plans [Member] | Piedmont Natural Gas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		1		1		1
Interest cost		1		1		2
Expected return on plan assets		(2)		(2)		(2)
Amortization of actuarial loss (gain)		1		1
Net periodic costs		$ 1		$ 1		$ 1

Employee Benefit Plans (Amounts

Employee Benefit Plans (Amounts Recognized in Accumulated Other Comprehensive Income and Regulatory Assets and Liabilities) (Details) - USD ($) $ in Millions	2 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015	Oct. 31, 2015
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract]
Net amount recognized in accumulated other comprehensive (income) loss		$ (3)	$ 11		$ 13
Progress Energy [Member]
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract]
Net amount recognized in accumulated other comprehensive (income) loss		(4)	(1)		$ 10
Pension Plan [Member] | Qualified Plan [Member]
Amounts Recognized in Regulatory Assets and Liabilities [Abstract]
Regulatory assets, net increase (decrease)		(212)	214
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract]
Deferred income tax expense (benefit)			4
Prior year service cost (credit) arising during the year		1	(2)
Amortization of prior year actuarial gains (losses)		(7)	(7)
Net amount recognized in accumulated other comprehensive (income) loss		(6)	(5)
Pension Plan [Member] | Nonqualified Plan [Member]
Amounts Recognized in Regulatory Assets and Liabilities [Abstract]
Regulatory assets, net increase (decrease)		5	(3)
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract]
Deferred income tax expense (benefit)		(1)
Actuarial (gains) losses arising during the year		2	1
Prior year service cost (credit) arising during the year			(1)
Net amount recognized in accumulated other comprehensive (income) loss		1
Pension Plan [Member] | Duke Energy Carolinas [Member] | Qualified Plan [Member]
Amounts Recognized in Regulatory Assets and Liabilities [Abstract]
Regulatory assets, net increase (decrease)		(70)	4
Pension Plan [Member] | Duke Energy Carolinas [Member] | Nonqualified Plan [Member]
Amounts Recognized in Regulatory Assets and Liabilities [Abstract]
Regulatory assets, net increase (decrease)		(1)	(2)
Pension Plan [Member] | Progress Energy [Member] | Qualified Plan [Member]
Amounts Recognized in Regulatory Assets and Liabilities [Abstract]
Regulatory assets, net increase (decrease)		(49)	34
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract]
Deferred income tax expense (benefit)		3
Amortization of prior year actuarial gains (losses)		(7)	(1)
Net amount recognized in accumulated other comprehensive (income) loss		(4)	(1)
Pension Plan [Member] | Progress Energy [Member] | Nonqualified Plan [Member]
Amounts Recognized in Regulatory Assets and Liabilities [Abstract]
Regulatory assets, net increase (decrease)		3	2
Pension Plan [Member] | Duke Energy Progress [Member] | Qualified Plan [Member]
Amounts Recognized in Regulatory Assets and Liabilities [Abstract]
Regulatory assets, net increase (decrease)		(37)	18
Pension Plan [Member] | Duke Energy Progress [Member] | Nonqualified Plan [Member]
Amounts Recognized in Regulatory Assets and Liabilities [Abstract]
Regulatory assets, net increase (decrease)		1	1
Pension Plan [Member] | Duke Energy Florida [Member] | Qualified Plan [Member]
Amounts Recognized in Regulatory Assets and Liabilities [Abstract]
Regulatory assets, net increase (decrease)		(11)	16
Pension Plan [Member] | Duke Energy Florida [Member] | Nonqualified Plan [Member]
Amounts Recognized in Regulatory Assets and Liabilities [Abstract]
Regulatory assets, net increase (decrease)		2	1
Pension Plan [Member] | Duke Energy Ohio [Member] | Qualified Plan [Member]
Amounts Recognized in Regulatory Assets and Liabilities [Abstract]
Regulatory assets, net increase (decrease)		9	2
Pension Plan [Member] | Duke Energy Indiana [Member] | Qualified Plan [Member]
Amounts Recognized in Regulatory Assets and Liabilities [Abstract]
Regulatory assets, net increase (decrease)		(19)	9
Pension Plan [Member] | Duke Energy Indiana [Member] | Nonqualified Plan [Member]
Amounts Recognized in Regulatory Assets and Liabilities [Abstract]
Regulatory assets, net increase (decrease)			(1)
Pension Plan [Member] | Piedmont Natural Gas [Member] | Qualified Plan [Member]
Amounts Recognized in Regulatory Assets and Liabilities [Abstract]
Regulatory assets, net increase (decrease)	$ 34	(64)		$ 35		$ 20
Other Post-Retirement Benefit Plans [Member]
Amounts Recognized in Regulatory Assets and Liabilities [Abstract]
Regulatory assets, net increase (decrease)		71	53
Regulatory liabilities, net increase (decrease)		(27)	(114)
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract]
Deferred income tax expense (benefit)		(1)	(2)
Actuarial (gains) losses arising during the year			3
Amortization of prior year prior service credit		3	1
Net amount recognized in accumulated other comprehensive (income) loss		2	2
Other Post-Retirement Benefit Plans [Member] | Duke Energy Carolinas [Member]
Amounts Recognized in Regulatory Assets and Liabilities [Abstract]
Regulatory liabilities, net increase (decrease)		(2)	(22)
Other Post-Retirement Benefit Plans [Member] | Progress Energy [Member]
Amounts Recognized in Regulatory Assets and Liabilities [Abstract]
Regulatory assets, net increase (decrease)		81	47
Regulatory liabilities, net increase (decrease)			(51)
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract]
Amortization of prior year prior service credit			1
Net amount recognized in accumulated other comprehensive (income) loss			1
Other Post-Retirement Benefit Plans [Member] | Duke Energy Progress [Member]
Amounts Recognized in Regulatory Assets and Liabilities [Abstract]
Regulatory assets, net increase (decrease)		42	38
Regulatory liabilities, net increase (decrease)			(25)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Florida [Member]
Amounts Recognized in Regulatory Assets and Liabilities [Abstract]
Regulatory assets, net increase (decrease)		39	9
Regulatory liabilities, net increase (decrease)			(26)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Ohio [Member]
Amounts Recognized in Regulatory Assets and Liabilities [Abstract]
Regulatory liabilities, net increase (decrease)		(3)	(2)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Indiana [Member]
Amounts Recognized in Regulatory Assets and Liabilities [Abstract]
Regulatory assets, net increase (decrease)		(5)	(6)
Regulatory liabilities, net increase (decrease)		(7)	$ (12)
Other Post-Retirement Benefit Plans [Member] | Piedmont Natural Gas [Member]
Amounts Recognized in Regulatory Assets and Liabilities [Abstract]
Regulatory assets, net increase (decrease)	$ (1)	$ (11)		$ 2		$ 1

Employee Benefit Plans (Project

Employee Benefit Plans (Projected Benefit Obligations Reconciliation of Funded Status to Net Amount Recognized) (Details) - USD ($) $ in Millions	2 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015	Oct. 31, 2015
Pension Plan [Member]
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions		$ 19	$ 155		$ 302
Pension Plan [Member] | Qualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		8,131	7,727
Obligation assumed from acquisition			352
Service cost		159	147		159
Interest cost		328	335		324
Actuarial loss (gain)		455	307
Plan amendments		(61)	(52)
Benefits paid		(537)	(679)
Impact of settlements		(27)	(6)
Obligation at measurement date	$ 8,131	8,448	8,131		7,727
Accumulated benefit obligation at measurement date	8,006	8,369	8,006
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		8,531	8,136
Assets received from acquisition			343
Employer contributions		19	155
Actual return on plan assets		1,017	582
Benefits paid		(537)	(679)
Impact of Settlements		(27)	(6)
Plan assets at measurement date	8,531	9,003	8,531		8,136
Funded status of plan	400	555	400
Pension Plan [Member] | Nonqualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		332	341
Obligation assumed from acquisition			5
Service cost		2	2		3
Interest cost		13	14		13
Actuarial loss (gain)		15	4
Plan amendments			(2)
Benefits paid		(31)	(32)
Obligation at measurement date	332	331	332		341
Accumulated benefit obligation at measurement date	332	331	332
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions		31	32
Benefits paid		(31)	(32)
Pension Plan [Member] | Duke Energy Carolinas [Member]
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions			43		91
Pension Plan [Member] | Duke Energy Carolinas [Member] | Qualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		1,952	1,995
Service cost		48	48		50
Interest cost		79	86		83
Actuarial loss (gain)		68	46
Transfers		27	14
Plan amendments			(3)
Benefits paid		(145)	(234)
Obligation at measurement date	1,952	2,029	1,952		1,995
Accumulated benefit obligation at measurement date	1,952	2,029	1,952
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		2,225	2,243
Employer contributions			43
Actual return on plan assets		265	159
Benefits paid		(145)	(234)
Transfer of plan assets		27	14
Plan assets at measurement date	2,225	2,372	2,225		2,243
Funded status of plan	273	343	273
Pension Plan [Member] | Duke Energy Carolinas [Member] | Nonqualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		14	16
Service cost		1
Interest cost		1	1		1
Actuarial loss (gain)			(1)
Benefits paid		(2)	(2)
Obligation at measurement date	14	14	14		16
Accumulated benefit obligation at measurement date	14	14	14
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions		2	2
Benefits paid		(2)	(2)
Pension Plan [Member] | Progress Energy [Member]
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions			43		83
Pension Plan [Member] | Progress Energy [Member] | Qualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		2,512	2,451
Service cost		45	42		44
Interest cost		100	106		104
Actuarial loss (gain)		158	111
Transfers		(32)	(3)
Benefits paid		(146)	(195)
Obligation at measurement date	2,512	2,637	2,512		2,451
Accumulated benefit obligation at measurement date	2,479	2,601	2,479
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		2,675	2,640
Employer contributions			43
Actual return on plan assets		317	190
Benefits paid		(146)	(195)
Transfer of plan assets		(32)	(3)
Plan assets at measurement date	2,675	2,814	2,675		2,640
Funded status of plan	163	177	163
Pension Plan [Member] | Progress Energy [Member] | Nonqualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		114	112
Service cost					1
Interest cost		5	5		4
Actuarial loss (gain)		5	5
Benefits paid		(8)	(8)
Obligation at measurement date	114	116	114		112
Accumulated benefit obligation at measurement date	114	116	114
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions		8	8
Benefits paid		(8)	(8)
Pension Plan [Member] | Duke Energy Progress [Member]
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions			24		42
Pension Plan [Member] | Duke Energy Progress [Member] | Qualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		1,158	1,143
Service cost		26	24		23
Interest cost		47	49		48
Actuarial loss (gain)		57	52
Transfers		(2)	(3)
Benefits paid		(75)	(107)
Obligation at measurement date	1,158	1,211	1,158		1,143
Accumulated benefit obligation at measurement date	1,158	1,211	1,158
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		1,290	1,284
Employer contributions			24
Actual return on plan assets		153	92
Benefits paid		(75)	(107)
Transfer of plan assets		(2)	(3)
Plan assets at measurement date	1,290	1,366	1,290		1,284
Funded status of plan	132	155	132
Pension Plan [Member] | Duke Energy Progress [Member] | Nonqualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		33	33
Interest cost		1	1		1
Actuarial loss (gain)		4	2
Benefits paid		(3)	(3)
Obligation at measurement date	33	35	33		33
Accumulated benefit obligation at measurement date	33	35	33
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions		3	3
Benefits paid		(3)	(3)
Pension Plan [Member] | Duke Energy Florida [Member]
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions			20		40
Pension Plan [Member] | Duke Energy Florida [Member] | Qualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		1,323	1,276
Service cost		19	19		20
Interest cost		53	55		54
Actuarial loss (gain)		99	57
Transfers		(15)
Benefits paid		(69)	(84)
Obligation at measurement date	1,323	1,410	1,323		1,276
Accumulated benefit obligation at measurement date	1,290	1,375	1,290
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		1,352	1,321
Employer contributions			20
Actual return on plan assets		161	95
Benefits paid		(69)	(84)
Transfer of plan assets		(15)
Plan assets at measurement date	1,352	1,429	1,352		1,321
Funded status of plan	29	19	29
Pension Plan [Member] | Duke Energy Florida [Member] | Nonqualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		46	46
Interest cost		2	2		2
Actuarial loss (gain)		2	1
Benefits paid		(3)	(3)
Obligation at measurement date	46	47	46		46
Accumulated benefit obligation at measurement date	46	47	46
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions		3	3
Benefits paid		(3)	(3)
Pension Plan [Member] | Duke Energy Ohio [Member]
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions		4	5		8
Pension Plan [Member] | Duke Energy Ohio [Member] | Qualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		447	453
Service cost		4	4		4
Interest cost		18	19		18
Actuarial loss (gain)		35	13
Transfers		12	(3)
Plan amendments			(3)
Benefits paid		(37)	(36)
Obligation at measurement date	447	479	447		453
Accumulated benefit obligation at measurement date	436	468	436
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		428	433
Employer contributions		4	5
Actual return on plan assets		51	29
Benefits paid		(37)	(36)
Transfer of plan assets		12	(3)
Plan assets at measurement date	428	458	428		433
Funded status of plan	(19)	(21)	(19)
Pension Plan [Member] | Duke Energy Ohio [Member] | Nonqualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		4	4
Obligation at measurement date	4	4	4		4
Accumulated benefit obligation at measurement date	4	4	4
Pension Plan [Member] | Duke Energy Indiana [Member]
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions			9		19
Pension Plan [Member] | Duke Energy Indiana [Member] | Qualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		658	649
Service cost		9	9		10
Interest cost		26	28		27
Actuarial loss (gain)		26	41
Plan amendments			(15)
Benefits paid		(50)	(54)
Obligation at measurement date	658	669	658		649
Accumulated benefit obligation at measurement date	649	652	649
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		657	655
Employer contributions			9
Actual return on plan assets		77	47
Benefits paid		(50)	(54)
Plan assets at measurement date	657	684	657		655
Funded status of plan	(1)	15	(1)
Pension Plan [Member] | Duke Energy Indiana [Member] | Nonqualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		3	5
Actuarial loss (gain)			(2)
Obligation at measurement date	3	3	3		5
Accumulated benefit obligation at measurement date	3	3	3
Pension Plan [Member] | Piedmont Natural Gas [Member]
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions	10	11		$ 10		$ 10
Pension Plan [Member] | Piedmont Natural Gas [Member] | Qualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	352	344		312
Service cost	2	10		11		11
Interest cost	2	14		9		12
Actuarial loss (gain)	(5)	38		34
Plan amendments		(61)
Benefits paid	(1)	(5)		(14)
Impact of settlements	(6)	(27)
Obligation at measurement date	344	313	344	352		312
Accumulated benefit obligation at measurement date	289	313	289	296
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	343	346		329
Employer contributions	10	11		10
Actual return on plan assets		43		18
Benefits paid	(1)	(5)		(14)
Impact of Settlements	(6)	(27)
Plan assets at measurement date	346	368	346	343		329
Funded status of plan	2	55	2	(9)
Pension Plan [Member] | Piedmont Natural Gas [Member] | Nonqualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	5	4		6
Actuarial loss (gain)	(1)
Impact of settlements				(1)
Obligation at measurement date	4	4	4	5		6
Accumulated benefit obligation at measurement date		4		5
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date				1
Impact of Settlements				(1)
Plan assets at measurement date						1
Other Post-Retirement Benefit Plans [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		868	828
Obligation assumed from acquisition			39
Service cost		4	3		6
Interest cost		34	35		36
Plan participants' contributions		17	19
Actuarial loss (gain)		4	33
Plan amendments		(28)	(1)
Benefits paid		(86)	(88)
Obligation at measurement date	868	813	868		828
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		244	208
Assets received from acquisition			29
Employer contributions		25	62
Actual return on plan assets		25	14
Benefits paid		(86)	(88)
Plan participants' contributions		17	19
Plan assets at measurement date	244	225	244		208
Other Post-Retirement Benefit Plans [Member] | Duke Energy Carolinas [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		201	200
Service cost		1	1		1
Interest cost		8	8		9
Plan participants' contributions		3	3
Actuarial loss (gain)		(3)	5
Transfers		2	1
Plan amendments		(5)
Benefits paid		(18)	(17)
Obligation at measurement date	201	189	201		200
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		137	134
Employer contributions			9
Actual return on plan assets		15	8
Benefits paid		(18)	(17)
Employer contributions (reimbursements)		(4)
Plan participants' contributions		3	3
Plan assets at measurement date	137	133	137		134
Other Post-Retirement Benefit Plans [Member] | Progress Energy [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		357	354
Service cost			1		1
Interest cost		13	15		15
Plan participants' contributions		6	7
Actuarial loss (gain)		4	16
Transfers		(1)
Plan amendments		(3)
Benefits paid		(34)	(36)
Obligation at measurement date	357	342	357		354
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		1
Employer contributions		26	29
Actual return on plan assets		1	1
Benefits paid		(34)	(36)
Plan participants' contributions		6	7
Plan assets at measurement date	1		1
Other Post-Retirement Benefit Plans [Member] | Duke Energy Progress [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		191	188
Service cost					1
Interest cost		7	8		8
Plan participants' contributions		3	4
Actuarial loss (gain)		1	8
Plan amendments		(1)
Benefits paid		(17)	(17)
Obligation at measurement date	191	184	191		188
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions		14	13
Benefits paid		(17)	(17)
Plan participants' contributions		3	4
Other Post-Retirement Benefit Plans [Member] | Duke Energy Florida [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		164	164
Service cost			1		1
Interest cost		6	7		7
Plan participants' contributions		3	3
Actuarial loss (gain)		3	8
Transfers		(1)
Plan amendments		(2)
Benefits paid		(17)	(19)
Obligation at measurement date	164	156	164		164
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date			1
Employer contributions		14	15
Benefits paid		(17)	(19)
Plan participants' contributions		3	3
Plan assets at measurement date					1
Other Post-Retirement Benefit Plans [Member] | Duke Energy Ohio [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		32	35
Interest cost		1	1		2
Plan participants' contributions		1	1
Transfers		1
Plan amendments		(2)	(1)
Benefits paid		(3)	(4)
Obligation at measurement date	32	30	32		35
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		7	8
Employer contributions			1
Actual return on plan assets		2	1
Benefits paid		(3)	(4)
Plan participants' contributions		1	1
Plan assets at measurement date	7	7	7		8
Other Post-Retirement Benefit Plans [Member] | Duke Energy Indiana [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		83	87
Service cost					1
Interest cost		3	4		4
Plan participants' contributions		2	2
Actuarial loss (gain)		3	3
Plan amendments		(2)
Benefits paid		(11)	(13)
Obligation at measurement date	83	78	83		87
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		22	19
Employer contributions			12
Actual return on plan assets		1	2
Benefits paid		(11)	(13)
Employer contributions (reimbursements)		(3)
Plan participants' contributions		2	2
Plan assets at measurement date	22	11	22		$ 19
Other Post-Retirement Benefit Plans [Member] | Piedmont Natural Gas [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	39	39		38
Service cost		1		1		1
Interest cost		1		1		2
Actuarial loss (gain)		1		2
Plan amendments		(9)
Benefits paid		(1)		(3)
Obligation at measurement date	39	32	39	39		38
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	29	29		28
Employer contributions				3
Actual return on plan assets		3		1
Benefits paid		(1)		(3)
Plan assets at measurement date	$ 29	$ 31	$ 29	$ 29		$ 28

Employee Benefit Plans (Amou149

Employee Benefit Plans (Amounts Recognized in Consolidated Balance Sheets) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Noncurrent pension liability	$ 1,103	$ 1,111
Regulatory assets	13,879	13,901
Regulatory Liabilities	15,732	7,290
Duke Energy Carolinas [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Noncurrent pension liability	95	97
Regulatory assets	3,152	3,397
Regulatory Liabilities	6,357	3,001
Progress Energy [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Noncurrent pension liability	545	547
Regulatory assets	6,751	6,123
Regulatory Liabilities	5,519	2,584
Duke Energy Progress [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Noncurrent pension liability	248	252
Regulatory assets	3,859	3,431
Regulatory Liabilities	4,138	2,104
Duke Energy Florida [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Noncurrent pension liability	264	262
Regulatory assets	2,892	2,693
Regulatory Liabilities	1,381	479
Duke Energy Ohio [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Noncurrent pension liability	59	56
Regulatory assets	494	557
Regulatory Liabilities	927	257
Duke Energy Indiana [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Noncurrent pension liability	76	71
Regulatory assets	1,143	1,222
Regulatory Liabilities	1,747	788
Piedmont Natural Gas [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Noncurrent pension liability	5	14
Regulatory assets	378	497
Regulatory Liabilities	1,144	608
Pension Plan [Member] | Qualified Plan [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Prefunded pension	680	518
Noncurrent pension liability	125	118
Net amount recognized	555	400
Regulatory assets	1,886	2,098
Accumulated Other Comprehensive Income (Loss) [Abstract]
Deferred income tax asset	(41)	(41)
Prior year service cost (credit) arising during the year	(5)	(6)
Net actuarial loss (gain)	116	123
Net amount recognized in accumulated other comprehensive income (loss)	70	76
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss	132	147
Unrecognized prior service (credit) cost	(32)	(24)
Pension Plan [Member] | Nonqualified Plan [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Current pension liability	23	28
Noncurrent pension liability	308	304
Total accrued pension liability	331	332
Regulatory assets	78	73
Accumulated Other Comprehensive Income (Loss) [Abstract]
Deferred income tax asset	(4)	(3)
Prior year service cost (credit) arising during the year	(1)	(1)
Net actuarial loss (gain)	12	10
Net amount recognized in accumulated other comprehensive income (loss)	7	6
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss	8	7
Unrecognized prior service (credit) cost	(2)	(2)
Pension Plan [Member] | Duke Energy Carolinas [Member] | Qualified Plan [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Prefunded pension	343	273
Net amount recognized	343	273
Regulatory assets	406	476
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss	29	31
Unrecognized prior service (credit) cost	(8)	(8)
Pension Plan [Member] | Duke Energy Carolinas [Member] | Nonqualified Plan [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Current pension liability	2	2
Noncurrent pension liability	12	12
Total accrued pension liability	14	14
Regulatory assets	4	5
Pension Plan [Member] | Progress Energy [Member] | Qualified Plan [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Prefunded pension	245	225
Noncurrent pension liability	68	62
Net amount recognized	177	163
Regulatory assets	756	805
Accumulated Other Comprehensive Income (Loss) [Abstract]
Deferred income tax asset	(3)	(6)
Net actuarial loss (gain)	9	16
Net amount recognized in accumulated other comprehensive income (loss)	6	10
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss	44	52
Unrecognized prior service (credit) cost	(3)	(3)
Pension Plan [Member] | Progress Energy [Member] | Nonqualified Plan [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Current pension liability	8	8
Noncurrent pension liability	108	106
Total accrued pension liability	116	114
Regulatory assets	21	18
Accumulated Other Comprehensive Income (Loss) [Abstract]
Deferred income tax asset	(3)	(3)
Net actuarial loss (gain)	9	9
Net amount recognized in accumulated other comprehensive income (loss)	6	6
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss	2	2
Pension Plan [Member] | Duke Energy Progress [Member] | Qualified Plan [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Prefunded pension	155	132
Net amount recognized	155	132
Regulatory assets	341	378
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss	21	23
Unrecognized prior service (credit) cost	(2)	(2)
Pension Plan [Member] | Duke Energy Progress [Member] | Nonqualified Plan [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Current pension liability	3	2
Noncurrent pension liability	32	31
Total accrued pension liability	35	33
Regulatory assets	8	7
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss	1	1
Pension Plan [Member] | Duke Energy Florida [Member] | Qualified Plan [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Prefunded pension	87	91
Noncurrent pension liability	68	62
Net amount recognized	19	29
Regulatory assets	415	426
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss	23	29
Unrecognized prior service (credit) cost	(1)	(1)
Pension Plan [Member] | Duke Energy Florida [Member] | Nonqualified Plan [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Current pension liability	3	3
Noncurrent pension liability	44	43
Total accrued pension liability	47	46
Regulatory assets	13	11
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss	1	1
Pension Plan [Member] | Duke Energy Ohio [Member] | Qualified Plan [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Prefunded pension	8	6
Noncurrent pension liability	29	25
Net amount recognized	(21)	(19)
Regulatory assets	90	81
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss	5	5
Pension Plan [Member] | Duke Energy Ohio [Member] | Nonqualified Plan [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Noncurrent pension liability	4	4
Total accrued pension liability	4	4
Regulatory assets	1	1
Pension Plan [Member] | Duke Energy Indiana [Member] | Qualified Plan [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Prefunded pension	16
Noncurrent pension liability	1	1
Net amount recognized	15	(1)
Regulatory assets	152	171
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss	7	8
Unrecognized prior service (credit) cost	(2)	(2)
Pension Plan [Member] | Duke Energy Indiana [Member] | Nonqualified Plan [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Noncurrent pension liability	3	3
Total accrued pension liability	3	3
Pension Plan [Member] | Piedmont Natural Gas [Member] | Qualified Plan [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Prefunded pension	55	3
Net amount recognized	55	3
Regulatory assets	73	137
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss	11	13
Unrecognized prior service (credit) cost	(9)	(2)
Pension Plan [Member] | Piedmont Natural Gas [Member] | Nonqualified Plan [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Noncurrent pension liability	4	4
Total accrued pension liability	4	4
Regulatory assets	1	1
Other Post-Retirement Benefit Plans [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Current pension liability	36	38
Noncurrent pension liability	552	586
Total accrued pension liability	588	624
Regulatory assets	125	54
Regulatory Liabilities	147	174
Accumulated Other Comprehensive Income (Loss) [Abstract]
Deferred income tax liability	4	5
Prior year service cost (credit) arising during the year	(2)	(5)
Net actuarial loss (gain)	(10)	(10)
Net amount recognized in accumulated other comprehensive income (loss)	(8)	(10)
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss	5	10
Unrecognized prior service (credit) cost	(19)	(115)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Carolinas [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Noncurrent pension liability	56	64
Total accrued pension liability	56	64
Regulatory Liabilities	44	46
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss	3	(2)
Unrecognized prior service (credit) cost	(5)	(10)
Other Post-Retirement Benefit Plans [Member] | Progress Energy [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Current pension liability	29	31
Noncurrent pension liability	313	325
Total accrued pension liability	342	356
Regulatory assets	129	48
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss	1	21
Unrecognized prior service (credit) cost	(7)	(85)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Progress [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Current pension liability	15	17
Noncurrent pension liability	169	174
Total accrued pension liability	184	191
Regulatory assets	80	38
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss		12
Unrecognized prior service (credit) cost	(1)	(55)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Florida [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Current pension liability	14	15
Noncurrent pension liability	142	149
Total accrued pension liability	156	164
Regulatory assets	49	10
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss	1	9
Unrecognized prior service (credit) cost	(6)	(30)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Ohio [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Current pension liability	2	2
Noncurrent pension liability	21	23
Total accrued pension liability	23	25
Regulatory Liabilities	16	19
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss		(2)
Unrecognized prior service (credit) cost	(1)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Indiana [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Noncurrent pension liability	67	63
Total accrued pension liability	67	63
Regulatory assets	46	51
Regulatory Liabilities	64	71
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss		(6)
Unrecognized prior service (credit) cost	(1)	(1)
Other Post-Retirement Benefit Plans [Member] | Piedmont Natural Gas [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Noncurrent pension liability	1	10
Total accrued pension liability	1	10
Regulatory assets	(4)	$ 7
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized prior service (credit) cost	$ (2)

Employee Benefit Plans (Informa

Employee Benefit Plans (Information For Plans with Accumulated Benefit Obligation in Excess of Plan Assets) (Details) - Pension Plan [Member] - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Qualified Plan [Member]
Information For Plans With Accumulated Benefit Obligation In Excess Of Plan Assets [Abstract]
Projected benefit obligation	$ 1,386	$ 1,299
Accumulated benefit obligation	1,326	1,239
Fair value of plan assets	1,260	1,182
Nonqualified Plan [Member]
Information For Plans With Accumulated Benefit Obligation In Excess Of Plan Assets [Abstract]
Projected benefit obligation	331	332
Accumulated benefit obligation	331	332
Duke Energy Carolinas [Member] | Nonqualified Plan [Member]
Information For Plans With Accumulated Benefit Obligation In Excess Of Plan Assets [Abstract]
Projected benefit obligation	14	14
Accumulated benefit obligation	14	14
Progress Energy [Member] | Qualified Plan [Member]
Information For Plans With Accumulated Benefit Obligation In Excess Of Plan Assets [Abstract]
Projected benefit obligation	718	665
Accumulated benefit obligation	683	633
Fair value of plan assets	650	604
Progress Energy [Member] | Nonqualified Plan [Member]
Information For Plans With Accumulated Benefit Obligation In Excess Of Plan Assets [Abstract]
Projected benefit obligation	116	114
Accumulated benefit obligation	116	114
Duke Energy Progress [Member] | Nonqualified Plan [Member]
Information For Plans With Accumulated Benefit Obligation In Excess Of Plan Assets [Abstract]
Projected benefit obligation	35	33
Accumulated benefit obligation	35	33
Duke Energy Florida [Member] | Qualified Plan [Member]
Information For Plans With Accumulated Benefit Obligation In Excess Of Plan Assets [Abstract]
Projected benefit obligation	718	665
Accumulated benefit obligation	683	633
Fair value of plan assets	650	604
Duke Energy Florida [Member] | Nonqualified Plan [Member]
Information For Plans With Accumulated Benefit Obligation In Excess Of Plan Assets [Abstract]
Projected benefit obligation	47	46
Accumulated benefit obligation	47	46
Duke Energy Ohio [Member] | Qualified Plan [Member]
Information For Plans With Accumulated Benefit Obligation In Excess Of Plan Assets [Abstract]
Projected benefit obligation	337	311
Accumulated benefit obligation	326	299
Fair value of plan assets	308	286
Duke Energy Ohio [Member] | Nonqualified Plan [Member]
Information For Plans With Accumulated Benefit Obligation In Excess Of Plan Assets [Abstract]
Projected benefit obligation	4	4
Accumulated benefit obligation	4	4
Duke Energy Indiana [Member] | Nonqualified Plan [Member]
Information For Plans With Accumulated Benefit Obligation In Excess Of Plan Assets [Abstract]
Projected benefit obligation	3	3
Accumulated benefit obligation	3	3
Piedmont Natural Gas [Member] | Nonqualified Plan [Member]
Information For Plans With Accumulated Benefit Obligation In Excess Of Plan Assets [Abstract]
Projected benefit obligation	4	4
Accumulated benefit obligation	$ 4	$ 4

Employee Benefit Plans (Assumpt

Employee Benefit Plans (Assumptions Used For Pension Benefits Accounting) (Details)	2 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015	Oct. 31, 2015
Pension Plan [Member] | Qualified Plan [Member]
Benefit Obligations [Abstract]
Discount rate	4.10%	3.60%	4.10%		4.40%
Net Periodic Benefit Cost [Abstract]
Discount rate		4.10%	4.40%		4.10%
Expected long-term rate of return on plan assets					6.50%
Pension Plan [Member] | Nonqualified Plan [Member]
Benefit Obligations [Abstract]
Discount rate	4.10%	3.60%	4.10%		4.40%
Salary increase	4.40%		4.40%		4.40%
Net Periodic Benefit Cost [Abstract]
Discount rate		4.10%	4.40%		4.10%
Salary increase		4.40%	4.40%		4.40%
Pension Plan [Member] | Minimum [Member] | Qualified Plan [Member]
Benefit Obligations [Abstract]
Salary increase	4.00%	3.50%	4.00%		4.00%
Net Periodic Benefit Cost [Abstract]
Discount rate
Salary increase		4.00%	4.00%		4.00%
Expected long-term rate of return on plan assets		6.50%	6.50%
Pension Plan [Member] | Minimum [Member] | Nonqualified Plan [Member]
Benefit Obligations [Abstract]
Salary increase		3.50%
Pension Plan [Member] | Maximum [Member] | Qualified Plan [Member]
Benefit Obligations [Abstract]
Salary increase	4.50%	4.00%	4.50%		4.40%
Net Periodic Benefit Cost [Abstract]
Salary increase		4.50%	4.40%		4.40%
Expected long-term rate of return on plan assets		6.75%	6.75%
Pension Plan [Member] | Maximum [Member] | Nonqualified Plan [Member]
Benefit Obligations [Abstract]
Salary increase		4.00%
Pension Plan [Member] | Piedmont Natural Gas [Member] | Qualified Plan [Member]
Benefit Obligations [Abstract]
Discount rate	4.10%		4.10%	3.80%		4.34%
Salary increase	4.50%		4.50%	4.05%		4.07%
Net Periodic Benefit Cost [Abstract]
Discount rate	3.80%			4.34%		4.13%
Salary increase	4.05%			4.07%		3.68%
Expected long-term rate of return on plan assets	6.75%			7.25%		7.50%
Pension Plan [Member] | Piedmont Natural Gas [Member] | Nonqualified Plan [Member]
Benefit Obligations [Abstract]
Discount rate	4.10%		4.10%	3.80%		3.85%
Net Periodic Benefit Cost [Abstract]
Discount rate	3.80%			3.85%		3.69%
Other Post-Retirement Benefit Plans [Member]
Benefit Obligations [Abstract]
Discount rate	4.10%	3.60%	4.10%		4.40%
Net Periodic Benefit Cost [Abstract]
Discount rate		4.10%	4.40%		4.10%
Expected long-term rate of return on plan assets		6.50%	6.50%		6.50%
Assumed tax rate		35.00%	35.00%		35.00%
Other Post-Retirement Benefit Plans [Member] | Piedmont Natural Gas [Member]
Benefit Obligations [Abstract]
Discount rate	4.10%		4.10%	3.80%		4.38%
Net Periodic Benefit Cost [Abstract]
Discount rate	3.80%			4.38%		4.03%
Expected long-term rate of return on plan assets	6.75%			7.25%		7.50%

Employee Benefit Plans (Assumed

Employee Benefit Plans (Assumed Health Care Cost Trend Rates) (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate assumed for next year	7.00%	7.00%
Rate to which the cost trend is assumed to decline (the ultimate trend rate)	4.75%	4.75%
Year that the rate reaches the ultimate trend rate	2,024	2,023

Employee Benefit Plans (Sensiti

Employee Benefit Plans (Sensitivity to Changes in Assumed Health Care Cost Trend Rates) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)
Defined Benefit Plan Disclosure [Line Items]
Effect on total service and interest costs - 1 Percentage Point Increase	$ 1
Effect on post-retirement benefit obligation - 1 Percentage Point Increase	27
Effect on total service and interest costs - 1 Percentage Point Decrease	(1)
Effect on post-retirement benefit obligation - 1 Percentage Point Decrease	(24)
Duke Energy Carolinas [Member]
Defined Benefit Plan Disclosure [Line Items]
Effect on post-retirement benefit obligation - 1 Percentage Point Increase	6
Effect on post-retirement benefit obligation - 1 Percentage Point Decrease	(6)
Progress Energy [Member]
Defined Benefit Plan Disclosure [Line Items]
Effect on total service and interest costs - 1 Percentage Point Increase	1
Effect on post-retirement benefit obligation - 1 Percentage Point Increase	11
Effect on post-retirement benefit obligation - 1 Percentage Point Decrease	(10)
Duke Energy Progress [Member]
Defined Benefit Plan Disclosure [Line Items]
Effect on total service and interest costs - 1 Percentage Point Increase	1
Effect on post-retirement benefit obligation - 1 Percentage Point Increase	6
Effect on post-retirement benefit obligation - 1 Percentage Point Decrease	(5)
Duke Energy Florida [Member]
Defined Benefit Plan Disclosure [Line Items]
Effect on post-retirement benefit obligation - 1 Percentage Point Increase	5
Effect on post-retirement benefit obligation - 1 Percentage Point Decrease	(5)
Duke Energy Ohio [Member]
Defined Benefit Plan Disclosure [Line Items]
Effect on post-retirement benefit obligation - 1 Percentage Point Increase	1
Effect on post-retirement benefit obligation - 1 Percentage Point Decrease	(1)
Duke Energy Indiana [Member]
Defined Benefit Plan Disclosure [Line Items]
Effect on post-retirement benefit obligation - 1 Percentage Point Increase	3
Effect on post-retirement benefit obligation - 1 Percentage Point Decrease	(2)
Piedmont Natural Gas [Member]
Defined Benefit Plan Disclosure [Line Items]
Effect on post-retirement benefit obligation - 1 Percentage Point Increase	1
Effect on post-retirement benefit obligation - 1 Percentage Point Decrease	$ (1)

Employee Benefit Plans (Expecte

Employee Benefit Plans (Expected Benefit Payments) (Details) $ in Millions	Dec. 31, 2017USD ($)
Pension Plan [Member] | Qualified Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2,018	$ 642
2,019	644
2,020	661
2,021	666
2,022	672
2023-2027	3,099
Pension Plan [Member] | Nonqualified Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2,018	23
2,019	21
2,020	21
2,021	22
2,022	25
2023-2027	117
Pension Plan [Member] | Duke Energy Carolinas [Member] | Qualified Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2,018	185
2,019	185
2,020	195
2,021	194
2,022	197
2023-2027	865
Pension Plan [Member] | Duke Energy Carolinas [Member] | Nonqualified Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2,018	2
2,019	1
2,020	1
2,021	1
2,022	1
2023-2027	6
Pension Plan [Member] | Progress Energy [Member] | Qualified Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2,018	161
2,019	164
2,020	172
2,021	175
2,022	176
2023-2027	888
Pension Plan [Member] | Progress Energy [Member] | Nonqualified Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2,018	8
2,019	8
2,020	8
2,021	8
2,022	8
2023-2027	36
Pension Plan [Member] | Duke Energy Progress [Member] | Qualified Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2,018	85
2,019	86
2,020	90
2,021	93
2,022	92
2023-2027	449
Pension Plan [Member] | Duke Energy Progress [Member] | Nonqualified Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2,018	3
2,019	2
2,020	2
2,021	2
2,022	2
2023-2027	11
Pension Plan [Member] | Duke Energy Florida [Member] | Qualified Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2,018	75
2,019	77
2,020	80
2,021	81
2,022	83
2023-2027	435
Pension Plan [Member] | Duke Energy Florida [Member] | Nonqualified Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2,018	3
2,019	3
2,020	3
2,021	3
2,022	3
2023-2027	15
Pension Plan [Member] | Duke Energy Ohio [Member] | Qualified Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2,018	36
2,019	36
2,020	36
2,021	37
2,022	36
2023-2027	166
Pension Plan [Member] | Duke Energy Ohio [Member] | Nonqualified Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2023-2027	1
Pension Plan [Member] | Duke Energy Indiana [Member] | Qualified Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2,018	47
2,019	46
2,020	44
2,021	44
2,022	44
2023-2027	210
Pension Plan [Member] | Duke Energy Indiana [Member] | Nonqualified Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2023-2027	1
Pension Plan [Member] | Piedmont Natural Gas [Member] | Qualified Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2,018	29
2,019	26
2,020	24
2,021	24
2,022	23
2023-2027	103
Pension Plan [Member] | Piedmont Natural Gas [Member] | Nonqualified Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2023-2027	2
Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2,018	78
2,019	76
2,020	73
2,021	71
2,022	68
2023-2027	290
Other Post-Retirement Benefit Plans [Member] | Duke Energy Carolinas [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2,018	17
2,019	17
2,020	17
2,021	17
2,022	17
2023-2027	70
Other Post-Retirement Benefit Plans [Member] | Progress Energy [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2,018	30
2,019	29
2,020	29
2,021	28
2,022	27
2023-2027	117
Other Post-Retirement Benefit Plans [Member] | Duke Energy Progress [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2,018	16
2,019	15
2,020	15
2,021	15
2,022	14
2023-2027	63
Other Post-Retirement Benefit Plans [Member] | Duke Energy Florida [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2,018	14
2,019	14
2,020	14
2,021	13
2,022	13
2023-2027	54
Other Post-Retirement Benefit Plans [Member] | Duke Energy Ohio [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2,018	3
2,019	3
2,020	3
2,021	3
2,022	3
2023-2027	12
Other Post-Retirement Benefit Plans [Member] | Duke Energy Indiana [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2,018	9
2,019	9
2,020	8
2,021	7
2,022	7
2023-2027	29
Other Post-Retirement Benefit Plans [Member] | Piedmont Natural Gas [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2,018	2
2,019	2
2,020	2
2,021	3
2,022	3
2023-2027	$ 13

Employee Benefit Plans (Target

Employee Benefit Plans (Target and Actual Asset Allocations) (Details)	Dec. 31, 2017	Dec. 31, 2016
Master Trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual asset allocation	100.00%	100.00%
Target allocation	100.00%
Master Trust [Member] | US Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual asset allocation	11.00%	11.00%
Target allocation	10.00%
Master Trust [Member] | Non US Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual asset allocation	8.00%	8.00%
Target allocation	8.00%
Master Trust [Member] | Global Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual asset allocation	10.00%	10.00%
Target allocation	10.00%
Master Trust [Member] | Global Private Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual asset allocation	2.00%	2.00%
Target allocation	3.00%
Master Trust [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual asset allocation	63.00%	63.00%
Target allocation	63.00%
Master Trust [Member] | Hedge Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual asset allocation	2.00%	2.00%
Target allocation	2.00%
Master Trust [Member] | Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual asset allocation	2.00%	2.00%
Target allocation	2.00%
Master Trust [Member] | Other Global Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual asset allocation	2.00%	2.00%
Target allocation	2.00%
OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual asset allocation	100.00%	100.00%
Target allocation	100.00%
OPEB [Member] | US Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual asset allocation	41.00%	39.00%
Target allocation	32.00%
OPEB [Member] | Non US Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual asset allocation	8.00%
Target allocation	6.00%
OPEB [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual asset allocation	36.00%	37.00%
Target allocation	45.00%
OPEB [Member] | Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual asset allocation	2.00%	2.00%
Target allocation	2.00%
OPEB [Member] | Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual asset allocation	13.00%	22.00%
Target allocation	15.00%
Piedmont Pension and OPEB Assets [Member] | US Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual asset allocation		61.00%
Target allocation		60.00%
Piedmont Pension and OPEB Assets [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual asset allocation		39.00%
Target allocation		40.00%

Employee Benefit Plans (Fair Va

Employee Benefit Plans (Fair Value Measurements of Plan Assets - Master Retirement Trust) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	$ 28	$ 38	$ 31
Master Trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	9,114	8,655
Alternative Investment, Fair Value Disclosure	1,345	1,300
Master Trust [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	2,189	1,929
Master Trust [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	5,552	5,388
Master Trust [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	28	38
Master Trust [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	2,823	2,472
Alternative Investment, Fair Value Disclosure	847	759
Master Trust [Member] | Equity Securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	1,976	1,677
Master Trust [Member] | Equity Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets		27
Master Trust [Member] | Equity Securities [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets		9
Master Trust [Member] | Corporate Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	4,694	4,330
Master Trust [Member] | Corporate Debt Securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets		8
Master Trust [Member] | Corporate Debt Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	4,694	4,322
Master Trust [Member] | Short Term Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	246	476
Master Trust [Member] | Short Term Investments [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	192	211
Master Trust [Member] | Short Term Investments [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	54	265
Master Trust [Member] | Partnership Interest [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	137	157
Alternative Investment, Fair Value Disclosure	137	157
Master Trust [Member] | Hedge Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	226	232
Alternative Investment, Fair Value Disclosure	226	232
Master Trust [Member] | Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	135	144
Alternative Investment, Fair Value Disclosure	135	127
Master Trust [Member] | Real Estate [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets		17
Master Trust [Member] | US Treasury and Government [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	762	734
Master Trust [Member] | US Treasury and Government [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	762	734
Master Trust [Member] | Guaranteed Investment Contracts [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	28	29
Master Trust [Member] | Guaranteed Investment Contracts [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	28	29
Master Trust [Member] | Government Bonds - Foreign [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	38	32
Master Trust [Member] | Government Bonds - Foreign [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	38	32
Master Trust [Member] | Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	6	17
Master Trust [Member] | Cash and Cash Equivalents [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	6	15
Master Trust [Member] | Cash and Cash Equivalents [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets		2
Master Trust [Member] | Asset Backed Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	2
Master Trust [Member] | Asset Backed Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	2
Master Trust [Member] | Miscellaneous Investments And Other [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	17	32
Alternative Investment, Fair Value Disclosure		25
Master Trust [Member] | Miscellaneous Investments And Other [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	15	1
Master Trust [Member] | Miscellaneous Investments And Other [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	2	6
OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	58	66
OPEB [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	58	66
OPEB [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	28	26
OPEB [Member] | Equity Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	28	26
OPEB [Member] | Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	1	1
OPEB [Member] | Real Estate [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	1	1
OPEB [Member] | Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	8	14
OPEB [Member] | Cash and Cash Equivalents [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	8	14
OPEB [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	21	25
OPEB [Member] | Debt Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets	$ 21	$ 25
Duke Energy Carolinas [Member] | Master Trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Allocated assets	27.00%	27.00%
Progress Energy [Member] | Master Trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Allocated assets	30.00%	30.00%
Duke Energy Progress [Member] | Master Trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Allocated assets	15.00%	15.00%
Duke Energy Florida [Member] | Master Trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Allocated assets	15.00%	15.00%
Duke Energy Ohio [Member] | Master Trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Allocated assets	5.00%	5.00%
Duke Energy Indiana [Member] | Master Trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Allocated assets	8.00%	8.00%
Piedmont Natural Gas [Member] | Master Trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Allocated assets	4.00%

Employee Benefit Plans (Reconci

Employee Benefit Plans (Reconciliation of Assets Measured at Fair Value on a Recurring Basis) (Details) - Level 3 [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Plan assets at prior measurement date	$ 38	$ 31
Assets received from acquisition		9
Sales	(2)	(2)
Total gains (losses) and other, net	1
Transfer of Level 3 assets to other classifications	(9)
Plan assets at measurement date	$ 28	$ 38

Employee Benefit Plans (Employe

Employee Benefit Plans (Employee Savings Plans)(Details) - USD ($)	2 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015	Oct. 31, 2015
Employee Savings Plans [Abstract]
Matching contribution percentage		100.00%
Eligible pay percentage		6.00%
Additional contribution percentage for employees not participating in defined pension plans		4.00%
Employer contributions		$ 179,000,000	$ 169,000,000		$ 159,000,000
Duke Energy Carolinas [Member]
Employee Savings Plans [Abstract]
Employer contributions		61,000,000	57,000,000		54,000,000
Progress Energy [Member]
Employee Savings Plans [Abstract]
Employer contributions		53,000,000	50,000,000		48,000,000
Duke Energy Progress [Member]
Employee Savings Plans [Abstract]
Employer contributions		37,000,000	35,000,000		34,000,000
Duke Energy Florida [Member]
Employee Savings Plans [Abstract]
Employer contributions		16,000,000	15,000,000		13,000,000
Duke Energy Ohio [Member]
Employee Savings Plans [Abstract]
Employer contributions		3,000,000	3,000,000		3,000,000
Duke Energy Indiana [Member]
Employee Savings Plans [Abstract]
Employer contributions		$ 9,000,000	8,000,000		7,000,000
Piedmont Natural Gas [Member]
Employee Savings Plans [Abstract]
Eligible pay percentage		5.00%
Additional contribution percentage for employees not participating in defined pension plans		4.00%
Employer contributions			$ 0		$ 0
Piedmont Natural Gas [Member] | Pension Plan [Member]
Employee Savings Plans [Abstract]
Eligible pay percentage		4.00%
Employer contributions	$ 0	$ 2,000,000		$ 2,000,000		$ 2,000,000
Piedmont Natural Gas [Member] | 401K [Member]
Employee Savings Plans [Abstract]
Employer contributions	$ 1,000,000	$ 7,000,000		$ 7,000,000		$ 7,000,000

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Line Items]
Tax Act	$ (112)
Impact of tax legislation on transition tax and foreign earnings	10
Income tax benefit related to remeasurement of deferred tax asset	534
Regulatory Liabilities	15,732	$ 7,290
Tax Act [Member]
Income Tax Disclosure [Line Items]
Regulatory Liabilities	8,313
Valuation Allowance, Tax Credit Carryforward [Member]
Income Tax Disclosure [Line Items]
Tax Act	$ 406

Income Taxes (Components of Inc

Income Taxes (Components of Income Tax Expense) (Details) - USD ($) $ in Millions	2 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015	Oct. 31, 2015
Current Income Tax Expense (Benefit), Continuing Operations [Abstract]
Current federal taxes		$ (247)
Current state taxes		4	$ (15)		$ (12)
Current foreign taxes		3	2		4
Total current income taxes		(240)	(13)		(8)
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]
Deferred federal taxes		1,344	1,064		1,097
Deferred state taxes		102	117		181
Total deferred income taxes		1,446	1,181		1,278
Investment tax credit amortization		(10)	(12)		(14)
Income tax expense (benefit) from continuing operations		1,196	1,156		1,256
Tax expense (benefit) from discontinued operations		(6)	(30)		89
Total income tax expense included in Consolidated Statements of Operations		1,190	1,126		1,345
Net operating loss carry forward		428	648		264
Duke Energy Income from Continuing Operations Before Income Taxes [Abstract]
Domestic		4,207	3,689		3,831
Foreign		59	45		79
Total income from continuing operations before income taxes		4,266	3,734		3,910
Equity in losses of unconsolidated affiliates		(119)	15		(69)
Tax Act [Member]
Duke Energy Income from Continuing Operations Before Income Taxes [Abstract]
Equity in losses of unconsolidated affiliates		16
Duke Energy Carolinas [Member]
Current Income Tax Expense (Benefit), Continuing Operations [Abstract]
Current federal taxes		221	139		216
Current state taxes		20	25		14
Total current income taxes		241	164		230
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]
Deferred federal taxes		381	430		345
Deferred state taxes		35	45		57
Total deferred income taxes		416	475		402
Investment tax credit amortization		(5)	(5)		(5)
Income tax expense (benefit) from continuing operations		652	634		627
Total income tax expense included in Consolidated Statements of Operations		652	634		627
Net operating loss carry forward		(10)	4		15
Duke Energy Income from Continuing Operations Before Income Taxes [Abstract]
Total income from continuing operations before income taxes		1,866	1,800		1,708
Progress Energy [Member]
Current Income Tax Expense (Benefit), Continuing Operations [Abstract]
Current federal taxes		(436)	15		(193)
Current state taxes		(5)	(19)		1
Total current income taxes		(441)	(4)		(192)
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]
Deferred federal taxes		664	486		694
Deferred state taxes		44	50		27
Total deferred income taxes		708	536		721
Investment tax credit amortization		(3)	(5)		(7)
Income tax expense (benefit) from continuing operations		264	527		522
Tax expense (benefit) from discontinued operations			1		(1)
Total income tax expense included in Consolidated Statements of Operations		264	528		521
Net operating loss carry forward		74	190		119
Duke Energy Income from Continuing Operations Before Income Taxes [Abstract]
Total income from continuing operations before income taxes		1,532	1,566		1,587
Duke Energy Progress [Member]
Current Income Tax Expense (Benefit), Continuing Operations [Abstract]
Current federal taxes		(95)	(59)		(56)
Current state taxes		2	(25)		(4)
Total current income taxes		(93)	(84)		(60)
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]
Deferred federal taxes		378	350		334
Deferred state taxes		10	40		27
Total deferred income taxes		388	390		361
Investment tax credit amortization		(3)	(5)		(7)
Income tax expense (benefit) from continuing operations		292	301		294
Total income tax expense included in Consolidated Statements of Operations		292	301		294
Net operating loss carry forward		(1)	60		21
Duke Energy Income from Continuing Operations Before Income Taxes [Abstract]
Total income from continuing operations before income taxes		1,007	900		860
Duke Energy Florida [Member]
Current Income Tax Expense (Benefit), Continuing Operations [Abstract]
Current federal taxes		(188)	76		1
Current state taxes		(11)	22		(7)
Total current income taxes		(199)	98		(6)
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]
Deferred federal taxes		194	199		290
Deferred state taxes		51	25		58
Total deferred income taxes		245	224		348
Income tax expense (benefit) from continuing operations		46	322		342
Total income tax expense included in Consolidated Statements of Operations		46	322		342
Net operating loss carry forward		36	49		84
Duke Energy Income from Continuing Operations Before Income Taxes [Abstract]
Total income from continuing operations before income taxes		758	873		941
Duke Energy Ohio [Member]
Current Income Tax Expense (Benefit), Continuing Operations [Abstract]
Current federal taxes		(37)	(7)		(18)
Current state taxes		2	(13)		(1)
Total current income taxes		(35)	(20)		(19)
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]
Deferred federal taxes		99	88		96
Deferred state taxes		(4)	11		5
Total deferred income taxes		95	99		101
Investment tax credit amortization		(1)	(1)		(1)
Income tax expense (benefit) from continuing operations		59	78		81
Tax expense (benefit) from discontinued operations			(36)		22
Total income tax expense included in Consolidated Statements of Operations		59	42		103
Net operating loss carry forward		17	26		3
Duke Energy Income from Continuing Operations Before Income Taxes [Abstract]
Total income from continuing operations before income taxes		252	270		230
Duke Energy Indiana [Member]
Current Income Tax Expense (Benefit), Continuing Operations [Abstract]
Current federal taxes		128	7		(86)
Current state taxes		21	6		(12)
Total current income taxes		149	13		(98)
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]
Deferred federal taxes		138	202		245
Deferred state taxes		14	11		17
Total deferred income taxes		152	213		262
Investment tax credit amortization			(1)		(1)
Income tax expense (benefit) from continuing operations		301	225		163
Total income tax expense included in Consolidated Statements of Operations		301	225		163
Net operating loss carry forward		42	58		45
Duke Energy Income from Continuing Operations Before Income Taxes [Abstract]
Total income from continuing operations before income taxes		655	606		$ 479
Piedmont Natural Gas [Member]
Current Income Tax Expense (Benefit), Continuing Operations [Abstract]
Current federal taxes	$ 4	(90)		$ 27		$ (1)
Current state taxes	(2)	(3)		12		1
Total current income taxes	2	(93)		39
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]
Deferred federal taxes	24	147		79		78
Deferred state taxes	6	8		6		12
Total deferred income taxes	30	155		85		90
Income tax expense (benefit) from continuing operations	32	62		124		90
Total income tax expense included in Consolidated Statements of Operations		62
Net operating loss carry forward	(17)	79		(91)		(46)
Duke Energy Income from Continuing Operations Before Income Taxes [Abstract]
Total income from continuing operations before income taxes	86	201		317		227
Equity in losses of unconsolidated affiliates	$ (2)	$ 6		$ (29)		$ (34)
Previously Remitted Earnings [Member]
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]
Tax expense (benefit) from discontinued operations			$ (95)

Income Taxes (Effective Tax Rat

Income Taxes (Effective Tax Rates) (Details) - USD ($) $ in Millions	2 Months Ended	3 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015	Oct. 31, 2015
Reconciliation of Income Tax Expense at the U.S. Federal Statutory Tax Rate to the Actual Tax Expense from Continuing Operations [Abstract]
Income tax expense, computed at the statutory rate of 35%			$ 1,493	$ 1,307		$ 1,369
State income tax, net of federal income tax effect			69	64		109
AFUDC equity income			(81)	(70)		(58)
Renewable energy production tax credits			(132)	(97)		(72)
Tax Act			(112)
Audit Adjustment				5		(22)
Tax true-up			(52)	(14)		2
Other items, net			11	(39)		(72)
Income tax expense (benefit) from continuing operations			$ 1,196	$ 1,156		$ 1,256
Effective tax rate			28.00%	31.00%		32.10%
Duke Energy Carolinas [Member]
Reconciliation of Income Tax Expense at the U.S. Federal Statutory Tax Rate to the Actual Tax Expense from Continuing Operations [Abstract]
Income tax expense, computed at the statutory rate of 35%			$ 653	$ 630		$ 598
State income tax, net of federal income tax effect			36	46		46
AFUDC equity income			(37)	(36)		(34)
Tax Act		$ 15	15
Audit Adjustment				3
Tax true-up			(24)	(14)		2
Other items, net			9	5		15
Income tax expense (benefit) from continuing operations			$ 652	$ 634		$ 627
Effective tax rate			34.90%	35.20%		36.70%
Progress Energy [Member]
Reconciliation of Income Tax Expense at the U.S. Federal Statutory Tax Rate to the Actual Tax Expense from Continuing Operations [Abstract]
Income tax expense, computed at the statutory rate of 35%			$ 536	$ 548		$ 555
State income tax, net of federal income tax effect			25	20		18
AFUDC equity income			(32)	(26)		(19)
Renewable energy production tax credits						(1)
Tax Act		(246)	(246)
Audit Adjustment						(23)
Tax true-up			(19)	(11)		(3)
Other items, net				(4)		(5)
Income tax expense (benefit) from continuing operations			$ 264	$ 527		$ 522
Effective tax rate			17.20%	33.70%		32.90%
Duke Energy Progress [Member]
Reconciliation of Income Tax Expense at the U.S. Federal Statutory Tax Rate to the Actual Tax Expense from Continuing Operations [Abstract]
Income tax expense, computed at the statutory rate of 35%			$ 353	$ 315		$ 302
State income tax, net of federal income tax effect			8	10		15
AFUDC equity income			(17)	(17)		(17)
Tax Act		(40)	(40)
Audit Adjustment						1
Tax true-up			(13)	(3)		(4)
Other items, net			1	(4)		(3)
Income tax expense (benefit) from continuing operations			$ 292	$ 301		$ 294
Effective tax rate			29.00%	33.40%		34.20%
Duke Energy Florida [Member]
Reconciliation of Income Tax Expense at the U.S. Federal Statutory Tax Rate to the Actual Tax Expense from Continuing Operations [Abstract]
Income tax expense, computed at the statutory rate of 35%			$ 265	$ 306		$ 330
State income tax, net of federal income tax effect			26	30		33
AFUDC equity income			(16)	(9)		(3)
Tax Act		(226)	(226)
Audit Adjustment						(24)
Tax true-up			(7)	(9)		2
Other items, net			4	4		4
Income tax expense (benefit) from continuing operations			$ 46	$ 322		$ 342
Effective tax rate			6.10%	36.90%		36.30%
Duke Energy Ohio [Member]
Reconciliation of Income Tax Expense at the U.S. Federal Statutory Tax Rate to the Actual Tax Expense from Continuing Operations [Abstract]
Income tax expense, computed at the statutory rate of 35%			$ 88	$ 95		$ 81
State income tax, net of federal income tax effect			(1)	(2)		2
AFUDC equity income			(4)	(2)		(1)
Tax Act		(23)	(23)
Tax true-up			(5)	(16)		(5)
Other items, net			4	3		4
Income tax expense (benefit) from continuing operations			$ 59	$ 78		$ 81
Effective tax rate			23.40%	28.90%		35.20%
Duke Energy Indiana [Member]
Reconciliation of Income Tax Expense at the U.S. Federal Statutory Tax Rate to the Actual Tax Expense from Continuing Operations [Abstract]
Income tax expense, computed at the statutory rate of 35%			$ 229	$ 212		$ 168
State income tax, net of federal income tax effect			23	11		2
AFUDC equity income			(8)	(6)		(4)
Tax Act		$ 55	55
Tax true-up			(6)	2		(9)
Other items, net			8	6		6
Income tax expense (benefit) from continuing operations			$ 301	$ 225		$ 163
Effective tax rate			46.00%	37.10%		34.00%
Piedmont Natural Gas [Member]
Reconciliation of Income Tax Expense at the U.S. Federal Statutory Tax Rate to the Actual Tax Expense from Continuing Operations [Abstract]
Income tax expense, computed at the statutory rate of 35%	$ 30		$ 70		$ 111		$ 79
State income tax, net of federal income tax effect	1		3		11		9
Tax Act			(12)
Other items, net	1		1		2		2
Income tax expense (benefit) from continuing operations	$ 32		$ 62		$ 124		$ 90
Effective tax rate	37.20%		30.80%		39.10%		39.70%

Income Taxes (Deferred Income T

Income Taxes (Deferred Income Taxes) (Details) - USD ($) $ in Millions	3 Months Ended					12 Months Ended
	Jun. 30, 2017	Sep. 30, 2016	Jul. 31, 2016	Sep. 30, 2015	Jul. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred Tax Assets, Gross [Abstract]
Deferred credits and other liabilities						$ 143	$ 382
Capital lease obligations						49	60
Pension, postretirement and other employee benefits						295	561
Progress Energy merger purchase accounting adjustments						536	918
Tax credits and NOL carryforwards						4,527	4,682
Other						73	205
Valuation allowance						(519)	(96)
Total deferred income tax assets						5,104	6,712
Deferred Tax Liabilities, Gross [Abstract]
Investments and other assets						(1,419)	(1,892)
Accelerated depreciation rates						(9,216)	(14,872)
Regulatory assets and deferred debits, net						(1,090)	(4,103)
Total deferred income tax liabilities						(11,725)	(20,867)
Net deferred income tax liabilities						(6,621)	(14,155)
Decrease In Deferred Taxes As A Result Of Tax Legislation Change						8,982
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards						4,527	4,682
Valuation allowance						(519)	(96)
Classification of Deferred Tax Assets (Liabiliities) in the Consolidated Balance Sheets [Abstract]
Net deferred income tax liabilities						$ (6,621)	$ (14,155)
State [Member] | January 2015 [Member] | North Carolina Department of Revenue [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Statutory Tax Rate								5.00%
State [Member] | January 2016 [Member] | North Carolina Department of Revenue [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Statutory Tax Rate							4.00%
Net reduction in deferred tax liability				$ 95
State [Member] | January 2017 [Member] | North Carolina Department of Revenue [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Statutory Tax Rate						3.00%
Net reduction in deferred tax liability		$ 80
State [Member] | Tax Year 2019 [Member] | North Carolina Department of Revenue [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Statutory Tax Rate						2.50%
Net reduction in deferred tax liability	$ 55
Investment Tax Credits [Member]
Deferred Tax Assets, Gross [Abstract]
Tax credits and NOL carryforwards						$ 1,406
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards						$ 1,406
Investment Tax Credits [Member] | Minimum [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Expiration year						Dec. 31, 2024
Investment Tax Credits [Member] | Maximum [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Expiration year						Dec. 31, 2037
Alternative Minimum Tax Credit [Member]
Deferred Tax Assets, Gross [Abstract]
Tax credits and NOL carryforwards						$ 1,147
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards						1,147
NOL Carryforwards [Member] | Federal [Member]
Deferred Tax Assets, Gross [Abstract]
Tax credits and NOL carryforwards						393
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards						$ 393
NOL Carryforwards [Member] | Federal [Member] | Minimum [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Expiration year						Dec. 31, 2022
NOL Carryforwards [Member] | Federal [Member] | Maximum [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Expiration year						Dec. 31, 2036
NOL Carryforwards [Member] | State [Member]
Deferred Tax Assets, Gross [Abstract]
Tax credits and NOL carryforwards						$ 296
Valuation allowance						(90)
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards						296
Valuation allowance						$ (90)
NOL Carryforwards [Member] | State [Member] | Minimum [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Expiration year						Dec. 31, 2018
NOL Carryforwards [Member] | State [Member] | Maximum [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Expiration year						Dec. 31, 2037
NOL Carryforwards [Member] | Foreign Jurisdictions [Member]
Deferred Tax Assets, Gross [Abstract]
Tax credits and NOL carryforwards						$ 13
Valuation allowance						(13)
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards						13
Valuation allowance						$ (13)
NOL Carryforwards [Member] | Foreign Jurisdictions [Member] | Minimum [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Expiration year						Dec. 31, 2027
NOL Carryforwards [Member] | Foreign Jurisdictions [Member] | Maximum [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Expiration year						Dec. 31, 2036
Foreign Tax Credit [Member]
Deferred Tax Assets, Gross [Abstract]
Tax credits and NOL carryforwards						$ 1,272
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards						1,272
Foreign Tax Credit [Member] | Federal [Member]
Deferred Tax Assets, Gross [Abstract]
Valuation allowance						(416)
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Valuation allowance						$ (416)
Foreign Tax Credit [Member] | Foreign Jurisdictions [Member] | Minimum [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Expiration year						Dec. 31, 2024
Foreign Tax Credit [Member] | Foreign Jurisdictions [Member] | Maximum [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Expiration year						Dec. 31, 2027
Duke Energy Carolinas [Member]
Deferred Tax Assets, Gross [Abstract]
Deferred credits and other liabilities						$ 33	$ 66
Capital lease obligations						14	8
Pension, postretirement and other employee benefits						(17)	16
Tax credits and NOL carryforwards						234	192
Regulatory liabilities and deferred credits						222
Other						10	16
Total deferred income tax assets						496	298
Deferred Tax Liabilities, Gross [Abstract]
Investments and other assets						(849)	(1,149)
Accelerated depreciation rates						(3,060)	(4,664)
Regulatory assets and deferred debits, net							(1,029)
Total deferred income tax liabilities						(3,909)	(6,842)
Net deferred income tax liabilities						(3,413)	(6,544)
Decrease In Deferred Taxes As A Result Of Tax Legislation Change						3,454
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards						234	192
Classification of Deferred Tax Assets (Liabiliities) in the Consolidated Balance Sheets [Abstract]
Net deferred income tax liabilities						(3,413)	(6,544)
Progress Energy [Member]
Deferred Tax Assets, Gross [Abstract]
Deferred credits and other liabilities						78	126
Pension, postretirement and other employee benefits						111	199
Tax credits and NOL carryforwards						402	1,165
Other						1	35
Valuation allowance						(14)	(12)
Total deferred income tax assets						578	1,513
Deferred Tax Liabilities, Gross [Abstract]
Investments and other assets						(470)	(597)
Accelerated depreciation rates						(2,803)	(4,490)
Regulatory assets and deferred debits, net						(807)	(1,672)
Total deferred income tax liabilities						(4,080)	(6,759)
Net deferred income tax liabilities						(3,502)	(5,246)
Decrease In Deferred Taxes As A Result Of Tax Legislation Change						3,282
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards						402	1,165
Valuation allowance						(14)	(12)
Classification of Deferred Tax Assets (Liabiliities) in the Consolidated Balance Sheets [Abstract]
Net deferred income tax liabilities						(3,502)	(5,246)
Duke Energy Progress [Member]
Deferred Tax Assets, Gross [Abstract]
Deferred credits and other liabilities						23	40
Pension, postretirement and other employee benefits						44	91
Tax credits and NOL carryforwards						156	222
Other						4	8
Total deferred income tax assets						227	361
Deferred Tax Liabilities, Gross [Abstract]
Investments and other assets						(289)	(313)
Accelerated depreciation rates						(1,583)	(2,479)
Regulatory assets and deferred debits, net						(238)	(892)
Total deferred income tax liabilities						(2,110)	(3,684)
Net deferred income tax liabilities						(1,883)	(3,323)
Decrease In Deferred Taxes As A Result Of Tax Legislation Change						1,882
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards						156	222
Classification of Deferred Tax Assets (Liabiliities) in the Consolidated Balance Sheets [Abstract]
Net deferred income tax liabilities						(1,883)	(3,323)
Duke Energy Florida [Member]
Deferred Tax Assets, Gross [Abstract]
Deferred credits and other liabilities						49	93
Pension, postretirement and other employee benefits						60	96
Tax credits and NOL carryforwards						143	232
Total deferred income tax assets						252	421
Deferred Tax Liabilities, Gross [Abstract]
Investments and other assets						(187)	(297)
Accelerated depreciation rates						(1,257)	(2,038)
Regulatory assets and deferred debits, net						(569)	(780)
Total deferred income tax liabilities						(2,013)	(3,115)
Net deferred income tax liabilities						(1,761)	(2,694)
Decrease In Deferred Taxes As A Result Of Tax Legislation Change						1,420
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards						143	232
Classification of Deferred Tax Assets (Liabiliities) in the Consolidated Balance Sheets [Abstract]
Net deferred income tax liabilities						(1,761)	(2,694)
Duke Energy Ohio [Member]
Deferred Tax Assets, Gross [Abstract]
Deferred credits and other liabilities						11	21
Pension, postretirement and other employee benefits						14	22
Tax credits and NOL carryforwards						25	49
Regulatory liabilities and deferred credits						65
Investments and other assets							3
Other							5
Total deferred income tax assets						115	100
Deferred Tax Liabilities, Gross [Abstract]
Accelerated depreciation rates						(896)	(1,404)
Regulatory assets and deferred debits, net							(139)
Total deferred income tax liabilities						(896)	(1,543)
Net deferred income tax liabilities						(781)	(1,443)
Decrease In Deferred Taxes As A Result Of Tax Legislation Change						771
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards						25	49
Classification of Deferred Tax Assets (Liabiliities) in the Consolidated Balance Sheets [Abstract]
Net deferred income tax liabilities						(781)	(1,443)
Duke Energy Indiana [Member]
Deferred Tax Assets, Gross [Abstract]
Deferred credits and other liabilities						6	4
Capital lease obligations						2	1
Pension, postretirement and other employee benefits						18	37
Tax credits and NOL carryforwards						216	278
Investments and other assets						1
Other							9
Total deferred income tax assets						243	329
Deferred Tax Liabilities, Gross [Abstract]
Investments and other assets						(14)	(21)
Accelerated depreciation rates						(966)	(1,938)
Regulatory assets and deferred debits, net						(188)	(270)
Total deferred income tax liabilities						(1,168)	(2,229)
Net deferred income tax liabilities						(925)	(1,900)
Decrease In Deferred Taxes As A Result Of Tax Legislation Change						1,053
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards						216	278
Classification of Deferred Tax Assets (Liabiliities) in the Consolidated Balance Sheets [Abstract]
Net deferred income tax liabilities						(925)	(1,900)
Piedmont Natural Gas [Member]
Deferred Tax Assets, Gross [Abstract]
Deferred credits and other liabilities						(5)	71
Pension, postretirement and other employee benefits						(4)	10
Tax credits and NOL carryforwards						70	192
Regulatory liabilities and deferred credits						61
Investments and other assets						18
Other							45
Valuation allowance							(1)
Total deferred income tax assets						140	317
Deferred Tax Liabilities, Gross [Abstract]
Investments and other assets							(21)
Accelerated depreciation rates						(697)	(1,080)
Regulatory assets and deferred debits, net							(147)
Other						(7)
Total deferred income tax liabilities						(704)	(1,248)
Net deferred income tax liabilities						(564)	(931)
Decrease In Deferred Taxes As A Result Of Tax Legislation Change						521
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards						70	192
Valuation allowance							(1)
Classification of Deferred Tax Assets (Liabiliities) in the Consolidated Balance Sheets [Abstract]
Net deferred income tax liabilities						$ (564)	$ (931)
Piedmont Natural Gas [Member] | State [Member] | January 2016 [Member] | North Carolina Department of Revenue [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Net reduction in deferred tax liability					$ 18
Piedmont Natural Gas [Member] | State [Member] | January 2017 [Member] | North Carolina Department of Revenue [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Net reduction in deferred tax liability			$ 16

Income Taxes (Other Disclosures

Income Taxes (Other Disclosures) (Details) - USD ($) $ in Millions	2 Months Ended	12 Months Ended
	Feb. 21, 2018	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefits - January 1	$ 25	$ 17	$ 88		$ 213
Gross increases-tax positions in prior periods		12
Gross decreases-tax positions in prior periods		(4)	(4)		(48)
Decreases due to settlements			(68)		(45)
Reduction due to lapse of statute of limitations			1		(32)
Total changes		8	(71)		(125)
Unrecognized Tax Benefits - December 31		25	17		88
Amount that if recognized, would affect the effective tax rate or regulatory liability		15
Amount that if recognized, would be recorded as a component of discontinued operations		7
Income Tax Examination, Penalties and Interest Expense [Abstract]
Net interest income recognized related to income taxes					12
Income Tax Examination, Penalties and Interest Accrued [Abstract]
Interest receivable related to income taxes					3
Interest payable related to income taxes		5	4
Duke Energy Carolinas [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefits - January 1	5	1	72		160
Gross increases-tax positions in prior periods		4
Gross decreases-tax positions in prior periods			(4)		(45)
Decreases due to settlements			(67)		(43)
Total changes		4	(71)		(88)
Unrecognized Tax Benefits - December 31		5	1		72
Amount that if recognized, would affect the effective tax rate or regulatory liability		4
Income Tax Examination, Penalties and Interest Expense [Abstract]
Net interest expense recognized related to income taxes		2	7		1
Income Tax Examination, Penalties and Interest Accrued [Abstract]
Interest payable related to income taxes		25	23		14
Progress Energy [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefits - January 1	5	2	1		32
Gross increases-tax positions in prior periods		3			1
Gross decreases-tax positions in prior periods			(1)
Reduction due to lapse of statute of limitations			2		(32)
Total changes		3	1		(31)
Unrecognized Tax Benefits - December 31		5	2		1
Amount that if recognized, would affect the effective tax rate or regulatory liability		7
Income Tax Examination, Penalties and Interest Expense [Abstract]
Net interest income recognized related to income taxes		1	1		2
Income Tax Examination, Penalties and Interest Accrued [Abstract]
Interest payable related to income taxes		1	1
Duke Energy Progress [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefits - January 1	5	2	3		23
Gross increases-tax positions in prior periods		3			1
Gross decreases-tax positions in prior periods			(1)
Reduction due to lapse of statute of limitations					(21)
Total changes		3	(1)		(20)
Unrecognized Tax Benefits - December 31		5	2		3
Amount that if recognized, would affect the effective tax rate or regulatory liability		5
Income Tax Examination, Penalties and Interest Expense [Abstract]
Net interest income recognized related to income taxes					2
Income Tax Examination, Penalties and Interest Accrued [Abstract]
Interest payable related to income taxes		1	1		1
Duke Energy Florida [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefits - January 1	5	4			8
Gross increases-tax positions in prior periods		1	4
Reduction due to lapse of statute of limitations					(8)
Total changes		1	4		(8)
Unrecognized Tax Benefits - December 31		5	4
Amount that if recognized, would affect the effective tax rate or regulatory liability		1
Income Tax Examination, Penalties and Interest Expense [Abstract]
Net interest income recognized related to income taxes		1	2		1
Duke Energy Ohio [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefits - January 1	1	4
Gross increases-tax positions in prior periods		1	4
Gross decreases-tax positions in prior periods		(4)
Total changes		(3)	4
Unrecognized Tax Benefits - December 31		1	4
Amount that if recognized, would affect the effective tax rate or regulatory liability		1
Amount that if recognized, would be recorded as a component of discontinued operations		2
Duke Energy Indiana [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefits - January 1	1		1		1
Gross increases-tax positions in prior periods		1
Decreases due to settlements			(1)
Total changes		1	$ (1)
Unrecognized Tax Benefits - December 31		1			1
Amount that if recognized, would affect the effective tax rate or regulatory liability		1
Income Tax Examination, Penalties and Interest Expense [Abstract]
Net interest income recognized related to income taxes					1
Income Tax Examination, Penalties and Interest Accrued [Abstract]
Interest receivable related to income taxes					$ 3
Piedmont Natural Gas [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefits - January 1	3
Gross increases-tax positions in prior periods		3
Total changes		3
Unrecognized Tax Benefits - December 31		3
Amount that if recognized, would affect the effective tax rate or regulatory liability		$ 3
Income Tax Examination, Penalties and Interest Expense [Abstract]
Net interest income recognized related to income taxes				$ 1
Subsequent Event [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Total changes	(8)
Subsequent Event [Member] | Duke Energy Carolinas [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Total changes	$ (1)

Other Income and Expenses, N164

Other Income and Expenses, Net (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Component Of Other Income Expense Nonoperating [Line Items]
Interest income	$ 13	$ 21	$ 20
AFUDC equity	237	200	164
Post in-service equity returns	40	67	73
Nonoperating income (expense), other	62	36	33
Other income and expenses, net	352	324	290
Duke Energy Carolinas [Member]
Component Of Other Income Expense Nonoperating [Line Items]
Interest income	2	4	2
AFUDC equity	106	102	96
Post in-service equity returns	28	55	60
Nonoperating income (expense), other	3	1	2
Other income and expenses, net	139	162	160
Progress Energy [Member]
Component Of Other Income Expense Nonoperating [Line Items]
Interest income	6	4	4
AFUDC equity	92	76	54
Post in-service equity returns	12	12	13
Nonoperating income (expense), other	18	22	26
Other income and expenses, net	128	114	97
Duke Energy Progress [Member]
Component Of Other Income Expense Nonoperating [Line Items]
Interest income	2	3	2
AFUDC equity	47	50	47
Post in-service equity returns	12	12	13
Nonoperating income (expense), other	4	6	9
Other income and expenses, net	65	71	71
Duke Energy Florida [Member]
Component Of Other Income Expense Nonoperating [Line Items]
Interest income	5	2	2
AFUDC equity	45	26	7
Nonoperating income (expense), other	11	16	15
Other income and expenses, net	61	44	24
Duke Energy Ohio [Member]
Component Of Other Income Expense Nonoperating [Line Items]
Interest income	6	5	4
AFUDC equity	11	6	3
Nonoperating income (expense), other		(2)	(1)
Other income and expenses, net	17	9	6
Duke Energy Indiana [Member]
Component Of Other Income Expense Nonoperating [Line Items]
Interest income	8	6	6
AFUDC equity	28	16	11
Nonoperating income (expense), other	1		(6)
Other income and expenses, net	$ 37	$ 22	$ 11

Quarterly Financial Data (Un165

Quarterly Financial Data (Unaudited) (Schedule of Quarterly Financial Information) (Details) - USD ($) $ / shares in Units, $ in Millions	2 Months Ended	3 Months Ended												12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Sep. 30, 2016	Jul. 31, 2016	Jun. 30, 2016	Apr. 30, 2016	Mar. 31, 2016	Jan. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015	Oct. 31, 2015
Quarterly Financial Information Disclosure [Line Items]
Operating revenues		$ 5,799	$ 6,482	$ 5,555	$ 5,729	$ 5,577		$ 6,576		$ 5,213		$ 5,377		$ 23,565	$ 22,743		$ 22,371
Operating income (loss)		1,262	1,695	1,387	1,437	888		1,954		1,259		1,240		5,781	5,341		5,078
Income (loss) from continuing operations		705	957	691	717	376		1,001		624		577		3,070	2,578		2,654
Income (Loss) From Discontinued Operations, net of tax		(2)	(2)	(2)		(598)		180		(112)		122		(6)	(408)		177
Net income (loss)		703	955	689	717	(222)		1,181		512		699		3,064	2,170		2,831
Net Income (Loss) Attributable to Parent		$ 703	$ 954	$ 686	$ 716	$ (227)		$ 1,176		$ 509		$ 694		$ 3,059	$ 2,152		$ 2,816
Income (loss) from continuing operations attributable to Duke Energy Corporation common shareholders [Abstract]
Basic		$ 1	$ 1.36	$ 0.98	$ 1.02	$ 0.53		$ 1.44		$ 0.90		$ 0.83		$ 4.37	$ 3.71		$ 3.80
Diluted		1	1.36	0.98	1.02	0.53		1.44		0.90		0.83		4.37	3.71		3.80
Income (loss) from discontinued operations attributable to Duke Energy Corporation common shareholders [Abstract]
Basic						(0.86)		0.26		(0.16)		0.18		(0.01)	(0.60)		0.25
Diluted						(0.86)		0.26		(0.16)		0.18		(0.01)	(0.60)		0.25
Net income attributable to Duke Energy Corporation common shareholders [Abstract]
Basic		1	1.36	0.98	1.02	(0.33)		1.70		0.74		1.01		4.36	3.11		4.05
Diluted		$ 1	$ 1.36	$ 0.98	$ 1.02	$ (0.33)		$ 1.70		$ 0.74		$ 1.01		$ 4.36	$ 3.11		$ 4.05
Duke Energy Carolinas [Member]
Quarterly Financial Information Disclosure [Line Items]
Operating revenues		$ 1,721	$ 2,136	$ 1,729	$ 1,716	$ 1,681		$ 2,226		$ 1,675		$ 1,740		$ 7,302	$ 7,322		$ 7,229
Operating income (loss)		403	777	485	484	302		815		464		481		2,149	2,062		1,960
Net Income (Loss) Attributable to Parent		205	466	273	270	140		494		261		271		1,214	1,166		1,081
Progress Energy [Member]
Quarterly Financial Information Disclosure [Line Items]
Operating revenues		2,348	2,864	2,392	2,179	2,208		2,965		2,348		2,332		9,783	9,853		10,277
Operating income (loss)		493	657	591	487	292		814		560		475		2,228	2,141		2,160
Income (loss) from continuing operations						104		449		274		212		1,268	1,039		1,065
Income (Loss) From Discontinued Operations, net of tax															2		(3)
Net income (loss)		447	343	277	201	106		449		274		212		1,268	1,041		1,062
Net Income (Loss) Attributable to Parent		444	341	274	199	104		446		272		209		1,258	1,031		1,051
Duke Energy Progress [Member]
Quarterly Financial Information Disclosure [Line Items]
Operating revenues		1,251	1,460	1,199	1,219	1,174		1,583		1,213		1,307		5,129	5,277		5,290
Operating income (loss)		256	411	282	286	135		438		255		258		1,235	1,086		1,024
Net Income (Loss) Attributable to Parent		168	246	154	147	60		271		131		137		715	599		566
Duke Energy Florida [Member]
Quarterly Financial Information Disclosure [Line Items]
Operating revenues		1,095	1,401	1,191	959	1,030		1,381		1,133		1,024		4,646	4,568		4,977
Operating income (loss)		234	240	306	196	155		373		300		213		976	1,041		1,115
Net Income (Loss) Attributable to Parent		344	120	158	90	64		206		171		110		712	551		599
Duke Energy Ohio [Member]
Quarterly Financial Information Disclosure [Line Items]
Operating revenues		497	471	437	518	511		489		428		516		1,923	1,944		1,905
Operating income (loss)		76	102	65	83	90		106		55		96		326	347		303
Income (loss) from continuing operations														193	192		149
Income (Loss) From Discontinued Operations, net of tax			(1)					34				2		(1)	36		23
Net Income (Loss) Attributable to Parent		65	55	30	42	57		89		23		59		192	228		172
Duke Energy Indiana [Member]
Quarterly Financial Information Disclosure [Line Items]
Operating revenues		745	802	742	758	733		809		702		714		3,047	2,958		2,890
Operating income (loss)		170	230	210	186	176		239		174		176		796	765		644
Net Income (Loss) Attributable to Parent		36	121	106	91	$ 72		$ 129		$ 85		$ 95		354	$ 381		$ 316
Piedmont Natural Gas [Member]
Quarterly Financial Information Disclosure [Line Items]
Operating revenues	$ 322	444	183	201	500		$ 172		$ 160		$ 353		$ 464	1,328		$ 1,149		$ 1,383
Operating income (loss)	96	115	(4)	5	170		(50)				104		171	286		225		263
Net Income (Loss) Attributable to Parent	$ 54	$ 63	$ (11)	$ (8)	$ 95		$ 39		$ (7)		$ 63		$ 98	$ 139		$ 193		$ 137

Quarterly Financial Data (Un166

Quarterly Financial Data (Unaudited) (Unusual or Infrequently Occurring Items) (Details) - USD ($) $ in Millions	2 Months Ended	3 Months Ended												12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Sep. 30, 2016	Jul. 31, 2016	Jun. 30, 2016	Apr. 30, 2016	Mar. 31, 2016	Jan. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015	Oct. 31, 2015
Quarterly Financial Information Disclosure [Line Items]
Costs to achieve mergers, integration costs		$ (34)	$ (23)	$ (30)	$ (16)									$ (103)
Costs to achieve mergers, acquisition costs						$ (208)		$ (84)		$ (111)		$ (120)			$ (523)
Asset Impairment Charges														(282)	(18)		$ (106)
Net Income (Loss) Attributable to Parent		703	954	686	716	(227)		1,176		509		694		3,059	2,152		2,816
(Loss) Income from Discontinued Operations, net of tax		(2)	(2)	(2)		(598)		180		(112)		122		(6)	(408)		177
Cost Savings Initiative						(29)		(19)		(24)		(20)			(92)
Tax Act														(112)
Total		27	(242)	(30)	(16)	(751)		(174)		(329)		(140)		(261)	(1,394)
Regulatory settlements [Member]
Quarterly Financial Information Disclosure [Line Items]
Asset Impairment Charges			(135)
Utilities Operating Expense, Impairments		(23)												(158)
Commercial Renewables Impairment [Member]
Quarterly Financial Information Disclosure [Line Items]
Asset Impairment Charges		(18)	(84)					(71)						(102)	(71)
Impacts of the Tax Act [Member]
Quarterly Financial Information Disclosure [Line Items]
Net Income (Loss) Attributable to Parent		102												102
Loss on Disposal Group [Member]
Quarterly Financial Information Disclosure [Line Items]
Discontinued Operation, Provision for Loss (Gain) on Disposal, before Income Tax						514									514
Central America Impairment [Member]
Quarterly Financial Information Disclosure [Line Items]
Asset Impairment Charges										(194)					(194)
Duke Energy Carolinas [Member]
Quarterly Financial Information Disclosure [Line Items]
Costs to achieve mergers, integration costs		(5)	(5)	(6)	(4)									(20)
Costs to achieve mergers, acquisition costs						(68)		(13)		(12)		(11)			(104)
Asset Impairment Charges															(1)		(1)
Net Income (Loss) Attributable to Parent		205	466	273	270	140		494		261		271		1,214	1,166		1,081
Cost Savings Initiative						(11)		(8)		(10)		(10)			(39)
Tax Act		15												15
Total		(20)	(5)	(6)	(4)	(79)		(21)		(22)		(21)		(35)	(143)
Progress Energy [Member]
Quarterly Financial Information Disclosure [Line Items]
Costs to achieve mergers, integration costs		(6)	(6)	(7)	(4)									(23)
Costs to achieve mergers, acquisition costs						(44)		(10)		(8)		(7)			(69)
Asset Impairment Charges														(156)	(7)		(12)
Net Income (Loss) Attributable to Parent		444	341	274	199	104		446		272		209		1,258	1,031		1,051
(Loss) Income from Discontinued Operations, net of tax															2		(3)
Cost Savings Initiative						(14)		(10)		(8)		(8)			(40)
Tax Act		(246)												(246)
Total		217	(141)	(7)	(4)	(58)		(20)		(16)		(15)		65	(109)
Progress Energy [Member] | Regulatory settlements [Member]
Quarterly Financial Information Disclosure [Line Items]
Asset Impairment Charges			(135)
Utilities Operating Expense, Impairments		(23)												(158)
Duke Energy Progress [Member]
Quarterly Financial Information Disclosure [Line Items]
Costs to achieve mergers, integration costs		(4)	(4)	(4)	(2)									(14)
Costs to achieve mergers, acquisition costs						(40)		(6)		(5)		(5)			(56)
Asset Impairment Charges														(19)	(1)		(5)
Net Income (Loss) Attributable to Parent		168	246	154	147	60		271		131		137		715	599		566
Cost Savings Initiative						(6)		(7)		(5)		(5)			(23)
Tax Act		(40)												(40)
Total		13	(4)	(4)	(2)	(46)		(13)		(10)		(10)		3	(79)
Duke Energy Progress [Member] | Regulatory settlements [Member]
Quarterly Financial Information Disclosure [Line Items]
Utilities Operating Expense, Impairments		(23)												(23)
Duke Energy Florida [Member]
Quarterly Financial Information Disclosure [Line Items]
Costs to achieve mergers, integration costs		(2)	(2)	(3)	(2)									(9)
Costs to achieve mergers, acquisition costs						(4)		(4)		(3)		(2)			(13)
Asset Impairment Charges														(138)	(6)		(7)
Net Income (Loss) Attributable to Parent		344	120	158	90	64		206		171		110		712	551		599
Cost Savings Initiative						(9)		(3)		(3)		(2)			(17)
Tax Act		(226)												(226)
Total		224	(137)	(3)	(2)	(13)		(7)		(6)		(4)		82	(30)
Duke Energy Florida [Member] | Regulatory settlements [Member]
Quarterly Financial Information Disclosure [Line Items]
Asset Impairment Charges			(135)											(135)
Duke Energy Ohio [Member]
Quarterly Financial Information Disclosure [Line Items]
Costs to achieve mergers, integration costs		(2)	(2)	(1)	(1)									(6)
Costs to achieve mergers, acquisition costs						(2)		(2)		(1)		(1)			(6)
Asset Impairment Charges														(1)
Net Income (Loss) Attributable to Parent		65	55	30	42	57		89		23		59		192	228		172
(Loss) Income from Discontinued Operations, net of tax			(1)					34				2		(1)	36		23
Cost Savings Initiative						(1)				(1)		(1)			(3)
Tax Act		(23)												(23)
Total		21	(2)	(1)	(1)	(3)		(2)		(2)		(2)		17	(9)
Duke Energy Indiana [Member]
Quarterly Financial Information Disclosure [Line Items]
Costs to achieve mergers, integration costs		(1)	(2)	(2)	(1)									(6)
Costs to achieve mergers, acquisition costs						(3)		(3)		(2)		(1)			(9)
Asset Impairment Charges														(18)	(8)		(88)
Net Income (Loss) Attributable to Parent		36	121	106	91	72		129		85		95		354	381		$ 316
Cost Savings Initiative						(1)		(1)		(4)		(1)			(7)
Tax Act		55												55
Total		(56)	(2)	(2)	(1)	$ (4)		$ (4)		$ (6)		$ (2)		(61)	$ (16)
Piedmont Natural Gas [Member]
Quarterly Financial Information Disclosure [Line Items]
Costs to achieve mergers, integration costs		(19)	(8)	(13)	(6)									(46)
Costs to achieve mergers, acquisition costs	$ (7)						$ (53)		$ (1)		$ (2)		$ (6)			$ (62)
Asset Impairment Charges														(7)
Net Income (Loss) Attributable to Parent	$ 54	63	(11)	(8)	95		$ 39		$ (7)		$ 63		$ 98	139		$ 193		$ 137
Tax Act														(12)
Total		(17)	$ (8)	$ (13)	$ (6)									(44)
Piedmont Natural Gas [Member] | Impacts of the Tax Act [Member]
Quarterly Financial Information Disclosure [Line Items]
Net Income (Loss) Attributable to Parent		$ 2												$ 2