Progress Energy (PREX) 10-Q 2 Nov 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Oct. 31, 2018
Document Information [Line Items]
Entity Registrant Name	Duke Energy Corporation
Entity Central Index Key	1,326,160
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Common Stock, Shares Outstanding		712,877,558
Trading Symbol	DUK
Entity Emerging Growth Company	false
Entity Small Business	false
Duke Energy Carolinas [Member]
Document Information [Line Items]
Entity Registrant Name	Duke Energy Carolinas, LLC
Entity Central Index Key	30,371
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Progress Energy [Member]
Document Information [Line Items]
Entity Registrant Name	Progress Energy, Inc
Entity Central Index Key	1,094,093
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Duke Energy Progress [Member]
Document Information [Line Items]
Entity Registrant Name	Duke Energy Progress, LLC
Entity Central Index Key	17,797
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Duke Energy Florida [Member]
Document Information [Line Items]
Entity Registrant Name	Duke Energy Florida, LLC
Entity Central Index Key	37,637
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Duke Energy Ohio [Member]
Document Information [Line Items]
Entity Registrant Name	Duke Energy Ohio, Inc.
Entity Central Index Key	20,290
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Duke Energy Indiana [Member]
Document Information [Line Items]
Entity Registrant Name	Duke Energy Indiana, LLC
Entity Central Index Key	81,020
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Piedmont Natural Gas [Member]
Document Information [Line Items]
Entity Registrant Name	Piedmont Natural Gas Company, Inc.
Entity Central Index Key	78,460
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Operating Revenues
Regulated electric	$ 6,216	$ 6,091	$ 16,678	$ 16,122
Regulated natural gas	230	247	1,221	1,168
Nonregulated electric and other	182	144	507	476
Total operating revenues	6,628	6,482	18,406	17,766
Operating Expenses
Operation, maintenance and other	1,584	1,476	4,592	4,385
Depreciation and amortization	1,039	900	2,979	2,594
Property and other taxes	323	313	954	924
Impairment charges	124	207	339	216
Total operating expenses	5,059	4,827	14,505	13,374
Gains (Losses) on Sales of Other Assets and Other, net	10	6	(87)	24
Operating Income	1,579	1,661	3,814	4,416
Other Income and Expenses
Equity in earnings of unconsolidated affiliates	37	36	49	101
Other income and expenses, net	131	122	327	358
Total other income and expenses	168	158	376	459
Interest Expense	517	498	1,550	1,475
Income From Continuing Operations Before Income Taxes	1,230	1,321	2,640	3,400
Income Tax Expense From Continuing Operations	168	364	449	1,035
Income From Continuing Operations	1,062	957	2,191	2,365
Income (Loss) From Discontinued Operations, net of tax	4	(2)	(1)	(4)
Net Income	1,066	955	2,190	2,361
Less: Net (Loss) Income Attributable to Noncontrolling Interests	(16)	1	(12)	5
Net Income Attributable to Duke Energy Corporation	1,082	954	2,202	2,356
Other Comprehensive Income (Loss), net of tax
Pension and OPEB adjustments	1		3	2
Net unrealized (losses) gains on cash flow hedges	(3)	2	10	(2)
Reclassification into earnings from cash flow hedges	6	(2)	5	3
Unrealized (losses) gains on available-for-sale securities		2	(5)	10
Other Comprehensive Income, net of tax	4	2	13	13
Comprehensive Income	1,070	957	2,203	2,374
Less: Comprehensive (Loss) Income Attributable to Noncontrolling Interests	(16)	1	(12)	5
Comprehensive Income Attributable to Duke Energy Corporation	$ 1,086	$ 956	$ 2,215	$ 2,369
Income from continuing operations attributable to Duke Energy Corporation common stockholders
Basic (usd per share)	$ 1.51	$ 1.36	$ 3.12	$ 3.37
Diluted (usd per share)	1.51	1.36	3.11	3.37
Loss from discontinued operations attributable to Duke Energy Corporation common stockholders
Basic (usd per share)				(0.01)
Diluted (usd per share)				(0.01)
Net income attributable to Duke Energy Corporation common stockholders
Basic (usd per share)	1.51	1.36	3.12	3.36
Diluted (usd per share)	$ 1.51	$ 1.36	$ 3.11	$ 3.36
Weighted average shares outstanding
Basic (shares)	713	700	705	700
Diluted (shares)	714	700	706	700
Duke Energy Carolinas [Member]
Operating Revenues
Total operating revenues	$ 2,090	$ 2,136	$ 5,525	$ 5,581
Operating Expenses
Fuel used in electric generation and purchased power/Cost of natural gas	490	531	1,370	1,394
Operation, maintenance and other	514	494	1,464	1,472
Depreciation and amortization	305	281	866	804
Property and other taxes	67	67	214	206
Impairment charges	1		191
Total operating expenses	1,377	1,373	4,105	3,876
Gains (Losses) on Sales of Other Assets and Other, net			(1)
Operating Income	713	763	1,419	1,705
Other Income and Expenses
Total other income and expenses	34	40	108	140
Interest Expense	106	108	323	314
Income From Continuing Operations Before Income Taxes	641	695	1,204	1,531
Income Tax Expense From Continuing Operations	145	229	268	522
Net Income Attributable to Duke Energy Corporation	496	466	936	1,009
Other Comprehensive Income (Loss), net of tax
Reclassification into earnings from cash flow hedges			1	1
Other Comprehensive Income, net of tax			1	1
Comprehensive Income Attributable to Duke Energy Corporation	496	466	937	1,010
Progress Energy [Member]
Operating Revenues
Total operating revenues	3,045	2,864	8,119	7,435
Operating Expenses
Fuel used in electric generation and purchased power/Cost of natural gas	1,148	1,031	3,019	2,588
Operation, maintenance and other	680	588	1,913	1,697
Depreciation and amortization	419	334	1,183	958
Property and other taxes	145	140	399	386
Impairment charges	1	135	34	137
Total operating expenses	2,393	2,228	6,548	5,766
Gains (Losses) on Sales of Other Assets and Other, net	11	5	23	19
Operating Income	663	641	1,594	1,688
Other Income and Expenses
Total other income and expenses	51	36	128	112
Interest Expense	214	193	626	595
Income From Continuing Operations Before Income Taxes	500	484	1,096	1,205
Income Tax Expense From Continuing Operations	94	141	186	384
Net Income	406	343	910	821
Less: Net (Loss) Income Attributable to Noncontrolling Interests	2	2	6	7
Net Income Attributable to Duke Energy Corporation	404	341	904	814
Other Comprehensive Income (Loss), net of tax
Pension and OPEB adjustments		3	2	5
Net unrealized (losses) gains on cash flow hedges	2	(2)	5	4
Unrealized (losses) gains on available-for-sale securities		1	(1)	3
Other Comprehensive Income, net of tax	2	2	6	12
Comprehensive Income	408	345	916	833
Less: Comprehensive (Loss) Income Attributable to Noncontrolling Interests	2	2	6	7
Comprehensive Income Attributable to Duke Energy Corporation	406	343	910	826
Duke Energy Progress [Member]
Operating Revenues
Total operating revenues	1,582	1,460	4,333	3,878
Operating Expenses
Fuel used in electric generation and purchased power/Cost of natural gas	535	475	1,452	1,214
Operation, maintenance and other	431	365	1,187	1,069
Depreciation and amortization	253	182	723	536
Property and other taxes	40	40	115	120
Impairment charges			33
Total operating expenses	1,259	1,062	3,510	2,939
Gains (Losses) on Sales of Other Assets and Other, net	7		9	3
Operating Income	330	398	832	942
Other Income and Expenses
Total other income and expenses	24	27	61	84
Interest Expense	82	65	241	217
Income From Continuing Operations Before Income Taxes	272	360	652	809
Income Tax Expense From Continuing Operations	56	114	120	262
Net Income Attributable to Duke Energy Corporation	216	246	532	547
Other Comprehensive Income (Loss), net of tax
Comprehensive Income Attributable to Duke Energy Corporation	216	246	532	547
Duke Energy Florida [Member]
Operating Revenues
Total operating revenues	1,462	1,401	3,780	3,551
Operating Expenses
Fuel used in electric generation and purchased power/Cost of natural gas	614	557	1,567	1,374
Operation, maintenance and other	245	220	719	623
Depreciation and amortization	166	154	460	423
Property and other taxes	105	99	284	265
Impairment charges	1	135	1	137
Total operating expenses	1,131	1,165	3,031	2,822
Operating Income	331	236	749	729
Other Income and Expenses
Total other income and expenses	28	19	75	58
Interest Expense	73	71	210	211
Income From Continuing Operations Before Income Taxes	286	184	614	576
Income Tax Expense From Continuing Operations	43	64	100	208
Net Income Attributable to Duke Energy Corporation	243	120	514	368
Other Comprehensive Income (Loss), net of tax
Unrealized (losses) gains on available-for-sale securities		1	(1)	3
Other Comprehensive Income, net of tax			(1)	3
Comprehensive Income Attributable to Duke Energy Corporation	243	121	513	371
Duke Energy Ohio [Member]
Operating Revenues
Regulated electric	373	371	1,055	1,036
Regulated natural gas	84	90	361	360
Nonregulated electric and other	12	10	36	30
Total operating revenues	469	471	1,452	1,426
Operating Expenses
Operation, maintenance and other	76	125	337	388
Depreciation and amortization	64	63	196	193
Property and other taxes	73	65	218	204
Impairment charges				1
Total operating expenses	330	371	1,151	1,180
Gains (Losses) on Sales of Other Assets and Other, net		1	(106)	1
Operating Income	139	101	195	247
Other Income and Expenses
Total other income and expenses	3	5	17	15
Interest Expense	23	22	68	67
Income From Continuing Operations Before Income Taxes	119	84	144	195
Income Tax Expense From Continuing Operations	19	28	23	67
Income From Continuing Operations	100	56	121	128
Income (Loss) From Discontinued Operations, net of tax		(1)		(1)
Net Income				127
Net Income Attributable to Duke Energy Corporation	100	55	121	127
Other Comprehensive Income (Loss), net of tax
Comprehensive Income Attributable to Duke Energy Corporation	100	55	121	127
Duke Energy Indiana [Member]
Operating Revenues
Total operating revenues	819	802	2,288	2,302
Operating Expenses
Fuel used in electric generation and purchased power/Cost of natural gas	272	259	730	744
Operation, maintenance and other	198	177	576	546
Depreciation and amortization	130	120	386	336
Property and other taxes	16	19	56	56
Impairment charges	30		30
Total operating expenses	646	575	1,778	1,682
Gains (Losses) on Sales of Other Assets and Other, net		1		1
Operating Income	173	228	510	621
Other Income and Expenses
Total other income and expenses	23	12	36	32
Interest Expense	42	44	125	132
Income From Continuing Operations Before Income Taxes	154	196	421	521
Income Tax Expense From Continuing Operations	35	75	104	203
Net Income Attributable to Duke Energy Corporation	119	121	317	318
Other Comprehensive Income (Loss), net of tax
Comprehensive Income Attributable to Duke Energy Corporation	119	121	317	318
Piedmont Natural Gas [Member]
Operating Revenues
Total operating revenues	172	183	940	884
Operating Expenses
Fuel used in electric generation and purchased power/Cost of natural gas	54	63	387	333
Operation, maintenance and other	85	73	252	226
Depreciation and amortization	40	38	118	109
Property and other taxes	12	13	36	38
Impairment charges				7
Total operating expenses	191	187	793	713
Operating Income	(19)	(4)	147	171
Other Income and Expenses
Equity in earnings of unconsolidated affiliates	3	3	6	8
Other income and expenses, net	3	0	9	(1)
Total other income and expenses	6	3	15	7
Interest Expense	19	20	60	59
Income From Continuing Operations Before Income Taxes	(32)	(21)	102	119
Income Tax Expense From Continuing Operations	(11)	(10)	21	43
Net Income Attributable to Duke Energy Corporation	(21)	(11)	81	76
Other Comprehensive Income (Loss), net of tax
Comprehensive Income Attributable to Duke Energy Corporation	(21)	(11)	81	76
Electricity, US Regulated [Member] | Duke Energy Ohio [Member]
Operating Expenses
Fuel used in electric generation and purchased power/Cost of natural gas	99	100	284	283
Electricity, Nonregulated [Member] | Duke Energy Ohio [Member]
Operating Expenses
Fuel used in electric generation and purchased power/Cost of natural gas	14	13	43	42
Electricity [Member]
Operating Expenses
Fuel used in electric generation and purchased power/Cost of natural gas	1,931	1,863	5,181	4,853
Natural Gas [Member]
Operating Expenses
Fuel used in electric generation and purchased power/Cost of natural gas	58	68	460	402
Natural Gas [Member] | Duke Energy Ohio [Member]
Operating Expenses
Fuel used in electric generation and purchased power/Cost of natural gas	$ 4	$ 5	$ 73	$ 69

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest [Abstract]
Net Income	$ 1,066	$ 955	$ 2,190	$ 2,361
Other Comprehensive Income, net of tax
Pension and OPEB adjustments	1		3	2
Net unrealized (losses) gains on cash flow hedges	(3)	2	10	(2)
Reclassification into earnings from cash flow hedges	6	(2)	5	3
Unrealized (losses) gains on available-for-sale securities		2	(5)	10
Other Comprehensive Income, net of tax	4	2	13	13
Comprehensive Income	1,070	957	2,203	2,374
Less: Comprehensive (Loss) Income Attributable to Noncontrolling Interests	(16)	1	(12)	5
Comprehensive Income Attributable to Duke Energy Corporation	$ 1,086	$ 956	$ 2,215	$ 2,369

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Current Assets
Cash and cash equivalents	$ 303	$ 358
Receivables (net of allowance for doubtful accounts)	682	779
Receivables of VIEs (net of allowance for doubtful accounts)	2,397	1,995
Inventory	3,140	3,250
Regulatory assets (includes amounts related to VIEs)	1,906	1,437
Other	1,092	634
Total current assets	9,520	8,453
Property, Plant and Equipment
Cost	132,677	127,507
Accumulated depreciation and amortization	(43,200)	(41,537)
Generation facilities to be retired, net	388	421
Net property, plant and equipment	89,865	86,391
Other Noncurrent Assets
Goodwill	19,303	19,396
Regulatory assets	12,616	12,442
Nuclear decommissioning trust funds	7,421	7,097
Investments in equity method unconsolidated affiliates	1,328	1,175
Other	3,112	2,960
Total other noncurrent assets	43,780	43,070
Total Assets	143,165	137,914
Current Liabilities
Accounts payable	3,234	3,043
Notes payable and commercial paper	2,891	2,163
Taxes accrued	674	551
Interest accrued	557	525
Current maturities of long-term debt (includes amounts related to VIEs)	3,455	3,244
Asset retirement obligations	902	689
Regulatory liabilities	506	402
Other	1,703	1,865
Total current liabilities	13,922	12,482
Long-Term Debt (includes amounts related to VIEs)	50,507	49,035
Other Noncurrent Liabilities
Deferred income taxes	7,765	6,621
Asset retirement obligations	9,354	9,486
Regulatory liabilities	15,587	15,330
Accrued pension and other post-retirement benefit costs	1,001	1,103
Investment tax credits	539	539
Other	1,477	1,581
Total other noncurrent liabilities	35,723	34,660
Commitments and Contingencies
Equity
Common stock	1	1
Additional paid-in capital	39,747	38,792
Retained earnings	3,313	3,013
Accumulated other comprehensive loss	(66)	(67)
Total Duke Energy Corporation stockholders' equity	42,995	41,739
Noncontrolling interests	18	(2)
Total equity	43,013	41,737
Total Liabilities and Equity	143,165	137,914
Duke Energy Carolinas [Member]
Current Assets
Cash and cash equivalents	27	16
Receivables (net of allowance for doubtful accounts)	203	200
Receivables of VIEs (net of allowance for doubtful accounts)	795	640
Receivables from affiliated companies	158	95
Inventory	976	971
Regulatory assets (includes amounts related to VIEs)	435	299
Other	55	19
Total current assets	2,649	2,240
Property, Plant and Equipment
Cost	44,086	42,939
Accumulated depreciation and amortization	(15,536)	(15,063)
Net property, plant and equipment	28,550	27,876
Other Noncurrent Assets
Regulatory assets	3,188	2,853
Nuclear decommissioning trust funds	3,943	3,772
Other	1,009	979
Total other noncurrent assets	8,140	7,604
Total Assets	39,339	37,720
Current Liabilities
Accounts payable	888	842
Accounts payable to affiliated companies	142	209
Notes payable to affiliated companies	804	104
Taxes accrued	189	234
Interest accrued	141	108
Current maturities of long-term debt (includes amounts related to VIEs)	506	1,205
Asset retirement obligations	292	337
Regulatory liabilities	144	126
Other	419	486
Total current liabilities	3,525	3,651
Long-Term Debt (includes amounts related to VIEs)	9,589	8,598
Long-Term Debt Payable to Affiliated Companies	300	300
Other Noncurrent Liabilities
Deferred income taxes	3,639	3,413
Asset retirement obligations	3,420	3,273
Regulatory liabilities	6,480	6,231
Accrued pension and other post-retirement benefit costs	97	95
Investment tax credits	233	232
Other	508	566
Total other noncurrent liabilities	14,377	13,810
Commitments and Contingencies
Equity
Member's equity	11,554	11,368
Accumulated other comprehensive loss	(6)	(7)
Total member's equity	11,548	11,361
Total Liabilities and Equity	39,339	37,720
Progress Energy [Member]
Current Assets
Cash and cash equivalents	43	40
Receivables (net of allowance for doubtful accounts)	131	123
Receivables of VIEs (net of allowance for doubtful accounts)	1,098	780
Receivables from affiliated companies	15	31
Notes receivable from affiliated companies	445	240
Inventory	1,473	1,592
Regulatory assets (includes amounts related to VIEs)	1,122	741
Other	256	334
Total current assets	4,583	3,881
Property, Plant and Equipment
Cost	49,822	47,323
Accumulated depreciation and amortization	(16,652)	(15,857)
Generation facilities to be retired, net	388	421
Net property, plant and equipment	33,558	31,887
Other Noncurrent Assets
Goodwill	3,655	3,655
Regulatory assets	5,987	6,010
Nuclear decommissioning trust funds	3,477	3,324
Other	1,019	931
Total other noncurrent assets	14,138	13,920
Total Assets	52,279	49,688
Current Liabilities
Accounts payable	1,301	1,006
Accounts payable to affiliated companies	327	251
Notes payable to affiliated companies	794	805
Taxes accrued	244	101
Interest accrued	228	212
Current maturities of long-term debt (includes amounts related to VIEs)	1,322	771
Asset retirement obligations	475	295
Regulatory liabilities	246	213
Other	672	729
Total current liabilities	5,609	4,383
Long-Term Debt (includes amounts related to VIEs)	17,440	16,916
Long-Term Debt Payable to Affiliated Companies	150	150
Other Noncurrent Liabilities
Deferred income taxes	3,947	3,502
Asset retirement obligations	4,960	5,119
Regulatory liabilities	5,275	5,306
Accrued pension and other post-retirement benefit costs	513	545
Other	255	302
Total other noncurrent liabilities	14,950	14,774
Commitments and Contingencies
Equity
Additional paid-in capital	9,143	9,143
Retained earnings	5,009	4,350
Accumulated other comprehensive loss	(24)	(25)
Total Duke Energy Corporation stockholders' equity	14,128	13,468
Noncontrolling interests	2	(3)
Total equity	14,130	13,465
Total Liabilities and Equity	52,279	49,688
Duke Energy Progress [Member]
Current Assets
Cash and cash equivalents	17	20
Receivables (net of allowance for doubtful accounts)	34	56
Receivables of VIEs (net of allowance for doubtful accounts)	635	459
Receivables from affiliated companies	6	3
Notes receivable from affiliated companies	52
Inventory	956	1,017
Regulatory assets (includes amounts related to VIEs)	677	352
Other	112	97
Total current assets	2,489	2,004
Property, Plant and Equipment
Cost	31,091	29,583
Accumulated depreciation and amortization	(11,484)	(10,903)
Generation facilities to be retired, net	388	421
Net property, plant and equipment	19,995	19,101
Other Noncurrent Assets
Regulatory assets	3,822	3,507
Nuclear decommissioning trust funds	2,744	2,588
Other	653	599
Total other noncurrent assets	7,219	6,694
Total Assets	29,703	27,799
Current Liabilities
Accounts payable	808	402
Accounts payable to affiliated companies	252	179
Notes payable to affiliated companies		240
Taxes accrued	92	64
Interest accrued	100	102
Current maturities of long-term debt (includes amounts related to VIEs)	603	3
Asset retirement obligations	470	295
Regulatory liabilities	162	139
Other	353	376
Total current liabilities	2,840	1,800
Long-Term Debt (includes amounts related to VIEs)	7,401	7,204
Long-Term Debt Payable to Affiliated Companies	150	150
Other Noncurrent Liabilities
Deferred income taxes	2,076	1,883
Asset retirement obligations	4,371	4,378
Regulatory liabilities	4,128	3,999
Accrued pension and other post-retirement benefit costs	240	248
Investment tax credits	143	143
Other	48	45
Total other noncurrent liabilities	11,006	10,696
Commitments and Contingencies
Equity
Total member's equity	8,306	7,949
Total Liabilities and Equity	29,703	27,799
Duke Energy Florida [Member]
Current Assets
Cash and cash equivalents	20	13
Receivables (net of allowance for doubtful accounts)	95	65
Receivables of VIEs (net of allowance for doubtful accounts)	463	321
Receivables from affiliated companies	20	2
Notes receivable from affiliated companies	393	313
Inventory	517	574
Regulatory assets (includes amounts related to VIEs)	445	389
Other	27	86
Total current assets	1,980	1,763
Property, Plant and Equipment
Cost	18,722	17,730
Accumulated depreciation and amortization	(5,161)	(4,947)
Net property, plant and equipment	13,561	12,783
Other Noncurrent Assets
Regulatory assets	2,165	2,503
Nuclear decommissioning trust funds	734	736
Other	315	284
Total other noncurrent assets	3,214	3,523
Total Assets	18,755	18,069
Current Liabilities
Accounts payable	492	602
Accounts payable to affiliated companies	83	74
Taxes accrued	232	34
Interest accrued	74	56
Current maturities of long-term debt (includes amounts related to VIEs)	269	768
Asset retirement obligations	4
Regulatory liabilities	84	74
Other	315	334
Total current liabilities	1,553	1,942
Long-Term Debt (includes amounts related to VIEs)	7,102	6,327
Other Noncurrent Liabilities
Deferred income taxes	2,012	1,761
Asset retirement obligations	589	742
Regulatory liabilities	1,146	1,307
Accrued pension and other post-retirement benefit costs	241	264
Other	56	108
Total other noncurrent liabilities	4,044	4,182
Commitments and Contingencies
Equity
Member's equity	6,058	5,614
Accumulated other comprehensive loss	(2)	4
Total member's equity	6,056	5,618
Total Liabilities and Equity	18,755	18,069
Duke Energy Ohio [Member]
Current Assets
Cash and cash equivalents	7	12
Receivables (net of allowance for doubtful accounts)	112	68
Receivables from affiliated companies	71	133
Notes receivable from affiliated companies		14
Inventory	135	133
Regulatory assets (includes amounts related to VIEs)	41	49
Other	28	39
Total current assets	394	448
Property, Plant and Equipment
Cost	9,176	8,732
Accumulated depreciation and amortization	(2,683)	(2,691)
Net property, plant and equipment	6,493	6,041
Other Noncurrent Assets
Goodwill	920	920
Regulatory assets	427	445
Other	62	21
Total other noncurrent assets	1,409	1,386
Total Assets	8,296	7,875
Current Liabilities
Accounts payable	251	313
Accounts payable to affiliated companies	54	62
Notes payable to affiliated companies	268	29
Taxes accrued	159	190
Interest accrued	34	21
Current maturities of long-term debt (includes amounts related to VIEs)	452	3
Asset retirement obligations	7	3
Regulatory liabilities	57	36
Other	67	71
Total current liabilities	1,349	728
Long-Term Debt (includes amounts related to VIEs)	1,589	2,039
Long-Term Debt Payable to Affiliated Companies	25	25
Other Noncurrent Liabilities
Deferred income taxes	790	781
Asset retirement obligations	91	81
Regulatory liabilities	865	891
Accrued pension and other post-retirement benefit costs	84	59
Other	113	108
Total other noncurrent liabilities	1,943	1,920
Equity
Common stock	762	762
Additional paid-in capital	2,776	2,670
Retained earnings	(148)	(269)
Total Duke Energy Corporation stockholders' equity	3,390	3,163
Total Liabilities and Equity	8,296	7,875
Duke Energy Indiana [Member]
Current Assets
Cash and cash equivalents	17	9
Receivables (net of allowance for doubtful accounts)	56	57
Receivables from affiliated companies	98	125
Inventory	434	450
Regulatory assets (includes amounts related to VIEs)	190	165
Other	64	30
Total current assets	859	836
Property, Plant and Equipment
Cost	15,298	14,948
Accumulated depreciation and amortization	(4,831)	(4,662)
Net property, plant and equipment	10,467	10,286
Other Noncurrent Assets
Regulatory assets	950	978
Other	233	189
Total other noncurrent assets	1,183	1,167
Total Assets	12,509	12,289
Current Liabilities
Accounts payable	177	196
Accounts payable to affiliated companies	72	78
Notes payable to affiliated companies	201	161
Taxes accrued	44	95
Interest accrued	54	57
Current maturities of long-term debt (includes amounts related to VIEs)	62	3
Asset retirement obligations	128	54
Regulatory liabilities	25	24
Other	109	104
Total current liabilities	872	772
Long-Term Debt (includes amounts related to VIEs)	3,571	3,630
Long-Term Debt Payable to Affiliated Companies	150	150
Other Noncurrent Liabilities
Deferred income taxes	988	925
Asset retirement obligations	616	727
Regulatory liabilities	1,761	1,723
Accrued pension and other post-retirement benefit costs	110	76
Investment tax credits	147	147
Other	31	18
Total other noncurrent liabilities	3,653	3,616
Equity
Total member's equity	4,263	4,121
Total Liabilities and Equity	12,509	12,289
Piedmont Natural Gas [Member]
Current Assets
Cash and cash equivalents	6	19
Receivables (net of allowance for doubtful accounts)	83	275
Receivables from affiliated companies	10	7
Notes receivable from affiliated companies	11
Inventory	51	66
Regulatory assets (includes amounts related to VIEs)	38	95
Other	48	52
Total current assets	247	514
Property, Plant and Equipment
Cost	7,265	6,725
Accumulated depreciation and amortization	(1,553)	(1,479)
Net property, plant and equipment	5,712	5,246
Other Noncurrent Assets
Goodwill	49	49
Regulatory assets	305	283
Investments in equity method unconsolidated affiliates	63	61
Other	65	65
Total other noncurrent assets	482	458
Total Assets	6,441	6,218
Current Liabilities
Accounts payable	131	125
Accounts payable to affiliated companies	27	13
Notes payable to affiliated companies		364
Taxes accrued	31	19
Interest accrued	25	31
Current maturities of long-term debt (includes amounts related to VIEs)	350	250
Regulatory liabilities	34	3
Other	51	69
Total current liabilities	649	874
Long-Term Debt (includes amounts related to VIEs)	1,788	1,787
Other Noncurrent Liabilities
Deferred income taxes	586	564
Asset retirement obligations	15	15
Regulatory liabilities	1,171	1,141
Accrued pension and other post-retirement benefit costs	3	5
Other	186	170
Total other noncurrent liabilities	1,961	1,895
Commitments and Contingencies
Equity
Common stock	1,160	860
Retained earnings	883	802
Total Duke Energy Corporation stockholders' equity	2,043	1,662
Total Liabilities and Equity	$ 6,441	$ 6,218

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Allowance for doubtful accounts - receivables	$ 17	$ 14
Regulatory assets, current	1,906	1,437
Other, current assets	1,092	634
Regulatory assets, noncurrent	12,616	12,442
Current maturities of long-term debt	3,455	3,244
Long-Term Debt	$ 50,507	$ 49,035
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	2,000,000,000	2,000,000,000
Common stock, shares outstanding	713,000,000	700,000,000
Variable Interest Entity [Member]
Allowance for doubtful accounts - receivables of VIEs	$ 55	$ 54
Regulatory assets, current	52	51
Regulatory assets, noncurrent	1,055	1,091
Current maturities of long-term debt	228	225
Long-Term Debt	4,015	4,306
Duke Energy Carolinas [Member]
Allowance for doubtful accounts - receivables	2	2
Regulatory assets, current	435	299
Other, current assets	55	19
Regulatory assets, noncurrent	3,188	2,853
Current maturities of long-term debt	506	1,205
Long-Term Debt	9,589	8,598
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	5	4
Regulatory assets, current	1,122	741
Other, current assets	256	334
Regulatory assets, noncurrent	5,987	6,010
Current maturities of long-term debt	1,322	771
Long-Term Debt	$ 17,440	$ 16,916
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	$ 8	$ 7
Regulatory assets, current	52	51
Regulatory assets, noncurrent	1,055	1,091
Current maturities of long-term debt	53	53
Long-Term Debt	1,636	1,689
Duke Energy Progress [Member]
Allowance for doubtful accounts - receivables	2	1
Regulatory assets, current	677	352
Other, current assets	112	97
Regulatory assets, noncurrent	3,822	3,507
Current maturities of long-term debt	603	3
Long-Term Debt	7,401	7,204
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	3
Regulatory assets, current	445	389
Other, current assets	27	86
Regulatory assets, noncurrent	2,165	2,503
Current maturities of long-term debt	269	768
Long-Term Debt	7,102	6,327
Duke Energy Florida [Member] | Variable Interest Entity [Member]
Allowance for doubtful accounts - receivables of VIEs	3	2
Regulatory assets, current	52	51
Other, current assets	14	40
Regulatory assets, noncurrent	1,055	1,091
Current maturities of long-term debt	53	53
Long-Term Debt	1,336	1,389
Duke Energy Ohio [Member]
Allowance for doubtful accounts - receivables	3	3
Regulatory assets, current	41	49
Other, current assets	28	39
Regulatory assets, noncurrent	427	445
Current maturities of long-term debt	452	3
Long-Term Debt	$ 1,589	$ 2,039
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	$ 2
Regulatory assets, current	190	165
Other, current assets	64	30
Regulatory assets, noncurrent	950	978
Current maturities of long-term debt	62	3
Long-Term Debt	3,571	3,630
Piedmont Natural Gas [Member]
Allowance for doubtful accounts - receivables	1	2
Regulatory assets, current	38	95
Other, current assets	48	52
Regulatory assets, noncurrent	305	283
Current maturities of long-term debt	350	250
Long-Term Debt	$ 1,788	$ 1,787
Common stock, shares authorized	100	100
Common stock, shares outstanding	100	100

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
CASH FLOWS FROM OPERATING ACTIVITIES
Net Income	$ 2,190	$ 2,361
Net income (attributable to parent)	2,202	2,356
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and accretion (including amortization of nuclear fuel)	3,447	2,990
Equity component of AFUDC	(175)	(175)
Losses (gains) on sales of other assets	87	(28)
Impairment charges	339	216
Deferred income taxes	1,099	1,016
Equity in earnings of unconsolidated affiliates	(49)	(101)
Accrued pension and other post-retirement benefit costs	46	19
Contributions to qualified pension plans	(141)	(8)
Payments for asset retirement obligations	(389)	(420)
Payment for disposal of other assets	(105)
Other rate case adjustments	37
Provision for rate refunds	375
(Increase) decrease in
Net realized and unrealized mark-to-market and hedging transactions	15	4
Receivables	(288)	80
Inventory	104	248
Other current assets	(648)	(210)
Increase (decrease) in
Accounts payable	389	(554)
Taxes accrued	122	233
Other current liabilities	(180)	(532)
Other assets	(585)	(159)
Other liabilities	(23)	(2)
Net cash provided by operating activities	5,667	4,978
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(6,752)	(5,841)
Contributions to equity method investments	(298)	(370)
Purchases of debt and equity securities	(2,763)	(3,170)
Proceeds from sales and maturities of debt and equity securities	2,718	3,199
Other	(175)	(149)
Net cash used in investing activities	(7,270)	(6,331)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from the issuance of long-term debt	4,110	5,710
Proceeds from the issuance of common stock	834
Payments for the redemption of long-term debt	(2,278)	(2,035)
Proceeds from the issuance of short-term debt with original maturities greater than 90 days	243	265
Payments for the redemption of short-term debt with original maturities greater than 90 days	(207)	(237)
Notes payable and commercial paper	638	(647)
Dividends paid	(1,835)	(1,825)
Other	42	8
Net cash provided by financing activities	1,547	1,239
Net decrease in cash, cash equivalents and restricted cash	(56)	(114)
Cash, cash equivalents and restricted cash at beginning of period	505	541
Cash, cash equivalents and restricted cash at end of period	449	427
Cash and cash equivalents at beginning of period	358
Cash and cash equivalents at end of period	303
Significant non-cash transactions:
Accrued capital expenditures	1,016	740
Non-cash dividends	79
Duke Energy Carolinas [Member]
CASH FLOWS FROM OPERATING ACTIVITIES
Net income (attributable to parent)	936	1,009
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and accretion (including amortization of nuclear fuel)	1,084	1,051
Equity component of AFUDC	(57)	(79)
Losses (gains) on sales of other assets	1
Impairment charges	191
Deferred income taxes	266	330
Accrued pension and other post-retirement benefit costs	3
Contributions to qualified pension plans	(46)
Payments for asset retirement obligations	(174)	(201)
Provision for rate refunds	163
(Increase) decrease in
Net realized and unrealized mark-to-market and hedging transactions	2	1
Receivables	(154)	(40)
Receivable from affiliated companies	(63)	17
Inventory	(11)	50
Other current assets	(54)	8
Increase (decrease) in
Accounts payable	69	(78)
Accounts payable to affiliated companies	(67)	(88)
Taxes accrued	(47)	225
Other current liabilities	(129)	(149)
Other assets	18	(18)
Other liabilities	(47)	(26)
Net cash provided by operating activities	1,884	2,012
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(2,006)	(1,747)
Purchases of debt and equity securities	(1,386)	(1,660)
Proceeds from sales and maturities of debt and equity securities	1,386	1,664
Notes receivable from affiliated companies		66
Other	(103)	(58)
Net cash used in investing activities	(2,109)	(1,735)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from the issuance of long-term debt	991
Payments for the redemption of long-term debt	(704)	(115)
Notes payable to affiliated companies	700	468
Distributions to parent	(750)	(625)
Other	(1)	(1)
Net cash provided by financing activities	236	(273)
Net increase (decrease) in cash and cash equivalents	11	4
Cash and cash equivalents at beginning of period	16	14
Cash and cash equivalents at end of period	27	18
Significant non-cash transactions:
Accrued capital expenditures	299	292
Progress Energy [Member]
CASH FLOWS FROM OPERATING ACTIVITIES
Net Income	910	821
Net income (attributable to parent)	904	814
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and accretion (including amortization of nuclear fuel)	1,458	1,130
Equity component of AFUDC	(80)	(68)
Losses (gains) on sales of other assets	(23)	(20)
Impairment charges	34	137
Deferred income taxes	342	651
Accrued pension and other post-retirement benefit costs	18	(9)
Contributions to qualified pension plans	(45)
Payments for asset retirement obligations	(164)	(190)
Other rate case adjustments	37
Provision for rate refunds	101
(Increase) decrease in
Net realized and unrealized mark-to-market and hedging transactions	14	1
Receivables	(316)	(182)
Receivable from affiliated companies	16	102
Inventory	119	126
Other current assets	(156)	(312)
Increase (decrease) in
Accounts payable	427	(281)
Accounts payable to affiliated companies	76	(59)
Taxes accrued	143	143
Other current liabilities	(28)	(184)
Other assets	(668)	(100)
Other liabilities	(34)	(85)
Net cash provided by operating activities	2,181	1,621
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(2,689)	(2,419)
Purchases of debt and equity securities	(1,216)	(1,393)
Proceeds from sales and maturities of debt and equity securities	1,225	1,411
Net proceeds from the sales of other assets	20
Notes receivable from affiliated companies	(205)	(90)
Other	(142)	(36)
Net cash used in investing activities	(3,007)	(2,527)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from the issuance of long-term debt	1,785	1,720
Payments for the redemption of long-term debt	(719)	(611)
Notes payable to affiliated companies	(11)	(129)
Dividends to parent	(250)	(125)
Other	(3)	(3)
Net cash provided by financing activities	802	852
Net decrease in cash, cash equivalents and restricted cash	(24)	(54)
Cash, cash equivalents and restricted cash at beginning of period	87	110
Cash, cash equivalents and restricted cash at end of period	63	56
Cash and cash equivalents at beginning of period	40
Cash and cash equivalents at end of period	43
Significant non-cash transactions:
Accrued capital expenditures	441	174
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
Net income (attributable to parent)	532	547
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and accretion (including amortization of nuclear fuel)	869	691
Equity component of AFUDC	(41)	(35)
Losses (gains) on sales of other assets	(9)	(4)
Impairment charges	33
Deferred income taxes	187	287
Accrued pension and other post-retirement benefit costs	11	(15)
Contributions to qualified pension plans	(25)
Payments for asset retirement obligations	(133)	(149)
Other rate case adjustments	37
Provision for rate refunds	101
(Increase) decrease in
Net realized and unrealized mark-to-market and hedging transactions	3	(2)
Receivables	(154)	(47)
Receivable from affiliated companies	(3)	(3)
Inventory	62	52
Other current assets	(239)	(34)
Increase (decrease) in
Accounts payable	325	(286)
Accounts payable to affiliated companies	73	(20)
Taxes accrued	28	33
Other current liabilities	(27)	(139)
Other assets	(358)	(49)
Other liabilities	11	(9)
Net cash provided by operating activities	1,283	818
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(1,526)	(1,247)
Purchases of debt and equity securities	(831)	(995)
Proceeds from sales and maturities of debt and equity securities	807	974
Net proceeds from the sales of other assets	20
Notes receivable from affiliated companies	(52)	64
Other	(82)	(26)
Net cash used in investing activities	(1,664)	(1,230)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from the issuance of long-term debt	796	812
Payments for the redemption of long-term debt	(2)	(270)
Notes payable to affiliated companies	(240)
Dividends to parent	(175)	(125)
Other	(1)	(1)
Net cash provided by financing activities	378	416
Net increase (decrease) in cash and cash equivalents	(3)	4
Cash and cash equivalents at beginning of period	20	11
Cash and cash equivalents at end of period	17	15
Significant non-cash transactions:
Accrued capital expenditures	261	116
Duke Energy Florida [Member]
CASH FLOWS FROM OPERATING ACTIVITIES
Net income (attributable to parent)	514	368
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and accretion (including amortization of nuclear fuel)	581	431
Equity component of AFUDC	(40)	(33)
Impairment charges	1	137
Deferred income taxes	169	366
Accrued pension and other post-retirement benefit costs	4	3
Contributions to qualified pension plans	(20)
Payments for asset retirement obligations	(31)	(41)
(Increase) decrease in
Net realized and unrealized mark-to-market and hedging transactions	7	3
Receivables	(163)	(140)
Receivable from affiliated companies	(18)	1
Inventory	57	74
Other current assets	51	(195)
Increase (decrease) in
Accounts payable	101	6
Accounts payable to affiliated companies	9	(35)
Taxes accrued	198	109
Other current liabilities	1	(45)
Other assets	(308)	(35)
Other liabilities	(58)	(71)
Net cash provided by operating activities	1,055	903
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(1,162)	(1,172)
Purchases of debt and equity securities	(385)	(398)
Proceeds from sales and maturities of debt and equity securities	418	437
Notes receivable from affiliated companies	(80)	(70)
Other	(61)	(10)
Net cash used in investing activities	(1,270)	(1,213)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from the issuance of long-term debt	989	908
Payments for the redemption of long-term debt	(717)	(341)
Notes payable to affiliated companies		(297)
Distributions to parent	(75)
Other	(1)	(1)
Net cash provided by financing activities	196	269
Net decrease in cash, cash equivalents and restricted cash	(19)	(41)
Cash, cash equivalents and restricted cash at beginning of period	53	69
Cash, cash equivalents and restricted cash at end of period	34	28
Cash and cash equivalents at beginning of period	13
Cash and cash equivalents at end of period	20
Significant non-cash transactions:
Accrued capital expenditures	180	102
Duke Energy Ohio [Member]
CASH FLOWS FROM OPERATING ACTIVITIES
Net Income		127
Net income (attributable to parent)	121	127
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and accretion (including amortization of nuclear fuel)	199	196
Equity component of AFUDC	(10)	(8)
Losses (gains) on sales of other assets	106	(1)
Impairment charges		1
Deferred income taxes	9	70
Accrued pension and other post-retirement benefit costs	3	3
Contributions to qualified pension plans		(4)
Payments for asset retirement obligations	(3)	(4)
Provision for rate refunds	23
(Increase) decrease in
Net realized and unrealized mark-to-market and hedging transactions		1
Receivables	(44)	3
Receivable from affiliated companies	62	48
Inventory	(2)	1
Other current assets	12	(8)
Increase (decrease) in
Accounts payable	(47)	(48)
Accounts payable to affiliated companies	(8)	(4)
Taxes accrued	(31)	(21)
Other current liabilities	19	(6)
Other assets	3	(13)
Other liabilities	(17)	(2)
Net cash provided by operating activities	395	331
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(588)	(457)
Cost of removal, net of salvage	(63)	(25)
Notes receivable from affiliated companies	14	7
Other	1
Net cash used in investing activities	(636)	(475)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from the issuance of long-term debt		182
Payments for the redemption of long-term debt	(3)	(2)
Notes payable to affiliated companies	239	(16)
Dividends to parent		(25)
Other		(1)
Net cash provided by financing activities	236	138
Net increase (decrease) in cash and cash equivalents	(5)	(6)
Cash and cash equivalents at beginning of period	12	13
Cash and cash equivalents at end of period	7	7
Significant non-cash transactions:
Accrued capital expenditures	83	65
Non-cash equity contribution from parent or Transfer of ownership interest of certain equity method investees to parent	106
Duke Energy Indiana [Member]
CASH FLOWS FROM OPERATING ACTIVITIES
Net income (attributable to parent)	317	318
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and accretion (including amortization of nuclear fuel)	388	339
Equity component of AFUDC	(28)	(20)
Losses (gains) on sales of other assets		(1)
Impairment charges	30
Deferred income taxes	94	101
Accrued pension and other post-retirement benefit costs	5	4
Contributions to qualified pension plans	(8)
Payments for asset retirement obligations	(49)	(26)
Provision for rate refunds	58
(Increase) decrease in
Receivables	1	53
Receivable from affiliated companies	27	31
Inventory	16	54
Other current assets	(59)	18
Increase (decrease) in
Accounts payable	28	(71)
Accounts payable to affiliated companies	(6)	(1)
Taxes accrued	(51)	115
Other current liabilities	6	(18)
Other assets	29	(24)
Other liabilities	(13)	32
Net cash provided by operating activities	785	904
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(619)	(603)
Purchases of debt and equity securities	(42)	(15)
Proceeds from sales and maturities of debt and equity securities	18	6
Notes receivable from affiliated companies		57
Other	3	(40)
Net cash used in investing activities	(640)	(595)
CASH FLOWS FROM FINANCING ACTIVITIES
Payments for the redemption of long-term debt	(1)	(3)
Notes payable to affiliated companies	40
Distributions to parent	(175)	(300)
Other	(1)	(1)
Net cash provided by financing activities	(137)	(304)
Net increase (decrease) in cash and cash equivalents	8	5
Cash and cash equivalents at beginning of period	9	17
Cash and cash equivalents at end of period	17	22
Significant non-cash transactions:
Accrued capital expenditures	71	101
Piedmont Natural Gas [Member]
CASH FLOWS FROM OPERATING ACTIVITIES
Net income (attributable to parent)	81	76
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and accretion (including amortization of nuclear fuel)	120	112
Impairment charges		7
Deferred income taxes	2	127
Equity in earnings of unconsolidated affiliates	(6)	(8)
Accrued pension and other post-retirement benefit costs	(3)	9
Provision for rate refunds	31
(Increase) decrease in
Receivables	192	157
Receivable from affiliated companies	(3)	(1)
Inventory	16	13
Other current assets	58	(129)
Increase (decrease) in
Accounts payable	(48)	(52)
Accounts payable to affiliated companies	14	(1)
Taxes accrued	11	(37)
Other current liabilities	8	(21)
Other assets	(4)	(9)
Other liabilities	(5)	(7)
Net cash provided by operating activities	464	236
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(497)	(407)
Cost of removal, net of salvage	(8)
Contributions to equity method investments		(12)
Notes receivable from affiliated companies	(11)
Other	3	2
Net cash used in investing activities	(513)	(417)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from the issuance of long-term debt	100	250
Payments for the redemption of long-term debt		(35)
Notes payable and commercial paper		(330)
Notes payable to affiliated companies	(364)	284
Capital contributions from parent	300
Other		(1)
Net cash provided by financing activities	36	168
Net increase (decrease) in cash and cash equivalents	(13)	(13)
Cash and cash equivalents at beginning of period	19	25
Cash and cash equivalents at end of period	6	12
Significant non-cash transactions:
Accrued capital expenditures	$ 89	47
Non-cash equity contribution from parent or Transfer of ownership interest of certain equity method investees to parent		$ 149

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Changes in Equity - USD ($) $ in Millions	Total		Common Stockholders' Equity [Member]		Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]		Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member]	Net Gains (Losses) on Cash Flow Hedges [Member]	Net Unrealized (Losses) Gains on Available for Sale Securities [Member]		Pension and OPEB Adjustments [Member]	Noncontrolling Interest [Member]		Duke Energy Carolinas [Member]	Duke Energy Carolinas [Member]Member's Equity [Member]	Duke Energy Carolinas [Member]Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member]	Duke Energy Carolinas [Member]Net Gains (Losses) on Cash Flow Hedges [Member]	Progress Energy [Member]		Progress Energy [Member]Common Stockholders' Equity [Member]		Progress Energy [Member]Additional Paid-in Capital [Member]	Progress Energy [Member]Retained Earnings [Member]		Progress Energy [Member]Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member]	Progress Energy [Member]Net Gains (Losses) on Cash Flow Hedges [Member]	Progress Energy [Member]Net Unrealized (Losses) Gains on Available for Sale Securities [Member]		Progress Energy [Member]Pension and OPEB Adjustments [Member]	Progress Energy [Member]Noncontrolling Interest [Member]	Duke Energy Progress [Member]	Duke Energy Florida [Member]	Duke Energy Florida [Member]Member's Equity [Member]		Duke Energy Florida [Member]Net Unrealized (Losses) Gains 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]	Piedmont Natural Gas [Member]	Piedmont Natural Gas [Member]Common Stock [Member]	Piedmont Natural Gas [Member]Retained Earnings [Member]
Beginning Balance at Dec. 31, 2016	$ 41,041		$ 41,033		$ 1	$ 38,741	$ 2,384			$ (20)	$ (1)		$ (72)	$ 8						$ 11,807		$ 11,820		$ 8,094	$ 3,764			$ (23)	$ 1		$ (16)	$ (13)
Beginning Balance, in shares at Dec. 31, 2016					700,000,000
Beginning Balance (member's equity) at Dec. 31, 2016																$ 10,772	$ 10,781		$ (9)														$ 7,358	$ 4,900	$ 4,899		$ 1								$ 4,067
Beginning Balance (parent) at Dec. 31, 2016																																							$ 2,996		$ 762	$ 2,695		$ (461)		$ 1,672	$ 860	$ 812
Net Income	2,361		2,356				2,356							5						821		814			814							7							127
Net income (attributable to parent)	2,356															1,009	1,009			814													547	368	368				127					127	318	76		76
Other comprehensive income (loss)	13		13							1	10		2			1			1	12		12						4	3		5			3			3
Common stock issuances, including dividend reinvestment and employee benefits	33		33			33
Common stock dividends	(1,825)		(1,825)				(1,825)									(625)	(625)			(672)	[1]	(672)	[1]		(672)	[1]							(125)						(25)			(25)			(300)
Distributions to noncontrolling interest in subsidiaries	(2)													(2)
Equitization of certain notes payable to affiliates																				1,047		1,047		1,047
Other	21	[2]	21	[2]			21	[2]								(1)	(1)			2		2		2										3	3											(149)		(149)
Ending Balance at Sep. 30, 2017	41,642		41,631		$ 1	38,774	2,936			$ (19)	9		(70)	11						13,017		13,023		9,143	3,906			$ (19)	4		(11)	(6)
Ending Balance, in shares at Sep. 30, 2017					700,000,000
Ending Balance (member's equity) at Sep. 30, 2017																11,156	11,164		$ (8)														7,780	5,274	5,270		4								4,085
Ending Balance (parent) at Sep. 30, 2017																																							$ 3,098		762	2,670		(334)		$ 1,599	860	739
Beginning Balance at Dec. 31, 2017	$ 41,737		41,739		$ 1	38,792	3,013		$ (10)		12		(69)	(2)						$ 13,465		13,468		9,143	4,350		$ (18)		5		(12)	(3)
Beginning Balance, in shares at Dec. 31, 2017	700,000,000				700,000,000															100																			90,000,000							100
Beginning Balance (member's equity) at Dec. 31, 2017																11,361	11,368	$ (7)															7,949	5,618	5,614		4								4,121
Beginning Balance (parent) at Dec. 31, 2017	$ 41,739																			$ 13,468																			$ 3,163		762	2,670		(269)		$ 1,662	860	802
Net Income	2,190		2,202				2,202							(12)						910		904			904							6
Net income (attributable to parent)	2,202															936	936			904													532	514	514				121					121	317	81		81
Other comprehensive income (loss)	13		13						15		(5)		3			1		1		6		6					5		(1)		2			(1)			(1)
Common stock issuances, including dividend reinvestment and employee benefits, shares					13,000,000
Common stock issuances, including dividend reinvestment and employee benefits	955		955			955
Common stock dividends	(1,914)		(1,914)				(1,914)									(750)	(750)			(250)		(250)			(250)								(175)	(75)	(75)										(175)
Distributions to noncontrolling interest in subsidiaries	(1)													(1)						(1)												(1)
Other	33	[3]					12	[3]			(12)	[3]		33	[3]										5	[4]			(5)	[4]					5	[5]	(5)	[5]	$ 106	[6]		106	[6]			$ 300	300
Ending Balance at Sep. 30, 2018	$ 43,013		$ 42,995		$ 1	$ 39,747	$ 3,313		$ 5		$ (5)		$ (66)	$ 18						$ 14,130		$ 14,128		$ 9,143	$ 5,009		$ (13)		$ (1)		$ (10)	$ 2
Ending Balance, in shares at Sep. 30, 2018	713,000,000				713,000,000															100																			90,000,000							100
Ending Balance (member's equity) at Sep. 30, 2018																$ 11,548	$ 11,554	$ (6)															$ 8,306	$ 6,056	$ 6,058		$ (2)								$ 4,263
Ending Balance (parent) at Sep. 30, 2018	$ 42,995																			$ 14,128																			$ 3,390		$ 762	$ 2,776		$ (148)		$ 2,043	$ 1,160	$ 883
[1]	Includes a $547 million non-cash dividend related to a legal entity restructuring.
[2]	Cumulative-effect adjustment due to implementation of a new accounting standard related to stock-based compensation and the associated income taxes.
[3]	Amounts in Retained Earnings and Accumulated Other Comprehensive Loss represent a cumulative-effect adjustment due to implementation of a new accounting standard related to Financial Instruments Classification and Measurement. See Note 1 for more information. Amount in Noncontrolling Interests relates to tax equity financing activity in the Commercial Renewables segment.
[4]	Amounts in Retained Earnings and Accumulated Other Comprehensive Loss represent a cumulative-effect adjustment due to implementation of a new accounting standard related to Financial Instruments Classification and Measurement. See Note 1 for more information.
[5]	Amounts in Member's Equity and Accumulated Other Comprehensive Income (Loss) represent a cumulative-effect adjustment due to implementation of a new accounting standard related to Financial Instruments Classification and Measurement. See Note 1 for more information.
[6]	Represents a non-cash settlement through equity of an intercompany payable from Duke Energy Ohio to its parent.

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Changes in Equity (Parenthetical) $ in Millions	9 Months Ended
	Sep. 30, 2017USD ($)
Progress Energy [Member]
Dividend to parent related to a legal entity restructuring	$ 547

Organization and Basis of Prese

Organization and Basis of Presentation	9 Months Ended
	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Basis of Presentation	Index to Combined Notes to Condensed Consolidated Financial Statements The unaudited notes to the Condensed Consolidated Financial Statements that follow are a combined presentation. The following list indicates the registrants to which the footnotes apply. Applicable Notes Registrant 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 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. ORGANIZATION AND BASIS OF PRESENTATION 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 separate subsidiary registrants (collectively referred to as the Subsidiary Registrants), which, along with Duke Energy, are collectively referred to as the Duke Energy Registrants. These Condensed 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 Condensed 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 Condensed 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. 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. BASIS OF PRESENTATION These Condensed Consolidated Financial Statements have been prepared in accordance with generally accepted accounting principles in the U.S. (GAAP) for interim financial information and with the instructions to Form 10-Q and Regulation S-X. Accordingly, these Condensed Consolidated Financial Statements do not include all information and notes required by GAAP for annual financial statements. Since the interim Condensed Consolidated Financial Statements and Notes do not include all information and notes required by GAAP in the U.S. for annual financial statements, the Condensed Consolidated Financial Statements and other information included in this quarterly report should be read in conjunction with the Consolidated Financial Statements and Notes in the Duke Energy Registrants’ combined Annual Report on Form 10-K/A for the year ended December 31, 2017 . The information in these combined notes relates to each of the Duke Energy Registrants as noted in the Index to Combined Notes to Condensed Consolidated Financial Statements. However, none of the registrants make any representations as to information related solely to Duke Energy or the subsidiaries of Duke Energy other than itself. These Condensed Consolidated Financial Statements, in the opinion of the respective companies’ management, reflect all normal recurring adjustments necessary to fairly present the financial position and results of operations of each of the Duke Energy Registrants. Amounts reported in Duke Energy’s interim Condensed Consolidated Statements of Operations and each of the Subsidiary Registrants’ interim Condensed Consolidated Statements of Operations and Comprehensive Income are not necessarily indicative of amounts expected for the respective annual periods due to effects of seasonal temperature variations on energy consumption, regulatory rulings, timing of maintenance on electric generating units, changes in mark-to-market valuations, changing commodity prices and other factors. In preparing financial statements that conform to GAAP, management 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. Certain prior year amounts have been reclassified to conform to the current year presentation. REVENUE Duke Energy recognizes revenue as customers obtain control of promised goods and services in an amount that reflects consideration expected in exchange for those goods or services. Generally, the delivery of electricity and natural gas results in the transfer of control to customers at the time the commodity is delivered and the amount of revenue recognized is equal to the amount billed to each customer, including estimated volumes delivered when billings have not yet occurred. See Note 13 for further information. OTHER CURRENT ASSETS Duke Energy recorded a receivable related to the Tax Act in Other within Current Assets in September 2018. As a result, Income taxes receivable exceeds five percent of Total current assets on the Duke Energy Condensed Consolidated Balance Sheets and is $655 million and $260 million as of September 30, 2018 , and December 31, 2017 , respectively. See Note 17 for further information. CASH, CASH EQUIVALENTS AND RESTRICTED CASH Duke Energy, Progress Energy and Duke Energy Florida have restricted cash balances related primarily to collateral assets, escrow deposits and variable interest entities (VIEs). See Note 12 for additional information. Restricted cash amounts are included in Other within Current Assets and Other Noncurrent Assets. The following table presents the components of cash, cash equivalents and restricted cash included in the Condensed Consolidated Balance Sheets. September 30, 2018 December 31, 2017 Duke Duke Duke Progress Energy Duke Progress Energy Energy Energy Florida Energy Energy Florida Current Assets Cash and cash equivalents $ 303 $ 43 $ 20 $ 358 $ 40 $ 13 Other 139 14 14 138 40 40 Other Noncurrent Assets Other 7 6 — 9 7 — Total cash, cash equivalents and restricted cash $ 449 $ 63 $ 34 $ 505 $ 87 $ 53 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 September 30, 2018 , and December 31, 2017 . The components of inventory are presented in the tables below. September 30, 2018 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 $ 2,283 $ 758 $ 1,071 $ 748 $ 323 $ 87 $ 294 $ 1 Coal 515 176 187 99 88 14 138 — Natural gas, oil and other fuel 342 42 215 109 106 34 2 50 Total inventory $ 3,140 $ 976 $ 1,473 $ 956 $ 517 $ 135 $ 434 $ 51 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 fuel 354 35 219 104 115 34 2 64 Total inventory $ 3,250 $ 971 $ 1,592 $ 1,017 $ 574 $ 133 $ 450 $ 66 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, excise taxes are accounted for on a net basis. Excise taxes accounted for on a gross basis within both Operating Revenues and Property and other taxes on the Condensed Consolidated Statements of Operations were as follows. Three Months Ended September 30, Nine Months Ended September 30, (in millions) 2018 2017 2018 2017 Duke Energy $ 114 $ 107 $ 308 $ 289 Duke Energy Carolinas 10 9 27 27 Progress Energy 71 67 181 168 Duke Energy Progress 5 5 15 14 Duke Energy Florida 66 62 166 154 Duke Energy Ohio 26 24 81 75 Duke Energy Indiana 6 6 17 16 Piedmont 1 1 2 3 NEW ACCOUNTING STANDARDS The new accounting standards adopted for 2018 and 2017 had no material impact on the presentation or results of operations, cash flows or financial position of the Duke Energy Registrants. While immaterial, adoption of the following accounting standards had the most significant impact on the Duke Energy results of operations, cash flows and financial position for the nine months ended September 30, 2018 . Revenue from Contracts with Customers. In May 2014, the Financial Accounting Standards Board (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 expected in exchange for those goods or services. The amendments also required 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. The majority of Duke Energy’s revenue is in scope of the new guidance. Other revenue arrangements, such as alternative revenue programs and certain purchase power agreements (PPAs) and lighting agreements accounted for as leases, are excluded from the scope of this guidance and, therefore, are accounted for and evaluated for separate presentation and disclosure under other relevant accounting guidance. Duke Energy elected the modified retrospective method of adoption effective January 1, 2018. Under the modified retrospective method of adoption, prior year reported results are not restated. Adoption of this standard did not result in a material change in the timing or pattern of revenue recognition and a cumulative-effect adjustment was not recorded at January 1, 2018. Duke Energy utilized certain practical expedients including applying this guidance to open contracts at the date of adoption, expensing costs to obtain a contract where the amortization period of the asset would have been one year or less, ignoring the effects of a significant financing when the period between transfer of the good or service and payment is one year or less and recognizing revenues for certain contracts under the invoice practical expedient, which allows revenue recognition to be consistent with invoiced amounts (including unbilled estimates) provided certain criteria are met, including consideration of whether the invoiced amounts reasonably represent the value provided to customers. In preparation for adoption, Duke Energy identified material revenue streams and reviewed representative contracts and tariffs, including those associated with certain long-term customer contracts such as wholesale contracts, PPAs and other customer arrangements. Duke Energy also monitored the activities of the power and utilities industry revenue recognition task force and has reviewed published positions on specific industry issues to evaluate the impact, if any, on Duke Energy’s specific contracts and conclusions. Duke Energy applied the available practical expedient to portfolios of tariffs and contracts with similar characteristics. The vast majority of sales, including energy provided to retail customers, are from tariff offerings that provide natural gas or electricity without a defined contractual term ("at-will"). In most circumstances, revenue from contracts with customers is equivalent to the electricity or natural gas supplied and billed in that period (including unbilled estimates). As such, adoption of the new rules did not result in a shift in the timing or pattern of revenue recognition for such sales. While there have been changes to the captions and descriptions of revenues in Duke Energy’s financial statements, the most significant impact as a result of adopting the standard are additional disclosures around the nature, amount, timing and uncertainty of revenues and cash flows arising from contracts with customers. See Note 13 for further information. Financial Instruments Classification and Measurement. On January 1, 2018, Duke Energy adopted FASB guidance, which revised the classification and measurement of certain financial instruments. The adopted guidance changes the presentation of realized and unrealized gains and losses in certain equity securities that were previously recorded in accumulated other comprehensive income (AOCI). These gains and losses are now recorded in net income. 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. This guidance had a minimal impact on the Duke Energy Registrant's Condensed Consolidated Statements of Operations and Comprehensive Income as changes in the fair value of most of the Duke Energy Registrants' equity securities are deferred as regulatory assets or liabilities pursuant to accounting guidance for regulated operations. The resulting adjustment of unrealized gains and losses in AOCI to retained earnings was immaterial. The primary impact to Duke Energy as a result of implementing this guidance is adding disclosure requirements to present separately the financial assets and financial liabilities by measurement category and form of financial asset. See Notes 10 and 11 for further information. 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 Condensed Consolidated Statements of Cash Flows. Under the updated guidance, restricted cash and restricted cash equivalents are included within beginning-of-period and end-of-period cash and cash equivalents on the Condensed Consolidated Statements of Cash Flows. Duke Energy adopted this guidance on January 1, 2018. The guidance has been applied using a retrospective transition method to each period presented. The adoption by Duke Energy of the revised guidance resulted in a change to the amount of Cash, cash equivalents and restricted cash explained when reconciling the beginning-of-period and end-of-period total amounts shown on the Condensed Consolidated Statements of Cash Flows. In addition, a reconciliation has been provided of Cash, cash equivalents and restricted cash reported within the Condensed Consolidated Balance Sheets that sums to the total of the same such amounts in the Condensed Consolidated Statements of Cash Flows. Prior to adoption, the Duke Energy Registrants reflected changes in noncurrent restricted cash within Cash Flows from Investing Activities and changes in current restricted cash within Cash Flows from Operating Activities on the Condensed Consolidated Statements of Cash Flows. In August 2016, the FASB issued accounting guidance addressing diversity in practice for eight separate cash flow issues. The guidance requires entities to classify distributions received from equity method investees using either the cumulative earnings approach or the nature of the distribution approach. Duke Energy adopted this guidance on January 1, 2018, and elected the nature of distribution approach. This approach requires all distributions received to be categorized based on legal documentation describing the nature of the activities generating the distribution. Cash inflows resulting in a return on investment (surplus) will be reflected in Cash Flows from Operating Activities on the Condensed Consolidated Statements of Cash Flows, whereas cash inflows resulting in a return of investment (capital) will be reflected in Cash Flows from Investing Activities on the Condensed Consolidated Statements of Cash Flows. The guidance has been applied using the retrospective transition method to each period presented. There are no changes to the Condensed Consolidated Statements of Cash Flows for the periods presented as a result of this accounting change. Retirement Benefits. In March 2017, the FASB issued revised accounting guidance for the presentation of net periodic costs related to benefit plans. Previous guidance required the aggregation of all the components of net periodic costs on the Condensed Consolidated Statement of Operations and did not require the disclosure of the location of net periodic costs on the Condensed Consolidated Statement of Operations. Under the amended guidance, the service cost component of net periodic costs is included within Operating Income within the same line as other compensation expenses. All other components of net periodic costs are 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 previous guidance, which permitted all components of net periodic costs to be eligible for capitalization. Duke Energy adopted this guidance on January 1, 2018. Under previous guidance, Duke Energy presented the total non-capitalized net periodic costs within Operation, maintenance and other on the Condensed Consolidated Statements of Operations. The adoption of this guidance resulted 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 utilized the practical expedient for retrospective presentation. The change in components of net periodic costs eligible for capitalization is applicable prospectively. Since Duke Energy’s service cost component is greater than the total net periodic costs, the change results in increased capitalization of net periodic costs, higher Operation, maintenance and other and higher Other income and expenses. The resulting prospective impact to Duke Energy is an immaterial increase in Net Income. See Note 15 for further information. For Duke Energy, the retrospective change resulted in higher Operation, maintenance and other and higher Other income and expenses, net, of $156 million , $131 million and $96 million for the years ended December 31, 2017, 2016 and 2015, respectively. There was no change to Net Income for these prior periods. The following new Accounting Standards Updates (ASUs) have been issued, but have not yet been adopted by Duke Energy, as of September 30, 2018 . 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 will be applied using a modified retrospective approach. Upon adoption, agreements considered leases for the use of certain aircraft, space on communication towers, industrial equipment, fleet vehicles, fuel transportation (barges and railcars), land and office space will be recognized on the balance sheet. Duke Energy expects to elect certain of the following practical expedients upon adoption: Practical Expedient Description Election Package of transition practical expedients (for leases commenced prior to adoption date and must be adopted as a package) Do not need to 1) reassess whether any expired or existing contracts are/or contain leases, 2) reassess the lease classification for any expired or existing leases and 3) reassess initial direct costs for any existing leases. Duke Energy plans to elect this practical expedient. Short-term lease expedient (elect by class of underlying asset) Elect as an accounting policy to not apply the recognition requirements to short-term leases by asset class. Duke Energy plans to elect this practical expedient for all asset classes. Lease and non-lease components (elect by class of underlying asset) Elect as an accounting policy to not separate non-lease components from lease components and instead account for each lease and associated non-lease component as a single lease component by asset class. Duke Energy is currently assessing the election of this practical expedient. Hindsight expedient (when determining lease term) Elect to use hindsight to determine the lease term. Duke Energy plans to elect this practical expedient. Existing and expired land easements not previously accounted for as leases Elect to not evaluate existing or expired easements under the new guidance and carry forward current accounting treatment. Duke Energy plans to elect this practical expedient. Comparative reporting requirements for initial adoption Elect to apply transition requirements at adoption date, recognize cumulative effect adjustment to retained earnings in period of adoption and not apply ASC 842 to comparative periods, including disclosures. Duke Energy plans to elect this practical expedient. Lessor expedient (elect by class of underlying asset) Elect as an accounting policy to aggregate non-lease components with the related lease component when specified conditions are met by asset class. Account for the combined component based on its predominant characteristic (revenue or operating lease). Duke Energy is currently assessing the election of this practical expedient. Duke Energy is currently evaluating the financial statement impact of adopting this standard and is continuing to monitor industry implementation issues, including leases within asset retirement obligations, pipeline laterals and renewable energy PPAs. In arrangements where Duke Energy is the lessee, it expects an increase in assets and liabilities on its balance sheet along with the addition of required disclosures of key lease information. However, the ultimate lessee impact of the new standard has not yet been determined. Duke Energy does not expect a material change to its financial statements from adoption of the new standard for contracts where it is the lessor. 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 is implementing a third-party software tool to help with the adoption and ongoing accounting under the new standard.

Business Segments

Business Segments	9 Months Ended
	Sep. 30, 2018
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 includes intercompany revenues and expenses that are eliminated on the Condensed Consolidated Financial Statements. Certain governance costs are allocated to each segment. In addition, direct interest expense and income taxes are included in segment income. 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 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. Commercial Renewables 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 interest expense on holding company debt, unallocated corporate costs and Duke Energy’s wholly owned captive insurance company, Bison Insurance Company Limited (Bison). Other also includes Duke Energy's 17.5 percent interest in National Methanol Company (NMC), a large regional producer of methyl tertiary butyl ether located in Saudi Arabia. The investment in NMC is accounted for under the equity method of accounting. Business segment information is presented in the following tables. Segment assets presented exclude intercompany assets. Three Months Ended September 30, 2018 Electric Gas Total Utilities and Utilities and Commercial Reportable (in millions) Infrastructure Infrastructure Renewables Segments Other Eliminations Consolidated Unaffiliated revenues $ 6,253 $ 232 $ 127 $ 6,612 $ 16 $ — $ 6,628 Intersegment revenues 7 24 — 31 18 (49 ) — Total revenues $ 6,260 $ 256 $ 127 $ 6,643 $ 34 $ (49 ) $ 6,628 Segment income (loss) (a)(b)(c) $ 1,167 $ 17 $ (62 ) $ 1,122 $ (44 ) $ — $ 1,078 Add back noncontrolling interests (16 ) Income from discontinued operations, net of tax 4 Net income $ 1,066 Segment assets $ 123,847 $ 11,806 $ 4,212 $ 139,865 $ 3,115 $ 185 $ 143,165 Three Months Ended September 30, 2017 Electric Gas Total Utilities and Utilities and Commercial Reportable (in millions) Infrastructure Infrastructure Renewables Segments Other Eliminations Consolidated Unaffiliated revenues $ 6,122 $ 249 $ 95 $ 6,466 $ 16 $ — $ 6,482 Intersegment revenues 7 23 — 30 19 (49 ) — Total revenues $ 6,129 $ 272 $ 95 $ 6,496 $ 35 $ (49 ) $ 6,482 Segment income (loss) (b)(d)(e) $ 1,020 $ 19 $ (49 ) $ 990 $ (34 ) $ — $ 956 Add back noncontrolling interests 1 Loss from discontinued operations, net of tax (2 ) Net income $ 955 (a) All segments include adjustments to the December 31, 2017 estimate of the income tax effects of the Tax Act. See Note 17 for additional information. (b) Other includes costs to achieve the Piedmont acquisition. (c) Commercial Renewables includes an impairment charge related to goodwill. See Note 7 for additional information. (d) Electric Utilities and Infrastructure includes an impairment charge related to the unrecovered Levy Nuclear Project costs at Duke Energy Florida. (e) Commercial Renewables includes impairment charges related to certain wind projects. Nine Months Ended September 30, 2018 Electric Gas Total Utilities and Utilities and Commercial Reportable (in millions) Infrastructure Infrastructure Renewables Segments Other Eliminations Consolidated Unaffiliated revenues $ 16,783 $ 1,229 $ 347 $ 18,359 $ 47 $ — $ 18,406 Intersegment revenues 23 72 — 95 54 (149 ) — Total revenues $ 16,806 $ 1,301 $ 347 $ 18,454 $ 101 $ (149 ) $ 18,406 Segment income (loss) (a)(b)(c)(d)(e)(f) $ 2,492 $ 161 $ (4 ) $ 2,649 $ (446 ) $ — $ 2,203 Add back noncontrolling interests (12 ) Loss from discontinued operations, net of tax (1 ) Net income $ 2,190 Nine Months Ended September 30, 2017 Electric Gas Total Utilities and Utilities and Commercial Reportable (in millions) Infrastructure Infrastructure Renewables Segments Other Eliminations Consolidated Unaffiliated revenues $ 16,211 $ 1,175 $ 333 $ 17,719 $ 47 $ — $ 17,766 Intersegment revenues 23 68 — 91 56 (147 ) — Total revenues $ 16,234 $ 1,243 $ 333 $ 17,810 $ 103 $ (147 ) $ 17,766 Segment income (loss) (c)(g)(h) $ 2,384 $ 179 $ 2 $ 2,565 $ (205 ) $ — $ 2,360 Add back noncontrolling interests 5 Loss from discontinued operations, net of tax (4 ) Net income $ 2,361 (a) All segments include adjustments to the December 31, 2017 estimate of the income tax effects of the Tax Act. See Note 17 for additional information. (b) Electric Utilities and Infrastructure includes regulatory and legislative impairment charges related to rate case orders, settlements or other actions of regulators or legislative bodies. See Note 3 for additional information. (c) Other includes costs to achieve the Piedmont acquisition. (d) Gas Utilities and Infrastructure includes an impairment of the investment in Constitution Pipeline Company, LLC (Constitution). See Note 3 for additional information. (e) Other includes the loss on the sale of the retired Beckjord Generating Station (Beckjord) described below and a valuation allowance recorded against the alternative minimum tax credits subject to sequestration. See Note 17 for additional information on the valuation allowance. (f) Commercial Renewables includes an impairment charge related to goodwill. See Note 7 for additional information. (g) Electric Utilities and Infrastructure includes an impairment charge related to the unrecovered Levy Nuclear Project costs at Duke Energy Florida. (h) Commercial Renewables includes impairment charges related to certain wind projects. In February 2018, Duke Energy sold Beckjord, a nonregulated facility retired during 2014, and recorded a pretax loss of $106 million within Gains (Losses) on Sales of Other Assets and Other, net and $1 million within Operation, maintenance and other on Duke Energy's Condensed Consolidated Statements of Operations for the nine months ended September 30, 2018 . The sale included the transfer of coal ash basins and other real property and indemnification from any and all potential future claims related to the property, whether arising under environmental laws or otherwise. 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. Both reportable operating segments conduct 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 the Ohio Valley Electric Corporation's (OVEC) power plants. See Note 8 for additional information on related party transactions. Three Months Ended September 30, 2018 Electric Gas Total Utilities and Utilities and Reportable (in millions) Infrastructure Infrastructure Segments Other Eliminations Consolidated Total revenues $ 373 $ 84 $ 457 $ 12 $ — $ 469 Segment income/Net income $ 85 $ 12 $ 97 $ 3 $ — $ 100 Segment assets $ 5,484 $ 2,775 $ 8,259 $ 39 $ (2 ) $ 8,296 Three Months Ended September 30, 2017 Electric Gas Total Utilities and Utilities and Reportable (in millions) Infrastructure Infrastructure Segments Other Consolidated Total revenues $ 371 $ 90 $ 461 $ 10 $ 471 Segment income (loss) $ 50 $ 14 $ 64 $ (8 ) $ 56 Loss from discontinued operations, net of tax (1 ) Net income $ 55 Nine Months Ended September 30, 2018 Electric Gas Total Utilities and Utilities and Reportable (in millions) Infrastructure Infrastructure Segments Other Consolidated Total revenues $ 1,055 $ 361 $ 1,416 $ 36 $ 1,452 Segment income (loss)/Net income (a) $ 157 $ 64 $ 221 $ (100 ) $ 121 Nine Months Ended September 30, 2017 Electric Gas Total Utilities and Utilities and Reportable (in millions) Infrastructure Infrastructure Segments Other Consolidated Total revenues $ 1,036 $ 360 $ 1,396 $ 30 $ 1,426 Segment income (loss) $ 96 $ 56 $ 152 $ (24 ) $ 128 Loss from discontinued operations, net of tax (1 ) Net income $ 127 (a) Other includes the loss on the sale of Beckjord.

Regulatory Matters

Regulatory Matters	9 Months Ended
	Sep. 30, 2018
Regulated Operations [Abstract]
Regulatory Matters	REGULATORY MATTERS 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. Duke Energy Carolinas and Duke Energy Progress Grid Improvement – South Carolina On June 22, 2018, Duke Energy Carolinas and Duke Energy Progress filed a joint petition with the PSCSC seeking an accounting order authorizing deferral of certain costs incurred in connection with grid reliability, resiliency and modernization work that is being performed under the companies’ grid improvement initiative. On October 3, 2018, the PSCSC granted Duke Energy Carolinas' and Duke Energy Progress' joint petition. Hurricane Florence Storm Damage In September 2018, Hurricane Florence made landfall and inflicted severe damage to the Duke Energy Carolinas and Duke Energy Progress territories in North Carolina and South Carolina. Approximately 1.8 million customers were impacted. The companies incurred approximately $455 million in operation and maintenance expenses ( $35 million and $420 million for Duke Energy Carolinas and Duke Energy Progress, respectively,) and approximately $85 million in capital costs ( $10 million and $75 million for Duke Energy Carolinas and Duke Energy Progress, respectively,) which are included in Net property, plant and equipment on the Condensed Consolidated Balance Sheets as of September 30, 2018, resulting from the hurricane restoration efforts. Most of the operation and maintenance expenses are deferred in Regulatory assets within Other Noncurrent Assets on the Condensed Consolidated Balance Sheets as of September 30, 2018. The balance of operation and maintenance expenses are included in Operation, maintenance and other on the Condensed Consolidated Statements of Operations for the three and nine months ended September 30, 2018. Given the magnitude of the storm, Duke Energy Progress intends to request approval in North Carolina and South Carolina to defer the incremental costs incurred to a regulatory asset for recovery in the next base rate case. These requests are expected to be filed during the fourth quarter of 2018. Duke Energy Carolinas 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 represented an approximate 13.6 percent increase in annual base revenues. The rate increase was driven by capital investments subsequent to the previous base rate case, including the William States Lee Combined Cycle Facility discussed below, grid improvement projects, advanced metering infrastructure (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 February 28, 2018, Duke Energy Carolinas and the North Carolina Public Staff (Public Staff) filed an Agreement and Stipulation of Partial Settlement resolving certain portions of the proceeding. Terms of the settlement included 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, Duke Energy Carolinas recorded a pretax charge of approximately $4 million to Operation, maintenance and other on the Condensed Consolidated Statements of Operations. On June 1, 2018, Duke Energy Carolinas and certain intervenors filed a Pilot Grid Rider Agreement and Stipulation (Grid Rider Stipulation) in which the parties agreed to the proposal Duke Energy Carolinas introduced in a post-hearing brief on April 27, 2018, along with additional commitments by Duke Energy Carolinas. Also on June 1, 2018, Duke Energy Carolinas and the Commercial Group filed a Partial Stipulation and Settlement Agreement to be considered in conjunction with the Stipulation. Components of the Grid Rider Stipulation included: • Duke Energy Carolinas would recover grid improvement costs through a pilot, three-year Grid Rider except for costs related to targeted undergrounding of power lines, cable and conduit replacement, and power pole replacement; • Excluded costs were to be deferred with a return until Duke Energy Carolinas’ next base rate case proceeding; and • Costs incurred during the three-year pilot, both rider recoverable and deferred, were subject to a 4.5 percent cumulative cap of total annual electric service revenue. On June 22, 2018, the NCUC issued an order approving the Stipulation of Partial Settlement and requiring a revenue reduction. The order also included the following material components not covered in the Stipulation: • Recovery of $554 million of deferred coal ash basin closure costs over a five -year period with a return at Duke Energy Carolinas' weighted average cost of capital (WACC); • Assessment of a $70 million management penalty ratably over a five-year period by reducing the annual recovery of the deferred coal ash costs; • Denial of Duke Energy Carolinas' request for recovery of future estimated ongoing annual coal ash costs of $201 million with approval to defer such costs with a return at Duke Energy Carolinas' WACC, to be considered for recovery in the next rate case; • Inclusion in rates of costs related to the Lee Combined Cycle Facility, two new solar facilities, and AMI deployment as requested; • Recovery of Lee Nuclear Station licensing and development cost of $347 million over a 12 -year period, but denial of a return on the deferred balance of costs; • Reduction in revenue related to lower income tax expense resulting from the Federal Tax Cuts and Jobs Act (Tax Act), and a requirement to maintain all excess deferred income tax (EDIT) resulting from the Tax Act in a regulatory liability account pending flow back to customers as approved by the commission at the earlier of three years or Duke Energy Carolinas’ next general rate case proceeding; and • Denial of the proposed Grid Rider Stipulation related to grid improvement costs and denial of deferral accounting treatment of the costs at this time. Duke Energy Carolinas may petition for deferral of grid modernization costs outside of a general rate case proceeding if it can show financial hardship or a stipulation that includes greater consensus among intervening parties on costs being classified as grid modernization. As a result of the Order, Duke Energy Carolinas recorded a pretax charge of approximately $150 million to Impairment charges and Operation, maintenance and other on the Condensed Consolidated Statements of Operations. The charge is primarily related to the denial of a return on the Lee Nuclear Project and for previously recognized return impacted by the coal ash management penalty described above. On July 27, 2018, NCUC approved Duke Energy Carolinas' compliance filing. As a result, revised customer rates were effective on August 1, 2018. On July 20, 2018, the North Carolina Attorney General filed a Notice of Appeal to the North Carolina Supreme Court from the June 22, 2018, Order Accepting Stipulation, Deciding Contested Issues and Requiring Revenue Reduction issued by the NCUC. The Attorney General contends the commission’s order should be reversed and remanded, as it is in excess of the commission’s statutory authority; affected by errors of law; unsupported by competent, material and substantial evidence in view of the entire record as submitted; and arbitrary or capricious. The Sierra Club, North Carolina Sustainable Energy Association, North Carolina Justice Center, North Carolina Housing Coalition, Natural Resource Defense Council and Southern Alliance for Clean Energy have also filed Notices of Appeal to the North Carolina Supreme Court from the June 22, 2018, Order Accepting Stipulation, Deciding Contested Issues and Requiring Revenue Reduction. On August 8, 2018, the Public Staff filed a Notice of Cross Appeal to the North Carolina Supreme Court from the June 22, 2018, Order Accepting Stipulation, Deciding Contested Issues and Requiring Revenue Reduction issued by the NCUC. The Public Staff contends the commission’s order should be reversed and remanded, as it is affected by errors of law, and is unsupported by substantial evidence with regard to the commission’s failure to consider substantial evidence of coal ash related environmental violations. The briefing will likely be delayed until the second quarter of 2019. Duke Energy Carolinas cannot predict the outcome of this matter. 2018 South Carolina Rate Case On October 8, 2018, Duke Energy Carolinas filed a notice with the PSCSC of the company’s intent to file a base rate adjustment application no earlier than 30 days from the notice submittal date. 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 PPA between the parties by including in its rates amortization expense associated with regulatory assets and recorded in a certain account without FERC approval. 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. Duke Energy Carolinas has issued to PMPA and similarly situated wholesale customers refunds of approximately $25 million . FERC also set the matter for settlement and hearing. PMPA and other customers filed a protest to Duke Energy Carolinas' refund report claiming that the refunds are inadequate in that (1) Duke Energy Carolinas invoked the limitations periods in the contracts to limit the time period for which the refunds were paid and the customers disagree that this limitation applies, and (2) Duke Energy Carolinas refunded only amounts recovered through a certain account and the customers have asserted that the order applies to all regulatory assets. On July 3, 2018, FERC issued an order accepting Duke Energy Carolinas' refund report and ruling that these two claims are outside the scope of FERC's February order. Duke Energy Carolinas will file revised formula rates as well as settlement agreements which are subject to FERC approval. Duke Energy Carolinas cannot predict the outcome of this matter. 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 for the construction and operation of a 750-megawatt (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 its share of the cost to build the facility was approximately $650 million , including allowance for funds used during construction (AFUDC). Approximately $600 million is being recovered through base rate or deferral filings in North Carolina and South Carolina. The remaining amount will be included in future rate filings. The project commenced commercial operation on April 5, 2018. NCEMC owns approximately 13 percent of the project. Lee Nuclear Station In December 2007, Duke Energy Carolinas applied to the NRC for combined operating licenses (COLs) for two Westinghouse Electric Company (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 a result of the COLs being issued. The Duke Energy Carolinas rate case filing discussed above included a request to cancel the development of the Lee Nuclear Station project, recover incurred licensing and development costs and maintain the license issued by the NRC as an option for potential future development. The cancellation request was due to the Westinghouse bankruptcy filing and other market activity. The NCUC Order issued on June 22, 2018, approved the cancellation of the Lee Nuclear Project, allowed Duke Energy Carolinas to continue to maintain the COLs, provided for recovery of the North Carolina retail allocation of project development costs, including AFUDC accrued through December 31, 2017, over 12 years and disallowed any return on the unamortized balance during the 12-year recovery period. Given the recent repeal of certain sections of the Base Load Review Act in South Carolina combined with the cancellation of the project, Duke Energy Carolinas determined that it was no longer probable it would be allowed a return on its share of project development costs attributable to South Carolina. As a result, Duke Energy Carolinas recorded a pretax impairment in the second quarter of $29 million within Impairment charges on the Condensed Consolidated Statements of Operations and Comprehensive Income. South Carolina Petition On June 22, 2018, Duke Energy Carolinas filed a petition with the PSCSC requesting an accounting order to defer certain costs incurred in connection with the addition of the William States Lee Combined Cycle Facility, the ongoing deployment of Duke Energy Carolinas new billing and Customer Information System and the addition of the Carolinas West Primary Distribution Control Center. This request totaling approximately $33 million was approved on July 25, 2018. Sale of Hydroelectric (Hydro) Plants In May 2018, Duke Energy Carolinas entered an agreement for the sale of five hydro plants with a combined 18.7-MW generation capacity in the Western Carolinas region to Northbrook Energy. The completion of the transaction is subject to approval from FERC, as well as other state regulatory agencies and is contingent upon regulatory approval from the NCUC and PSCSC to defer the total estimated loss on the sale of approximately $40 million . On July 5, 2018, Duke Energy Carolinas filed with NCUC for approval of the sale of the five hydro plants to Northbrook, to transfer the Certificates of Public Convenience and Necessity (CPCN) for the four North Carolina hydro plants and to establish a regulatory asset for the North Carolina retail portion of the difference between sales proceeds and net book value. On September 4, 2018, the Public Staff filed comments supporting the CPCN transfer with conditions, specifically that the commission direct Duke Energy Carolinas and the Public Staff to further evaluate the reasonableness of Duke Energy Carolinas' expenditures at the facilities in the 36 months leading up to the agreement for the sale for consideration in the next rate case. On September 18, 2018, Duke Energy Carolinas filed reply comments opposing this condition. The Public Staff also recommended that the amortization period for the regulatory asset start in the month in which the asset transfer is completed, rather than be delayed until the next rate case. On August 28, 2018, Duke Energy Carolinas filed with PSCSC its Application for Approval of Transfer and Sale of Hydroelectric Generation Facilities, Acceptance for Filing of a Power Purchase Agreement and an Accounting Order to Establish a Regulatory Asset. On September 10, 2018, the South Carolina Office of Regulatory Staff (ORS) provided a letter to the commission stating its position on the application and on September 18, 2018, Duke Energy Carolinas requested this matter be carried over to allow Duke Energy Carolinas time to discuss certain accounting issues with the ORS. On October 9, 2018, Duke Energy Carolinas filed a Notice of Application for Transfer of Licenses with the FERC, which provides 30 days to file comments and motions to intervene. If commission approvals are not received, Duke Energy Carolinas can cancel the sales agreement and retain the hydro facilities. If commission approvals are received, the closing is expected to occur during the first quarter of 2019. After closing, Duke Energy Carolinas will purchase all the capacity and energy generated by these facilities at the avoided cost for five years through power purchase agreements. Duke Energy Carolinas cannot predict the outcome of this matter. Duke Energy Progress 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 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 July 10, 2017, the NCUC consolidated Duke Energy Progress' storm deferral request into the Duke Energy Progress rate case docket for decision. On November 22, 2017, Duke Energy Progress and the Public Staff filed an Agreement and Stipulation of Partial Settlement resolving certain portions of the proceeding. Terms of the settlement included 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 Condensed Consolidated Statements of Operations, principally related to disallowances from rate base of certain projects at the Mayo and Sutton plants. On February 23, 2018, the NCUC issued an order approving the stipulation. The order also included the following material components not covered in the stipulation: • Recovery of the remaining $234 million of deferred coal ash basin closure costs over a five -year period with a return at Duke Energy Progress' WACC, excluding $9.5 million of retail deferred coal ash basin costs related to ash hauling at Duke Energy Progress' Asheville Plant; • Assessment of a $30 million management penalty ratably over a five-year period by reducing the annual recovery of the deferred coal ash costs; • Denial of Duke Energy Progress' request for recovery of future estimated ongoing annual coal ash costs of $129 million with approval to defer such costs with a return at Duke Energy Progress' WACC, to be considered for recovery in the next rate case; and • Approval to recover $51 million of the approximately $80 million deferred storm costs over a five -year period with amortization beginning in October 2016. The order did not allow the deferral of the associated capital costs or a return on the deferred balance during the deferral period. The order also impacted certain amounts that were similarly recorded on Duke Energy Carolinas' Condensed Consolidated Balance Sheets. As a result of the order, Duke Energy Progress and Duke Energy Carolinas recorded pretax charges of $68 million and $14 million , respectively, in the first quarter of 2018 to Impairment charges, Operation, maintenance and other and Interest Expense on the Condensed Consolidated Statements of Operations. These charges primarily related to the coal ash basin disallowance and previously recognized return impacted by the coal ash management penalty and deferred storm cost adjustments. Revised customer rates became effective on March 16, 2018. On May 15, 2018, the Public Staff filed a Notice of Cross Appeal to the North Carolina Supreme Court from the February 23, 2018, Order Accepting Stipulation, Deciding Contested Issues and Granting Partial Rate Increase issued by the NCUC. The Public Staff contend the commission’s order should be reversed and remanded, as it is affected by errors of law, and is unsupported by competent, material and substantial evidence in view of the entire record as submitted. The North Carolina Attorney General and Sierra Club have also filed Notices of Appeal to the North Carolina Supreme Court from the February 23, 2018, Order Accepting Stipulation, Deciding Contested Issues and Granting Partial Rate Increase. The briefing will likely be delayed until the second quarter of 2019. Duke Energy Progress cannot predict the outcome of this matter. 2016 South Carolina Rate Case In December 2016, the PSCSC approved a rate case settlement agreement among the ORS, 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. 2018 South Carolina Rate Case On October 8, 2018, Duke Energy Progress filed a notice with the PSCSC of the company’s intent to file a base rate adjustment application no earlier than 30 days from the notice submittal date. 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, 2018, 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 complete 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 $352 million and $385 million is included in Generation facilities to be retired, net on Duke Energy Progress' Condensed Consolidated Balance Sheets as of September 30, 2018 , and December 31, 2017 , respectively. Duke Energy Progress' request for a regulatory asset at the time of retirement with amortization over a 10 -year period was approved by the NCUC on February 23, 2018. 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’ Condensed 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 revised formula rates and amortized over a 15 -year period beginning May 1, 2014. As part of the settlement agreement for the 2017 North Carolina Rate Case discussed above, Duke Energy Progress will amortize the regulatory asset over an eight -year period. NCUC approved the settlement on February 23, 2018. South Carolina Petitions On June 22, 2018, Duke Energy Progress filed a petition with the PSCSC seeking an accounting order authorizing Duke Energy Progress to adopt new depreciation rates, effective March 16, 2018, that reflect the results of Duke Energy Progress’ most recent depreciation study. Also on June 22, 2018, Duke Energy Progress filed a petition with the PSCSC requesting an accounting order to defer certain costs incurred in connection with the deployment of AMI, the ongoing deployment of Duke Energy Progress' new billing and Customer Information System, new depreciation rates and costs incurred in connection with the return of certain excess deferred state income taxes from North Carolina. These requests totaling approximately $20 million were approved on July 25, 2018. FERC Form 1 Reporting Matter On October 18, 2017, Fayetteville Public Works Commission (FPWC) filed with FERC a complaint against Duke Energy Progress. In the complaint, FPWC alleges that Duke Energy Progress’ change in its method of reporting materials and supplies inventory on FERC Form 1 for 2015 constituted a change in accounting practice that Duke Energy Progress was not permitted to implement without first obtaining FERC approval. On April 23, 2018, FERC issued an order finding that Duke Energy Progress’ new reporting methodology was not proper and required Duke Energy Progress to revise its FERC Form 1s beginning in 2014 and to issue refunds to formula rate customers. Duke Energy Progress estimates that these refunds will total approximately $14 million . On May 23, 2018, Duke Energy Progress filed a request for rehearing alleging that FERC’s order is incorrect. Duke Energy Progress revised its FERC Form 1 filings in June 2018. On August 31, 2018, Duke Energy Progress filed with FERC a refund report memorializing its payment of refunds to FPWC. Duke Energy Progress cannot predict the outcome of this matter. Tax Act As ordered by the NCUC on October 5, 2018, Duke Energy Progress filed a proposal on October 25, 2018, to adjust rates to reflect the reduction in federal corporate income tax rate from 35 to 21 percent for taxable years beginning after December 31, 2017, as outlined in the Tax Act. Duke Energy Progress proposes that this rate decrement be effective for service rendered on and after December 1, 2018. The Public Staff is requested to file comments on the proposal no later than November 14, 2018, and other parties may also file comments on the proposals no later than November 14, 2018. Duke Energy Progress cannot predict the outcome of this matter. Duke Energy Florida Storm Restoration Cost Recovery In September 2017, Duke Energy Florida’s service territory suffered significant damage from Hurricane Irma, resulting in approximately 1.3 million customers experiencing outages. In the fourth quarter of 2017, Duke Energy Florida also incurred preparation costs related to Hurricane Nate. On December 28, 2017, Duke Energy Florida filed a petition with the FPSC to recover incremental storm restoration costs for hurricanes Irma and Nate and to replenish the storm reserve. On February 6, 2018, the FPSC approved a stipulation that would apply tax savings resulting from the Tax Act toward storm costs effective January 2018 in lieu of implementing a storm surcharge. Storm costs are currently expected to be fully recovered by approximately mid-2021. On May 31, 2018, Duke Energy Florida filed a petition for approval of actual storm restoration costs and associated recovery process related to Hurricanes Irma and Nate. The petition is seeking the approval for the recovery in the amount of $510 million in actual recoverable storm restoration costs, including the replenishment of Duke Energy Florida’s storm reserve of $132 million , and the process for recovering these recoverable storm costs. On August 20, 2018, the FPSC approved Duke Energy Florida's unopposed Motion for Continuance filed August 17, 2018, to allow for an evidentiary hearing in this matter. The commission has scheduled the hearing to begin on May 21, 2019. At September 30, 2018, Duke Energy Florida's Condensed Consolidated Balance Sheets included approximately $258 million of recoverable costs under the FPSC's storm rule in Regulatory assets within Current Assets and Other Noncurrent Assets related to storm recovery. Duke Energy Florida cannot predict the outcome of this matter. Tax Act Pursuant to Duke Energy Florida's 2017 Revised and Restated Settlement Agreement, on May 31, 2018, Duke Energy Florida filed a petition related to the Tax Act, which included annual tax savings of $84 million and annual amortization of EDIT of $67 million for a total of $151 million . The pretax revenue requirement impact is $201 million , of which $50 million will be offset with accelerated depreciation of Crystal River 4 and 5 coal units and $151 million will be offset by Hurricane Irma storm cost recovery as explained in the Storm Restoration Cost Recovery section above. The petition is subject to review and approval by the FPSC. Duke Energy Florida cannot predict the outcome of this matter. Citrus County Combined Cycle Facility On October 2, 2014, the FPSC granted Duke Energy Florida a Determination of Need for the construction of a 1,640-MW combined-cycle natural gas plant in Citrus County, Florida. On May 5, 2015, the Florida Department of Environmental Protection approved Duke Energy Florida's Site Certification Application. The project has received all required permits and approvals and construction began in October 2015. The facility is expected to be commercially available by the end of 2018 at an estimated cost of $1.5 billion , including AFUDC. Actual costs are expected to exceed this estimate by an immaterial amount after recoveries; therefore, an impairment is not expected. On April 2, 2018, Duke Energy Florida filed a petition seeking approval to include in base rates the revenue requirements associated with the new facility. The annual retail revenue requirement is approximately $200 million . On July 10, 2018, the FPSC voted to approve Duke Energy Florida's request to include the revenue requirements for the new Citrus County combined-cycle units in base rates. The first 820-MW power block came on line on October 26, 2018, and the rate increase for this unit will be effective in December 2018. The second 820-MW power block remains on track to start serving customers in December 2018. The rate increase for the second unit is expected to take place in January 2019. The plant will receive natural gas from the Sabal Trail pipeline discussed below. Solar Base Rate Adjustment On July 31, 2018, Duke Energy Florida petitioned the FPSC to include in base rates the revenue requirements for its first two solar generation projects, the Hamilton Project and the Columbia Project, as authorized by the 2017 Second Revised and Restated Stipulation and Settlement Agreeme

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments And Contingencies	COMMITMENTS AND CONTINGENCIES 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 asset retirement obligations (ARO) recorded as a result of various environmental regulations, 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 on the Condensed 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 Condensed Consolidated Balance Sheets. Nine Months Ended September 30, 2018 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Balance at beginning of period $ 81 $ 10 $ 15 $ 3 $ 12 $ 47 $ 5 $ 2 Provisions/adjustments 7 3 2 3 (1 ) 3 1 — Cash reductions (20 ) (2 ) (5 ) (1 ) (4 ) (12 ) (1 ) — Balance at end of period $ 68 $ 11 $ 12 $ 5 $ 7 $ 38 $ 5 $ 2 Nine Months Ended September 30, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Balance at beginning of period $ 98 $ 10 $ 18 $ 3 $ 14 $ 59 $ 10 $ 1 Provisions/adjustments (1 ) 2 1 — 1 (3 ) (2 ) 1 Cash reductions (13 ) (2 ) (3 ) — (3 ) (7 ) (1 ) — Balance at end of period $ 84 $ 10 $ 16 $ 3 $ 12 $ 49 $ 7 $ 2 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 $ 57 Duke Energy Carolinas 17 Duke Energy Ohio 30 Piedmont 2 LITIGATION 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. The parties are engaged in discovery. Duke Energy Carolinas and Duke Energy Progress cannot predict the outcome of this matter. NCDEQ State Enforcement Actions In the first quarter of 2013, the 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 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 with the North Carolina Court of Appeals to challenge the trial court’s order. The parties were unable to reach an agreement at mediation in April 2017 and submitted briefs to the trial court on remaining issues to be tried. On August 1, 2018, the Court of Appeals dismissed the appeal and the matter is proceeding before the trial court. No trial date has been scheduled. Duke Energy Carolinas and Duke Energy Progress cannot predict the outcome of this matter. 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. Duke Energy Progress and RRBA each filed motions for summary judgment on March 23, 2018. The court has not yet ruled on these motions. 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 at the Roxboro Plant and one claim relating to the use of nearby water bodies. Duke Energy Progress and RRBA each filed motions for summary judgment on April 17, 2018, and the court has not yet ruled on these motions. On May 8, 2018, on motion from Duke Energy Progress, the court ordered trial in both of the above matters to be consolidated. Trial is currently scheduled for July 15, 2019. 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 granted by the court on March 30, 2018. RRBA had until April 30, 2018, to file an appeal to the Fourth Circuit but did not do so. 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, which was granted by the court on May 29, 2018. RRBA had until June 28, 2018, to file an appeal to the Fourth Circuit but did not do so. On December 5, 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, and on August 13, 2018, the court issued an order denying Duke Energy Carolinas’ motion to dismiss. Duke Energy Carolinas' answer to the complaint was filed on August 27, 2018. On October 10, 2018, Duke Energy Carolinas filed Motions to Dismiss for lack of standing, Motion for Judgment on the Pleadings and Motion to Stay Discovery. A hearing on the motion to stay is scheduled for December 12, 2018, and a scheduling conference has been set for January 2019. Duke Energy Carolinas and Duke Energy Progress cannot predict the outcome of these matters. 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 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 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 that ended at an 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. Settlement payments are being made, and, as of September 30, 2018 , Duke Energy Carolinas and Duke Energy Progress have remaining reserves of $4 million and $2 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 (Sutton). 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. On March 6, 2018, Plaintiffs' counsel voluntarily dismissed the action without prejudice It is not possible to estimate the maximum exposure of loss, if any, that may occur in connection with future claims that might be made by these residents. Asbestos-related Injuries and Damages Claims Duke Energy Carolinas has experienced numerous claims for indemnification and medical cost reimbursement related to asbestos exposure. These claims relate to damages for bodily injuries alleged to have arisen from exposure to or use of asbestos in connection with construction and maintenance activities conducted on its electric generation plants prior to 1985. As of September 30, 2018 , there were 160 asserted claims for non-malignant cases with cumulative relief sought of up to $43 million , and 63 asserted claims for malignant cases with cumulative relief sought of up to $19 million . Based on Duke Energy Carolinas’ experience, it is expected that the ultimate resolution of most of these claims likely will be less than the amount claimed. Duke Energy Carolinas has recognized asbestos-related reserves of $461 million at September 30, 2018 , and $489 million at December 31, 2017 . These reserves are classified in Other within Other Noncurrent Liabilities and Other within Current Liabilities on the Condensed Consolidated Balance Sheets. These reserves are based upon the minimum amount of the range of loss for current and future asbestos claims through 2037, are recorded on an undiscounted basis and incorporate anticipated inflation. In light of the uncertainties inherent in a longer-term forecast, management does not believe they can reasonably estimate the indemnity and medical costs that might be incurred after 2037 related to such potential claims. It is possible Duke Energy Carolinas may incur asbestos liabilities in excess of the recorded reserves. Duke Energy Carolinas has third-party insurance to cover certain losses related to asbestos-related injuries and damages above an aggregate self-insured retention. Duke Energy Carolinas’ cumulative payments began to exceed the self-insurance retention in 2008. Future payments up to the policy limit will be reimbursed by the third-party insurance carrier. The insurance policy limit for potential future insurance recoveries indemnification and medical cost claim payments is $764 million in excess of the self-insured retention. Receivables for insurance recoveries were $553 million at September 30, 2018 , and $585 million at December 31, 2017 . These amounts are classified in Other within Other Noncurrent Assets and Receivables within Current Assets on the Condensed Consolidated Balance Sheets. Duke Energy Carolinas is not aware of any uncertainties regarding the legal sufficiency of insurance claims. Duke Energy Carolinas believes the insurance recovery asset is probable of recovery as the insurance carrier continues to have a strong financial strength rating. Duke Energy Progress and Duke Energy Florida Spent Nuclear Fuel Matters On October 16, 2014, Duke Energy Progress and Duke Energy Florida sued the U.S. in the U.S. Court of Federal Claims. The lawsuit claimed the Department of Energy breached a contract in failing to accept spent nuclear fuel under the Nuclear Waste Policy Act of 1982 and asserted damages for the cost of on-site storage. Duke Energy Progress and Duke Energy Florida asserted damages for the period January 1, 2011, through December 31, 2013, of $48 million and $25 million , respectively. On November 17, 2017, the court awarded Duke Energy Progress and Duke Energy Florida $48 million and $21 million , respectively, subject to appeal. No appeals were filed and Duke Energy Progress and Duke Energy Florida recognized the recoveries in the first quarter of 2018. Claims for all periods through 2013 have been resolved. On June 22, 2018, Duke Energy Progress and Duke Energy Florida filed a complaint for damages incurred for 2014 through first quarter 2018. Duke Energy Progress Gypsum Supply Agreement Matter On June 30, 2017, CertainTeed Gypsum NC, Inc. (CertainTeed) filed a declaratory judgment action against Duke Energy Progress in the North Carolina Business Court relating to a gypsum supply agreement. In its complaint, CertainTeed sought an order from the court declaring that the minimum amount of gypsum Duke Energy Progress must provide to CertainTeed under the supply agreement is 50,000 tons per month through 2029. Subsequently, CertainTeed also sought a preliminary injunction requiring Duke Energy Progress to provide 50,000 tons of gypsum per month through the trial date. The parties reached an agreement under which Duke Energy Progress delivered 50,000 tons of gypsum per month through August 2018. Trial in this matter was completed on July 16, 2018. On August 29, 2018, the court issued an order and opinion finding that Duke Energy Progress is required to supply 50,000 tons of gypsum/month, but that CertainTeed’s sole remedy for Duke Energy Progress’ long-term discontinuance under the agreement is liquidated damages. This ruling effectively limits CertainTeed’s remedies in the event that Duke Energy Progress elects to permanently discontinue gypsum supply at the Roxboro plant. The estimated maximum amount that would be owed under the liquidated damages provision is approximately $90 million . Both CertainTeed and Duke Energy Progress have filed cross-appeals, as they explore a possible resolution. Duke Energy Progress cannot predict the outcome of this matter. Duke Energy Florida Class Action Lawsuit On February 22, 2016, a lawsuit was filed in the U.S. District Court for the Southern District of Florida on behalf of a putative class of Duke Energy Florida and FP&L’s customers in Florida. The suit alleges the state of Florida’s nuclear power plant cost recovery statutes (NCRS) are unconstitutional and pre-empted by federal law. Plaintiffs claim they are entitled to repayment of all money paid by customers of Duke Energy Florida and FP&L as a result of the NCRS, as well as an injunction against any future charges under those statutes. The constitutionality of the NCRS has been challenged unsuccessfully in a number of prior cases on alternative grounds. Duke Energy Florida and FP&L filed motions to dismiss the complaint on May 5, 2016. On September 21, 2016, the court granted the motions to dismiss with prejudice. Plaintiffs filed a motion for reconsideration, which was denied. On January 4, 2017, plaintiffs filed a notice of appeal to the Eleventh Circuit U.S. Court of Appeals (Eleventh Circuit). On July 11, 2018, the Eleventh Circuit affirmed the U.S. District Court's dismissal of the lawsuit. The deadline to file a petition for cert was October 9, 2018, and no petition was filed; therefore, the dismissal of the lawsuit is final. Westinghouse Contract Litigation On March 28, 2014, Duke Energy Florida filed a lawsuit against Westinghouse in the U.S. District Court for the Western District of North Carolina. The lawsuit sought recovery of $54 million in milestone payments in excess of work performed under an Engineering, Procurement and Construction agreement (EPC) for Levy as well as a determination by the court of the amounts due to Westinghouse as a result of the termination of an EPC contract. Duke Energy Florida recognized an exit obligation as a result of the termination of the EPC. On March 31, 2014, Westinghouse filed a separate lawsuit against Duke Energy Florida in U.S. District Court for the Western District of Pennsylvania alleging damages under the same EPC contract in excess of $510 million for engineering and design work, costs to end supplier contracts and an alleged termination fee. On June 9, 2014, the judge in the North Carolina case ruled that the litigation would proceed in the Western District of North Carolina. On July 11, 2016, Duke Energy Florida and Westinghouse filed separate Motions for Summary Judgment. On September 29, 2016, the court issued its ruling, granting Westinghouse a $30 million termination fee claim and dismissing Duke Energy Florida's $54 million refund claim. Westinghouse's claim for termination costs continued to trial. Following a trial on the matter, the court issued an order in December 2016 denying Westinghouse’s claim for termination costs and reaffirming its earlier ruling in favor of Westinghouse on the $30 million termination fee. Judgment was entered against Duke Energy Florida in the amount of approximately $34 million , which includes prejudgment interest. Westinghouse appealed the trial court's order to the Fourth Circuit and Duke Energy Florida cross-appealed. On March 29, 2017, Westinghouse filed Chapter 11 bankruptcy in the Southern District of New York, which automatically stayed the appeal. On May 23, 2017, the bankruptcy court entered an order lifting the stay with respect to the appeal. Briefing of the appeal concluded on October 20, 2017. Westinghouse and Duke Energy Florida executed a settlement agreement resolving this matter on April 5, 2018. The bankruptcy court approved the settlement and Duke Energy Florida paid approximately $34 million to Westinghouse in July 2018 pursuant to this agreement. At the request of the parties, the Fourth Circuit has dismissed the appeal. MGP Cost Recovery Action On December 30, 2011, Duke Energy Florida filed a lawsuit against FirstEnergy Corp. (FirstEnergy) to recover investigation and remediation costs incurred by Duke Energy Florida in connection with the restoration of two former MGP sites in Florida. Duke Energy Florida alleged that FirstEnergy, as the successor to Associated Gas & Electric Co., owes past and future contribution and response costs of up to $43 million for the investigation and remediation of MGP sites. On December 6, 2016, the trial court entered judgment against Duke Energy Florida in the case. In January 2017, Duke Energy Florida appealed the decision to the U.S. Court of Appeals for the Sixth Circuit, which affirmed the trial court's ruling on April 10, 2018. The dismissal of the lawsuit is therefore final. Other Litigation and Legal Proceedings The Duke Energy Registrants are involved in other legal, tax and regulatory proceedings arising in the ordinary course of business, some of which involve significant amounts. The Duke Energy Registrants believe the final disposition of these proceedings will not have a material effect on their results of operations, cash flows or financial position. 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 related to the termination of an EPC contract discussed above. Reserves are classified on the Condensed 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. (in millions) September 30, 2018 December 31, 2017 Reserves for Legal Matters Duke Energy $ 63 $ 88 Duke Energy Carolinas 11 30 Progress Energy 50 55 Duke Energy Progress 11 13 Duke Energy Florida 23 24 Piedmont 1 2 OTHER COMMITMENTS AND CONTINGENCIES General As part of their normal business, the Duke Energy Registrants are party to various financial guarantees, performance guarantees and other contractual commitments to extend guarantees of credit and other assistance to various subsidiaries, investees and other third parties. These guarantees involve elements of performance and credit risk, which are not fully recognized on the Condensed Consolidated Balance Sheets and have unlimited maximum potential payments. However, the Duke Energy Registrants do not believe these guarantees will have a material effect on their results of operations, cash flows or financial position. In addition, the Duke Energy Registrants enter into various fixed-price, noncancelable commitments to purchase or sell power or natural gas, take-or-pay arrangements, transportation, or throughput agreements and other contracts that may or may not be recognized on their respective Condensed Consolidated Balance Sheets. Some of these arrangements may be recognized at fair value on their respective Condensed Consolidated Balance Sheets if such contracts meet the definition of a derivative and the normal purchase/normal sale (NPNS) exception does not apply. In most cases, the Duke Energy Registrants’ purchase obligation contracts contain provisions for price adjustments, minimum purchase levels and other financial commitments.

Debt and Credit Facilities

Debt and Credit Facilities	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Debt And Credit Facilities	DEBT AND CREDIT FACILITIES SUMMARY OF SIGNIFICANT DEBT ISSUANCES The following table summarizes significant debt issuances (in millions). Nine Months Ended September 30, 2018 Duke Duke Duke Duke Maturity Interest Duke Energy Energy Energy Energy Issuance Date Date Rate Energy (Parent) Carolinas Progress Florida Unsecured Debt March 2018 (a) April 2025 3.950 % $ 250 $ 250 $ — $ — $ — May 2018 (b) May 2021 2.819 % 500 500 — — — September 2018 (c) September 2078 5.625 % 500 500 — — — First Mortgage Bonds March 2018 (d) March 2023 3.050 % 500 — 500 — — March 2018 (d) March 2048 3.950 % 500 — 500 — — June 2018 (e) July 2028 3.800 % 600 — — — 600 June 2018 (e) July 2048 4.200 % 400 — — — 400 August 2018 (f) September 2023 3.375 % 300 — — 300 — August 2018 (f) September 2028 3.700 % 500 — — 500 — Total issuances $ 4,050 $ 1,250 $ 1,000 $ 800 $ 1,000 (a) Debt issued to pay down short-term debt. (b) Debt issued to pay down short-term debt. Debt issuance has a floating interest rate. (c) Callable after September 2023 at par. Debt issued to pay down short-term debt and for general corporate purposes. (d) Debt issued to repay at maturity a $ 300 million first mortgage bond due April 2018, pay down intercompany short-term debt and for general corporate purposes. (e) Debt issued to repay a portion of intercompany short-term debt under money-pool borrowing arrangement and for general corporate purposes. (f) Debt issued to repay short-term debt and for general corporate purposes. CURRENT MATURITIES OF LONG-TERM DEBT The following table shows the significant components of Current Maturities of Long-Term Debt on the Condensed 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 September 30, 2018 Unsecured Debt Progress Energy March 2019 7.050 % $ 450 Duke Energy (Parent) September 2019 5.050 % 500 Piedmont September 2019 2.848 % (b) 350 First Mortgage Bonds Duke Energy Carolinas November 2018 7.000 % 500 Duke Energy Progress January 2019 5.300 % 600 Duke Energy Ohio April 2019 5.450 % 450 Other (a) 605 Current maturities of long-term debt $ 3,455 (a) Includes capital lease obligations, amortizing debt and small bullet maturities. (b) Debt issuance has a floating interest rate. AVAILABLE CREDIT FACILITIES Master Credit Facility In January 2018, Duke Energy extended the termination date of substantially all of its existing $8 billion Master Credit Facility capacity from March 16, 2022, to March 16, 2023. In May 2018, Duke Energy completed the extension process with 100 percent of all commitments to the Master Credit Facility extending to March 16, 2023 . The Duke Energy Registrants, excluding Progress Energy (Parent), have borrowing capacity under the Master Credit Facility up to a specified sublimit 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. The table below includes the current borrowing sublimits and available capacity under the Master Credit Facility. September 30, 2018 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 $ 2,650 $ 1,750 $ 1,400 $ 650 $ 450 $ 600 $ 500 Reduction to backstop issuances Commercial paper (b) (2,519 ) (988 ) (872 ) (150 ) — (216 ) (293 ) — Outstanding letters of credit (55 ) (47 ) (4 ) (2 ) — — — (2 ) Tax-exempt bonds (81 ) — — — — — (81 ) — Coal ash set-aside (500 ) — (250 ) (250 ) — — — — Available capacity under the Master Credit Facility $ 4,845 $ 1,615 $ 624 $ 998 $ 650 $ 234 $ 226 $ 498 (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 on the Condensed Consolidated Balance Sheets. Three-Year Revolving Credit Facility Duke Energy (Parent) has a $1.0 billion revolving credit facility (the Three Year Revolver) through June 2020. As of September 30, 2018 , $500 million has been drawn under the Three Year Revolver. This balance is classified as Long-Term Debt on Duke Energy's Condensed 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 September 2018, Piedmont executed an amendment to its existing senior unsecured term loan (the Piedmont Term Loan). The amendment increased commitments from $250 million to $350 million and extended the maturity date to September 2019. As of September 30, 2018 , the entire $350 million has been drawn under the Piedmont Term Loan. The balance is classified as Current maturities of long-term debt on Piedmont's Condensed Consolidated Balance Sheets.

Asset Retirement Obligations

Asset Retirement Obligations	9 Months Ended
	Sep. 30, 2018
Asset Retirement Obligation [Abstract]
Asset Retirement Obligations	ASSET RETIREMENT OBLIGATIONS The Duke Energy Registrants record AROs when there is a legal obligation to incur retirement costs associated with the retirement of a long-lived asset and the obligation can be reasonably estimated. The following table presents the AROs recorded on the Condensed Consolidated Balance Sheets. September 30, 2018 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) $ 5,367 $ 2,031 $ 3,181 $ 2,650 $ 531 $ — $ — $ — Closure of Ash Impoundments 4,575 1,623 2,175 2,154 20 52 725 — Other 314 58 79 37 42 46 19 15 Total ARO $ 10,256 $ 3,712 $ 5,435 $ 4,841 $ 593 $ 98 $ 744 $ 15 Less: current portion 902 292 475 470 4 7 128 — Total noncurrent ARO $ 9,354 $ 3,420 $ 4,960 $ 4,371 $ 589 $ 91 $ 616 $ 15 (a) Duke Energy amount includes purchase accounting adjustments related to the merger with Progress Energy. ARO Liability Rollforward Actual closure costs incurred could be materially different from current estimates that form the basis of the recorded AROs. The following table presents the change in liability associated with AROs for the Duke Energy Registrants. Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Balance at December 31, 2017 (a) $ 10,175 $ 3,610 $ 5,414 $ 4,673 $ 742 $ 84 $ 781 $ 15 Accretion expense (b) 319 133 168 145 23 3 22 — Liabilities settled (c) (431 ) (198 ) (186 ) (155 ) (31 ) (5 ) (42 ) — Liabilities incurred in the current year 34 8 — — — — 25 — Revisions in estimates of cash flows (d) 159 159 39 178 (141 ) 16 (42 ) — Balance at September 30, 2018 $ 10,256 $ 3,712 $ 5,435 $ 4,841 $ 593 $ 98 $ 744 $ 15 (a) Primarily relates to decommissioning nuclear power facilities, closure of ash impoundments, asbestos removal, closure of landfills at fossil generation facilities, retirement of natural gas mains and removal of renewable energy generation assets. (b) For the nine months ended September 30, 2018 , substantially all accretion expense relates to Duke Energy's regulated operations and has been deferred in accordance with regulatory accounting treatment. (c) Primarily relates to ash impoundment closures and nuclear decommissioning of Crystal River Unit 3. (d) Primarily relates to increases in groundwater monitoring estimates for closure of ash impoundments, partially offset by modifications to the timing of expected cash flows and a reduction for nuclear decommissioning at Crystal River Unit 3 compared to original estimates. Asset retirement costs associated with the AROs for operating plants and retired plants are included in Net property, plant and equipment and Regulatory assets within Other Noncurrent Assets, respectively, on the Condensed Consolidated Balance Sheets.

Goodwill

Goodwill	9 Months Ended
	Sep. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	GOODWILL Duke Energy The following table presents the goodwill by reportable operating segment included on Duke Energy's Condensed Consolidated Balance Sheets at September 30, 2018 , and December 31, 2017 . Electric Utilities Gas Utilities Commercial (in millions) and Infrastructure and Infrastructure Renewables Total Goodwill balance at December 31, 2017 $ 17,379 $ 1,924 $ 122 $ 19,425 Accumulated impairment charges — — (29 ) $ (29 ) Goodwill balance at December 31, 2017, adjusted for accumulated impairment charges $ 17,379 $ 1,924 $ 93 $ 19,396 Goodwill balance at September 30, 2018 $ 17,379 $ 1,924 $ 122 $ 19,425 Accumulated impairment charges — — (122 ) (122 ) Goodwill balance at September 30, 2018, adjusted for accumulated impairment charges $ 17,379 $ 1,924 $ — $ 19,303 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 Condensed Consolidated Balance Sheets at September 30, 2018 , and December 31, 2017 . 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. 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. In the third quarter of 2018, based on the results of the annual quantitative goodwill impairment test, management determined that the fair value of the Commercial Renewables reporting unit was below its respective carrying value, including goodwill. Determination of the Commercial Renewables reporting unit fair value was based on an income approach, which estimates the fair value based on discounted future cash flows. The fair value of the Commercial Renewables reporting unit is impacted by several factors, including forecasted tax credit utilization, the cost of capital, current and forecasted solar and wind volumes, and legislative developments. Certain assumptions used in determining the fair value of the reporting unit in the 2018 impairment test changed from those used in the 2017 annual impairment test including the cost of capital as a result of rising interest rates and the timing of tax credit utilization due to the Tax Act and IRS (Internal Revenue Service) clarification on bonus depreciation in August 2018. Based on the quantitative impairment test, the estimated fair value of the Commercial Renewables reporting unit was below its carrying value by an immaterial amount but still more than the goodwill balance assigned to the reporting unit. As such, the entire remaining goodwill balance of approximately $93 million was impaired during the third quarter of 2018. 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. As such, no other impairment charges were recorded in the third quarter of 2018.

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2018
Related Party Transactions [Abstract]
Related Party Transactions	RELATED PARTY TRANSACTIONS The Subsidiary Registrants engage in related party transactions in accordance with applicable state and federal commission regulations. Refer to the Condensed 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 on the Condensed Consolidated Statements of Operations and Comprehensive Income are presented in the following table. Three Months Ended September 30, Nine Months Ended September 30, (in millions) 2018 2017 2018 2017 Duke Energy Carolinas Corporate governance and shared service expenses (a) $ 214 $ 206 $ 647 $ 645 Indemnification coverages (b) 6 5 17 17 JDA revenue (c) 13 9 66 42 JDA expense (c) 61 39 134 91 Intercompany natural gas purchases (d) 3 3 11 5 Progress Energy Corporate governance and shared service expenses (a) $ 216 $ 207 $ 613 $ 555 Indemnification coverages (b) 8 10 25 29 JDA revenue (c) 61 39 134 91 JDA expense (c) 13 9 66 42 Intercompany natural gas purchases (d) 20 19 58 57 Duke Energy Progress Corporate governance and shared service expenses (a) $ 138 $ 112 $ 382 $ 321 Indemnification coverages (b) 3 4 9 11 JDA revenue (c) 61 39 134 91 JDA expense (c) 13 9 66 42 Intercompany natural gas purchases (d) 20 19 58 57 Duke Energy Florida Corporate governance and shared service expenses (a) $ 78 $ 95 $ 231 $ 234 Indemnification coverages (b) 5 6 16 18 Duke Energy Ohio Corporate governance and shared service expenses (a) $ 85 $ 90 $ 264 $ 275 Indemnification coverages (b) 1 1 3 3 Duke Energy Indiana Corporate governance and shared service expenses (a) $ 105 $ 94 $ 302 $ 281 Indemnification coverages (b) 2 2 6 6 Piedmont Corporate governance and shared service expenses (a) $ 39 $ 11 $ 115 $ 25 Indemnification coverages (b) 1 1 2 2 Intercompany natural gas sales (d) 23 22 69 62 (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 Condensed 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 Condensed Consolidated Statements of Operations and Comprehensive Income. (c) Duke Energy Carolinas and Duke Energy Progress participate in a Joint Dispatch Agreement (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 Condensed 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 Operating revenues, and Duke Energy Carolinas and Duke Energy Progress record the related purchases as a component of Fuel used in electric generation and purchased power on their respective Condensed Consolidated Statements of Operations and Comprehensive Income. These intercompany revenues and expenses are eliminated in consolidation. 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. These transactions of the Subsidiary Registrants were not material for the three and nine months ended September 30, 2018 , and 2017 . As discussed in Note 12 , certain trade receivables have been sold by Duke Energy Ohio and Duke Energy Indiana to Cinergy Receivables Company LLC (CRC), an indirect subsidiary of Duke Energy. The proceeds obtained from the sales of receivables are largely cash but also include a subordinated note from CRC for a portion of the purchase price. 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 for the three and nine months ended September 30, 2018 , and 2017 , which are included in Cost of natural gas on Piedmont's Condensed Consolidated Statements of Operations and Comprehensive Income. Three Months Ended September 30, Nine Months Ended September 30, (in millions) Type of expense 2018 2017 2018 2017 Cardinal Transportation Costs $ 2 $ 2 $ 5 $ 6 Pine Needle Natural Gas Storage Costs 2 2 6 6 Hardy Storage Natural Gas Storage Costs 2 2 7 7 Total $ 6 $ 6 $ 18 $ 19 Piedmont had accounts payable to its equity method investments of $2 million at September 30, 2018 , and December 31, 2017 , related to these transactions. These amounts are included in Accounts payable on the Condensed 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 September 30, 2018 Intercompany income tax receivable $ 32 $ 196 $ 80 $ — $ — $ 22 $ 11 Intercompany income tax payable — — — 77 9 — — December 31, 2017 Intercompany income tax receivable $ — $ 168 $ — $ 44 $ 22 $ — $ 7 Intercompany income tax payable 44 — 21 — — 35 —

Derivatives and Hedging

Derivatives and Hedging	9 Months Ended
	Sep. 30, 2018
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 Condensed Consolidated Balance Sheets. Cash collateral related to derivative instruments executed under master netting arrangements is offset against the collateralized derivatives on the Condensed Consolidated Balance Sheets. The cash impacts of settled derivatives are recorded as operating activities on the Condensed 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 or Treasury locks 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. Gains and losses reclassified out of AOCI for the three and nine months ended September 30, 2018 , and 2017 were not material. 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 primarily include contracts not designated as a hedge because they are accounted for under regulatory accounting or 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 on the Duke Energy Registrant's Condensed Consolidated Statements of Operations and Comprehensive Income. The following table shows notional amounts of outstanding derivatives related to interest rate risk. September 30, 2018 Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Cash flow hedges $ 411 $ — $ — $ — $ — $ — Undesignated contracts 1,127 400 500 250 250 27 Total notional amount (a) $ 1,538 $ 400 $ 500 $ 250 $ 250 $ 27 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 (a) Duke Energy includes amounts related to consolidated VIEs of $411 million in cash flow hedges and $200 million in undesignated contracts as of September 30, 2018 , and $660 million in cash flow hedges as of December 31, 2017 . 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 natural gas costs 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. September 30, 2018 Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy Carolinas Energy Progress Florida Indiana Piedmont Electricity (gigawatt-hours) 170 — — — — 170 — Natural gas (millions of dekatherms) 744 119 167 158 9 1 457 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 LOCATION AND FAIR VALUE OF DERIVATIVE ASSETS AND LIABILITIES RECOGNIZED ON THE CONDENSED 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 Condensed 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 September 30, 2018 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 $ 46 $ 2 $ 3 $ 2 $ 1 $ 8 $ 29 $ 4 Noncurrent 1 — — — — — — — Total Derivative Assets – Commodity Contracts $ 47 $ 2 $ 3 $ 2 $ 1 $ 8 $ 29 $ 4 Interest Rate Contracts Designated as Hedging Instruments Current $ 6 $ 5 $ — $ — $ — $ — $ — $ — Noncurrent 6 — — — — — — — Not Designated as Hedging Instruments Current 1 — — — — — — — Noncurrent 17 — — — — — — — Total Derivative Assets – Interest Rate Contracts $ 30 $ 5 $ — $ — $ — $ — $ — $ — Total Derivative Assets $ 77 $ 7 $ 3 $ 2 $ 1 $ 8 $ 29 $ 4 Derivative Liabilities September 30, 2018 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 $ 26 $ 14 $ 5 $ 5 $ — $ — $ — $ 7 Noncurrent 177 14 17 8 — — — 146 Total Derivative Liabilities – Commodity Contracts $ 203 $ 28 $ 22 $ 13 $ — $ — $ — $ 153 Interest Rate Contracts Designated as Hedging Instruments Current $ 2 $ — $ — $ — $ — $ — $ — $ — Not Designated as Hedging Instruments Current 7 — 6 3 3 1 — — Noncurrent 13 — 9 8 2 3 — — Total Derivative Liabilities – Interest Rate Contracts $ 22 $ — $ 15 $ 11 $ 5 $ 4 $ — $ — Total Derivative Liabilities $ 225 $ 28 $ 37 $ 24 $ 5 $ 4 $ — $ 153 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 OFFSETTING ASSETS AND LIABILITIES The following tables present the line items on the Condensed 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 September 30, 2018 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 $ 53 $ 7 $ 3 $ 2 $ 1 $ 8 $ 29 $ 4 Gross amounts offset (4 ) (2 ) (2 ) (2 ) — — — — Net amounts presented in Current Assets: Other $ 49 $ 5 $ 1 $ — $ 1 $ 8 $ 29 $ 4 Noncurrent Gross amounts recognized $ 24 $ — $ — $ — $ — $ — $ — $ — Gross amounts offset (1 ) — — — — — — — Net amounts presented in Other Noncurrent Assets: Other $ 23 $ — $ — $ — $ — $ — $ — $ — Derivative Liabilities September 30, 2018 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 $ 14 $ 11 $ 8 $ 3 $ 1 $ — $ 7 Gross amounts offset (4 ) (2 ) (2 ) (2 ) — — — — Net amounts presented in Current Liabilities: Other $ 31 $ 12 $ 9 $ 6 $ 3 $ 1 $ — $ 7 Noncurrent Gross amounts recognized $ 190 $ 14 $ 26 $ 16 $ 2 $ 3 $ — $ 146 Gross amounts offset (1 ) — (1 ) (1 ) — — — — Net amounts presented in Other Noncurrent Liabilities: Other $ 189 $ 14 $ 25 $ 15 $ 2 $ 3 $ — $ 146 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 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. September 30, 2018 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 $ 48 $ 26 $ 23 $ 22 $ — Fair value of collateral already posted — — — — — Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered 48 26 23 22 — 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 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	9 Months Ended
	Sep. 30, 2018
Investments, Debt and Equity Securities [Abstract]
Investments In Debt And Equity Securities	INVESTMENTS IN DEBT AND EQUITY SECURITIES Duke Energy’s investments in debt and equity 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 Other Post-Retirement Benefit Obligations (OPEB) plans and (iii) Bison. The Duke Energy Registrants classify investments in debt securities as available-for-sale (AFS) and investments in equity securities as fair value through net income (FV-NI). For investments in debt securities classified as AFS, the unrealized gains and losses are included in other comprehensive income until realized, at which time, they are reported through net income. For investments in equity securities classified as FV-NI, both realized and unrealized gains and losses are reported through net income. Substantially all of Duke Energy’s investments in debt and equity securities qualify for regulatory accounting, and accordingly, all associated realized and unrealized gains and losses on these investments are deferred as a regulatory asset or liability. Duke Energy classifies the majority of 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 securities within the Investment Trusts are considered OTTIs and are recognized immediately and deferred to regulatory accounts where appropriate. 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. 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. If an OTTI exists, the unrealized credit loss is included in earnings. There were no material credit losses as of September 30, 2018 , and December 31, 2017 . Other Investments amounts are recorded in Other within Other Noncurrent Assets on the Condensed Consolidated Balance Sheets. DUKE ENERGY The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. September 30, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 75 $ — $ — $ 115 Equity securities 3,117 48 5,272 2,805 27 4,914 Corporate debt securities 5 10 595 17 2 570 Municipal bonds — 7 346 4 3 344 U.S. government bonds 5 25 974 11 7 1,027 Other debt securities — 3 141 — 1 118 Total NDTF Investments $ 3,127 $ 93 $ 7,403 $ 2,837 $ 40 $ 7,088 Other Investments Cash and cash equivalents $ — $ — $ 21 $ — $ — $ 15 Equity securities 51 — 115 59 — 123 Corporate debt securities — 1 64 1 — 57 Municipal bonds 1 1 85 2 1 83 U.S. government bonds — 1 59 — — 41 Other debt securities — 1 43 — 1 44 Total Other Investments $ 52 $ 4 $ 387 $ 62 $ 2 $ 363 Total Investments $ 3,179 $ 97 $ 7,790 $ 2,899 $ 42 $ 7,451 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected . The table below summarizes the maturity date for debt securities. (in millions) September 30, 2018 Due in one year or less $ 100 Due after one through five years 492 Due after five through 10 years 561 Due after 10 years 1,154 Total $ 2,307 Realized gains and losses, which were determined on a specific identification basis, from sales of FV-NI and AFS securities for the three and nine months ended September 30, 2018 , and from sales of AFS securities for the three and nine months ended September 30, 2017 , were as follows. Three Months Ended Nine Months Ended (in millions) September 30, 2018 September 30, 2018 FV-NI: Realized gains $ 19 $ 85 Realized losses 16 60 AFS: Realized gains 4 14 Realized losses 7 32 Three Months Ended Nine Months Ended (in millions) September 30, 2017 September 30, 2017 Realized gains $ 37 $ 170 Realized losses 25 124 DUKE ENERGY CAROLINAS The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. September 30, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 18 $ — $ — $ 32 Equity securities 1,692 29 2,890 1,531 12 2,692 Corporate debt securities 2 7 372 9 2 359 Municipal bonds — 2 80 — 1 60 U.S. government bonds 1 14 439 3 4 503 Other debt securities — 3 137 — 1 112 Total NDTF Investments $ 1,695 $ 55 $ 3,936 $ 1,543 $ 20 $ 3,758 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected . The table below summarizes the maturity date for debt securities. (in millions) September 30, 2018 Due in one year or less $ 12 Due after one through five years 161 Due after five through 10 years 289 Due after 10 years 566 Total $ 1,028 Realized gains and losses, which were determined on a specific identification basis, from sales of FV-NI and AFS securities for the three and nine months ended September 30, 2018 , and from sales of AFS securities for the three and nine months ended September 30, 2017 , were as follows. Three Months Ended Nine Months Ended (in millions) September 30, 2018 September 30, 2018 FV-NI: Realized gains $ 11 $ 47 Realized losses 8 30 AFS: Realized gains 4 13 Realized losses 6 24 Three Months Ended Nine Months Ended (in millions) September 30, 2017 September 30, 2017 Realized gains $ 20 $ 110 Realized losses 13 76 PROGRESS ENERGY The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. September 30, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 57 $ — $ — $ 83 Equity securities 1,425 19 2,382 1,274 15 2,222 Corporate debt securities 3 3 223 8 — 211 Municipal bonds — 5 266 4 2 284 U.S. government bonds 4 11 535 8 3 524 Other debt securities — — 4 — — 6 Total NDTF Investments $ 1,432 $ 38 $ 3,467 $ 1,294 $ 20 $ 3,330 Other Investments Cash and cash equivalents $ — $ — $ 18 $ — $ — $ 12 Municipal bonds 1 — 48 2 — 47 Total Other Investments $ 1 $ — $ 66 $ 2 $ — $ 59 Total Investments $ 1,433 $ 38 $ 3,533 $ 1,296 $ 20 $ 3,389 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected . The table below summarizes the maturity date for debt securities. (in millions) September 30, 2018 Due in one year or less $ 83 Due after one through five years 268 Due after five through 10 years 217 Due after 10 years 508 Total $ 1,076 Realized gains and losses, which were determined on a specific identification basis, from sales of FV-NI and AFS securities for the three and nine months ended September 30, 2018 , and from sales of AFS securities for the three and nine months ended September 30, 2017 , were as follows. Three Months Ended Nine Months Ended (in millions) September 30, 2018 September 30, 2018 FV-NI: Realized gains $ 8 $ 38 Realized losses 8 30 AFS: Realized gains — 1 Realized losses 1 8 Three Months Ended Nine Months Ended (in millions) September 30, 2017 September 30, 2017 Realized gains $ 16 $ 58 Realized losses 12 47 DUKE ENERGY PROGRESS The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. September 30, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 42 $ — $ — $ 50 Equity securities 1,101 14 1,913 980 12 1,795 Corporate debt securities 2 2 162 6 — 149 Municipal bonds — 5 265 4 2 283 U.S. government bonds 3 8 352 5 2 310 Other debt securities — — 2 — — 4 Total NDTF Investments $ 1,106 $ 29 $ 2,736 $ 995 $ 16 $ 2,591 Other Investments Cash and cash equivalents $ — $ — $ 8 $ — $ — $ 1 Total Other Investments $ — $ — $ 8 $ — $ — $ 1 Total Investments $ 1,106 $ 29 $ 2,744 $ 995 $ 16 $ 2,592 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected . The table below summarizes the maturity date for debt securities. (in millions) September 30, 2018 Due in one year or less $ 40 Due after one through five years 200 Due after five through 10 years 156 Due after 10 years 385 Total $ 781 Realized gains and losses, which were determined on a specific identification basis, from sales of FV-NI and AFS securities for the three and nine months ended September 30, 2018 , and from sales of AFS securities for the three and nine months ended September 30, 2017 , were as follows. Three Months Ended Nine Months Ended (in millions) September 30, 2018 September 30, 2018 FV-NI: Realized gains $ 7 $ 32 Realized losses 7 27 AFS: Realized gains — 1 Realized losses 1 6 Three Months Ended Nine Months Ended (in millions) September 30, 2017 September 30, 2017 Realized gains $ 14 $ 49 Realized losses 11 41 DUKE ENERGY FLORIDA The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. September 30, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 15 $ — $ — $ 33 Equity securities 324 5 469 294 3 427 Corporate debt securities 1 1 61 2 — 62 Municipal bonds — — 1 — — 1 U.S. government bonds 1 3 183 3 1 214 Other debt securities — — 2 — — 2 Total NDTF Investments (b) $ 326 $ 9 $ 731 $ 299 $ 4 $ 739 Other Investments Cash and cash equivalents $ — $ — $ — $ — $ — $ 1 Municipal bonds 1 — 48 2 — 47 Total Other Investments $ 1 $ — $ 48 $ 2 $ — $ 48 Total Investments $ 327 $ 9 $ 779 $ 301 $ 4 $ 787 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected . (b) During the nine months ended September 30, 2018 , 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) September 30, 2018 Due in one year or less $ 43 Due after one through five years 68 Due after five through 10 years 61 Due after 10 years 123 Total $ 295 Realized gains and losses, which were determined on a specific identification basis, from sales of FV-NI and AFS securities for the three and nine months ended September 30, 2018 , and from sales of AFS securities for the three and nine months ended September 30, 2017 , were as follows. Three Months Ended Nine Months Ended (in millions) September 30, 2018 September 30, 2018 FV-NI: Realized gains $ 1 $ 6 Realized losses 1 3 AFS: Realized gains — — Realized losses — 2 Three Months Ended Nine Months Ended (in millions) September 30, 2017 September 30, 2017 Realized gains $ 2 $ 9 Realized losses 1 6 DUKE ENERGY INDIANA The following table presents the estimated fair value of investments in debt and equity securities; equity investments are measured at FV-NI and debt investments are classified as AFS. September 30, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value Investments Equity securities $ 40 $ — $ 78 $ 49 $ — $ 97 Corporate debt securities — — 8 — — 3 Municipal bonds — 1 32 — 1 28 Total Investments $ 40 $ 1 $ 118 $ 49 $ 1 $ 128 (a) Realized and unrealized gains and losses where regulatory accounting is applied are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected . The table below summarizes the maturity date for debt securities. (in millions) September 30, 2018 Due in one year or less $ 2 Due after one through five years 20 Due after five through 10 years 5 Due after 10 years 13 Total $ 40 Realized gains and losses, which were determined on a specific identification basis, from sales of FV-NI and AFS securities for the three and nine months ended September 30, 2018 , and from sales of AFS securities for the three and nine months ended September 30, 2017 , were insignificant.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2018
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 that 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 at fair value using the net asset value (NAV) per share practical expedient. The NAV is derived based on the investment cost, less any impairment, plus or minus changes resulting from observable price changes for an identical or similar investment of the same issuer. 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 three and nine months ended September 30, 2018 , and 2017 . 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 New York Stock Exchange and 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 natural 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 in Duke Energy's Annual Report on Form 10-K/A for the year ended December 31, 2017, for a discussion of the valuation of goodwill and intangible assets. DUKE ENERGY The following tables provide recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets. Derivative amounts in the tables below for all Duke Energy Registrants exclude cash collateral, which is disclosed in Note 9 . See Note 10 for additional information related to investments by major security type for the Duke Energy Registrants. September 30, 2018 (in millions) Total Fair Value Level 1 Level 2 Level 3 Not Categorized NDTF equity securities $ 5,272 $ 5,203 $ — $ — $ 69 NDTF debt securities 2,131 510 1,621 — — Other equity securities 115 115 — — — Other debt securities 272 78 194 — — Derivative assets 77 4 36 37 — Total assets 7,867 5,910 1,851 37 69 Derivative liabilities (225 ) — (72 ) (153 ) — Net assets (liabilities) $ 7,642 $ 5,910 $ 1,779 $ (116 ) $ 69 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 equity securities 123 123 — — — Other 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 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' Condensed Consolidated Statements of Operations and Comprehensive Income. Amounts included in changes of net assets on the Duke Energy Registrants' Condensed Consolidated Balance Sheets are included in regulatory assets or liabilities. All derivative assets and liabilities are presented on a net basis. Three Months Ended September 30, 2018 Three Months Ended September 30, 2017 (in millions) Investments Derivatives (net) Total Investments Derivatives (net) Total Balance at beginning of period $ — $ (97 ) $ (97 ) $ — $ (91 ) $ (91 ) Purchases, sales, issuances and settlements: Settlements — (14 ) (14 ) — (12 ) (12 ) Total (losses) gains included on the Condensed Consolidated Balance Sheet — (5 ) (5 ) — 10 10 Balance at end of period $ — $ (116 ) $ (116 ) $ — $ (93 ) $ (93 ) Nine Months Ended September 30, 2018 Nine Months Ended September 30, 2017 (in millions) Investments Derivatives (net) Total Investments Derivatives (net) Total Balance at beginning of period $ — $ (114 ) $ (114 ) $ 5 $ (166 ) $ (161 ) Total pretax realized or unrealized gains included in comprehensive income — — — 1 — 1 Purchases, sales, issuances and settlements: Purchases — 56 56 — 55 55 Sales — — — (6 ) — (6 ) Settlements — (43 ) (43 ) — (30 ) (30 ) Total (losses) gains included on the Condensed Consolidated Balance Sheet — (15 ) (15 ) — 48 48 Balance at end of period $ — $ (116 ) $ (116 ) $ — $ (93 ) $ (93 ) DUKE ENERGY CAROLINAS The following tables provide recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets. September 30, 2018 (in millions) Total Fair Value Level 1 Level 2 Not Categorized NDTF equity securities $ 2,890 $ 2,821 $ — $ 69 NDTF debt securities 1,046 122 924 — Derivative assets 7 — 7 — Total assets 3,943 2,943 931 69 Derivative liabilities (28 ) — (28 ) — Net assets $ 3,915 $ 2,943 $ 903 $ 69 December 31, 2017 (in millions) Total Fair Value Level 1 Level 2 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 The following table provides a reconciliation of beginning and ending balances of assets and liabilities measured at fair value using Level 3 measurements. Investments Three Months Ended September 30, Nine Months Ended September 30, (in millions) 2018 2017 2018 2017 Balance at beginning of period $ — $ — $ — $ 3 Total pretax realized or unrealized gains included in comprehensive income — — — 1 Purchases, sales, issuances and settlements: Sales — — — (4 ) Balance at end of period $ — $ — $ — $ — PROGRESS ENERGY The following tables provide recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets. September 30, 2018 December 31, 2017 (in millions) Total Fair Value Level 1 Level 2 Total Fair Value Level 1 Level 2 NDTF equity securities $ 2,382 $ 2,382 $ — $ 2,222 $ 2,222 $ — NDTF debt securities 1,085 388 697 1,108 431 677 Other debt securities 66 18 48 59 12 47 Derivative assets 3 — 3 3 1 2 Total assets 3,536 2,788 748 3,392 2,666 726 Derivative liabilities (37 ) — (37 ) (36 ) (1 ) (35 ) Net assets $ 3,499 $ 2,788 $ 711 $ 3,356 $ 2,665 $ 691 DUKE ENERGY PROGRESS The following tables provide recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets. September 30, 2018 December 31, 2017 (in millions) Total Fair Value Level 1 Level 2 Total Fair Value Level 1 Level 2 NDTF equity securities $ 1,913 $ 1,913 $ — $ 1,795 $ 1,795 $ — NDTF debt securities 823 254 569 796 243 553 Other debt securities 8 8 — 1 1 — Derivative assets 2 — 2 2 1 1 Total assets 2,746 2,175 571 2,594 2,040 554 Derivative liabilities (24 ) — (24 ) (18 ) (1 ) (17 ) Net assets $ 2,722 $ 2,175 $ 547 $ 2,576 $ 2,039 $ 537 DUKE ENERGY FLORIDA The following tables provide recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets. September 30, 2018 December 31, 2017 (in millions) Total Fair Value Level 1 Level 2 Total Fair Value Level 1 Level 2 NDTF equity securities $ 469 $ 469 $ — $ 427 $ 427 $ — NDTF debt securities 262 134 128 312 188 124 Other debt securities 48 — 48 48 1 47 Derivative assets 1 — 1 1 — 1 Total assets 780 603 177 788 616 172 Derivative liabilities (5 ) — (5 ) (12 ) — (12 ) Net assets $ 775 $ 603 $ 172 $ 776 $ 616 $ 160 DUKE ENERGY OHIO The following table provides recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets. September 30, 2018 December 31, 2017 (in millions) Total Fair Value Level 2 Level 3 Total Fair Value Level 2 Level 3 Derivative assets $ 8 $ — $ 8 $ 1 $ — $ 1 Derivative liabilities (4 ) (4 ) — (5 ) (5 ) — Net assets (liabilities) $ 4 $ (4 ) $ 8 $ (4 ) $ (5 ) $ 1 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) Three Months Ended September 30, Nine Months Ended September 30, (in millions) 2018 2017 2018 2017 Balance at beginning of period $ 9 $ 3 $ 1 $ 5 Purchases, sales, issuances and settlements: Purchases — — 7 3 Settlements (1 ) (1 ) (2 ) (3 ) Total gains (losses) included on the Condensed Consolidated Balance Sheet — — 2 (3 ) Balance at end of period $ 8 $ 2 $ 8 $ 2 DUKE ENERGY INDIANA The following tables provide recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets. September 30, 2018 December 31, 2017 (in millions) Total Fair Value Level 1 Level 2 Level 3 Total Fair Value Level 1 Level 2 Level 3 Other equity securities $ 78 $ 78 $ — $ — $ 97 $ 97 $ — $ — Other debt securities 40 — 40 — 31 — 31 — Derivative assets 29 — — 29 27 — — 27 Total assets $ 147 $ 78 $ 40 $ 29 $ 155 $ 97 $ 31 $ 27 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) Three Months Ended September 30, Nine Months Ended September 30, (in millions) 2018 2017 2018 2017 Balance at beginning of period $ 44 $ 51 $ 27 $ 16 Purchases, sales, issuances and settlements: Purchases — — 49 52 Settlements (13 ) (11 ) (41 ) (27 ) Total losses included on the Condensed Consolidated Balance Sheet (2 ) (12 ) (6 ) (13 ) Balance at end of period $ 29 $ 28 $ 29 $ 28 PIEDMONT The following tables provide recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets. September 30, 2018 (in millions) Total Fair Value Level 1 Level 3 Derivative assets $ 4 $ 4 $ — Derivative liabilities (153 ) — (153 ) Net (liabilities) assets $ (149 ) $ 4 $ (153 ) December 31, 2017 (in millions) Total Fair Value Level 1 Level 3 Other debt securities $ 1 $ 1 $ — Derivative assets 2 2 — Total assets 3 3 — Derivative liabilities (142 ) — (142 ) Net (liabilities) assets $ (139 ) $ 3 $ (142 ) 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) Three Months Ended September 30, Nine Months Ended September 30, (in millions) 2018 2017 2018 2017 Balance at beginning of period $ (150 ) $ (145 ) $ (142 ) $ (187 ) Total (losses) gains and settlements (3 ) 22 (11 ) 64 Balance at end of period $ (153 ) $ (123 ) $ (153 ) $ (123 ) QUANTITATIVE INFORMATION ABOUT UNOBSERVABLE INPUTS The following tables include quantitative information about the Duke Energy Registrants' derivatives classified as Level 3. September 30, 2018 Fair Value Investment Type (in millions) Valuation Technique Unobservable Input Range Duke Energy Ohio Financial Transmission Rights (FTRs) $ 8 RTO auction pricing FTR price – per megawatt-hour (MWh) $ 1.03 - $ 4.10 Duke Energy Indiana FTRs 29 RTO auction pricing FTR price – per MWh (2.32 ) - 8.11 Piedmont Natural gas contracts (153 ) Discounted cash flow Forward natural gas curves – price per million British thermal unit (MMBtu) 1.74 - 3.41 Duke Energy Total Level 3 derivatives $ (116 ) 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 ) 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. September 30, 2018 December 31, 2017 (in millions) Book Value Fair Value Book Value Fair Value Duke Energy (a) $ 53,962 $ 53,949 $ 52,279 $ 55,331 Duke Energy Carolinas 10,395 10,887 10,103 11,372 Progress Energy 18,912 19,825 17,837 20,000 Duke Energy Progress 8,154 8,231 7,357 7,992 Duke Energy Florida 7,371 7,749 7,095 7,953 Duke Energy Ohio 2,066 2,136 2,067 2,249 Duke Energy Indiana 3,783 4,178 3,783 4,464 Piedmont 2,138 2,175 2,037 2,209 (a) Book value of long-term debt includes $1.6 billion as of September 30, 2018 , and $1.7 billion as of December 31, 2017 , of unamortized debt discount and premium, net in purchase accounting adjustments related to the mergers with Progress Energy and Piedmont that are excluded from fair value of long-term debt. At both September 30, 2018 , and December 31, 2017 , 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	9 Months Ended
	Sep. 30, 2018
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 re-evaluation, 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 the consolidated 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 nine months ended September 30, 2018 , and the year ended December 31, 2017 , 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 Condensed 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 Condensed 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 summarizes the amounts and expiration dates of the credit facilities and associated restricted receivables described above. Duke Energy Duke Energy Duke Energy Duke Energy Carolinas Progress Florida (in millions) CRC DERF DEPR DEFR Expiration date December 2020 December 2020 February 2021 April 2021 Credit facility amount $ 325 $ 450 $ 300 $ 225 Amounts borrowed at September 30, 2018 325 450 300 225 Amounts borrowed at December 31, 2017 325 450 300 225 Restricted Receivables at September 30, 2018 504 795 635 456 Restricted Receivables at December 31, 2017 545 640 459 317 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 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. 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 Condensed Consolidated Balance Sheets. (in millions) September 30, 2018 December 31, 2017 Receivables of VIEs $ 7 $ 4 Regulatory Assets: Current 52 51 Current Assets: Other 14 40 Other Noncurrent Assets: Regulatory assets 1,055 1,091 Current Liabilities: Other 3 10 Current maturities of long-term debt 53 53 Long-Term Debt 1,111 1,164 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 Condensed Consolidated Balance Sheets related to renewables VIEs. (in millions) September 30, 2018 December 31, 2017 Current Assets: Other $ 203 $ 174 Property, plant and equipment, cost 4,025 3,923 Accumulated depreciation and amortization (695 ) (591 ) Other Noncurrent Assets: Other 268 50 Current maturities of long-term debt 175 170 Long-Term Debt 1,604 1,700 Other Noncurrent Liabilities: Deferred income taxes — (148 ) Other Noncurrent Liabilities: Other 225 241 NON-CONSOLIDATED VIEs The following tables summarize the impact of non-consolidated VIEs on the Condensed Consolidated Balance Sheets. September 30, 2018 Duke Energy Duke Duke Pipeline Commercial Other Energy Energy (in millions) Investments (a) Renewables VIEs Total Ohio Indiana Receivables from affiliated companies $ — $ — $ — $ — $ 56 $ 94 Investments in equity method unconsolidated affiliates 729 190 47 966 — — Total assets $ 729 $ 190 $ 47 $ 966 $ 56 $ 94 Other current liabilities — — 3 3 — — Deferred income taxes 14 — — 14 — — Other noncurrent liabilities — — 11 11 — — Total liabilities $ 14 $ — $ 14 $ 28 $ — $ — Net assets $ 715 $ 190 $ 33 $ 938 $ 56 $ 94 (a) See Pipeline Investments table below for further details regarding Investments in equity method unconsolidated affiliates. December 31, 2017 Duke Energy Duke Duke Pipeline Commercial Other Energy Energy (in millions) Investments Renewables VIEs 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 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 4 . 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 balances in these joint ventures. VIE Investment Amount (in millions) Ownership September 30, December 31, Entity Name Interest 2018 2017 ACP 47 % $ 704 $ 397 Sabal Trail (a) 7.5 % — 219 Constitution (b) 24 % 25 81 Total $ 729 $ 697 (a) At December 31, 2017 , Sabal Trail was considered a VIE due to having insufficient equity to finance their own activities without subordinated financial support. However, Sabal Trail is now a fully operational, well capitalized entity. As a result, Sabal Trail has sufficient equity to finance its own activities, and therefore, is no longer considered a VIE. Duke Energy's investment in Sabal Trail was $112 million at September 30, 2018 . (b) During the nine months ended September 30, 2018 , Duke Energy recorded an OTTI of $55 million related to Constitution within Equity in earnings of unconsolidated affiliates on Duke Energy's Condensed Consolidated Statements of Income. See Note 3 for additional information. In 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 $486 million , which represents 47 percent of the outstanding borrowings under the credit facility as of September 30, 2018 . 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 Transmission, LLC (Pioneer). Pioneer is considered a VIE due to having insufficient equity to finance its 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 OVEC having insufficient equity to finance its activities without subordinated financial support. As a counterparty to an inter-company power agreement (ICPA), Duke Energy Ohio has a contractual arrangement to receive entitlements to capacity and energy 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. On March 31, 2018, FirstEnergy Solutions (FES), a subsidiary of FirstEnergy and an ICPA counterparty with a power participation ratio of 4.85 percent, filed for Chapter 11 bankruptcy, which could increase costs allocated to the counterparties. On July 31, 2018, the bankruptcy court rejected the FES ICPA, which means OVEC is an unsecured creditor in the FES bankruptcy proceeding. Duke Energy Ohio cannot predict the impact of the bankruptcy filing on its OVEC interests. In addition, certain proposed environmental rulemaking could result in future increased OVEC 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 turn over 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 2018 2017 2018 2017 Anticipated credit loss ratio 0.5 % 0.5 % 0.3 % 0.3 % Discount rate 2.9 % 2.1 % 2.9 % 2.1 % Receivable turnover rate 13.6 % 13.5 % 10.9 % 10.7 % The following table shows the gross and net receivables sold. Duke Energy Ohio Duke Energy Indiana (in millions) September 30, 2018 December 31, 2017 September 30, 2018 December 31, 2017 Receivables sold $ 218 $ 273 $ 326 $ 312 Less: Retained interests 56 87 94 106 Net receivables sold $ 162 $ 186 $ 232 $ 206 The following table shows sales and cash flows related to receivables sold. Duke Energy Ohio Duke Energy Indiana Three Months Ended Nine Months Ended Three Months Ended Nine Months Ended September 30, September 30, September 30, September 30, (in millions) 2018 2017 2018 2017 2018 2017 2018 2017 Sales Receivables sold $ 450 $ 438 $ 1,478 $ 1,392 $ 754 $ 720 $ 2,140 $ 2,047 Loss recognized on sale 4 2 10 7 5 3 12 9 Cash flows Cash proceeds from receivables sold $ 449 $ 434 $ 1,499 $ 1,421 $ 743 $ 713 $ 2,140 $ 2,064 Collection fees received — 1 1 1 — — 1 1 Return received on retained interests 2 — 5 2 3 2 7 5 Cash flows from sales of receivables are reflected within Operating Activities on Duke Energy Ohio’s and Duke Energy Indiana’s Condensed 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 Condensed 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 .

Revenue

Revenue	9 Months Ended
	Sep. 30, 2018
Revenue from Contract with Customer [Abstract]
Revenue	REVENUE As described in Note 1, Duke Energy adopted Revenue from Contracts with Customers effective January 1, 2018, using the modified retrospective method of adoption, which does not require restatement of prior year reported results. No cumulative effect adjustment was recorded as the vast majority of Duke Energy’s revenues are at-will and without a defined contractual term. Additionally, comparative disclosures for 2018 operating results with the previous revenue recognition rules are not applicable as Duke Energy’s revenue recognition has not materially changed as a result of the new standard. Duke Energy recognizes revenue consistent with amounts billed under tariff offerings or at contractually agreed upon rates based on actual physical delivery of electric or natural gas service, including estimated volumes delivered when billings have not yet occurred. As such, the majority of Duke Energy’s revenues have fixed pricing based on the contractual terms of the published tariffs, with variability in expected cash flows attributable to the customer’s volumetric demand and ultimate quantities of energy or natural gas supplied and used during the billing period. The stand-alone selling price of related sales are designed to support recovery of prudently incurred costs and an appropriate return on invested assets and are primarily governed by published tariff rates or contractual agreements approved by relevant regulatory bodies. As described in Note 1, certain excise taxes and franchise fees 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 as part of revenues. Duke Energy elects to account for all other taxes net of revenues. Performance obligations are satisfied over time as energy or natural gas is delivered and consumed with billings generally occurring monthly and related payments due within 30 days, depending on regulatory requirements. In no event does the timing between payment and delivery of the goods and services exceed one year. Using this output method for revenue recognition provides a faithful depiction of the transfer of electric and natural gas service as customers obtain control of the commodity and benefit from its use at delivery. Additionally, Duke Energy has an enforceable right to consideration for energy or natural gas delivered at any discrete point in time, and will recognize revenue at an amount that reflects the consideration to which Duke Energy is entitled for the energy or natural gas delivered. As described above, the majority of Duke Energy’s tariff revenues are at-will and, as such, related contracts with customers have an expected duration of one year or less and will not have future performance obligations for disclosure. Additionally, other long-term revenue streams, including wholesale contracts, generally provide services that are part of a single performance obligation, the delivery of electricity or natural gas. As such, other than material fixed consideration under long-term contracts, related disclosures for future performance obligations are also not applicable. Duke Energy earns substantially all of its revenues through its reportable segments, Electric Utilities and Infrastructure, Gas Utilities and Infrastructure and Commercial Renewables. Electric Utilities and Infrastructure Electric Utilities and Infrastructure earns the majority of its revenues through retail and wholesale electric service through the generation, transmission, distribution and sale of electricity. Duke Energy generally provides retail and wholesale electric service customers with their full electric load requirements or with supplemental load requirements when the customer has other sources of electricity. Retail electric service is generally marketed throughout Duke Energy's electric service territory through standard service offers. The standard service offers are through tariffs determined by regulators in Duke Energy's regulated service territory. Each tariff, which is assigned to customers based on customer class, has multiple components such as an energy charge, a demand charge, a basic facilities charge and applicable riders. Duke Energy considers each of these components to be aggregated into a single performance obligation for providing electric service, or in the case of distribution only customers in Duke Energy Ohio, for delivering electricity. Electricity is considered a single performance obligation satisfied over time consistent with the series guidance and is provided and consumed over the billing period (generally one month) . Retail electric service is typically provided to at-will customers that can cancel service at any time, without a substantive penalty . Additionally, Duke Energy adheres to applicable regulatory requirements in each jurisdiction to ensure the collectability of amounts billed and appropriate mitigating procedures are followed when necessary. As such, revenue from contracts with customers for such contracts is equivalent to the electricity supplied and billed in that period (including unbilled estimates). Wholesale electric service is generally provided under long-term contracts using cost-based pricing. FERC regulates costs that may be recovered from customers and the amount of return companies are permitted to earn. Wholesale contracts include both energy and demand charges. For full requirements contracts, Duke Energy considers both charges as a single performance obligation for providing integrated electric service. For contracts where energy and demand charges are considered separate performance obligations, energy and demand are each a distinct performance obligation under the series guidance and are satisfied as energy is delivered and stand-ready service is provided on a monthly basis. This service represents consumption over the billing period and revenue is recognized consistent with billings and unbilled estimates, which generally occur monthly. Contractual amounts owed are typically trued up annually based upon incurred costs in accordance with FERC published filings and the specific customer’s actual peak demand. Estimates of variable consideration related to potential additional billings or refunds owed are updated quarterly. The majority of wholesale revenues are full requirements contracts where the customers purchase the substantial majority of their energy needs and do not have a fixed quantity of contractually required energy or capacity. As such, related forecasted revenues are considered optional purchases. Supplemental requirements contracts that include contracted blocks of energy and capacity at contractually fixed prices have the following estimated remaining performance obligations: Remaining Performance Obligations (in millions) 2018 2019 2020 2021 2022 Thereafter Total Progress Energy $ 24 $ 112 $ 121 $ 80 $ 82 $ 81 $ 500 Duke Energy Progress 2 9 9 9 9 18 56 Duke Energy Florida 22 103 112 71 73 63 444 Duke Energy Indiana 2 9 10 5 — — 26 Revenues for block sales are recognized monthly as energy is delivered and stand-ready service is provided, consistent with invoiced amounts and unbilled estimates. Gas Utilities and Infrastructure Gas Utilities and Infrastructure earns its revenue through retail and wholesale natural gas service through the transportation, distribution and sale of natural gas. Duke Energy generally provides retail and wholesale natural gas service customers with all natural gas load requirements. Additionally, while natural gas can be stored, substantially all natural gas provided by Duke Energy is consumed by customers simultaneously with receipt of delivery. Retail natural gas service is marketed throughout Duke Energy's natural gas service territory using published tariff rates. The tariff rates are established by regulators in Duke Energy's service territories. Each tariff, which is assigned to customers based on customer class, have multiple components, such as a commodity charge , demand charge, customer or monthly charge and transportation costs. Duke Energy considers each of these components to be aggregated into a single performance obligation for providing natural gas service. For contracts where Duke Energy provides all of the customer’s natural gas needs, the delivery of natural gas is considered a single performance obligation satisfied over time, and revenue is recognized monthly based on billings and unbilled estimates as service is provided and the commodity is consumed over the billing period. Additionally, natural gas service is typically at-will and customers can cancel service at any time, without a substantive penalty . Duke Energy also adheres to applicable regulatory requirements to ensure the collectability of amounts billed and receivable and appropriate mitigating procedures are followed when necessary . Certain long-term individually negotiated contracts exist to provide natural gas service. These contracts are regulated and approved by state commissions. The negotiated contracts have multiple components, including a natural gas and a demand charge, similar to retail natural gas contracts. Duke Energy considers each of these components to be a single performance obligation for providing natural gas service. This service represents consumption over the billing period, generally one month. Fixed capacity payments under long-term contracts for the Gas segment include minimum margin contracts and supply arrangements with municipalities and power generation facilities. Revenues for related sales are recognized monthly as natural gas is delivered and stand-ready service is provided, consistent with invoiced amounts and unbilled estimates. Estimated remaining performance obligations are as follows: Remaining Performance Obligations (in millions) 2018 2019 2020 2021 2022 Thereafter Total Piedmont $ 18 $ 71 $ 70 $ 65 $ 64 $ 462 $ 750 Commercial Renewables Commercial Renewables earns the majority of its revenues through long-term PPAs and generally sells all of its wind and solar facility output, electricity and Renewable Energy Credits (RECs) to customers. The majority of these PPAs have historically been accounted for as leases. For PPAs that are not accounted for as leases, the delivery of electricity and the delivery of RECs are considered separate performance obligations. The delivery of electricity is a performance obligation satisfied over time and represents generation and consumption of the electricity over the billing period, generally one month. The delivery of RECs is a performance obligation satisfied at a point in time and represents delivery of each REC generated by the wind or solar facility. The majority of self-generated RECs are bundled with energy in Duke Energy’s contracts and, as such, related revenues are recognized as energy is generated and delivered as that pattern is consistent with Duke Energy’s performance. Commercial Renewables recognizes revenue based on the energy generated and billed for the period, generally one month, at contractual rates (including unbilled estimates) according to the invoice practical expedient. Amounts are typically due within 30 days of invoice. Other The remainder of Duke Energy’s operations is presented as Other, which does not include material revenues from contracts with customers. Disaggregated Revenues For the Electric and Gas segments, revenue by customer class is most meaningful to Duke Energy as each respective customer class collectively represents unique customer expectations of service, generally has different energy and demand requirements, and operates under tailored, regulatory approved pricing structures. Additionally, each customer class is impacted differently by weather and a variety of economic factors including the level of population growth, economic investment, employment levels, and regulatory activities in each of Duke Energy’s jurisdictions. As such, analyzing revenues disaggregated by customer class allows Duke Energy to understand the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. For the Commercial Renewables segment, the majority of revenues from contracts with customers are from selling all of the unit-contingent output at contractually defined pricing under long-term PPAs with consistent expectations regarding the timing and certainty of cash flows. Disaggregated revenues are presented as follows: Three Months Ended September 30, 2018 Duke Duke Duke Duke Duke (in millions) Duke Energy Progress Energy Energy Energy Energy By market or type of customer Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Electric Utilities and Infrastructure Residential $ 2,729 $ 823 $ 1,425 $ 572 $ 853 $ 203 $ 279 $ — General 1,763 635 800 373 427 112 218 — Industrial 835 352 246 177 69 33 202 — Wholesale 589 132 372 335 37 3 81 — Other revenues 225 109 134 90 44 20 29 — Total Electric Utilities and Infrastructure revenue from contracts with customers $ 6,141 $ 2,051 $ 2,977 $ 1,547 $ 1,430 $ 371 $ 809 $ — Gas Utilities and Infrastructure Residential $ 116 $ — $ — $ — $ — $ 59 $ — $ 57 Commercial 66 — — — — 20 — 46 Industrial 28 — — — — 3 — 24 Power Generation — — — — — — — 13 Other revenues 23 — — — — 1 — 22 Total Gas Utilities and Infrastructure revenue from contracts with customers $ 233 $ — $ — $ — $ — $ 83 $ — $ 162 Commercial Renewables Revenue from contracts with customers $ 61 $ — $ — $ — $ — $ — $ — $ — Other Revenue from contracts with customers $ 16 $ — $ — $ — $ — $ 12 $ — $ — Total revenue from contracts with customers $ 6,451 $ 2,051 $ 2,977 $ 1,547 $ 1,430 $ 466 $ 809 $ 162 Other revenue sources (a) $ 177 $ 39 $ 68 $ 35 $ 32 $ 3 $ 10 $ 10 Total revenues $ 6,628 $ 2,090 $ 3,045 $ 1,582 $ 1,462 $ 469 $ 819 $ 172 Nine Months Ended September 30, 2018 Duke Duke Duke Duke Duke (in millions) Duke Energy Progress Energy Energy Energy Energy By market or type of customer Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Electric Utilities and Infrastructure Residential $ 7,264 $ 2,263 $ 3,636 $ 1,540 $ 2,096 $ 564 $ 802 $ — General 4,619 1,608 2,109 972 1,137 318 584 — Industrial 2,235 893 678 481 197 96 567 — Wholesale 1,737 366 1,140 1,019 121 5 226 — Other revenues 558 261 359 222 137 57 66 — Total Electric Utilities and Infrastructure revenue from contracts with customers $ 16,413 $ 5,391 $ 7,922 $ 4,234 $ 3,688 $ 1,040 $ 2,245 $ — Gas Utilities and Infrastructure Residential $ 682 $ — $ — $ — $ — $ 236 $ — $ 446 Commercial 354 — — — — 97 — 257 Industrial 107 — — — — 13 — 93 Power Generation — — — — — — — 40 Other revenues 101 — — — — 13 — 88 Total Gas Utilities and Infrastructure revenue from contracts with customers $ 1,244 $ — $ — $ — $ — $ 359 $ — $ 924 Commercial Renewables Revenue from contracts with customers $ 141 $ — $ — $ — $ — $ — $ — $ — Other Revenue from contracts with customers $ 47 $ — $ — $ — $ — $ 36 $ — $ — Total Revenue from contracts with customers $ 17,845 $ 5,391 $ 7,922 $ 4,234 $ 3,688 $ 1,435 $ 2,245 $ 924 Other revenue sources (a) $ 561 $ 134 $ 197 $ 99 $ 92 $ 17 $ 43 $ 16 Total revenues $ 18,406 $ 5,525 $ 8,119 $ 4,333 $ 3,780 $ 1,452 $ 2,288 $ 940 (a) Other revenue sources include revenues from leases, derivatives and alternative revenue programs that are not considered revenues from contracts with customers. Alternative revenue programs in certain jurisdictions include regulatory mechanisms that periodically adjust for over or under collection of related revenues. IMPACT OF WEATHER AND THE TIMING OF BILLING PERIODS Revenues and costs are influenced by seasonal weather patterns. Peak sales of electricity occur during the summer and winter months , which results in higher revenue and cash flows during these periods. By contrast, lower sales of electricity occur during the spring and fall, allowing for scheduled plant maintenance. Residential and general service customers are more impacted by weather than industrial customers. Estimated weather impacts are based on actual current period weather compared to normal weather conditions. Normal weather conditions are defined as the long-term average of actual historical weather conditions. Heating-degree days measure the variation in weather based on the extent the average daily temperature falls below a base temperature. Cooling-degree days measure the variation in weather based on the extent the average daily temperature rises above the base temperature. Each degree of temperature below the base temperature counts as one heating-degree day and each degree of temperature above the base temperature counts as one cooling-degree day. The estimated impact of weather on earnings for Electric Utilities and Infrastructure is based on the temperature variances from a normal condition and customers' historic usage patterns. The methodology used to estimate the impact of weather does not consider all variables that may impact customer response to weather conditions, such as humidity in the summer or wind chill in the winter. The precision of this estimate may also be impacted by applying long-term weather trends to shorter-term periods. Gas Utilities and Infrastructure's costs and revenues are influenced by seasonal patterns due to peak natural gas sales occurring during the winter months as a result of space heating requirements. Residential customers are the most impacted by weather. There are certain regulatory mechanisms for the North Carolina, South Carolina , Tennessee and Ohio service territories that normalize the margins collected from certain customer classes during the winter. In North Carolina, rate design provides protection from both weather and other usage variations such as conservation, while South Carolina and Tennessee revenues are adjusted solely based on weather. Ohio primarily employs a fixed charge each month regardless of the season and usage. UNBILLED REVENUE 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 Condensed Consolidated Balance Sheets as shown in the following table. (in millions) September 30, 2018 December 31, 2017 Duke Energy $ 802 $ 944 Duke Energy Carolinas 278 342 Progress Energy 283 228 Duke Energy Progress 163 143 Duke Energy Florida 120 85 Duke Energy Ohio 2 4 Duke Energy Indiana 25 21 Piedmont 3 86 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, CRC and accounts for the transfers of receivables as sales. Accordingly, the receivables sold are not reflected on the Condensed Consolidated Balance Sheets of Duke Energy Ohio and Duke Energy Indiana. See Note 12 for further information. These receivables for unbilled revenues are shown in the table below. (in millions) September 30, 2018 December 31, 2017 Duke Energy Ohio $ 68 $ 104 Duke Energy Indiana 121 132

Common Stock

Common Stock	9 Months Ended
	Sep. 30, 2018
Equity [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 stock, 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 shares outstanding to the diluted weighted average number of common shares outstanding. Three Months Ended September 30, Nine Months Ended September 30, (in millions, except per-share amounts) 2018 2017 2018 2017 Income from continuing operations attributable to Duke Energy common stockholders excluding impact of participating securities $ 1,077 $ 954 $ 2,199 $ 2,356 Weighted average shares outstanding – basic 713 700 705 700 Equity Forwards 1 — 1 — Weighted average shares outstanding – diluted 714 700 706 700 Earnings per share from continuing operations attributable to Duke Energy common stockholders Basic $ 1.51 $ 1.36 $ 3.12 $ 3.37 Diluted $ 1.51 $ 1.36 $ 3.11 $ 3.37 Potentially dilutive items excluded from the calculation (a) 2 2 2 2 Dividends declared per common share $ 0.9275 $ 0.89 $ 2.7075 $ 2.60 (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 Issuance 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 (ATM) 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 any of the Agents, shares of common stock through September 23, 2019. In June 2018, Duke Energy marketed two separate tranches, each for 1.3 million shares, of common stock. The first tranche was marketed with Wells Fargo Bank at an initial forward price of $72.02 per share and the second tranche was marketed with Citibank at an initial forward price of $78.71 per share through equity forward transactions under the ATM program. The Equity Forwards require Duke Energy to either physically settle the transactions by issuing 2.6 million shares in exchange for net proceeds at the then-applicable forward sale price specified by the agreements or net settle in whole or in part through the delivery or receipt of cash or shares. The settlement alternative is at Duke Energy's election. Separately, in March 2018, Duke Energy marketed an equity offering of 21.3 million shares of common stock through an Underwriting Agreement with Credit Suisse Securities (USA) LLC, J.P. Morgan Securities LLC, Barclays Capital Inc. and Goldman Sachs & Co. LLC, as representatives of several underwriters, Credit Suisse Capital LLC and J.P. Morgan Securities LLC as Forward Sellers, and Credit Suisse Capital LLC and JPMorgan Chase National Bank Associate, acting as forward purchasers. In connection with the offering, Duke Energy entered into equity forward sale agreements with Credit Suisse Securities (USA) LLC as Agent for Credit Suisse Capital LLC and J.P. Morgan Chase Bank, National Association. The sale price was $75 per share less certain net adjustments for an initial forward price of $74.07 per share. The Equity Forwards require Duke Energy to either physically settle the transactions by issuing 21.3 million shares in exchange for net proceeds at the then-applicable forward sale price specified by the agreements, or net settle in whole or in part through the delivery or receipt of cash or shares. The settlement alternative is at Duke Energy's election. In June 2018, Duke Energy physically settled one-half of the equity forwards by delivering approximately 10.6 million shares of common stock in exchange for net cash proceeds of approximately $781 million . For contracts that have not been settled, no amounts have or will be recorded in Duke Energy's Condensed Consolidated Financial Statements with respect to the equity or ATM offerings until settlements of the Equity Forwards occur, which is expected by December 31, 2018. If Duke Energy had elected to net share settle these contracts as of September 30, 2018, Duke Energy would have been required to deliver 1.1 million shares. The initial forward sale price will be subject to adjustment on a daily basis based on a floating interest rate factor and will decrease by other fixed amounts specified in the relevant forward sale agreement. Until settlement of the Equity Forwards, earnings per share dilution resulting from the agreements, if any, will be determined under the treasury stock method. Share dilution occurs when the average market price of Duke Energy's stock is higher than the average forward sales price. For the nine months ended September 30, 2018 , Duke Energy has issued 1.7 million shares through its Dividend Reinvestment Program (DRIP) with an increase in additional paid-in capital of approximately $134 million

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	STOCK-BASED COMPENSATION Stock-based compensation awarded to employees or outside directors is measured at the service inception date or grant date. The fair value of the award is expensed or capitalized over the requisite service period. For awards with performance conditions, the probability of vesting is assessed at each reporting period and compensation cost is adjusted based upon that assessment. The following table presents information related to Duke Energy's stock–based compensation. Three Months Ended Nine Months Ended September 30, September 30, (in millions) 2018 2017 2018 2017 Restricted stock unit awards $ 10 $ 10 $ 32 $ 30 Performance awards 13 7 27 20 Pretax stock-based compensation cost $ 23 $ 17 $ 59 $ 50 Stock-based compensation cost capitalized $ 1 $ 1 $ 3 $ 2 Stock-based compensation expense $ 22 $ 16 $ 56 $ 48 Tax benefit associated with stock-based compensation expense $ 5 $ 6 $ 13 $ 18

Employee Benefit Plans

Employee Benefit Plans	9 Months Ended
	Sep. 30, 2018
Retirement Benefits [Abstract]
Employee Benefit Plans	EMPLOYEE BENEFIT PLANS DEFINED BENEFIT RETIREMENT PLANS Duke Energy maintains, and the Subsidiary Registrants participate in, qualified and non-qualified, non-contributory defined benefit retirement plans. 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 presents contributions made by the Duke Energy Registrants to their qualified defined benefit pension plans during the nine months ended September 30, 2018 . Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Indiana Contributions $ 141 $ 46 $ 45 $ 25 $ 20 $ 8 Duke Energy and Duke Energy Ohio made contributions of $8 million and $4 million , respectively, to their qualified defined benefit pension plans during the nine months ended September 30, 2017 . Duke Energy uses a December 31 measurement date for its defined benefit retirement plan assets and obligations. Components of Net Periodic Benefit Costs The tables below present total net periodic benefit costs prior to capitalization of amounts reflected as Net property, plant and equipment on the Condensed Consolidated Balance Sheets. Only the service cost component of net periodic benefit costs is eligible to be capitalized. The remaining non-capitalized portions of net periodic benefit costs are classified as either: (1) service cost, which is recorded in Operations, maintenance and other on the Condensed Consolidated Statements of Operations; or as (2) components of non-service cost, which is recorded in Other income and expenses, net on the Condensed Consolidated Statements of Operations. See Note 1 for further information on impacts of the retirement benefits accounting standard adopted by Duke Energy on January 1, 2018. Pension and other post-retirement benefit costs presented in the tables below for the Subsidiary Registrants are amounts allocated from Duke Energy for the employees of the respective Subsidiary Registrants. The Condensed Consolidated Statements of Operations of the Subsidiary Registrants also include allocated net periodic benefit costs for their proportionate share of pension and post-retirement benefit costs related to employees of the Duke Energy shared services affiliate. However, in the tables below these amounts are only presented in the Duke Energy column. For additional information on the corporate governance and shared service expenses allocated from the Duke Energy shared service affiliate, see Note 8 . QUALIFIED PENSION PLANS The following tables include the components of net periodic pension costs for qualified pension plans. Three Months Ended September 30, 2018 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Service cost $ 47 $ 15 $ 13 $ 7 $ 5 $ 2 $ 2 $ 2 Interest cost on projected benefit obligation 74 18 24 10 13 4 6 3 Expected return on plan assets (140 ) (37 ) (45 ) (21 ) (23 ) (7 ) (10 ) (6 ) Amortization of actuarial loss 33 7 11 6 6 1 2 3 Amortization of prior service credit (8 ) (2 ) (1 ) — — — — (3 ) Net periodic pension costs $ 6 $ 1 $ 2 $ 2 $ 1 $ — $ — $ (1 ) Three Months Ended September 30, 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 $ 40 $ 12 $ 12 $ 6 $ 5 $ 1 $ 2 $ 3 Interest cost on projected benefit obligation 82 20 25 12 13 4 7 3 Expected return on plan assets (136 ) (35 ) (43 ) (21 ) (21 ) (7 ) (11 ) (6 ) Amortization of actuarial loss 36 8 14 6 7 1 3 3 Amortization of prior service credit (6 ) (2 ) (1 ) — — — — (1 ) Other 2 — 1 — — — — — Net periodic pension costs $ 18 $ 3 $ 8 $ 3 $ 4 $ (1 ) $ 1 $ 2 Nine Months Ended September 30, 2018 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Service cost $ 137 $ 45 $ 39 $ 22 $ 16 $ 4 $ 7 $ 6 Interest cost on projected benefit obligation 224 54 70 31 38 13 18 9 Expected return on plan assets (420 ) (111 ) (133 ) (63 ) (69 ) (21 ) (31 ) (18 ) Amortization of actuarial loss 99 21 33 16 18 3 6 9 Amortization of prior service credit (24 ) (6 ) (3 ) (1 ) (1 ) — — (9 ) Net periodic pension costs $ 16 $ 3 $ 6 $ 5 $ 2 $ (1 ) $ — $ (3 ) Nine Months Ended September 30, 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 $ 120 $ 36 $ 36 $ 18 $ 15 $ 3 $ 6 $ 9 Interest cost on projected benefit obligation 246 60 75 36 39 14 21 9 Expected return on plan assets (408 ) (106 ) (129 ) (63 ) (63 ) (21 ) (33 ) (18 ) Amortization of actuarial loss 108 24 42 18 21 3 9 9 Amortization of prior service credit (18 ) (6 ) (3 ) — — — — (3 ) Other 6 — 3 1 — — — 1 Net periodic pension costs $ 54 $ 8 $ 24 $ 10 $ 12 $ (1 ) $ 3 $ 7 NON-QUALIFIED PENSION PLANS The following tables include the components of net periodic pension costs for non-qualified pension plans for registrants with non-qualified pension costs. Three Months Ended September 30, 2018 Duke Duke Duke Duke Energy Progress Energy Energy (in millions) Energy Carolinas Energy Progress Florida Interest cost on projected benefit obligation $ 3 $ — $ 1 $ — $ — Amortization of actuarial loss 2 — — — — Net periodic pension costs $ 5 $ — $ 1 $ — $ — Three Months Ended September 30, 2017 Duke Duke Duke Duke Energy Progress Energy Energy (in millions) Energy Carolinas Energy Progress Florida Interest cost on projected benefit obligation $ 4 $ — $ 1 $ 1 $ 1 Amortization of actuarial loss 2 — 1 — — Net periodic pension costs $ 6 $ — $ 2 $ 1 $ 1 Nine Months Ended September 30, 2018 Duke Duke Duke Duke Energy Progress Energy Energy (in millions) Energy Carolinas Energy Progress Florida Service cost $ 1 $ 1 $ — $ — $ — Interest cost on projected benefit obligation 9 — 3 1 1 Amortization of actuarial loss 6 — — — — Amortization of prior service (credit) cost (1 ) — 1 — — Net periodic pension costs $ 15 $ 1 $ 4 $ 1 $ 1 Nine Months Ended September 30, 2017 Duke Duke Duke Duke Energy Progress Energy Energy (in millions) Energy Carolinas Energy Progress Florida Interest cost on projected benefit obligation $ 10 $ 1 $ 3 $ 2 $ 2 Amortization of actuarial loss 6 — 3 — — Net periodic pension costs $ 16 $ 1 $ 6 $ 2 $ 2 OTHER POST-RETIREMENT BENEFIT PLANS Duke Energy provides, and the Subsidiary Registrants participate in, certain health care and life insurance benefits for retired employees on a contributory and non-contributory basis. The following tables include the components of net periodic other post-retirement benefit costs. Three Months Ended September 30, 2018 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 $ — $ — $ — $ — $ — $ — $ — Interest cost on accumulated post-retirement benefit obligation 7 2 3 2 1 — 1 — Expected return on plan assets (4 ) (2 ) — — — — — — Amortization of actuarial loss 2 1 — — — — 1 — Amortization of prior service credit (5 ) (1 ) (2 ) — (1 ) — — — Net periodic other post-retirement benefit costs $ 2 $ — $ 1 $ 2 $ — $ — $ 2 $ — Three Months Ended September 30, 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 $ 1 $ — $ — $ — $ — $ — $ — $ — Interest cost on accumulated post-retirement benefit obligation 9 2 4 2 2 — 1 — Expected return on plan assets (3 ) (2 ) — — — — — — Amortization of actuarial loss 2 — 5 3 2 — — — Amortization of prior service credit (29 ) (2 ) (21 ) (14 ) (8 ) — — — Net periodic other post-retirement benefit costs $ (20 ) $ (2 ) $ (12 ) $ (9 ) $ (4 ) $ — $ 1 $ — Nine Months Ended September 30, 2018 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Service cost $ 5 $ 1 $ — $ — $ — $ — $ — $ — Interest cost on accumulated post-retirement benefit obligation 21 5 9 5 4 1 3 — Expected return on plan assets (10 ) (6 ) — — — — — — Amortization of actuarial loss 5 2 1 — — — 3 — Amortization of prior service credit (15 ) (3 ) (6 ) — (4 ) — — (1 ) Net periodic other post-retirement benefit costs $ 6 $ (1 ) $ 4 $ 5 $ — $ 1 $ 6 $ (1 ) Nine Months Ended September 30, 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 $ 3 $ — $ — $ — $ — $ — $ — $ — Interest cost on accumulated post-retirement benefit obligation 27 6 11 6 6 — 1 — Expected return on plan assets (10 ) (6 ) — — — — — — Amortization of actuarial loss (gain) 6 (2 ) 15 9 6 (1 ) — — Amortization of prior service credit (87 ) (6 ) (63 ) (41 ) (23 ) — — — Net periodic other post-retirement benefit costs $ (61 ) $ (8 ) $ (37 ) $ (26 ) $ (11 ) $ (1 ) $ 1 $ — EMPLOYEE SAVINGS PLAN Duke Energy sponsors, and the Subsidiary Registrants participate in, an employee savings plan that covers substantially all employees. The following table includes employer 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 Three Months Ended September 30, 2018 $ 49 $ 15 $ 13 $ 9 $ 4 $ — $ 3 $ 4 2017 43 14 12 9 4 1 2 2 Nine Months Ended September 30, 2018 $ 167 $ 53 $ 45 $ 31 $ 14 $ 2 $ 8 $ 10 2017 147 49 42 30 13 3 7 5

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2018
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 lowered the corporate federal income tax rate from 35 to 21 percent, limits interest deductions outside of regulated utility operations, requires the normalization of excess deferred taxes associated with property under ARAM as a prerequisite to qualifying for accelerated depreciation and repealed the federal manufacturing deduction. The Tax Act also repealed the corporate alternative minimum tax (AMT) and stipulates a refund of 50 percent of remaining AMT credit carryforwards (to the extent the credits exceed regular tax for the year) for tax years 2018, 2019 and 2020 with all remaining AMT credits to be refunded in tax year 2021. During the three months ended September 30, 2018, the company reclassified $573 million which is 50 percent of the remaining estimated AMT credit carryforwards from noncurrent deferred tax liability to a current federal income tax receivable as a result of the Tax Act. The company reclassified the estimated AMT credit carryforwards during the three months ended September 30, 2018, since the company expects to receive it as a refund from the IRS in the three months ended September 30, 2019, based on the expected filing of Duke Energy's 2018 income tax return in the second quarter of 2019. At this time AMT credits, which are among the certain tax credits treated as refundable under the Tax Act, are subject to sequestration. In the first quarter of 2018, the company revised the December 31, 2017, estimate of the income tax effects of the Tax Act and recorded a $76 million valuation allowance against these AMT credits based on additional interpretative guidance from the Internal Revenue Service related to the Tax Act. See Note 22 to the Consolidated Financial Statements in the Annual Report on Form 10-K/A for the year ended December 31, 2017 , for information on the U.S. Securities and Exchange Commission staff's guidance on accounting for the Tax Act (Staff Accounting Bulletin No. 118 (SAB 118), Income Tax Accounting Implications of the Tax Cuts and Jobs Act). During the three months ended September 30, 2018 , the company revised the December 31, 2017 estimate of the income tax effects of the Tax Act, in accordance with SAB 118, by recording a $3 million benefit for the remeasurement of its deferred tax assets and deferred tax liabilities primarily related to the guidance on bonus depreciation issued by the Internal Revenue Service in August of 2018 affecting the computation of the company's 2017 Federal income tax liability. 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. For Duke Energy's regulated operations, where the reduction is expected to be returned to customers in future rates, the remeasurement has been deferred as a regulatory liability. For the three months ended September 30, 2018, Duke Energy recorded a regulatory liability of $57 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. For the nine months ended September 30, 2018, the company has revised the December 31, 2017, estimates of the income tax effects of the Tax Act, in accordance with SAB 118, by recording an expense of $73 million . Additional tax returns will be filed in the quarter ending December 31, 2018, and Duke Energy expects to make refinements of estimates recorded in the three months ending September 30, 2018. These refinements are not expected to be material to the financial statements. Duke Energy anticipates finalizing and recording any resulting adjustments within the measurement period allowed, which will be no later than the quarter ending December 31, 2018. EFFECTIVE TAX RATES The effective tax rates from continuing operations for each of the Duke Energy Registrants are included in the following table. Three Months Ended Nine Months Ended September 30, September 30, 2018 2017 2018 2017 Duke Energy 13.7 % 27.6 % 17.0 % 30.4 % Duke Energy Carolinas 22.6 % 32.9 % 22.3 % 34.1 % Progress Energy 18.8 % 29.1 % 17.0 % 31.9 % Duke Energy Progress 20.6 % 31.7 % 18.4 % 32.4 % Duke Energy Florida 15.0 % 34.8 % 16.3 % 36.1 % Duke Energy Ohio 16.0 % 33.3 % 16.0 % 34.4 % Duke Energy Indiana 22.7 % 38.3 % 24.7 % 39.0 % Piedmont 34.4 % 47.6 % 20.6 % 36.1 % The decrease in the effective tax rate (ETR) for Duke Energy and the Subsidiary Registrants for the three months ended September 30, 2018 , is primarily due to the lower statutory federal corporate tax rate under the Tax Act. The decrease in the ETR for Duke Energy and the Subsidiary Registrants for the nine months ended September 30, 2018 , is primarily due to the lower statutory federal corporate tax rate under the Tax Act and the amortization of federal and state excess deferred taxes, partially offset by a valuation allowance against AMT credits discussed above. The decrease in the ETR for Duke Energy Carolinas for the three and nine months ended September 30, 2018 , is primarily due to the lower statutory federal corporate tax rate under the Tax Act and amortization of state excess deferred taxes partially offset by favorable tax return true ups in the prior year. The decrease in the ETR for Progress Energy for the three and nine months ended September 30, 2018 , is primarily due to the lower statutory federal corporate tax rate under the Tax Act and the amortization of federal and state excess deferred taxes. The decrease in the ETR for Duke Energy Progress for the three and nine months ended September 30, 2018 , is primarily due to the lower statutory federal corporate tax rate under the Tax Act and amortization of state excess deferred taxes. The decrease in the ETR for Duke Energy Florida for the three and nine months ended September 30, 2018 , is primarily due to the lower statutory federal corporate tax rate under the Tax Act and the amortization of federal excess deferred taxes. The decrease in the ETR for Duke Energy Ohio for the three and nine months ended September 30, 2018 , is primarily due to the lower statutory federal corporate tax rate under the Tax Act and the amortization of federal excess deferred taxes. The decrease in the ETR for Duke Energy Indiana for the three and nine months ended September 30, 2018 , is primarily due to the lower statutory federal corporate tax rate under the Tax Act. The decrease in the ETR for Piedmont for the three months ended September 30, 2018 , is primarily due to the lower statutory federal corporate tax rate under the Tax Act partially offset by favorable research credits in relation to pretax losses. The decrease in the ETR for Piedmont for the nine months ended September 30, 2018 , is primarily due to the lower statutory federal corporate tax rate under the Tax Act.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2018
Subsequent Events [Abstract]
Subsequent Events	SUBSEQUENT EVENTS For information on subsequent events related to regulatory matters and commitments and contingencies see Notes 3 and 4, respectively. On October 10, 2018, Hurricane Michael made landfall on Florida's Panhandle as a Category 4 hurricane, the most powerful storm to hit the Florida Panhandle in recorded history. The storm caused significant damage and more than a million power outages within the service territories of Duke Energy Florida, Duke Energy Carolinas and Duke Energy Progress. Duke Energy has not completed the final accumulation of total estimated storm restoration costs incurred; however, the preliminary estimate is approximately $235 million of operation and maintenance expenses and approximately $185 million in capital costs. Given the magnitude of the storm, Duke Energy Carolinas and Duke Energy Progress intend to request approval to defer the incremental costs incurred to a regulatory asset for recovery in the next base rate cases, and Duke Energy Florida will recover these storm costs consistent with the provisions in its 2017 Second Revised and Restated Settlement Agreement.

Organization and Basis of Pre_2

Organization and Basis of Presentation (Policy)	9 Months Ended
	Sep. 30, 2018
Policy Text Block [Line Items]
Basis of Presentation	BASIS OF PRESENTATION These Condensed Consolidated Financial Statements have been prepared in accordance with generally accepted accounting principles in the U.S. (GAAP) for interim financial information and with the instructions to Form 10-Q and Regulation S-X. Accordingly, these Condensed Consolidated Financial Statements do not include all information and notes required by GAAP for annual financial statements. Since the interim Condensed Consolidated Financial Statements and Notes do not include all information and notes required by GAAP in the U.S. for annual financial statements, the Condensed Consolidated Financial Statements and other information included in this quarterly report should be read in conjunction with the Consolidated Financial Statements and Notes in the Duke Energy Registrants’ combined Annual Report on Form 10-K/A for the year ended December 31, 2017 . The information in these combined notes relates to each of the Duke Energy Registrants as noted in the Index to Combined Notes to Condensed Consolidated Financial Statements. However, none of the registrants make any representations as to information related solely to Duke Energy or the subsidiaries of Duke Energy other than itself. These Condensed Consolidated Financial Statements, in the opinion of the respective companies’ management, reflect all normal recurring adjustments necessary to fairly present the financial position and results of operations of each of the Duke Energy Registrants. Amounts reported in Duke Energy’s interim Condensed Consolidated Statements of Operations and each of the Subsidiary Registrants’ interim Condensed Consolidated Statements of Operations and Comprehensive Income are not necessarily indicative of amounts expected for the respective annual periods due to effects of seasonal temperature variations on energy consumption, regulatory rulings, timing of maintenance on electric generating units, changes in mark-to-market valuations, changing commodity prices and other factors.
Consolidation	These Condensed 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 Condensed Consolidated Financial Statements also reflect the Duke Energy Registrants’ proportionate share of certain jointly owned generation and transmission facilities.
Use of Estimates	In preparing financial statements that conform to GAAP, management 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.
Cash, Cash Equivalents, and Restricted Cash	CASH, CASH EQUIVALENTS AND RESTRICTED CASH Duke Energy, Progress Energy and Duke Energy Florida have restricted cash balances related primarily to collateral assets, escrow deposits and variable interest entities (VIEs). See Note 12 for additional information. Restricted cash amounts are included in Other within Current Assets and Other Noncurrent Assets.
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.
New Accounting Standards	NEW ACCOUNTING STANDARDS The new accounting standards adopted for 2018 and 2017 had no material impact on the presentation or results of operations, cash flows or financial position of the Duke Energy Registrants. While immaterial, adoption of the following accounting standards had the most significant impact on the Duke Energy results of operations, cash flows and financial position for the nine months ended September 30, 2018 . Revenue from Contracts with Customers. In May 2014, the Financial Accounting Standards Board (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 expected in exchange for those goods or services. The amendments also required 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. The majority of Duke Energy’s revenue is in scope of the new guidance. Other revenue arrangements, such as alternative revenue programs and certain purchase power agreements (PPAs) and lighting agreements accounted for as leases, are excluded from the scope of this guidance and, therefore, are accounted for and evaluated for separate presentation and disclosure under other relevant accounting guidance. Duke Energy elected the modified retrospective method of adoption effective January 1, 2018. Under the modified retrospective method of adoption, prior year reported results are not restated. Adoption of this standard did not result in a material change in the timing or pattern of revenue recognition and a cumulative-effect adjustment was not recorded at January 1, 2018. Duke Energy utilized certain practical expedients including applying this guidance to open contracts at the date of adoption, expensing costs to obtain a contract where the amortization period of the asset would have been one year or less, ignoring the effects of a significant financing when the period between transfer of the good or service and payment is one year or less and recognizing revenues for certain contracts under the invoice practical expedient, which allows revenue recognition to be consistent with invoiced amounts (including unbilled estimates) provided certain criteria are met, including consideration of whether the invoiced amounts reasonably represent the value provided to customers. In preparation for adoption, Duke Energy identified material revenue streams and reviewed representative contracts and tariffs, including those associated with certain long-term customer contracts such as wholesale contracts, PPAs and other customer arrangements. Duke Energy also monitored the activities of the power and utilities industry revenue recognition task force and has reviewed published positions on specific industry issues to evaluate the impact, if any, on Duke Energy’s specific contracts and conclusions. Duke Energy applied the available practical expedient to portfolios of tariffs and contracts with similar characteristics. The vast majority of sales, including energy provided to retail customers, are from tariff offerings that provide natural gas or electricity without a defined contractual term ("at-will"). In most circumstances, revenue from contracts with customers is equivalent to the electricity or natural gas supplied and billed in that period (including unbilled estimates). As such, adoption of the new rules did not result in a shift in the timing or pattern of revenue recognition for such sales. While there have been changes to the captions and descriptions of revenues in Duke Energy’s financial statements, the most significant impact as a result of adopting the standard are additional disclosures around the nature, amount, timing and uncertainty of revenues and cash flows arising from contracts with customers. See Note 13 for further information. Financial Instruments Classification and Measurement. On January 1, 2018, Duke Energy adopted FASB guidance, which revised the classification and measurement of certain financial instruments. The adopted guidance changes the presentation of realized and unrealized gains and losses in certain equity securities that were previously recorded in accumulated other comprehensive income (AOCI). These gains and losses are now recorded in net income. 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. This guidance had a minimal impact on the Duke Energy Registrant's Condensed Consolidated Statements of Operations and Comprehensive Income as changes in the fair value of most of the Duke Energy Registrants' equity securities are deferred as regulatory assets or liabilities pursuant to accounting guidance for regulated operations. The resulting adjustment of unrealized gains and losses in AOCI to retained earnings was immaterial. The primary impact to Duke Energy as a result of implementing this guidance is adding disclosure requirements to present separately the financial assets and financial liabilities by measurement category and form of financial asset. See Notes 10 and 11 for further information. 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 Condensed Consolidated Statements of Cash Flows. Under the updated guidance, restricted cash and restricted cash equivalents are included within beginning-of-period and end-of-period cash and cash equivalents on the Condensed Consolidated Statements of Cash Flows. Duke Energy adopted this guidance on January 1, 2018. The guidance has been applied using a retrospective transition method to each period presented. The adoption by Duke Energy of the revised guidance resulted in a change to the amount of Cash, cash equivalents and restricted cash explained when reconciling the beginning-of-period and end-of-period total amounts shown on the Condensed Consolidated Statements of Cash Flows. In addition, a reconciliation has been provided of Cash, cash equivalents and restricted cash reported within the Condensed Consolidated Balance Sheets that sums to the total of the same such amounts in the Condensed Consolidated Statements of Cash Flows. Prior to adoption, the Duke Energy Registrants reflected changes in noncurrent restricted cash within Cash Flows from Investing Activities and changes in current restricted cash within Cash Flows from Operating Activities on the Condensed Consolidated Statements of Cash Flows. In August 2016, the FASB issued accounting guidance addressing diversity in practice for eight separate cash flow issues. The guidance requires entities to classify distributions received from equity method investees using either the cumulative earnings approach or the nature of the distribution approach. Duke Energy adopted this guidance on January 1, 2018, and elected the nature of distribution approach. This approach requires all distributions received to be categorized based on legal documentation describing the nature of the activities generating the distribution. Cash inflows resulting in a return on investment (surplus) will be reflected in Cash Flows from Operating Activities on the Condensed Consolidated Statements of Cash Flows, whereas cash inflows resulting in a return of investment (capital) will be reflected in Cash Flows from Investing Activities on the Condensed Consolidated Statements of Cash Flows. The guidance has been applied using the retrospective transition method to each period presented. There are no changes to the Condensed Consolidated Statements of Cash Flows for the periods presented as a result of this accounting change. Retirement Benefits. In March 2017, the FASB issued revised accounting guidance for the presentation of net periodic costs related to benefit plans. Previous guidance required the aggregation of all the components of net periodic costs on the Condensed Consolidated Statement of Operations and did not require the disclosure of the location of net periodic costs on the Condensed Consolidated Statement of Operations. Under the amended guidance, the service cost component of net periodic costs is included within Operating Income within the same line as other compensation expenses. All other components of net periodic costs are 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 previous guidance, which permitted all components of net periodic costs to be eligible for capitalization. Duke Energy adopted this guidance on January 1, 2018. Under previous guidance, Duke Energy presented the total non-capitalized net periodic costs within Operation, maintenance and other on the Condensed Consolidated Statements of Operations. The adoption of this guidance resulted 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 utilized the practical expedient for retrospective presentation. The change in components of net periodic costs eligible for capitalization is applicable prospectively. Since Duke Energy’s service cost component is greater than the total net periodic costs, the change results in increased capitalization of net periodic costs, higher Operation, maintenance and other and higher Other income and expenses. The resulting prospective impact to Duke Energy is an immaterial increase in Net Income. See Note 15 for further information. For Duke Energy, the retrospective change resulted in higher Operation, maintenance and other and higher Other income and expenses, net, of $156 million , $131 million and $96 million for the years ended December 31, 2017, 2016 and 2015, respectively. There was no change to Net Income for these prior periods. The following new Accounting Standards Updates (ASUs) have been issued, but have not yet been adopted by Duke Energy, as of September 30, 2018 . 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 will be applied using a modified retrospective approach. Upon adoption, agreements considered leases for the use of certain aircraft, space on communication towers, industrial equipment, fleet vehicles, fuel transportation (barges and railcars), land and office space will be recognized on the balance sheet. Duke Energy expects to elect certain of the following practical expedients upon adoption: Practical Expedient Description Election Package of transition practical expedients (for leases commenced prior to adoption date and must be adopted as a package) Do not need to 1) reassess whether any expired or existing contracts are/or contain leases, 2) reassess the lease classification for any expired or existing leases and 3) reassess initial direct costs for any existing leases. Duke Energy plans to elect this practical expedient. Short-term lease expedient (elect by class of underlying asset) Elect as an accounting policy to not apply the recognition requirements to short-term leases by asset class. Duke Energy plans to elect this practical expedient for all asset classes. Lease and non-lease components (elect by class of underlying asset) Elect as an accounting policy to not separate non-lease components from lease components and instead account for each lease and associated non-lease component as a single lease component by asset class. Duke Energy is currently assessing the election of this practical expedient. Hindsight expedient (when determining lease term) Elect to use hindsight to determine the lease term. Duke Energy plans to elect this practical expedient. Existing and expired land easements not previously accounted for as leases Elect to not evaluate existing or expired easements under the new guidance and carry forward current accounting treatment. Duke Energy plans to elect this practical expedient. Comparative reporting requirements for initial adoption Elect to apply transition requirements at adoption date, recognize cumulative effect adjustment to retained earnings in period of adoption and not apply ASC 842 to comparative periods, including disclosures. Duke Energy plans to elect this practical expedient. Lessor expedient (elect by class of underlying asset) Elect as an accounting policy to aggregate non-lease components with the related lease component when specified conditions are met by asset class. Account for the combined component based on its predominant characteristic (revenue or operating lease). Duke Energy is currently assessing the election of this practical expedient. Duke Energy is currently evaluating the financial statement impact of adopting this standard and is continuing to monitor industry implementation issues, including leases within asset retirement obligations, pipeline laterals and renewable energy PPAs. In arrangements where Duke Energy is the lessee, it expects an increase in assets and liabilities on its balance sheet along with the addition of required disclosures of key lease information. However, the ultimate lessee impact of the new standard has not yet been determined. Duke Energy does not expect a material change to its financial statements from adoption of the new standard for contracts where it is the lessor. 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 is implementing a third-party software tool to help with the adoption and ongoing accounting under the new standard.
Environmental Costs	Costs are typically expensed as Operation, maintenance and other on the Condensed Consolidated Statements of Operations unless regulatory recovery of the costs is deemed probable. Liabilities are recorded when losses become probable and are reasonably estimable.
Derivatives	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. 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 on the Duke Energy Registrant's Condensed Consolidated Statements of Operations and Comprehensive Income.
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 securities within the Investment Trusts are considered OTTIs and are recognized immediately and deferred to regulatory accounts where appropriate. 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. 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. If an OTTI exists, the unrealized credit loss is included in earnings.
Revenue from Contract with Customer	certain excise taxes and franchise fees 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 as part of revenues. Duke Energy elects to account for all other taxes net of revenues. Duke Energy recognizes revenue consistent with amounts billed under tariff offerings or at contractually agreed upon rates based on actual physical delivery of electric or natural gas service, including estimated volumes delivered when billings have not yet occurred. UNBILLED REVENUE 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. 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, CRC and accounts for the transfers of receivables as sales. Accordingly, the receivables sold are not reflected on the Condensed Consolidated Balance Sheets of Duke Energy Ohio and Duke Energy Indiana.
Earnings Per Share	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 stock, such as stock options and equity forward sale agreements, were exercised or settled.
Stock-based Compensation	Stock-based compensation awarded to employees or outside directors is measured at the service inception date or grant date. The fair value of the award is expensed or capitalized over the requisite service period.

Organization and Basis of Pre_3

Organization and Basis of Presentation (Tables)	9 Months Ended
	Sep. 30, 2018
Organization And Basis Of Presentation [Line Items]
Schedule of Cash, Cash Equivalents and Restricted Cash	The following table presents the components of cash, cash equivalents and restricted cash included in the Condensed Consolidated Balance Sheets. September 30, 2018 December 31, 2017 Duke Duke Duke Progress Energy Duke Progress Energy Energy Energy Florida Energy Energy Florida Current Assets Cash and cash equivalents $ 303 $ 43 $ 20 $ 358 $ 40 $ 13 Other 139 14 14 138 40 40 Other Noncurrent Assets Other 7 6 — 9 7 — Total cash, cash equivalents and restricted cash $ 449 $ 63 $ 34 $ 505 $ 87 $ 53
Schedule of Utility Inventory	The components of inventory are presented in the tables below. September 30, 2018 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 $ 2,283 $ 758 $ 1,071 $ 748 $ 323 $ 87 $ 294 $ 1 Coal 515 176 187 99 88 14 138 — Natural gas, oil and other fuel 342 42 215 109 106 34 2 50 Total inventory $ 3,140 $ 976 $ 1,473 $ 956 $ 517 $ 135 $ 434 $ 51 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 fuel 354 35 219 104 115 34 2 64 Total inventory $ 3,250 $ 971 $ 1,592 $ 1,017 $ 574 $ 133 $ 450 $ 66
Schedule of Excise Taxes	Excise taxes accounted for on a gross basis within both Operating Revenues and Property and other taxes on the Condensed Consolidated Statements of Operations were as follows. Three Months Ended September 30, Nine Months Ended September 30, (in millions) 2018 2017 2018 2017 Duke Energy $ 114 $ 107 $ 308 $ 289 Duke Energy Carolinas 10 9 27 27 Progress Energy 71 67 181 168 Duke Energy Progress 5 5 15 14 Duke Energy Florida 66 62 166 154 Duke Energy Ohio 26 24 81 75 Duke Energy Indiana 6 6 17 16 Piedmont 1 1 2 3
Schedule of New Accounting Pronouncements	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 will be applied using a modified retrospective approach. Upon adoption, agreements considered leases for the use of certain aircraft, space on communication towers, industrial equipment, fleet vehicles, fuel transportation (barges and railcars), land and office space will be recognized on the balance sheet. Duke Energy expects to elect certain of the following practical expedients upon adoption: Practical Expedient Description Election Package of transition practical expedients (for leases commenced prior to adoption date and must be adopted as a package) Do not need to 1) reassess whether any expired or existing contracts are/or contain leases, 2) reassess the lease classification for any expired or existing leases and 3) reassess initial direct costs for any existing leases. Duke Energy plans to elect this practical expedient. Short-term lease expedient (elect by class of underlying asset) Elect as an accounting policy to not apply the recognition requirements to short-term leases by asset class. Duke Energy plans to elect this practical expedient for all asset classes. Lease and non-lease components (elect by class of underlying asset) Elect as an accounting policy to not separate non-lease components from lease components and instead account for each lease and associated non-lease component as a single lease component by asset class. Duke Energy is currently assessing the election of this practical expedient. Hindsight expedient (when determining lease term) Elect to use hindsight to determine the lease term. Duke Energy plans to elect this practical expedient. Existing and expired land easements not previously accounted for as leases Elect to not evaluate existing or expired easements under the new guidance and carry forward current accounting treatment. Duke Energy plans to elect this practical expedient. Comparative reporting requirements for initial adoption Elect to apply transition requirements at adoption date, recognize cumulative effect adjustment to retained earnings in period of adoption and not apply ASC 842 to comparative periods, including disclosures. Duke Energy plans to elect this practical expedient. Lessor expedient (elect by class of underlying asset) Elect as an accounting policy to aggregate non-lease components with the related lease component when specified conditions are met by asset class. Account for the combined component based on its predominant characteristic (revenue or operating lease). Duke Energy is currently assessing the election of this practical expedient.

Business Segments (Tables)

Business Segments (Tables)	9 Months Ended
	Sep. 30, 2018
Segment Reporting Information [Line Items]
Business Segment Data	Business segment information is presented in the following tables. Segment assets presented exclude intercompany assets. Three Months Ended September 30, 2018 Electric Gas Total Utilities and Utilities and Commercial Reportable (in millions) Infrastructure Infrastructure Renewables Segments Other Eliminations Consolidated Unaffiliated revenues $ 6,253 $ 232 $ 127 $ 6,612 $ 16 $ — $ 6,628 Intersegment revenues 7 24 — 31 18 (49 ) — Total revenues $ 6,260 $ 256 $ 127 $ 6,643 $ 34 $ (49 ) $ 6,628 Segment income (loss) (a)(b)(c) $ 1,167 $ 17 $ (62 ) $ 1,122 $ (44 ) $ — $ 1,078 Add back noncontrolling interests (16 ) Income from discontinued operations, net of tax 4 Net income $ 1,066 Segment assets $ 123,847 $ 11,806 $ 4,212 $ 139,865 $ 3,115 $ 185 $ 143,165 Three Months Ended September 30, 2017 Electric Gas Total Utilities and Utilities and Commercial Reportable (in millions) Infrastructure Infrastructure Renewables Segments Other Eliminations Consolidated Unaffiliated revenues $ 6,122 $ 249 $ 95 $ 6,466 $ 16 $ — $ 6,482 Intersegment revenues 7 23 — 30 19 (49 ) — Total revenues $ 6,129 $ 272 $ 95 $ 6,496 $ 35 $ (49 ) $ 6,482 Segment income (loss) (b)(d)(e) $ 1,020 $ 19 $ (49 ) $ 990 $ (34 ) $ — $ 956 Add back noncontrolling interests 1 Loss from discontinued operations, net of tax (2 ) Net income $ 955 (a) All segments include adjustments to the December 31, 2017 estimate of the income tax effects of the Tax Act. See Note 17 for additional information. (b) Other includes costs to achieve the Piedmont acquisition. (c) Commercial Renewables includes an impairment charge related to goodwill. See Note 7 for additional information. (d) Electric Utilities and Infrastructure includes an impairment charge related to the unrecovered Levy Nuclear Project costs at Duke Energy Florida. (e) Commercial Renewables includes impairment charges related to certain wind projects. Nine Months Ended September 30, 2018 Electric Gas Total Utilities and Utilities and Commercial Reportable (in millions) Infrastructure Infrastructure Renewables Segments Other Eliminations Consolidated Unaffiliated revenues $ 16,783 $ 1,229 $ 347 $ 18,359 $ 47 $ — $ 18,406 Intersegment revenues 23 72 — 95 54 (149 ) — Total revenues $ 16,806 $ 1,301 $ 347 $ 18,454 $ 101 $ (149 ) $ 18,406 Segment income (loss) (a)(b)(c)(d)(e)(f) $ 2,492 $ 161 $ (4 ) $ 2,649 $ (446 ) $ — $ 2,203 Add back noncontrolling interests (12 ) Loss from discontinued operations, net of tax (1 ) Net income $ 2,190 Nine Months Ended September 30, 2017 Electric Gas Total Utilities and Utilities and Commercial Reportable (in millions) Infrastructure Infrastructure Renewables Segments Other Eliminations Consolidated Unaffiliated revenues $ 16,211 $ 1,175 $ 333 $ 17,719 $ 47 $ — $ 17,766 Intersegment revenues 23 68 — 91 56 (147 ) — Total revenues $ 16,234 $ 1,243 $ 333 $ 17,810 $ 103 $ (147 ) $ 17,766 Segment income (loss) (c)(g)(h) $ 2,384 $ 179 $ 2 $ 2,565 $ (205 ) $ — $ 2,360 Add back noncontrolling interests 5 Loss from discontinued operations, net of tax (4 ) Net income $ 2,361 (a) All segments include adjustments to the December 31, 2017 estimate of the income tax effects of the Tax Act. See Note 17 for additional information. (b) Electric Utilities and Infrastructure includes regulatory and legislative impairment charges related to rate case orders, settlements or other actions of regulators or legislative bodies. See Note 3 for additional information. (c) Other includes costs to achieve the Piedmont acquisition. (d) Gas Utilities and Infrastructure includes an impairment of the investment in Constitution Pipeline Company, LLC (Constitution). See Note 3 for additional information. (e) Other includes the loss on the sale of the retired Beckjord Generating Station (Beckjord) described below and a valuation allowance recorded against the alternative minimum tax credits subject to sequestration. See Note 17 for additional information on the valuation allowance. (f) Commercial Renewables includes an impairment charge related to goodwill. See Note 7 for additional information. (g) Electric Utilities and Infrastructure includes an impairment charge related to the unrecovered Levy Nuclear Project costs at Duke Energy Florida. (h) Commercial Renewables includes impairment charges related to certain wind projects.
Duke Energy Ohio [Member]
Segment Reporting Information [Line Items]
Business Segment Data	Three Months Ended September 30, 2018 Electric Gas Total Utilities and Utilities and Reportable (in millions) Infrastructure Infrastructure Segments Other Eliminations Consolidated Total revenues $ 373 $ 84 $ 457 $ 12 $ — $ 469 Segment income/Net income $ 85 $ 12 $ 97 $ 3 $ — $ 100 Segment assets $ 5,484 $ 2,775 $ 8,259 $ 39 $ (2 ) $ 8,296 Three Months Ended September 30, 2017 Electric Gas Total Utilities and Utilities and Reportable (in millions) Infrastructure Infrastructure Segments Other Consolidated Total revenues $ 371 $ 90 $ 461 $ 10 $ 471 Segment income (loss) $ 50 $ 14 $ 64 $ (8 ) $ 56 Loss from discontinued operations, net of tax (1 ) Net income $ 55 Nine Months Ended September 30, 2018 Electric Gas Total Utilities and Utilities and Reportable (in millions) Infrastructure Infrastructure Segments Other Consolidated Total revenues $ 1,055 $ 361 $ 1,416 $ 36 $ 1,452 Segment income (loss)/Net income (a) $ 157 $ 64 $ 221 $ (100 ) $ 121 Nine Months Ended September 30, 2017 Electric Gas Total Utilities and Utilities and Reportable (in millions) Infrastructure Infrastructure Segments Other Consolidated Total revenues $ 1,036 $ 360 $ 1,396 $ 30 $ 1,426 Segment income (loss) $ 96 $ 56 $ 152 $ (24 ) $ 128 Loss from discontinued operations, net of tax (1 ) Net income $ 127 (a) Other includes the loss on the sale of Beckjord.

Regulatory Matters (Tables)

Regulatory Matters (Tables)	9 Months Ended
	Sep. 30, 2018
Regulated Operations [Abstract]
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 Condensed Consolidated Balance Sheets as of September 30, 2018 , 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 $ 132 Progress Energy and Duke Energy Florida Crystal River Units 1 and 2 (b) 766 100 Duke Energy Indiana Gallagher Units 2 and 4 (c) 280 123 Total Duke Energy 1,631 $ 355 (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 2016 settlement of Edwardsport IGCC matters.

Commitments and Contingencies (

Commitments and Contingencies (Table)	9 Months Ended
	Sep. 30, 2018
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 $ 57 Duke Energy Carolinas 17 Duke Energy Ohio 30 Piedmont 2
Reserve, Environmental Cost [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 Condensed Consolidated Balance Sheets. Nine Months Ended September 30, 2018 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Balance at beginning of period $ 81 $ 10 $ 15 $ 3 $ 12 $ 47 $ 5 $ 2 Provisions/adjustments 7 3 2 3 (1 ) 3 1 — Cash reductions (20 ) (2 ) (5 ) (1 ) (4 ) (12 ) (1 ) — Balance at end of period $ 68 $ 11 $ 12 $ 5 $ 7 $ 38 $ 5 $ 2 Nine Months Ended September 30, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Balance at beginning of period $ 98 $ 10 $ 18 $ 3 $ 14 $ 59 $ 10 $ 1 Provisions/adjustments (1 ) 2 1 — 1 (3 ) (2 ) 1 Cash reductions (13 ) (2 ) (3 ) — (3 ) (7 ) (1 ) — Balance at end of period $ 84 $ 10 $ 16 $ 3 $ 12 $ 49 $ 7 $ 2
Reserve, Legal [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
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 related to the termination of an EPC contract discussed above. Reserves are classified on the Condensed 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. (in millions) September 30, 2018 December 31, 2017 Reserves for Legal Matters Duke Energy $ 63 $ 88 Duke Energy Carolinas 11 30 Progress Energy 50 55 Duke Energy Progress 11 13 Duke Energy Florida 23 24 Piedmont 1 2

Debt and Credit Facilities (Tab

Debt and Credit Facilities (Tables)	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Schedule of Long-term Debt Instruments	The following table shows the significant components of Current Maturities of Long-Term Debt on the Condensed 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 September 30, 2018 Unsecured Debt Progress Energy March 2019 7.050 % $ 450 Duke Energy (Parent) September 2019 5.050 % 500 Piedmont September 2019 2.848 % (b) 350 First Mortgage Bonds Duke Energy Carolinas November 2018 7.000 % 500 Duke Energy Progress January 2019 5.300 % 600 Duke Energy Ohio April 2019 5.450 % 450 Other (a) 605 Current maturities of long-term debt $ 3,455 (a) Includes capital lease obligations, amortizing debt and small bullet maturities. (b) Debt issuance has a floating interest rate. The following table summarizes significant debt issuances (in millions). Nine Months Ended September 30, 2018 Duke Duke Duke Duke Maturity Interest Duke Energy Energy Energy Energy Issuance Date Date Rate Energy (Parent) Carolinas Progress Florida Unsecured Debt March 2018 (a) April 2025 3.950 % $ 250 $ 250 $ — $ — $ — May 2018 (b) May 2021 2.819 % 500 500 — — — September 2018 (c) September 2078 5.625 % 500 500 — — — First Mortgage Bonds March 2018 (d) March 2023 3.050 % 500 — 500 — — March 2018 (d) March 2048 3.950 % 500 — 500 — — June 2018 (e) July 2028 3.800 % 600 — — — 600 June 2018 (e) July 2048 4.200 % 400 — — — 400 August 2018 (f) September 2023 3.375 % 300 — — 300 — August 2018 (f) September 2028 3.700 % 500 — — 500 — Total issuances $ 4,050 $ 1,250 $ 1,000 $ 800 $ 1,000 (a) Debt issued to pay down short-term debt. (b) Debt issued to pay down short-term debt. Debt issuance has a floating interest rate. (c) Callable after September 2023 at par. Debt issued to pay down short-term debt and for general corporate purposes. (d) Debt issued to repay at maturity a $ 300 million first mortgage bond due April 2018, pay down intercompany short-term debt and for general corporate purposes. (e) Debt issued to repay a portion of intercompany short-term debt under money-pool borrowing arrangement and for general corporate purposes. (f) Debt issued to repay short-term debt and for general corporate purposes.
Schedule Of Line Of Credit Facilities	The table below includes the current borrowing sublimits and available capacity under the Master Credit Facility. September 30, 2018 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 $ 2,650 $ 1,750 $ 1,400 $ 650 $ 450 $ 600 $ 500 Reduction to backstop issuances Commercial paper (b) (2,519 ) (988 ) (872 ) (150 ) — (216 ) (293 ) — Outstanding letters of credit (55 ) (47 ) (4 ) (2 ) — — — (2 ) Tax-exempt bonds (81 ) — — — — — (81 ) — Coal ash set-aside (500 ) — (250 ) (250 ) — — — — Available capacity under the Master Credit Facility $ 4,845 $ 1,615 $ 624 $ 998 $ 650 $ 234 $ 226 $ 498 (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 on the Condensed Consolidated Balance Sheets.

Asset Retirement Obligations (T

Asset Retirement Obligations (Tables)	9 Months Ended
	Sep. 30, 2018
Asset Retirement Obligation [Abstract]
Schedule of Asset Retirement Obligations	The following table presents the AROs recorded on the Condensed Consolidated Balance Sheets. September 30, 2018 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) $ 5,367 $ 2,031 $ 3,181 $ 2,650 $ 531 $ — $ — $ — Closure of Ash Impoundments 4,575 1,623 2,175 2,154 20 52 725 — Other 314 58 79 37 42 46 19 15 Total ARO $ 10,256 $ 3,712 $ 5,435 $ 4,841 $ 593 $ 98 $ 744 $ 15 Less: current portion 902 292 475 470 4 7 128 — Total noncurrent ARO $ 9,354 $ 3,420 $ 4,960 $ 4,371 $ 589 $ 91 $ 616 $ 15 (a) Duke Energy amount includes purchase accounting adjustments related to the merger with Progress Energy.
Schedule of Change in Asset Retirement Obligation	The following table presents the change in liability associated with AROs for the Duke Energy Registrants. Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Balance at December 31, 2017 (a) $ 10,175 $ 3,610 $ 5,414 $ 4,673 $ 742 $ 84 $ 781 $ 15 Accretion expense (b) 319 133 168 145 23 3 22 — Liabilities settled (c) (431 ) (198 ) (186 ) (155 ) (31 ) (5 ) (42 ) — Liabilities incurred in the current year 34 8 — — — — 25 — Revisions in estimates of cash flows (d) 159 159 39 178 (141 ) 16 (42 ) — Balance at September 30, 2018 $ 10,256 $ 3,712 $ 5,435 $ 4,841 $ 593 $ 98 $ 744 $ 15 (a) Primarily relates to decommissioning nuclear power facilities, closure of ash impoundments, asbestos removal, closure of landfills at fossil generation facilities, retirement of natural gas mains and removal of renewable energy generation assets. (b) For the nine months ended September 30, 2018 , substantially all accretion expense relates to Duke Energy's regulated operations and has been deferred in accordance with regulatory accounting treatment. (c) Primarily relates to ash impoundment closures and nuclear decommissioning of Crystal River Unit 3. (d) Primarily relates to increases in groundwater monitoring estimates for closure of ash impoundments, partially offset by modifications to the timing of expected cash flows and a reduction for nuclear decommissioning at Crystal River Unit 3 compared to original estimates.

Goodwill (Tables)

Goodwill (Tables)	9 Months Ended
	Sep. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill By Reportable Operating Segment	The following table presents the goodwill by reportable operating segment included on Duke Energy's Condensed Consolidated Balance Sheets at September 30, 2018 , and December 31, 2017 . Electric Utilities Gas Utilities Commercial (in millions) and Infrastructure and Infrastructure Renewables Total Goodwill balance at December 31, 2017 $ 17,379 $ 1,924 $ 122 $ 19,425 Accumulated impairment charges — — (29 ) $ (29 ) Goodwill balance at December 31, 2017, adjusted for accumulated impairment charges $ 17,379 $ 1,924 $ 93 $ 19,396 Goodwill balance at September 30, 2018 $ 17,379 $ 1,924 $ 122 $ 19,425 Accumulated impairment charges — — (122 ) (122 ) Goodwill balance at September 30, 2018, adjusted for accumulated impairment charges $ 17,379 $ 1,924 $ — $ 19,303

Related Party Transactions (Tab

Related Party Transactions (Tables)	9 Months Ended
	Sep. 30, 2018
Related Party Transaction [Line Items]
Schedule of Related Party Transactions, Other Revenue and Expense	Material amounts related to transactions with related parties included on the Condensed Consolidated Statements of Operations and Comprehensive Income are presented in the following table. Three Months Ended September 30, Nine Months Ended September 30, (in millions) 2018 2017 2018 2017 Duke Energy Carolinas Corporate governance and shared service expenses (a) $ 214 $ 206 $ 647 $ 645 Indemnification coverages (b) 6 5 17 17 JDA revenue (c) 13 9 66 42 JDA expense (c) 61 39 134 91 Intercompany natural gas purchases (d) 3 3 11 5 Progress Energy Corporate governance and shared service expenses (a) $ 216 $ 207 $ 613 $ 555 Indemnification coverages (b) 8 10 25 29 JDA revenue (c) 61 39 134 91 JDA expense (c) 13 9 66 42 Intercompany natural gas purchases (d) 20 19 58 57 Duke Energy Progress Corporate governance and shared service expenses (a) $ 138 $ 112 $ 382 $ 321 Indemnification coverages (b) 3 4 9 11 JDA revenue (c) 61 39 134 91 JDA expense (c) 13 9 66 42 Intercompany natural gas purchases (d) 20 19 58 57 Duke Energy Florida Corporate governance and shared service expenses (a) $ 78 $ 95 $ 231 $ 234 Indemnification coverages (b) 5 6 16 18 Duke Energy Ohio Corporate governance and shared service expenses (a) $ 85 $ 90 $ 264 $ 275 Indemnification coverages (b) 1 1 3 3 Duke Energy Indiana Corporate governance and shared service expenses (a) $ 105 $ 94 $ 302 $ 281 Indemnification coverages (b) 2 2 6 6 Piedmont Corporate governance and shared service expenses (a) $ 39 $ 11 $ 115 $ 25 Indemnification coverages (b) 1 1 2 2 Intercompany natural gas sales (d) 23 22 69 62 (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 Condensed 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 Condensed Consolidated Statements of Operations and Comprehensive Income. (c) Duke Energy Carolinas and Duke Energy Progress participate in a Joint Dispatch Agreement (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 Condensed 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 Operating revenues, and Duke Energy Carolinas and Duke Energy Progress record the related purchases as a component of Fuel used in electric generation and purchased power on their respective Condensed Consolidated Statements of Operations and Comprehensive Income. These intercompany revenues and expenses are eliminated in consolidation. The following table presents expenses for the three and nine months ended September 30, 2018 , and 2017 , which are included in Cost of natural gas on Piedmont's Condensed Consolidated Statements of Operations and Comprehensive Income. Three Months Ended September 30, Nine Months Ended September 30, (in millions) Type of expense 2018 2017 2018 2017 Cardinal Transportation Costs $ 2 $ 2 $ 5 $ 6 Pine Needle Natural Gas Storage Costs 2 2 6 6 Hardy Storage Natural Gas Storage Costs 2 2 7 7 Total $ 6 $ 6 $ 18 $ 19 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 September 30, 2018 Intercompany income tax receivable $ 32 $ 196 $ 80 $ — $ — $ 22 $ 11 Intercompany income tax payable — — — 77 9 — — December 31, 2017 Intercompany income tax receivable $ — $ 168 $ — $ 44 $ 22 $ — $ 7 Intercompany income tax payable 44 — 21 — — 35 —

Derivatives and Hedging (Tables

Derivatives and Hedging (Tables)	9 Months Ended
	Sep. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Notional Amounts of Outstanding Derivative Positions	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. September 30, 2018 Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy Carolinas Energy Progress Florida Indiana Piedmont Electricity (gigawatt-hours) 170 — — — — 170 — Natural gas (millions of dekatherms) 744 119 167 158 9 1 457 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 The following table shows notional amounts of outstanding derivatives related to interest rate risk. September 30, 2018 Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Cash flow hedges $ 411 $ — $ — $ — $ — $ — Undesignated contracts 1,127 400 500 250 250 27 Total notional amount (a) $ 1,538 $ 400 $ 500 $ 250 $ 250 $ 27 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 (a) Duke Energy includes amounts related to consolidated VIEs of $411 million in cash flow hedges and $200 million in undesignated contracts as of September 30, 2018 , and $660 million in cash flow hedges as of December 31, 2017 .
Location And Fair Value Of Derivatives Recognized in the Condensed 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 Condensed 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 September 30, 2018 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 $ 46 $ 2 $ 3 $ 2 $ 1 $ 8 $ 29 $ 4 Noncurrent 1 — — — — — — — Total Derivative Assets – Commodity Contracts $ 47 $ 2 $ 3 $ 2 $ 1 $ 8 $ 29 $ 4 Interest Rate Contracts Designated as Hedging Instruments Current $ 6 $ 5 $ — $ — $ — $ — $ — $ — Noncurrent 6 — — — — — — — Not Designated as Hedging Instruments Current 1 — — — — — — — Noncurrent 17 — — — — — — — Total Derivative Assets – Interest Rate Contracts $ 30 $ 5 $ — $ — $ — $ — $ — $ — Total Derivative Assets $ 77 $ 7 $ 3 $ 2 $ 1 $ 8 $ 29 $ 4 Derivative Liabilities September 30, 2018 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 $ 26 $ 14 $ 5 $ 5 $ — $ — $ — $ 7 Noncurrent 177 14 17 8 — — — 146 Total Derivative Liabilities – Commodity Contracts $ 203 $ 28 $ 22 $ 13 $ — $ — $ — $ 153 Interest Rate Contracts Designated as Hedging Instruments Current $ 2 $ — $ — $ — $ — $ — $ — $ — Not Designated as Hedging Instruments Current 7 — 6 3 3 1 — — Noncurrent 13 — 9 8 2 3 — — Total Derivative Liabilities – Interest Rate Contracts $ 22 $ — $ 15 $ 11 $ 5 $ 4 $ — $ — Total Derivative Liabilities $ 225 $ 28 $ 37 $ 24 $ 5 $ 4 $ — $ 153 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
Offsetting Assets	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 $ — $ — $ — $ — The following tables present the line items on the Condensed 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 September 30, 2018 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 $ 53 $ 7 $ 3 $ 2 $ 1 $ 8 $ 29 $ 4 Gross amounts offset (4 ) (2 ) (2 ) (2 ) — — — — Net amounts presented in Current Assets: Other $ 49 $ 5 $ 1 $ — $ 1 $ 8 $ 29 $ 4 Noncurrent Gross amounts recognized $ 24 $ — $ — $ — $ — $ — $ — $ — Gross amounts offset (1 ) — — — — — — — Net amounts presented in Other Noncurrent Assets: Other $ 23 $ — $ — $ — $ — $ — $ — $ —
Offsetting Liabilities	Derivative Liabilities September 30, 2018 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 $ 14 $ 11 $ 8 $ 3 $ 1 $ — $ 7 Gross amounts offset (4 ) (2 ) (2 ) (2 ) — — — — Net amounts presented in Current Liabilities: Other $ 31 $ 12 $ 9 $ 6 $ 3 $ 1 $ — $ 7 Noncurrent Gross amounts recognized $ 190 $ 14 $ 26 $ 16 $ 2 $ 3 $ — $ 146 Gross amounts offset (1 ) — (1 ) (1 ) — — — — Net amounts presented in Other Noncurrent Liabilities: Other $ 189 $ 14 $ 25 $ 15 $ 2 $ 3 $ — $ 146 The following tables present the line items on the Condensed 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 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. September 30, 2018 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 $ 48 $ 26 $ 23 $ 22 $ — Fair value of collateral already posted — — — — — Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered 48 26 23 22 — 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

Investments in Debt and Equit_2

Investments in Debt and Equity Securities (Tables)	9 Months Ended
	Sep. 30, 2018
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading, and Equity Securities, FV-NI	The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. September 30, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 75 $ — $ — $ 115 Equity securities 3,117 48 5,272 2,805 27 4,914 Corporate debt securities 5 10 595 17 2 570 Municipal bonds — 7 346 4 3 344 U.S. government bonds 5 25 974 11 7 1,027 Other debt securities — 3 141 — 1 118 Total NDTF Investments $ 3,127 $ 93 $ 7,403 $ 2,837 $ 40 $ 7,088 Other Investments Cash and cash equivalents $ — $ — $ 21 $ — $ — $ 15 Equity securities 51 — 115 59 — 123 Corporate debt securities — 1 64 1 — 57 Municipal bonds 1 1 85 2 1 83 U.S. government bonds — 1 59 — — 41 Other debt securities — 1 43 — 1 44 Total Other Investments $ 52 $ 4 $ 387 $ 62 $ 2 $ 363 Total Investments $ 3,179 $ 97 $ 7,790 $ 2,899 $ 42 $ 7,451 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected .
Debt Securities, Available-for-sale	The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. September 30, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 75 $ — $ — $ 115 Equity securities 3,117 48 5,272 2,805 27 4,914 Corporate debt securities 5 10 595 17 2 570 Municipal bonds — 7 346 4 3 344 U.S. government bonds 5 25 974 11 7 1,027 Other debt securities — 3 141 — 1 118 Total NDTF Investments $ 3,127 $ 93 $ 7,403 $ 2,837 $ 40 $ 7,088 Other Investments Cash and cash equivalents $ — $ — $ 21 $ — $ — $ 15 Equity securities 51 — 115 59 — 123 Corporate debt securities — 1 64 1 — 57 Municipal bonds 1 1 85 2 1 83 U.S. government bonds — 1 59 — — 41 Other debt securities — 1 43 — 1 44 Total Other Investments $ 52 $ 4 $ 387 $ 62 $ 2 $ 363 Total Investments $ 3,179 $ 97 $ 7,790 $ 2,899 $ 42 $ 7,451 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected .
Available-for-sale Securities	The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. September 30, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 75 $ — $ — $ 115 Equity securities 3,117 48 5,272 2,805 27 4,914 Corporate debt securities 5 10 595 17 2 570 Municipal bonds — 7 346 4 3 344 U.S. government bonds 5 25 974 11 7 1,027 Other debt securities — 3 141 — 1 118 Total NDTF Investments $ 3,127 $ 93 $ 7,403 $ 2,837 $ 40 $ 7,088 Other Investments Cash and cash equivalents $ — $ — $ 21 $ — $ — $ 15 Equity securities 51 — 115 59 — 123 Corporate debt securities — 1 64 1 — 57 Municipal bonds 1 1 85 2 1 83 U.S. government bonds — 1 59 — — 41 Other debt securities — 1 43 — 1 44 Total Other Investments $ 52 $ 4 $ 387 $ 62 $ 2 $ 363 Total Investments $ 3,179 $ 97 $ 7,790 $ 2,899 $ 42 $ 7,451 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected .
Investments Classified by Contractual Maturity Date	The table below summarizes the maturity date for debt securities. (in millions) September 30, 2018 Due in one year or less $ 100 Due after one through five years 492 Due after five through 10 years 561 Due after 10 years 1,154 Total $ 2,307
Schedule of Realized Gain (Loss)	Realized gains and losses, which were determined on a specific identification basis, from sales of FV-NI and AFS securities for the three and nine months ended September 30, 2018 , and from sales of AFS securities for the three and nine months ended September 30, 2017 , were as follows. Three Months Ended Nine Months Ended (in millions) September 30, 2018 September 30, 2018 FV-NI: Realized gains $ 19 $ 85 Realized losses 16 60 AFS: Realized gains 4 14 Realized losses 7 32 Three Months Ended Nine Months Ended (in millions) September 30, 2017 September 30, 2017 Realized gains $ 37 $ 170 Realized losses 25 124
Duke Energy Carolinas [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading, and Equity Securities, FV-NI	The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. September 30, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 18 $ — $ — $ 32 Equity securities 1,692 29 2,890 1,531 12 2,692 Corporate debt securities 2 7 372 9 2 359 Municipal bonds — 2 80 — 1 60 U.S. government bonds 1 14 439 3 4 503 Other debt securities — 3 137 — 1 112 Total NDTF Investments $ 1,695 $ 55 $ 3,936 $ 1,543 $ 20 $ 3,758 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected .
Debt Securities, Available-for-sale	The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. September 30, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 18 $ — $ — $ 32 Equity securities 1,692 29 2,890 1,531 12 2,692 Corporate debt securities 2 7 372 9 2 359 Municipal bonds — 2 80 — 1 60 U.S. government bonds 1 14 439 3 4 503 Other debt securities — 3 137 — 1 112 Total NDTF Investments $ 1,695 $ 55 $ 3,936 $ 1,543 $ 20 $ 3,758 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected .
Available-for-sale Securities	The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. September 30, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 18 $ — $ — $ 32 Equity securities 1,692 29 2,890 1,531 12 2,692 Corporate debt securities 2 7 372 9 2 359 Municipal bonds — 2 80 — 1 60 U.S. government bonds 1 14 439 3 4 503 Other debt securities — 3 137 — 1 112 Total NDTF Investments $ 1,695 $ 55 $ 3,936 $ 1,543 $ 20 $ 3,758 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected .
Investments Classified by Contractual Maturity Date	The table below summarizes the maturity date for debt securities. (in millions) September 30, 2018 Due in one year or less $ 12 Due after one through five years 161 Due after five through 10 years 289 Due after 10 years 566 Total $ 1,028
Schedule of Realized Gain (Loss)	Realized gains and losses, which were determined on a specific identification basis, from sales of FV-NI and AFS securities for the three and nine months ended September 30, 2018 , and from sales of AFS securities for the three and nine months ended September 30, 2017 , were as follows. Three Months Ended Nine Months Ended (in millions) September 30, 2018 September 30, 2018 FV-NI: Realized gains $ 11 $ 47 Realized losses 8 30 AFS: Realized gains 4 13 Realized losses 6 24 Three Months Ended Nine Months Ended (in millions) September 30, 2017 September 30, 2017 Realized gains $ 20 $ 110 Realized losses 13 76
Progress Energy [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading, and Equity Securities, FV-NI	The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. September 30, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 57 $ — $ — $ 83 Equity securities 1,425 19 2,382 1,274 15 2,222 Corporate debt securities 3 3 223 8 — 211 Municipal bonds — 5 266 4 2 284 U.S. government bonds 4 11 535 8 3 524 Other debt securities — — 4 — — 6 Total NDTF Investments $ 1,432 $ 38 $ 3,467 $ 1,294 $ 20 $ 3,330 Other Investments Cash and cash equivalents $ — $ — $ 18 $ — $ — $ 12 Municipal bonds 1 — 48 2 — 47 Total Other Investments $ 1 $ — $ 66 $ 2 $ — $ 59 Total Investments $ 1,433 $ 38 $ 3,533 $ 1,296 $ 20 $ 3,389 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected .
Debt Securities, Available-for-sale	The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. September 30, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 57 $ — $ — $ 83 Equity securities 1,425 19 2,382 1,274 15 2,222 Corporate debt securities 3 3 223 8 — 211 Municipal bonds — 5 266 4 2 284 U.S. government bonds 4 11 535 8 3 524 Other debt securities — — 4 — — 6 Total NDTF Investments $ 1,432 $ 38 $ 3,467 $ 1,294 $ 20 $ 3,330 Other Investments Cash and cash equivalents $ — $ — $ 18 $ — $ — $ 12 Municipal bonds 1 — 48 2 — 47 Total Other Investments $ 1 $ — $ 66 $ 2 $ — $ 59 Total Investments $ 1,433 $ 38 $ 3,533 $ 1,296 $ 20 $ 3,389 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected .
Available-for-sale Securities	The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. September 30, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 57 $ — $ — $ 83 Equity securities 1,425 19 2,382 1,274 15 2,222 Corporate debt securities 3 3 223 8 — 211 Municipal bonds — 5 266 4 2 284 U.S. government bonds 4 11 535 8 3 524 Other debt securities — — 4 — — 6 Total NDTF Investments $ 1,432 $ 38 $ 3,467 $ 1,294 $ 20 $ 3,330 Other Investments Cash and cash equivalents $ — $ — $ 18 $ — $ — $ 12 Municipal bonds 1 — 48 2 — 47 Total Other Investments $ 1 $ — $ 66 $ 2 $ — $ 59 Total Investments $ 1,433 $ 38 $ 3,533 $ 1,296 $ 20 $ 3,389 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected .
Investments Classified by Contractual Maturity Date	The table below summarizes the maturity date for debt securities. (in millions) September 30, 2018 Due in one year or less $ 83 Due after one through five years 268 Due after five through 10 years 217 Due after 10 years 508 Total $ 1,076
Schedule of Realized Gain (Loss)	Realized gains and losses, which were determined on a specific identification basis, from sales of FV-NI and AFS securities for the three and nine months ended September 30, 2018 , and from sales of AFS securities for the three and nine months ended September 30, 2017 , were as follows. Three Months Ended Nine Months Ended (in millions) September 30, 2018 September 30, 2018 FV-NI: Realized gains $ 8 $ 38 Realized losses 8 30 AFS: Realized gains — 1 Realized losses 1 8 Three Months Ended Nine Months Ended (in millions) September 30, 2017 September 30, 2017 Realized gains $ 16 $ 58 Realized losses 12 47
Duke Energy Progress [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading, and Equity Securities, FV-NI	The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. September 30, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 42 $ — $ — $ 50 Equity securities 1,101 14 1,913 980 12 1,795 Corporate debt securities 2 2 162 6 — 149 Municipal bonds — 5 265 4 2 283 U.S. government bonds 3 8 352 5 2 310 Other debt securities — — 2 — — 4 Total NDTF Investments $ 1,106 $ 29 $ 2,736 $ 995 $ 16 $ 2,591 Other Investments Cash and cash equivalents $ — $ — $ 8 $ — $ — $ 1 Total Other Investments $ — $ — $ 8 $ — $ — $ 1 Total Investments $ 1,106 $ 29 $ 2,744 $ 995 $ 16 $ 2,592 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected .
Debt Securities, Available-for-sale	The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. September 30, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 42 $ — $ — $ 50 Equity securities 1,101 14 1,913 980 12 1,795 Corporate debt securities 2 2 162 6 — 149 Municipal bonds — 5 265 4 2 283 U.S. government bonds 3 8 352 5 2 310 Other debt securities — — 2 — — 4 Total NDTF Investments $ 1,106 $ 29 $ 2,736 $ 995 $ 16 $ 2,591 Other Investments Cash and cash equivalents $ — $ — $ 8 $ — $ — $ 1 Total Other Investments $ — $ — $ 8 $ — $ — $ 1 Total Investments $ 1,106 $ 29 $ 2,744 $ 995 $ 16 $ 2,592 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected .
Available-for-sale Securities	The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. September 30, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 42 $ — $ — $ 50 Equity securities 1,101 14 1,913 980 12 1,795 Corporate debt securities 2 2 162 6 — 149 Municipal bonds — 5 265 4 2 283 U.S. government bonds 3 8 352 5 2 310 Other debt securities — — 2 — — 4 Total NDTF Investments $ 1,106 $ 29 $ 2,736 $ 995 $ 16 $ 2,591 Other Investments Cash and cash equivalents $ — $ — $ 8 $ — $ — $ 1 Total Other Investments $ — $ — $ 8 $ — $ — $ 1 Total Investments $ 1,106 $ 29 $ 2,744 $ 995 $ 16 $ 2,592 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected .
Investments Classified by Contractual Maturity Date	The table below summarizes the maturity date for debt securities. (in millions) September 30, 2018 Due in one year or less $ 40 Due after one through five years 200 Due after five through 10 years 156 Due after 10 years 385 Total $ 781
Schedule of Realized Gain (Loss)	Realized gains and losses, which were determined on a specific identification basis, from sales of FV-NI and AFS securities for the three and nine months ended September 30, 2018 , and from sales of AFS securities for the three and nine months ended September 30, 2017 , were as follows. Three Months Ended Nine Months Ended (in millions) September 30, 2018 September 30, 2018 FV-NI: Realized gains $ 7 $ 32 Realized losses 7 27 AFS: Realized gains — 1 Realized losses 1 6 Three Months Ended Nine Months Ended (in millions) September 30, 2017 September 30, 2017 Realized gains $ 14 $ 49 Realized losses 11 41
Duke Energy Florida [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading, and Equity Securities, FV-NI	The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. September 30, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 15 $ — $ — $ 33 Equity securities 324 5 469 294 3 427 Corporate debt securities 1 1 61 2 — 62 Municipal bonds — — 1 — — 1 U.S. government bonds 1 3 183 3 1 214 Other debt securities — — 2 — — 2 Total NDTF Investments (b) $ 326 $ 9 $ 731 $ 299 $ 4 $ 739 Other Investments Cash and cash equivalents $ — $ — $ — $ — $ — $ 1 Municipal bonds 1 — 48 2 — 47 Total Other Investments $ 1 $ — $ 48 $ 2 $ — $ 48 Total Investments $ 327 $ 9 $ 779 $ 301 $ 4 $ 787 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected . (b) During the nine months ended September 30, 2018 , 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.
Debt Securities, Available-for-sale	The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. September 30, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 15 $ — $ — $ 33 Equity securities 324 5 469 294 3 427 Corporate debt securities 1 1 61 2 — 62 Municipal bonds — — 1 — — 1 U.S. government bonds 1 3 183 3 1 214 Other debt securities — — 2 — — 2 Total NDTF Investments (b) $ 326 $ 9 $ 731 $ 299 $ 4 $ 739 Other Investments Cash and cash equivalents $ — $ — $ — $ — $ — $ 1 Municipal bonds 1 — 48 2 — 47 Total Other Investments $ 1 $ — $ 48 $ 2 $ — $ 48 Total Investments $ 327 $ 9 $ 779 $ 301 $ 4 $ 787 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected . (b) During the nine months ended September 30, 2018 , 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.
Available-for-sale Securities	The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. September 30, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 15 $ — $ — $ 33 Equity securities 324 5 469 294 3 427 Corporate debt securities 1 1 61 2 — 62 Municipal bonds — — 1 — — 1 U.S. government bonds 1 3 183 3 1 214 Other debt securities — — 2 — — 2 Total NDTF Investments (b) $ 326 $ 9 $ 731 $ 299 $ 4 $ 739 Other Investments Cash and cash equivalents $ — $ — $ — $ — $ — $ 1 Municipal bonds 1 — 48 2 — 47 Total Other Investments $ 1 $ — $ 48 $ 2 $ — $ 48 Total Investments $ 327 $ 9 $ 779 $ 301 $ 4 $ 787 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected . (b) During the nine months ended September 30, 2018 , 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) September 30, 2018 Due in one year or less $ 43 Due after one through five years 68 Due after five through 10 years 61 Due after 10 years 123 Total $ 295
Schedule of Realized Gain (Loss)	Realized gains and losses, which were determined on a specific identification basis, from sales of FV-NI and AFS securities for the three and nine months ended September 30, 2018 , and from sales of AFS securities for the three and nine months ended September 30, 2017 , were as follows. Three Months Ended Nine Months Ended (in millions) September 30, 2018 September 30, 2018 FV-NI: Realized gains $ 1 $ 6 Realized losses 1 3 AFS: Realized gains — — Realized losses — 2 Three Months Ended Nine Months Ended (in millions) September 30, 2017 September 30, 2017 Realized gains $ 2 $ 9 Realized losses 1 6
Duke Energy Indiana [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading, and Equity Securities, FV-NI	The following table presents the estimated fair value of investments in debt and equity securities; equity investments are measured at FV-NI and debt investments are classified as AFS. September 30, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value Investments Equity securities $ 40 $ — $ 78 $ 49 $ — $ 97 Corporate debt securities — — 8 — — 3 Municipal bonds — 1 32 — 1 28 Total Investments $ 40 $ 1 $ 118 $ 49 $ 1 $ 128 (a) Realized and unrealized gains and losses where regulatory accounting is applied are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected .
Debt Securities, Available-for-sale	The following table presents the estimated fair value of investments in debt and equity securities; equity investments are measured at FV-NI and debt investments are classified as AFS. September 30, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value Investments Equity securities $ 40 $ — $ 78 $ 49 $ — $ 97 Corporate debt securities — — 8 — — 3 Municipal bonds — 1 32 — 1 28 Total Investments $ 40 $ 1 $ 118 $ 49 $ 1 $ 128 (a) Realized and unrealized gains and losses where regulatory accounting is applied are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected .
Available-for-sale Securities	The following table presents the estimated fair value of investments in debt and equity securities; equity investments are measured at FV-NI and debt investments are classified as AFS. September 30, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value Investments Equity securities $ 40 $ — $ 78 $ 49 $ — $ 97 Corporate debt securities — — 8 — — 3 Municipal bonds — 1 32 — 1 28 Total Investments $ 40 $ 1 $ 118 $ 49 $ 1 $ 128 (a) Realized and unrealized gains and losses where regulatory accounting is applied are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected .
Investments Classified by Contractual Maturity Date	The table below summarizes the maturity date for debt securities. (in millions) September 30, 2018 Due in one year or less $ 2 Due after one through five years 20 Due after five through 10 years 5 Due after 10 years 13 Total $ 40

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2018
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 Condensed Consolidated Balance Sheets. Derivative amounts in the tables below for all Duke Energy Registrants exclude cash collateral, which is disclosed in Note 9 . See Note 10 for additional information related to investments by major security type for the Duke Energy Registrants. September 30, 2018 (in millions) Total Fair Value Level 1 Level 2 Level 3 Not Categorized NDTF equity securities $ 5,272 $ 5,203 $ — $ — $ 69 NDTF debt securities 2,131 510 1,621 — — Other equity securities 115 115 — — — Other debt securities 272 78 194 — — Derivative assets 77 4 36 37 — Total assets 7,867 5,910 1,851 37 69 Derivative liabilities (225 ) — (72 ) (153 ) — Net assets (liabilities) $ 7,642 $ 5,910 $ 1,779 $ (116 ) $ 69 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 equity securities 123 123 — — — Other 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
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' Condensed Consolidated Statements of Operations and Comprehensive Income. Amounts included in changes of net assets on the Duke Energy Registrants' Condensed Consolidated Balance Sheets are included in regulatory assets or liabilities. All derivative assets and liabilities are presented on a net basis. Three Months Ended September 30, 2018 Three Months Ended September 30, 2017 (in millions) Investments Derivatives (net) Total Investments Derivatives (net) Total Balance at beginning of period $ — $ (97 ) $ (97 ) $ — $ (91 ) $ (91 ) Purchases, sales, issuances and settlements: Settlements — (14 ) (14 ) — (12 ) (12 ) Total (losses) gains included on the Condensed Consolidated Balance Sheet — (5 ) (5 ) — 10 10 Balance at end of period $ — $ (116 ) $ (116 ) $ — $ (93 ) $ (93 ) Nine Months Ended September 30, 2018 Nine Months Ended September 30, 2017 (in millions) Investments Derivatives (net) Total Investments Derivatives (net) Total Balance at beginning of period $ — $ (114 ) $ (114 ) $ 5 $ (166 ) $ (161 ) Total pretax realized or unrealized gains included in comprehensive income — — — 1 — 1 Purchases, sales, issuances and settlements: Purchases — 56 56 — 55 55 Sales — — — (6 ) — (6 ) Settlements — (43 ) (43 ) — (30 ) (30 ) Total (losses) gains included on the Condensed Consolidated Balance Sheet — (15 ) (15 ) — 48 48 Balance at end of period $ — $ (116 ) $ (116 ) $ — $ (93 ) $ (93 )
Quantitative Information Table - Level 3	The following tables include quantitative information about the Duke Energy Registrants' derivatives classified as Level 3. September 30, 2018 Fair Value Investment Type (in millions) Valuation Technique Unobservable Input Range Duke Energy Ohio Financial Transmission Rights (FTRs) $ 8 RTO auction pricing FTR price – per megawatt-hour (MWh) $ 1.03 - $ 4.10 Duke Energy Indiana FTRs 29 RTO auction pricing FTR price – per MWh (2.32 ) - 8.11 Piedmont Natural gas contracts (153 ) Discounted cash flow Forward natural gas curves – price per million British thermal unit (MMBtu) 1.74 - 3.41 Duke Energy Total Level 3 derivatives $ (116 ) 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 )
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. September 30, 2018 December 31, 2017 (in millions) Book Value Fair Value Book Value Fair Value Duke Energy (a) $ 53,962 $ 53,949 $ 52,279 $ 55,331 Duke Energy Carolinas 10,395 10,887 10,103 11,372 Progress Energy 18,912 19,825 17,837 20,000 Duke Energy Progress 8,154 8,231 7,357 7,992 Duke Energy Florida 7,371 7,749 7,095 7,953 Duke Energy Ohio 2,066 2,136 2,067 2,249 Duke Energy Indiana 3,783 4,178 3,783 4,464 Piedmont 2,138 2,175 2,037 2,209 (a) Book value of long-term debt includes $1.6 billion as of September 30, 2018 , and $1.7 billion as of December 31, 2017 , of unamortized debt discount and premium, net in purchase accounting adjustments related to the mergers with Progress Energy and Piedmont that are excluded from fair value of long-term debt.
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 Condensed Consolidated Balance Sheets. September 30, 2018 (in millions) Total Fair Value Level 1 Level 2 Not Categorized NDTF equity securities $ 2,890 $ 2,821 $ — $ 69 NDTF debt securities 1,046 122 924 — Derivative assets 7 — 7 — Total assets 3,943 2,943 931 69 Derivative liabilities (28 ) — (28 ) — Net assets $ 3,915 $ 2,943 $ 903 $ 69 December 31, 2017 (in millions) Total Fair Value Level 1 Level 2 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
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. Investments Three Months Ended September 30, Nine Months Ended September 30, (in millions) 2018 2017 2018 2017 Balance at beginning of period $ — $ — $ — $ 3 Total pretax realized or unrealized gains included in comprehensive income — — — 1 Purchases, sales, issuances and settlements: Sales — — — (4 ) Balance at end of period $ — $ — $ — $ —
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 tables provide recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets. September 30, 2018 December 31, 2017 (in millions) Total Fair Value Level 1 Level 2 Total Fair Value Level 1 Level 2 NDTF equity securities $ 2,382 $ 2,382 $ — $ 2,222 $ 2,222 $ — NDTF debt securities 1,085 388 697 1,108 431 677 Other debt securities 66 18 48 59 12 47 Derivative assets 3 — 3 3 1 2 Total assets 3,536 2,788 748 3,392 2,666 726 Derivative liabilities (37 ) — (37 ) (36 ) (1 ) (35 ) Net assets $ 3,499 $ 2,788 $ 711 $ 3,356 $ 2,665 $ 691
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 tables provide recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets. September 30, 2018 December 31, 2017 (in millions) Total Fair Value Level 1 Level 2 Total Fair Value Level 1 Level 2 NDTF equity securities $ 1,913 $ 1,913 $ — $ 1,795 $ 1,795 $ — NDTF debt securities 823 254 569 796 243 553 Other debt securities 8 8 — 1 1 — Derivative assets 2 — 2 2 1 1 Total assets 2,746 2,175 571 2,594 2,040 554 Derivative liabilities (24 ) — (24 ) (18 ) (1 ) (17 ) Net assets $ 2,722 $ 2,175 $ 547 $ 2,576 $ 2,039 $ 537
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 tables provide recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets. September 30, 2018 December 31, 2017 (in millions) Total Fair Value Level 1 Level 2 Total Fair Value Level 1 Level 2 NDTF equity securities $ 469 $ 469 $ — $ 427 $ 427 $ — NDTF debt securities 262 134 128 312 188 124 Other debt securities 48 — 48 48 1 47 Derivative assets 1 — 1 1 — 1 Total assets 780 603 177 788 616 172 Derivative liabilities (5 ) — (5 ) (12 ) — (12 ) Net assets $ 775 $ 603 $ 172 $ 776 $ 616 $ 160
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 Condensed Consolidated Balance Sheets. September 30, 2018 December 31, 2017 (in millions) Total Fair Value Level 2 Level 3 Total Fair Value Level 2 Level 3 Derivative assets $ 8 $ — $ 8 $ 1 $ — $ 1 Derivative liabilities (4 ) (4 ) — (5 ) (5 ) — Net assets (liabilities) $ 4 $ (4 ) $ 8 $ (4 ) $ (5 ) $ 1
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) Three Months Ended September 30, Nine Months Ended September 30, (in millions) 2018 2017 2018 2017 Balance at beginning of period $ 9 $ 3 $ 1 $ 5 Purchases, sales, issuances and settlements: Purchases — — 7 3 Settlements (1 ) (1 ) (2 ) (3 ) Total gains (losses) included on the Condensed Consolidated Balance Sheet — — 2 (3 ) Balance at end of period $ 8 $ 2 $ 8 $ 2
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 tables provide recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets. September 30, 2018 December 31, 2017 (in millions) Total Fair Value Level 1 Level 2 Level 3 Total Fair Value Level 1 Level 2 Level 3 Other equity securities $ 78 $ 78 $ — $ — $ 97 $ 97 $ — $ — Other debt securities 40 — 40 — 31 — 31 — Derivative assets 29 — — 29 27 — — 27 Total assets $ 147 $ 78 $ 40 $ 29 $ 155 $ 97 $ 31 $ 27
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) Three Months Ended September 30, Nine Months Ended September 30, (in millions) 2018 2017 2018 2017 Balance at beginning of period $ 44 $ 51 $ 27 $ 16 Purchases, sales, issuances and settlements: Purchases — — 49 52 Settlements (13 ) (11 ) (41 ) (27 ) Total losses included on the Condensed Consolidated Balance Sheet (2 ) (12 ) (6 ) (13 ) Balance at end of period $ 29 $ 28 $ 29 $ 28
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 tables provide recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets. September 30, 2018 (in millions) Total Fair Value Level 1 Level 3 Derivative assets $ 4 $ 4 $ — Derivative liabilities (153 ) — (153 ) Net (liabilities) assets $ (149 ) $ 4 $ (153 ) December 31, 2017 (in millions) Total Fair Value Level 1 Level 3 Other debt securities $ 1 $ 1 $ — Derivative assets 2 2 — Total assets 3 3 — Derivative liabilities (142 ) — (142 ) Net (liabilities) assets $ (139 ) $ 3 $ (142 )
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) Three Months Ended September 30, Nine Months Ended September 30, (in millions) 2018 2017 2018 2017 Balance at beginning of period $ (150 ) $ (145 ) $ (142 ) $ (187 ) Total (losses) gains and settlements (3 ) 22 (11 ) 64 Balance at end of period $ (153 ) $ (123 ) $ (153 ) $ (123 )

Variable Interest Entities (Tab

Variable Interest Entities (Tables)	9 Months Ended
	Sep. 30, 2018
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Schedule Of Variable Interest Entities	The following table summarizes the amounts and expiration dates of the credit facilities and associated restricted receivables described above. Duke Energy Duke Energy Duke Energy Duke Energy Carolinas Progress Florida (in millions) CRC DERF DEPR DEFR Expiration date December 2020 December 2020 February 2021 April 2021 Credit facility amount $ 325 $ 450 $ 300 $ 225 Amounts borrowed at September 30, 2018 325 450 300 225 Amounts borrowed at December 31, 2017 325 450 300 225 Restricted Receivables at September 30, 2018 504 795 635 456 Restricted Receivables at December 31, 2017 545 640 459 317
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Schedule Of Variable Interest Entities	The following tables summarize the impact of non-consolidated VIEs on the Condensed Consolidated Balance Sheets. September 30, 2018 Duke Energy Duke Duke Pipeline Commercial Other Energy Energy (in millions) Investments (a) Renewables VIEs Total Ohio Indiana Receivables from affiliated companies $ — $ — $ — $ — $ 56 $ 94 Investments in equity method unconsolidated affiliates 729 190 47 966 — — Total assets $ 729 $ 190 $ 47 $ 966 $ 56 $ 94 Other current liabilities — — 3 3 — — Deferred income taxes 14 — — 14 — — Other noncurrent liabilities — — 11 11 — — Total liabilities $ 14 $ — $ 14 $ 28 $ — $ — Net assets $ 715 $ 190 $ 33 $ 938 $ 56 $ 94 (a) See Pipeline Investments table below for further details regarding Investments in equity method unconsolidated affiliates. December 31, 2017 Duke Energy Duke Duke Pipeline Commercial Other Energy Energy (in millions) Investments Renewables VIEs 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
DEFPF [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Schedule Of Variable Interest Entities	The following table summarizes the impact of DEFPF on Duke Energy Florida's Condensed Consolidated Balance Sheets. (in millions) September 30, 2018 December 31, 2017 Receivables of VIEs $ 7 $ 4 Regulatory Assets: Current 52 51 Current Assets: Other 14 40 Other Noncurrent Assets: Regulatory assets 1,055 1,091 Current Liabilities: Other 3 10 Current maturities of long-term debt 53 53 Long-Term Debt 1,111 1,164
Commercial Renewables [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Schedule Of Variable Interest Entities	The table below presents material balances reported on Duke Energy's Condensed Consolidated Balance Sheets related to renewables VIEs. (in millions) September 30, 2018 December 31, 2017 Current Assets: Other $ 203 $ 174 Property, plant and equipment, cost 4,025 3,923 Accumulated depreciation and amortization (695 ) (591 ) Other Noncurrent Assets: Other 268 50 Current maturities of long-term debt 175 170 Long-Term Debt 1,604 1,700 Other Noncurrent Liabilities: Deferred income taxes — (148 ) Other Noncurrent Liabilities: Other 225 241
Pipeline Investments [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Schedule Of Variable Interest Entities	The table below presents Duke Energy's ownership interest and investment balances in these joint ventures. VIE Investment Amount (in millions) Ownership September 30, December 31, Entity Name Interest 2018 2017 ACP 47 % $ 704 $ 397 Sabal Trail (a) 7.5 % — 219 Constitution (b) 24 % 25 81 Total $ 729 $ 697 (a) At December 31, 2017 , Sabal Trail was considered a VIE due to having insufficient equity to finance their own activities without subordinated financial support. However, Sabal Trail is now a fully operational, well capitalized entity. As a result, Sabal Trail has sufficient equity to finance its own activities, and therefore, is no longer considered a VIE. Duke Energy's investment in Sabal Trail was $112 million at September 30, 2018 . (b) During the nine months ended September 30, 2018 , Duke Energy recorded an OTTI of $55 million related to Constitution within Equity in earnings of unconsolidated affiliates on Duke Energy's Condensed Consolidated Statements of Income. See Note 3 for additional information.
Cinergy Receivables [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [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 2018 2017 2018 2017 Anticipated credit loss ratio 0.5 % 0.5 % 0.3 % 0.3 % Discount rate 2.9 % 2.1 % 2.9 % 2.1 % Receivable turnover rate 13.6 % 13.5 % 10.9 % 10.7 % The following table shows the gross and net receivables sold. Duke Energy Ohio Duke Energy Indiana (in millions) September 30, 2018 December 31, 2017 September 30, 2018 December 31, 2017 Receivables sold $ 218 $ 273 $ 326 $ 312 Less: Retained interests 56 87 94 106 Net receivables sold $ 162 $ 186 $ 232 $ 206 The following table shows sales and cash flows related to receivables sold. Duke Energy Ohio Duke Energy Indiana Three Months Ended Nine Months Ended Three Months Ended Nine Months Ended September 30, September 30, September 30, September 30, (in millions) 2018 2017 2018 2017 2018 2017 2018 2017 Sales Receivables sold $ 450 $ 438 $ 1,478 $ 1,392 $ 754 $ 720 $ 2,140 $ 2,047 Loss recognized on sale 4 2 10 7 5 3 12 9 Cash flows Cash proceeds from receivables sold $ 449 $ 434 $ 1,499 $ 1,421 $ 743 $ 713 $ 2,140 $ 2,064 Collection fees received — 1 1 1 — — 1 1 Return received on retained interests 2 — 5 2 3 2 7 5

Revenue (Tables)

Revenue (Tables)	9 Months Ended
	Sep. 30, 2018
Revenue from Contract with Customer [Abstract]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction	Estimated remaining performance obligations are as follows: Remaining Performance Obligations (in millions) 2018 2019 2020 2021 2022 Thereafter Total Piedmont $ 18 $ 71 $ 70 $ 65 $ 64 $ 462 $ 750 Supplemental requirements contracts that include contracted blocks of energy and capacity at contractually fixed prices have the following estimated remaining performance obligations: Remaining Performance Obligations (in millions) 2018 2019 2020 2021 2022 Thereafter Total Progress Energy $ 24 $ 112 $ 121 $ 80 $ 82 $ 81 $ 500 Duke Energy Progress 2 9 9 9 9 18 56 Duke Energy Florida 22 103 112 71 73 63 444 Duke Energy Indiana 2 9 10 5 — — 26
Disaggregation of Revenue	Disaggregated revenues are presented as follows: Three Months Ended September 30, 2018 Duke Duke Duke Duke Duke (in millions) Duke Energy Progress Energy Energy Energy Energy By market or type of customer Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Electric Utilities and Infrastructure Residential $ 2,729 $ 823 $ 1,425 $ 572 $ 853 $ 203 $ 279 $ — General 1,763 635 800 373 427 112 218 — Industrial 835 352 246 177 69 33 202 — Wholesale 589 132 372 335 37 3 81 — Other revenues 225 109 134 90 44 20 29 — Total Electric Utilities and Infrastructure revenue from contracts with customers $ 6,141 $ 2,051 $ 2,977 $ 1,547 $ 1,430 $ 371 $ 809 $ — Gas Utilities and Infrastructure Residential $ 116 $ — $ — $ — $ — $ 59 $ — $ 57 Commercial 66 — — — — 20 — 46 Industrial 28 — — — — 3 — 24 Power Generation — — — — — — — 13 Other revenues 23 — — — — 1 — 22 Total Gas Utilities and Infrastructure revenue from contracts with customers $ 233 $ — $ — $ — $ — $ 83 $ — $ 162 Commercial Renewables Revenue from contracts with customers $ 61 $ — $ — $ — $ — $ — $ — $ — Other Revenue from contracts with customers $ 16 $ — $ — $ — $ — $ 12 $ — $ — Total revenue from contracts with customers $ 6,451 $ 2,051 $ 2,977 $ 1,547 $ 1,430 $ 466 $ 809 $ 162 Other revenue sources (a) $ 177 $ 39 $ 68 $ 35 $ 32 $ 3 $ 10 $ 10 Total revenues $ 6,628 $ 2,090 $ 3,045 $ 1,582 $ 1,462 $ 469 $ 819 $ 172 Nine Months Ended September 30, 2018 Duke Duke Duke Duke Duke (in millions) Duke Energy Progress Energy Energy Energy Energy By market or type of customer Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Electric Utilities and Infrastructure Residential $ 7,264 $ 2,263 $ 3,636 $ 1,540 $ 2,096 $ 564 $ 802 $ — General 4,619 1,608 2,109 972 1,137 318 584 — Industrial 2,235 893 678 481 197 96 567 — Wholesale 1,737 366 1,140 1,019 121 5 226 — Other revenues 558 261 359 222 137 57 66 — Total Electric Utilities and Infrastructure revenue from contracts with customers $ 16,413 $ 5,391 $ 7,922 $ 4,234 $ 3,688 $ 1,040 $ 2,245 $ — Gas Utilities and Infrastructure Residential $ 682 $ — $ — $ — $ — $ 236 $ — $ 446 Commercial 354 — — — — 97 — 257 Industrial 107 — — — — 13 — 93 Power Generation — — — — — — — 40 Other revenues 101 — — — — 13 — 88 Total Gas Utilities and Infrastructure revenue from contracts with customers $ 1,244 $ — $ — $ — $ — $ 359 $ — $ 924 Commercial Renewables Revenue from contracts with customers $ 141 $ — $ — $ — $ — $ — $ — $ — Other Revenue from contracts with customers $ 47 $ — $ — $ — $ — $ 36 $ — $ — Total Revenue from contracts with customers $ 17,845 $ 5,391 $ 7,922 $ 4,234 $ 3,688 $ 1,435 $ 2,245 $ 924 Other revenue sources (a) $ 561 $ 134 $ 197 $ 99 $ 92 $ 17 $ 43 $ 16 Total revenues $ 18,406 $ 5,525 $ 8,119 $ 4,333 $ 3,780 $ 1,452 $ 2,288 $ 940 (a) Other revenue sources include revenues from leases, derivatives and alternative revenue programs that are not considered revenues from contracts with customers. Alternative revenue programs in certain jurisdictions include regulatory mechanisms that periodically adjust for over or under collection of related revenues.
Schedule Of Unbilled Revenues With Restricted Receivables	Unbilled revenues are included within Receivables and Receivables of VIEs on the Condensed Consolidated Balance Sheets as shown in the following table. (in millions) September 30, 2018 December 31, 2017 Duke Energy $ 802 $ 944 Duke Energy Carolinas 278 342 Progress Energy 283 228 Duke Energy Progress 163 143 Duke Energy Florida 120 85 Duke Energy Ohio 2 4 Duke Energy Indiana 25 21 Piedmont 3 86 These receivables for unbilled revenues are shown in the table below. (in millions) September 30, 2018 December 31, 2017 Duke Energy Ohio $ 68 $ 104 Duke Energy Indiana 121 132

Common Stock (Tables)

Common Stock (Tables)	9 Months Ended
	Sep. 30, 2018
Equity [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 shares outstanding to the diluted weighted average number of common shares outstanding. Three Months Ended September 30, Nine Months Ended September 30, (in millions, except per-share amounts) 2018 2017 2018 2017 Income from continuing operations attributable to Duke Energy common stockholders excluding impact of participating securities $ 1,077 $ 954 $ 2,199 $ 2,356 Weighted average shares outstanding – basic 713 700 705 700 Equity Forwards 1 — 1 — Weighted average shares outstanding – diluted 714 700 706 700 Earnings per share from continuing operations attributable to Duke Energy common stockholders Basic $ 1.51 $ 1.36 $ 3.12 $ 3.37 Diluted $ 1.51 $ 1.36 $ 3.11 $ 3.37 Potentially dilutive items excluded from the calculation (a) 2 2 2 2 Dividends declared per common share $ 0.9275 $ 0.89 $ 2.7075 $ 2.60 (a) Performance stock awards were not included in the dilutive securities calculation because the performance measures related to the awards had not been met.

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule Of Stock-Based Compensation Expense	The following table presents information related to Duke Energy's stock–based compensation. Three Months Ended Nine Months Ended September 30, September 30, (in millions) 2018 2017 2018 2017 Restricted stock unit awards $ 10 $ 10 $ 32 $ 30 Performance awards 13 7 27 20 Pretax stock-based compensation cost $ 23 $ 17 $ 59 $ 50 Stock-based compensation cost capitalized $ 1 $ 1 $ 3 $ 2 Stock-based compensation expense $ 22 $ 16 $ 56 $ 48 Tax benefit associated with stock-based compensation expense $ 5 $ 6 $ 13 $ 18

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	9 Months Ended
	Sep. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan Disclosures	The following table includes employer 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 Three Months Ended September 30, 2018 $ 49 $ 15 $ 13 $ 9 $ 4 $ — $ 3 $ 4 2017 43 14 12 9 4 1 2 2 Nine Months Ended September 30, 2018 $ 167 $ 53 $ 45 $ 31 $ 14 $ 2 $ 8 $ 10 2017 147 49 42 30 13 3 7 5
Qualified Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Schedule of Defined Benefit Plans Disclosures	The following table presents contributions made by the Duke Energy Registrants to their qualified defined benefit pension plans during the nine months ended September 30, 2018 . Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Indiana Contributions $ 141 $ 46 $ 45 $ 25 $ 20 $ 8
Components of Net Periodic Pension Costs	The following tables include the components of net periodic pension costs for qualified pension plans. Three Months Ended September 30, 2018 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Service cost $ 47 $ 15 $ 13 $ 7 $ 5 $ 2 $ 2 $ 2 Interest cost on projected benefit obligation 74 18 24 10 13 4 6 3 Expected return on plan assets (140 ) (37 ) (45 ) (21 ) (23 ) (7 ) (10 ) (6 ) Amortization of actuarial loss 33 7 11 6 6 1 2 3 Amortization of prior service credit (8 ) (2 ) (1 ) — — — — (3 ) Net periodic pension costs $ 6 $ 1 $ 2 $ 2 $ 1 $ — $ — $ (1 ) Three Months Ended September 30, 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 $ 40 $ 12 $ 12 $ 6 $ 5 $ 1 $ 2 $ 3 Interest cost on projected benefit obligation 82 20 25 12 13 4 7 3 Expected return on plan assets (136 ) (35 ) (43 ) (21 ) (21 ) (7 ) (11 ) (6 ) Amortization of actuarial loss 36 8 14 6 7 1 3 3 Amortization of prior service credit (6 ) (2 ) (1 ) — — — — (1 ) Other 2 — 1 — — — — — Net periodic pension costs $ 18 $ 3 $ 8 $ 3 $ 4 $ (1 ) $ 1 $ 2 Nine Months Ended September 30, 2018 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Service cost $ 137 $ 45 $ 39 $ 22 $ 16 $ 4 $ 7 $ 6 Interest cost on projected benefit obligation 224 54 70 31 38 13 18 9 Expected return on plan assets (420 ) (111 ) (133 ) (63 ) (69 ) (21 ) (31 ) (18 ) Amortization of actuarial loss 99 21 33 16 18 3 6 9 Amortization of prior service credit (24 ) (6 ) (3 ) (1 ) (1 ) — — (9 ) Net periodic pension costs $ 16 $ 3 $ 6 $ 5 $ 2 $ (1 ) $ — $ (3 ) Nine Months Ended September 30, 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 $ 120 $ 36 $ 36 $ 18 $ 15 $ 3 $ 6 $ 9 Interest cost on projected benefit obligation 246 60 75 36 39 14 21 9 Expected return on plan assets (408 ) (106 ) (129 ) (63 ) (63 ) (21 ) (33 ) (18 ) Amortization of actuarial loss 108 24 42 18 21 3 9 9 Amortization of prior service credit (18 ) (6 ) (3 ) — — — — (3 ) Other 6 — 3 1 — — — 1 Net periodic pension costs $ 54 $ 8 $ 24 $ 10 $ 12 $ (1 ) $ 3 $ 7
Non-Qualified Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Components of Net Periodic Pension Costs	The following tables include the components of net periodic pension costs for non-qualified pension plans for registrants with non-qualified pension costs. Three Months Ended September 30, 2018 Duke Duke Duke Duke Energy Progress Energy Energy (in millions) Energy Carolinas Energy Progress Florida Interest cost on projected benefit obligation $ 3 $ — $ 1 $ — $ — Amortization of actuarial loss 2 — — — — Net periodic pension costs $ 5 $ — $ 1 $ — $ — Three Months Ended September 30, 2017 Duke Duke Duke Duke Energy Progress Energy Energy (in millions) Energy Carolinas Energy Progress Florida Interest cost on projected benefit obligation $ 4 $ — $ 1 $ 1 $ 1 Amortization of actuarial loss 2 — 1 — — Net periodic pension costs $ 6 $ — $ 2 $ 1 $ 1 Nine Months Ended September 30, 2018 Duke Duke Duke Duke Energy Progress Energy Energy (in millions) Energy Carolinas Energy Progress Florida Service cost $ 1 $ 1 $ — $ — $ — Interest cost on projected benefit obligation 9 — 3 1 1 Amortization of actuarial loss 6 — — — — Amortization of prior service (credit) cost (1 ) — 1 — — Net periodic pension costs $ 15 $ 1 $ 4 $ 1 $ 1 Nine Months Ended September 30, 2017 Duke Duke Duke Duke Energy Progress Energy Energy (in millions) Energy Carolinas Energy Progress Florida Interest cost on projected benefit obligation $ 10 $ 1 $ 3 $ 2 $ 2 Amortization of actuarial loss 6 — 3 — — Net periodic pension costs $ 16 $ 1 $ 6 $ 2 $ 2
Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Components of Net Periodic Pension Costs	The following tables include the components of net periodic other post-retirement benefit costs. Three Months Ended September 30, 2018 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 $ — $ — $ — $ — $ — $ — $ — Interest cost on accumulated post-retirement benefit obligation 7 2 3 2 1 — 1 — Expected return on plan assets (4 ) (2 ) — — — — — — Amortization of actuarial loss 2 1 — — — — 1 — Amortization of prior service credit (5 ) (1 ) (2 ) — (1 ) — — — Net periodic other post-retirement benefit costs $ 2 $ — $ 1 $ 2 $ — $ — $ 2 $ — Three Months Ended September 30, 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 $ 1 $ — $ — $ — $ — $ — $ — $ — Interest cost on accumulated post-retirement benefit obligation 9 2 4 2 2 — 1 — Expected return on plan assets (3 ) (2 ) — — — — — — Amortization of actuarial loss 2 — 5 3 2 — — — Amortization of prior service credit (29 ) (2 ) (21 ) (14 ) (8 ) — — — Net periodic other post-retirement benefit costs $ (20 ) $ (2 ) $ (12 ) $ (9 ) $ (4 ) $ — $ 1 $ — Nine Months Ended September 30, 2018 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Service cost $ 5 $ 1 $ — $ — $ — $ — $ — $ — Interest cost on accumulated post-retirement benefit obligation 21 5 9 5 4 1 3 — Expected return on plan assets (10 ) (6 ) — — — — — — Amortization of actuarial loss 5 2 1 — — — 3 — Amortization of prior service credit (15 ) (3 ) (6 ) — (4 ) — — (1 ) Net periodic other post-retirement benefit costs $ 6 $ (1 ) $ 4 $ 5 $ — $ 1 $ 6 $ (1 ) Nine Months Ended September 30, 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 $ 3 $ — $ — $ — $ — $ — $ — $ — Interest cost on accumulated post-retirement benefit obligation 27 6 11 6 6 — 1 — Expected return on plan assets (10 ) (6 ) — — — — — — Amortization of actuarial loss (gain) 6 (2 ) 15 9 6 (1 ) — — Amortization of prior service credit (87 ) (6 ) (63 ) (41 ) (23 ) — — — Net periodic other post-retirement benefit costs $ (61 ) $ (8 ) $ (37 ) $ (26 ) $ (11 ) $ (1 ) $ 1 $ —

Income Taxes (Tables)

Income Taxes (Tables)	9 Months Ended
	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Summary of Effective Tax Rates	The effective tax rates from continuing operations for each of the Duke Energy Registrants are included in the following table. Three Months Ended Nine Months Ended September 30, September 30, 2018 2017 2018 2017 Duke Energy 13.7 % 27.6 % 17.0 % 30.4 % Duke Energy Carolinas 22.6 % 32.9 % 22.3 % 34.1 % Progress Energy 18.8 % 29.1 % 17.0 % 31.9 % Duke Energy Progress 20.6 % 31.7 % 18.4 % 32.4 % Duke Energy Florida 15.0 % 34.8 % 16.3 % 36.1 % Duke Energy Ohio 16.0 % 33.3 % 16.0 % 34.4 % Duke Energy Indiana 22.7 % 38.3 % 24.7 % 39.0 % Piedmont 34.4 % 47.6 % 20.6 % 36.1 %

Organization and Basis of Pre_4

Organization and Basis of Presentation (Other Current Assets) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Current Assets, Other [Member]
Organization And Basis Of Presentation [Line Items]
Tax receivable	$ 655	$ 260

Organization and Basis of Pre_5

Organization and Basis of Presentation (Schedule of Cash and Cash Equivalents) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Current Assets
Cash and cash equivalents	$ 303	$ 358
Other	139	138
Other Noncurrent Assets
Other	7	9
Total cash, cash equivalents and restricted cash	449	505	$ 427	$ 541
Progress Energy [Member]
Current Assets
Cash and cash equivalents	43	40
Other	14	40
Other Noncurrent Assets
Other	6	7
Total cash, cash equivalents and restricted cash	63	87	56	110
Duke Energy Florida [Member]
Current Assets
Cash and cash equivalents	20	13
Other	14	40
Other Noncurrent Assets
Total cash, cash equivalents and restricted cash	$ 34	$ 53	$ 28	$ 69

Organization and Basis of Pre_6

Organization and Basis of Presentation (Schedule of Inventory) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Public Utilities, Inventory [Line Items]
Inventory	$ 3,140	$ 3,250
Materials and supplies [Member]
Public Utilities, Inventory [Line Items]
Inventory	2,283	2,293
Coal [Member]
Public Utilities, Inventory [Line Items]
Inventory	515	603
Natural gas, oil and other fuel [Member]
Public Utilities, Inventory [Line Items]
Inventory	342	354
Duke Energy Carolinas [Member]
Public Utilities, Inventory [Line Items]
Inventory	976	971
Duke Energy Carolinas [Member] | Materials and supplies [Member]
Public Utilities, Inventory [Line Items]
Inventory	758	744
Duke Energy Carolinas [Member] | Coal [Member]
Public Utilities, Inventory [Line Items]
Inventory	176	192
Duke Energy Carolinas [Member] | Natural gas, oil and other fuel [Member]
Public Utilities, Inventory [Line Items]
Inventory	42	35
Progress Energy [Member]
Public Utilities, Inventory [Line Items]
Inventory	1,473	1,592
Progress Energy [Member] | Materials and supplies [Member]
Public Utilities, Inventory [Line Items]
Inventory	1,071	1,118
Progress Energy [Member] | Coal [Member]
Public Utilities, Inventory [Line Items]
Inventory	187	255
Progress Energy [Member] | Natural gas, oil and other fuel [Member]
Public Utilities, Inventory [Line Items]
Inventory	215	219
Duke Energy Progress [Member]
Public Utilities, Inventory [Line Items]
Inventory	956	1,017
Duke Energy Progress [Member] | Materials and supplies [Member]
Public Utilities, Inventory [Line Items]
Inventory	748	774
Duke Energy Progress [Member] | Coal [Member]
Public Utilities, Inventory [Line Items]
Inventory	99	139
Duke Energy Progress [Member] | Natural gas, oil and other fuel [Member]
Public Utilities, Inventory [Line Items]
Inventory	109	104
Duke Energy Florida [Member]
Public Utilities, Inventory [Line Items]
Inventory	517	574
Duke Energy Florida [Member] | Materials and supplies [Member]
Public Utilities, Inventory [Line Items]
Inventory	323	343
Duke Energy Florida [Member] | Coal [Member]
Public Utilities, Inventory [Line Items]
Inventory	88	116
Duke Energy Florida [Member] | Natural gas, oil and other fuel [Member]
Public Utilities, Inventory [Line Items]
Inventory	106	115
Duke Energy Ohio [Member]
Public Utilities, Inventory [Line Items]
Inventory	135	133
Duke Energy Ohio [Member] | Materials and supplies [Member]
Public Utilities, Inventory [Line Items]
Inventory	87	82
Duke Energy Ohio [Member] | Coal [Member]
Public Utilities, Inventory [Line Items]
Inventory	14	17
Duke Energy Ohio [Member] | Natural gas, oil and other fuel [Member]
Public Utilities, Inventory [Line Items]
Inventory	34	34
Duke Energy Indiana [Member]
Public Utilities, Inventory [Line Items]
Inventory	434	450
Duke Energy Indiana [Member] | Materials and supplies [Member]
Public Utilities, Inventory [Line Items]
Inventory	294	309
Duke Energy Indiana [Member] | Coal [Member]
Public Utilities, Inventory [Line Items]
Inventory	138	139
Duke Energy Indiana [Member] | Natural gas, oil and other fuel [Member]
Public Utilities, Inventory [Line Items]
Inventory	2	2
Piedmont Natural Gas [Member]
Public Utilities, Inventory [Line Items]
Inventory	51	66
Piedmont Natural Gas [Member] | Materials and supplies [Member]
Public Utilities, Inventory [Line Items]
Inventory	1	2
Piedmont Natural Gas [Member] | Natural gas, oil and other fuel [Member]
Public Utilities, Inventory [Line Items]
Inventory	$ 50	$ 64

Organization and Basis of Pre_7

Organization and Basis of Presentation (Schedule of Excise Taxes) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	$ 114	$ 107	$ 308	$ 289
Duke Energy Carolinas [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	10	9	27	27
Progress Energy [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	71	67	181	168
Duke Energy Progress [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	5	5	15	14
Duke Energy Florida [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	66	62	166	154
Duke Energy Ohio [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	26	24	81	75
Duke Energy Indiana [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	6	6	17	16
Piedmont Natural Gas [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	$ 1	$ 1	$ 2	$ 3

Organization and Basis of Pre_8

Organization and Basis of Presentation (New Accounting Standards) (Details) - Accounting Standards Update 2017-07 [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating income and expenses, net [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New accounting pronouncement, quantified affect	$ 156	$ 131	$ 96
Nonoperating income and expenses, net [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New accounting pronouncement, quantified affect	$ 156	$ 131	$ 96

Business Segments (Narrative) (

Business Segments (Narrative) (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)segment	Sep. 30, 2017USD ($)
Segment Reporting Information [Line Items]
Pretax loss on disposal	$ (10)	$ (6)	$ 87	$ (24)
Operation, maintenance and other	1,584	1,476	4,592	4,385
Duke Energy Ohio [Member]
Segment Reporting Information [Line Items]
Pretax loss on disposal		(1)	106	(1)
Operation, maintenance and other	$ 76	$ 125	$ 337	$ 388
Number of reportable segments | segment			2
Beckjord [Member]
Segment Reporting Information [Line Items]
Pretax loss on disposal			$ 106
Operation, maintenance and other			$ 1
National Methanol Company [Member]
Segment Reporting Information [Line Items]
Ownership percentage	17.50%		17.50%

Business Segments (Business Seg

Business Segments (Business Segment Data) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Segment Reporting Information [Line Items]
Operating revenues	$ 6,628	$ 6,482	$ 18,406	$ 17,766
Segment income (loss)	1,078	956	2,203	2,360
Add back noncontrolling interests	(16)	1	(12)	5
Income (Loss) From Discontinued Operations, net of tax	4	(2)	(1)	(4)
Net Income	1,066	955	2,190	2,361
Net income (attributable to parent)	1,082	954	2,202	2,356
Segment assets	143,165		143,165		$ 137,914
Electric Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Operating revenues	6,253	6,122	16,783	16,211
Gas Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Operating revenues	232	249	1,229	1,175
Commercial Renewables [Member]
Segment Reporting Information [Line Items]
Operating revenues	127	95	347	333
Total Reportable Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	6,612	6,466	18,359	17,719
Other [Member]
Segment Reporting Information [Line Items]
Operating revenues	16	16	47	47
Operating Segments [Member]
Segment Reporting Information [Line Items]
Segment income (loss)	1,122	990	2,649	2,565
Segment assets	139,865		139,865
Operating Segments [Member] | Electric Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Operating revenues	6,260	6,129	16,806	16,234
Segment income (loss)	1,167	1,020	2,492	2,384
Segment assets	123,847		123,847
Operating Segments [Member] | Gas Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Operating revenues	256	272	1,301	1,243
Segment income (loss)	17	19	161	179
Segment assets	11,806		11,806
Operating Segments [Member] | Commercial Renewables [Member]
Segment Reporting Information [Line Items]
Operating revenues	127	95	347	333
Segment income (loss)	(62)	(49)	(4)	2
Segment assets	4,212		4,212
Operating Segments [Member] | Total Reportable Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	6,643	6,496	18,454	17,810
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues	(49)	(49)	(149)	(147)
Segment assets	185		185
Intersegment Eliminations [Member] | Electric Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Operating revenues	7	7	23	23
Intersegment Eliminations [Member] | Gas Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Operating revenues	24	23	72	68
Intersegment Eliminations [Member] | Total Reportable Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	31	30	95	91
Intersegment Eliminations [Member] | Other [Member]
Segment Reporting Information [Line Items]
Operating revenues	18	19	54	56
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Segment income (loss)	(44)	(34)	(446)	(205)
Segment assets	3,115		3,115
Corporate, Non-Segment [Member] | Other [Member]
Segment Reporting Information [Line Items]
Operating revenues	34	35	101	103
Duke Energy Ohio [Member]
Segment Reporting Information [Line Items]
Operating revenues	469	471	1,452	1,426
Segment income (loss)	100	56	121	128
Income (Loss) From Discontinued Operations, net of tax		(1)		(1)
Net Income				127
Net income (attributable to parent)	100	55	121	127
Segment assets	8,296		8,296		$ 7,875
Duke Energy Ohio [Member] | Electric Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Operating revenues	373	371	1,055	1,036
Duke Energy Ohio [Member] | Gas Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Operating revenues	84	90	361	360
Duke Energy Ohio [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	457	461	1,416	1,396
Segment income (loss)	97	64	221	152
Segment assets	8,259		8,259
Duke Energy Ohio [Member] | Operating Segments [Member] | Electric Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Segment income (loss)	85	50	157	96
Segment assets	5,484		5,484
Duke Energy Ohio [Member] | Operating Segments [Member] | Gas Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Segment income (loss)	12	14	64	56
Segment assets	2,775		2,775
Duke Energy Ohio [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Segment assets	(2)		(2)
Duke Energy Ohio [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues	12	10	36	30
Segment income (loss)	3	$ (8)	(100)	$ (24)
Segment assets	$ 39		$ 39

Regulatory Matters (Narrative)

Regulatory Matters (Narrative) (Details) customer in Millions, $ in Millions	Oct. 03, 2018	Jul. 31, 2018USD ($)	Sep. 30, 2018USD ($)customer	Jul. 31, 2018USD ($)	May 31, 2018USD ($)	Feb. 28, 2018USD ($)	Jun. 30, 2017USD ($)	Dec. 31, 2015USD ($)	Sep. 30, 2018USD ($)customer	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)customerMW	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)	Jun. 30, 2018USD ($)
Public Utilities, General Disclosures [Line Items]
Operation, maintenance and other									$ 1,584	$ 1,476	$ 4,592	$ 4,385
Impairment and related charges									124	207	339	216
Loss before income taxes									(1,230)	(1,321)	(2,640)	(3,400)
Accretion expense											319
Public utilities, property, plant and equipment, net			$ 89,865						89,865		89,865		$ 86,391
Regulated operating revenue, electric, non-nuclear									6,216	6,091	$ 16,678	16,122
Generation Facilities To Be Retired [Member]
Public Utilities, General Disclosures [Line Items]
Capacity (in MW) | MW											1,631
Public utilities, property, plant and equipment, net			$ 355						$ 355		$ 355
Atlantic Coast Pipeline (ACP) [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage			47.00%						47.00%		47.00%
Long-term purchase commitment, period											20 years
Sabal Trail Transmission Pipeline [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost			$ 3,200						$ 3,200		$ 3,200
Joint owner ownership percentage			7.50%						7.50%		7.50%
Long-term purchase commitment, period											25 years
Constitution Pipeline [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage			24.00%						24.00%		24.00%
Estimated contributions			$ 229						$ 229		$ 229
Equity method investment, OTTI											$ 55
Dominion Resources [Member] | Atlantic Coast Pipeline (ACP) [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage			48.00%						48.00%		48.00%
Southern Company Gas [Member] | Atlantic Coast Pipeline (ACP) [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage			5.00%						5.00%		5.00%
Spectra Energy Partners [Member] | Sabal Trail Transmission Pipeline [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage			50.00%						50.00%		50.00%
NextEra Energy [Member] | Sabal Trail Transmission Pipeline [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage			42.50%						42.50%		42.50%
Williams Partners L.P. [Member] | Constitution Pipeline [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage			41.00%						41.00%		41.00%
Minimum [Member] | Atlantic Coast Pipeline (ACP) [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost			$ 6,500						$ 6,500		$ 6,500			$ 6,000
Maximum [Member] | Atlantic Coast Pipeline (ACP) [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost			$ 7,000						$ 7,000		$ 7,000			$ 6,500
Hurricane Florence Storm Damage [Member]
Public Utilities, General Disclosures [Line Items]
Customers experiencing outages | customer			1.8						1.8		1.8
Operation, maintenance and other			$ 455
Estimated capital cost			85						$ 85		$ 85
FERC 494 Refund of Regional Transmission Enhancement Projects [Member] | FERC [Member]
Public Utilities, General Disclosures [Line Items]
Customer refundable fees, refund payments											47
Progress Energy Merger FERC Mitigation [Member] | FERC [Member]
Public Utilities, General Disclosures [Line Items]
Penalty assessed											3.5
Duke Energy Carolinas [Member]
Public Utilities, General Disclosures [Line Items]
Operation, maintenance and other									514	494	1,464	1,472
Impairment and related charges									1		191
Loss before income taxes									(641)	(695)	(1,204)	(1,531)
Accretion expense											133
Public utilities, property, plant and equipment, net			28,550						28,550		28,550		27,876
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			$ 650						$ 650		650
Approved rate increase (decrease), amount											$ 600
Joint owner ownership percentage			13.00%						13.00%		13.00%
Duke Energy Carolinas [Member] | Hurricane Florence Storm Damage [Member]
Public Utilities, General Disclosures [Line Items]
Operation, maintenance and other			$ 35
Estimated capital cost			10						$ 10		$ 10
Duke Energy Carolinas [Member] | 2017 North Carolina Rate Case [Member] | NCUC [Member]
Public Utilities, General Disclosures [Line Items]
Operation, maintenance and other						$ 4
Requested rate increase (decrease), amount											$ 647
Requested rate increase, percentage											13.60%
Requested return on equity, percent											9.90%
Public utilities, requested equity capital structure, percentage											52.00%
Public utilities, requested debt capital structure, percentage											48.00%
Penalty assessed											$ 70
Estimated future coal ash costs			201						201		201
Utilities operating expenses, impairments									150
Loss before income taxes											14
Duke Energy Carolinas [Member] | 2017 North Carolina Rate Case [Member] | NCUC [Member] | Asset retirement obligations - coal ash [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			554						554		$ 554
Regulatory asset, amortization period											5 years
Duke Energy Carolinas [Member] | 2017 North Carolina Rate Case [Member] | NCUC [Member] | Deferred Project Costs [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			347						347		$ 347
Regulatory asset, amortization period											12 years
Duke Energy Carolinas [Member] | 2017 North Carolina Rate Case [Member] | William State Lee Iii Nuclear Station [Member] | NCUC [Member]
Public Utilities, General Disclosures [Line Items]
Utilities operating expenses, impairments											$ 29
Duke Energy Carolinas [Member] | FERC Formula Rate Matter [Member] | FERC [Member]
Public Utilities, General Disclosures [Line Items]
Customer refundable fees, refund payments											25
Duke Energy Carolinas [Member] | 2018 Sale of Hydro Plants [Member] | NCUC [Member]
Public Utilities, General Disclosures [Line Items]
Estimated loss on asset sale					$ 40
Duke Energy Carolinas [Member] | 2018 PSCSC Petitions [Member] | PSCSC [Member]
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease), amount				$ 33
Progress Energy [Member]
Public Utilities, General Disclosures [Line Items]
Operation, maintenance and other									680	588	1,913	1,697
Impairment and related charges									1	135	34	137
Loss before income taxes									(500)	(484)	(1,096)	(1,205)
Accretion expense											168
Public utilities, property, plant and equipment, net			33,558						33,558		33,558		31,887
Duke Energy Progress [Member]
Public Utilities, General Disclosures [Line Items]
Operation, maintenance and other									431	365	1,187	1,069
Impairment and related charges											33
Loss before income taxes									(272)	(360)	(652)	(809)
Accretion expense											145
Public utilities, property, plant and equipment, net			19,995						19,995		$ 19,995		19,101
Duke Energy Progress [Member] | Asheville Plant [Member] | Generation Facilities To Be Retired [Member]
Public Utilities, General Disclosures [Line Items]
Capacity (in MW) | MW											376
Public utilities, property, plant and equipment, net			352						352		$ 352		385
Duke Energy Progress [Member] | Hurricane Florence Storm Damage [Member]
Public Utilities, General Disclosures [Line Items]
Operation, maintenance and other			420
Estimated capital cost			75						75		75
Duke Energy Progress [Member] | 2017 North Carolina Rate Case [Member] | NCUC [Member]
Public Utilities, General Disclosures [Line Items]
Requested rate increase (decrease), amount											$ 477
Requested rate increase, percentage											14.90%
Requested return on equity, percent											9.90%
Public utilities, requested equity capital structure, percentage											52.00%
Public utilities, requested debt capital structure, percentage											48.00%
Penalty assessed											$ 30
Estimated future coal ash costs			129						129		129
Utilities operating expenses, impairments													25
Requested rate increase (decrease), amended amount											$ 420
Requested rate increase (decrease) amended, percentage											13.00%
Estimated storm costs - capital and operation maintenance			116						116		$ 116
Loss before income taxes											68
Duke Energy Progress [Member] | 2017 North Carolina Rate Case [Member] | NCUC [Member] | Asset retirement obligations - coal ash [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			234						234		$ 234
Regulatory asset, amortization period											5 years
Excluded deferred coal ash costs			9.5						9.5		$ 9.5
Duke Energy Progress [Member] | 2017 North Carolina Rate Case [Member] | NCUC [Member] | Storm Costs [Member]
Public Utilities, General Disclosures [Line Items]
Requested rate increase (decrease), amount											$ 80
Regulatory asset, amortization period											5 years
Approved rate increase (decrease), amount											$ 51
Duke Energy Progress [Member] | 2016 South Carolina Rate Case Settlement [Member] | PSCSC [Member]
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease), amount											$ 56
Accretion expense													18.5
Approved return on equity percentage											10.10%
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											$ 38
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											18.5
Duke Energy Progress [Member] | Western Carolinas Modernization Plan [Member] | NCUC [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost			893						893		$ 893
Regulatory asset, amortization period											10 years
Duke Energy Progress [Member] | Shearon Harris Nuclear Expansion [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets													47
Regulatory asset, amortization period											8 years
Wholesale debt return amortization period											15 years
Duke Energy Progress [Member] | 2018 PSCSC Petitions [Member] | PSCSC [Member]
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease), amount				$ 20
Duke Energy Progress [Member] | FERC Form 1 Reporting Matter [Member] | FERC [Member]
Public Utilities, General Disclosures [Line Items]
Customer refundable fees, refund payments											$ 14
Duke Energy Florida [Member]
Public Utilities, General Disclosures [Line Items]
Operation, maintenance and other									245	220	719	623
Impairment and related charges									1	135	1	137
Loss before income taxes									(286)	(184)	(614)	(576)
Accretion expense											23
Public utilities, property, plant and equipment, net			13,561						13,561		13,561		12,783
Duke Energy Florida [Member] | Storm Costs [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			258						258		258
Duke Energy Florida [Member] | Citrus County Station [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost of new utility plant, including AFUDC			$ 1,500						$ 1,500		$ 1,500
Duke Energy Florida [Member] | Storm Restoration Cost Recovery [Member] | FPSC [Member]
Public Utilities, General Disclosures [Line Items]
Customers experiencing outages | customer			1.3						1.3		1.3
Estimated storm costs - capital and operation maintenance			$ 510						$ 510		$ 510
Duke Energy Florida [Member] | Federal Tax Act Impacts [Member] | FPSC [Member]
Public Utilities, General Disclosures [Line Items]
Requested rate increase (decrease), amount											(151)
Tax act annual savings											84
Tax act excess deferred tax amortization requested rate decrease, amount											67
Duke Energy Florida [Member] | Federal Tax Act Impacts Revenue Requirement [Member] | FPSC [Member]
Public Utilities, General Disclosures [Line Items]
Requested rate increase (decrease), amount											201
Duke Energy Florida [Member] | Federal Tax Act Impacts Revenue Requirement [Member] | FPSC [Member] | Storm Costs [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			151						151		151
Duke Energy Florida [Member] | Federal Tax Act Impacts Revenue Requirement [Member] | Crystal River Units 3 and 4 [Member] | FPSC [Member]
Public Utilities, General Disclosures [Line Items]
Public utilities, property, plant and equipment, net			50						50		50
Duke Energy Florida [Member] | Citrus County Combined Cycle Facility [Member]
Public Utilities, General Disclosures [Line Items]
Requested rate increase (decrease), amount											200
Duke Energy Florida [Member] | 2017 Second Revised and Restated Stipulation and Settlement Agreement [Member] | Hamilton Project [Member] | FPSC [Member]
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease), amount		$ (15.2)
Duke Energy Florida [Member] | 2017 Second Revised and Restated Stipulation and Settlement Agreement [Member] | Columbia Project [Member] | FPSC [Member]
Public Utilities, General Disclosures [Line Items]
Requested rate increase (decrease), amount		$ (14)
Duke Energy Ohio [Member]
Public Utilities, General Disclosures [Line Items]
Operation, maintenance and other									76	125	337	388
Impairment and related charges												1
Loss before income taxes									(119)	(84)	(144)	(195)
Accretion expense											3
Public utilities, property, plant and equipment, net			6,493						6,493		6,493		6,041
Regulated operating revenue, electric, non-nuclear									373	371	1,055	1,036
Duke Energy Ohio [Member] | 2017 Ohio Electric Base Rate Case [Member] | PUCO [Member]
Public Utilities, General Disclosures [Line Items]
Requested rate increase (decrease), amount											$ 15
Requested return on equity, percent											10.40%
Public utilities, requested equity capital structure, percentage											50.75%
Public utilities, requested debt capital structure, percentage											49.25%
Approved rate increase (decrease), amount											$ (20)
Requested rate increase (decrease), amended amount											$ (19)
Requested rate increase (decrease) amended, percentage											9.84%
Duke Energy Ohio [Member] | 2017 Ohio Electric Base Rate Case [Member] | PUCO [Member] | Minimum [Member]
Public Utilities, General Disclosures [Line Items]
Requested rate increase (decrease), amount											$ (18)
Requested return on equity, percent											9.22%
Duke Energy Ohio [Member] | 2017 Ohio Electric Base Rate Case [Member] | PUCO [Member] | Maximum [Member]
Public Utilities, General Disclosures [Line Items]
Requested rate increase (decrease), amount											$ (29)
Requested return on equity, percent											10.24%
Requested rider revenue increase											$ 10
Duke Energy Ohio [Member] | Energy Efficiency Cost Recovery [Member] | PUCO [Member]
Public Utilities, General Disclosures [Line Items]
Regulated operating revenue, electric, non-nuclear								$ 20
Duke Energy Ohio [Member] | Energy Efficiency Cost Recovery [Member] | PUCO [Member] | Maximum [Member]
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease), amount											38
Approved rate increase (decrease), one-time waiver amount											56
Duke Energy Ohio [Member] | Natural Gas Pipeline Extension [Member] | OPSB [Member] | Minimum [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost excluding AFUDC			163						163		163
Duke Energy Ohio [Member] | Natural Gas Pipeline Extension [Member] | OPSB [Member] | Maximum [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost excluding AFUDC			245						245		245
Duke Energy Ohio [Member] | Duke Energy Kentucky Electric Rate Case [Member] | KPSC [Member]
Public Utilities, General Disclosures [Line Items]
Requested rate increase (decrease), amount											$ 49
Requested rate increase, percentage											15.00%
Approved rate increase (decrease), amount											$ 8.4
Requested rate increase (decrease), amended amount											$ (30.1)
Requested rate increase (decrease) amended, percentage											9.00%
Approved return on equity percentage											9.725%
Public utilities, approved equity capital structure, percentage											49.00%
Total allocable capitalization			650						650		$ 650
Incremental rider revenue											13
Duke Energy Ohio [Member] | Duke Energy Kentucky Gas Base Rate Case [Member] | KPSC [Member]
Public Utilities, General Disclosures [Line Items]
Requested rate increase (decrease), amount											$ 10.5
Requested rate increase, percentage											11.10%
Requested rate increase (decrease), amended amount											$ (5.2)
Duke Energy Indiana [Member]
Public Utilities, General Disclosures [Line Items]
Operation, maintenance and other									198	177	576	546
Impairment and related charges									30		30
Loss before income taxes									(154)	(196)	(421)	(521)
Accretion expense											22
Public utilities, property, plant and equipment, net			10,467						10,467		10,467		10,286
Duke Energy Indiana [Member] | Benton County Wind Farm Dispute [Member]
Public Utilities, General Disclosures [Line Items]
Litigation settlement, amount awarded to other party							$ 29
Duke Energy Indiana [Member] | Edwardsport Integrated Gasification Combined Cycle Plant [Member]
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease), amount											(10)
Impairment and related charges									32
Decrease in regulatory assets											$ 30
Duke Energy Indiana [Member] | FERC Transmission Rates [Member] | FERC [Member]
Public Utilities, General Disclosures [Line Items]
Approved return on equity percentage											12.38%
Approved return on equity percentage adder											0.50%
Duke Energy Indiana [Member] | FERC Complaint [Member] | FERC [Member]
Public Utilities, General Disclosures [Line Items]
Requested return on equity, percent											8.67%
Duke Energy Indiana [Member] | FERC Complaint 1 [Member] | FERC [Member]
Public Utilities, General Disclosures [Line Items]
Approved return on equity percentage											10.32%
Duke Energy Indiana [Member] | FERC Complaint 2 [Member] | FERC [Member]
Public Utilities, General Disclosures [Line Items]
Requested return on equity, percent											9.70%
Duke Energy Indiana [Member] | Federal Tax Act Impacts Tranche 1 [Member] | IURC [Member]
Public Utilities, General Disclosures [Line Items]
Requested rate increase (decrease), amount											$ (7)
Duke Energy Indiana [Member] | Federal Tax Act Impacts Tranche 2 [Member] | IURC [Member]
Public Utilities, General Disclosures [Line Items]
Requested rate increase (decrease), amount											(35)
Piedmont Natural Gas [Member]
Public Utilities, General Disclosures [Line Items]
Operation, maintenance and other									85	73	252	226
Impairment and related charges												7
Loss before income taxes									32	$ 21	(102)	$ (119)
Public utilities, property, plant and equipment, net			5,712						5,712		5,712		$ 5,246
Piedmont Natural Gas [Member] | NCUC IMR Petition filed October 2018 [Member] | NCUC [Member]
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease), amount									(9.5)
Piedmont Natural Gas [Member] | NCUC IMR Petition filed May 2018 [Member] | NCUC [Member]
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease), amount									(5.7)
Storm Costs [Member] | Duke Energy Florida [Member] | Storm Restoration Cost Recovery [Member] | FPSC [Member]
Public Utilities, General Disclosures [Line Items]
Allowed storm allowance			$ 132						$ 132		$ 132
Subsequent Event [Member] | Piedmont Natural Gas [Member] | South Carolina Rate Stabilization Adjustment Filing [Member] | PSCSC [Member]
Public Utilities, General Disclosures [Line Items]
Approved return on equity percentage	10.20%

Regulatory Matters (Schedule of

Regulatory Matters (Schedule of Net Carrying Value Of Facilities and Megawatt Capacity) (Details) $ in Millions	9 Months Ended
	Sep. 30, 2018USD ($)MW	Dec. 31, 2017USD ($)
Public Utilities, General Disclosures [Line Items]
Public utilities, property, plant and equipment, net	$ 89,865	$ 86,391
Duke Energy Carolinas [Member]
Public Utilities, General Disclosures [Line Items]
Public utilities, property, plant and equipment, net	28,550	27,876
Progress Energy [Member]
Public Utilities, General Disclosures [Line Items]
Public utilities, property, plant and equipment, net	33,558	31,887
Duke Energy Florida [Member]
Public Utilities, General Disclosures [Line Items]
Public utilities, property, plant and equipment, net	13,561	12,783
Duke Energy Indiana [Member]
Public Utilities, General Disclosures [Line Items]
Public utilities, property, plant and equipment, net	$ 10,467	$ 10,286
Generation Facilities To Be Retired [Member]
Public Utilities, General Disclosures [Line Items]
Capacity (in MW) | MW	1,631
Public utilities, property, plant and equipment, net	$ 355
Allen Steam Station Units 1-3 [Member] | Generation Facilities To Be Retired [Member] | Duke Energy Carolinas [Member]
Public Utilities, General Disclosures [Line Items]
Capacity (in MW) | MW	585
Public utilities, property, plant and equipment, net	$ 132
Crystal River Units 1 and 2 [Member] | Generation Facilities To Be Retired [Member] | Progress Energy [Member]
Public Utilities, General Disclosures [Line Items]
Capacity (in MW) | MW	766
Public utilities, property, plant and equipment, net	$ 100
Crystal River Units 1 and 2 [Member] | Generation Facilities To Be Retired [Member] | Duke Energy Florida [Member]
Public Utilities, General Disclosures [Line Items]
Capacity (in MW) | MW	766
Public utilities, property, plant and equipment, net	$ 100
Gallagher Units 2 and 4 [Member] | Generation Facilities To Be Retired [Member] | Duke Energy Indiana [Member]
Public Utilities, General Disclosures [Line Items]
Capacity (in MW) | MW	280
Public utilities, property, plant and equipment, net	$ 123

Commitments and Contingencies_2

Commitments and Contingencies (Narrative) (Details)	1 Months Ended	9 Months Ended
	Jul. 31, 2018USD ($)	Sep. 30, 2018USD ($)plantclaimT	Dec. 31, 2017USD ($)
Valuation and Qualifying Accounts [Abstract]
Loss contingency accrual		$ 63,000,000	$ 88,000,000
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]
Number of plants with no disputed facts | plant		7
Number of NC plants with ash basins | plant		14
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]
Valuation and Qualifying Accounts [Abstract]
Loss contingency accrual		$ 11,000,000	30,000,000
Duke Energy Carolinas [Member] | Groundwater Contamination Claims [Member]
Valuation and Qualifying Accounts [Abstract]
Loss contingency accrual		4,000,000
Duke Energy Carolinas [Member] | Asbestos-related Injuries and Damages Claims [Member]
Valuation and Qualifying Accounts [Abstract]
Asbestos-related injuries and damages reserves		461,000,000	489,000,000
Reinsurance retention policy, excess retention, amount reinsured		764,000,000
Probable insurance recoveries		$ 553,000,000	585,000,000
Duke Energy Carolinas [Member] | Asbestos-related Injuries and Damages Claims [Member] | Non-Malignant Asbestos Claim [Member]
Valuation and Qualifying Accounts [Abstract]
Loss contingency, pending claims, number | claim		160
Asbestos-related injuries and damages reserves		$ 43,000,000
Duke Energy Carolinas [Member] | Asbestos-related Injuries and Damages Claims [Member] | Malignant Asbestos Claim [Member]
Valuation and Qualifying Accounts [Abstract]
Loss contingency, pending claims, number | claim		63
Asbestos-related injuries and damages reserves		$ 19,000,000
Progress Energy [Member]
Valuation and Qualifying Accounts [Abstract]
Loss contingency accrual		50,000,000	55,000,000
Duke Energy Progress [Member]
Valuation and Qualifying Accounts [Abstract]
Loss contingency accrual		11,000,000	13,000,000
Duke Energy Progress [Member] | Groundwater Contamination Claims [Member]
Valuation and Qualifying Accounts [Abstract]
Loss contingency accrual		2,000,000
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
Estimate of possible losses		$ 90,000,000
Duke Energy Florida [Member]
Valuation and Qualifying Accounts [Abstract]
Loss contingency accrual		23,000,000	24,000,000
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		510,000,000
Loss contingency, damages awarded, value		30,000,000
Gain contingency, dismissed amount		54,000,000
Loss contingency damages awarded and interest, value		34,000,000
Loss contingency, damages paid, value	$ 34,000,000
Duke Energy Florida [Member] | MGP Cost Recovery Action [Member]
Valuation and Qualifying Accounts [Abstract]
Gain contingency, unrecorded amount		$ 43,000,000

Commitments and Contingencies_3

Commitments and Contingencies (Schedule of Environmental Loss Contingencies) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of period	$ 81	$ 98
Provisions/adjustments	7	(1)
Cash reductions	(20)	(13)
Balance at end of period	68	84
Environmental exit costs, reasonably possible additional loss	57
Duke Energy Carolinas [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of period	10	10
Provisions/adjustments	3	2
Cash reductions	(2)	(2)
Balance at end of period	11	10
Environmental exit costs, reasonably possible additional loss	17
Progress Energy [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of period	15	18
Provisions/adjustments	2	1
Cash reductions	(5)	(3)
Balance at end of period	12	16
Duke Energy Progress [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of period	3	3
Provisions/adjustments	3
Cash reductions	(1)
Balance at end of period	5	3
Duke Energy Florida [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of period	12	14
Provisions/adjustments	(1)	1
Cash reductions	(4)	(3)
Balance at end of period	7	12
Duke Energy Ohio [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of period	47	59
Provisions/adjustments	3	(3)
Cash reductions	(12)	(7)
Balance at end of period	38	49
Environmental exit costs, reasonably possible additional loss	30
Duke Energy Indiana [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of period	5	10
Provisions/adjustments	1	(2)
Cash reductions	(1)	(1)
Balance at end of period	5	7
Piedmont Natural Gas [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of period	2	1
Provisions/adjustments		1
Cash reductions	0
Balance at end of period	2	$ 2
Environmental exit costs, reasonably possible additional loss	$ 2

Commitments and Contingencies_4

Commitments and Contingencies (Schedule of Legal Reserves) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Loss Contingencies [Line Items]
Reserves for legal matters	$ 63	$ 88
Duke Energy Carolinas [Member]
Loss Contingencies [Line Items]
Reserves for legal matters	11	30
Progress Energy [Member]
Loss Contingencies [Line Items]
Reserves for legal matters	50	55
Duke Energy Progress [Member]
Loss Contingencies [Line Items]
Reserves for legal matters	11	13
Duke Energy Florida [Member]
Loss Contingencies [Line Items]
Reserves for legal matters	23	24
Piedmont Natural Gas [Member]
Loss Contingencies [Line Items]
Reserves for legal matters	$ 1	$ 2

Debt and Credit Facilities (Nar

Debt and Credit Facilities (Narrative) (Details) - USD ($)	9 Months Ended
	Sep. 30, 2018	Aug. 31, 2018
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Facility size	$ 8,000,000,000
Line of credit facility, expiration date	Mar. 16, 2023
Three Year Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Facility size	$ 1,000,000,000
Outstanding balance	500,000,000
Duke Energy Carolinas [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Facility size	1,750,000,000
Duke Energy Carolinas [Member] | USDOJ [Member] | North Carolina Ash Basins [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Minimum master credit facility balance required	250,000,000
Duke Energy Progress [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Facility size	1,400,000,000
Piedmont Natural Gas [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Facility size	500,000,000
Debt Maturing September 2019, 2.848% Coupon [Member] | Piedmont Natural Gas [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Facility size	350,000,000	$ 250,000,000
Outstanding balance	$ 350,000,000

Debt and Credit Facilities (Sum

Debt and Credit Facilities (Summary of Debt Issuances) (Details) - USD ($)	1 Months Ended	9 Months Ended
	Apr. 30, 2018	Sep. 30, 2018	Sep. 30, 2017
Debt Instrument [Line Items]
Debt issuances		$ 4,050,000,000
Repayments of long-term debt		2,278,000,000	$ 2,035,000,000
Parent Company [Member]
Debt Instrument [Line Items]
Debt issuances		1,250,000,000
Duke Energy Carolinas [Member]
Debt Instrument [Line Items]
Debt issuances		1,000,000,000
Repayments of long-term debt		704,000,000	115,000,000
Duke Energy Carolinas [Member] | First Mortgage Bonds Maturing April 2018, 5.100% Coupon
Debt Instrument [Line Items]
Repayments of long-term debt	$ 300,000,000
Duke Energy Progress [Member]
Debt Instrument [Line Items]
Debt issuances		800,000,000
Repayments of long-term debt		2,000,000	270,000,000
Duke Energy Florida [Member]
Debt Instrument [Line Items]
Debt issuances		1,000,000,000
Repayments of long-term debt		717,000,000	$ 341,000,000
Unsecured Debt [Member] | March 2018 Debt Issuance 3.950% Coupon Due 2025 [Member]
Debt Instrument [Line Items]
Debt issuances		$ 250,000,000
Interest rate		3.95%
Unsecured Debt [Member] | May 2018 Debt Issuance 2.819% Coupon Due 2021 [Member] [Member]
Debt Instrument [Line Items]
Debt issuances		$ 500,000,000
Interest rate		2.819%
Unsecured Debt [Member] | September 2018 Debt Issuance 5.625% Coupon Due 2078 [Member]
Debt Instrument [Line Items]
Debt issuances		$ 500,000,000
Interest rate		5.625%
Unsecured Debt [Member] | Parent Company [Member] | March 2018 Debt Issuance 3.950% Coupon Due 2025 [Member]
Debt Instrument [Line Items]
Debt issuances		$ 250,000,000
Unsecured Debt [Member] | Parent Company [Member] | May 2018 Debt Issuance 2.819% Coupon Due 2021 [Member] [Member]
Debt Instrument [Line Items]
Debt issuances		500,000,000
Unsecured Debt [Member] | Parent Company [Member] | September 2018 Debt Issuance 5.625% Coupon Due 2078 [Member]
Debt Instrument [Line Items]
Debt issuances		500,000,000
First Mortgage [Member] | March 2018 Debt Issuance 3.050% Coupon Due 2023 [Member]
Debt Instrument [Line Items]
Debt issuances		$ 500,000,000
Interest rate		3.05%
First Mortgage [Member] | March 2018 Debt Issuance 3.950% Coupon Due 2048 [Member]
Debt Instrument [Line Items]
Debt issuances		$ 500,000,000
Interest rate		3.95%
First Mortgage [Member] | June 2018 Debt issuance 3.80% coupon Due 2028 [Member]
Debt Instrument [Line Items]
Debt issuances		$ 600,000,000
Interest rate		3.80%
First Mortgage [Member] | June 2018 Debt Issuance 4.20 Coupon Due 2048 [Member]
Debt Instrument [Line Items]
Debt issuances		$ 400,000,000
Interest rate		4.20%
First Mortgage [Member] | August 2018 Debt Issuance 3.375% Coupon Due 2023 [Member]
Debt Instrument [Line Items]
Debt issuances		$ 300,000,000
Interest rate		3.375%
First Mortgage [Member] | August 2018 Debt Issuance 3.700% Coupon Due 2028 [Member]
Debt Instrument [Line Items]
Debt issuances		$ 500,000,000
Interest rate		3.70%
First Mortgage [Member] | Duke Energy Carolinas [Member] | March 2018 Debt Issuance 3.050% Coupon Due 2023 [Member]
Debt Instrument [Line Items]
Debt issuances		$ 500,000,000
First Mortgage [Member] | Duke Energy Carolinas [Member] | March 2018 Debt Issuance 3.950% Coupon Due 2048 [Member]
Debt Instrument [Line Items]
Debt issuances		500,000,000
First Mortgage [Member] | Duke Energy Progress [Member] | August 2018 Debt Issuance 3.375% Coupon Due 2023 [Member]
Debt Instrument [Line Items]
Debt issuances		300,000,000
First Mortgage [Member] | Duke Energy Progress [Member] | August 2018 Debt Issuance 3.700% Coupon Due 2028 [Member]
Debt Instrument [Line Items]
Debt issuances		500,000,000
First Mortgage [Member] | Duke Energy Florida [Member] | June 2018 Debt issuance 3.80% coupon Due 2028 [Member]
Debt Instrument [Line Items]
Debt issuances		600,000,000
First Mortgage [Member] | Duke Energy Florida [Member] | June 2018 Debt Issuance 4.20 Coupon Due 2048 [Member]
Debt Instrument [Line Items]
Debt issuances		$ 400,000,000

Debt and Credit Facilities (S_2

Debt and Credit Facilities (Summary of Current Maturities of Long-term Debt) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Current maturities of long-term debt	$ 3,455	$ 3,244
Other debt obligations [Member]
Debt Instrument [Line Items]
Current maturities of long-term debt	$ 605
Parent Company [Member] | Unsecured Debt [Member] | Debt Maturing September 2019, 5.050% Coupon [Member]
Debt Instrument [Line Items]
Interest rate	5.05%
Current maturities of long-term debt	$ 500
Progress Energy [Member]
Debt Instrument [Line Items]
Current maturities of long-term debt	$ 1,322	771
Progress Energy [Member] | Unsecured Debt [Member] | Debt Maturing March 2019, 7.050% Coupon [Member]
Debt Instrument [Line Items]
Interest rate	7.05%
Current maturities of long-term debt	$ 450
Piedmont Natural Gas [Member]
Debt Instrument [Line Items]
Current maturities of long-term debt	$ 350	250
Piedmont Natural Gas [Member] | Unsecured Debt [Member] | Debt Maturing September 2019, 2.848% Coupon [Member]
Debt Instrument [Line Items]
Interest rate	2.848%
Current maturities of long-term debt	$ 350
Duke Energy Carolinas [Member]
Debt Instrument [Line Items]
Current maturities of long-term debt	$ 506	1,205
Duke Energy Carolinas [Member] | First Mortgage Bonds [Member] | Bonds Maturing November 2018, 7.000% Coupon [Member]
Debt Instrument [Line Items]
Interest rate	7.00%
Current maturities of long-term debt	$ 500
Duke Energy Progress [Member]
Debt Instrument [Line Items]
Current maturities of long-term debt	$ 603	3
Duke Energy Progress [Member] | First Mortgage Bonds [Member] | Bonds Maturing January 2019, 5.300% Coupon [Member]
Debt Instrument [Line Items]
Interest rate	5.30%
Current maturities of long-term debt	$ 600
Duke Energy Ohio [Member]
Debt Instrument [Line Items]
Current maturities of long-term debt	$ 452	$ 3
Duke Energy Ohio [Member] | First Mortgage Bonds [Member] | Bonds Maturing April 2019, 5.450% Coupon [Member] [Member]
Debt Instrument [Line Items]
Interest rate	5.45%
Current maturities of long-term debt	$ 450

Debt and Credit Facilities (Sch

Debt and Credit Facilities (Schedule of Line of Credit Facilities) (Details) - Revolving Credit Facility [Member]	Sep. 30, 2018USD ($)
Line of Credit Facility [Line Items]
Facility size	$ 8,000,000,000
Commercial paper	(2,519,000,000)
Outstanding letters of credit	(55,000,000)
Tax exempt bonds	(81,000,000)
Coal ash set-aside	(500,000,000)
Available capacity	4,845,000,000
Parent Company [Member]
Line of Credit Facility [Line Items]
Facility size	2,650,000,000
Commercial paper	(988,000,000)
Outstanding letters of credit	(47,000,000)
Available capacity	1,615,000,000
Duke Energy Carolinas [Member]
Line of Credit Facility [Line Items]
Facility size	1,750,000,000
Commercial paper	(872,000,000)
Outstanding letters of credit	(4,000,000)
Coal ash set-aside	(250,000,000)
Available capacity	624,000,000
Duke Energy Progress [Member]
Line of Credit Facility [Line Items]
Facility size	1,400,000,000
Commercial paper	(150,000,000)
Outstanding letters of credit	(2,000,000)
Coal ash set-aside	(250,000,000)
Available capacity	998,000,000
Duke Energy Florida [Member]
Line of Credit Facility [Line Items]
Facility size	650,000,000
Available capacity	650,000,000
Duke Energy Ohio [Member]
Line of Credit Facility [Line Items]
Facility size	450,000,000
Commercial paper	(216,000,000)
Available capacity	234,000,000
Duke Energy Indiana [Member]
Line of Credit Facility [Line Items]
Facility size	600,000,000
Commercial paper	(293,000,000)
Tax exempt bonds	(81,000,000)
Available capacity	226,000,000
Piedmont Natural Gas [Member]
Line of Credit Facility [Line Items]
Facility size	500,000,000
Outstanding letters of credit	(2,000,000)
Available capacity	498,000,000
Proceeds Loaned To Subsidiary Registrants [Member] | Parent Company [Member]
Line of Credit Facility [Line Items]
Commercial paper	$ (625,000,000)

Asset Retirement Obligations (A

Asset Retirement Obligations (ARO by Category) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Asset Retirement Obligations [Line Items]
Total ARO	$ 10,256	$ 10,175
Less: current portion	902	689
Total noncurrent ARO	9,354	9,486
Duke Energy Carolinas [Member]
Asset Retirement Obligations [Line Items]
Total ARO	3,712	3,610
Less: current portion	292	337
Total noncurrent ARO	3,420	3,273
Progress Energy [Member]
Asset Retirement Obligations [Line Items]
Total ARO	5,435	5,414
Less: current portion	475	295
Total noncurrent ARO	4,960	5,119
Duke Energy Progress [Member]
Asset Retirement Obligations [Line Items]
Total ARO	4,841	4,673
Less: current portion	470	295
Total noncurrent ARO	4,371	4,378
Duke Energy Florida [Member]
Asset Retirement Obligations [Line Items]
Total ARO	593	742
Less: current portion	4
Total noncurrent ARO	589	742
Duke Energy Ohio [Member]
Asset Retirement Obligations [Line Items]
Total ARO	98	84
Less: current portion	7	3
Total noncurrent ARO	91	81
Duke Energy Indiana [Member]
Asset Retirement Obligations [Line Items]
Total ARO	744	781
Less: current portion	128	54
Total noncurrent ARO	616	727
Piedmont Natural Gas [Member]
Asset Retirement Obligations [Line Items]
Total ARO	15	15
Total noncurrent ARO	15	$ 15
Decommissioning of Nuclear Power Facilities [Member]
Asset Retirement Obligations [Line Items]
Total ARO	5,367
Decommissioning of Nuclear Power Facilities [Member] | Duke Energy Carolinas [Member]
Asset Retirement Obligations [Line Items]
Total ARO	2,031
Decommissioning of Nuclear Power Facilities [Member] | Progress Energy [Member]
Asset Retirement Obligations [Line Items]
Total ARO	3,181
Decommissioning of Nuclear Power Facilities [Member] | Duke Energy Progress [Member]
Asset Retirement Obligations [Line Items]
Total ARO	2,650
Decommissioning of Nuclear Power Facilities [Member] | Duke Energy Florida [Member]
Asset Retirement Obligations [Line Items]
Total ARO	531
Closure of Ash Impoundments [Member]
Asset Retirement Obligations [Line Items]
Total ARO	4,575
Closure of Ash Impoundments [Member] | Duke Energy Carolinas [Member]
Asset Retirement Obligations [Line Items]
Total ARO	1,623
Closure of Ash Impoundments [Member] | Progress Energy [Member]
Asset Retirement Obligations [Line Items]
Total ARO	2,175
Closure of Ash Impoundments [Member] | Duke Energy Progress [Member]
Asset Retirement Obligations [Line Items]
Total ARO	2,154
Closure of Ash Impoundments [Member] | Duke Energy Florida [Member]
Asset Retirement Obligations [Line Items]
Total ARO	20
Closure of Ash Impoundments [Member] | Duke Energy Ohio [Member]
Asset Retirement Obligations [Line Items]
Total ARO	52
Closure of Ash Impoundments [Member] | Duke Energy Indiana [Member]
Asset Retirement Obligations [Line Items]
Total ARO	725
Other [Member]
Asset Retirement Obligations [Line Items]
Total ARO	314
Other [Member] | Duke Energy Carolinas [Member]
Asset Retirement Obligations [Line Items]
Total ARO	58
Other [Member] | Progress Energy [Member]
Asset Retirement Obligations [Line Items]
Total ARO	79
Other [Member] | Duke Energy Progress [Member]
Asset Retirement Obligations [Line Items]
Total ARO	37
Other [Member] | Duke Energy Florida [Member]
Asset Retirement Obligations [Line Items]
Total ARO	42
Other [Member] | Duke Energy Ohio [Member]
Asset Retirement Obligations [Line Items]
Total ARO	46
Other [Member] | Duke Energy Indiana [Member]
Asset Retirement Obligations [Line Items]
Total ARO	19
Other [Member] | Piedmont Natural Gas [Member]
Asset Retirement Obligations [Line Items]
Total ARO	$ 15

Asset Retirement Obligations _2

Asset Retirement Obligations (ARO Rollforward) (Details) $ in Millions	9 Months Ended
	Sep. 30, 2018USD ($)
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of period	$ 10,175
Accretion expense	319
Liabilities settled	(431)
Liabilities incurred in the current year	34
Revision in estimates of cash flows	159
Balance at end of period	10,256
Duke Energy Carolinas [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of period	3,610
Accretion expense	133
Liabilities settled	(198)
Liabilities incurred in the current year	8
Revision in estimates of cash flows	159
Balance at end of period	3,712
Progress Energy [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of period	5,414
Accretion expense	168
Liabilities settled	(186)
Revision in estimates of cash flows	39
Balance at end of period	5,435
Duke Energy Progress [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of period	4,673
Accretion expense	145
Liabilities settled	(155)
Revision in estimates of cash flows	178
Balance at end of period	4,841
Duke Energy Florida [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of period	742
Accretion expense	23
Liabilities settled	(31)
Revision in estimates of cash flows	(141)
Balance at end of period	593
Duke Energy Ohio [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of period	84
Accretion expense	3
Liabilities settled	(5)
Revision in estimates of cash flows	16
Balance at end of period	98
Duke Energy Indiana [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of period	781
Accretion expense	22
Liabilities settled	(42)
Liabilities incurred in the current year	25
Revision in estimates of cash flows	(42)
Balance at end of period	744
Piedmont Natural Gas [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of period	15
Balance at end of period	$ 15

Goodwill (Rollforward of Goodwi

Goodwill (Rollforward of Goodwill) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Goodwill [Line Items]
Goodwill balance	$ 19,425	$ 19,425
Accumulated impairment charges	(122)	(29)
Goodwill balance, adjusted for accumulated impairment charges	19,303	19,396
Electric Utilities and Infrastructure [Member]
Goodwill [Line Items]
Goodwill balance	17,379	17,379
Goodwill balance, adjusted for accumulated impairment charges	17,379	17,379
Gas Utilities and Infrastructure [Member]
Goodwill [Line Items]
Goodwill balance	1,924	1,924
Goodwill balance, adjusted for accumulated impairment charges	1,924	1,924
Commercial Renewables [Member]
Goodwill [Line Items]
Goodwill balance	122	122
Accumulated impairment charges	$ (122)	(29)
Goodwill balance, adjusted for accumulated impairment charges		$ 93

Goodwill (Narrative) (Details)

Goodwill (Narrative) (Details) - USD ($)	3 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Goodwill [Line Items]
Goodwill	$ 19,303,000,000	$ 19,396,000,000
Accumulated impairment charges	122,000,000	29,000,000
Electric Utilities and Infrastructure [Member]
Goodwill [Line Items]
Goodwill	17,379,000,000	17,379,000,000
Gas Utilities and Infrastructure [Member]
Goodwill [Line Items]
Goodwill	1,924,000,000	1,924,000,000
Commercial Renewables [Member]
Goodwill [Line Items]
Goodwill		93,000,000
Accumulated impairment charges	122,000,000	29,000,000
Goodwill impairment	93,000,000
Duke Energy Ohio [Member]
Goodwill [Line Items]
Goodwill	920,000,000	920,000,000
Accumulated impairment charges	216,000,000	216,000,000
Duke Energy Ohio [Member] | Electric Utilities and Infrastructure [Member]
Goodwill [Line Items]
Goodwill	596,000,000	596,000,000
Duke Energy Ohio [Member] | Gas Utilities and Infrastructure [Member]
Goodwill [Line Items]
Goodwill	324,000,000	324,000,000
Progress Energy [Member]
Goodwill [Line Items]
Goodwill	3,655,000,000	3,655,000,000
Accumulated impairment charges	0	0
Piedmont Natural Gas [Member]
Goodwill [Line Items]
Goodwill	49,000,000	49,000,000
Accumulated impairment charges	$ 0	$ 0

Related Party Transactions (Oth

Related Party Transactions (Other Revenue and Expense) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
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	$ 214	$ 206	$ 647	$ 645
Duke Energy Carolinas [Member] | Indemnification coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	6	5	17	17
Duke Energy Carolinas [Member] | JDA [Member] | Duke Energy Progress [Member]
Related Party Transaction [Line Items]
Related party transaction, other revenues from transactions with related party	13	9	66	42
Related party transaction, expenses from transactions with related party	61	39	134	91
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	3	3	11	5
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	216	207	613	555
Progress Energy [Member] | Indemnification coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	8	10	25	29
Progress Energy [Member] | JDA [Member] | Duke Energy Carolinas [Member]
Related Party Transaction [Line Items]
Related party transaction, other revenues from transactions with related party	61	39	134	91
Related party transaction, expenses from transactions with related party	13	9	66	42
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	20	19	58	57
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	138	112	382	321
Duke Energy Progress [Member] | Indemnification coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	3	4	9	11
Duke Energy Progress [Member] | JDA [Member] | Duke Energy Carolinas [Member]
Related Party Transaction [Line Items]
Related party transaction, other revenues from transactions with related party	61	39	134	91
Related party transaction, expenses from transactions with related party	13	9	66	42
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	20	19	58	57
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	78	95	231	234
Duke Energy Florida [Member] | Indemnification coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	5	6	16	18
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	85	90	264	275
Duke Energy Ohio [Member] | Indemnification coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	1	1	3	3
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	105	94	302	281
Duke Energy Indiana [Member] | Indemnification coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	2	2	6	6
Piedmont Natural Gas [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, other revenues from transactions with related party				62
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	39	11	115	25
Piedmont Natural Gas [Member] | Indemnification coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	1	1	2	$ 2
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	$ 23	$ 22	$ 69

Related Party Transactions (Equ

Related Party Transactions (Equity Method Investments) (Details) - Piedmont Natural Gas [Member] - Equity Method Investee [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	$ 6	$ 6	$ 18	$ 19
Cardinal Pipeline Company, LLC [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	2	2	5	6
Pine Needle LNG Company, LLC [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	2	2	6	6
Hardy Storage Company, LLC [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	$ 2	$ 2	$ 7	$ 7

Related Party Transactions (Nar

Related Party Transactions (Narrative) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Piedmont Natural Gas [Member] | Equity Method Investee [Member]
Related Party Transaction [Line Items]
Accounts payable, related parties	$ 2	$ 2

Related Party Transactions (Int

Related Party Transactions (Intercompany Income Taxes) (Details) - Affiliated Entity [Member] - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Duke Energy Carolinas [Member]
Related Party Transaction [Line Items]
Income taxes receivable	$ 32
Income tax payable		$ 44
Progress Energy [Member]
Related Party Transaction [Line Items]
Income taxes receivable	196	168
Duke Energy Progress [Member]
Related Party Transaction [Line Items]
Income taxes receivable	80
Income tax payable		21
Duke Energy Florida [Member]
Related Party Transaction [Line Items]
Income taxes receivable		44
Income tax payable	77
Duke Energy Ohio [Member]
Related Party Transaction [Line Items]
Income taxes receivable		22
Income tax payable	9
Duke Energy Indiana [Member]
Related Party Transaction [Line Items]
Income taxes receivable	22
Income tax payable		35
Piedmont Natural Gas [Member]
Related Party Transaction [Line Items]
Income taxes receivable	$ 11	$ 7

Derivatives and Hedging (Notion

Derivatives and Hedging (Notional Amounts of Derivative Instruments) (Details) Mcf in Millions, $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2018USD ($)GWhMcf	Dec. 31, 2017USD ($)GWhMcf
Commodity Contracts [Member] | Electricity [Member]
Derivative [Line Items]
Notional amount, energy measure (in gigawatt-hours) | GWh	170	34
Commodity Contracts [Member] | Natural Gas [Member]
Derivative [Line Items]
Notional amount, volume (in millions of decatherms) | Mcf	744	770
Interest Rate Contracts [Member]
Derivative [Line Items]
Notional amount	$ 1,538	$ 1,587
Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Notional amount	411	660
Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Notional amount	1,127	927
Variable Interest Entity, Primary Beneficiary [Member] | Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Notional amount	411	$ 660
Variable Interest Entity, Primary Beneficiary [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Notional amount	$ 200
Duke Energy Carolinas [Member] | Commodity Contracts [Member] | Natural Gas [Member]
Derivative [Line Items]
Notional amount, volume (in millions of decatherms) | Mcf	119	105
Duke Energy Carolinas [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Notional amount	$ 400	$ 400
Duke Energy Carolinas [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Notional amount	$ 400	$ 400
Progress Energy [Member] | Commodity Contracts [Member] | Natural Gas [Member]
Derivative [Line Items]
Notional amount, volume (in millions of decatherms) | Mcf	167	183
Progress Energy [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Notional amount	$ 500	$ 500
Progress Energy [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Notional amount	$ 500	$ 500
Duke Energy Progress [Member] | Commodity Contracts [Member] | Natural Gas [Member]
Derivative [Line Items]
Notional amount, volume (in millions of decatherms) | Mcf	158	133
Duke Energy Progress [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Notional amount	$ 250	$ 250
Duke Energy Progress [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [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	9	50
Duke Energy Florida [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Notional amount	$ 250	$ 250
Duke Energy Florida [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Notional amount	250	250
Duke Energy Ohio [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Notional amount	27	27
Duke Energy Ohio [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [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	170	34
Duke Energy Indiana [Member] | Commodity Contracts [Member] | Natural Gas [Member]
Derivative [Line Items]
Notional amount, volume (in millions of decatherms) | Mcf	1	2
Piedmont Natural Gas [Member] | Commodity Contracts [Member] | Natural Gas [Member]
Derivative [Line Items]
Notional amount, volume (in millions of decatherms) | Mcf	457	480

Derivatives and Hedging (Locati

Derivatives and Hedging (Location and Fair Value Amounts of Derivatives Reflected in the Condensed Consolidated Balance Sheets) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	$ 77	$ 51
Location and fair value amounts of derivatives (Liability)	225	230
Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	53	35
Noncurrent Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	24	16
Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	35	66
Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	190	164
Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	47	35
Location and fair value amounts of derivatives (Liability)	203	182
Interest Rate Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	30	16
Location and fair value amounts of derivatives (Liability)	22	48
Designated As Hedging Instrument [Member] | Interest Rate Contracts [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	6	1
Designated As Hedging Instrument [Member] | Interest Rate Contracts [Member] | Noncurrent Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	6	15
Designated As Hedging Instrument [Member] | Interest Rate Contracts [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	2	29
Designated As Hedging Instrument [Member] | Interest Rate Contracts [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)		6
Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	46	34
Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Noncurrent Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	1
Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	26	36
Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	177	146
Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1
Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member] | Noncurrent Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	17
Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	7	1
Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	13	12
Duke Energy Carolinas [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	7	2
Location and fair value amounts of derivatives (Liability)	28	35
Duke Energy Carolinas [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	7	2
Duke Energy Carolinas [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	14	31
Duke Energy Carolinas [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	14	4
Duke Energy Carolinas [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	2	2
Location and fair value amounts of derivatives (Liability)	28	10
Duke Energy Carolinas [Member] | Interest Rate Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	5
Location and fair value amounts of derivatives (Liability)		25
Duke Energy Carolinas [Member] | Designated As Hedging Instrument [Member] | Interest Rate Contracts [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	5
Duke Energy Carolinas [Member] | Designated As Hedging Instrument [Member] | Interest Rate Contracts [Member] | Current Liabilities, Other [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 Contracts [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	2	2
Duke Energy Carolinas [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	14	6
Duke Energy Carolinas [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	14	4
Progress Energy [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	3	3
Location and fair value amounts of derivatives (Liability)	37	36
Progress Energy [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	3	2
Progress Energy [Member] | Noncurrent Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)		1
Progress Energy [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	11	19
Progress Energy [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	26	17
Progress Energy [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	3	3
Location and fair value amounts of derivatives (Liability)	22	28
Progress Energy [Member] | Interest Rate Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	15	8
Progress Energy [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	3	2
Progress Energy [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Noncurrent Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)		1
Progress Energy [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	5	18
Progress Energy [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	17	10
Progress Energy [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	6	1
Progress Energy [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	9	7
Duke Energy Progress [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	2	2
Location and fair value amounts of derivatives (Liability)	24	18
Duke Energy Progress [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	2	1
Duke Energy Progress [Member] | Noncurrent Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)		1
Duke Energy Progress [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	8	8
Duke Energy Progress [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	16	10
Duke Energy Progress [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	2	2
Location and fair value amounts of derivatives (Liability)	13	12
Duke Energy Progress [Member] | Interest Rate Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	11	6
Duke Energy Progress [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	2	1
Duke Energy Progress [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Noncurrent Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	0	1
Duke Energy Progress [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	5	8
Duke Energy Progress [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	8	4
Duke Energy Progress [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	3
Duke Energy Progress [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	8	6
Duke Energy Florida [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	1
Location and fair value amounts of derivatives (Liability)	5	12
Duke Energy Florida [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	1
Duke Energy Florida [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	3	10
Duke Energy Florida [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	2	2
Duke Energy Florida [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	1
Location and fair value amounts of derivatives (Liability)		10
Duke Energy Florida [Member] | Interest Rate Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	5	2
Duke Energy Florida [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	1
Duke Energy Florida [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	0	10
Duke Energy Florida [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	3
Duke Energy Florida [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	2	2
Duke Energy Ohio [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	8	1
Location and fair value amounts of derivatives (Liability)	4	5
Duke Energy Ohio [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	8	1
Duke Energy Ohio [Member] | Current Liabilities, Other [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)	3	4
Duke Energy Ohio [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	8	1
Duke Energy Ohio [Member] | Interest Rate Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	4	5
Duke Energy Ohio [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	8	1
Duke Energy Ohio [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member] | Current Liabilities, Other [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 Contracts [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	3	4
Duke Energy Indiana [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	29	27
Duke Energy Indiana [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	29	27
Duke Energy Indiana [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	29	27
Duke Energy Indiana [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	29	27
Piedmont Natural Gas [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	4	2
Location and fair value amounts of derivatives (Liability)	153	142
Piedmont Natural Gas [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	4	2
Piedmont Natural Gas [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	7	11
Piedmont Natural Gas [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	146	131
Piedmont Natural Gas [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	4	2
Location and fair value amounts of derivatives (Liability)	153	142
Piedmont Natural Gas [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	4	2
Piedmont Natural Gas [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	7	11
Piedmont Natural Gas [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	$ 146	$ 131

Derivatives and Hedging (Schedu

Derivatives and Hedging (Schedule of Offsetting Assets) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	$ 77	$ 51
Net amounts recognized on the Condensed Consolidated Balance Sheet	77	51
Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	53	35
Gross amounts offset	(4)
Net amounts recognized on the Condensed Consolidated Balance Sheet	49	35
Noncurrent Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	24	16
Gross amounts offset	(1)
Net amounts recognized on the Condensed Consolidated Balance Sheet	23	16
Duke Energy Carolinas [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	7	2
Net amounts recognized on the Condensed Consolidated Balance Sheet	7	2
Duke Energy Carolinas [Member] | Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	7	2
Gross amounts offset	(2)
Net amounts recognized on the Condensed Consolidated Balance Sheet	5	2
Progress Energy [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	3	3
Net amounts recognized on the Condensed Consolidated Balance Sheet	3	3
Progress Energy [Member] | Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	3	2
Gross amounts offset	(2)
Net amounts recognized on the Condensed Consolidated Balance Sheet	1	2
Progress Energy [Member] | Noncurrent Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized		1
Net amounts recognized on the Condensed Consolidated Balance Sheet		1
Duke Energy Progress [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	2	2
Net amounts recognized on the Condensed Consolidated Balance Sheet	2	2
Duke Energy Progress [Member] | Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	2	1
Gross amounts offset	(2)
Net amounts recognized on the Condensed Consolidated Balance Sheet		1
Duke Energy Progress [Member] | Noncurrent Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized		1
Net amounts recognized on the Condensed Consolidated Balance Sheet		1
Duke Energy Florida [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	1	1
Net amounts recognized on the Condensed Consolidated Balance Sheet	1	1
Duke Energy Florida [Member] | Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	1	1
Net amounts recognized on the Condensed Consolidated Balance Sheet	1	1
Duke Energy Ohio [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	8	1
Net amounts recognized on the Condensed Consolidated Balance Sheet	8	1
Duke Energy Ohio [Member] | Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	8	1
Net amounts recognized on the Condensed Consolidated Balance Sheet	8	1
Duke Energy Indiana [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	29	27
Net amounts recognized on the Condensed Consolidated Balance Sheet	29	27
Duke Energy Indiana [Member] | Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	29	27
Net amounts recognized on the Condensed Consolidated Balance Sheet	29	27
Piedmont Natural Gas [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	4	2
Net amounts recognized on the Condensed Consolidated Balance Sheet	4	2
Piedmont Natural Gas [Member] | Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	4	2
Net amounts recognized on the Condensed Consolidated Balance Sheet	$ 4	$ 2

Derivatives and Hedging (Sche_2

Derivatives and Hedging (Schedule of Offsetting Liabilities) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	$ 225	$ 230
Net amounts recognized on the Condensed Consolidated Balance Sheet	225	230
Other Current Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	35	66
Gross amounts offset	(4)	(3)
Net amounts recognized on the Condensed Consolidated Balance Sheet	31	63
Other Noncurrent Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	190	164
Gross amounts offset	(1)	(1)
Net amounts recognized on the Condensed Consolidated Balance Sheet	189	163
Duke Energy Carolinas [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	28	35
Net amounts recognized on the Condensed Consolidated Balance Sheet	28	35
Duke Energy Carolinas [Member] | Other Current Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	14	31
Gross amounts offset	(2)	(2)
Net amounts recognized on the Condensed Consolidated Balance Sheet	12	29
Duke Energy Carolinas [Member] | Other Noncurrent Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	14	4
Net amounts recognized on the Condensed Consolidated Balance Sheet	14	4
Progress Energy [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	37	36
Net amounts recognized on the Condensed Consolidated Balance Sheet	37	36
Progress Energy [Member] | Other Current Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	11	19
Gross amounts offset	(2)	(2)
Net amounts recognized on the Condensed Consolidated Balance Sheet	9	17
Progress Energy [Member] | Other Noncurrent Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	26	17
Gross amounts offset	(1)	(1)
Net amounts recognized on the Condensed Consolidated Balance Sheet	25	16
Duke Energy Progress [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	24	18
Net amounts recognized on the Condensed Consolidated Balance Sheet	24	18
Duke Energy Progress [Member] | Other Current Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	8	8
Gross amounts offset	(2)	(2)
Net amounts recognized on the Condensed Consolidated Balance Sheet	6	6
Duke Energy Progress [Member] | Other Noncurrent Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	16	10
Gross amounts offset	(1)	(1)
Net amounts recognized on the Condensed Consolidated Balance Sheet	15	9
Duke Energy Florida [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	5	12
Net amounts recognized on the Condensed Consolidated Balance Sheet	5	12
Duke Energy Florida [Member] | Other Current Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	3	10
Net amounts recognized on the Condensed Consolidated Balance Sheet	3	10
Duke Energy Florida [Member] | Other Noncurrent Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	2	2
Net amounts recognized on the Condensed Consolidated Balance Sheet	2	2
Duke Energy Ohio [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	4	5
Net amounts recognized on the Condensed Consolidated Balance Sheet	4	5
Duke Energy Ohio [Member] | Other Current Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	1	1
Net amounts recognized on the Condensed Consolidated Balance Sheet	1	1
Duke Energy Ohio [Member] | Other Noncurrent Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	3	4
Net amounts recognized on the Condensed Consolidated Balance Sheet	3	4
Piedmont Natural Gas [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	153	142
Net amounts recognized on the Condensed Consolidated Balance Sheet	153	142
Piedmont Natural Gas [Member] | Other Current Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	7	11
Net amounts recognized on the Condensed Consolidated Balance Sheet	7	11
Piedmont Natural Gas [Member] | Other Noncurrent Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	146	131
Net amounts recognized on the Condensed Consolidated Balance Sheet	$ 146	$ 131

Derivatives and Hedging (Deriva

Derivatives and Hedging (Derivative Instruments with Credit-Risk Related Contingent Features and Cash Collateral) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Schedule of Information Regarding Derivative Instruments That Contain Credit-Risk Related Contingent Features
Aggregate fair value amounts of derivative instruments in a net liability position	$ 48	$ 59
Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered	48	59
Duke Energy Carolinas [Member]
Schedule of Information Regarding Derivative Instruments That Contain Credit-Risk Related Contingent Features
Aggregate fair value amounts of derivative instruments in a net liability position	26	35
Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered	26	35
Progress Energy [Member]
Schedule of Information Regarding Derivative Instruments That Contain Credit-Risk Related Contingent Features
Aggregate fair value amounts of derivative instruments in a net liability position	23	25
Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered	23	25
Duke Energy Progress [Member]
Schedule of Information Regarding Derivative Instruments That Contain Credit-Risk Related Contingent Features
Aggregate fair value amounts of derivative instruments in a net liability position	22	15
Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered	$ 22	15
Duke Energy Florida [Member]
Schedule of Information Regarding Derivative Instruments That Contain Credit-Risk Related Contingent Features
Aggregate fair value amounts of derivative instruments in a net liability position		10
Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered		$ 10

Investments in Debt and Equit_3

Investments in Debt and Equity Securities (All Debt and Equity Securities Through OCI and FV-NI - ASU 2016-01) (Details) $ in Millions	Sep. 30, 2018USD ($)
Schedule Of Available For Sale Securities And Other Trading Assets [Line Items]
Debt securities, available-for-sale, and equity securities, FV-NI, unrealized gain	$ 3,179
Debt securities, available-for-sale, and equity securities, FV-NI, unrealized loss	97
Debt securities, available-for-sale, and equity securities, FV-NI	7,790
Ndtf [Member]
Schedule Of Available For Sale Securities And Other Trading Assets [Line Items]
Debt securities, available-for-sale, and equity securities, FV-NI, unrealized gain	3,127
Debt securities, available-for-sale, and equity securities, FV-NI, unrealized loss	93
Cash and cash equivalents	75
Debt securities, available-for-sale, and equity securities, FV-NI	7,403
Other Classification [Member]
Schedule Of Available For Sale Securities And Other Trading Assets [Line Items]
Debt securities, available-for-sale, and equity securities, FV-NI, unrealized gain	52
Debt securities, available-for-sale, and equity securities, FV-NI, unrealized loss	4
Cash and cash equivalents	21
Debt securities, available-for-sale, and equity securities, FV-NI	387
Duke Energy Carolinas [Member] | Ndtf [Member]
Schedule Of Available For Sale Securities And Other Trading Assets [Line Items]
Debt securities, available-for-sale, and equity securities, FV-NI, unrealized gain	1,695
Debt securities, available-for-sale, and equity securities, FV-NI, unrealized loss	55
Cash and cash equivalents	18
Debt securities, available-for-sale, and equity securities, FV-NI	3,936
Progress Energy [Member]
Schedule Of Available For Sale Securities And Other Trading Assets [Line Items]
Debt securities, available-for-sale, and equity securities, FV-NI, unrealized gain	1,433
Debt securities, available-for-sale, and equity securities, FV-NI, unrealized loss	38
Debt securities, available-for-sale, and equity securities, FV-NI	3,533
Progress Energy [Member] | Ndtf [Member]
Schedule Of Available For Sale Securities And Other Trading Assets [Line Items]
Debt securities, available-for-sale, and equity securities, FV-NI, unrealized gain	1,432
Debt securities, available-for-sale, and equity securities, FV-NI, unrealized loss	38
Cash and cash equivalents	57
Debt securities, available-for-sale, and equity securities, FV-NI	3,467
Progress Energy [Member] | Other Classification [Member]
Schedule Of Available For Sale Securities And Other Trading Assets [Line Items]
Debt securities, available-for-sale, and equity securities, FV-NI, unrealized gain	1
Cash and cash equivalents	18
Debt securities, available-for-sale, and equity securities, FV-NI	66
Duke Energy Progress [Member]
Schedule Of Available For Sale Securities And Other Trading Assets [Line Items]
Debt securities, available-for-sale, and equity securities, FV-NI, unrealized gain	1,106
Debt securities, available-for-sale, and equity securities, FV-NI, unrealized loss	29
Debt securities, available-for-sale, and equity securities, FV-NI	2,744
Duke Energy Progress [Member] | Ndtf [Member]
Schedule Of Available For Sale Securities And Other Trading Assets [Line Items]
Debt securities, available-for-sale, and equity securities, FV-NI, unrealized gain	1,106
Debt securities, available-for-sale, and equity securities, FV-NI, unrealized loss	29
Cash and cash equivalents	42
Debt securities, available-for-sale, and equity securities, FV-NI	2,736
Duke Energy Progress [Member] | Other Classification [Member]
Schedule Of Available For Sale Securities And Other Trading Assets [Line Items]
Cash and cash equivalents	8
Debt securities, available-for-sale, and equity securities, FV-NI	8
Duke Energy Florida [Member]
Schedule Of Available For Sale Securities And Other Trading Assets [Line Items]
Debt securities, available-for-sale, and equity securities, FV-NI, unrealized gain	327
Debt securities, available-for-sale, and equity securities, FV-NI, unrealized loss	9
Debt securities, available-for-sale, and equity securities, FV-NI	779
Duke Energy Florida [Member] | Ndtf [Member]
Schedule Of Available For Sale Securities And Other Trading Assets [Line Items]
Debt securities, available-for-sale, and equity securities, FV-NI, unrealized gain	326
Debt securities, available-for-sale, and equity securities, FV-NI, unrealized loss	9
Cash and cash equivalents	15
Debt securities, available-for-sale, and equity securities, FV-NI	731
Duke Energy Florida [Member] | Other Classification [Member]
Schedule Of Available For Sale Securities And Other Trading Assets [Line Items]
Debt securities, available-for-sale, and equity securities, FV-NI, unrealized gain	1
Debt securities, available-for-sale, and equity securities, FV-NI	48
Duke Energy Indiana [Member]
Schedule Of Available For Sale Securities And Other Trading Assets [Line Items]
Debt securities, available-for-sale, and equity securities, FV-NI, unrealized gain	40
Debt securities, available-for-sale, and equity securities, FV-NI, unrealized loss	1
Debt securities, available-for-sale, and equity securities, FV-NI	$ 118

Investments in Debt and Equit_4

Investments in Debt and Equity Securities (Equity Securities, FV-NI - ASU 2016-01) (Details) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2018USD ($)	Sep. 30, 2018USD ($)
Equity Securities, FV-NI, Realized Gain (Loss) [Abstract]
Equity securities, FV-NI, realized gain	$ 19	$ 85
Equity securities, FV-NI, realized loss	16	60
Ndtf [Member]
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract]
Equity securities, FV-NI, unrealized gain	3,117	3,117
Equity securities, FV-NI, unrealized loss	48	48
Equity securities, FV-NI	5,272	5,272
Other Classification [Member]
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract]
Equity securities, FV-NI, unrealized gain	51	51
Equity securities, FV-NI	115	115
Duke Energy Carolinas [Member]
Equity Securities, FV-NI, Realized Gain (Loss) [Abstract]
Equity securities, FV-NI, realized gain	11	47
Equity securities, FV-NI, realized loss	8	30
Duke Energy Carolinas [Member] | Ndtf [Member]
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract]
Equity securities, FV-NI, unrealized gain	1,692	1,692
Equity securities, FV-NI, unrealized loss	29	29
Equity securities, FV-NI	2,890	2,890
Progress Energy [Member]
Equity Securities, FV-NI, Realized Gain (Loss) [Abstract]
Equity securities, FV-NI, realized gain	8	38
Equity securities, FV-NI, realized loss	8	30
Progress Energy [Member] | Ndtf [Member]
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract]
Equity securities, FV-NI, unrealized gain	1,425	1,425
Equity securities, FV-NI, unrealized loss	19	19
Equity securities, FV-NI	2,382	2,382
Duke Energy Progress [Member]
Equity Securities, FV-NI, Realized Gain (Loss) [Abstract]
Equity securities, FV-NI, realized gain	7	32
Equity securities, FV-NI, realized loss	7	27
Duke Energy Progress [Member] | Ndtf [Member]
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract]
Equity securities, FV-NI, unrealized gain	1,101	1,101
Equity securities, FV-NI, unrealized loss	14	14
Equity securities, FV-NI	1,913	1,913
Duke Energy Florida [Member]
Equity Securities, FV-NI, Realized Gain (Loss) [Abstract]
Equity securities, FV-NI, realized gain	1	6
Equity securities, FV-NI, realized loss	1	3
Duke Energy Florida [Member] | Ndtf [Member]
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract]
Equity securities, FV-NI, unrealized gain	324	324
Equity securities, FV-NI, unrealized loss	5	5
Equity securities, FV-NI	469	469
Duke Energy Indiana [Member]
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract]
Equity securities, FV-NI, unrealized gain	40	40
Equity securities, FV-NI	78	78
Duke Energy Indiana [Member] | Other Classification [Member]
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract]
Equity securities, FV-NI	$ 78	$ 78

Investments in Debt Securities

Investments in Debt Securities and Equity Securities (Available-for-sale, OCI - ASU 2016-01) (Details) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2018USD ($)	Sep. 30, 2018USD ($)
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale	$ 2,307	$ 2,307
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract]
Debt securities, available-for-sale, realized gain	4	14
Debt securities, available-for-sale, realized loss	7	32
Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale	2,131	2,131
Other Classification [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale	272	272
Corporate debt securities [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	5	5
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	10	10
Debt securities, available-for-sale	595	595
Corporate debt securities [Member] | Other Classification [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	1	1
Debt securities, available-for-sale	64	64
Municipal bonds [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	0	0
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	7	7
Debt securities, available-for-sale	346	346
Municipal bonds [Member] | Other Classification [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	1	1
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	1	1
Debt securities, available-for-sale	85	85
US treasury and government [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	5	5
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	25	25
Debt securities, available-for-sale	974	974
US treasury and government [Member] | Other Classification [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	1	1
Debt securities, available-for-sale	59	59
Other debt obligations [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	3	3
Debt securities, available-for-sale	141	141
Other debt obligations [Member] | Other Classification [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	1	1
Debt securities, available-for-sale	43	43
Duke Energy Carolinas [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale	1,028	1,028
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract]
Debt securities, available-for-sale, realized gain	4	13
Debt securities, available-for-sale, realized loss	6	24
Duke Energy Carolinas [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale	1,046	1,046
Duke Energy Carolinas [Member] | Corporate debt securities [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	2	2
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	7	7
Debt securities, available-for-sale	372	372
Duke Energy Carolinas [Member] | Municipal bonds [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	0	0
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	2	2
Debt securities, available-for-sale	80	80
Duke Energy Carolinas [Member] | US treasury and government [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	1	1
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	14	14
Debt securities, available-for-sale	439	439
Duke Energy Carolinas [Member] | Other debt obligations [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	0	0
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	3	3
Debt securities, available-for-sale	137	137
Progress Energy [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale	1,076	1,076
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract]
Debt securities, available-for-sale, realized gain	0	1
Debt securities, available-for-sale, realized loss	1	8
Progress Energy [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale	1,085	1,085
Progress Energy [Member] | Other Classification [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale	66	66
Progress Energy [Member] | Corporate debt securities [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	3	3
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	3	3
Debt securities, available-for-sale	223	223
Progress Energy [Member] | Municipal bonds [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	0	0
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	5	5
Debt securities, available-for-sale	266	266
Progress Energy [Member] | Municipal bonds [Member] | Other Classification [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	1	1
Debt securities, available-for-sale	48	48
Progress Energy [Member] | US treasury and government [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	4	4
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	11	11
Debt securities, available-for-sale	535	535
Progress Energy [Member] | Other debt obligations [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale	4	4
Duke Energy Progress [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale	781	781
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract]
Debt securities, available-for-sale, realized gain	0	1
Debt securities, available-for-sale, realized loss	1	6
Duke Energy Progress [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale	823	823
Duke Energy Progress [Member] | Other Classification [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale	8	8
Duke Energy Progress [Member] | Corporate debt securities [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	2	2
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	2	2
Debt securities, available-for-sale	162	162
Duke Energy Progress [Member] | Municipal bonds [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	0	0
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	5	5
Debt securities, available-for-sale	265	265
Duke Energy Progress [Member] | US treasury and government [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	3	3
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	8	8
Debt securities, available-for-sale	352	352
Duke Energy Progress [Member] | Other debt obligations [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	0	0
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	0	0
Debt securities, available-for-sale	2	2
Duke Energy Florida [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale	295	295
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract]
Debt securities, available-for-sale, realized loss	0	2
Duke Energy Florida [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale	262	262
Duke Energy Florida [Member] | Other Classification [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale	48	48
Duke Energy Florida [Member] | Corporate debt securities [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	1	1
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	1	1
Debt securities, available-for-sale	61	61
Duke Energy Florida [Member] | Municipal bonds [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	0	0
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	0	0
Debt securities, available-for-sale	1	1
Duke Energy Florida [Member] | Municipal bonds [Member] | Other Classification [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	1	1
Debt securities, available-for-sale	48	48
Duke Energy Florida [Member] | US treasury and government [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	1	1
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	3	3
Debt securities, available-for-sale	183	183
Duke Energy Florida [Member] | Other debt obligations [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	0	0
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	0	0
Debt securities, available-for-sale	2	2
Duke Energy Indiana [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale	40	40
Duke Energy Indiana [Member] | Other Classification [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale	40	40
Duke Energy Indiana [Member] | Corporate debt securities [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale	8	8
Duke Energy Indiana [Member] | Municipal bonds [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	1	1
Debt securities, available-for-sale	$ 32	$ 32

Investments in Debt and Equit_5

Investments in Debt and Equity Securities (Available-For-Sale Investments) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			$ 2,899
Gross Unrealized Holding Losses			42
Estimated Fair Value			7,451
Realized Gains	$ 37	$ 170
Realized Losses	25	124
Ndtf [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			2,837
Gross Unrealized Holding Losses			40
Estimated Fair Value			7,088
Ndtf [Member] | Cash and Cash Equivalents [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value			115
Ndtf [Member] | Equity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			2,805
Gross Unrealized Holding Losses			27
Estimated Fair Value			4,914
Ndtf [Member] | Corporate debt securities [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			17
Gross Unrealized Holding Losses			2
Estimated Fair Value			570
Ndtf [Member] | Municipal bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			4
Gross Unrealized Holding Losses			3
Estimated Fair Value			344
Ndtf [Member] | US treasury and government [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			11
Gross Unrealized Holding Losses			7
Estimated Fair Value			1,027
Ndtf [Member] | Other debt obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Losses			1
Estimated Fair Value			118
Other Classification [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			62
Gross Unrealized Holding Losses			2
Estimated Fair Value			363
Other Classification [Member] | Cash and Cash Equivalents [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value			15
Other Classification [Member] | Equity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			59
Estimated Fair Value			123
Other Classification [Member] | Corporate debt securities [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			1
Estimated Fair Value			57
Other Classification [Member] | Municipal bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			2
Gross Unrealized Holding Losses			1
Estimated Fair Value			83
Other Classification [Member] | US treasury and government [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value			41
Other Classification [Member] | Other debt obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Losses			1
Estimated Fair Value			44
Duke Energy Carolinas [Member]
Debt Securities, Available-for-sale [Line Items]
Realized Gains	20	110
Realized Losses	13	76
Duke Energy Carolinas [Member] | Ndtf [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			1,543
Gross Unrealized Holding Losses			20
Estimated Fair Value			3,758
Duke Energy Carolinas [Member] | Ndtf [Member] | Cash and Cash Equivalents [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value			32
Duke Energy Carolinas [Member] | Ndtf [Member] | Equity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			1,531
Gross Unrealized Holding Losses			12
Estimated Fair Value			2,692
Duke Energy Carolinas [Member] | Ndtf [Member] | Corporate debt securities [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			9
Gross Unrealized Holding Losses			2
Estimated Fair Value			359
Duke Energy Carolinas [Member] | Ndtf [Member] | Municipal bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Losses			1
Estimated Fair Value			60
Duke Energy Carolinas [Member] | Ndtf [Member] | US treasury and government [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			3
Gross Unrealized Holding Losses			4
Estimated Fair Value			503
Duke Energy Carolinas [Member] | Ndtf [Member] | Other debt obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Losses			1
Estimated Fair Value			112
Progress Energy [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			1,296
Gross Unrealized Holding Losses			20
Estimated Fair Value			3,389
Realized Gains	16	58
Realized Losses	12	47
Progress Energy [Member] | Ndtf [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			1,294
Gross Unrealized Holding Losses			20
Estimated Fair Value			3,330
Progress Energy [Member] | Ndtf [Member] | Cash and Cash Equivalents [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value			83
Progress Energy [Member] | Ndtf [Member] | Equity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			1,274
Gross Unrealized Holding Losses			15
Estimated Fair Value			2,222
Progress Energy [Member] | Ndtf [Member] | Corporate debt securities [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			8
Estimated Fair Value			211
Progress Energy [Member] | Ndtf [Member] | Municipal bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			4
Gross Unrealized Holding Losses			2
Estimated Fair Value			284
Progress Energy [Member] | Ndtf [Member] | US treasury and government [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			8
Gross Unrealized Holding Losses			3
Estimated Fair Value			524
Progress Energy [Member] | Ndtf [Member] | Other debt obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value			6
Progress Energy [Member] | Other Classification [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			2
Estimated Fair Value			59
Progress Energy [Member] | Other Classification [Member] | Cash and Cash Equivalents [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value			12
Progress Energy [Member] | Other Classification [Member] | Municipal bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			2
Estimated Fair Value			47
Duke Energy Progress [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			995
Gross Unrealized Holding Losses			16
Estimated Fair Value			2,592
Realized Gains	14	49
Realized Losses	11	41
Duke Energy Progress [Member] | Ndtf [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			995
Gross Unrealized Holding Losses			16
Estimated Fair Value			2,591
Duke Energy Progress [Member] | Ndtf [Member] | Cash and Cash Equivalents [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value			50
Duke Energy Progress [Member] | Ndtf [Member] | Equity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			980
Gross Unrealized Holding Losses			12
Estimated Fair Value			1,795
Duke Energy Progress [Member] | Ndtf [Member] | Corporate debt securities [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			6
Estimated Fair Value			149
Duke Energy Progress [Member] | Ndtf [Member] | Municipal bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			4
Gross Unrealized Holding Losses			2
Estimated Fair Value			283
Duke Energy Progress [Member] | Ndtf [Member] | US treasury and government [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			5
Gross Unrealized Holding Losses			2
Estimated Fair Value			310
Duke Energy Progress [Member] | Ndtf [Member] | Other debt obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value			4
Duke Energy Progress [Member] | Other Classification [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value			1
Duke Energy Progress [Member] | Other Classification [Member] | Cash and Cash Equivalents [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value			1
Duke Energy Florida [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			301
Gross Unrealized Holding Losses			4
Estimated Fair Value			787
Realized Gains	2	9
Realized Losses	$ 1	$ 6
Duke Energy Florida [Member] | Ndtf [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			299
Gross Unrealized Holding Losses			4
Estimated Fair Value			739
Duke Energy Florida [Member] | Ndtf [Member] | Cash and Cash Equivalents [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value			33
Duke Energy Florida [Member] | Ndtf [Member] | Equity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			294
Gross Unrealized Holding Losses			3
Estimated Fair Value			427
Duke Energy Florida [Member] | Ndtf [Member] | Corporate debt securities [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			2
Estimated Fair Value			62
Duke Energy Florida [Member] | Ndtf [Member] | Municipal bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value			1
Duke Energy Florida [Member] | Ndtf [Member] | US treasury and government [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			3
Gross Unrealized Holding Losses			1
Estimated Fair Value			214
Duke Energy Florida [Member] | Ndtf [Member] | Other debt obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value			2
Duke Energy Florida [Member] | Other Classification [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			2
Estimated Fair Value			48
Duke Energy Florida [Member] | Other Classification [Member] | Cash and Cash Equivalents [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value			1
Duke Energy Florida [Member] | Other Classification [Member] | Municipal bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			2
Estimated Fair Value			47
Duke Energy Indiana [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			49
Gross Unrealized Holding Losses			1
Estimated Fair Value			128
Duke Energy Indiana [Member] | Equity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Gains			49
Estimated Fair Value			97
Duke Energy Indiana [Member] | Corporate debt securities [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value			3
Duke Energy Indiana [Member] | Municipal bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Holding Losses			1
Estimated Fair Value			$ 28

Investments in Debt and Equit_6

Investments in Debt and Equity Securities (Maturities) (Details) $ in Millions	Sep. 30, 2018USD ($)
Debt Instrument [Line Items]
Due in one year or less	$ 100
Due after one through five years	492
Due after five through 10 years	561
Due after 10 years	1,154
Total	2,307
Duke Energy Carolinas [Member]
Debt Instrument [Line Items]
Due in one year or less	12
Due after one through five years	161
Due after five through 10 years	289
Due after 10 years	566
Total	1,028
Progress Energy [Member]
Debt Instrument [Line Items]
Due in one year or less	83
Due after one through five years	268
Due after five through 10 years	217
Due after 10 years	508
Total	1,076
Duke Energy Progress [Member]
Debt Instrument [Line Items]
Due in one year or less	40
Due after one through five years	200
Due after five through 10 years	156
Due after 10 years	385
Total	781
Duke Energy Florida [Member]
Debt Instrument [Line Items]
Due in one year or less	43
Due after one through five years	68
Due after five through 10 years	61
Due after 10 years	123
Total	295
Duke Energy Indiana [Member]
Debt Instrument [Line Items]
Due in one year or less	2
Due after one through five years	20
Due after five through 10 years	5
Due after 10 years	13
Total	$ 40

Fair Value Measurements (Fair V

Fair Value Measurements (Fair Value Measurement Amounts for Assets and Liabilities) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	$ 2,307
Derivative assets	77	$ 51
Total assets	7,867	7,503
Derivative liabilities	(225)	(230)
Net assets (liabilities)	7,642	7,273
Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	4	3
Total assets	5,910	5,658
Derivative liabilities	0	(2)
Net assets (liabilities)	5,910	5,656
Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	36	20
Total assets	1,851	1,743
Derivative liabilities	(72)	(86)
Net assets (liabilities)	1,779	1,657
Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	37	28
Total assets	37	28
Derivative liabilities	(153)	(142)
Net assets (liabilities)	(116)	(114)
Fair Value Measured at Net Asset Value Per Share [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	69	74
Net assets (liabilities)	69	74
Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	5,272
Debt securities, available-for-sale	2,131
Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	5,203
Debt securities, available-for-sale	510
Ndtf [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	1,621
Ndtf [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	69
Investments, fair value disclosures		74
Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	115
Debt securities, available-for-sale	272
Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	115
Debt securities, available-for-sale	78
Other Classification [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	194
Equity Securities [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		4,914
Equity Securities [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		4,840
Equity Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		123
Equity Securities [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		123
Debt Securities [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		2,174
Debt Securities [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		635
Debt Securities [Member] | Ndtf [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		1,539
Debt Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		241
Debt Securities [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		57
Debt Securities [Member] | Other Classification [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		184
Duke Energy Carolinas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	1,028
Derivative assets	7	2
Total assets	3,943	3,760
Derivative liabilities	(28)	(35)
Net assets (liabilities)	3,915	3,725
Duke Energy Carolinas [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0
Total assets	2,943	2,822
Derivative liabilities	0	(1)
Net assets (liabilities)	2,943	2,821
Duke Energy Carolinas [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	7	2
Total assets	931	864
Derivative liabilities	(28)	(34)
Net assets (liabilities)	903	830
Duke Energy Carolinas [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	69	74
Net assets (liabilities)	69	74
Duke Energy Carolinas [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	2,890
Debt securities, available-for-sale	1,046
Duke Energy Carolinas [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	2,821
Debt securities, available-for-sale	122
Duke Energy Carolinas [Member] | Ndtf [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	924
Duke Energy Carolinas [Member] | Ndtf [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	69
Investments, fair value disclosures		74
Duke Energy Carolinas [Member] | Equity Securities [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		2,692
Duke Energy Carolinas [Member] | Equity Securities [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		2,618
Duke Energy Carolinas [Member] | Debt Securities [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		1,066
Duke Energy Carolinas [Member] | Debt Securities [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		204
Duke Energy Carolinas [Member] | Debt Securities [Member] | Ndtf [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		862
Progress Energy [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	1,076
Derivative assets	3	3
Total assets	3,536	3,392
Derivative liabilities	(37)	(36)
Net assets (liabilities)	3,499	3,356
Progress Energy [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	1
Total assets	2,788	2,666
Derivative liabilities	0	(1)
Net assets (liabilities)	2,788	2,665
Progress Energy [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	3	2
Total assets	748	726
Derivative liabilities	(37)	(35)
Net assets (liabilities)	711	691
Progress Energy [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	2,382
Debt securities, available-for-sale	1,085
Progress Energy [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	2,382
Debt securities, available-for-sale	388
Progress Energy [Member] | Ndtf [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	697
Progress Energy [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	66
Progress Energy [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	18
Progress Energy [Member] | Other Classification [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	48
Progress Energy [Member] | Equity Securities [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		2,222
Progress Energy [Member] | Equity Securities [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		2,222
Progress Energy [Member] | Debt Securities [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		1,108
Progress Energy [Member] | Debt Securities [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		431
Progress Energy [Member] | Debt Securities [Member] | Ndtf [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		677
Progress Energy [Member] | Debt Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		59
Progress Energy [Member] | Debt Securities [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		12
Progress Energy [Member] | Debt Securities [Member] | Other Classification [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		47
Duke Energy Progress [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	781
Derivative assets	2	2
Total assets	2,746	2,594
Derivative liabilities	(24)	(18)
Net assets (liabilities)	2,722	2,576
Duke Energy Progress [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	1
Total assets	2,175	2,040
Derivative liabilities	0	(1)
Net assets (liabilities)	2,175	2,039
Duke Energy Progress [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	2	1
Total assets	571	554
Derivative liabilities	(24)	(17)
Net assets (liabilities)	547	537
Duke Energy Progress [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	1,913
Debt securities, available-for-sale	823
Duke Energy Progress [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	1,913
Debt securities, available-for-sale	254
Duke Energy Progress [Member] | Ndtf [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	569
Duke Energy Progress [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	8
Duke Energy Progress [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	8
Duke Energy Progress [Member] | Equity Securities [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		1,795
Duke Energy Progress [Member] | Equity Securities [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		1,795
Duke Energy Progress [Member] | Debt Securities [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		796
Duke Energy Progress [Member] | Debt Securities [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		243
Duke Energy Progress [Member] | Debt Securities [Member] | Ndtf [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		553
Duke Energy Progress [Member] | Debt Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		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, fair value disclosures		1
Duke Energy Florida [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	295
Derivative assets	1	1
Total assets	780	788
Derivative liabilities	(5)	(12)
Net assets (liabilities)	775	776
Duke Energy Florida [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	603	616
Net assets (liabilities)	603	616
Duke Energy Florida [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	1	1
Total assets	177	172
Derivative liabilities	(5)	(12)
Net assets (liabilities)	172	160
Duke Energy Florida [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	469
Debt securities, available-for-sale	262
Duke Energy Florida [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	469
Debt securities, available-for-sale	134
Duke Energy Florida [Member] | Ndtf [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	128
Duke Energy Florida [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	48
Duke Energy Florida [Member] | Other Classification [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	48
Duke Energy Florida [Member] | Equity Securities [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		427
Duke Energy Florida [Member] | Equity Securities [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		427
Duke Energy Florida [Member] | Debt Securities [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		312
Duke Energy Florida [Member] | Debt Securities [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		188
Duke Energy Florida [Member] | Debt Securities [Member] | Ndtf [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		124
Duke Energy Florida [Member] | Debt Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		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, fair value disclosures		1
Duke Energy Florida [Member] | Debt Securities [Member] | Other Classification [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		47
Duke Energy Ohio [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	8	1
Derivative liabilities	(4)	(5)
Net assets (liabilities)	4	(4)
Duke Energy Ohio [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilities	(4)	(5)
Net assets (liabilities)	(4)	(5)
Duke Energy Ohio [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	8	1
Net assets (liabilities)	8	1
Duke Energy Indiana [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	78
Debt securities, available-for-sale	40
Derivative assets	29	27
Total assets	147	155
Duke Energy Indiana [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0
Total assets	78	97
Duke Energy Indiana [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	40	31
Duke Energy Indiana [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	29	27
Total assets	29	27
Duke Energy Indiana [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	78
Debt securities, available-for-sale	40
Duke Energy Indiana [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	78
Duke Energy Indiana [Member] | Other Classification [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	40
Duke Energy Indiana [Member] | Equity Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		97
Duke Energy Indiana [Member] | Equity Securities [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		97
Duke Energy Indiana [Member] | Debt Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		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, fair value disclosures		31
Piedmont Natural Gas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	4	2
Total assets		3
Derivative liabilities	(153)	(142)
Net assets (liabilities)	(149)	(139)
Piedmont Natural Gas [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	4	2
Total assets		3
Net assets (liabilities)	4	3
Piedmont Natural Gas [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilities	(153)	(142)
Net assets (liabilities)	$ (153)	(142)
Piedmont Natural Gas [Member] | Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		1
Piedmont Natural Gas [Member] | Debt Securities [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value disclosures		$ 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 ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement, transfers between activity levels	$ 0	$ 0	$ 0	$ 0
Derivatives (net)
Balance at beginning of period	(97,000,000)	(91,000,000)	(114,000,000)	(166,000,000)
Purchases, sales, issuances and settlements:
Purchases			56,000,000	55,000,000
Settlements	(14,000,000)	(12,000,000)	(43,000,000)	(30,000,000)
Total (losses) gains included on the Condensed Consolidated Balance Sheet	(5,000,000)	10,000,000	(15,000,000)	48,000,000
Balance at end of period	(116,000,000)	(93,000,000)	(116,000,000)	(93,000,000)
Investments and Derivatives, Net
Balance at beginning of period	(97,000,000)	(91,000,000)	(114,000,000)	(161,000,000)
Total pretax realized or unrealized gains included in comprehensive income				1,000,000
Purchases, sales, issuances and settlements:
Purchases			56,000,000	55,000,000
Sales				(6,000,000)
Settlements	(14,000,000)	(12,000,000)	(43,000,000)	(30,000,000)
Total (losses) gains included on the Condensed Consolidated Balance Sheet	(5,000,000)	10,000,000	(15,000,000)	48,000,000
Balance at end of period	(116,000,000)	(93,000,000)	(116,000,000)	(93,000,000)
Investments [Member]
Investments
Balance at beginning of period		0		5,000,000
Total pretax realized or unrealized gains included in comprehensive income				1,000,000
Purchases, sales, issuances and settlements:
Sales				(6,000,000)
Duke Energy Carolinas [Member] | Investments [Member]
Investments
Balance at beginning of period				3,000,000
Total pretax realized or unrealized gains included in comprehensive income				1,000,000
Purchases, sales, issuances and settlements:
Sales				(4,000,000)
Duke Energy Ohio [Member]
Derivatives (net)
Balance at beginning of period	9,000,000	3,000,000	1,000,000	5,000,000
Purchases, sales, issuances and settlements:
Purchases	0		7,000,000	3,000,000
Settlements	(1,000,000)	(1,000,000)	(2,000,000)	(3,000,000)
Total (losses) gains included on the Condensed Consolidated Balance Sheet			2,000,000	(3,000,000)
Balance at end of period	8,000,000	2,000,000	8,000,000	2,000,000
Duke Energy Indiana [Member]
Derivatives (net)
Balance at beginning of period	44,000,000	51,000,000	27,000,000	16,000,000
Purchases, sales, issuances and settlements:
Purchases	0	0	49,000,000	52,000,000
Settlements	(13,000,000)	(11,000,000)	(41,000,000)	(27,000,000)
Total (losses) gains included on the Condensed Consolidated Balance Sheet	(2,000,000)	(12,000,000)	(6,000,000)	(13,000,000)
Balance at end of period	29,000,000	28,000,000	29,000,000	28,000,000
Piedmont Natural Gas [Member]
Derivatives (net)
Balance at beginning of period	(150,000,000)	(145,000,000)	(142,000,000)	(187,000,000)
Purchases, sales, issuances and settlements:
Total gains (losses) and settlements	(3,000,000)	22,000,000	(11,000,000)	64,000,000
Balance at end of period	$ (153,000,000)	$ (123,000,000)	$ (153,000,000)	$ (123,000,000)

Fair Value Measurements (Quanti

Fair Value Measurements (Quantitative Level 3 Fair Value Disclosures) (Details) $ in Millions	Sep. 30, 2018USD ($)$ / MWh$ / MMBTU	Jun. 30, 2018USD ($)	Dec. 31, 2017USD ($)	Sep. 30, 2017USD ($)$ / MWh$ / MMBTU	Jun. 30, 2017USD ($)	Dec. 31, 2016USD ($)
Fair Value Measurement Inputs and Valuation Techniques
Net derivative asset (liability)	$ (116)	$ (97)	$ (114)	$ (93)	$ (91)	$ (166)
Duke Energy Ohio [Member]
Fair Value Measurement Inputs and Valuation Techniques
Net derivative asset (liability)	8	9	1	$ 2	3	5
Duke Energy Ohio [Member] | Financial Transmission Rights [Member] | Valuation, Market Approach [Member]
Fair Value Measurement Inputs and Valuation Techniques
Net derivative asset (liability)	$ 8		1
Duke Energy Ohio [Member] | Financial Transmission Rights [Member] | Minimum [Member] | Valuation, Market Approach [Member]
Fair Value Measurement Inputs and Valuation Techniques
Input measurements (in usd per MWh and usd per MMBtu) | $ / MWh	1.03			0.07
Duke Energy Ohio [Member] | Financial Transmission Rights [Member] | Maximum [Member] | Valuation, Market Approach [Member]
Fair Value Measurement Inputs and Valuation Techniques
Input measurements (in usd per MWh and usd per MMBtu) | $ / MWh	4.10			1.41
Duke Energy Indiana [Member]
Fair Value Measurement Inputs and Valuation Techniques
Net derivative asset (liability)	$ 29	44	27	$ 28	51	16
Duke Energy Indiana [Member] | Financial Transmission Rights [Member] | Valuation, Market Approach [Member]
Fair Value Measurement Inputs and Valuation Techniques
Net derivative asset (liability)	$ 29		27
Duke Energy Indiana [Member] | Financial Transmission Rights [Member] | Minimum [Member] | Valuation, Market Approach [Member]
Fair Value Measurement Inputs and Valuation Techniques
Input measurements (in usd per MWh and usd per MMBtu) | $ / MWh	(2.32)			(0.77)
Duke Energy Indiana [Member] | Financial Transmission Rights [Member] | Maximum [Member] | Valuation, Market Approach [Member]
Fair Value Measurement Inputs and Valuation Techniques
Input measurements (in usd per MWh and usd per MMBtu) | $ / MWh	8.11			7.44
Piedmont Natural Gas [Member]
Fair Value Measurement Inputs and Valuation Techniques
Net derivative asset (liability)	$ (153)	$ (150)	(142)	$ (123)	$ (145)	$ (187)
Piedmont Natural Gas [Member] | Derivative Financial Instruments, Liabilities [Member] | Discounted Cash Flow [Member]
Fair Value Measurement Inputs and Valuation Techniques
Net derivative asset (liability)	$ (153)		$ (142)
Piedmont Natural Gas [Member] | Derivative Financial Instruments, Liabilities [Member] | Minimum [Member] | Discounted Cash Flow [Member]
Fair Value Measurement Inputs and Valuation Techniques
Input measurements (in usd per MWh and usd per MMBtu) | $ / MMBTU	1.74			2.10
Piedmont Natural Gas [Member] | Derivative Financial Instruments, Liabilities [Member] | Maximum [Member] | Discounted Cash Flow [Member]
Fair Value Measurement Inputs and Valuation Techniques
Input measurements (in usd per MWh and usd per MMBtu) | $ / MMBTU	3.41			2.88

Fair Value Measurements (Other

Fair Value Measurements (Other Fair Value Disclosure) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	$ 53,962	$ 52,279
Long-term debt, fair value	53,949	55,331
Piedmont Natural Gas and Progress Energy [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unamortized debt discount (premium), net	1,600	1,700
Duke Energy Carolinas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	10,395	10,103
Long-term debt, fair value	10,887	11,372
Progress Energy [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	18,912	17,837
Long-term debt, fair value	19,825	20,000
Duke Energy Progress [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	8,154	7,357
Long-term debt, fair value	8,231	7,992
Duke Energy Florida [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	7,371	7,095
Long-term debt, fair value	7,749	7,953
Duke Energy Ohio [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	2,066	2,067
Long-term debt, fair value	2,136	2,249
Duke Energy Indiana [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	3,783	3,783
Long-term debt, fair value	4,178	4,464
Piedmont Natural Gas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	2,138	2,037
Long-term debt, fair value	$ 2,175	$ 2,209

Variable Interest Entities (Nar

Variable Interest Entities (Narrative) (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Variable interest entity, financial or other support, amount	$ 0	$ 0
Cinergy Receivables [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [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 Entities [Line Items]
Variable interest entity ownership interest	50.00%
OVEC [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Variable interest entity ownership interest	9.00%
Duke Energy Ohio [Member] | Cinergy Receivables [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Fixed interest rate added to LIBOR to compute variable rate	1.00%
Duke Energy Indiana [Member] | Cinergy Receivables [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [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	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Variable Interest Entities [Line Items]
Long-Term Debt	$ 50,507	$ 49,035
Duke Energy Carolinas [Member]
Variable Interest Entities [Line Items]
Long-Term Debt	9,589	8,598
Duke Energy Progress [Member]
Variable Interest Entities [Line Items]
Long-Term Debt	7,401	7,204
Duke Energy Florida [Member]
Variable Interest Entities [Line Items]
Long-Term Debt	$ 7,102	6,327
Cinergy Receivables [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Line of credit facility, expiration date	Dec. 1, 2020
Facility size	$ 325
Long-Term Debt	325	325
Accounts receivable from securitization	$ 504	545
DERF [Member] | Duke Energy Carolinas [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Line of credit facility, expiration date	Dec. 1, 2020
Facility size	$ 450
Long-Term Debt	450	450
Accounts receivable from securitization	$ 795	640
DEPR [Member] | Duke Energy Progress [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Line of credit facility, expiration date	Feb. 1, 2021
Facility size	$ 300
Long-Term Debt	300	300
Accounts receivable from securitization	$ 635	459
DEFR [Member] | Duke Energy Florida [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Line of credit facility, expiration date	Apr. 1, 2021
Facility size	$ 225
Long-Term Debt	225	225
Accounts receivable from securitization	$ 456	$ 317

Variable Interest Entities (S_2

Variable Interest Entities (Schedule of Consolidated VIEs) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Regulatory assets, current	$ 1,906	$ 1,437
Other, current assets	1,092	634
Regulatory assets, noncurrent	12,616	12,442
Property, plant and equipment, cost	132,677	127,507
Accumulated depreciation and amortization	(43,200)	(41,537)
Other noncurrent assets	3,112	2,960
Current Liabilities: Other	1,703	1,865
Current maturities of long-term debt	3,455	3,244
Long-Term Debt	50,507	49,035
Deferred income taxes	7,765	6,621
Noncurrent Liabilities: Other	1,477	1,581
Duke Energy Carolinas [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Regulatory assets, current	435	299
Other, current assets	55	19
Regulatory assets, noncurrent	3,188	2,853
Property, plant and equipment, cost	44,086	42,939
Accumulated depreciation and amortization	(15,536)	(15,063)
Other noncurrent assets	1,009	979
Current Liabilities: Other	419	486
Current maturities of long-term debt	506	1,205
Long-Term Debt	9,589	8,598
Deferred income taxes	3,639	3,413
Noncurrent Liabilities: Other	508	566
Duke Energy Progress [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Regulatory assets, current	677	352
Other, current assets	112	97
Regulatory assets, noncurrent	3,822	3,507
Property, plant and equipment, cost	31,091	29,583
Accumulated depreciation and amortization	(11,484)	(10,903)
Other noncurrent assets	653	599
Current Liabilities: Other	353	376
Current maturities of long-term debt	603	3
Long-Term Debt	7,401	7,204
Deferred income taxes	2,076	1,883
Noncurrent Liabilities: Other	48	45
Duke Energy Florida [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Regulatory assets, current	445	389
Other, current assets	27	86
Regulatory assets, noncurrent	2,165	2,503
Property, plant and equipment, cost	18,722	17,730
Accumulated depreciation and amortization	(5,161)	(4,947)
Other noncurrent assets	315	284
Current Liabilities: Other	315	334
Current maturities of long-term debt	269	768
Long-Term Debt	7,102	6,327
Deferred income taxes	2,012	1,761
Noncurrent Liabilities: Other	56	108
DEFPF [Member] | Duke Energy Florida [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Receivables of VIEs	7	4
Regulatory assets, current	52	51
Other, current assets	14	40
Regulatory assets, noncurrent	1,055	1,091
Current Liabilities: Other	3	10
Current maturities of long-term debt	53	53
Long-Term Debt	1,111	1,164
DERF [Member] | Duke Energy Carolinas [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Receivables of VIEs	795	640
Long-Term Debt	450	450
DEPR [Member] | Duke Energy Progress [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Receivables of VIEs	635	459
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]
Receivables of VIEs	456	317
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]
Receivables of VIEs	504	545
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	203	174
Property, plant and equipment, cost	4,025	3,923
Accumulated depreciation and amortization	(695)	(591)
Other noncurrent assets	268	50
Current maturities of long-term debt	175	170
Long-Term Debt	1,604	1,700
Deferred income taxes		(148)
Noncurrent Liabilities: Other	$ 225	$ 241

Variable Interest Entities (S_3

Variable Interest Entities (Schedule of Non-Consolidated VIEs) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Variable Interest Entities [Line Items]
Investments in equity method unconsolidated affiliates	$ 1,328	$ 1,175
Other noncurrent assets	3,112	2,960
Taxes accrued	674	551
Current Liabilities: Other	1,703	1,865
Deferred income taxes	7,765	6,621
Noncurrent Liabilities: Other	1,477	1,581
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Investments in equity method unconsolidated affiliates	966	919
Other noncurrent assets		17
Total assets	966	936
Taxes accrued		(29)
Current Liabilities: Other	3	4
Deferred income taxes	14	42
Noncurrent Liabilities: Other	11	12
Total liabilities	28	29
Net assets	938	907
Pipeline Investments [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Investments in equity method unconsolidated affiliates	729	697
Other noncurrent assets		17
Total assets	729	714
Taxes accrued		(29)
Deferred income taxes	14	42
Total liabilities	14	13
Net assets	715	701
Commercial Renewables [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Investments in equity method unconsolidated affiliates	190	180
Total assets	190	180
Net assets	190	180
Other VIEs [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Investments in equity method unconsolidated affiliates	47	42
Total assets	47	42
Current Liabilities: Other	3	4
Noncurrent Liabilities: Other	11	12
Total liabilities	14	16
Net assets	33	26
Duke Energy Ohio [Member]
Variable Interest Entities [Line Items]
Receivables from affiliated companies	71	133
Other noncurrent assets	62	21
Taxes accrued	159	190
Current Liabilities: Other	67	71
Deferred income taxes	790	781
Noncurrent Liabilities: Other	113	108
Duke Energy Ohio [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Receivables from affiliated companies	56	87
Total assets	56	87
Net assets	56	87
Duke Energy Indiana [Member]
Variable Interest Entities [Line Items]
Receivables from affiliated companies	98	125
Other noncurrent assets	233	189
Taxes accrued	44	95
Current Liabilities: Other	109	104
Deferred income taxes	988	925
Noncurrent Liabilities: Other	31	18
Duke Energy Indiana [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Receivables from affiliated companies	94	106
Total assets	94	106
Net assets	$ 94	$ 106

Variable Interest Entities (Pip

Variable Interest Entities (Pipeline Investments) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Variable Interest Entities [Line Items]
Investments in joint ventures	$ 1,328	$ 1,175
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Variable interest entity, nonconsolidated, carrying amount, liabilities	28	29
Investments in joint ventures	966	919
Piedmont Natural Gas [Member]
Variable Interest Entities [Line Items]
Investments in joint ventures	$ 63	61
Atlantic Coast Pipeline [Member]
Variable Interest Entities [Line Items]
Ownership percentage	47.00%
Atlantic Coast Pipeline [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Equity method investment, line of credit facility, maximum borrowing capacity		3,400
Investments in joint ventures	$ 704	397
Atlantic Coast Pipeline [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Revolving Credit Facility [Member]
Variable Interest Entities [Line Items]
Variable interest entity, entity maximum loss exposure, percent	47.00%
Variable interest entity, nonconsolidated, carrying amount, liabilities	$ 486
Sabal Trail Transmission Pipeline [Member]
Variable Interest Entities [Line Items]
Investments in joint ventures	$ 112
Ownership percentage	7.50%
Sabal Trail Transmission Pipeline [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Investments in joint ventures		219
Constitution Pipeline [Member]
Variable Interest Entities [Line Items]
Ownership percentage	24.00%
Constitution Pipeline [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Equity method investment, OTTI	$ 55
Investments in joint ventures	25	81
Pipeline Investments [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Investments in joint ventures	$ 729	$ 697

Variable Interest Entities (Fai

Variable Interest Entities (Fair Value Assumptions) (Details) - Variable Interest Entity, Not Primary Beneficiary [Member] - Cinergy Receivables [Member]	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Duke Energy Ohio [Member]
Variable Interest Entities [Line Items]
Anticipated credit loss ratio	0.50%	0.50%
Discount rate	2.90%	2.10%
Receivable turnover rate	13.60%	13.50%
Duke Energy Indiana [Member]
Variable Interest Entities [Line Items]
Anticipated credit loss ratio	0.30%	0.30%
Discount rate	2.90%	2.10%
Receivable turnover rate	10.90%	10.70%

Variable Interest Entities (Rec

Variable Interest Entities (Receivables Sold) (Details) - Variable Interest Entity, Not Primary Beneficiary [Member] - Cinergy Receivables [Member] - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Duke Energy Ohio [Member]
Variable Interest Entities [Line Items]
Receivables sold	$ 218	$ 273
Less: Retained interests	56	87
Net receivables sold	162	186
Duke Energy Indiana [Member]
Variable Interest Entities [Line Items]
Receivables sold	326	312
Less: Retained interests	94	106
Net receivables sold	$ 232	$ 206

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	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Duke Energy Ohio [Member]
Variable Interest Entities [Line Items]
Receivables sold	$ 450	$ 438	$ 1,478	$ 1,392
Loss recognized on sale	4	2	10	7
Cash proceeds from receivables sold	449	434	1,499	1,421
Collection fees received		1	1	1
Return received on retained interests	2		5	2
Duke Energy Indiana [Member]
Variable Interest Entities [Line Items]
Receivables sold	754	720	2,140	2,047
Loss recognized on sale	5	3	12	9
Cash proceeds from receivables sold	743	713	2,140	2,064
Collection fees received			1	1
Return received on retained interests	$ 3	$ 2	$ 7	$ 5

Revenue (Narrative) (Details)

Revenue (Narrative) (Details) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contracts with customers	$ 6,451,000,000	$ 17,845,000,000
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contracts with customers		$ 0

Revenue (Remaining Performance

Revenue (Remaining Performance Obligations) (Details) $ in Millions	Sep. 30, 2018USD ($)
Progress Energy [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 24
Revenue, remaining performance obligation, expected timing of satisfaction, period	3 months
Progress Energy [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 112
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Progress Energy [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 121
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Progress Energy [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 80
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Progress Energy [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 82
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Progress Energy [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 81
Progress Energy [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	500
Duke Energy Progress [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 2
Revenue, remaining performance obligation, expected timing of satisfaction, period	3 months
Duke Energy Progress [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 9
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Duke Energy Progress [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 9
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Duke Energy Progress [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 9
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Duke Energy Progress [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 9
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Duke Energy Progress [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 18
Duke Energy Progress [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	56
Duke Energy Florida [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 22
Revenue, remaining performance obligation, expected timing of satisfaction, period	3 months
Duke Energy Florida [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 103
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Duke Energy Florida [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 112
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Duke Energy Florida [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 71
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Duke Energy Florida [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 73
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Duke Energy Florida [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 63
Duke Energy Florida [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	444
Duke Energy Indiana [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 2
Revenue, remaining performance obligation, expected timing of satisfaction, period	3 months
Duke Energy Indiana [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 9
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Duke Energy Indiana [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 10
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Duke Energy Indiana [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 5
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Duke Energy Indiana [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 26
Piedmont Natural Gas [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-07-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 18
Piedmont Natural Gas [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, expected timing of satisfaction, period	3 months
Piedmont Natural Gas [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 71
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Piedmont Natural Gas [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 70
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Piedmont Natural Gas [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 65
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Piedmont Natural Gas [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 64
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Piedmont Natural Gas [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 462
Piedmont Natural Gas [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 750

Revenue (Disaggregation of Reve

Revenue (Disaggregation of Revenue) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 6,451		$ 17,845
Revenue from sources other than contracts with customers	177		561
Total operating revenues	6,628	$ 6,482	18,406	$ 17,766
Electric Utilities and Infrastructure [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	6,141		16,413
Total operating revenues	6,253	6,122	16,783	16,211
Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2,729		7,264
Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | General [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,763		4,619
Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	835		2,235
Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	589		1,737
Electric Utilities and Infrastructure [Member] | Other Revenues [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	225		558
Gas Utilities and Infrastructure [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	233		1,244
Total operating revenues	232	249	1,229	1,175
Gas Utilities and Infrastructure [Member] | Natural Gas, US Regulated [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	116		682
Gas Utilities and Infrastructure [Member] | Natural Gas, US Regulated [Member] | Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	66		354
Gas Utilities and Infrastructure [Member] | Natural Gas, US Regulated [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	28		107
Gas Utilities and Infrastructure [Member] | Other Revenues [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	23		101
Commercial Renewables [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	61		141
Total operating revenues	127	95	347	333
Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	16		47
Total operating revenues	16	16	47	47
Duke Energy Carolinas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2,051		5,391
Revenue from sources other than contracts with customers	39		134
Total operating revenues	2,090	2,136	5,525	5,581
Duke Energy Carolinas [Member] | Electric Utilities and Infrastructure [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2,051		5,391
Duke Energy Carolinas [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	823		2,263
Duke Energy Carolinas [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | General [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	635		1,608
Duke Energy Carolinas [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	352		893
Duke Energy Carolinas [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	132		366
Duke Energy Carolinas [Member] | Electric Utilities and Infrastructure [Member] | Other Revenues [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	109		261
Progress Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2,977		7,922
Revenue from sources other than contracts with customers	68		197
Total operating revenues	3,045	2,864	8,119	7,435
Progress Energy [Member] | Electric Utilities and Infrastructure [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2,977		7,922
Progress Energy [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,425		3,636
Progress Energy [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | General [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	800		2,109
Progress Energy [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	246		678
Progress Energy [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	372		1,140
Progress Energy [Member] | Electric Utilities and Infrastructure [Member] | Other Revenues [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	134		359
Duke Energy Progress [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,547		4,234
Revenue from sources other than contracts with customers	35		99
Total operating revenues	1,582	1,460	4,333	3,878
Duke Energy Progress [Member] | Electric Utilities and Infrastructure [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,547		4,234
Duke Energy Progress [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	572		1,540
Duke Energy Progress [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | General [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	373		972
Duke Energy Progress [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	177		481
Duke Energy Progress [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	335		1,019
Duke Energy Progress [Member] | Electric Utilities and Infrastructure [Member] | Other Revenues [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	90		222
Duke Energy Florida [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,430		3,688
Revenue from sources other than contracts with customers	32		92
Total operating revenues	1,462	1,401	3,780	3,551
Duke Energy Florida [Member] | Electric Utilities and Infrastructure [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,430		3,688
Duke Energy Florida [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	853		2,096
Duke Energy Florida [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | General [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	427		1,137
Duke Energy Florida [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	69		197
Duke Energy Florida [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	37		121
Duke Energy Florida [Member] | Electric Utilities and Infrastructure [Member] | Other Revenues [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	44		137
Duke Energy Ohio [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	466		1,435
Revenue from sources other than contracts with customers	3		17
Total operating revenues	469	471	1,452	1,426
Duke Energy Ohio [Member] | Electric Utilities and Infrastructure [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	371		1,040
Total operating revenues	373	371	1,055	1,036
Duke Energy Ohio [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	203		564
Duke Energy Ohio [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | General [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	112		318
Duke Energy Ohio [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	33		96
Duke Energy Ohio [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	3		5
Duke Energy Ohio [Member] | Electric Utilities and Infrastructure [Member] | Other Revenues [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	20		57
Duke Energy Ohio [Member] | Gas Utilities and Infrastructure [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	83		359
Total operating revenues	84	90	361	360
Duke Energy Ohio [Member] | Gas Utilities and Infrastructure [Member] | Natural Gas, US Regulated [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	59		236
Duke Energy Ohio [Member] | Gas Utilities and Infrastructure [Member] | Natural Gas, US Regulated [Member] | Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	20		97
Duke Energy Ohio [Member] | Gas Utilities and Infrastructure [Member] | Natural Gas, US Regulated [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	3		13
Duke Energy Ohio [Member] | Gas Utilities and Infrastructure [Member] | Other Revenues [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1		13
Duke Energy Ohio [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	12		36
Duke Energy Indiana [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	809		2,245
Revenue from sources other than contracts with customers	10		43
Total operating revenues	819	802	2,288	2,302
Duke Energy Indiana [Member] | Electric Utilities and Infrastructure [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	809		2,245
Duke Energy Indiana [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	279		802
Duke Energy Indiana [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | General [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	218		584
Duke Energy Indiana [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	202		567
Duke Energy Indiana [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	81		226
Duke Energy Indiana [Member] | Electric Utilities and Infrastructure [Member] | Other Revenues [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	29		66
Piedmont Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	162		924
Revenue from sources other than contracts with customers	10		16
Total operating revenues	172	$ 183	940	$ 884
Piedmont Natural Gas [Member] | Gas Utilities and Infrastructure [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	162		924
Piedmont Natural Gas [Member] | Gas Utilities and Infrastructure [Member] | Natural Gas, US Regulated [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	57		446
Piedmont Natural Gas [Member] | Gas Utilities and Infrastructure [Member] | Natural Gas, US Regulated [Member] | Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	46		257
Piedmont Natural Gas [Member] | Gas Utilities and Infrastructure [Member] | Natural Gas, US Regulated [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	24		93
Piedmont Natural Gas [Member] | Gas Utilities and Infrastructure [Member] | Natural Gas, US Regulated [Member] | Power Generation [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	13		40
Piedmont Natural Gas [Member] | Gas Utilities and Infrastructure [Member] | Other Revenues [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 22		$ 88

Revenue (Unbilled Revenues) (De

Revenue (Unbilled Revenues) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	$ 802	$ 944
Duke Energy Carolinas [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	278	342
Progress Energy [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	283	228
Duke Energy Progress [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	163	143
Duke Energy Florida [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	120	85
Duke Energy Ohio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	2	4
Duke Energy Indiana [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	25	21
Piedmont Natural Gas [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	3	86
Cinergy Receivables [Member] | Duke Energy Ohio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	68	104
Cinergy Receivables [Member] | Duke Energy Indiana [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	$ 121	$ 132

Common Stock (Earnings Per Shar

Common Stock (Earnings Per Share Data) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Equity [Abstract]
Income from continuing operations attributable to Duke Energy common stockholders excluding impact of participating securities	$ 1,077	$ 954	$ 2,199	$ 2,356
Average shares, basic	713	700	705	700
Equity Forwards, shares	1		1
Average shares, diluted	714	700	706	700
EPS, basic (usd per share)	$ 1.51	$ 1.36	$ 3.12	$ 3.37
EPS, diluted (usd per share)	$ 1.51	$ 1.36	$ 3.11	$ 3.37
Number of stock options and performance and unvested stock awards excluded from the dilutive securities calculation	2	2	2	2
Dividends declared per share (usd per share)	$ 0.9275	$ 0.89	$ 2.7075	$ 2.60

Common Stock (Equity Securities

Common Stock (Equity Securities Offering) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	Feb. 20, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2018
Forward Contract Indexed to Issuer's Equity [Line Items]
Maximum value of shares to be issued under ATM program	$ 1,000
Proceeds from the issuance of common stock				$ 834
Forward contract indexed to issuer's equity, shares				1.1
Stock issued during period, shares, DRIP				1.7
Stock issued during period, value, DRIP				$ 134
ATM [Member]
Forward Contract Indexed to Issuer's Equity [Line Items]
Settlement alternative, shares				2.6
ATM [Member] | Wells Fargo Bank [Member]
Forward Contract Indexed to Issuer's Equity [Line Items]
Shares offered		1.3
Forward contract indexed to issuer's equity, forward rate per share		$ 72.02
ATM [Member] | Citibank [Member]
Forward Contract Indexed to Issuer's Equity [Line Items]
Shares offered		1.3
Forward contract indexed to issuer's equity, forward rate per share		$ 78.71
Equity Forwards [Member]
Forward Contract Indexed to Issuer's Equity [Line Items]
Shares offered			21.3
Forward contract indexed to issuer's equity, forward rate per share			$ 74.07
Sales price			$ 75
Settlement alternative, shares			21.3
Shares, Issued		10.6
Proceeds from the issuance of common stock		$ 781

Stock-Based Compensation (Sched

Stock-Based Compensation (Schedule of Stock-Based Compensation Expense) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pretax stock-based compensation cost	$ 23	$ 17	$ 59	$ 50
Stock-based compensation costs capitalized	1	1	3	2
Stock-based compensation expense	22	16	56	48
Tax benefit associated with stock-based compensation expense	5	6	13	18
Restricted Stock Units Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pretax stock-based compensation cost	10	10	32	30
Performance Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pretax stock-based compensation cost	$ 13	$ 7	$ 27	$ 20

Employee Benefit Plans (Plan Co

Employee Benefit Plans (Plan Contributions) (Details) - Qualified Pension Plan [Member] - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Contributions by Employer	$ 141	$ 8
Duke Energy Carolinas [Member]
Defined Benefit Plan Disclosure [Line Items]
Contributions by Employer	46
Progress Energy [Member]
Defined Benefit Plan Disclosure [Line Items]
Contributions by Employer	45
Duke Energy Progress [Member]
Defined Benefit Plan Disclosure [Line Items]
Contributions by Employer	25
Duke Energy Florida [Member]
Defined Benefit Plan Disclosure [Line Items]
Contributions by Employer	20
Duke Energy Indiana [Member]
Defined Benefit Plan Disclosure [Line Items]
Contributions by Employer	$ 8
Duke Energy Ohio [Member]
Defined Benefit Plan Disclosure [Line Items]
Contributions by Employer		$ 4

Employee Benefit Plans (Compone

Employee Benefit Plans (Components of Net Periodic Pension Costs) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Qualified Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 47	$ 40	$ 137	$ 120
Interest cost on projected benefit obligation	74	82	224	246
Expected return on plan assets	(140)	(136)	(420)	(408)
Amortization of actuarial loss (gain)	33	36	99	108
Amortization of prior service (credit) cost	(8)	(6)	(24)	(18)
Other		2		6
Net periodic costs	6	18	16	54
Qualified Pension Plan [Member] | Duke Energy Carolinas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	15	12	45	36
Interest cost on projected benefit obligation	18	20	54	60
Expected return on plan assets	(37)	(35)	(111)	(106)
Amortization of actuarial loss (gain)	7	8	21	24
Amortization of prior service (credit) cost	(2)	(2)	(6)	(6)
Net periodic costs	1	3	3	8
Qualified Pension Plan [Member] | Progress Energy [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	13	12	39	36
Interest cost on projected benefit obligation	24	25	70	75
Expected return on plan assets	(45)	(43)	(133)	(129)
Amortization of actuarial loss (gain)	11	14	33	42
Amortization of prior service (credit) cost	(1)	(1)	(3)	(3)
Other		1		3
Net periodic costs	2	8	6	24
Qualified Pension Plan [Member] | Duke Energy Progress [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	7	6	22	18
Interest cost on projected benefit obligation	10	12	31	36
Expected return on plan assets	(21)	(21)	(63)	(63)
Amortization of actuarial loss (gain)	6	6	16	18
Amortization of prior service (credit) cost			(1)
Other				1
Net periodic costs	2	3	5	10
Qualified Pension Plan [Member] | Duke Energy Florida [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	5	5	16	15
Interest cost on projected benefit obligation	13	13	38	39
Expected return on plan assets	(23)	(21)	(69)	(63)
Amortization of actuarial loss (gain)	6	7	18	21
Amortization of prior service (credit) cost			(1)
Net periodic costs	1	4	2	12
Qualified Pension Plan [Member] | Duke Energy Ohio [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	2	1	4	3
Interest cost on projected benefit obligation	4	4	13	14
Expected return on plan assets	(7)	(7)	(21)	(21)
Amortization of actuarial loss (gain)	1	1	3	3
Net periodic costs		(1)	(1)	(1)
Qualified Pension Plan [Member] | Duke Energy Indiana [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	2	2	7	6
Interest cost on projected benefit obligation	6	7	18	21
Expected return on plan assets	(10)	(11)	(31)	(33)
Amortization of actuarial loss (gain)	2	3	6	9
Net periodic costs		1		3
Qualified Pension Plan [Member] | Piedmont Natural Gas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	2	3	6	9
Interest cost on projected benefit obligation	3	3	9	9
Expected return on plan assets	(6)	(6)	(18)	(18)
Amortization of actuarial loss (gain)	3	3	9	9
Amortization of prior service (credit) cost	(3)	(1)	(9)	(3)
Other				1
Net periodic costs	(1)	2	(3)	7
Non-Qualified Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost			1
Interest cost on projected benefit obligation	3	4	9	10
Amortization of actuarial loss (gain)	2	2	6	6
Amortization of prior service (credit) cost			(1)
Net periodic costs	5	6	15	16
Non-Qualified Pension Plan [Member] | Duke Energy Carolinas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost			1
Interest cost on projected benefit obligation				1
Net periodic costs			1	1
Non-Qualified Pension Plan [Member] | Progress Energy [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost on projected benefit obligation	1	1	3	3
Amortization of actuarial loss (gain)		1		3
Amortization of prior service (credit) cost			1
Net periodic costs	1	2	4	6
Non-Qualified Pension Plan [Member] | Duke Energy Progress [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost on projected benefit obligation		1	1	2
Net periodic costs		1	1	2
Non-Qualified Pension Plan [Member] | Duke Energy Florida [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost on projected benefit obligation		1	1	2
Net periodic costs		1	1	2
Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	2	1	5	3
Interest cost on projected benefit obligation	7	9	21	27
Expected return on plan assets	(4)	(3)	(10)	(10)
Amortization of actuarial loss (gain)	2	2	5	6
Amortization of prior service (credit) cost	(5)	(29)	(15)	(87)
Net periodic costs	2	(20)	6	(61)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Carolinas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost			1
Interest cost on projected benefit obligation	2	2	5	6
Expected return on plan assets	(2)	(2)	(6)	(6)
Amortization of actuarial loss (gain)	1		2	(2)
Amortization of prior service (credit) cost	(1)	(2)	(3)	(6)
Net periodic costs		(2)	(1)	(8)
Other Post-Retirement Benefit Plans [Member] | Progress Energy [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost on projected benefit obligation	3	4	9	11
Amortization of actuarial loss (gain)		5	1	15
Amortization of prior service (credit) cost	(2)	(21)	(6)	(63)
Net periodic costs	1	(12)	4	(37)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Progress [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost on projected benefit obligation	2	2	5	6
Amortization of actuarial loss (gain)		3		9
Amortization of prior service (credit) cost		(14)		(41)
Net periodic costs	2	(9)	5	(26)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Florida [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost on projected benefit obligation	1	2	4	6
Amortization of actuarial loss (gain)		2		6
Amortization of prior service (credit) cost	(1)	(8)	(4)	(23)
Net periodic costs		(4)		(11)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Ohio [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost on projected benefit obligation			1
Amortization of actuarial loss (gain)				(1)
Net periodic costs			1	(1)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Indiana [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost on projected benefit obligation	1	1	3	1
Amortization of actuarial loss (gain)	1		3
Net periodic costs	$ 2	$ 1	6	$ 1
Other Post-Retirement Benefit Plans [Member] | Piedmont Natural Gas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Amortization of prior service (credit) cost			(1)
Net periodic costs			$ (1)

Employee Benefit Plans (Employe

Employee Benefit Plans (Employee Savings Plans) (Details) - Employee Savings Plan [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Defined Contribution Plan Disclosure [Line Items]
Employer contributions	$ 49	$ 43	$ 167	$ 147
Duke Energy Carolinas [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions	15	14	53	49
Progress Energy [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions	13	12	45	42
Duke Energy Progress [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions	9	9	31	30
Duke Energy Florida [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions	4	4	14	13
Duke Energy Ohio [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions		1	2	3
Duke Energy Indiana [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions	3	2	8	7
Piedmont Natural Gas [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions	$ 4	$ 2	$ 10	$ 5

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Reclassification of ATM credit carryforwards	$ 573
Provisional adjustments for TCJA	3	$ 76	$ 73
Regulatory liability representing revaluation of deferred tax balances	$ 57

Income Taxes (Effective Tax Rat

Income Taxes (Effective Tax Rates) (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Reconciliation of Income Tax Expense at the U.S. Federal Statutory Tax Rate to the Actual Tax Expense from Continuing Operations [Abstract]
Effective tax rate	13.70%	27.60%	17.00%	30.40%
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]
Effective tax rate	22.60%	32.90%	22.30%	34.10%
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]
Effective tax rate	18.80%	29.10%	17.00%	31.90%
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]
Effective tax rate	20.60%	31.70%	18.40%	32.40%
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]
Effective tax rate	15.00%	34.80%	16.30%	36.10%
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]
Effective tax rate	16.00%	33.30%	16.00%	34.40%
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]
Effective tax rate	22.70%	38.30%	24.70%	39.00%
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]
Effective tax rate	34.40%	47.60%	20.60%	36.10%

Subsequent Events (Narrative) (

Subsequent Events (Narrative) (Details) - USD ($) $ in Millions	Oct. 10, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Subsequent Event [Line Items]
Operation, maintenance and other		$ 1,584	$ 1,476	$ 4,592	$ 4,385
Hurricane Michael Storm Damage [Member] | Estimated Impact [Member]
Subsequent Event [Line Items]
Operation, maintenance and other	$ 235
Estimated capital cost	$ 185