Duke Energy Carolinas 10-Q 3 Nov 17 2017 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information	9 Months Ended
	Sep. 30, 2017shares
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, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Common Stock, Shares Outstanding	699,975,614
Trading Symbol	DUK
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
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
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
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
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
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
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

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, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Operating Revenues
Regulated electric	$ 6,091	$ 6,303	$ 16,122	$ 16,321
Regulated natural gas	247	89	1,168	355
Nonregulated electric and other	144	184	476	490
Total operating revenues	6,482	6,576	17,766	17,166
Operating Expenses
Fuel used in electric generation and purchased power	1,863	2,031	4,853	5,140
Cost of natural gas	68	6	402	64
Operation, maintenance and other	1,442	1,460	4,282	4,227
Depreciation and amortization	900	819	2,594	2,402
Property and other taxes	313	302	924	887
Impairment charges	207	10	216	14
Total operating expenses	4,793	4,628	13,271	12,734
Gains (Losses) on Sales of Other Assets and Other, net	6	6	24	21
Operating Income (Loss)	1,695	1,954	4,519	4,453
Other Income and Expenses
Equity in earnings (losses) of unconsolidated affiliates	36	(60)	101	(37)
Other income and expenses, net	88	86	255	237
Total other income and expenses	124	26	356	200
Interest Expense	498	464	1,475	1,431
Income (Loss) From Continuing Operations Before Income Taxes	1,321	1,516	3,400	3,222
Income Tax Expense (Benefit) from Continuing Operations	364	515	1,035	1,020
Income from Continuing Operations	957	1,001	2,365	2,202
(Loss) Income From Discontinued Operations, net of tax	(2)	180	(4)	190
Net income	955	1,181	2,361	2,392
Less: Net Income Attributable to Noncontrolling Interests	1	5	5	13
Net Income (Loss) Attributable to Parent	954	1,176	2,356	2,379
Other Comprehensive Income (Loss), net of tax
Pension and OPEB adjustments	0	0	2	2
Net unrealized (losses) gains on cash flow hedges	2	6	(2)	(19)
Reclassification into earnings from cash flow hedges	(2)	1	3	3
Unrealized gains on available-for-sale securities	2	0	10	7
Other Comprehensive Income, net of tax	2	(5)	13	88
Comprehensive Income	957	1,176	2,374	2,480
Less: Comprehensive Income Attributable to Noncontrolling Interests	1	4	5	16
Comprehensive Income (Loss) Attributable to Parent	$ 956	$ 1,172	$ 2,369	$ 2,464
Income from continuing operations attributable to Duke Energy Corporation common stockholders
Basic (usd per share)	$ 1.36	$ 1.44	$ 3.37	$ 3.19
Diluted (usd per share)	1.36	1.44	3.37	3.18
Income (Loss) from discontinued operations attributable to Duke Energy Corporation common stockholders
Basic (usd per share)		0.26	(0.01)	0.26
Diluted (usd per share)		0.26	(0.01)	0.26
Net income attributable to Duke Energy Corporation common stockholders
Basic (usd per share)	1.36	1.70	3.36	3.45
Diluted (usd per share)	$ 1.36	$ 1.70	$ 3.36	$ 3.44
Weighted average shares outstanding
Basic (shares)	700	689	700	689
Diluted (shares)	700	691	700	690
Duke Energy Carolinas [Member]
Operating Revenues
Total operating revenues	$ 2,136	$ 2,226	$ 5,581	$ 5,641
Operating Expenses
Fuel used in electric generation and purchased power	531	581	1,394	1,391
Operation, maintenance and other	480	493	1,431	1,481
Depreciation and amortization	281	268	804	802
Property and other taxes	67	68	206	206
Total operating expenses	1,359	1,410	3,835	3,880
Gains (Losses) on Sales of Other Assets and Other, net		(1)		(1)
Operating Income (Loss)	777	815	1,746	1,760
Other Income and Expenses
Other income and expenses, net	26	39	99	121
Interest Expense	108	102	314	316
Income (Loss) From Continuing Operations Before Income Taxes	695	752	1,531	1,565
Income Tax Expense (Benefit) from Continuing Operations	229	258	522	539
Net Income (Loss) Attributable to Parent	466	494	1,009	1,026
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 (Loss) Attributable to Parent	466	494	1,010	1,027
Progress Energy [Member]
Operating Revenues
Total operating revenues	2,864	2,965	7,435	7,645
Operating Expenses
Fuel used in electric generation and purchased power	1,031	1,120	2,588	2,832
Operation, maintenance and other	572	582	1,650	1,699
Depreciation and amortization	334	318	958	904
Property and other taxes	140	136	386	375
Impairment charges	135	1	137	4
Total operating expenses	2,212	2,157	5,719	5,814
Gains (Losses) on Sales of Other Assets and Other, net	5	6	19	18
Operating Income (Loss)	657	814	1,735	1,849
Other Income and Expenses
Other income and expenses, net	20	31	65	79
Interest Expense	193	177	595	497
Income (Loss) From Continuing Operations Before Income Taxes	484	668	1,205	1,431
Income Tax Expense (Benefit) from Continuing Operations	141	219	384	496
Net income	343	449	821	935
Less: Net Income Attributable to Noncontrolling Interests	2	3	7	8
Net Income (Loss) Attributable to Parent	341	446	814	927
Other Comprehensive Income (Loss), net of tax
Pension and OPEB adjustments	3		5	2
Net unrealized (losses) gains on cash flow hedges	(2)		4
Reclassification into earnings from cash flow hedges		1		4
Unrealized gains on available-for-sale securities	1	1	3	2
Other Comprehensive Income, net of tax	2	2	12	8
Comprehensive Income	345	451	833	943
Less: Comprehensive Income Attributable to Noncontrolling Interests	2	3	7	8
Comprehensive Income (Loss) Attributable to Parent	343	448	826	935
Duke Energy Progress [Member]
Operating Revenues
Total operating revenues	1,460	1,583	3,878	4,103
Operating Expenses
Fuel used in electric generation and purchased power	475	569	1,214	1,441
Operation, maintenance and other	352	360	1,032	1,067
Depreciation and amortization	182	176	536	526
Property and other taxes	40	40	120	119
Impairment charges		1		1
Total operating expenses	1,049	1,146	2,902	3,154
Gains (Losses) on Sales of Other Assets and Other, net		1	3	2
Operating Income (Loss)	411	438	979	951
Other Income and Expenses
Other income and expenses, net	14	18	47	47
Interest Expense	65	61	217	188
Income (Loss) From Continuing Operations Before Income Taxes	360	395	809	810
Income Tax Expense (Benefit) from Continuing Operations	114	124	262	271
Net Income (Loss) Attributable to Parent	246	271	547	539
Other Comprehensive Income (Loss), net of tax
Comprehensive Income (Loss) Attributable to Parent	246	271	547	539
Duke Energy Florida [Member]
Operating Revenues
Total operating revenues	1,401	1,381	3,551	3,538
Operating Expenses
Fuel used in electric generation and purchased power	557	550	1,374	1,391
Operation, maintenance and other	216	219	610	623
Depreciation and amortization	154	142	423	378
Property and other taxes	99	96	265	256
Impairment charges	135	1	137	4
Total operating expenses	1,161	1,008	2,809	2,652
Operating Income (Loss)	240	373	742	886
Other Income and Expenses
Other income and expenses, net	15	11	45	30
Interest Expense	71	62	211	143
Income (Loss) From Continuing Operations Before Income Taxes	184	322	576	773
Income Tax Expense (Benefit) from Continuing Operations	64	116	208	286
Net Income (Loss) Attributable to Parent	120	206	368	487
Other Comprehensive Income (Loss), net of tax
Unrealized gains on available-for-sale securities	1	1	3	2
Other Comprehensive Income, net of tax			3	2
Comprehensive Income (Loss) Attributable to Parent	121	207	371	489
Duke Energy Ohio [Member]
Operating Revenues
Regulated electric	371	390	1,036	1,053
Regulated natural gas	90	89	360	358
Nonregulated electric and other	10	10	30	22
Total operating revenues	471	489	1,426	1,433
Operating Expenses
Fuel used in electric generation and purchased power	100	129	283	340
Fuel used in electric generation and purchased power – nonregulated	13	14	42	37
Cost of natural gas	5	6	69	64
Operation, maintenance and other	124	126	385	367
Depreciation and amortization	63	50	193	175
Property and other taxes	65	59	204	195
Impairment charges			1
Total operating expenses	370	384	1,177	1,178
Gains (Losses) on Sales of Other Assets and Other, net	1	1	1	2
Operating Income (Loss)	102	106	250	257
Other Income and Expenses
Other income and expenses, net	4	3	12	6
Interest Expense	22	22	67	63
Income (Loss) From Continuing Operations Before Income Taxes	84	87	195	200
Income Tax Expense (Benefit) from Continuing Operations	28	32	67	65
Income from Continuing Operations	56	55	128	135
(Loss) Income From Discontinued Operations, net of tax	(1)	34	(1)	36
Net Income (Loss) Attributable to Parent	55	89	127	171
Other Comprehensive Income (Loss), net of tax
Comprehensive Income (Loss) Attributable to Parent	55	89	127	171
Duke Energy Indiana [Member]
Operating Revenues
Total operating revenues	802	809	2,302	2,225
Operating Expenses
Fuel used in electric generation and purchased power	259	242	744	690
Operation, maintenance and other	175	175	541	526
Depreciation and amortization	120	123	336	345
Property and other taxes	19	22	56	67
Impairment charges		8		8
Total operating expenses	573	570	1,677	1,636
Gains (Losses) on Sales of Other Assets and Other, net	1		1
Operating Income (Loss)	230	239	626	589
Other Income and Expenses
Other income and expenses, net	10	5	27	15
Interest Expense	44	45	132	136
Income (Loss) From Continuing Operations Before Income Taxes	196	199	521	468
Income Tax Expense (Benefit) from Continuing Operations	75	70	203	159
Net Income (Loss) Attributable to Parent	121	129	318	309
Other Comprehensive Income (Loss), net of tax
Reclassification into earnings from cash flow hedges				(1)
Other Comprehensive Income, net of tax				(1)
Comprehensive Income (Loss) Attributable to Parent	121	129	318	308
Piedmont Natural Gas [Member]
Operating Revenues
Regulated natural gas	181	155	877	815
Nonregulated electric and other	2	3	7	8
Total operating revenues	183	158	884	823
Operating Expenses
Cost of natural gas	63	42	333	289
Operation, maintenance and other	73	74	226	221
Depreciation and amortization	38	35	109	103
Property and other taxes	13	11	38	33
Impairment charges			7
Total operating expenses	187	162	713	646
Operating Income (Loss)	(4)	(4)	171	177
Other Income and Expenses
Equity in earnings (losses) of unconsolidated affiliates	3	2	8	25
Other income and expenses, net		(1)	(1)	(1)
Total other income and expenses	3	1	7	24
Interest Expense	20	17	59	50
Income (Loss) From Continuing Operations Before Income Taxes	(21)	(20)	119	151
Income Tax Expense (Benefit) from Continuing Operations	(10)	(8)	43	57
Net Income (Loss) Attributable to Parent	(11)	(12)	76	94
Other Comprehensive Income (Loss), net of tax
Reclassification into earnings from cash flow hedges		1		1
Other Comprehensive Income, net of tax				1
Comprehensive Income (Loss) Attributable to Parent	$ (11)	$ (11)	$ 76	$ 95

Condensed Consolidated Stateme3

Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest [Abstract]
Net income	$ 955	$ 1,181	$ 2,361	$ 2,392
Other Comprehensive Income, net of tax
Foreign currency translation adjustments	0	(12)	0	95
Pension and OPEB adjustments	0	0	2	2
Net unrealized gains (losses) on cash flow hedges	2	6	(2)	(19)
Reclassification into earnings from cash flow hedges	(2)	1	3	3
Unrealized gains on available-for-sale securities	2	0	10	7
Other Comprehensive Income (Loss), net of tax	2	(5)	13	88
Comprehensive Income	957	1,176	2,374	2,480
Less: Comprehensive Income Attributable to Noncontrolling Interests	1	4	5	16
Comprehensive Income (Loss) Attributable to Parent	$ 956	$ 1,172	$ 2,369	$ 2,464

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Current Assets
Cash and cash equivalents	$ 282	$ 392
Receivables (net of allowance for doubtful accounts)	528	751
Receivables of VIEs (net of allowance for doubtful accounts)	2,089	1,893
Inventory	3,265	3,522
Regulatory assets	1,109	1,023
Other	433	458
Total current assets	7,706	8,039
Property, Plant and Equipment
Cost	125,582	121,397
Accumulated depreciation and amortization	(41,161)	(39,406)
Generation facilities to be retired, net	441	529
Net property, plant and equipment	84,862	82,520
Other Noncurrent Assets
Goodwill	19,418	19,425
Regulatory assets	13,367	12,878
Nuclear decommissioning trust funds	6,814	6,205
Investments in equity method unconsolidated affiliates	1,366	925
Other	2,792	2,769
Total other noncurrent assets	43,757	42,202
Total Assets	136,325	132,761
Current Liabilities
Accounts payable	2,645	2,994
Notes payable and commercial paper	1,899	2,487
Taxes accrued	627	384
Interest accrued	538	503
Current maturities of long-term debt	2,485	2,319
Asset retirement obligations	619	411
Regulatory liabilities	273	409
Other	1,734	2,044
Total current liabilities	10,820	11,551
Long-Term Debt	48,929	45,576
Other Noncurrent Liabilities
Deferred income taxes	15,058	14,155
Asset retirement obligations	9,586	10,200
Regulatory liabilities	7,027	6,881
Accrued pension and other post-retirement benefit costs	1,105	1,111
Investment tax credits	534	493
Other	1,624	1,753
Total other noncurrent liabilities	34,934	34,593
Commitments and Contingencies
Equity
Common stock	1	1
Additional paid-in capital	38,774	38,741
Retained earnings	2,936	2,384
Accumulated other comprehensive loss	(80)	(93)
Total Parent stockholders' equity	41,631	41,033
Noncontrolling interests	11	8
Total equity	41,642	41,041
Total Liabilities and Equity	136,325	132,761
Duke Energy Carolinas [Member]
Current Assets
Cash and cash equivalents	18	14
Receivables (net of allowance for doubtful accounts)	180	160
Receivables of VIEs (net of allowance for doubtful accounts)	691	645
Receivables from affiliated companies	146	163
Notes receivable from affiliated companies		66
Inventory	1,000	1,055
Regulatory assets	237	238
Other	27	37
Total current assets	2,299	2,378
Property, Plant and Equipment
Cost	42,321	41,127
Accumulated depreciation and amortization	(14,969)	(14,365)
Net property, plant and equipment	27,352	26,762
Other Noncurrent Assets
Regulatory assets	3,077	3,159
Nuclear decommissioning trust funds	3,621	3,273
Other	910	943
Total other noncurrent assets	7,608	7,375
Total Assets	37,259	36,515
Current Liabilities
Accounts payable	726	833
Accounts payable to affiliated companies	159	247
Notes payable to affiliated companies	468
Taxes accrued	368	143
Interest accrued	135	102
Current maturities of long-term debt	705	116
Asset retirement obligations	304	222
Regulatory liabilities	105	161
Other	435	468
Total current liabilities	3,405	2,292
Long-Term Debt	8,520	9,187
Long-Term Debt Payable to Affiliated Companies	300	300
Other Noncurrent Liabilities
Deferred income taxes	6,796	6,544
Asset retirement obligations	3,297	3,673
Regulatory liabilities	2,884	2,840
Accrued pension and other post-retirement benefit costs	108	97
Investment tax credits	234	203
Other	559	607
Total other noncurrent liabilities	13,878	13,964
Commitments and Contingencies
Equity
Member's equity	11,164	10,781
Accumulated other comprehensive loss	(8)	(9)
Total member's equity	11,156	10,772
Total Liabilities and Equity	37,259	36,515
Progress Energy [Member]
Current Assets
Cash and cash equivalents	30	46
Receivables (net of allowance for doubtful accounts)	93	114
Receivables of VIEs (net of allowance for doubtful accounts)	900	692
Receivables from affiliated companies		106
Notes receivable from affiliated companies	170	80
Inventory	1,584	1,717
Regulatory assets	440	401
Other	243	148
Total current assets	3,460	3,304
Property, Plant and Equipment
Cost	46,659	44,864
Accumulated depreciation and amortization	(15,760)	(15,212)
Generation facilities to be retired, net	441	529
Net property, plant and equipment	31,340	30,181
Other Noncurrent Assets
Goodwill	3,655	3,655
Regulatory assets	6,438	5,722
Nuclear decommissioning trust funds	3,194	2,932
Other	909	856
Total other noncurrent assets	14,196	13,165
Total Assets	48,996	46,650
Current Liabilities
Accounts payable	1,015	1,003
Accounts payable to affiliated companies	289	348
Notes payable to affiliated companies	576	729
Taxes accrued	227	83
Interest accrued	216	201
Current maturities of long-term debt	770	778
Asset retirement obligations	250	189
Regulatory liabilities	121	189
Other	652	745
Total current liabilities	4,116	4,265
Long-Term Debt	16,717	15,590
Long-Term Debt Payable to Affiliated Companies	150	1,173
Other Noncurrent Liabilities
Deferred income taxes	6,463	5,246
Asset retirement obligations	5,189	5,286
Regulatory liabilities	2,511	2,395
Accrued pension and other post-retirement benefit costs	535	547
Other	298	341
Total other noncurrent liabilities	14,996	13,815
Commitments and Contingencies
Equity
Additional paid-in capital	9,143	8,094
Retained earnings	3,906	3,764
Accumulated other comprehensive loss	(26)	(38)
Total Parent stockholders' equity	13,023	11,820
Noncontrolling interests	(6)	(13)
Total equity	13,017	11,807
Total Liabilities and Equity	48,996	46,650
Duke Energy Progress [Member]
Current Assets
Cash and cash equivalents	15	11
Receivables (net of allowance for doubtful accounts)	29	51
Receivables of VIEs (net of allowance for doubtful accounts)	472	404
Receivables from affiliated companies	8	5
Notes receivable from affiliated companies	101	165
Inventory	1,018	1,076
Regulatory assets	230	188
Other	40	57
Total current assets	1,913	1,957
Property, Plant and Equipment
Cost	29,104	28,419
Accumulated depreciation and amortization	(10,793)	(10,561)
Generation facilities to be retired, net	441	529
Net property, plant and equipment	18,752	18,387
Other Noncurrent Assets
Regulatory assets	3,588	3,243
Nuclear decommissioning trust funds	2,463	2,217
Other	565	525
Total other noncurrent assets	6,616	5,985
Total Assets	27,281	26,329
Current Liabilities
Accounts payable	271	589
Accounts payable to affiliated companies	207	227
Taxes accrued	137	104
Interest accrued	91	102
Current maturities of long-term debt	203	452
Asset retirement obligations	250	189
Regulatory liabilities	107	158
Other	318	365
Total current liabilities	1,584	2,186
Long-Term Debt	7,204	6,409
Long-Term Debt Payable to Affiliated Companies	150	150
Other Noncurrent Liabilities
Deferred income taxes	3,606	3,323
Asset retirement obligations	4,426	4,508
Regulatory liabilities	2,097	1,946
Accrued pension and other post-retirement benefit costs	246	252
Investment tax credits	144	146
Other	44	51
Total other noncurrent liabilities	10,563	10,226
Commitments and Contingencies
Equity
Total member's equity	7,780	7,358
Total Liabilities and Equity	27,281	26,329
Duke Energy Florida [Member]
Current Assets
Cash and cash equivalents	8	16
Receivables (net of allowance for doubtful accounts)	61	61
Receivables of VIEs (net of allowance for doubtful accounts)	428	288
Receivables from affiliated companies		5
Notes receivable from affiliated companies	70
Inventory	566	641
Regulatory assets	211	213
Other	154	125
Total current assets	1,498	1,349
Property, Plant and Equipment
Cost	17,546	16,434
Accumulated depreciation and amortization	(4,960)	(4,644)
Net property, plant and equipment	12,586	11,790
Other Noncurrent Assets
Regulatory assets	2,850	2,480
Nuclear decommissioning trust funds	731	715
Other	293	278
Total other noncurrent assets	3,874	3,473
Total Assets	17,958	16,612
Current Liabilities
Accounts payable	744	413
Accounts payable to affiliated companies	90	125
Notes payable to affiliated companies		297
Taxes accrued	143	33
Interest accrued	71	49
Current maturities of long-term debt	567	326
Regulatory liabilities	14	31
Other	310	352
Total current liabilities	1,939	1,626
Long-Term Debt	6,129	5,799
Other Noncurrent Liabilities
Deferred income taxes	3,076	2,694
Asset retirement obligations	763	778
Regulatory liabilities	414	448
Accrued pension and other post-retirement benefit costs	257	262
Other	106	105
Total other noncurrent liabilities	4,616	4,287
Commitments and Contingencies
Equity
Member's equity	5,270	4,899
Accumulated other comprehensive loss	4	1
Total member's equity	5,274	4,900
Total Liabilities and Equity	17,958	16,612
Duke Energy Ohio [Member]
Current Assets
Cash and cash equivalents	7	13
Receivables (net of allowance for doubtful accounts)	68	71
Receivables from affiliated companies	81	129
Notes receivable from affiliated companies	87	94
Inventory	139	137
Regulatory assets	57	37
Other	18	37
Total current assets	457	518
Property, Plant and Equipment
Cost	8,509	8,126
Accumulated depreciation and amortization	(2,658)	(2,579)
Net property, plant and equipment	5,851	5,547
Other Noncurrent Assets
Goodwill	920	920
Regulatory assets	510	520
Other	27	23
Total other noncurrent assets	1,457	1,463
Total Assets	7,765	7,528
Current Liabilities
Accounts payable	251	282
Accounts payable to affiliated companies	59	63
Notes payable to affiliated companies		16
Taxes accrued	157	178
Interest accrued	33	19
Current maturities of long-term debt		1
Asset retirement obligations	6
Regulatory liabilities	15	21
Other	74	91
Total current liabilities	595	671
Long-Term Debt	2,042	1,858
Long-Term Debt Payable to Affiliated Companies	25	25
Other Noncurrent Liabilities
Deferred income taxes	1,512	1,443
Asset retirement obligations	75	77
Regulatory liabilities	232	236
Accrued pension and other post-retirement benefit costs	52	56
Other	134	166
Total other noncurrent liabilities	2,005	1,978
Commitments and Contingencies
Equity
Common stock	762	762
Additional paid-in capital	2,670	2,695
Retained earnings	(334)	(461)
Total Parent stockholders' equity	3,098	2,996
Total Liabilities and Equity	7,765	7,528
Duke Energy Indiana [Member]
Current Assets
Cash and cash equivalents	22	17
Receivables (net of allowance for doubtful accounts)	74	105
Receivables from affiliated companies	83	114
Notes receivable from affiliated companies	29	86
Inventory	450	504
Regulatory assets	158	149
Other	34	45
Total current assets	850	1,020
Property, Plant and Equipment
Cost	14,716	14,241
Accumulated depreciation and amortization	(4,592)	(4,317)
Net property, plant and equipment	10,124	9,924
Other Noncurrent Assets
Regulatory assets	1,123	1,073
Other	170	147
Total other noncurrent assets	1,293	1,220
Total Assets	12,267	12,164
Current Liabilities
Accounts payable	188	263
Accounts payable to affiliated companies	73	74
Taxes accrued	146	31
Interest accrued	54	61
Current maturities of long-term debt	3	3
Asset retirement obligations	58
Regulatory liabilities	28	40
Other	111	93
Total current liabilities	661	565
Long-Term Debt	3,632	3,633
Long-Term Debt Payable to Affiliated Companies	150	150
Other Noncurrent Liabilities
Deferred income taxes	1,979	1,900
Asset retirement obligations	735	866
Regulatory liabilities	735	748
Accrued pension and other post-retirement benefit costs	78	71
Investment tax credits	147	137
Other	65	27
Total other noncurrent liabilities	3,739	3,749
Commitments and Contingencies
Equity
Total member's equity	4,085	4,067
Total Liabilities and Equity	12,267	12,164
Piedmont Natural Gas [Member]
Current Assets
Cash and cash equivalents	12	25
Receivables (net of allowance for doubtful accounts)	77	232
Receivables from affiliated companies	8	7
Inventory	53	66
Regulatory assets	133	124
Income taxes receivable	99	9
Other	31	12
Total current assets	413	475
Property, Plant and Equipment
Cost	6,579	6,174
Accumulated depreciation and amortization	(1,454)	(1,360)
Net property, plant and equipment	5,125	4,814
Other Noncurrent Assets
Goodwill	49	49
Regulatory assets	322	373
Investments in equity method unconsolidated affiliates	76	212
Other	11	21
Total other noncurrent assets	458	655
Total Assets	5,996	5,944
Current Liabilities
Accounts payable	98	155
Accounts payable to affiliated companies	7	8
Notes payable and commercial paper		330
Notes payable to affiliated companies	284
Taxes accrued	30	67
Interest accrued	24	33
Current maturities of long-term debt		35
Regulatory liabilities	3
Other	72	102
Total current liabilities	518	730
Long-Term Debt	2,036	1,786
Other Noncurrent Liabilities
Deferred income taxes	1,046	931
Asset retirement obligations	15	14
Regulatory liabilities	627	608
Accrued pension and other post-retirement benefit costs	14	14
Other	141	189
Total other noncurrent liabilities	1,843	1,756
Commitments and Contingencies
Equity
Common stock	860	860
Retained earnings	739	812
Total Parent stockholders' equity	1,599	1,672
Total Liabilities and Equity	$ 5,996	$ 5,944

Condensed Consolidated Balance5

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Allowance for doubtful accounts - receivables	$ 13	$ 14
Regulatory assets, current	1,109	1,023
Other, current assets	433	458
Regulatory assets, noncurrent	13,367	12,878
Current maturities of long-term debt	2,485	2,319
Long-Term Debt	$ 48,929	$ 45,576
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	2,000,000,000	2,000,000,000
Common stock, shares outstanding	700,000,000	700,000,000
Variable Interest Entity [Member]
Allowance for doubtful accounts - receivables of VIEs	$ 54	$ 54
Regulatory assets, current	51	50
Regulatory assets, noncurrent	1,101	1,142
Current maturities of long-term debt	215	260
Long-Term Debt	4,219	3,587
Duke Energy Carolinas [Member]
Allowance for doubtful accounts - receivables	2	2
Regulatory assets, current	237	238
Other, current assets	27	37
Regulatory assets, noncurrent	3,077	3,159
Current maturities of long-term debt	705	116
Long-Term Debt	8,520	9,187
Duke Energy Carolinas [Member] | Variable Interest Entity [Member]
Allowance for doubtful accounts - receivables of VIEs	7	7
Progress Energy [Member]
Allowance for doubtful accounts - receivables	4	6
Regulatory assets, current	440	401
Other, current assets	243	148
Regulatory assets, noncurrent	6,438	5,722
Current maturities of long-term debt	770	778
Long-Term Debt	$ 16,717	$ 15,590
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	100	100
Common stock, shares outstanding	100	100
Progress Energy [Member] | Variable Interest Entity [Member]
Allowance for doubtful accounts - receivables of VIEs	$ 7	$ 7
Regulatory assets, current	51	50
Regulatory assets, noncurrent	1,101	1,142
Current maturities of long-term debt	53	62
Long-Term Debt	1,689	1,741
Duke Energy Progress [Member]
Allowance for doubtful accounts - receivables	1	4
Regulatory assets, current	230	188
Other, current assets	40	57
Regulatory assets, noncurrent	3,588	3,243
Current maturities of long-term debt	203	452
Long-Term Debt	7,204	6,409
Duke Energy Progress [Member] | Variable Interest Entity [Member]
Allowance for doubtful accounts - receivables of VIEs	5	5
Duke Energy Florida [Member]
Allowance for doubtful accounts - receivables	3	2
Regulatory assets, current	211	213
Other, current assets	154	125
Regulatory assets, noncurrent	2,850	2,480
Current maturities of long-term debt	567	326
Long-Term Debt	6,129	5,799
Duke Energy Florida [Member] | Variable Interest Entity [Member]
Allowance for doubtful accounts - receivables of VIEs	2	2
Regulatory assets, current	51	50
Other, current assets	20	53
Regulatory assets, noncurrent	1,101	1,142
Current maturities of long-term debt	53	62
Long-Term Debt	1,389	1,442
Duke Energy Ohio [Member]
Allowance for doubtful accounts - receivables	2	2
Regulatory assets, current	57	37
Other, current assets	18	37
Regulatory assets, noncurrent	510	520
Current maturities of long-term debt		1
Long-Term Debt	$ 2,042	$ 1,858
Common stock, par value	$ 8.50	$ 8.50
Common stock, shares authorized	120,000,000	120,000,000
Common stock, shares outstanding	90,000,000	90,000,000
Duke Energy Indiana [Member]
Allowance for doubtful accounts - receivables	$ 1	$ 1
Regulatory assets, current	158	149
Other, current assets	34	45
Regulatory assets, noncurrent	1,123	1,073
Current maturities of long-term debt	3	3
Long-Term Debt	3,632	3,633
Piedmont Natural Gas [Member]
Allowance for doubtful accounts - receivables	2	3
Regulatory assets, current	133	124
Other, current assets	31	12
Regulatory assets, noncurrent	322	373
Current maturities of long-term debt		35
Long-Term Debt	$ 2,036	$ 1,786
Common stock, shares authorized	100	100
Common stock, shares outstanding	100	100

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 2,361	$ 2,392
Net income (attributable to parent)	2,356	2,379
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and accretion (including amortization of nuclear fuel)	2,990	2,847
Equity component of AFUDC	(175)	(140)
Gains on sales of other assets	(28)	(27)
Impairment charges	216	279
Deferred income taxes	1,016	648
Equity in earnings of unconsolidated affiliates	(101)	(34)
Accrued pension and other post-retirement benefit costs	19	12
Contributions to qualified pension plans	(8)
Payments for asset retirement obligations	(420)	(443)
(Increase) decrease in
Net realized and unrealized mark-to-market and hedging transactions	4	36
Receivables	80	(276)
Inventory	248	455
Other current assets	(176)	(163)
Increase (decrease) in
Accounts payable	(554)	(207)
Taxes accrued	233	417
Other current liabilities	(532)	(157)
Other assets	(160)	(64)
Other liabilities	(2)	36
Net cash provided by operating activities	5,011	5,611
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(5,841)	(5,252)
Contributions to equity method investments	(370)	(198)
Purchases of available-for-sale securities	(3,170)	(4,048)
Proceeds from sales and maturities of available-for-sale securities	3,199	4,107
Change in restricted cash	(29)	(34)
Other	(149)	(130)
Net cash used in investing activities	(6,360)	(5,555)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from the issuance of long-term debt	5,710	8,647
Proceeds from the issuance of common stock related to employee benefit plans		7
Payments for the redemption of long-term debt	(2,035)	(988)
Proceeds from issuance of short-term debt with original maturities greater than 90 days	265	1,424
Payments for the redemption of short-term debt with original maturities greater than 90 days	(237)	(492)
Notes payable and commercial paper	(647)	(1,579)
Dividends paid	(1,825)	(1,731)
Other	8	(22)
Net cash provided by financing activities	1,239	5,266
Changes in cash and cash equivalents associated with assets held for sale		11
Net decrease in cash and cash equivalents	(110)	5,333
Cash and cash equivalents at beginning of period	392	383
Cash and cash equivalents at end of period	282	5,716
Significant non-cash transactions:
Accrued capital expenditures	740	631
Duke Energy Carolinas [Member]
CASH FLOWS FROM OPERATING ACTIVITIES
Net income (attributable to parent)	1,009	1,026
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and accretion (including amortization of nuclear fuel)	1,051	1,020
Equity component of AFUDC	(79)	(75)
Gains on sales of other assets		1
Deferred income taxes	330	382
Accrued pension and other post-retirement benefit costs		3
Payments for asset retirement obligations	(201)	(204)
(Increase) decrease in
Net realized and unrealized mark-to-market and hedging transactions	1	4
Receivables	(40)	(191)
Receivable from affiliated companies	17	19
Inventory	50	217
Other current assets	8	81
Increase (decrease) in
Accounts payable	(78)	(179)
Accounts payable to affiliated companies	(88)	(100)
Taxes accrued	225	248
Other current liabilities	(149)	51
Other assets	(18)	57
Other liabilities	(26)	(15)
Net cash provided by operating activities	2,012	2,345
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(1,747)	(1,531)
Purchases of available-for-sale securities	(1,660)	(2,070)
Proceeds from sales and maturities of available-for-sale securities	1,664	2,070
Notes receivable from affiliated companies	66	131
Other	(58)	(65)
Net cash used in investing activities	(1,735)	(1,465)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from the issuance of long-term debt		992
Payments for the redemption of long-term debt	(115)	(3)
Notes payable to affiliated companies	468
Distributions to parent	(625)	(1,800)
Other	(1)
Net cash provided by financing activities	(273)	(811)
Net decrease in cash and cash equivalents	4	69
Cash and cash equivalents at beginning of period	14	13
Cash and cash equivalents at end of period	18	82
Significant non-cash transactions:
Accrued capital expenditures	292	228
Progress Energy [Member]
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	821	935
Net income (attributable to parent)	814	927
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and accretion (including amortization of nuclear fuel)	1,130	1,071
Equity component of AFUDC	(68)	(51)
Gains on sales of other assets	(20)	(23)
Impairment charges	137	4
Deferred income taxes	651	425
Accrued pension and other post-retirement benefit costs	(9)	(19)
Payments for asset retirement obligations	(190)	(203)
(Increase) decrease in
Net realized and unrealized mark-to-market and hedging transactions	1	33
Receivables	(182)	(155)
Receivable from affiliated companies	102	329
Inventory	126	99
Other current assets	(279)	(30)
Increase (decrease) in
Accounts payable	(281)	(24)
Accounts payable to affiliated companies	(59)	(109)
Taxes accrued	143	159
Other current liabilities	(184)	(156)
Other assets	(100)	(90)
Other liabilities	(85)	(4)
Net cash provided by operating activities	1,654	2,191
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(2,419)	(2,286)
Purchases of available-for-sale securities	(1,393)	(1,849)
Proceeds from sales and maturities of available-for-sale securities	1,411	1,899
Proceeds from Insurance	4	58
Notes receivable from affiliated companies	(90)	(43)
Change in restricted cash	5	(6)
Other	(40)	(17)
Net cash used in investing activities	(2,522)	(2,244)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from the issuance of long-term debt	1,720	2,375
Payments for the redemption of long-term debt	(611)	(327)
Notes payable to affiliated companies	(129)	(798)
Dividends to parent	(125)	(1,075)
Other	(3)	(1)
Net cash provided by financing activities	852	174
Net decrease in cash and cash equivalents	(16)	121
Cash and cash equivalents at beginning of period	46	44
Cash and cash equivalents at end of period	30	165
Significant non-cash transactions:
Accrued capital expenditures	174	228
Equitization of certain notes payable to affiliates	1,047
Dividend to parent related to a legal restructuring	547
Duke Energy Progress [Member]
CASH FLOWS FROM OPERATING ACTIVITIES
Net income (attributable to parent)	547	539
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and accretion (including amortization of nuclear fuel)	691	679
Equity component of AFUDC	(35)	(34)
Gains on sales of other assets	(4)	(4)
Impairment charges		1
Deferred income taxes	287	325
Accrued pension and other post-retirement benefit costs	(15)	(24)
Payments for asset retirement obligations	(149)	(163)
(Increase) decrease in
Net realized and unrealized mark-to-market and hedging transactions	(2)
Receivables	(47)	(78)
Receivable from affiliated companies	(3)	11
Inventory	52	91
Other current assets	(34)	37
Increase (decrease) in
Accounts payable	(286)	(44)
Accounts payable to affiliated companies	(20)	(47)
Taxes accrued	33	76
Other current liabilities	(139)	37
Other assets	(49)	(32)
Other liabilities	(9)	(10)
Net cash provided by operating activities	818	1,360
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(1,247)	(1,106)
Purchases of available-for-sale securities	(995)	(1,470)
Proceeds from sales and maturities of available-for-sale securities	974	1,448
Notes receivable from affiliated companies	64	(65)
Other	(26)	(27)
Net cash used in investing activities	(1,230)	(1,220)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from the issuance of long-term debt	812	505
Payments for the redemption of long-term debt	(270)	(15)
Notes payable to affiliated companies		(209)
Dividends to parent	(125)	(301)
Other	(1)	1
Net cash provided by financing activities	416	(19)
Net decrease in cash and cash equivalents	4	121
Cash and cash equivalents at beginning of period	11	15
Cash and cash equivalents at end of period	15	136
Significant non-cash transactions:
Accrued capital expenditures	116	66
Duke Energy Florida [Member]
CASH FLOWS FROM OPERATING ACTIVITIES
Net income (attributable to parent)	368	487
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and accretion (including amortization of nuclear fuel)	431	383
Equity component of AFUDC	(33)	(16)
Impairment charges	137	4
Deferred income taxes	366	136
Accrued pension and other post-retirement benefit costs	3	2
Payments for asset retirement obligations	(41)	(41)
(Increase) decrease in
Net realized and unrealized mark-to-market and hedging transactions	3	34
Receivables	(140)	(78)
Receivable from affiliated companies	1	41
Inventory	74	8
Other current assets	(162)	(32)
Increase (decrease) in
Accounts payable	6	20
Accounts payable to affiliated companies	(35)	(55)
Taxes accrued	109	61
Other current liabilities	(45)	(183)
Other assets	(35)	(56)
Other liabilities	(71)	1
Net cash provided by operating activities	936	716
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(1,172)	(1,179)
Purchases of available-for-sale securities	(398)	(379)
Proceeds from sales and maturities of available-for-sale securities	437	450
Proceeds from Insurance	4	58
Notes receivable from affiliated companies	(70)
Change in restricted cash		(6)
Other	(14)	10
Net cash used in investing activities	(1,213)	(1,046)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from the issuance of long-term debt	908	1,870
Payments for the redemption of long-term debt	(341)	(12)
Notes payable to affiliated companies	(297)	(750)
Distributions to parent		(774)
Other	(1)	(2)
Net cash provided by financing activities	269	332
Net decrease in cash and cash equivalents	(8)	2
Cash and cash equivalents at beginning of period	16	8
Cash and cash equivalents at end of period	8	10
Significant non-cash transactions:
Accrued capital expenditures	102	162
Duke Energy Ohio [Member]
CASH FLOWS FROM OPERATING ACTIVITIES
Net income (attributable to parent)	127	171
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and accretion (including amortization of nuclear fuel)	196	178
Equity component of AFUDC	(8)	(4)
Gains on sales of other assets	(1)	(2)
Impairment charges	1
Deferred income taxes	70	36
Accrued pension and other post-retirement benefit costs	3	4
Contributions to qualified pension plans	(4)
Payments for asset retirement obligations	(4)	(4)
(Increase) decrease in
Net realized and unrealized mark-to-market and hedging transactions	1
Receivables	3	(1)
Receivable from affiliated companies	48	(3)
Inventory	1	(5)
Other current assets	(8)	50
Increase (decrease) in
Accounts payable	(48)	13
Accounts payable to affiliated companies	(4)	(4)
Taxes accrued	(21)	(13)
Other current liabilities	(6)	(53)
Other assets	(13)	(8)
Other liabilities	(2)	(28)
Net cash provided by operating activities	331	327
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(457)	(334)
Notes receivable from affiliated companies	7	(47)
Other	(25)	(21)
Net cash used in investing activities	(475)	(402)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from the issuance of long-term debt	182	341
Payments for the redemption of long-term debt	(2)	(53)
Notes payable to affiliated companies	(16)	(103)
Dividends to parent	(25)	(25)
Other	(1)
Net cash provided by financing activities	138	160
Net decrease in cash and cash equivalents	(6)	85
Cash and cash equivalents at beginning of period	13	14
Cash and cash equivalents at end of period	7	99
Significant non-cash transactions:
Accrued capital expenditures	65	56
Duke Energy Indiana [Member]
CASH FLOWS FROM OPERATING ACTIVITIES
Net income (attributable to parent)	318	309
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and accretion (including amortization of nuclear fuel)	339	347
Equity component of AFUDC	(20)	(11)
Gains on sales of other assets	(1)
Impairment charges		8
Deferred income taxes	101	122
Accrued pension and other post-retirement benefit costs	4	6
Payments for asset retirement obligations	(26)	(31)
(Increase) decrease in
Receivables	53	16
Receivable from affiliated companies	31	(3)
Inventory	54	146
Other current assets	18	(105)
Increase (decrease) in
Accounts payable	(71)	(14)
Accounts payable to affiliated companies	(1)	(1)
Taxes accrued	115	12
Other current liabilities	(18)	(85)
Other assets	(24)	(38)
Other liabilities	32	64
Net cash provided by operating activities	904	742
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(603)	(540)
Purchases of available-for-sale securities	(15)	(12)
Proceeds from sales and maturities of available-for-sale securities	6	9
Notes receivable from affiliated companies	57	45
Other	(40)	(28)
Net cash used in investing activities	(595)	(526)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from the issuance of long-term debt		495
Payments for the redemption of long-term debt	(3)	(476)
Distributions to parent	(300)	(149)
Other	(1)	(1)
Net cash provided by financing activities	(304)	(131)
Net decrease in cash and cash equivalents	5	85
Cash and cash equivalents at beginning of period	17	9
Cash and cash equivalents at end of period	22	94
Significant non-cash transactions:
Accrued capital expenditures	101	56
Piedmont Natural Gas [Member]
CASH FLOWS FROM OPERATING ACTIVITIES
Net income (attributable to parent)	76	94
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and accretion (including amortization of nuclear fuel)	112	111
Impairment charges	7
Deferred income taxes	127	50
Equity in earnings of unconsolidated affiliates	(8)	(25)
Accrued pension and other post-retirement benefit costs	9	2
Contributions to qualified pension plans		(1)
Payments for asset retirement obligations		(5)
(Increase) decrease in
Receivables	157	88
Receivable from affiliated companies	(1)
Inventory	13	33
Other current assets	(129)	(50)
Increase (decrease) in
Accounts payable	(52)	11
Accounts payable to affiliated companies	(1)
Taxes accrued	(37)	12
Other current liabilities	(21)	(11)
Other assets	(9)	55
Other liabilities	(7)	17
Net cash provided by operating activities	236	381
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(407)	(416)
Contributions to equity method investments	(12)	(40)
Other	2	(2)
Net cash used in investing activities	(417)	(458)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from the issuance of long-term debt	250	296
Proceeds from the issuance of common stock related to employee benefit plans		121
Payments for the redemption of long-term debt	(35)	(40)
Notes payable and commercial paper	(330)	(210)
Notes payable to affiliated companies	284
Dividends paid		(82)
Other	(1)
Net cash provided by financing activities	168	85
Net decrease in cash and cash equivalents	(13)	8
Cash and cash equivalents at beginning of period	25	33
Cash and cash equivalents at end of period	12	41
Significant non-cash transactions:
Accrued capital expenditures	47	$ 30
Transfer of Ownership Interest in Investments [Member] | Piedmont Natural Gas [Member]
Significant non-cash transactions:
Transfer of ownership interest of certain equity method investees to parent	$ 149

Condensed Consolidated Stateme7

Condensed Consolidated Statements of Changes in Equity - USD ($) $ in Millions	Total		Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]		Foreign Currency Translation Adjustments [Member]	Net Gains (Losses) on Cash Flow Hedges [Member]	Net Unrealized Gains (Losses) on Available for Sale Securities [Member]	Pension and OPEB Adjustments [Member]	Common Stockholders' Equity [Member]		Noncontrolling Interest [Member]	Duke Energy Carolinas [Member]	Duke Energy Carolinas [Member]Members Equity [Member]	Duke Energy Carolinas [Member]Net Gains (Losses) on Cash Flow Hedges [Member]	Progress Energy [Member]		Progress Energy [Member]Additional Paid-in Capital [Member]	Progress Energy [Member]Retained Earnings [Member]		Progress Energy [Member]Net Gains (Losses) on Cash Flow Hedges [Member]	Progress Energy [Member]Net Unrealized Gains (Losses) on Available for Sale Securities [Member]	Progress Energy [Member]Pension and OPEB Adjustments [Member]	Progress Energy [Member]Common Stockholders' Equity [Member]		Progress Energy [Member]Noncontrolling Interest [Member]	Duke Energy Progress [Member]	Duke Energy Florida [Member]	Duke Energy Florida [Member]Members Equity [Member]	Duke Energy Florida [Member]Net Unrealized Gains (Losses) on Available for Sale Securities [Member]	Duke Energy Ohio [Member]	Duke Energy Ohio [Member]Common Stock [Member]	Duke Energy Ohio [Member]Additional Paid-in Capital [Member]	Duke Energy Ohio [Member]Retained Earnings [Member]	Duke Energy Indiana [Member]	Duke Energy Indiana [Member]Common Stock [Member]	Duke Energy Indiana [Member]Additional Paid-in Capital [Member]	Duke Energy Indiana [Member]Retained Earnings [Member]	Duke Energy Indiana [Member]Members Equity [Member]	Duke Energy Indiana [Member]Net Gains (Losses) on Cash Flow Hedges [Member]	Piedmont Natural Gas [Member]	Piedmont Natural Gas [Member]Common Stock [Member]	Piedmont Natural Gas [Member]Retained Earnings [Member]	Piedmont Natural Gas [Member]Net Gains (Losses) on Cash Flow Hedges [Member]
Beginning Balance at Dec. 31, 2015	$ 39,771		$ 1	$ 37,968	$ 2,564		$ (692)	$ (50)	$ (3)	$ (61)	$ 39,727		$ 44				$ 12,853		$ 8,092	$ 4,831		$ (31)		$ (17)	$ 12,875		$ (22)
Beginning Balance, in shares at Dec. 31, 2015			688,000,000
Beginning Balance (member's equity) at Dec. 31, 2015														$ 11,606	$ 11,617	$ (11)												$ 7,059	$ 5,121	$ 5,121
Beginning Balance (parent) at Dec. 31, 2015																																$ 2,784	$ 762	$ 2,720	$ (698)	$ 3,836	$ 1	$ 1,384	$ 2,450		$ 1	$ 1,458	$ 728	$ 731	$ (1)
Net income	2,392				2,379						2,379		13				935			927					927		8
Net income (attributable to parent)	2,379													1,026	1,026		927											539	487	487		171			171	309				$ 309		94		94
Other comprehensive income (loss)	88						92	(16)	7	2	85		3	1		1	8					4	$ 2	2	8				2		$ 2					(1)					$ (1)	1			1
Common stock issuances, including dividend reinvestment and employee benefits, shares			1,000,000
Common stock issuances, including dividend reinvestment and employee benefits	29			29							29																															121	121
Common stock dividends	(1,731)				(1,731)						(1,731)																															(87)		(87)
Distributions to noncontrolling interest in subsidiaries	(3)												(3)				(1)										(1)
Distributions/dividends to parent														(1,800)	(1,800)		(1,075)			(1,075)					(1,075)			(301)	(774)	(774)		(25)		(25)		(149)				(149)
Other														(3)	(3)		3		4						4		(1)		3	3		9			9		$ (1)	$ (1,384)	$ (2,450)	3,835
Ending Balance at Sep. 30, 2016	40,546		$ 1	37,997	3,212		$ (600)	(66)	4	(59)	40,489		57				12,723		8,096	4,683		(27)	2	(15)	12,739		(16)
Ending Balance, in shares at Sep. 30, 2016			689,000,000
Ending Balance (member's equity) at Sep. 30, 2016														10,830	10,840	(10)												7,297	4,839	4,837	2					3,995				3,995
Ending Balance (parent) at Sep. 30, 2016																																$ 2,939	762	2,695	(518)							$ 1,587	849	738	$ 0
Beginning Balance at Dec. 31, 2016	$ 41,041		$ 1	38,741	2,384			(20)	(1)	(72)	41,033		8				$ 11,807		8,094	3,764		(23)	1	(16)	11,820		(13)
Beginning Balance, in shares at Dec. 31, 2016	700,000,000		700,000,000														100															90,000,000										100
Beginning Balance (member's equity) at Dec. 31, 2016														10,772	10,781	(9)												7,358	4,900	4,899	1					4,067				4,067
Beginning Balance (parent) at Dec. 31, 2016	$ 41,033																$ 11,820															$ 2,996	762	2,695	(461)							$ 1,672	860	812
Net income	2,361				2,356						2,356		5				821			814					814		7
Net income (attributable to parent)	2,356													1,009	1,009		814											547	368	368		127			127	318				318		76		76
Other comprehensive income (loss)	13							1	10	2	13			1		1	12					4	3	5	12				3		3
Common stock issuances, including dividend reinvestment and employee benefits	33			33							33
Common stock dividends	(1,825)				(1,825)						(1,825)
Distributions to noncontrolling interest in subsidiaries	(2)												(2)
Distributions/dividends to parent														(625)	(625)		(672)	[1]		(672)	[1]				(672)	[1]		(125)				$ (25)		(25)		(300)				(300)
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		$ 1	$ 38,774	$ 2,936			$ (19)	$ 9	$ (70)	$ 41,631		$ 11				$ 13,017		$ 9,143	$ 3,906		$ (19)	$ 4	$ (11)	$ 13,023		$ (6)
Ending Balance, in shares at Sep. 30, 2017	700,000,000		700,000,000														100															90,000,000										100
Ending Balance (member's equity) at Sep. 30, 2017														$ 11,156	$ 11,164	$ (8)												$ 7,780	$ 5,274	$ 5,270	$ 4					$ 4,085				$ 4,085
Ending Balance (parent) at Sep. 30, 2017	$ 41,631																$ 13,023															$ 3,098	$ 762	$ 2,670	$ (334)							$ 1,599	$ 860	$ 739
[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. See Note 1 for more information.

Condensed Consolidated Stateme8

Condensed Consolidated Statements of Changes in Equity (Parenthetical) $ in Millions	9 Months Ended
	Sep. 30, 2017USD ($)
Progress Energy [Member]
Non-cash dividend	$ 547

Organization and Basis of Prese

Organization and Basis of Presentation	9 Months Ended
	Sep. 30, 2017
Accounting Policies [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, (ii) subsidiaries that are not registrants but included in the consolidated Duke Energy balances and (iii) the Piedmont registrant not included in the consolidated Duke Energy results for the three and nine months ended September 30, 2016, as Piedmont results were not consolidated by Duke Energy until after the acquisition date of October 3, 2016. 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. On October 3, 2016, Duke Energy completed the acquisition of Piedmont. Piedmont's results of operations and cash flows are included in the accompanying condensed consolidated financial statements of Duke Energy for the three and nine months ended September 30, 2017 , but not for the three and nine months ended September 30, 2016 , as Piedmont's earnings and cash flows are only included in Duke Energy's consolidated results subsequent to the acquisition date. See Note 2 for additional information regarding the acquisition. In December 2016, Duke Energy completed an exit of the Latin American market to focus on its domestic regulated business, which was further bolstered by the acquisition of Piedmont. The sale of the International Energy business segment, excluding an equity method investment in National Methanol Company (NMC), was completed through two transactions including a sale of assets in Brazil to China Three Gorges (Luxembourg) Energy S.à.r.l. (China Three Gorges) and a sale of Duke Energy's remaining Latin American assets in Peru, Chile, Ecuador, Guatemala, El Salvador and Argentina to ISQ Enerlam Aggregator, L.P. and Enerlam (UK) Holding Ltd. (I Squared Capital) (collectively, the International Disposal Group). See Note 2 for additional information on the sale of International Energy. The results of operations of the International Disposal Group have been classified as Discontinued Operations on the Condensed Consolidated Statements of Operations. Duke Energy has elected to present cash flows of discontinued operations combined with cash flows of continuing operations. Unless otherwise noted, the notes to these Condensed Consolidated Financial Statements exclude amounts related to discontinued operations. See Note 2 for additional information. 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 (formerly the Tennessee Regulatory Authority) (TPUC) and FERC. BASIS OF PRESENTATION These Condensed Consolidated Financial Statements have been prepared in accordance with generally accepted accounting principles (GAAP) in the U.S. 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 in the U.S. 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 for the year ended December 31, 2016 , and the Consolidated Financial Statements and Notes in the Piedmont Annual Report on Form 10‑K for the year ended October 31, 2016. Effective November 1, 2016, Piedmont's fiscal year-end was changed from October 31 to December 31, the year-end of Duke Energy. A transition report was filed on Form 10-Q (Form 10-QT) as of December 31, 2016, for the transition period from November 1, 2016, to December 31, 2016. 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. UNBILLED REVENUE Revenues on sales of electricity and natural gas are recognized when service is provided or the product is delivered. Unbilled revenues are recognized by applying customer billing rates to the estimated volumes of energy and 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, meter reading schedules, and the impact of weather normalization or margin decoupling mechanisms. Unbilled revenues are included within Receivables and Receivables of variable interest entities (VIEs) on the Condensed Consolidated Balance Sheets as shown in the following table. (in millions) September 30, 2017 December 31, 2016 Duke Energy $ 771 $ 831 Duke Energy Carolinas 307 313 Progress Energy 216 161 Duke Energy Progress 113 102 Duke Energy Florida 103 59 Duke Energy Ohio 2 2 Duke Energy Indiana 29 32 Piedmont 4 77 Additionally, Duke Energy Ohio and Duke Energy Indiana sell nearly all of their retail accounts receivable to an affiliate, Cinergy Receivables Company, LLC (CRC), on a revolving basis. These transfers of receivables are accounted for as sales and include receivables for unbilled revenues. Accordingly, the receivables sold are not reflected on the Condensed Consolidated Balance Sheets of Duke Energy Ohio and Duke Energy Indiana. See Note 13 for further information. These receivables for unbilled revenues are shown in the table below. (in millions) September 30, 2017 December 31, 2016 Duke Energy Ohio $ 70 $ 97 Duke Energy Indiana 119 123 AMOUNTS ATTRIBUTABLE TO CONTROLLING INTERESTS For the three and nine months ended September 30, 2017 , the Loss from Discontinued Operations, net of tax on Duke Energy's Condensed Consolidated Statements of Operations is entirely attributable to controlling interests. The following table presents Net Income Attributable to Duke Energy Corporation for continuing operations and discontinued operations for the three and nine months ended September 30, 2016 . Three Months Ended Nine Months Ended (in millions) September 30, 2016 September 30, 2016 Income from Continuing Operations $ 1,001 $ 2,202 Income from Continuing Operations Attributable to Noncontrolling Interests 2 5 Income from Continuing Operations Attributable to Duke Energy Corporation $ 999 $ 2,197 Income from Discontinued Operations, net of tax $ 180 $ 190 Income from Discontinued Operations Attributable to Noncontrolling Interests, net of tax 3 8 Income from Discontinued Operations Attributable to Duke Energy Corporation, net of tax $ 177 $ 182 Net Income $ 1,181 $ 2,392 Net Income Attributable to Noncontrolling Interests 5 13 Net Income Attributable to Duke Energy Corporation $ 1,176 $ 2,379 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, 2017 , and December 31, 2016 . The components of inventory are presented in the tables below. 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 Materials and supplies $ 2,335 $ 767 $ 1,132 $ 780 $ 351 $ 83 $ 312 $ 2 Coal 581 197 231 130 101 17 136 — Natural gas, oil and other fuel 349 36 221 108 114 39 2 51 Total inventory $ 3,265 $ 1,000 $ 1,584 $ 1,018 $ 566 $ 139 $ 450 $ 53 December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Materials and supplies $ 2,374 $ 767 $ 1,167 $ 813 $ 354 $ 84 $ 312 $ 1 Coal 774 251 314 148 166 19 190 — Natural gas, oil and other fuel 374 37 236 115 121 34 2 65 Total inventory $ 3,522 $ 1,055 $ 1,717 $ 1,076 $ 641 $ 137 $ 504 $ 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 as 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) 2017 2016 2017 2016 Duke Energy $ 107 $ 107 $ 289 $ 285 Duke Energy Carolinas 9 6 27 21 Progress Energy 67 65 168 161 Duke Energy Progress 5 4 14 13 Duke Energy Florida 62 61 154 148 Duke Energy Ohio 24 26 75 77 Duke Energy Indiana 6 10 16 26 Piedmont 1 1 3 2 NEW ACCOUNTING STANDARDS The new accounting standards adopted for 2017 and 2016 had no material impact on the presentation or results of operations, cash flows or financial position of the Duke Energy Registrants. 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, 2017 . Stock-Based Compensation and Income Taxes. In first quarter 2017, Duke Energy adopted Financial Accounting Standards Board (FASB) guidance, which revised the accounting for stock-based compensation and the associated income taxes. The adopted guidance changes certain aspects of accounting for stock-based payment awards to employees including the accounting for income taxes and classification on the Condensed Consolidated Statements of Cash Flows. The primary impact to Duke Energy as a result of implementing this guidance was a cumulative-effect adjustment to retained earnings for tax benefits not previously recognized and additional income tax expense for the nine months ended September 30, 2017 . See the Duke Energy Condensed Consolidated Statements of Changes in Equity for further information. Goodwill Impairment. In January 2017, the FASB issued revised guidance for the subsequent measurement of goodwill. Under the guidance, a company will recognize an impairment to goodwill for the amount by which a reporting unit's carrying value exceeds the reporting unit's fair value, not to exceed the amount of goodwill allocated to that reporting unit. Duke Energy early adopted this guidance for the 2017 annual goodwill impairment test. The following new Accounting Standards Updates (ASUs) have been issued, but have not yet been adopted by Duke Energy, as of September 30, 2017 . Retirement Benefits. In March 2017, the FASB issued revised accounting guidance for the presentation of net periodic costs related to benefit plans. Current GAAP permits the aggregation of all the components of net periodic costs on the income statement and does 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 must be included within Operating income within the same line as other compensation expenses. All other components of net periodic costs must be outside of Operating income. In addition, the updated guidance permits only the service cost component of net periodic costs to be capitalized to Inventory or Property, Plant and Equipment. This represents a change from current GAAP, which permits all components of net periodic costs to be capitalized. These amendments should be applied retrospectively for the presentation of the various components of net periodic costs and prospectively for the change in eligible costs to be capitalized. The guidance allows for a practical expedient that permits a company to use amounts disclosed in prior-period financial statements as the estimation basis for applying the retrospective presentation requirements. For Duke Energy, this guidance is effective for interim and annual periods beginning January 1, 2018. Duke Energy currently presents the total non-capitalized net periodic costs within Operation, maintenance and other on the Condensed Consolidated Statement of Operations. The adoption of this guidance will result in a retrospective change to reclassify the presentation of the non-service cost (benefit) components of net periodic costs to Other income and expenses. Duke Energy intends to utilize the practical expedient for retrospective presentation. The change in net periodic costs eligible for capitalization is applicable prospectively. Since Duke Energy’s service cost component is expected to be greater than the total net periodic costs, the change will result in increased capitalization of net periodic costs, higher Operation, maintenance and other and higher Other income and expenses. The resulting impact to Duke Energy is expected to be an immaterial increase in net income resulting from the limitation of eligible capitalization of net periodic costs to the service cost component, which is larger than the total net periodic costs. Revenue from Contracts with Customers . In May 2014, the FASB issued revised accounting guidance for revenue recognition from contracts with customers. The core principle of this guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The amendments in this update also require disclosure of sufficient information to allow users to understand the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. Duke Energy has identified material revenue streams, which served as the basis for accounting analysis and documentation of the impact of this guidance on revenue recognition. The accounting analysis included reviewing representative contracts and tariffs for each material revenue stream. Most of Duke Energy’s revenue is expected to be in scope of the new guidance. The majority of our sales, including energy provided to residential customers, are from tariff offerings that provide natural gas or electricity without a defined contractual term ("at-will"). For such arrangements, Duke Energy expects that the revenue from contracts with customers will be equivalent to the electricity or natural gas supplied and billed in that period (including estimated billings). As such, Duke Energy does not expect that there will be a significant shift in the timing or pattern of revenue recognition for such sales. Also included in the accounting analysis was the evaluation of certain long-term revenue streams including electric wholesale contracts and renewables power purchase agreements (PPAs) under this guidance. For such arrangements, Duke Energy does not expect material changes to the pattern of revenue recognition on the registrants . In addition, the power and utilities industry revenue recognition task force released several draft positions on specific industry issues in October 2017 for public comment. Duke Energy has been working closely with the industry task force and will be reviewing these updated positions to evaluate the impact, if any, on Duke Energy’s specific contracts and preliminary conclusions to date. The evaluation of other revenue streams is ongoing along with consideration of potential revisions to processes, policies and controls, primarily related to evaluating supplemental disclosures required as a result of adopting this guidance. Some revenue arrangements, such as alternative revenue programs and certain PPAs accounted for as leases, are excluded from the scope of this guidance and, therefore, will be accounted for and evaluated for separate presentation and disclosure under other relevant accounting guidance. Duke Energy continues to evaluate what information would be most useful for users of the financial statements, including information already provided in disclosures outside of the financial statement footnotes. These additional disclosures could include the disaggregation of revenues by geographic location, type of service, customer class or by duration of contract ("at-will" versus contracted revenue). Duke Energy intends to use the modified retrospective method of adoption effective January 1, 2018. Under the modified retrospective method of adoption, prior year reported results are not restated and a cumulative-effect adjustment, if applicable, is recorded to retained earnings at January 1, 2018, as if the standard had always been in effect. In addition, disclosures, if applicable, include a comparison to what would have been reported for 2018 under the previous revenue recognition rules to assist financial statement users in understanding how revenue recognition has changed as a result of this standard and to facilitate comparability with prior year reported results, which are not restated under the modified retrospective approach as described above. Duke Energy also plans to utilize certain practical expedients including applying this guidance to open contracts at the date of adoption and recognizing revenues for certain contracts under the invoice practical expedient, which allows revenue recognition to be consistent with invoiced amounts (including estimated billings) provided certain criteria are met, including consideration of whether the invoiced amounts reasonably represent the value provided to customers. While the adoption of this guidance, including the cumulative-effect adjustment, is not expected to have a material impact on either the timing or amount of revenues recognized in Duke Energy's financial statements, Duke Energy anticipates additional disclosures around the nature, amount, timing and uncertainty of our revenues and cash flows arising from contracts with customers and will continue to evaluate the requirements, as well as any additional clarifying guidance that may be issued. 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, although it can be early adopted. The guidance is applied using a modified retrospective approach. Duke Energy is currently evaluating the financial statement impact of adopting this standard and is continuing to monitor industry implementation issues, including easements, pole attachments and renewable PPAs. Other than an expected increase in assets and liabilities, the ultimate impact of the new standard has not yet been determined. Significant system enhancements, including additional processes and controls, may be required to facilitate the identification, tracking and reporting of potential leases based upon requirements of the new lease standard. Statement of Cash Flows. In November 2016, the FASB issued revised accounting guidance to reduce diversity in practice for the presentation and classification of restricted cash on the statement of cash flows. Under the updated guidance, restricted cash and restricted cash equivalents will be included within beginning-of-period and end-of-period cash and cash equivalents on the statement of cash flows. For Duke Energy, this guidance is effective for the interim and annual periods beginning January 1, 2018. The guidance will be applied using a retrospective transition method to each period presented. Upon adoption by Duke Energy, the revised guidance will result in a change to the amount of cash and cash equivalents and restricted cash explained when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. Prior to adoption, the Duke Energy Registrants reflect changes in non-current restricted cash within Cash Flows from Investing Activities and changes in current restricted cash within Cash Flows from Operating Activities on the Condensed Consolidated Statement of Cash Flows. Financial Instruments Classification and Measurement. In January 2016, the FASB issued revised accounting guidance for the classification and measurement of financial instruments. Changes in the fair value of all equity securities will be required to be recorded in net income. Current GAAP allows some changes in fair value for available-for-sale equity securities to be recorded in Accumulated other comprehensive income (AOCI). Additional disclosures will be required to present separately the financial assets and financial liabilities by measurement category and form of financial asset. An entity's equity investments that are accounted for under the equity method of accounting are not included within the scope of the new guidance. For Duke Energy, the revised accounting guidance is effective for interim and annual periods beginning January 1, 2018, by recording a cumulative-effect adjustment to retained earnings as of January 1, 2018. This guidance is expected to have minimal impact on the Duke Energy Registrant's Condensed Consolidated Statements of Operations and Comprehensive Income as changes in the fair value of most of the Duke Energy Registrants' available-for-sale equity securities are deferred as regulatory assets or liabilities pursuant to accounting guidance for regulated operations.

Acquisitions and Dispositions

Acquisitions and Dispositions	9 Months Ended
	Sep. 30, 2017
Business Combinations [Abstract]
Acquisitions and Dispositions	ACQUISITIONS AND DISPOSITIONS ACQUISITIONS The Duke Energy Registrants consolidate assets and liabilities from acquisitions as of the purchase date and include earnings from acquisitions in consolidated earnings after the purchase date. 2016 Acquisition of Piedmont Natural Gas On October 3, 2016, Duke Energy acquired all outstanding common stock of Piedmont for a total cash purchase price of $5.0 billion and assumed Piedmont's existing long-term debt, which had a fair value of approximately $2.0 billion at the time of the acquisition. The acquisition provides a foundation for Duke Energy to establish a broader, long-term strategic natural gas infrastructure platform to complement its existing natural gas pipeline investments and regulated natural gas business in the Midwest. In connection with the closing of the acquisition, Piedmont became a wholly owned subsidiary of Duke Energy. Purchase Price Allocation The purchase price allocation of the Piedmont acquisition is as follows: (in millions) Current assets $ 497 Property, plant and equipment, net 4,714 Goodwill 3,353 Other long-term assets 804 Total assets 9,368 Current liabilities, including current maturities of long-term debt 576 Long-term liabilities 1,790 Long-term debt 2,002 Total liabilities 4,368 Total purchase price $ 5,000 The fair value of Piedmont's assets and liabilities was determined based on significant estimates and assumptions that are judgmental in nature, including the amount and timing of projected future cash flows, discount rates reflecting risk inherent in the future cash flows and market prices of long-term debt. The majority of Piedmont’s operations are subject to the rate-setting authority of the NCUC, the PSCSC and the TPUC and are accounted for pursuant to accounting guidance for regulated operations. The rate-setting and cost recovery provisions currently in place for Piedmont’s regulated operations provide revenues derived from costs, including a return on investment of assets and liabilities included in rate base. Thus, the fair value of Piedmont's assets and liabilities subject to these rate-setting provisions approximates the pre-acquisition carrying value and does not reflect any net valuation adjustments. The significant assets and liabilities for which valuation adjustments were reflected within the purchase price allocation include the acquired equity method investments and long-term debt. The difference between the fair value and the pre-acquisition carrying value of long-term debt for regulated operations was recorded as a regulatory asset. The excess of the purchase price over the fair value of Piedmont's assets and liabilities on the acquisition date was recorded as goodwill. The goodwill reflects the value paid by Duke Energy primarily for establishing a broader, long-term strategic natural gas infrastructure growth platform, an improved risk profile and expected synergies resulting from the combined entities. Under Securities and Exchange Commission (SEC) regulations, Duke Energy elected not to apply push down accounting to the stand-alone Piedmont financial statements. Other Acquisition-Related Matters Duke Energy recorded realized losses on forward-starting interest rate swaps related to the acquisition financing of $22 million and $190 million for the three and nine months ended September 30, 2016, respectively. See Note 10 for additional information. During the nine months ended September 30, 2017, Piedmont recorded a $7 million software impairment resulting from planned accounting system and process integration. Pro Forma Financial Information The following unaudited pro forma financial information reflects the combined results of operations of Duke Energy and Piedmont as if the merger had occurred as of January 1, 2016. The pro forma financial information excludes potential cost savings, intercompany revenues, Piedmont’s earnings from the equity method investment in SouthStar Energy Services, LLC (SouthStar) sold immediately prior to the merger, and after-tax nonrecurring transaction and integration costs incurred by Duke Energy and Piedmont of $41 million and $161 million for the three and nine months ended September 30, 2016, respectively. See Note 3 for additional information on Piedmont's sale of SouthStar. This information has been presented for illustrative purposes only and is not necessarily indicative of the consolidated results of operations that would have been achieved or the future consolidated results of operations of Duke Energy. Three Months Ended Nine Months Ended (in millions) September 30, 2016 September 30, 2016 Operating Revenues $ 6,713 $ 17,927 Net Income Attributable to Duke Energy Corporation 1,180 2,552 DISPOSITIONS 2016 Sale of International Energy In December 2016, Duke Energy sold its International Energy businesses, excluding the equity method investment in NMC (the International Disposal Group), in two separate transactions. Duke Energy sold its Brazilian business to China Three Gorges for approximately $1.2 billion , including the assumption of debt, and its remaining Central and South American businesses to I Squared Capital in a deal also valued at approximately $1.2 billion , including the assumption of debt. The transactions generated cash proceeds of $1.9 billion , excluding transaction costs, which were primarily used to reduce Duke Energy holding company debt. The following table presents the results of the International Disposal Group, which are included in (Loss) Income from Discontinued Operations, net of tax in Duke Energy's Condensed Consolidated Statements of Operations. Interest expense directly associated with the International Disposal Group was allocated to discontinued operations. No interest from corporate level debt was allocated to discontinued operations. Three Months Ended Nine Months Ended (in millions) September 30, 2016 September 30, 2016 Operating Revenues $ 245 $ 761 Fuel used in electric generation and purchased power 60 177 Cost of natural gas 11 34 Operation, maintenance and other 85 240 Depreciation and amortization 18 62 Property and other taxes 1 6 Impairment charges (a) — 194 Loss on Sales of Other Assets and Other, net (3 ) (2 ) Other Income and Expenses, net 14 35 Interest Expense 19 63 Income before income taxes 62 18 Income tax expense (benefit) (b) 4 (48 ) Income from discontinued operations of the International Disposal Group 58 66 Income from discontinued operations of other businesses (c) 122 124 Income from Discontinued Operations, net of tax $ 180 $ 190 (a) In conjunction with the advancements of marketing efforts during 2016, Duke Energy performed recoverability tests of the long-lived asset groups of International Energy. As a result, Duke Energy determined the carrying value of certain assets in Central America was not fully recoverable and recorded a pretax impairment charge of $194 million . The charge represents the excess carrying value over the estimated fair value of the assets, which was based on a Level 3 Fair Value measurement that was primarily determined from the income approach using discounted cash flows but also considered market information obtained in 2016. (b) Includes an income tax benefit of $95 million for the nine months ended September 30, 2016, related to historical undistributed foreign earnings. See Note 17 for additional information. (c) Duke Energy recognized an income tax benefit of $122 million resulting from immaterial out of period deferred tax liability adjustments for the three and nine months ended September 30, 2016. The amount includes $34 million recorded at Duke Energy Ohio. Duke Energy has elected not to separately disclose discontinued operations on the Condensed Consolidated Statements of Cash Flows. The following table summarizes Duke Energy's cash flows from discontinued operations related to the International Disposal Group. Nine Months Ended (in millions) September 30, 2016 Cash flows provided by (used in): Operating activities $ 201 Investing activities (35 ) Other Sale-Related Matters During 2017, Duke Energy provided certain transition services to China Three Gorges and I Squared Capital. Cash flows related to providing the transition services were not material and as of September 30, 2017, all transition services related to the International Disposal Group ended. Additionally, Duke Energy will reimburse China Three Gorges and I Squared Capital for all tax obligations arising from the period preceding consummation on the transactions, totaling approximately $78 million . Duke Energy has not recorded any other liabilities, contingent liabilities or indemnifications related to the International Disposal Group.

Business Segments

Business Segments	9 Months Ended
	Sep. 30, 2017
Segment Reporting [Abstract]
Business Segments	BUSINESS SEGMENTS Operating segments are determined based on information used by the chief operating decision-maker in deciding how to allocate resources and evaluate the performance of the business. Duke Energy evaluates segment performance based on segment income. Segment income is defined as income from continuing operations net of income attributable to noncontrolling interests. Segment income includes intercompany revenues and expenses that are eliminated on the Condensed Consolidated Financial Statements. Duke Energy Due to the Piedmont acquisition and the sale of International Energy in the fourth quarter of 2016, Duke Energy's segment structure was realigned to include the following segments: Electric Utilities and Infrastructure, Gas Utilities and Infrastructure and Commercial Renewables. Prior period information has been recast to conform to the current segment structure. See Note 2 for further information on the Piedmont and International Energy transactions. 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 corporate interest expense, unallocated corporate costs, contributions to the Duke Energy Foundation and the operations of Duke Energy’s wholly owned captive insurance subsidiary, Bison Insurance Company Limited (Bison). Other also includes Duke Energy's 25 percent interest in NMC, a large regional producer of methyl tertiary butyl ether (MTBE) located in Saudi Arabia. In October 2017, Duke Energy's economic ownership interest in NMC decreased from 25 percent to 17.5 percent . 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, 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) (a)(b)(c) $ 1,020 $ 19 $ (49 ) $ 990 $ (34 ) $ — $ 956 Add back noncontrolling interests 1 Loss from discontinued operations, net of tax (2 ) Net income $ 955 Segment assets $ 118,323 $ 11,361 $ 4,216 $ 133,900 $ 2,240 $ 185 $ 136,325 Three Months Ended September 30, 2016 Electric Gas Total Utilities and Utilities and Commercial Reportable (in millions) Infrastructure Infrastructure Renewables Segments Other Eliminations Consolidated Unaffiliated revenues $ 6,332 $ 89 $ 139 $ 6,560 $ 16 $ — $ 6,576 Intersegment revenues 8 — — 8 16 (24 ) — Total revenues $ 6,340 $ 89 $ 139 $ 6,568 $ 32 $ (24 ) $ 6,576 Segment income (loss) (a)(c) $ 1,189 $ 15 $ (24 ) $ 1,180 $ (181 ) $ — $ 999 Add back noncontrolling interests 2 Income from discontinued operations, net of tax (d) 180 Net income $ 1,181 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) (a)(b)(c) $ 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 Nine Months Ended September 30, 2016 Electric Gas Total Utilities and Utilities and Commercial Reportable (in millions) Infrastructure Infrastructure Renewables Segments Other Eliminations Consolidated Unaffiliated revenues $ 16,406 $ 355 $ 365 $ 17,126 $ 40 $ — $ 17,166 Intersegment revenues 24 3 — 27 51 (78 ) — Total revenues $ 16,430 $ 358 $ 365 $ 17,153 $ 91 $ (78 ) $ 17,166 Segment income (loss) (a)(c) $ 2,557 $ 63 $ 13 $ 2,633 $ (436 ) $ — $ 2,197 Add back noncontrolling interests 5 Income from discontinued operations, net of tax (d) 190 Net income $ 2,392 (a) Other includes costs to achieve the Piedmont acquisition. See Notes 2 and 10 for additional information. (b) For the three and nine months ended September 30, 2017, Electric Utilities and Infrastructure includes an impairment charge related to the Florida settlement agreement. See Note 4 for additional information. (c) Commercial Renewables includes impairment charges related to certain wind projects. See discussion below. (d) For the three and nine months ended September 30, 2016, Income from Discontinued Operations includes an income tax benefit resulting from immaterial out of period deferred tax liability adjustments. See Note 2 for additional information. During the three and nine months ended September 30, 2017, Duke Energy recorded a pretax impairment charge of $69 million on a wholly owned non-contracted wind project. The impairment was recorded within Impairment charges on Duke Energy’s Condensed Consolidated Statements of Operations. The charge represents the excess carrying value over the estimated fair value of the project, which was based on a Level 3 Fair Value measurement that was determined from the income approach using discounted cash flows. The impairment was primarily due to the non-contracted wind project being located in a market that has experienced declining market pricing during 2017 and declining long-term forecasted energy and capacity prices, driven by low natural gas prices, additional renewable generation placed in service and lack of significant load growth. During the three and nine months ended September 30, 2016, Duke Energy recorded an other than temporary impairment (OTTI) of certain Commercial Renewables wind project investments accounted for under the equity method. The $71 million pretax impairment was recorded within Equity in earnings (losses) of unconsolidated affiliates on Duke Energy's Condensed Consolidated Statements of Operations. The other than temporary decline in value of these investments was primarily attributable to a sustained decline in market pricing where the wind investments are located, the continued projected net losses for the projects and a reduction in the projected cash distributions to the class of investment owned by Duke Energy. Duke Energy Ohio Duke Energy Ohio has two reportable operating segments, Electric Utilities and Infrastructure and Gas Utilities and Infrastructure. Electric Utilities and Infrastructure transmits and distributes electricity in portions of Ohio and generates, distributes and sells electricity in portions of Northern Kentucky. Gas Utilities and Infrastructure transports and sells natural gas in portions of Ohio and Northern Kentucky. It conducts operations primarily through Duke Energy Ohio and its wholly owned subsidiary, Duke Energy Kentucky. The remainder of Duke Energy Ohio's operations is presented as Other, which is primarily comprised of governance costs allocated by its parent, Duke Energy, and revenues and expenses related to Duke Energy Ohio's contractual arrangement to buy power from the Ohio Valley Electric Corporation's (OVEC) power plants. See Note 9 for additional information on related party transactions. 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 Segment assets $ 5,006 $ 2,708 $ 7,714 $ 51 $ 7,765 Three Months Ended September 30, 2016 Electric Gas Total Utilities and Utilities and Reportable (in millions) Infrastructure Infrastructure Segments Other Consolidated Total revenues $ 390 $ 89 $ 479 $ 10 $ 489 Segment income (loss) 52 12 64 (9 ) 55 Income from discontinued operations, net of tax (a) 34 Net income $ 89 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 Nine Months Ended September 30, 2016 Electric Gas Total Utilities and Utilities and Reportable (in millions) Infrastructure Infrastructure Segments Other Consolidated Total revenues $ 1,053 $ 358 $ 1,411 $ 22 $ 1,433 Segment income (loss) 107 57 164 (29 ) 135 Income from discontinued operations, net of tax (a) 36 Net income $ 171 (a) For the three and nine months ended September 30, 2016, Income from Discontinued Operations includes an income tax benefit resulting from immaterial out of period deferred tax liability adjustments. See Note 2 for additional information. DUKE ENERGY CAROLINAS, PROGRESS ENERGY, DUKE ENERGY PROGRESS, DUKE ENERGY FLORIDA, DUKE ENERGY INDIANA AND PIEDMONT Piedmont has one reportable segment, Gas Utilities and Infrastructure, which transports and sells natural gas. The remainder of Piedmont's operations is presented as Other, which is comprised of certain unallocated corporate costs, including acquisition-related expenses, and earnings from Piedmont's equity method investment in SouthStar prior to its sale. Piedmont sold its 15 percent membership interest in SouthStar on October 3, 2016. Piedmont's income, net of tax, from SouthStar for the three and nine months ended September 30, 2016 , was $2 million and $12 million , respectively. The remaining Subsidiary Registrants each have one reportable operating segment, Electric Utilities and Infrastructure, which generates, transmits, distributes and sells electricity. The remainder of each company's operations is presented as Other, which is comprised of certain unallocated corporate costs. Other for Progress Energy also includes interest expense on corporate debt instruments of $56 million and $167 million for the three and nine months ended September 30, 2017 , respectively, and $55 million and $166 million for the three and nine months ended September 30, 2016 , respectively. The following table summarizes the net (loss) income of Other for each of these entities. Three Months Ended Nine Months Ended September 30, September 30, (in millions) 2017 2016 2017 2016 Duke Energy Carolinas $ (6 ) $ (16 ) $ (18 ) $ (50 ) Progress Energy (32 ) (45 ) (120 ) (139 ) Duke Energy Progress (4 ) (10 ) (11 ) (26 ) Duke Energy Florida (2 ) (5 ) (7 ) (14 ) Duke Energy Indiana (2 ) (3 ) (5 ) (10 ) Piedmont (5 ) — (18 ) 7 The assets at Duke Energy Carolinas, Progress Energy, Duke Energy Progress, Duke Energy Florida and Duke Energy Indiana are substantially all included within the Electric Utilities and Infrastructure segment at September 30, 2017 . The assets at Piedmont are substantially all included within the Gas Utilities and Infrastructure segment at September 30, 2017 .

Regulatory Matters

Regulatory Matters	9 Months Ended
	Sep. 30, 2017
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 Ash Basin Closure Costs Deferral On December 30, 2016, Duke Energy Carolinas and Duke Energy Progress filed a joint petition with the NCUC seeking an accounting order authorizing deferral of certain costs incurred in connection with federal and state environmental remediation requirements related to the permanent closure of ash basins and other ash storage units at coal-fired generating facilities that have provided or are providing generation to customers located in North Carolina. Initial comments were received in March 2017, and reply comments were filed on April 19, 2017. The NCUC has consolidated Duke Energy Carolinas' and Duke Energy Progress’ coal ash deferral requests into their respective general rate case dockets for decision. See "2017 North Carolina Rate Case" sections below for additional discussion. Duke Energy Carolinas and Duke Energy Progress cannot predict the outcome of this matter. Duke Energy Carolinas 2017 North Carolina Rate Case On August 25, 2017, Duke Energy Carolinas filed an application with the NCUC for a rate increase for retail customers of approximately $647 million , which represents an approximate 13.6 percent increase in annual base revenues. The rate increase is driven by capital investments subsequent to the previous base rate case, including grid improvement projects, 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. An evidentiary hearing is scheduled to begin on February 19, 2018. Duke Energy Carolinas cannot predict the outcome of this matter. Lincoln County Combustion Turbine Addition On June 12, 2017, Duke Energy Carolinas filed an application with the NCUC for a Certificate of Public Convenience and Necessity (CPCN) to construct and operate a new 402-megawatt (MW) simple cycle advanced combustion turbine natural gas-fueled electric generating unit at its existing Lincoln County site. The request also included construction of related transmission and natural gas pipeline interconnection facilities. If approved, construction would begin in 2018 with an extended commissioning and validation period from 2020-2024 and an estimated commercial operation date in 2024. An evidentiary hearing was held in August 2017. Briefs and proposed orders were filed on October 9, 2017. A decision is expected by the end of 2017. 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 (CECPCN) for the construction and operation of a 750-MW combined-cycle natural gas-fired generating plant at Duke Energy Carolinas' existing William States Lee Generating Station in Anderson, South Carolina. Duke Energy Carolinas began construction in July 2015 and estimates a cost to build of $600 million for its share of the facility, including allowance for funds used during construction (AFUDC). The project is expected to be commercially available in late 2017. NCEMC will own approximately 13 percent of the project. On July 3, 2014, the South Carolina Coastal Conservation League (SCCL) and Southern Alliance for Clean Energy (SACE) jointly filed a Notice of Appeal with the Court of Appeals of South Carolina (S.C. Court of Appeals) seeking the court's review of the PSCSC's decision, claiming the PSCSC did not properly consider a request related to a proposed solar facility prior to granting approval of the CECPCN. The S.C. Court of Appeals affirmed the PSCSC's decision on February 10, 2016, and on March 24, 2016, denied a request for rehearing filed by SCCL and SACE. On April 21, 2016, SCCL and SACE petitioned the South Carolina Supreme Court for review of the S.C. Court of Appeals decision. On March 24, 2017, the South Carolina Supreme Court denied the request for review, thus concluding the matter. Lee Nuclear Station In December 2007, Duke Energy Carolinas applied to the NRC for combined operating licenses (COLs) for two Westinghouse Electric Company (Westinghouse) AP1000 reactors for the proposed Lee 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 decisions to incur certain project development and preconstruction costs through several separately issued orders through 2011, 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. On March 29, 2017, Westinghouse filed for voluntary Chapter 11 bankruptcy in the U.S. Bankruptcy Court for the Southern District of New York. On May 15, 2017, the NCUC issued an order requiring Duke Energy Carolinas to provide information regarding potential impacts of the Westinghouse bankruptcy on the Lee Nuclear Station, as well as Duke Energy Carolinas' plans for cost recovery and additional financial information regarding the project. As part of its 2017 North Carolina Rate Case discussed above, Duke Energy Carolinas is seeking NCUC approval to cancel the development of the Lee Nuclear Station project due to the Westinghouse bankruptcy filing and other market activity and is requesting recovery of incurred licensing and development costs. Duke Energy Carolinas will maintain the license issued by the NRC in December 2016. 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 represents an approximate 14.9 percent increase in annual base revenues. 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. Intervenors in the case filed testimony in October 2017 and Duke Energy Progress' responses are due November 6, 2017. An evidentiary hearing is scheduled to begin November 20, 2017. Duke Energy Progress cannot predict the outcome of this matter. Storm Cost Deferral Filing On December 16, 2016, Duke Energy Progress filed a petition with the NCUC requesting an accounting order to defer certain costs incurred in connection with response to Hurricane Matthew and other significant storms in 2016. The final estimate of incremental operation and maintenance and capital costs of $116 million was filed with the NCUC in September 2017. On March 15, 2017, the NCUC Public Staff filed comments supporting deferral of a portion of Duke Energy Progress’ requested amount. Duke Energy Progress filed reply comments on April 12, 2017. On July 10, 2017, the NCUC consolidated Duke Energy Progress' storm deferral request into the Duke Energy Progress rate case docket for decision. See "2017 North Carolina Rate Case" for additional discussion. Duke Energy Progress cannot predict the outcome of this matter. Western Carolinas Modernization Plan On November 4, 2015, Duke Energy Progress announced a Western Carolinas Modernization Plan, which included retirement of the existing Asheville coal-fired plant, the construction of two 280‑MW combined-cycle natural gas plants having dual fuel capability, with the option to build a third natural gas simple cycle unit in 2023 based upon the outcome of initiatives to reduce the region's power demand. The plan also included upgrades to existing transmission lines and substations, installation of solar generation and a pilot battery storage project. These investments will be made within the next seven years. Duke Energy Progress is also working with the local natural gas distribution company to upgrade an existing natural gas pipeline to serve the natural gas plant. On March 28, 2016, the NCUC issued an order approving a CPCN for the new combined-cycle natural gas plants, but denying the CPCN for the contingent simple cycle unit without prejudice to Duke Energy Progress to refile for approval in the future. On March 28, 2017, Duke Energy Progress filed an annual progress report for the construction of the combined-cycle plants with the NCUC, with an estimated cost of $893 million . Site preparation activities for the combined-cycle plants are underway and construction of these plants is scheduled to begin 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 $405 million and $492 million is included in Generation facilities to be retired, net on Duke Energy Progress' Condensed Consolidated Balance Sheets as of September 30, 2017 , and December 31, 2016 , respectively. Duke Energy Florida Hurricane Irma Storm Damage In September 2017, all of Duke Energy Florida’s service territory was impacted by Hurricane Irma, which caused significant damage, resulting in approximately 1.3 million customers experiencing outages. Total storm restoration costs, including capital, are currently estimated at approximately $500 million . These estimates could change as Duke Energy Florida receives additional information on actual costs. After depleting any existing storm reserves, which were approximately $60 million before Hurricane Irma, Duke Energy Florida is permitted to petition the FPSC for recovery of additional incremental operation and maintenance costs resulting from the storm and to replenish the storm reserve to approximately $132 million for retail customers. Duke Energy Florida plans to make this petition by the end of 2017. At September 30, 2017, Duke Energy Florida's Condensed Consolidated Balance Sheets included approximately $400 million of recoverable costs under the FPSC's storm rule in Regulatory assets within Other Noncurrent Assets related to deferred Hurricane Irma storm costs. This amount is in addition to the storm reserve replenishment discussed above as part of Duke Energy Florida's petition to the FPSC. 2017 Second Revised and Restated Settlement Agreement On October 25, 2017, the FPSC approved a 2017 Second Revised and Restated Settlement Agreement (2017 Settlement) filed by Duke Energy Florida. The 2017 Settlement replaces and supplants the Revised and Restated Stipulation and Settlement Agreement approved in November 2013 (2013 Settlement). The 2017 Settlement extends the base rate case stay-out provision from the 2013 Settlement through the end of 2021 unless actual or projected return on equity falls below 9.5 percent ; however, Duke Energy Florida is allowed a multiyear increase to its base rates of $67 million per year in 2019, 2020 and 2021, as well as base rate increases for solar generation. In addition to carrying forward the provisions contained in the 2013 Settlement related to the Crystal River 1 and 2 coal units and future generation needs in Florida, the 2017 Settlement contains provisions related to future investments in solar and renewable energy technology, future investments in AMI technology as well as recovery of existing meters, impacts of potential tax reform, an electric vehicle charging station pilot program, as well as the termination of the proposed Levy Nuclear Project discussed below. As part of the 2017 Settlement, Duke Energy Florida will not move forward with building the Levy nuclear plant and recorded an pretax impairment charge of approximately $135 million in third quarter 2017 to write off all unrecovered Levy Nuclear Project costs, including the COL. The 2017 Settlement includes provisions to recover 2017 under-recovered fuel costs of approximately $196 million over a 24 -month period beginning in January 2018. On September 1, 2017, Duke Energy Florida submitted Alternate 2018 Fuel and Capacity clause projection filings consistent with the terms of the 2017 Settlement. The updated capacity filing reflects the removal of all Levy costs. The FPSC approved Duke Energy Florida's 2018 Alternate projection filings on October 25, 2017. A final order is expected by the end of 2017. Levy Nuclear Project On July 28, 2008, Duke Energy Florida applied to the NRC for COLs for two Westinghouse AP1000 reactors at Levy (Levy Nuclear Project). In 2008, the FPSC granted Duke Energy Florida’s petition for an affirmative Determination of Need and related orders requesting cost recovery under Florida’s nuclear cost-recovery rule, together with the associated facilities, including transmission lines and substation facilities. In October 2016, the NRC issued COLs for the proposed Levy Nuclear Plant Units 1 and 2. Duke Energy Florida is not required to build the nuclear reactors as a result of the COLs being issued. On January 28, 2014, Duke Energy Florida terminated the Levy engineering, procurement and construction agreement (EPC). Duke Energy Florida may be required to pay for work performed under the EPC. Duke Energy Florida recorded an exit obligation in 2014 for the termination of the EPC. This liability was recorded within Other in Other Noncurrent Liabilities with an offset primarily to Regulatory assets on the Condensed Consolidated Balance Sheets. Duke Energy Florida is allowed to recover reasonable and prudent EPC cancellation costs from its retail customers. On May 1, 2017, Duke Energy Florida filed a request with the FPSC to recover approximately $82 million of Levy Nuclear Project costs from retail customers in 2018. As part of the 2017 Settlement discussed above, Duke Energy Florida is no longer seeking recovery of costs related to the Levy Nuclear Project and the ongoing Westinghouse litigation discussed in Note 5. All remaining Levy Nuclear Project issues have been resolved. Hines Chiller Uprate Project On February 2, 2017, Duke Energy Florida filed a petition seeking approval to include in base rates the revenue requirement for a Chiller Uprate Project (Uprate Project) at the Hines Energy Complex. The Uprate Project was placed into service in March 2017 at a cost of approximately $150 million . The annual retail revenue requirement is approximately $19 million . On March 28, 2017, the FPSC issued an order approving the revenue requirement, which was included in base rates for the first billing cycle of April 2017. Duke Energy Ohio Duke Energy Kentucky Rate Case On September 1, 2017, Duke Energy Kentucky filed a rate case with the KPSC requesting an increase in electric base rates of approximately $49 million , which represents an approximate 15 percent increase on the average customer bill. The rate increase is driven by increased investment in utility plant, increased operations and maintenance expenses, and recovery of regulatory assets. The application also includes implementation of the Environmental Surcharge Mechanism to recover environmental costs not recovered in base rates, requests to establish a Distribution Capital Investment Rider to recover incremental costs of specific programs, requests to establish a FERC Transmission Cost Reconciliation Rider to recover escalating transmission costs and modification to the Profit Sharing Mechanism to increase customers' share of proceeds from the benefits of owning generation and to mitigate shareholder risks associated with that generation. The KPSC set filing deadlines of December 29, 2017, and February 14, 2018, for intervenor testimony and rebuttal testimony, respectively. An evidentiary hearing has not been scheduled. Duke Energy Kentucky anticipates that rates will go into effect in mid-April 2018. Duke Energy Kentucky cannot predict the outcome of this matter. Electric Security Plan Filing On June 1, 2017, Duke Energy Ohio filed with the PUCO a request for a standard service offer in the form of an electric security plan (ESP). If approved by the PUCO, the term of the ESP would be from June 1, 2018, to May 31, 2024. Terms of the ESP include continuation of market-based customer rates through competitive procurement processes for generation, continuation and expansion of existing rider mechanisms and proposed new rider mechanisms relating to regulatory mandates, costs incurred to enhance the customer experience and transform the grid and a service reliability rider for vegetation management. Public hearings were held in October 2017 and an evidentiary hearing scheduled to begin on November 13, 2017, has been continued to November 28, 2017. Duke Energy Ohio cannot predict the outcome of this matter. Woodsdale Station Fuel System Filing On June 9, 2015, the FERC ruled in favor of PJM Interconnection, LLC (PJM) on a revised Tariff and Reliability Assurance Agreement including implementation of a Capacity Performance (CP) proposal and to amend sections of the Operating Agreement related to generation non-performance. The CP proposal includes performance-based penalties for non-compliance. Duke Energy Kentucky is a Fixed Resource Requirement (FRR) entity, and therefore is subject to the compliance standards through its FRR plans. A partial CP obligation will apply to Duke Energy Kentucky in the delivery year beginning June 1, 2019, with full compliance beginning June 1, 2020. Duke Energy Kentucky has developed strategies for CP compliance investments. On May 31, 2017, Duke Energy Kentucky filed an application with the KPSC requesting authority to construct an ultra-low sulfur diesel backup fuel system for the Woodsdale Station. The back-up fuel system is projected to cost approximately $55 million and, if approved, is anticipated to be in service prior to the CP compliance deadline of April 2019. Duke Energy Kentucky cannot predict the outcome of this matter. Ohio Valley Electric Corporation On March 31, 2017, Duke Energy Ohio filed for approval to adjust its existing price stabilization rider (Rider PSR), which is currently set at zero dollars, to pass through net costs related to its contractual entitlement to capacity and energy from the generating assets owned by OVEC. The filing seeks to adjust Rider PSR for OVEC costs subsequent to April 1, 2017. Duke Energy Ohio is seeking deferral authority for net costs incurred from April 1, 2017, until the new rates under Rider PSR are put into effect. Various intervenors have filed motions to dismiss or stay the proceeding and Duke Energy Ohio has opposed these filings. See Note 13 for additional discussion of Duke Energy Ohio's ownership interest in OVEC. Duke Energy Ohio cannot predict the outcome of this matter. East Bend Coal Ash Basin Filing On December 2, 2016, Duke Energy Kentucky filed with the KPSC a request for a CPCN for construction projects necessary to close and repurpose an ash basin at the East Bend facility as a result of current and proposed U.S. Environmental Protection Agency (EPA) regulations. Duke Energy Kentucky estimated a total cost of approximately $93 million in the filing and expects in-service date in the fourth quarter of 2018. On June 6, 2017, the KPSC approved the CPCN request. Base Rate Case Duke Energy Ohio filed with the PUCO an electric distribution base rate case application and supporting testimony in March 2017. Duke Energy Ohio has requested an estimated annual increase of approximately $15 million and a return on equity of 10.4 percent . The application also includes requests to continue certain current riders and establish new riders related to LED Outdoor Lighting Service and regulatory mandates. On September 26, 2017, the PUCO staff filed a report recommending a revenue decrease between approximately $18 million and $29 million and a return on equity between 9.22 percent and 10.24 percent . Objections to the staff report are due by November 9, 2017. Public hearings were held in late October and early November. An evidentiary hearing is scheduled to begin on December 11, 2017. Duke Energy Ohio cannot predict the outcome of this matter. Natural Gas Pipeline Extension Duke Energy Ohio is proposing to install a new natural gas pipeline in its Ohio service territory to increase system reliability and enable the retirement of older infrastructure. On January 20, 2017, Duke Energy Ohio filed an amended application with the Ohio Power Siting Board for approval of one of two proposed routes. A public hearing was held on June 15, 2017, and an adjudicatory hearing was scheduled to begin September 11, 2017. On August 24, 2017, an administrative law judge (ALJ) granted a request made by Duke Energy Ohio to delay the procedural schedule while it works through various issues related to the pipeline route. If approved, construction of the pipeline extension is expected to be completed before the 2020/2021 winter season. The proposed project involves the installation of a natural gas line and is estimated to cost approximately $110 million , excluding AFUDC. Advanced Metering Infrastructure On April 25, 2016, Duke Energy Kentucky filed with the KPSC an application for approval of a CPCN for the construction of advanced metering infrastructure. Duke Energy Kentucky estimates the $49 million project will take two years to complete. Duke Energy Kentucky also requested approval to establish a regulatory asset for the remaining book value of existing meter equipment and inventory to be replaced. Duke Energy Kentucky and the Kentucky attorney general entered into a stipulation to settle matters related to the application. On May 25, 2017, the KPSC issued an order to approve the stipulation with certain modifications. On June 1, 2017, Duke Energy Kentucky filed its acceptance of the modifications. Duke Energy Ohio has approximately $7 million included in Regulatory assets on its Condensed Consolidated Balance Sheets at September 30, 2017, for the book value of existing meter equipment. Accelerated Natural Gas Service Line Replacement Rider On January 20, 2015, Duke Energy Ohio filed an application for approval of an accelerated natural gas service line replacement program (ASRP). Under the ASRP, Duke Energy Ohio proposed to replace certain natural gas service lines on an accelerated basis over a 10-year period. Duke Energy Ohio also proposed to complete preliminary survey and investigation work related to natural gas service lines that are customer owned and for which it does not have valid records and, further, to relocate interior natural gas meters to suitable exterior locations where such relocation can be accomplished. Duke Energy Ohio's projected total capital and operations and maintenance expenditures under the ASRP were approximately $240 million . The filing also sought approval of a rider mechanism (Rider ASRP) to recover related expenditures. Duke Energy Ohio proposed to update Rider ASRP on an annual basis. Intervenors opposed the ASRP, primarily because they believe the program is neither required nor necessary under federal pipeline regulation. On October 26, 2016, the PUCO issued an order denying the proposed ASRP. Duke Energy Ohio's application for rehearing of the PUCO decision was denied on May 17, 2017. Energy Efficiency Cost Recovery On March 28, 2014, Duke Energy Ohio filed an application for recovery of program costs, lost distribution revenue and performance incentives related to its energy efficiency and peak demand reduction programs. These programs are undertaken to comply with environmental mandates set forth in Ohio law. The PUCO approved Duke Energy Ohio’s application but found that Duke Energy Ohio was not permitted to use banked energy savings from previous years in order to calculate the amount of allowed incentive. This conclusion represented a change to the cost recovery mechanism that had been agreed upon by intervenors and approved by the PUCO in previous cases. The PUCO granted the applications for rehearing filed by Duke Energy Ohio and an intervenor. On January 6, 2016, Duke Energy Ohio and the PUCO Staff entered into a stipulation, pending the PUCO's approval, to resolve issues related to performance incentives and the PUCO Staff audit of 2013 costs, among other issues. In December 2015, based upon the stipulation, Duke Energy Ohio re-established approximately $20 million of the revenues that had been previously reversed. On October 26, 2016, the PUCO issued an order approving the stipulation without modification. Intervenors requested a rehearing of the PUCO decision. In December 2016, the PUCO granted a rehearing for the purpose of further review. Duke Energy Ohio cannot predict the outcome of this matter. On June 15, 2016, Duke Energy Ohio filed an application for approval of a three-year energy efficiency and peak demand reduction portfolio of programs. A stipulation and modified stipulation were filed on December 22, 2016, and January 27, 2017, respectively. Under the terms of the stipulations, which included support for deferral authority of all costs and a cap on shared savings incentives, Duke Energy Ohio has offered its energy efficiency and peak demand reduction programs throughout 2017. On February 3, 2017, Duke Energy Ohio filed for deferral authority of its costs incurred in 2017 in respect of its proposed energy efficiency and peak demand reduction portfolio. The PUCO staff and one intervenor have proposed a cap on both program costs and shared savings. On September 27, 2017, the PUCO issued an order approving a modified stipulation. The modifications impose an annual cap of approximately $38 million on program costs and shared savings incentives combined, but allowed for Duke Energy Ohio to file for a waiver of costs in excess of the cap in 2017. On October 12, 2017, Duke Energy Ohio filed a motion for a waiver for recovery of costs incurred in 2017 above the annual cap. Duke Energy Ohio cannot predict the outcome of this matter. 2012 Natural Gas Rate Case/Manufactured Gas Plant Cost Recovery On November 13, 2013, the PUCO issued an order approving a settlement of Duke Energy Ohio’s natural gas base rate case and authorizing the recovery of costs incurred between 2008 and 2012 for environmental investigation and remediation of two former manufactured gas plant (MGP) sites. The PUCO order also authorized Duke Energy Ohio to continue deferring MGP environmental investigation and remediation costs incurred subsequent to 2012 and to submit annual filings to adjust the MGP rider for future costs. Intervening parties appealed this decision to the Ohio Supreme Court and on June 29, 2017, the Ohio Supreme Court issued its decision affirming the PUCO order. Appellants filed a request for reconsideration, which was denied on September 27, 2017. This matter is now final. The PUCO order also contained deadlines for completing the MGP environmental investigation and remediation costs at the MGP sites. For the property known as the East End site, the PUCO order established a deadline of December 31, 2016, which was subsequently extended to December 31, 2019. In January 2017, intervening parties filed for rehearing of the PUCO's decision. On February 8, 2017, the PUCO denied the rehearing request. As of September 30, 2017, Duke Energy Ohio had approximately $36 million included in Regulatory assets on the Condensed Consolidated Balance Sheets for future remediation costs expected to be incurred at the East End site. Regional Transmission Organization Realignment Duke Energy Ohio, including Duke Energy Kentucky, transferred control of its transmission assets from Midcontinent Independent System Operator, Inc. (MISO) to PJM, effective December 31, 2011. The PUCO approved a settlement related to Duke Energy Ohio’s recovery of certain costs of the Regional Transmission Organization (RTO) realignment via a non-bypassable rider. Duke Energy Ohio is allowed to recover all MISO Transmission Expansion Planning (MTEP) costs, including but not limited to Multi Value Project (MVP) costs, directly or indirectly charged to Ohio customers. Duke Energy Ohio also agreed to vigorously defend against any charges for MVP projects from MISO. The KPSC also approved a request to effect the RTO realignment, subject to a commitment not to seek double recovery in a future rate case of the transmission expansion fees that may be charged by MISO and PJM in the same period or overlapping periods. Duke Energy Ohio had a recorded liability for its exit obligation and share of MTEP costs, excluding MVP, of $90 million at September 30, 2017 , and December 31, 2016 , recorded within Other in Current liabilities and Other in Other Noncurrent Liabilities on the Condensed Consolidated Balance Sheets. The retail portions of MTEP costs billed by MISO are recovered by Duke Energy Ohio through a non-bypassable rider. As of September 30, 2017 , and December 31, 2016 , Duke Energy Ohio had $71 million recorded in Regulatory assets on the Condensed Consolidated Balance Sheets. MVP. MISO approved 17 MVP proposals prior to Duke Energy Ohio’s exit from MISO on December 31, 2011. Construction of these projects is expected to continue through 2020. Costs of these projects, including operating and maintenance costs, property and income taxes, depreciation and an allowed return, are allocated and billed to MISO transmission owners. On December 29, 2011, MISO filed a tariff with the FERC providing for the allocation of MVP costs to a withdrawing owner based on monthly energy usage. The FERC set for hearing (i) whether MISO’s proposed cost allocation methodology to transmission owners who withdrew from MISO prior to January 1, 2012, is consistent with the tariff at the time of their withdrawal from MISO and, (ii) if not, what the amount of and methodology for calculating any MVP cost responsibility should be. In 2012, MISO estimated Duke Energy Ohio’s MVP obligation over the period from 2012 to 2071 at $2.7 billion , on an undiscounted basis. On July 16, 2013, a FERC ALJ issued an initial decision. Under this Initial Decision, Duke Energy Ohio would be liable for MVP costs. Duke Energy Ohio filed exceptions to the initial decision, requesting FERC to overturn the ALJ’s decision. On October 29, 2015, the FERC issued an order reversing the ALJ's decision. The FERC ruled the cost allocation methodology is not consistent with the MISO tariff and that Duke Energy Ohio has no liability for MVP costs after its withdrawal from MISO. On May 19, 2016, the FERC denied the request for rehearing filed by MISO and the MISO Transmission Owners. On July 15, 2016, the MISO Transmission Owners filed a petition for review with the U.S. Court of Appeals for the Sixth Circuit. On June 21, 2017, a three-judge panel affirmed FERC's 2015 decision holding that Duke Energy Ohio has no liability for the cost of the MVP projects constructed after Duke Energy Ohio's withdrawal from MISO. MISO did not file further petitions for review and this matter is now final. Duke Energy Indiana Coal Combustion Residual Plan On March 17, 2016, Duke Energy Indiana filed with the IURC a request for approval of its first group of federally mandated CCR rule compliance projects (Phase I CCR Compliance Projects) to comply with the EPA's CCR rule. The projects in this Phase I filing are CCR compliance projects, including the conversion of Cayuga and Gibson stations to dry bottom ash handling and related water treatment. Duke Energy Indiana has requested timely recovery of approximately $380 million in retail capital costs, including AFUDC, and recovery of incremental operating and maintenance costs under a federal mandate tracker that provides for timely recovery of 80 percent of such costs and deferral with carrying costs of 20 percent of such costs for recovery in a subsequent retail base rate case. On January 24, 2017, Duke Energy Indiana and various intervenors filed a settlement agreement with the IURC. Terms of the settlement include recovery of 60 pe

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2017
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, 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 Nine Months Ended September 30, 2016 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 $ 94 $ 10 $ 17 $ 3 $ 14 $ 54 $ 12 $ 1 Provisions/adjustments 34 5 5 2 3 6 20 — Cash reductions (12 ) (4 ) (6 ) (2 ) (4 ) (1 ) (2 ) — Balance at end of period $ 116 $ 11 $ 16 $ 3 $ 13 $ 59 $ 30 $ 1 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 $ 58 Duke Energy Carolinas 20 Duke Energy Ohio 30 Duke Energy Indiana 3 Piedmont 2 North Carolina and South Carolina Ash Basins In February 2014, a break in a stormwater pipe beneath an ash basin at Duke Energy Carolinas’ retired Dan River Steam Station caused a release of ash basin water and ash into the Dan River. Duke Energy Carolinas estimates 30,000 to 39,000 tons of ash and 24 million to 27 million gallons of basin water were released into the river. In July 2014, Duke Energy completed remediation work identified by the EPA. Future costs related to the Dan River release, including future civil enforcement, future regulatory directives, natural resources damages, future claims or litigation and long-term environmental impact costs, cannot be reasonably estimated at this time. The North Carolina Department of Environmental Quality (NCDEQ) has historically assessed Duke Energy Carolinas and Duke Energy Progress with Notices of Violations (NOV) for violations that were most often resolved through satisfactory corrective actions and minor, if any, fines or penalties. Subsequent to the Dan River ash release, Duke Energy Carolinas and Duke Energy Progress have been served with a higher level of NOVs, including assessed penalties for violations at L.V. Sutton Combined Cycle Plant (Sutton) and Dan River Steam Station. Duke Energy Carolinas and Duke Energy Progress cannot predict whether the NCDEQ will assess future penalties related to existing unresolved NOVs and if such penalties would be material. See "NCDEQ Notices of Violation" section below for additional discussion. LITIGATION Duke Energy Duke Energy no longer has exposure to litigation matters related to the International Disposal Group as a result of the divestiture of the business in December 2016. See Note 2 for additional information related to the sale of International Energy. Ash Basin Shareholder Derivative Litigation Five shareholder derivative lawsuits were filed in Delaware Chancery Court related to the release at Dan River and to the management of Duke Energy’s ash basins. On October 31, 2014, the five lawsuits were consolidated in a single proceeding titled In Re Duke Energy Corporation Coal Ash Derivative Litigation . On December 2, 2014, plaintiffs filed a Corrected Verified Consolidated Shareholder Derivative Complaint (Consolidated Complaint). The Consolidated Complaint names as defendants several current and former Duke Energy officers and directors (collectively, the Duke Energy Defendants). Duke Energy is named as a nominal defendant. The Consolidated Complaint alleges the Duke Energy Defendants breached their fiduciary duties by failing to adequately oversee Duke Energy’s ash basins and that these breaches of fiduciary duty may have contributed to the incident at Dan River and continued thereafter. The lawsuit also asserts claims against the Duke Energy Defendants for corporate waste (relating to the money Duke Energy has spent and will spend as a result of the fines, penalties and coal ash removal) and unjust enrichment (relating to the compensation and director remuneration that was received despite these alleged breaches of fiduciary duty). The lawsuit seeks both injunctive relief against Duke Energy and restitution from the Duke Energy Defendants. On April 22, 2016, plaintiffs filed an Amended Verified Consolidated Shareholder Derivative Complaint (Amended Complaint) making the same allegations as in the Consolidated Complaint. The Duke Energy Defendants filed a motion to dismiss the Amended Complaint on June 21, 2016. On December 14, 2016, the Delaware Chancery Court entered an order dismissing the Amended Complaint. Plaintiffs filed an appeal to the Delaware Supreme Court on January 9, 2017. Oral argument was held on September 27, 2017, and a decision is pending. On October 30, 2015, shareholder Saul Bresalier filed a shareholder derivative complaint (Bresalier Complaint) in the U.S. District Court for the District of Delaware. The lawsuit alleges that several current and former Duke Energy officers and directors (Bresalier Defendants) breached their fiduciary duties in connection with coal ash environmental issues, the post-merger change in Chief Executive Officer (CEO) and oversight of political contributions. Duke Energy is named as a nominal defendant. The Bresalier Complaint contends that the appointed Demand Review Committee failed to appropriately consider the shareholder’s earlier demand for litigation and improperly decided not to pursue claims against the Bresalier Defendants. On March 30, 2017, the court granted Defendants’ Motion to Dismiss on the claims relating to coal ash environmental issues and political contributions. As discussed below, a settlement agreement was approved for the merger-related claims in the Bresalier Complaint, and those claims were dismissed. On September 8, 2017, Bresalier filed a notice of appeal to the U.S. Court of Appeals for the Third Circuit (Third Circuit Court) challenging the dismissal of his coal ash and political contribution claims. Pursuant to a scheduling order issued by the Third Circuit Court, briefing will be complete on December 20, 2017. It is not possible to predict whether Duke Energy will incur any liability or to estimate the damages, if any, it might incur in connection with these matters. Progress Energy Merger Shareholder Litigation On May 31, 2013, the Delaware Chancery Court consolidated four shareholder derivative lawsuits filed in 2012. The Court also appointed a lead plaintiff and counsel for plaintiffs and designated the case as In Re Duke Energy Corporation Derivative Litigation (Merger Chancery Litigation). The lawsuit names as defendants the Legacy Duke Energy Directors. Duke Energy is named as a nominal defendant. The case alleges claims for breach of fiduciary duties of loyalty and care in connection with the post-merger change in CEO. Two shareholder Derivative Complaints, filed in 2012 in federal district court in Delaware, were consolidated as Tansey v. Rogers, et al. The case alleges claims against the Legacy Duke Energy Directors for breach of fiduciary duty and waste of corporate assets, as well as claims under Section 14(a) and 20(a) of the Exchange Act. Duke Energy is named as a nominal defendant. On December 21, 2015, Plaintiff filed a Consolidated Amended Complaint asserting the same claims contained in the original complaints. The Legacy Duke Energy Directors reached an agreement-in-principle to settle the Merger Chancery Litigation, conditioned on dismissal as well, of the Tansey v. Rogers, et al case and the merger-related claims in the Bresalier Complaint discussed above, which was approved by the Delaware Chancery Court on July 13, 2017. The entire settlement amount was funded by insurance. The settlement amount, less court-approved attorney fees, totaled $20 million and was paid to Duke Energy in third quarter 2017. Price Reporting Cases Duke Energy Trading and Marketing, LLC (DETM), a non-operating Duke Energy affiliate, was a defendant, along with numerous other energy companies, in four class-action lawsuits and a fifth single-plaintiff lawsuit in a consolidated federal court proceeding in Nevada. Each of these lawsuits contained similar claims that defendants allegedly manipulated natural gas markets by various means, including providing false information to natural gas trade publications and entering into unlawful arrangements and agreements in violation of the antitrust laws of the respective states. Plaintiffs sought damages in unspecified amounts. In February 2016, DETM reached agreements in principle to settle all of the pending lawsuits. Settlement of the single-plaintiff settlement was finalized and paid in March 2016. The proposed settlement of the class action lawsuits was approved by the Court and all settlement amounts, which are not material to Duke Energy, have been paid. Duke Energy Carolinas and Duke Energy Progress Coal Ash Insurance Coverage Litigation In March 2017, Duke Energy Carolinas and Duke Energy Progress filed a civil action in North Carolina Superior Court against various insurance providers. The lawsuit seeks payment for coal ash-related liabilities covered by third-party liability insurance policies. The insurance policies were issued between 1971 and 1986 and provide third-party liability insurance for property damage. The civil action seeks damages for breach of contract and indemnification for costs arising from the Coal Ash Act and the EPA CCR rule at 15 coal-fired plants in North Carolina and South Carolina. Duke Energy Carolinas and Duke Energy Progress cannot predict the outcome of this matter. NCDEQ 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. The litigation is concluded for these seven plants. Litigation continues for the remaining seven plants. 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. On March 15, 2017, Duke Energy Carolinas and Duke Energy Progress filed a Notice of Appeal to challenge the trial court’s order. The parties were unable to reach an agreement at mediation in April 2017. The parties submitted briefs to the court on remaining issues to be tried and a ruling is pending. On August 22, 2017, Duke Energy Carolinas and Duke Energy Progress filed a Petition for Discretionary Review, requesting the North Carolina Supreme Court to accept the appeal. On August 24, 2017, SELC filed a motion to dismiss the appeal. Duke Energy Carolinas' and Duke Energy Progress’ opening appellate briefs were filed on October 12, 2017. It is not possible to predict any liability or estimate any damages Duke Energy Carolinas or Duke Energy Progress might incur in connection with these matters. Federal Citizens Suits On June 13, 2016, the Roanoke River Basin Association (RRBA) filed a federal citizen suit in the Middle District of North Carolina alleging unpermitted discharges to surface water and groundwater violations at the Mayo Plant. On August 19, 2016, Duke Energy Progress filed a Motion to Dismiss. On April 26, 2017, the court entered an order dismissing four of the claims in the federal citizen suit. Two claims relating to alleged violations of National Pollutant Discharge Elimination System (NPDES) permit provisions survived the motion to dismiss, and Duke Energy Progress filed its response on May 10, 2017. The parties are engaged in pre-trial discovery. Trial has been scheduled for July 9, 2018. On March 16, 2017, RRBA served Duke Energy Progress with a Notice of Intent to Sue under the CWA for alleged violations of effluent standards and limitations at the Roxboro Plant. In anticipation of litigation, Duke Energy Progress filed a Complaint for Declaratory Relief in the U.S. District Court for the Western District of Virginia on May 11, 2017, which was subsequently dismissed. On May 16, 2017, RRBA filed a federal citizen suit in the U.S. District Court for the Middle District of North Carolina which asserts two claims relating to alleged violations of NPDES permit provisions and one claim relating to the use of nearby water bodies. 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 on August 21, 2017. On August 2, 2017, RRBA filed a federal citizen suit in the U.S. District Court for the Middle District of North Carolina challenging the closure plans at the Roxboro Plant under the EPA CCR Rule. Duke Energy Progress filed a motion to dismiss on October 2, 2017. On October 3, 2017, various parties served Duke Energy Carolinas with a Notice of Intent to Sue under the CWA for alleged violations at Duke Energy Carolinas' Belews Creek Steam Station (Belews Creek). A lawsuit may be filed sixty days after service of notice. It is not possible to predict whether Duke Energy Carolinas or Duke Energy Progress will incur any liability or to estimate the damages, if any, they might incur in connection with these matters. Five previously filed cases involving the Riverbend, Cape Fear, H.F. Lee, Sutton and Buck plants were dismissed or settled in 2016. Groundwater Contamination Claims Beginning in May 2015, a number of residents living in the vicinity of the North Carolina facilities with ash basins received letters from the NCDEQ advising them not to drink water from the private wells on their land tested by the NCDEQ as the samples were found to have certain substances at levels higher than the criteria set by the North Carolina Department of Health and Human Services (DHHS). Results of Comprehensive Site Assessments (CSAs) testing performed by Duke Energy under the Coal Ash Act have been consistent with historical data provided to state regulators over many years. The DHHS and NCDEQ sent follow-up letters on October 15, 2015, to residents near coal ash basins who 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. Duke Energy Carolinas and Duke Energy Progress have recognized reserves of $19 million and $4 million , respectively. On August 23, 2017, a class action suit was filed in Wake County Superior Court, North Carolina, against Duke Energy Carolinas and Duke Energy Progress on behalf of certain property owners living near coal ash impoundments at Allen, Asheville, Belews Creek, Buck, Cliffside, Lee, Marshall, Mayo and Roxboro. The class is defined as those who are “well-eligible” under the Coal Ash Act or those to whom Duke Energy has promised a permanent replacement water supply and seeks declaratory and injunctive relief, along with compensatory damages. Plaintiffs allege that Duke Energy’s improper maintenance of coal ash impoundments caused harm, particularly through groundwater contamination. Despite NCDEQ’s preliminary approval, Plaintiffs contend that Duke Energy’s proposed permanent water solutions plan fails to comply with the Coal Ash Act. On September 28, 2017, Duke Energy Carolinas and Duke Energy Progress filed a Motion to Dismiss and Motion to Strike the class designation. 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 one 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. It is not possible to estimate the maximum exposure of loss, if any, that may occur in connection with current claims or future claims, which 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, 2017 , there were 120 asserted claims for non-malignant cases with cumulative relief sought of up to $29 million , and 57 asserted claims for malignant cases with cumulative relief sought of up to $16 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 $486 million at September 30, 2017 , and $512 million at December 31, 2016 . 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 2036, 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 2036 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 $797 million in excess of the self-insured retention. Receivables for insurance recoveries were $570 million at September 30, 2017 , and $ 587 million at December 31, 2016 . 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 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. The appeal, which has been fully briefed, was heard on August 22, 2017, and a decision is pending. Duke Energy Florida cannot predict the outcome of this appeal. 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 seeks recovery of $54 million in milestone payments in excess of work performed under an EPC for Levy as well as a determination by the court of the amounts due to Westinghouse as a result of the termination of the EPC. Duke Energy Florida recognized an exit obligation as a result of the termination of the EPC. On March 31, 2014, Westinghouse filed a lawsuit against Duke Energy Florida in U.S. District Court for the Western District of Pennsylvania. The Pennsylvania lawsuit alleged damages under the EPC 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 will 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 on the parties' respective Motions for Summary Judgment, ruling in favor of Westinghouse on a $30 million termination fee claim and dismissing Duke Energy Florida's $54 million refund claim, but stating that Duke Energy Florida could use the refund claim to offset any damages for termination costs. Westinghouse's claim for termination costs was unaffected by this ruling and continued to trial. At trial, Westinghouse reduced its claim for termination costs from $482 million to $424 million . Following a trial on the matter, the court issued its final order in December 2016 denying Westinghouse’s claim for termination costs and re-affirming its earlier ruling in favor of Westinghouse on the $30 million termination fee and Duke Energy Florida’s refund claim. Judgment was entered against Duke Energy Florida in the amount of approximately $34 million , which includes prejudgment interest. Westinghouse has appealed the trial court's order to the U.S. Court of Appeals for the Fourth Circuit (Fourth Circuit Court) and Duke Energy Florida has cross-appealed. Duke Energy Florida cannot predict the ultimate outcome of the appeal of the trial court's order. 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, and the parties await a decision form the Fourth Circuit Court on whether it will allow oral argument of the appeal. Ultimate resolution of these matters could have a material effect on the results of operations, financial position or cash flows of Duke Energy Florida. See discussion of the 2017 Settlement and the Levy Nuclear Project in Note 4 for additional information regarding recovery of costs related to Westinghouse. 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 6th Circuit and briefing has been completed. Duke Energy Florida cannot predict the outcome of this appeal. 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 discussed above related to the termination of an EPC contract. 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, 2017 December 31, 2016 Reserves for Legal Matters Duke Energy $ 83 $ 98 Duke Energy Carolinas 23 23 Progress Energy 56 59 Duke Energy Progress 13 14 Duke Energy Florida 28 28 Duke Energy Ohio — 4 Piedmont 2 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, 2017
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). Refer to the "Available Credit Facilities" section below regarding amounts issued under the Three Year Revolver and the Piedmont Term Loan facilities. Nine Months Ended September 30, 2017 Duke Duke Duke Duke Maturity Interest Duke Energy Energy Energy Energy Issuance Date Date Rate Energy (Parent) Progress Florida Ohio Unsecured Debt April 2017 (a) April 2025 3.364 % $ 420 $ 420 $ — $ — $ — June 2017 (b) June 2020 2.100 % 330 330 — — — August 2017 (c) August 2022 2.400 % 500 500 — — — August 2017 (c) August 2027 3.150 % 750 750 — — — August 2017 (c) August 2047 3.950 % 500 500 — — — Secured Debt February 2017 (d) June 2034 4.120 % 587 — — — — August 2017 (e) December 2036 4.110 % 233 — — — — First Mortgage Bonds January 2017 (f) January 2020 1.850 % 250 — — 250 — January 2017 (f) January 2027 3.200 % 650 — — 650 — March 2017 (g) June 2046 3.700 % 100 — — — 100 September 2017 (h) September 2020 1.500 % (i) 300 — 300 — — September 2017 (h) September 2047 3.600 % 500 — 500 — — Total issuances $ 5,120 $ 2,500 $ 800 $ 900 $ 100 (a) Proceeds were used to refinance $ 400 million of unsecured debt at maturity and to repay a portion of outstanding commercial paper. (b) Debt issued to repay a portion of outstanding commercial paper. (c) Debt issued to repay at maturity $700 million of unsecured debt, to repay outstanding commercial paper and for general corporate purposes. (d) Portfolio financing of four Texas and Oklahoma wind facilities. Secured by substantially all of the assets of these wind facilities and nonrecourse to Duke Energy. Proceeds were used to reimburse Duke Energy for a portion of previously funded construction expenditures. (e) Portfolio financing of eight solar facilities located in California, Colorado and New Mexico. Secured by substantially all of the assets of these solar facilities and nonrecourse to Duke Energy. Proceeds were used to reimburse Duke Energy for a portion of previously funded construction expenditures. (f) Debt issued to fund capital expenditures for ongoing construction and capital maintenance, to repay a $250 million aggregate principal amount of bonds at maturity and for general corporate purposes. (g) Proceeds were used to fund capital expenditures for ongoing construction, capital maintenance and for general corporate purposes. (h) Debt issued to repay at maturity a $200 million aggregate principal amount of bonds due November 2017, pay down intercompany short-term debt and for general corporate purposes, including capital expenditures. (i) Debt issuance has a floating interest rate. 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, 2017 Unsecured Debt Duke Energy (Parent) June 2018 6.250 % $ 250 Duke Energy (Parent) June 2018 2.100 % 500 First Mortgage Bonds Duke Energy Progress November 2017 1.516 % (b) 200 Duke Energy Carolinas January 2018 5.250 % 400 Duke Energy Carolinas April 2018 5.100 % 300 Duke Energy Florida June 2018 5.650 % 500 Other (a) 335 Current maturities of long-term debt $ 2,485 (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 March 2017, Duke Energy amended its Master Credit Facility to increase its capacity from $7.5 billion to $8 billion , and to extend the termination date of the facility from January 30, 2020, to March 16, 2022. The amendment also added Piedmont as a borrower within the Master Credit Facility. Piedmont's separate $850 million credit facility was terminated in connection with the amendment. With the amendment, the Duke Energy Registrants, excluding Progress Energy (Parent), have borrowing capacity under the Master Credit Facility up to 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, 2017 Duke Duke Duke Duke Duke Duke Duke Energy Energy Energy Energy Energy Energy (in millions) Energy (Parent) Carolinas Progress Florida Ohio Indiana Piedmont Facility size (a) $ 8,000 $ 2,850 $ 1,350 $ 1,250 $ 1,000 $ 450 $ 600 $ 500 Reduction to backstop issuances Commercial paper (b) (1,569 ) (404 ) (636 ) (150 ) — (25 ) (150 ) (204 ) Outstanding letters of credit (60 ) (51 ) (4 ) (2 ) (1 ) — — (2 ) Tax-exempt bonds (81 ) — — — — — (81 ) — Coal ash set-aside (500 ) — (250 ) (250 ) — — — — Available capacity under the Master Credit Facility $ 5,790 $ 2,395 $ 460 $ 848 $ 999 $ 425 $ 369 $ 294 (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 In June 2017, Duke Energy (Parent) entered into a three -year $1.0 billion revolving credit facility (the Three Year Revolver). Borrowings under this facility will be used for general corporate purposes. As of September 30, 2017 , $270 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 June 2017, Piedmont entered into an 18 -month term loan facility with commitments totaling $250 million (the Piedmont Term Loan). Borrowings under the facility will be used for general corporate purposes. As of September 30, 2017 , the entire $250 million has been drawn under the Piedmont Term Loan. This balance is classified as Long-Term Debt on Piedmont's Condensed Consolidated Balance Sheets. The terms and conditions of the Piedmont Term Loan are generally consistent with those governing Duke Energy's Master Credit Facility.

Asset Retirement Obligations

Asset Retirement Obligations	9 Months Ended
	Sep. 30, 2017
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, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Decommissioning of Nuclear Power Facilities (a) $ 5,337 $ 1,916 $ 3,235 $ 2,536 $ 699 $ — $ — $ — Closure of Ash Impoundments 4,594 1,650 2,124 2,105 19 42 777 — Other 274 35 80 35 45 39 16 15 Total ARO $ 10,205 $ 3,601 $ 5,439 $ 4,676 $ 763 $ 81 $ 793 $ 15 Less: current portion 619 304 250 250 — 6 58 — Total noncurrent ARO $ 9,586 $ 3,297 $ 5,189 $ 4,426 $ 763 $ 75 $ 735 $ 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, 2016 (a) $ 10,611 $ 3,895 $ 5,475 $ 4,697 $ 778 $ 77 $ 866 $ 14 Accretion expense (b) 329 140 172 147 25 3 25 1 Liabilities settled (c) (430 ) (201 ) (193 ) (152 ) (41 ) (4 ) (26 ) (7 ) Liabilities incurred in the current year 48 5 — — — 7 27 7 Revisions in estimates of cash flows (d) (353 ) (238 ) (15 ) (16 ) 1 (2 ) (99 ) — Balance at September 30, 2017 $ 10,205 $ 3,601 $ 5,439 $ 4,676 $ 763 $ 81 $ 793 $ 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, 2017 , substantially all accretion expense relates to Duke Energy's regulated electric 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 favorable contract prices for closure of ash impoundments 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 and Intangible Assets

Goodwill and Intangible Assets	9 Months Ended
	Sep. 30, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	GOODWILL AND INTANGIBLE ASSETS 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, 2017 , and December 31, 2016 . Electric Utilities Gas Utilities Commercial (in millions) and Infrastructure and Infrastructure Renewables Total Goodwill Balance at December 31, 2016 $ 17,379 $ 1,924 $ 122 $ 19,425 Accumulated impairment charges (a) — — (7 ) (7 ) Goodwill Balance at September 30, 2017 $ 17,379 $ 1,924 $ 115 $ 19,418 (a) Duke Energy evaluated the recoverability of goodwill in the third quarter of 2017 and recorded an impairment of $7 million related to the Energy Management Solutions reporting unit within the Commercial Renewables segment. The fair value of the reporting unit was determined based on the market approach, which estimates fair value based on market comparables within the energy technologies industry. 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, 2017 , and December 31, 2016 . Progress Energy Progress Energy's Goodwill is included in the Electric Utilities and Infrastructure operating segment and there are no accumulated impairment charges. Piedmont Piedmont's Goodwill is included in the Gas Utilities and Infrastructure operating segment and there are no accumulated impairment charges. Effective November 1, 2016, Piedmont's fiscal year was changed from October 31 to December 31. Effective with this change, Piedmont changed the date of its annual impairment testing of goodwill from October 31 to August 31 to align with the other Duke Energy Registrants. Impairment Testing Duke Energy, Progress Energy, Duke Energy Ohio and Piedmont are required to perform an annual goodwill impairment test as of the same date each year and, accordingly, perform their annual impairment testing of goodwill as of August 31. Duke Energy, Progress Energy, Duke Energy Ohio and Piedmont update their test between annual tests if events or circumstances occur that would more likely than not reduce the fair value of a reporting unit below its carrying value. Except for the Energy Management Solutions reporting unit, the fair value of all other reporting units for Duke Energy, Progress Energy, Duke Energy Ohio and Piedmont exceeded their respective carrying values at the date of the annual impairment analysis. As such, no other impairment charges were recorded in the third quarter of 2017.

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2017
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) 2017 2016 2017 2016 Duke Energy Carolinas Corporate governance and shared service expenses (a) $ 205 $ 204 $ 645 $ 620 Indemnification coverages (b) 5 5 17 16 JDA revenue (c) 9 10 42 21 JDA expense (c) 39 36 91 127 Intercompany natural gas purchases (d) 3 — 5 — Progress Energy Corporate governance and shared service expenses (a) $ 208 $ 182 $ 555 $ 515 Indemnification coverages (b) 10 9 29 25 JDA revenue (c) 39 36 91 127 JDA expense (c) 9 10 42 21 Intercompany natural gas purchases (d) 19 — 57 — Duke Energy Progress Corporate governance and shared service expenses (a) $ 114 $ 103 $ 321 $ 292 Indemnification coverages (b) 4 4 11 10 JDA revenue (c) 39 36 91 127 JDA expense (c) 9 10 42 21 Intercompany natural gas purchases (d) 19 — 57 — Duke Energy Florida Corporate governance and shared service expenses (a) $ 94 $ 79 $ 234 $ 223 Indemnification coverages (b) 6 5 18 15 Duke Energy Ohio Corporate governance and shared service expenses (a) $ 90 $ 89 $ 275 $ 261 Indemnification coverages (b) 1 1 3 4 Duke Energy Indiana Corporate governance and shared service expenses (a) $ 93 $ 96 $ 281 $ 279 Indemnification coverages (b) 2 2 6 6 Piedmont Corporate governance and shared service expenses (a) $ 10 $ — $ 25 $ — Indemnification coverages (b) 1 — 2 — Intercompany natural gas sales (d) 22 — 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 Regulated natural gas revenues, and Duke Energy Carolinas and Duke Energy Progress record the related purchases in Fuel used in electric generation and purchased power on their respective Condensed Consolidated Statements of Operations and Comprehensive Income. The amounts are not eliminated in accordance with rate-based accounting regulations. For the three and nine months ended September 30, 2016 , which was prior to the Piedmont acquisition, Piedmont recorded $19 million and $57 million , respectively, of natural gas sales with Duke Energy Progress and $1 million and $ 3 million , respectively, with Duke Energy Carolinas. In addition to the amounts presented above, the Subsidiary Registrants have other affiliate transactions, including rental of office space, participation in a money pool arrangement, other operational transactions and their proportionate share of certain charged expenses. See Note 6 to the Consolidated Financial Statements in the Annual Report on Form 10-K for the year ended December 31, 2016, for more information regarding the money pool. These transactions of the Subsidiary Registrants were not material for the three and nine months ended September 30, 2017 , and 2016 . As discussed in Note 13 , certain trade receivables have been sold by Duke Energy Ohio and Duke Energy Indiana to CRC, an affiliate formed by a subsidiary of Duke Energy. The proceeds obtained from the sales of receivables are largely cash but also include a subordinated note from the affiliate 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, 2017 , and 2016 , 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 2017 2016 2017 2016 Cardinal Transportation Costs $ 2 $ 3 $ 6 $ 7 Pine Needle Natural Gas Storage Costs 2 3 6 8 Hardy Storage Natural Gas Storage Costs 2 2 7 7 Total $ 6 $ 8 $ 19 $ 22 Piedmont had accounts payable to its equity method investments of $2 million at September 30, 2017 , and December 31, 2016 , 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, 2017 Intercompany income tax receivable $ — $ 170 $ — $ 120 $ — $ — $ 89 Intercompany income tax payable 173 — 46 — 18 104 — December 31, 2016 Intercompany income tax receivable $ 1 $ — $ — $ 37 $ — $ — $ — Intercompany income tax payable — 37 90 — 1 3 38

Derivatives and Hedging

Derivatives and Hedging	9 Months Ended
	Sep. 30, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives and Hedging	DERIVATIVES AND HEDGING The Duke Energy Registrants use commodity and interest rate contracts to manage commodity price risk and interest rate risk. The primary use of commodity derivatives is to hedge the generation portfolio against changes in the prices of electricity and natural gas. Piedmont enters into natural gas supply contracts to provide diversification, reliability and natural gas cost benefits to its customers. Interest rate swaps are used to manage interest rate risk associated with borrowings. All derivative instruments not identified as NPNS are recorded at fair value as assets or liabilities on the 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, 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 include contracts not designated as a hedge because they are accounted for under regulatory accounting and contracts that do not qualify for hedge accounting. Duke Energy’s interest rate swaps for its regulated operations employ regulatory accounting. With regulatory accounting, the mark-to-market gains or losses on the swaps are deferred as regulatory liabilities or regulatory assets, respectively. Regulatory assets and liabilities are amortized consistent with the treatment of the related costs in the ratemaking process. The accrual of interest on the swaps is recorded as Interest Expense. In August 2016, Duke Energy unwound $1.4 billion of forward-starting interest rate swaps associated with the Piedmont acquisition financing. The swaps were considered undesignated as they did not qualify for hedge accounting. For the three and nine months ended September 30, 2016 , losses on the swaps of $22 million and $190 million , respectively, were included within Interest Expense on Duke Energy's Condensed Consolidated Statements of Operations. See Note 2 for additional information related to the Piedmont acquisition. The following table shows notional amounts of outstanding derivatives related to interest rate risk. September 30, 2017 Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Cash flow hedges (a) $ 703 $ — $ — $ — $ — $ — Undesignated contracts 927 400 500 250 250 27 Total notional amount $ 1,630 $ 400 $ 500 $ 250 $ 250 $ 27 December 31, 2016 Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Cash flow hedges (a) $ 750 $ — $ — $ — $ — $ — Undesignated contracts 927 400 500 250 250 27 Total notional amount $ 1,677 $ 400 $ 500 $ 250 $ 250 $ 27 (a) Duke Energy includes amounts related to consolidated VIEs of $703 million and $750 million as of September 30, 2017 , and December 31, 2016 , respectively. 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, 2017 Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy Carolinas Energy Progress Florida Indiana Piedmont Electricity (gigawatt-hours) 112 — — — — 112 — Natural gas (millions of dekatherms) 786 103 193 124 69 1 489 December 31, 2016 Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy Carolinas Energy Progress Florida Indiana Piedmont Electricity (gigawatt-hours) 147 — — — — 147 — Natural gas (millions of dekatherms) 890 91 269 118 151 1 529 LOCATION AND FAIR VALUE OF DERIVATIVE ASSETS AND LIABILITIES RECOGNIZED 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, 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 $ 48 $ 6 $ 10 $ 5 $ 4 $ 2 $ 28 $ 2 Noncurrent 6 2 4 3 1 — — — Total Derivative Assets – Commodity Contracts $ 54 $ 8 $ 14 $ 8 $ 5 $ 2 $ 28 $ 2 Interest Rate Contracts Designated as Hedging Instruments Noncurrent $ 14 $ — $ — $ — $ — $ — $ — $ — Not Designated as Hedging Instruments Current 1 — 1 — 1 — — — Total Derivative Assets – Interest Rate Contracts $ 15 $ — $ 1 $ — $ 1 $ — $ — $ — Total Derivative Assets $ 69 $ 8 $ 15 $ 8 $ 6 $ 2 $ 28 $ 2 Derivative Liabilities 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 Commodity Contracts Not Designated as Hedging Instruments Current $ 29 $ 1 $ 11 $ 2 $ 9 $ — $ — $ 18 Noncurrent 113 1 7 1 — — — 105 Total Derivative Liabilities – Commodity Contracts $ 142 $ 2 $ 18 $ 3 $ 9 $ — $ — $ 123 Interest Rate Contracts Designated as Hedging Instruments Current $ 7 $ — $ — $ — $ — $ — $ — $ — Noncurrent 9 — — — — — — — Not Designated as Hedging Instruments Current 24 23 — — — 1 — — Noncurrent 9 — 4 4 — 4 — — Total Derivative Liabilities – Interest Rate Contracts $ 49 $ 23 $ 4 $ 4 $ — $ 5 $ — $ — Total Derivative Liabilities $ 191 $ 25 $ 22 $ 7 $ 9 $ 5 $ — $ 123 Derivative Assets December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Commodity Contracts Not Designated as Hedging Instruments Current $ 108 $ 23 $ 61 $ 35 $ 26 $ 4 $ 16 $ 3 Noncurrent 32 10 21 10 11 1 — — Total Derivative Assets – Commodity Contracts $ 140 $ 33 $ 82 $ 45 $ 37 $ 5 $ 16 $ 3 Interest Rate Contracts Designated as Hedging Instruments Noncurrent $ 19 $ — $ — $ — $ — $ — $ — $ — Not Designated as Hedging Instruments Current 3 — 3 1 2 — — — Total Derivative Assets – Interest Rate Contracts $ 22 $ — $ 3 $ 1 $ 2 $ — $ — $ — Total Derivative Assets $ 162 $ 33 $ 85 $ 46 $ 39 $ 5 $ 16 $ 3 Derivative Liabilities December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Commodity Contracts Not Designated as Hedging Instruments Current $ 43 $ — $ 12 $ — $ 12 $ — $ 2 $ 35 Noncurrent 166 1 7 1 — — — 152 Total Derivative Liabilities – Commodity Contracts $ 209 $ 1 $ 19 $ 1 $ 12 $ — $ 2 $ 187 Interest Rate Contracts Designated as Hedging Instruments Current $ 8 $ — $ — $ — $ — $ — $ — $ — Noncurrent 8 — — — — — — — Not Designated as Hedging Instruments — Current 1 — — — — 1 — — Noncurrent 26 15 6 6 — 5 — — Total Derivative Liabilities – Interest Rate Contracts $ 43 $ 15 $ 6 $ 6 $ — $ 6 $ — $ — Total Derivative Liabilities $ 252 $ 16 $ 25 $ 7 $ 12 $ 6 $ 2 $ 187 OFFSETTING ASSETS AND LIABILITIES The following tables present the line items on the 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, 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 $ 49 $ 6 $ 11 $ 5 $ 5 $ 2 $ 28 $ 2 Gross amounts offset (3 ) — (3 ) (1 ) (2 ) — — — Net amounts presented in Current Assets: Other $ 46 $ 6 $ 8 $ 4 $ 3 $ 2 $ 28 $ 2 Noncurrent Gross amounts recognized $ 20 $ 2 $ 4 $ 3 $ 1 $ — $ — $ — Gross amounts offset (2 ) (1 ) (1 ) (1 ) — — — — Net amounts presented in Other Noncurrent Assets: Other $ 18 $ 1 $ 3 $ 2 $ 1 $ — $ — $ — Derivative Liabilities 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 Current Gross amounts recognized $ 60 $ 24 $ 11 $ 2 $ 9 $ 1 $ — $ 18 Gross amounts offset (4 ) (1 ) (3 ) (1 ) (2 ) — — — Net amounts presented in Current Liabilities: Other $ 56 $ 23 $ 8 $ 1 $ 7 $ 1 $ — $ 18 Noncurrent Gross amounts recognized $ 131 $ 1 $ 11 $ 5 $ — $ 4 $ — $ 105 Gross amounts offset (2 ) (1 ) (1 ) (1 ) — — — — Net amounts presented in Other Noncurrent Liabilities: Other $ 129 $ — $ 10 $ 4 $ — $ 4 $ — $ 105 Derivative Assets December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Current Gross amounts recognized $ 111 $ 23 $ 64 $ 36 $ 28 $ 4 $ 16 $ 3 Gross amounts offset (11 ) — (11 ) — (11 ) — — — Net amounts presented in Current Assets: Other $ 100 $ 23 $ 53 $ 36 $ 17 $ 4 $ 16 $ 3 Noncurrent Gross amounts recognized $ 51 $ 10 $ 21 $ 10 $ 11 $ 1 $ — $ — Gross amounts offset (2 ) (1 ) (1 ) (1 ) — — — — Net amounts presented in Other Noncurrent Assets: Other $ 49 $ 9 $ 20 $ 9 $ 11 $ 1 $ — $ — Derivative Liabilities December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Current Gross amounts recognized $ 52 $ — $ 12 $ — $ 12 $ 1 $ 2 $ 35 Gross amounts offset (11 ) — (11 ) — (11 ) — — — Net amounts presented in Current Liabilities: Other $ 41 $ — $ 1 $ — $ 1 $ 1 $ 2 $ 35 Noncurrent Gross amounts recognized $ 200 $ 16 $ 13 $ 7 $ — $ 5 $ — $ 152 Gross amounts offset (2 ) (1 ) (1 ) (1 ) — — — — Net amounts presented in Other Noncurrent Liabilities: Other $ 198 $ 15 $ 12 $ 6 $ — $ 5 $ — $ 152 OBJECTIVE CREDIT CONTINGENT FEATURES Certain derivative contracts contain objective credit contingent features. These features include the requirement to post cash collateral or letters of credit if specific events occur, such as a credit rating downgrade below investment grade. The following tables show information with respect to derivative contracts that are in a net liability position and contain objective credit-risk-related payment provisions. September 30, 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 $ 40 $ 25 $ 15 $ 6 $ 9 Fair value of collateral already posted — — — — — Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered 40 25 15 6 9 December 31, 2016 Duke Duke Duke Duke Energy Progress Energy Energy (in millions) Energy Carolinas Energy Progress Florida Aggregate fair value of derivatives in a net liability position $ 34 $ 16 $ 18 $ 6 $ 12 Fair value of collateral already posted — — — — — Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered 34 16 18 6 12 The Duke Energy Registrants have elected to offset cash collateral and fair values of derivatives. For amounts to be netted, the derivative and cash collateral must be executed with the same counterparty under the same master netting arrangement.

Investments in Debt and Equity

Investments in Debt and Equity Securities	9 Months Ended
	Sep. 30, 2017
Investments, Debt and Equity Securities [Abstract]
Investments In Debt And Equity Securities	INVESTMENTS IN DEBT AND EQUITY SECURITIES The Duke Energy Registrants classify their investments in debt and equity securities as either trading or available-for-sale. TRADING SECURITIES Piedmont's investments in debt and equity securities held in rabbi trusts associated with certain deferred compensation plans are classified as trading securities. The fair value of these investments was $1 million and $5 million as of September 30, 2017 , and December 31, 2016 , respectively. AVAILABLE-FOR-SALE (AFS) SECURITIES All other investments in debt and equity securities are classified as AFS. Duke Energy’s available-for-sale securities are primarily comprised of investments held in (i) the nuclear decommissioning trust fund (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. Duke Energy classifies all other investments in debt and equity securities as long term, unless otherwise noted. Investment Trusts The investments within the NDTF investments and the Duke Energy Progress, Duke Energy Florida and Duke Energy Indiana grantor trusts (Investment Trusts) are managed by independent investment managers with discretion to buy, sell and invest pursuant to the objectives set forth by the trust agreements. The Duke Energy Registrants have limited oversight of the day-to-day management of these investments. As a result, the ability to hold investments in unrealized loss positions is outside the control of the Duke Energy Registrants. Accordingly, all unrealized losses associated with debt and equity securities within the Investment Trusts are considered other-than-temporary impairments (OTTIs) and are recognized immediately. Investments within the Investment Trusts generally qualify for regulatory accounting, and accordingly realized and unrealized gains and losses are deferred as a regulatory asset or liability. Substantially all amounts of the Duke Energy Registrants' gross unrealized holding losses as of September 30, 2017 , and December 31, 2016 , are considered OTTIs on investments within Investment Trusts that have been recognized immediately as a regulatory asset. Other AFS Securities Unrealized gains and losses on all other AFS securities are included in other comprehensive income until realized, unless it is determined the carrying value of an investment is other-than-temporarily impaired. 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, 2017 , and December 31, 2016 . 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 AFS securities. September 30, 2017 December 31, 2016 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 $ — $ — $ 129 $ — $ — $ 111 Equity securities 2,549 28 4,627 2,092 54 4,106 Corporate debt securities 16 2 600 10 8 528 Municipal bonds 5 2 334 3 10 331 U.S. government bonds 10 4 984 10 8 984 Other debt securities — 1 120 — 3 124 Total NDTF $ 2,580 $ 37 $ 6,794 $ 2,115 $ 83 $ 6,184 Other Investments Cash and cash equivalents $ — $ — $ 15 $ — $ — $ 25 Equity securities 52 — 115 38 — 104 Corporate debt securities 1 — 64 1 1 66 Municipal bonds 3 1 83 2 1 82 U.S. government bonds — — 44 — 1 51 Other debt securities — — 37 — 2 42 Total Other Investments $ 56 $ 1 $ 358 $ 41 $ 5 $ 370 Total Investments $ 2,636 $ 38 $ 7,152 $ 2,156 $ 88 $ 6,554 The table below summarizes the maturity date for debt securities. (in millions) September 30, 2017 Due in one year or less $ 92 Due after one through five years 584 Due after five through 10 years 514 Due after 10 years 1,076 Total $ 2,266 Realized gains and losses, which were determined on a specific identification basis, from sales of AFS securities were as follows. Three Months Ended Nine Months Ended September 30, September 30, (in millions) 2017 2016 2017 2016 Realized gains $ 37 $ 82 $ 170 $ 200 Realized losses 25 42 124 134 DUKE ENERGY CAROLINAS The following table presents the estimated fair value of investments in AFS securities. September 30, 2017 December 31, 2016 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 $ — $ — $ 34 $ — $ — $ 18 Equity securities 1,395 14 2,553 1,157 28 2,245 Corporate debt securities 9 2 395 5 6 354 Municipal bonds 1 — 52 1 2 67 U.S. government bonds 3 3 466 2 5 458 Other debt securities — 1 113 — 3 116 Total NDTF $ 1,408 $ 20 $ 3,613 $ 1,165 $ 44 $ 3,258 Other Investments Other debt securities — — — — 1 3 Total Investments $ 1,408 $ 20 $ 3,613 $ 1,165 $ 45 $ 3,261 The table below summarizes the maturity date for debt securities. (in millions) September 30, 2017 Due in one year or less $ 5 Due after one through five years 218 Due after five through 10 years 264 Due after 10 years 539 Total $ 1,026 Realized gains and losses, which were determined on a specific identification basis, from sales of AFS securities were as follows. Three Months Ended Nine Months Ended September 30, September 30, (in millions) 2017 2016 2017 2016 Realized gains $ 20 $ 58 $ 110 $ 125 Realized losses 13 28 76 84 PROGRESS ENERGY The following table presents the estimated fair value of investments in AFS securities. September 30, 2017 December 31, 2016 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 $ — $ — $ 95 $ — $ — $ 93 Equity securities 1,154 14 2,074 935 26 1,861 Corporate debt securities 7 — 205 5 2 174 Municipal bonds 4 2 282 2 8 264 U.S. government bonds 7 1 518 8 3 526 Other debt securities — — 7 — — 8 Total NDTF $ 1,172 $ 17 $ 3,181 $ 950 $ 39 $ 2,926 Other Investments Cash and cash equivalents $ — $ — $ 11 $ — $ — $ 21 Municipal bonds 3 — 47 2 — 44 Total Other Investments $ 3 $ — $ 58 $ 2 $ — $ 65 Total Investments $ 1,175 $ 17 $ 3,239 $ 952 $ 39 $ 2,991 The table below summarizes the maturity date for debt securities. (in millions) September 30, 2017 Due in one year or less $ 74 Due after one through five years 309 Due after five through 10 years 194 Due after 10 years 482 Total $ 1,059 Realized gains and losses, which were determined on a specific identification basis, from sales of AFS securities were as follows. Three Months Ended Nine Months Ended September 30, September 30, (in millions) 2017 2016 2017 2016 Realized gains $ 16 $ 21 $ 58 $ 71 Realized losses 12 13 47 49 DUKE ENERGY PROGRESS The following table presents the estimated fair value of investments in AFS securities. September 30, 2017 December 31, 2016 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 $ — $ — $ 46 $ — $ — $ 45 Equity securities 882 11 1,683 704 21 1,505 Corporate debt securities 5 — 144 4 1 120 Municipal bonds 4 2 281 2 8 263 U.S. government bonds 5 1 303 5 2 275 Other debt securities — — 4 — — 5 Total NDTF $ 896 $ 14 $ 2,461 $ 715 $ 32 $ 2,213 Other Investments Cash and cash equivalents $ — $ — $ 1 $ — $ — $ 1 Total Investments $ 896 $ 14 $ 2,462 $ 715 $ 32 $ 2,214 The table below summarizes the maturity date for debt securities. (in millions) September 30, 2017 Due in one year or less $ 16 Due after one through five years 209 Due after five through 10 years 136 Due after 10 years 371 Total $ 732 Realized gains and losses, which were determined on a specific identification basis, from sales of AFS securities were as follows. Three Months Ended Nine Months Ended September 30, September 30, (in millions) 2017 2016 2017 2016 Realized gains $ 14 $ 18 $ 49 $ 60 Realized losses 11 11 41 42 DUKE ENERGY FLORIDA The following table presents the estimated fair value of investments in AFS securities. September 30, 2017 December 31, 2016 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 $ — $ — $ 49 $ — $ — $ 48 Equity securities 272 3 391 231 5 356 Corporate debt securities 2 — 61 1 1 54 Municipal bonds — — 1 — — 1 U.S. government bonds 2 — 215 3 1 251 Other debt securities — — 3 — — 3 Total NDTF (a) $ 276 $ 3 $ 720 $ 235 $ 7 $ 713 Other Investments Cash and cash equivalents $ — $ — $ — $ — $ — $ 4 Municipal bonds 3 — 47 2 — 44 Total Other Investments $ 3 $ — $ 47 $ 2 $ — $ 48 Total Investments $ 279 $ 3 $ 767 $ 237 $ 7 $ 761 (a) During the nine months ended September 30, 2017 , Duke Energy Florida continued to receive reimbursements from the NDTF for costs related to ongoing decommissioning activity of the Crystal River Unit 3 nuclear plant. The table below summarizes the maturity date for debt securities. (in millions) September 30, 2017 Due in one year or less $ 58 Due after one through five years 100 Due after five through 10 years 58 Due after 10 years 111 Total $ 327 Realized gains and losses, which were determined on a specific identification basis, from sales of AFS securities were as follows. Three Months Ended Nine Months Ended September 30, September 30, (in millions) 2017 2016 2017 2016 Realized gains $ 2 $ 3 $ 9 $ 11 Realized losses 1 2 6 7 DUKE ENERGY INDIANA The following table presents the estimated fair value of investments in AFS securities. September 30, 2017 December 31, 2016 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 $ 44 $ — $ 91 $ 33 $ — $ 79 Corporate debt securities — — 3 — — 2 Municipal bonds — 1 28 — 1 28 U.S. government bonds — — — — — 1 Total Investments $ 44 $ 1 $ 122 $ 33 $ 1 $ 110 The table below summarizes the maturity date for debt securities. (in millions) September 30, 2017 Due in one year or less $ 4 Due after one through five years 12 Due after five through 10 years 8 Due after 10 years 7 Total $ 31 Realized gains and losses, which were determined on a specific identification basis, from sales of AFS securities were insignificant for the three and nine months ended September 30, 2017 , and 2016 .

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements	FAIR VALUE MEASUREMENTS Fair value is the exchange price to sell an asset or transfer a liability in an orderly transaction between market participants at the measurement date. The fair value definition focuses on an exit price versus the acquisition cost. Fair value measurements use market data or assumptions market participants would use in pricing the asset or liability, including assumptions about risk and the risks inherent in the inputs to the valuation technique. These inputs may be readily observable, corroborated by market data or generally unobservable. Valuation techniques maximize the use of observable inputs and minimize use of unobservable inputs. A midmarket pricing convention (the midpoint price between bid and ask prices) is permitted for use as a practical expedient. Fair value measurements are classified in three levels based on the fair value hierarchy: Level 1 – Unadjusted quoted prices in active markets for identical assets or liabilities that the reporting entity can access at the measurement date. An active market is one in which transactions for an asset or liability occur with sufficient frequency and volume to provide ongoing pricing information. Level 2 – A fair value measurement utilizing inputs other than quoted prices included in Level 1 that are observable, either directly or indirectly, for an asset or liability. Inputs include (i) quoted prices for similar assets or liabilities in active markets, (ii) quoted prices for identical or similar assets or liabilities in markets that are not active (iii) and 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 based on the fair value of the underlying investments but may not be readily redeemable at that fair value. Fair value accounting guidance permits entities to elect to measure certain financial instruments that are not required to be accounted for at fair value, such as equity method investments or the company’s own debt, at fair value. The Duke Energy Registrants have not elected to record any of these items at fair value. Transfers between levels represent assets or liabilities that were previously (i) categorized at a higher level for which the inputs to the estimate became less observable or (ii) classified at a lower level for which the inputs became more observable during the period. The Duke Energy Registrant’s policy is to recognize transfers between levels of the fair value hierarchy at the end of the period. There were no transfers between levels during the three and nine months ended September 30, 2017 , and 2016 . 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 (NYSE) 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 2 related to the acquisition of Piedmont in 2016. See Note 11 in Duke Energy's Annual Report on Form 10-K for the year ended December 31, 2016, 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 10 . See Note 11 for additional information related to investments by major security type for the Duke Energy Registrants. September 30, 2017 (in millions) Total Fair Value Level 1 Level 2 Level 3 Not Categorized NDTF equity securities $ 4,627 $ 4,549 $ — $ — $ 78 NDTF debt securities 2,167 617 1,550 — — Other trading and AFS equity securities 116 116 — — — Other AFS debt securities 243 59 184 — — Derivative assets 69 4 35 30 — Total assets 7,222 5,345 1,769 30 78 Derivative liabilities (191 ) — (68 ) (123 ) — Net assets (liabilities) $ 7,031 $ 5,345 $ 1,701 $ (93 ) $ 78 December 31, 2016 (in millions) Total Fair Value Level 1 Level 2 Level 3 Not Categorized NDTF equity securities $ 4,106 $ 4,029 $ — $ — $ 77 NDTF debt securities 2,078 632 1,446 — — Other trading and AFS equity securities 104 104 — — — Other trading and AFS debt securities 266 75 186 5 — Derivative assets 162 5 136 21 — Total assets 6,716 4,845 1,768 26 77 Derivative liabilities (252 ) (2 ) (63 ) (187 ) — Net assets (liabilities) $ 6,464 $ 4,843 $ 1,705 $ (161 ) $ 77 The following tables provide reconciliations of beginning and ending balances of assets and liabilities measured at fair value using Level 3 measurements. Amounts included in earnings for derivatives are primarily included in Cost of natural gas on the Duke Energy Registrants' 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, 2017 Three Months Ended September 30, 2016 (in millions) Investments Derivatives (net) Total Investments Derivatives (net) Total Balance at beginning of period $ — $ (91 ) $ (91 ) $ 4 $ 34 $ 38 Purchases, sales, issuances and settlements: Settlements — (12 ) (12 ) — (9 ) (9 ) Total gains (losses) included on the Condensed Consolidated Balance Sheet — 10 10 — (2 ) (2 ) Balance at end of period $ — $ (93 ) $ (93 ) $ 4 $ 23 $ 27 Nine Months Ended September 30, 2017 Nine Months Ended September 30, 2016 (in millions) Investments Derivatives (net) Total Investments Derivatives (net) Total Balance at beginning of period $ 5 $ (166 ) $ (161 ) $ 5 $ 10 $ 15 Total pretax realized or unrealized gains included in comprehensive income 1 — 1 — — — Purchases, sales, issuances and settlements: Purchases — 55 55 — 34 34 Sales (6 ) — (6 ) (1 ) — (1 ) Settlements — (30 ) (30 ) — (22 ) (22 ) Total gains included on the Condensed Consolidated Balance Sheet — 48 48 — 1 1 Balance at end of period $ — $ (93 ) $ (93 ) $ 4 $ 23 $ 27 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, 2017 (in millions) Total Fair Value Level 1 Level 2 Level 3 Not Categorized NDTF equity securities $ 2,553 $ 2,475 $ — $ — $ 78 NDTF debt securities 1,060 178 882 — — Derivative assets 8 — 8 — — Total assets 3,621 2,653 890 — 78 Derivative liabilities (25 ) — (25 ) — — Net assets $ 3,596 $ 2,653 $ 865 $ — $ 78 December 31, 2016 (in millions) Total Fair Value Level 1 Level 2 Level 3 Not Categorized NDTF equity securities $ 2,245 $ 2,168 $ — $ — $ 77 NDTF debt securities 1,013 178 835 — — Other AFS debt securities 3 — — 3 — Derivative assets 33 — 33 — — Total assets 3,294 2,346 868 3 77 Derivative liabilities (16 ) — (16 ) — — Net assets $ 3,278 $ 2,346 $ 852 $ 3 $ 77 The following table provides 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) 2017 2016 2017 2016 Balance at beginning of period $ — $ 3 $ 3 $ 3 Total pretax realized or unrealized gains included in comprehensive income — — 1 — Purchases, sales, issuances and settlements: Sales — — (4 ) — Balance at end of period $ — $ 3 $ — $ 3 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, 2017 December 31, 2016 (in millions) Total Fair Value Level 1 Level 2 Total Fair Value Level 1 Level 2 NDTF equity securities $ 2,074 $ 2,074 $ — $ 1,861 $ 1,861 $ — NDTF debt securities 1,107 439 668 1,065 454 611 Other AFS debt securities 58 11 47 65 21 44 Derivative assets 15 1 14 85 — 85 Total assets 3,254 2,525 729 3,076 2,336 740 Derivative liabilities (22 ) — (22 ) (25 ) — (25 ) Net assets $ 3,232 $ 2,525 $ 707 $ 3,051 $ 2,336 $ 715 DUKE ENERGY PROGRESS The following table provides recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets. September 30, 2017 December 31, 2016 (in millions) Total Fair Value Level 1 Level 2 Total Fair Value Level 1 Level 2 NDTF equity securities $ 1,683 $ 1,683 $ — $ 1,505 $ 1,505 $ — NDTF debt securities 778 231 547 708 207 501 Other AFS debt securities 1 1 — 1 1 — Derivative assets 8 1 7 46 — 46 Total assets 2,470 1,916 554 2,260 1,713 547 Derivative liabilities (7 ) — (7 ) (7 ) — (7 ) Net assets $ 2,463 $ 1,916 $ 547 $ 2,253 $ 1,713 $ 540 DUKE ENERGY FLORIDA The following table provides recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets. September 30, 2017 December 31, 2016 (in millions) Total Fair Value Level 1 Level 2 Total Fair Value Level 1 Level 2 NDTF equity securities $ 391 $ 391 $ — $ 356 $ 356 $ — NDTF debt securities 329 208 121 357 247 110 Other AFS debt securities 47 — 47 48 4 44 Derivative assets 6 — 6 39 — 39 Total assets 773 599 174 800 607 193 Derivative liabilities (9 ) — (9 ) (12 ) — (12 ) Net assets $ 764 $ 599 $ 165 $ 788 $ 607 $ 181 DUKE ENERGY OHIO The following table provides recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets. September 30, 2017 December 31, 2016 (in millions) Total Fair Value Level 2 Level 3 Total Fair Value Level 2 Level 3 Derivative assets $ 2 $ — $ 2 $ 5 $ — $ 5 Derivative liabilities (5 ) (5 ) — (6 ) (6 ) — Net (liabilities) assets $ (3 ) $ (5 ) $ 2 $ (1 ) $ (6 ) $ 5 The following table provides a reconciliation of beginning and ending balances of assets and liabilities measured at fair value using Level 3 measurements. Derivatives (net) Three Months Ended September 30, Nine Months Ended September 30, (in millions) 2017 2016 2017 2016 Balance at beginning of period $ 3 $ 5 $ 5 $ 3 Purchases, sales, issuances and settlements: Purchases — — 3 5 Settlements (1 ) (2 ) (3 ) (4 ) Total losses included on the Condensed Consolidated Balance Sheet — — (3 ) (1 ) Balance at end of period $ 2 $ 3 $ 2 $ 3 DUKE ENERGY INDIANA 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, 2017 December 31, 2016 (in millions) Total Fair Value Level 1 Level 2 Level 3 Total Fair Value Level 1 Level 2 Level 3 Other AFS equity securities $ 91 $ 91 $ — $ — $ 79 $ 79 $ — $ — Other AFS debt securities 31 — 31 — 31 — 31 — Derivative assets 28 — — 28 16 — — 16 Total assets 150 91 31 28 126 79 31 16 Derivative liabilities — — — — (2 ) (2 ) — — Net assets $ 150 $ 91 $ 31 $ 28 $ 124 $ 77 $ 31 $ 16 The following table provides a reconciliation of beginning and ending balances of assets and liabilities measured at fair value using Level 3 measurements. Derivatives (net) Three Months Ended September 30, Nine Months Ended September 30, (in millions) 2017 2016 2017 2016 Balance at beginning of period $ 51 $ 29 $ 16 $ 7 Purchases, sales, issuances and settlements: Purchases — — 52 29 Settlements (11 ) (7 ) (27 ) (18 ) Total (losses) gains included on the Condensed Consolidated Balance Sheet (12 ) (2 ) (13 ) 2 Balance at end of period $ 28 $ 20 $ 28 $ 20 PIEDMONT 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, 2017 December 31, 2016 (in millions) Total Fair Value Level 1 Level 3 Total Fair Value Level 1 Level 3 Other trading equity securities $ 1 $ 1 $ — $ 4 $ 4 $ — Other trading debt securities — — — 1 1 — Derivative assets 2 2 — 3 3 — Total assets 3 3 — 8 8 — Derivative liabilities (123 ) — (123 ) (187 ) — (187 ) Net (liabilities) assets $ (120 ) $ 3 $ (123 ) $ (179 ) $ 8 $ (187 ) The following table provides a reconciliation of beginning and ending balances of assets and liabilities measured at fair value using Level 3 measurements. Derivatives (net) Three Months Ended September 30, Nine Months Ended September 30, (in millions) 2017 2016 2017 2016 Balance at beginning of period $ (145 ) $ (190 ) $ (187 ) $ (149 ) Total gains (losses) and settlements 22 (5 ) 64 (46 ) Balance at end of period $ (123 ) $ (195 ) $ (123 ) $ (195 ) QUANTITATIVE INFORMATION ABOUT UNOBSERVABLE INPUTS The following tables include quantitative information about the Duke Energy Registrants' derivatives classified as Level 3. September 30, 2017 Fair Value Investment Type (in millions) Valuation Technique Unobservable Input Range Duke Energy Ohio Financial Transmission Rights (FTRs) $ 2 RTO auction pricing FTR price – per megawatt-hour (MWh) $ — - $ 1.08 Duke Energy Indiana FTRs 28 RTO auction pricing FTR price – per MWh (0.82 ) - 6.19 Piedmont Natural gas contracts (123 ) Discounted cash flow Forward natural gas curves – price per million British thermal unit (MMBtu) 2.12 - 3.36 Duke Energy Total Level 3 derivatives $ (93 ) December 31, 2016 Fair Value Investment Type (in millions) Valuation Technique Unobservable Input Range Duke Energy Ohio FTRs $ 5 RTO auction pricing FTR price – per MWh $ 0.77 - $ 3.52 Duke Energy Indiana FTRs 16 RTO auction pricing FTR price – per MWh (0.83 ) - 9.32 Piedmont Natural gas contracts (187 ) Discounted cash flow Forward natural gas curves – price per MMBtu 2.31 - 4.18 Duke Energy Total Level 3 derivatives $ (166 ) OTHER FAIR VALUE DISCLOSURES The fair value and book value of long-term debt, including current maturities, is summarized in the following table. Estimates determined are not necessarily indicative of amounts that could have been settled in current markets. Fair value of long-term debt uses Level 2 measurements. September 30, 2017 December 31, 2016 (in millions) Book Value Fair Value Book Value Fair Value Duke Energy $ 51,414 $ 53,985 $ 47,895 $ 49,161 Duke Energy Carolinas 9,525 10,653 9,603 10,494 Progress Energy 17,637 19,615 17,541 19,107 Duke Energy Progress 7,557 8,075 7,011 7,357 Duke Energy Florida 6,696 7,475 6,125 6,728 Duke Energy Ohio 2,067 2,242 1,884 2,020 Duke Energy Indiana 3,785 4,407 3,786 4,260 Piedmont 2,036 2,193 1,821 1,933 At both September 30, 2017 , and December 31, 2016 , fair value of cash and cash equivalents, accounts and notes receivable, accounts payable, notes payable and commercial paper, and nonrecourse notes payable of VIEs are not materially different from their carrying amounts because of the short-term nature of these instruments and/or because the stated rates approximate market rates.

Variable Interest Entities

Variable Interest Entities	9 Months Ended
	Sep. 30, 2017
Variable Interest Entities [Abstract]
Variable Interest Entities	VARIABLE INTEREST ENTITIES A VIE is an entity that is evaluated for consolidation using more than a simple analysis of voting control. The analysis to determine whether an entity is a VIE considers contracts with an entity, credit support for an entity, the adequacy of the equity investment of an entity and the relationship of voting power to the amount of equity invested in an entity. This analysis is performed either upon the creation of a legal entity or upon the occurrence of an event requiring 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, 2017 , and the year ended December 31, 2016 , 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 described above. Duke Energy Duke Energy Duke Energy Duke Energy Carolinas Progress Florida (in millions) CRC DERF DEPR DEFR Expiration date December 2018 December 2018 February 2019 April 2019 Credit facility amount $ 325 $ 425 $ 300 $ 225 Amounts borrowed at September 30, 2017 325 425 300 225 Amounts borrowed at December 31, 2016 325 425 300 225 Nuclear Asset-Recovery Bonds – DEFPF Duke Energy Florida Project Finance, LLC (DEFPF) is a bankruptcy remote, wholly owned special purpose subsidiary of Duke Energy Florida. DEFPF was formed in 2016 for the sole purpose of issuing nuclear asset-recovery bonds to finance Duke Energy Florida's unrecovered regulatory asset related to Crystal River Unit 3. In June 2016, DEFPF issued $ 1,294 million of senior secured bonds and used the proceeds to acquire nuclear asset-recovery property from Duke Energy Florida. The nuclear asset-recovery property acquired includes the right to impose, bill, collect and adjust a non-bypassable nuclear asset-recovery charge from all Duke Energy Florida retail customers until the bonds are paid in full and all financing costs have been recovered. The nuclear asset-recovery bonds are secured by the nuclear asset-recovery property, and cash collections from the nuclear asset-recovery charges are the sole source of funds to satisfy the debt obligation. The bondholders have no recourse to Duke Energy Florida. 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, 2017 December 31, 2016 Receivables of VIEs $ 6 $ 6 Current Assets: Regulatory assets 51 50 Current Assets: Other 20 53 Other Noncurrent Assets: Regulatory assets 1,101 1,142 Current Liabilities: Other 3 17 Current maturities of long-term debt 53 62 Long-Term Debt 1,164 1,217 Commercial Renewables Certain of Duke Energy’s renewable energy facilities are VIEs due to Duke Energy issuing guarantees for debt service and operations and maintenance reserves in support of debt financings. Assets are restricted and cannot be pledged as collateral or sold to third parties without prior approval of debt holders. The activities that most significantly impact the economic performance of these renewable energy facilities were decisions associated with siting, negotiating PPAs, engineering, procurement and construction and decisions associated with ongoing operations and maintenance-related activities. Duke Energy consolidates the entities as it is responsible for all of these decisions. The table below presents material balances reported on Duke Energy's Condensed Consolidated Balance Sheets related to renewables VIEs. (in millions) September 30, 2017 December 31, 2016 Current Assets: Other $ 399 $ 223 Property, plant and equipment, cost 3,923 3,419 Accumulated depreciation and amortization (556 ) (453 ) Current maturities of long-term debt 162 198 Long-Term Debt 1,780 1,097 Deferred income taxes 223 275 Other Noncurrent Liabilities: Other 247 252 NON-CONSOLIDATED VIEs The following tables summarize the impact of non-consolidated VIEs on the Condensed Consolidated Balance Sheets. September 30, 2017 Duke Energy Duke Duke Pipeline Commercial Other Energy Energy (in millions) Investments Renewables VIEs (a) Total Ohio Indiana Receivables from affiliated companies $ — $ — $ — $ — $ 46 $ 75 Investments in equity method unconsolidated affiliates 895 172 39 1,106 — — Other noncurrent assets 18 — — 18 — — Total assets $ 913 $ 172 $ 39 $ 1,124 $ 46 $ 75 Other current liabilities — — 3 3 — — Deferred income taxes 29 — — 29 — — Other noncurrent liabilities — — 12 12 — — Total liabilities $ 29 $ — $ 15 $ 44 $ — $ — Net assets $ 884 $ 172 $ 24 $ 1,080 $ 46 $ 75 (a) Duke Energy holds a 50 percent equity interest in Duke-American Transmission Company, LLC (DATC). As of December 31, 2016, DATC was considered a VIE due to having insufficient equity to finance its own activities without subordinated financial support. However, DATC has sufficient equity to finance its own activities as of September 30, 2017, and, therefore, is no longer considered a VIE. Duke Energy's investment in DATC was $45 million at September 30, 2017. December 31, 2016 Duke Energy Duke Duke Pipeline Commercial Other Energy Energy (in millions) Investments Renewables VIEs Total Ohio Indiana Piedmont (a) Receivables from affiliated companies $ — $ — $ — $ — $ 82 $ 101 $ — Investments in equity method unconsolidated affiliates 487 174 90 751 — — 139 Other noncurrent assets 12 — — 12 — — — Total assets $ 499 $ 174 $ 90 $ 763 $ 82 $ 101 $ 139 Other current liabilities — — 3 3 — — — Other noncurrent liabilities — — 13 13 — — 4 Total liabilities $ — $ — $ 16 $ 16 $ — $ — 4 Net assets $ 499 $ 174 $ 74 $ 747 $ 82 $ 101 $ 135 (a) In April 2017, Piedmont transferred its non-consolidated VIE investments to a wholly owned subsidiary of Duke Energy. See "Pipeline Investments" section below for additional detail. The Duke Energy Registrants are not aware of any situations where the maximum exposure to loss significantly exceeds the carrying values shown above except for the power purchase agreement with OVEC, which is discussed below, and various guarantees, some of which are reflected in the table above as Other noncurrent liabilities. For more information on various guarantees, refer to Note 5 . 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 2017 2016 ACP 47 % $ 595 $ 265 Sabal Trail 7.5 % 218 140 Constitution 24 % 82 82 Total $ 895 $ 487 At December 31, 2016, Piedmont had a 7 percent ownership interest in ACP and a 24 percent ownership interest in Constitution. In April 2017, Piedmont transferred its ownership interests in ACP and Constitution to a wholly owned subsidiary of Duke Energy at book value. In October 2017, ACP executed a $3.4 billion revolving credit facility with a stated maturity date of October 2021. Duke Energy entered into a guarantee agreement to support its share of the ACP revolving credit facility. Duke Energy's maximum exposure to loss under the terms of the guarantee is limited to 47 percent of the outstanding borrowings under the credit facility. Through October 2017, ACP has borrowed $570 million against the revolving credit facility. 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, including costs associated with its 2,256 MW of coal-fired generation capacity. Deterioration in the credit quality or bankruptcy of one or more parties to the ICPA could increase the costs of OVEC. In addition, certain proposed environmental rulemaking could result in future increased cost allocations. CRC See discussion under Consolidated VIEs for additional information related to CRC. Amounts included in Receivables from affiliated companies in the above table for Duke Energy Ohio and Duke Energy Indiana reflect their retained interest in receivables sold to CRC. These subordinated notes held by Duke Energy Ohio and Duke Energy Indiana are stated at fair value. Carrying values of retained interests are determined by allocating carrying value of the receivables between assets sold and interests retained based on relative fair value. The allocated bases of the subordinated notes are not materially different than their face value because (i) the receivables generally 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 2017 2016 2017 2016 Anticipated credit loss ratio 0.5 % 0.5 % 0.3 % 0.3 % Discount rate 2.0 % 1.5 % 2.0 % 1.5 % Receivable turnover rate 13.4 % 13.3 % 10.7 % 10.6 % The following table shows the gross and net receivables sold. Duke Energy Ohio Duke Energy Indiana (in millions) September 30, 2017 December 31, 2016 September 30, 2017 December 31, 2016 Receivables sold $ 209 $ 267 $ 304 $ 306 Less: Retained interests 46 82 75 101 Net receivables sold $ 163 $ 185 $ 229 $ 205 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) 2017 2016 2017 2016 2017 2016 2017 2016 Sales Receivables sold $ 438 $ 481 $ 1,392 $ 1,442 $ 720 $ 722 $ 2,047 $ 1,980 Loss recognized on sale 2 2 7 7 3 3 9 8 Cash flows Cash proceeds from receivables sold $ 434 $ 468 $ 1,421 $ 1,432 $ 713 $ 703 $ 2,064 $ 1,958 Collection fees received 1 1 1 1 — — 1 1 Return received on retained interests — 1 2 2 2 2 5 4 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 .

Common Stock

Common Stock	9 Months Ended
	Sep. 30, 2017
Earnings Per Share [Abstract]
Common Stock	COMMON STOCK Basic Earnings Per Share (EPS) is computed by dividing net income attributable to Duke Energy common stockholders, as adjusted for distributed and undistributed earnings allocated to participating securities, by the weighted average number of common shares outstanding during the period. Diluted EPS is computed by dividing net income attributable to Duke Energy common stockholders, as adjusted for distributed and undistributed earnings allocated to participating securities, by the diluted weighted average number of common shares outstanding during the period. Diluted EPS reflects the potential dilution that could occur if securities or other agreements to issue common 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) 2017 2016 2017 2016 Income from continuing operations attributable to Duke Energy common stockholders excluding impact of participating securities $ 954 $ 998 $ 2,356 $ 2,194 Weighted average shares outstanding – basic 700 689 700 689 Equity Forwards — 2 — 1 Weighted average shares outstanding – diluted 700 691 700 690 Earnings per share from continuing operations attributable to Duke Energy common stockholders Basic $ 1.36 $ 1.44 $ 3.37 $ 3.19 Diluted $ 1.36 $ 1.44 $ 3.37 $ 3.18 Potentially dilutive items excluded from the calculation (a) 2 2 2 2 Dividends declared per common share $ 0.89 $ 0.855 $ 2.60 $ 2.505 (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 Forwards In March 2016, Duke Energy marketed an equity offering of 10.6 million shares of common stock. In lieu of issuing equity at the time of the offering, Duke Energy entered into equity forward sale agreements with Barclays (the Equity Forwards). The Equity Forwards required Duke Energy to either physically settle the transactions by issuing 10.6 million shares, or net settle in whole or in part through the delivery or receipt of cash or shares. As of September 30, 2016, share dilution resulting from the agreements was determined under the treasury stock method. Duke Energy physically settled the Equity Forwards in full in October 2016 following the close of the Piedmont acquisition. See Note 2 for additional information related to the Piedmont acquisition.

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	STOCK-BASED COMPENSATION For employee awards, equity classified stock-based compensation cost is measured at the service inception date or the grant date, based on the estimated achievement of certain performance metrics or the fair value of the award, and is recognized as expense or capitalized as a component of property, plant and equipment over the requisite service period. Pretax stock-based compensation costs, the tax benefit associated with stock-based compensation expense and stock-based compensation costs capitalized are included in the following table. Three Months Ended Nine Months Ended September 30, September 30, (in millions) 2017 2016 2017 2016 Restricted stock unit awards $ 10 $ 8 $ 30 $ 25 Performance awards 7 4 20 14 Pretax stock-based compensation cost $ 17 $ 12 $ 50 $ 39 Tax benefit associated with stock-based compensation expense $ 6 $ 5 $ 18 $ 14 Stock-based compensation costs capitalized 1 — 2 2 Prior to Duke Energy acquiring Piedmont, Piedmont had an incentive compensation plan for eligible officers and other participants. Piedmont's total pretax stock-based compensation costs were approximately $2 million and $5 million for the three and nine months ended September 30, 2016 , respectively. The tax benefit associated with Piedmont's stock-based compensation expense for the three and nine months ended September 30, 2016 , was immaterial.

Employee Benefit Plans

Employee Benefit Plans	9 Months Ended
	Sep. 30, 2017
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 includes information related to the Duke Energy Registrants' contributions to its U.S. qualified defined benefit pension plans. Duke Duke Energy (in millions) Energy Ohio Piedmont Anticipated 2017 contributions $ 19 $ 4 $ 11 Contributions made during the nine months ended September 30, 2017 8 4 — Remaining estimated contributions to be made in 2017 $ 11 $ — $ 11 Duke Energy did not make any contributions to its U.S. qualified defined benefit pension plans during the nine months ended September 30, 2016. Net periodic benefit costs disclosed in the tables below represent the cost of the respective benefit plan for the periods presented. However, portions of the net periodic benefit costs disclosed in the tables below have been capitalized as a component of property, plant and equipment. Amounts presented in the tables below for the Subsidiary Registrants represent the amounts of pension and other post-retirement benefit costs allocated by Duke Energy for employees of the Subsidiary Registrants. Additionally, the Subsidiary Registrants are allocated their proportionate share of pension and post-retirement benefit costs for employees of Duke Energy’s shared services affiliate that provides support to the Subsidiary Registrants. These allocated amounts are included in the governance and shared service costs discussed in Note 9 . Duke Energy uses a December 31 measurement date for its defined benefit retirement plan assets and obligations. QUALIFIED PENSION PLANS The following tables include the components of net periodic pension costs for qualified pension plans. 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 Three Months Ended September 30, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Service cost $ 36 $ 12 $ 11 $ 6 $ 4 $ 1 $ 2 $ 3 Interest cost on projected benefit obligation 83 21 27 12 14 5 7 2 Expected return on plan assets (128 ) (35 ) (42 ) (21 ) (21 ) (6 ) (10 ) (6 ) Amortization of actuarial loss 33 8 14 6 7 1 3 2 Amortization of prior service credit (4 ) (2 ) (1 ) — (1 ) — — (1 ) Other 2 1 1 — 1 — — — Net periodic pension costs $ 22 $ 5 $ 10 $ 3 $ 4 $ 1 $ 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 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 Nine Months Ended September 30, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Service cost $ 109 $ 36 $ 32 $ 18 $ 14 $ 3 $ 6 $ 8 Interest cost on projected benefit obligation 249 64 80 37 42 15 21 7 Expected return on plan assets (386 ) (106 ) (126 ) (62 ) (63 ) (20 ) (31 ) (18 ) Amortization of actuarial loss 99 24 41 17 21 3 9 6 Amortization of prior service credit (12 ) (6 ) (3 ) (1 ) (1 ) — — (2 ) Other 6 2 2 1 1 — — — Net periodic pension costs $ 65 $ 14 $ 26 $ 10 $ 14 $ 1 $ 5 $ 1 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, 2017 Duke Duke Duke Duke Energy Progress Energy Energy (in millions) Energy Carolinas Energy Progress Florida Service cost $ — $ — $ — $ — $ — Interest cost on projected benefit obligation 4 — 1 1 1 Amortization of actuarial loss 2 — 1 — — Net periodic pension costs $ 6 $ — $ 2 $ 1 $ 1 Three Months Ended September 30, 2016 Duke Duke Duke Duke Energy Progress Energy Energy (in millions) Energy Carolinas Energy Progress Florida Service cost $ 1 $ — $ — $ — $ — Interest cost on projected benefit obligation 4 — 2 — — Amortization of actuarial loss 2 — 1 1 1 Amortization of prior service credit (1 ) — — — — Net periodic pension costs $ 6 $ — $ 3 $ 1 $ 1 Nine Months Ended September 30, 2017 Duke Duke Duke Duke Energy Progress Energy Energy (in millions) Energy Carolinas Energy Progress Florida Service cost $ — $ — $ — $ — $ — 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 Nine Months Ended September 30, 2016 Duke Duke Duke Duke Energy Progress Energy Energy (in millions) Energy Carolinas Energy Progress Florida Service cost $ 2 $ — $ — $ — $ — Interest cost on projected benefit obligation 11 1 4 1 1 Amortization of actuarial loss 6 — 2 1 1 Amortization of prior service credit (1 ) — — — — Net periodic pension costs $ 18 $ 1 $ 6 $ 2 $ 2 OTHER POST-RETIREMENT BENEFIT PLANS Duke Energy provides, and the Subsidiary Registrants participate in, some health care and life insurance benefits for retired employees on a contributory and non-contributory basis. The following tables include the components of net periodic other post-retirement benefit costs. 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 $ — Three Months Ended September 30, 2016 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 $ — $ — $ — $ — $ 1 Interest cost on accumulated post-retirement benefit obligation 9 2 4 2 3 — 1 — Expected return on plan assets (2 ) (2 ) (1 ) — — — — — Amortization of actuarial loss (gain) 2 — 5 3 2 (1 ) — — Amortization of prior service credit (35 ) (4 ) (26 ) (16 ) (8 ) — (1 ) — Net periodic other post-retirement benefit costs $ (26 ) $ (4 ) $ (17 ) $ (11 ) $ (3 ) $ (1 ) $ — $ 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 $ — Nine Months Ended September 30, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Service cost $ 2 $ — $ 1 $ — $ — $ — $ — $ 1 Interest cost on accumulated post-retirement benefit obligation 26 6 11 6 6 1 3 1 Expected return on plan assets (9 ) (6 ) (1 ) — — — (1 ) (1 ) Amortization of actuarial loss (gain) 5 (2 ) 16 9 7 (2 ) (1 ) — Amortization of prior service credit (106 ) (10 ) (77 ) (50 ) (26 ) — (1 ) — Net periodic other post-retirement benefit costs $ (82 ) $ (12 ) $ (50 ) $ (35 ) $ (13 ) $ (1 ) $ — $ 1 DEFINED CONTRIBUTION RETIREMENT PLANS EMPLOYEE SAVINGS PLANS Duke Energy sponsors, and the Subsidiary Registrants participate in, employee savings plans that cover substantially all U.S. employees. The following table presents 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, 2017 $ 43 $ 14 $ 12 $ 9 $ 4 $ 1 $ 2 $ 2 2016 39 13 12 8 3 1 2 2 Nine Months Ended September 30, 2017 $ 147 $ 49 $ 42 $ 30 $ 13 $ 3 $ 7 $ 5 2016 130 44 39 27 11 3 6 5 MONEY PURCHASE PENSION PLAN Duke Energy provides, and Piedmont participates in, the Money Purchase Pension (MPP) plan, which is a defined contribution pension plan that allows certain employees to direct investments and assume risk of investment returns. In January 2017, a $2 million contribution was made to the MPP plan.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Income Taxes	INCOME TAXES 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, 2017 2016 2017 2016 Duke Energy 27.6 % 34.0 % 30.4 % 31.7 % Duke Energy Carolinas 32.9 % 34.3 % 34.1 % 34.4 % Progress Energy 29.1 % 32.8 % 31.9 % 34.7 % Duke Energy Progress 31.7 % 31.4 % 32.4 % 33.5 % Duke Energy Florida 34.8 % 36.0 % 36.1 % 37.0 % Duke Energy Ohio 33.3 % 36.8 % 34.4 % 32.5 % Duke Energy Indiana 38.3 % 35.2 % 39.0 % 34.0 % Piedmont (a) 47.6 % 40.0 % 36.1 % 37.7 % (a) Piedmont is in a net loss position for the three months ended September 30, 2017, and 2016. The decrease in the effective tax rate (ETR) for Duke Energy for the three months ended September 30, 2017 , is primarily due to higher research credits, tax benefits of legal entity restructuring and prior year unfavorable impacts of finalizing federal tax audits. The decrease in the ETR for Duke Energy for the nine months ended September 30, 2017 , is primarily due to higher research credits, tax benefits of legal entity restructuring and higher production tax credits related to wind projects placed in service; partially offset by lower investment tax credits due to lower solar investments. The decrease in the ETR for Duke Energy Carolinas for the three months ended September 30, 2017 , is primarily due to the favorable impact of research credits, provision to return true ups, and lower North Carolina corporate tax rates. The decrease in the ETR for Progress Energy for the three and nine months ended September 30, 2017 , is primarily due to the favorable impact of research credits and lower North Carolina corporate tax rates. The decrease in the ETR for Duke Energy Progress for the nine months ended September 30, 2017 , is primarily due to the favorable impact of research credits and lower North Carolina corporate tax rates. The decrease in the ETR for Duke Energy Florida for the three months ended September 30, 2017 , is primarily due to the favorable impact of research credits. The decrease in the ETR for Duke Energy Ohio for the three months ended September 30, 2017 , is primarily due to the favorable impact of research credits. The increase in the ETR for Duke Energy Ohio for the nine months ended September 30, 2017 , is primarily due to an immaterial out of period adjustment in the prior year related to deferred tax balances associated with property, plant and equipment. The increase in the ETR for Duke Energy Indiana for the three months ended September 30, 2017 , is primarily due to state tax credits recorded in the prior year. The increase in the ETR for Duke Energy Indiana for the nine months ended September 30, 2017 , is primarily due to an immaterial out of period adjustment in the prior year related to deferred tax balances associated with property, plant and equipment. The increase in the ETR for Piedmont for the three months ended September 30, 2017 , is primarily due to favorable tax return true ups and lower North Carolina corporate tax rates in relation to pretax losses. The decrease in the ETR for Piedmont for the nine months ended September 30, 2017 , is primarily due to favorable tax return true ups and lower North Carolina corporate tax rates. TAXES ON FOREIGN EARNINGS As of December 31, 2015, Duke Energy's intention was to indefinitely reinvest any future undistributed foreign earnings earned after December 31, 2014. In February 2016, Duke Energy announced it had initiated a process to divest the International Disposal Group and, accordingly, no longer intended to indefinitely reinvest post-2014 undistributed foreign earnings. This change in the company's intent, combined with the extension of bonus depreciation by Congress in late 2015, allowed Duke Energy to more efficiently utilize foreign tax credits and reduce U.S. deferred tax liabilities associated with historical unremitted foreign earnings by approximately $95 million for the nine months ended September 30, 2016 . Due to the classification of the International Disposal Group as discontinued operations, income tax amounts related to the International Disposal Group's foreign earnings are presented within (Loss) Income from Discontinued Operations, net of tax on the Condensed Consolidated Statements of Operations. See Note 2 for additional information related to the sale of the International Disposal Group.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2017
Subsequent Events [Abstract]
Subsequent Events	SUBSEQUENT EVENTS For information on additional subsequent events related to business segments, regulatory matters, commitments and contingencies and VIEs, see Notes 3, 4, 5 and 13.

Organization and Basis of Pre27

Organization and Basis of Presentation (Policy)	9 Months Ended
	Sep. 30, 2017
Policy Text Block [Line Items]
Basis of Accounting	The results of operations of the International Disposal Group have been classified as Discontinued Operations on the Condensed Consolidated Statements of Operations. Duke Energy has elected to present cash flows of discontinued operations combined with cash flows of continuing operations. Unless otherwise noted, the notes to these Condensed Consolidated Financial Statements exclude amounts related to discontinued operations. Piedmont's results of operations and cash flows are included in the accompanying condensed consolidated financial statements of Duke Energy for the three and nine months ended September 30, 2017 , but not for the three and nine months ended September 30, 2016 , as Piedmont's earnings and cash flows are only included in Duke Energy's consolidated results subsequent to the acquisition date. BASIS OF PRESENTATION These Condensed Consolidated Financial Statements have been prepared in accordance with generally accepted accounting principles (GAAP) in the U.S. 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 in the U.S. 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 for the year ended December 31, 2016 , and the Consolidated Financial Statements and Notes in the Piedmont Annual Report on Form 10‑K for the year ended October 31, 2016. Effective November 1, 2016, Piedmont's fiscal year-end was changed from October 31 to December 31, the year-end of Duke Energy. A transition report was filed on Form 10-Q (Form 10-QT) as of December 31, 2016, for the transition period from November 1, 2016, to December 31, 2016. 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.
Unbilled Revenue	UNBILLED REVENUE Revenues on sales of electricity and natural gas are recognized when service is provided or the product is delivered. Unbilled revenues are recognized by applying customer billing rates to the estimated volumes of energy and 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, meter reading schedules, and the impact of weather normalization or margin decoupling mechanisms.
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.
Excise Taxes	EXCISE TAXES Certain excise taxes levied by state or local governments are required to be paid even if not collected from the customer. These taxes are recognized on a gross basis. Otherwise, excise taxes are accounted for on a net basis.
New Accounting Standards	NEW ACCOUNTING STANDARDS The new accounting standards adopted for 2017 and 2016 had no material impact on the presentation or results of operations, cash flows or financial position of the Duke Energy Registrants. 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, 2017 . Stock-Based Compensation and Income Taxes. In first quarter 2017, Duke Energy adopted Financial Accounting Standards Board (FASB) guidance, which revised the accounting for stock-based compensation and the associated income taxes. The adopted guidance changes certain aspects of accounting for stock-based payment awards to employees including the accounting for income taxes and classification on the Condensed Consolidated Statements of Cash Flows. The primary impact to Duke Energy as a result of implementing this guidance was a cumulative-effect adjustment to retained earnings for tax benefits not previously recognized and additional income tax expense for the nine months ended September 30, 2017 . See the Duke Energy Condensed Consolidated Statements of Changes in Equity for further information. Goodwill Impairment. In January 2017, the FASB issued revised guidance for the subsequent measurement of goodwill. Under the guidance, a company will recognize an impairment to goodwill for the amount by which a reporting unit's carrying value exceeds the reporting unit's fair value, not to exceed the amount of goodwill allocated to that reporting unit. Duke Energy early adopted this guidance for the 2017 annual goodwill impairment test. The following new Accounting Standards Updates (ASUs) have been issued, but have not yet been adopted by Duke Energy, as of September 30, 2017 . Retirement Benefits. In March 2017, the FASB issued revised accounting guidance for the presentation of net periodic costs related to benefit plans. Current GAAP permits the aggregation of all the components of net periodic costs on the income statement and does 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 must be included within Operating income within the same line as other compensation expenses. All other components of net periodic costs must be outside of Operating income. In addition, the updated guidance permits only the service cost component of net periodic costs to be capitalized to Inventory or Property, Plant and Equipment. This represents a change from current GAAP, which permits all components of net periodic costs to be capitalized. These amendments should be applied retrospectively for the presentation of the various components of net periodic costs and prospectively for the change in eligible costs to be capitalized. The guidance allows for a practical expedient that permits a company to use amounts disclosed in prior-period financial statements as the estimation basis for applying the retrospective presentation requirements. For Duke Energy, this guidance is effective for interim and annual periods beginning January 1, 2018. Duke Energy currently presents the total non-capitalized net periodic costs within Operation, maintenance and other on the Condensed Consolidated Statement of Operations. The adoption of this guidance will result in a retrospective change to reclassify the presentation of the non-service cost (benefit) components of net periodic costs to Other income and expenses. Duke Energy intends to utilize the practical expedient for retrospective presentation. The change in net periodic costs eligible for capitalization is applicable prospectively. Since Duke Energy’s service cost component is expected to be greater than the total net periodic costs, the change will result in increased capitalization of net periodic costs, higher Operation, maintenance and other and higher Other income and expenses. The resulting impact to Duke Energy is expected to be an immaterial increase in net income resulting from the limitation of eligible capitalization of net periodic costs to the service cost component, which is larger than the total net periodic costs. Revenue from Contracts with Customers . In May 2014, the FASB issued revised accounting guidance for revenue recognition from contracts with customers. The core principle of this guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The amendments in this update also require disclosure of sufficient information to allow users to understand the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. Duke Energy has identified material revenue streams, which served as the basis for accounting analysis and documentation of the impact of this guidance on revenue recognition. The accounting analysis included reviewing representative contracts and tariffs for each material revenue stream. Most of Duke Energy’s revenue is expected to be in scope of the new guidance. The majority of our sales, including energy provided to residential customers, are from tariff offerings that provide natural gas or electricity without a defined contractual term ("at-will"). For such arrangements, Duke Energy expects that the revenue from contracts with customers will be equivalent to the electricity or natural gas supplied and billed in that period (including estimated billings). As such, Duke Energy does not expect that there will be a significant shift in the timing or pattern of revenue recognition for such sales. Also included in the accounting analysis was the evaluation of certain long-term revenue streams including electric wholesale contracts and renewables power purchase agreements (PPAs) under this guidance. For such arrangements, Duke Energy does not expect material changes to the pattern of revenue recognition on the registrants . In addition, the power and utilities industry revenue recognition task force released several draft positions on specific industry issues in October 2017 for public comment. Duke Energy has been working closely with the industry task force and will be reviewing these updated positions to evaluate the impact, if any, on Duke Energy’s specific contracts and preliminary conclusions to date. The evaluation of other revenue streams is ongoing along with consideration of potential revisions to processes, policies and controls, primarily related to evaluating supplemental disclosures required as a result of adopting this guidance. Some revenue arrangements, such as alternative revenue programs and certain PPAs accounted for as leases, are excluded from the scope of this guidance and, therefore, will be accounted for and evaluated for separate presentation and disclosure under other relevant accounting guidance. Duke Energy continues to evaluate what information would be most useful for users of the financial statements, including information already provided in disclosures outside of the financial statement footnotes. These additional disclosures could include the disaggregation of revenues by geographic location, type of service, customer class or by duration of contract ("at-will" versus contracted revenue). Duke Energy intends to use the modified retrospective method of adoption effective January 1, 2018. Under the modified retrospective method of adoption, prior year reported results are not restated and a cumulative-effect adjustment, if applicable, is recorded to retained earnings at January 1, 2018, as if the standard had always been in effect. In addition, disclosures, if applicable, include a comparison to what would have been reported for 2018 under the previous revenue recognition rules to assist financial statement users in understanding how revenue recognition has changed as a result of this standard and to facilitate comparability with prior year reported results, which are not restated under the modified retrospective approach as described above. Duke Energy also plans to utilize certain practical expedients including applying this guidance to open contracts at the date of adoption and recognizing revenues for certain contracts under the invoice practical expedient, which allows revenue recognition to be consistent with invoiced amounts (including estimated billings) provided certain criteria are met, including consideration of whether the invoiced amounts reasonably represent the value provided to customers. While the adoption of this guidance, including the cumulative-effect adjustment, is not expected to have a material impact on either the timing or amount of revenues recognized in Duke Energy's financial statements, Duke Energy anticipates additional disclosures around the nature, amount, timing and uncertainty of our revenues and cash flows arising from contracts with customers and will continue to evaluate the requirements, as well as any additional clarifying guidance that may be issued. 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, although it can be early adopted. The guidance is applied using a modified retrospective approach. Duke Energy is currently evaluating the financial statement impact of adopting this standard and is continuing to monitor industry implementation issues, including easements, pole attachments and renewable PPAs. Other than an expected increase in assets and liabilities, the ultimate impact of the new standard has not yet been determined. Significant system enhancements, including additional processes and controls, may be required to facilitate the identification, tracking and reporting of potential leases based upon requirements of the new lease standard. Statement of Cash Flows. In November 2016, the FASB issued revised accounting guidance to reduce diversity in practice for the presentation and classification of restricted cash on the statement of cash flows. Under the updated guidance, restricted cash and restricted cash equivalents will be included within beginning-of-period and end-of-period cash and cash equivalents on the statement of cash flows. For Duke Energy, this guidance is effective for the interim and annual periods beginning January 1, 2018. The guidance will be applied using a retrospective transition method to each period presented. Upon adoption by Duke Energy, the revised guidance will result in a change to the amount of cash and cash equivalents and restricted cash explained when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. Prior to adoption, the Duke Energy Registrants reflect changes in non-current restricted cash within Cash Flows from Investing Activities and changes in current restricted cash within Cash Flows from Operating Activities on the Condensed Consolidated Statement of Cash Flows. Financial Instruments Classification and Measurement. In January 2016, the FASB issued revised accounting guidance for the classification and measurement of financial instruments. Changes in the fair value of all equity securities will be required to be recorded in net income. Current GAAP allows some changes in fair value for available-for-sale equity securities to be recorded in Accumulated other comprehensive income (AOCI). Additional disclosures will be required to present separately the financial assets and financial liabilities by measurement category and form of financial asset. An entity's equity investments that are accounted for under the equity method of accounting are not included within the scope of the new guidance. For Duke Energy, the revised accounting guidance is effective for interim and annual periods beginning January 1, 2018, by recording a cumulative-effect adjustment to retained earnings as of January 1, 2018. This guidance is expected to have minimal impact on the Duke Energy Registrant's Condensed Consolidated Statements of Operations and Comprehensive Income as changes in the fair value of most of the Duke Energy Registrants' available-for-sale equity securities are deferred as regulatory assets or liabilities pursuant to accounting guidance for regulated operations.
Acquisitions	The fair value of Piedmont's assets and liabilities was determined based on significant estimates and assumptions that are judgmental in nature, including the amount and timing of projected future cash flows, discount rates reflecting risk inherent in the future cash flows and market prices of long-term debt.
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.
Investments	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. As a result, the ability to hold investments in unrealized loss positions is outside the control of the Duke Energy Registrants. Accordingly, all unrealized losses associated with debt and equity securities within the Investment Trusts are considered other-than-temporary impairments (OTTIs) and are recognized immediately. Investments within the Investment Trusts generally qualify for regulatory accounting, and accordingly realized and unrealized gains and losses are deferred as a regulatory asset or liability.
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	For employee awards, equity classified stock-based compensation cost is measured at the service inception date or the grant date, based on the estimated achievement of certain performance metrics or the fair value of the award, and is recognized as expense or capitalized as a component of property, plant and equipment over the requisite service period.
Duke Energy Ohio [Member]
Policy Text Block [Line Items]
Unbilled Revenue	Additionally, Duke Energy Ohio and Duke Energy Indiana sell nearly all of their retail accounts receivable to an affiliate, Cinergy Receivables Company, LLC (CRC), on a revolving basis. These transfers of receivables are accounted for as sales and include receivables for unbilled revenues. Accordingly, the receivables sold are not reflected on the Condensed Consolidated Balance Sheets of Duke Energy Ohio and Duke Energy Indiana.
Duke Energy Indiana [Member]
Policy Text Block [Line Items]
Unbilled Revenue	Additionally, Duke Energy Ohio and Duke Energy Indiana sell nearly all of their retail accounts receivable to an affiliate, Cinergy Receivables Company, LLC (CRC), on a revolving basis. These transfers of receivables are accounted for as sales and include receivables for unbilled revenues. Accordingly, the receivables sold are not reflected on the Condensed Consolidated Balance Sheets of Duke Energy Ohio and Duke Energy Indiana.

Organization and Basis of Pre28

Organization and Basis of Presentation (Tables)	9 Months Ended
	Sep. 30, 2017
Organization And Basis Of Presentation [Line Items]
Schedule Of Unbilled Revenues With Restricted Receivables	Unbilled revenues are included within Receivables and Receivables of variable interest entities (VIEs) on the Condensed Consolidated Balance Sheets as shown in the following table. (in millions) September 30, 2017 December 31, 2016 Duke Energy $ 771 $ 831 Duke Energy Carolinas 307 313 Progress Energy 216 161 Duke Energy Progress 113 102 Duke Energy Florida 103 59 Duke Energy Ohio 2 2 Duke Energy Indiana 29 32 Piedmont 4 77
Schedule Of Net Income Amounts Attributable To Controlling Interests	For the three and nine months ended September 30, 2017 , the Loss from Discontinued Operations, net of tax on Duke Energy's Condensed Consolidated Statements of Operations is entirely attributable to controlling interests. The following table presents Net Income Attributable to Duke Energy Corporation for continuing operations and discontinued operations for the three and nine months ended September 30, 2016 . Three Months Ended Nine Months Ended (in millions) September 30, 2016 September 30, 2016 Income from Continuing Operations $ 1,001 $ 2,202 Income from Continuing Operations Attributable to Noncontrolling Interests 2 5 Income from Continuing Operations Attributable to Duke Energy Corporation $ 999 $ 2,197 Income from Discontinued Operations, net of tax $ 180 $ 190 Income from Discontinued Operations Attributable to Noncontrolling Interests, net of tax 3 8 Income from Discontinued Operations Attributable to Duke Energy Corporation, net of tax $ 177 $ 182 Net Income $ 1,181 $ 2,392 Net Income Attributable to Noncontrolling Interests 5 13 Net Income Attributable to Duke Energy Corporation $ 1,176 $ 2,379
Schedule of Utility Inventory	The components of inventory are presented in the tables below. 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 Materials and supplies $ 2,335 $ 767 $ 1,132 $ 780 $ 351 $ 83 $ 312 $ 2 Coal 581 197 231 130 101 17 136 — Natural gas, oil and other fuel 349 36 221 108 114 39 2 51 Total inventory $ 3,265 $ 1,000 $ 1,584 $ 1,018 $ 566 $ 139 $ 450 $ 53 December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Materials and supplies $ 2,374 $ 767 $ 1,167 $ 813 $ 354 $ 84 $ 312 $ 1 Coal 774 251 314 148 166 19 190 — Natural gas, oil and other fuel 374 37 236 115 121 34 2 65 Total inventory $ 3,522 $ 1,055 $ 1,717 $ 1,076 $ 641 $ 137 $ 504 $ 66
Schedule of Excise Taxes	Excise taxes accounted for on a gross basis as 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) 2017 2016 2017 2016 Duke Energy $ 107 $ 107 $ 289 $ 285 Duke Energy Carolinas 9 6 27 21 Progress Energy 67 65 168 161 Duke Energy Progress 5 4 14 13 Duke Energy Florida 62 61 154 148 Duke Energy Ohio 24 26 75 77 Duke Energy Indiana 6 10 16 26 Piedmont 1 1 3 2
Duke Energy Ohio [Member]
Organization And Basis Of Presentation [Line Items]
Schedule Of Unbilled Revenues With Restricted Receivables	These receivables for unbilled revenues are shown in the table below. (in millions) September 30, 2017 December 31, 2016 Duke Energy Ohio $ 70 $ 97 Duke Energy Indiana 119 123
Duke Energy Indiana [Member]
Organization And Basis Of Presentation [Line Items]
Schedule Of Unbilled Revenues With Restricted Receivables	These receivables for unbilled revenues are shown in the table below. (in millions) September 30, 2017 December 31, 2016 Duke Energy Ohio $ 70 $ 97 Duke Energy Indiana 119 123

Acquisitions and Dispositions (

Acquisitions and Dispositions (Tables)	9 Months Ended
	Sep. 30, 2017
Business Combinations [Abstract]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed	The purchase price allocation of the Piedmont acquisition is as follows: (in millions) Current assets $ 497 Property, plant and equipment, net 4,714 Goodwill 3,353 Other long-term assets 804 Total assets 9,368 Current liabilities, including current maturities of long-term debt 576 Long-term liabilities 1,790 Long-term debt 2,002 Total liabilities 4,368 Total purchase price $ 5,000
Business Acquisition, Pro Forma Information	This information has been presented for illustrative purposes only and is not necessarily indicative of the consolidated results of operations that would have been achieved or the future consolidated results of operations of Duke Energy. Three Months Ended Nine Months Ended (in millions) September 30, 2016 September 30, 2016 Operating Revenues $ 6,713 $ 17,927 Net Income Attributable to Duke Energy Corporation 1,180 2,552
Financial Statement Disclosures	The following table presents the results of the International Disposal Group, which are included in (Loss) Income from Discontinued Operations, net of tax in Duke Energy's Condensed Consolidated Statements of Operations. Interest expense directly associated with the International Disposal Group was allocated to discontinued operations. No interest from corporate level debt was allocated to discontinued operations. Three Months Ended Nine Months Ended (in millions) September 30, 2016 September 30, 2016 Operating Revenues $ 245 $ 761 Fuel used in electric generation and purchased power 60 177 Cost of natural gas 11 34 Operation, maintenance and other 85 240 Depreciation and amortization 18 62 Property and other taxes 1 6 Impairment charges (a) — 194 Loss on Sales of Other Assets and Other, net (3 ) (2 ) Other Income and Expenses, net 14 35 Interest Expense 19 63 Income before income taxes 62 18 Income tax expense (benefit) (b) 4 (48 ) Income from discontinued operations of the International Disposal Group 58 66 Income from discontinued operations of other businesses (c) 122 124 Income from Discontinued Operations, net of tax $ 180 $ 190 (a) In conjunction with the advancements of marketing efforts during 2016, Duke Energy performed recoverability tests of the long-lived asset groups of International Energy. As a result, Duke Energy determined the carrying value of certain assets in Central America was not fully recoverable and recorded a pretax impairment charge of $194 million . The charge represents the excess carrying value over the estimated fair value of the assets, which was based on a Level 3 Fair Value measurement that was primarily determined from the income approach using discounted cash flows but also considered market information obtained in 2016. (b) Includes an income tax benefit of $95 million for the nine months ended September 30, 2016, related to historical undistributed foreign earnings. See Note 17 for additional information. (c) Duke Energy recognized an income tax benefit of $122 million resulting from immaterial out of period deferred tax liability adjustments for the three and nine months ended September 30, 2016. The amount includes $34 million recorded at Duke Energy Ohio. Duke Energy has elected not to separately disclose discontinued operations on the Condensed Consolidated Statements of Cash Flows. The following table summarizes Duke Energy's cash flows from discontinued operations related to the International Disposal Group. Nine Months Ended (in millions) September 30, 2016 Cash flows provided by (used in): Operating activities $ 201 Investing activities (35 )

Business Segments (Tables)

Business Segments (Tables)	9 Months Ended
	Sep. 30, 2017
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, 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) (a)(b)(c) $ 1,020 $ 19 $ (49 ) $ 990 $ (34 ) $ — $ 956 Add back noncontrolling interests 1 Loss from discontinued operations, net of tax (2 ) Net income $ 955 Segment assets $ 118,323 $ 11,361 $ 4,216 $ 133,900 $ 2,240 $ 185 $ 136,325 Three Months Ended September 30, 2016 Electric Gas Total Utilities and Utilities and Commercial Reportable (in millions) Infrastructure Infrastructure Renewables Segments Other Eliminations Consolidated Unaffiliated revenues $ 6,332 $ 89 $ 139 $ 6,560 $ 16 $ — $ 6,576 Intersegment revenues 8 — — 8 16 (24 ) — Total revenues $ 6,340 $ 89 $ 139 $ 6,568 $ 32 $ (24 ) $ 6,576 Segment income (loss) (a)(c) $ 1,189 $ 15 $ (24 ) $ 1,180 $ (181 ) $ — $ 999 Add back noncontrolling interests 2 Income from discontinued operations, net of tax (d) 180 Net income $ 1,181 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) (a)(b)(c) $ 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 Nine Months Ended September 30, 2016 Electric Gas Total Utilities and Utilities and Commercial Reportable (in millions) Infrastructure Infrastructure Renewables Segments Other Eliminations Consolidated Unaffiliated revenues $ 16,406 $ 355 $ 365 $ 17,126 $ 40 $ — $ 17,166 Intersegment revenues 24 3 — 27 51 (78 ) — Total revenues $ 16,430 $ 358 $ 365 $ 17,153 $ 91 $ (78 ) $ 17,166 Segment income (loss) (a)(c) $ 2,557 $ 63 $ 13 $ 2,633 $ (436 ) $ — $ 2,197 Add back noncontrolling interests 5 Income from discontinued operations, net of tax (d) 190 Net income $ 2,392 (a) Other includes costs to achieve the Piedmont acquisition. See Notes 2 and 10 for additional information. (b) For the three and nine months ended September 30, 2017, Electric Utilities and Infrastructure includes an impairment charge related to the Florida settlement agreement. See Note 4 for additional information. (c) Commercial Renewables includes impairment charges related to certain wind projects. See discussion below. (d) For the three and nine months ended September 30, 2016, Income from Discontinued Operations includes an income tax benefit resulting from immaterial out of period deferred tax liability adjustments. See Note 2 for additional information. The following table summarizes the net (loss) income of Other for each of these entities. Three Months Ended Nine Months Ended September 30, September 30, (in millions) 2017 2016 2017 2016 Duke Energy Carolinas $ (6 ) $ (16 ) $ (18 ) $ (50 ) Progress Energy (32 ) (45 ) (120 ) (139 ) Duke Energy Progress (4 ) (10 ) (11 ) (26 ) Duke Energy Florida (2 ) (5 ) (7 ) (14 ) Duke Energy Indiana (2 ) (3 ) (5 ) (10 ) Piedmont (5 ) — (18 ) 7
Duke Energy Ohio [Member]
Segment Reporting Information [Line Items]
Business Segment Data	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 Segment assets $ 5,006 $ 2,708 $ 7,714 $ 51 $ 7,765 Three Months Ended September 30, 2016 Electric Gas Total Utilities and Utilities and Reportable (in millions) Infrastructure Infrastructure Segments Other Consolidated Total revenues $ 390 $ 89 $ 479 $ 10 $ 489 Segment income (loss) 52 12 64 (9 ) 55 Income from discontinued operations, net of tax (a) 34 Net income $ 89 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 Nine Months Ended September 30, 2016 Electric Gas Total Utilities and Utilities and Reportable (in millions) Infrastructure Infrastructure Segments Other Consolidated Total revenues $ 1,053 $ 358 $ 1,411 $ 22 $ 1,433 Segment income (loss) 107 57 164 (29 ) 135 Income from discontinued operations, net of tax (a) 36 Net income $ 171 (a) For the three and nine months ended September 30, 2016, Income from Discontinued Operations includes an income tax benefit resulting from immaterial out of period deferred tax liability adjustments. See Note 2 for additional information.

Regulatory Matters (Tables)

Regulatory Matters (Tables)	9 Months Ended
	Sep. 30, 2017
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. Dollar amounts in the table below are included in Net property, plant and equipment on the Condensed Consolidated Balance Sheets as of September 30, 2017 , and exclude capitalized asset retirement costs. Remaining Net Capacity Book Value (in MW) (in millions) Duke Energy Carolinas Allen Steam Station Units 1-3 (a) 585 $ 164 Progress Energy and Duke Energy Florida Crystal River Units 1 and 2 (b) 873 111 Duke Energy Indiana Gallagher Units 2 and 4 (c) 280 130 Total Duke Energy 1,738 $ 405 (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 will likely retire these coal units by 2018 to comply with environmental regulations. (c) Duke Energy Indiana committed to either retire or stop burning coal at Gallagher Units 2 and 4 by December 31, 2022, as part of the settlement of Edwardsport IGCC matters.

Commitments and Contingencies (

Commitments and Contingencies (Table)	9 Months Ended
	Sep. 30, 2017
Valuation and Qualifying Accounts Disclosure [Line Items]
Schedule of Additional Possible Losses in Excess of Recorded Environmental Reserves	Additional losses in excess of recorded reserves that could be incurred for the stages of investigation, remediation and monitoring for environmental sites that have been evaluated at this time are not material except as presented in the table below. (in millions) Duke Energy $ 58 Duke Energy Carolinas 20 Duke Energy Ohio 30 Duke Energy Indiana 3 Piedmont 2
Reserve for Environmental Costs [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Schedule of Legal Reserves	The following tables contain information regarding reserves for probable and estimable costs related to the various environmental sites. These reserves are recorded in Accounts Payable within Current Liabilities and Other within Other Noncurrent Liabilities on the Condensed Consolidated Balance Sheets. 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 Nine Months Ended September 30, 2016 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 $ 94 $ 10 $ 17 $ 3 $ 14 $ 54 $ 12 $ 1 Provisions/adjustments 34 5 5 2 3 6 20 — Cash reductions (12 ) (4 ) (6 ) (2 ) (4 ) (1 ) (2 ) — Balance at end of period $ 116 $ 11 $ 16 $ 3 $ 13 $ 59 $ 30 $ 1
Legal Reserve [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 discussed above related to the termination of an EPC contract. 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, 2017 December 31, 2016 Reserves for Legal Matters Duke Energy $ 83 $ 98 Duke Energy Carolinas 23 23 Progress Energy 56 59 Duke Energy Progress 13 14 Duke Energy Florida 28 28 Duke Energy Ohio — 4 Piedmont 2 2

Debt and Credit Facilities (Tab

Debt and Credit Facilities (Tables)	9 Months Ended
	Sep. 30, 2017
Debt Disclosure [Abstract]
Schedule of Long-term Debt Instruments	The following table summarizes significant debt issuances (in millions). Refer to the "Available Credit Facilities" section below regarding amounts issued under the Three Year Revolver and the Piedmont Term Loan facilities. Nine Months Ended September 30, 2017 Duke Duke Duke Duke Maturity Interest Duke Energy Energy Energy Energy Issuance Date Date Rate Energy (Parent) Progress Florida Ohio Unsecured Debt April 2017 (a) April 2025 3.364 % $ 420 $ 420 $ — $ — $ — June 2017 (b) June 2020 2.100 % 330 330 — — — August 2017 (c) August 2022 2.400 % 500 500 — — — August 2017 (c) August 2027 3.150 % 750 750 — — — August 2017 (c) August 2047 3.950 % 500 500 — — — Secured Debt February 2017 (d) June 2034 4.120 % 587 — — — — August 2017 (e) December 2036 4.110 % 233 — — — — First Mortgage Bonds January 2017 (f) January 2020 1.850 % 250 — — 250 — January 2017 (f) January 2027 3.200 % 650 — — 650 — March 2017 (g) June 2046 3.700 % 100 — — — 100 September 2017 (h) September 2020 1.500 % (i) 300 — 300 — — September 2017 (h) September 2047 3.600 % 500 — 500 — — Total issuances $ 5,120 $ 2,500 $ 800 $ 900 $ 100 (a) Proceeds were used to refinance $ 400 million of unsecured debt at maturity and to repay a portion of outstanding commercial paper. (b) Debt issued to repay a portion of outstanding commercial paper. (c) Debt issued to repay at maturity $700 million of unsecured debt, to repay outstanding commercial paper and for general corporate purposes. (d) Portfolio financing of four Texas and Oklahoma wind facilities. Secured by substantially all of the assets of these wind facilities and nonrecourse to Duke Energy. Proceeds were used to reimburse Duke Energy for a portion of previously funded construction expenditures. (e) Portfolio financing of eight solar facilities located in California, Colorado and New Mexico. Secured by substantially all of the assets of these solar facilities and nonrecourse to Duke Energy. Proceeds were used to reimburse Duke Energy for a portion of previously funded construction expenditures. (f) Debt issued to fund capital expenditures for ongoing construction and capital maintenance, to repay a $250 million aggregate principal amount of bonds at maturity and for general corporate purposes. (g) Proceeds were used to fund capital expenditures for ongoing construction, capital maintenance and for general corporate purposes. (h) Debt issued to repay at maturity a $200 million aggregate principal amount of bonds due November 2017, pay down intercompany short-term debt and for general corporate purposes, including capital expenditures. (i) Debt issuance has a floating interest rate. 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, 2017 Unsecured Debt Duke Energy (Parent) June 2018 6.250 % $ 250 Duke Energy (Parent) June 2018 2.100 % 500 First Mortgage Bonds Duke Energy Progress November 2017 1.516 % (b) 200 Duke Energy Carolinas January 2018 5.250 % 400 Duke Energy Carolinas April 2018 5.100 % 300 Duke Energy Florida June 2018 5.650 % 500 Other (a) 335 Current maturities of long-term debt $ 2,485 (a) Includes capital lease obligations, amortizing debt and small bullet maturities. (b) Debt issuance has a floating interest rate.
Schedule Of Line Of Credit Facilities	The table below includes the current borrowing sublimits and available capacity under the Master Credit Facility. September 30, 2017 Duke Duke Duke Duke Duke Duke Duke Energy Energy Energy Energy Energy Energy (in millions) Energy (Parent) Carolinas Progress Florida Ohio Indiana Piedmont Facility size (a) $ 8,000 $ 2,850 $ 1,350 $ 1,250 $ 1,000 $ 450 $ 600 $ 500 Reduction to backstop issuances Commercial paper (b) (1,569 ) (404 ) (636 ) (150 ) — (25 ) (150 ) (204 ) Outstanding letters of credit (60 ) (51 ) (4 ) (2 ) (1 ) — — (2 ) Tax-exempt bonds (81 ) — — — — — (81 ) — Coal ash set-aside (500 ) — (250 ) (250 ) — — — — Available capacity under the Master Credit Facility $ 5,790 $ 2,395 $ 460 $ 848 $ 999 $ 425 $ 369 $ 294 (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, 2017
Asset Retirement Obligation [Abstract]
Schedule of Asset Retirement Obligations	The following table presents the AROs recorded on the Condensed Consolidated Balance Sheets. 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 Decommissioning of Nuclear Power Facilities (a) $ 5,337 $ 1,916 $ 3,235 $ 2,536 $ 699 $ — $ — $ — Closure of Ash Impoundments 4,594 1,650 2,124 2,105 19 42 777 — Other 274 35 80 35 45 39 16 15 Total ARO $ 10,205 $ 3,601 $ 5,439 $ 4,676 $ 763 $ 81 $ 793 $ 15 Less: current portion 619 304 250 250 — 6 58 — Total noncurrent ARO $ 9,586 $ 3,297 $ 5,189 $ 4,426 $ 763 $ 75 $ 735 $ 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, 2016 (a) $ 10,611 $ 3,895 $ 5,475 $ 4,697 $ 778 $ 77 $ 866 $ 14 Accretion expense (b) 329 140 172 147 25 3 25 1 Liabilities settled (c) (430 ) (201 ) (193 ) (152 ) (41 ) (4 ) (26 ) (7 ) Liabilities incurred in the current year 48 5 — — — 7 27 7 Revisions in estimates of cash flows (d) (353 ) (238 ) (15 ) (16 ) 1 (2 ) (99 ) — Balance at September 30, 2017 $ 10,205 $ 3,601 $ 5,439 $ 4,676 $ 763 $ 81 $ 793 $ 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, 2017 , substantially all accretion expense relates to Duke Energy's regulated electric 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 favorable contract prices for closure of ash impoundments compared to original estimates.

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	9 Months Ended
	Sep. 30, 2017
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, 2017 , and December 31, 2016 . Electric Utilities Gas Utilities Commercial (in millions) and Infrastructure and Infrastructure Renewables Total Goodwill Balance at December 31, 2016 $ 17,379 $ 1,924 $ 122 $ 19,425 Accumulated impairment charges (a) — — (7 ) (7 ) Goodwill Balance at September 30, 2017 $ 17,379 $ 1,924 $ 115 $ 19,418 (a) Duke Energy evaluated the recoverability of goodwill in the third quarter of 2017 and recorded an impairment of $7 million related to the Energy Management Solutions reporting unit within the Commercial Renewables segment. The fair value of the reporting unit was determined based on the market approach, which estimates fair value based on market comparables within the energy technologies industry.

Related Party Transactions (Tab

Related Party Transactions (Tables)	9 Months Ended
	Sep. 30, 2017
Related Party Transaction [Line Items]
Schedule of Related Party Transactions, Other Revenue and Expense	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, 2017 Intercompany income tax receivable $ — $ 170 $ — $ 120 $ — $ — $ 89 Intercompany income tax payable 173 — 46 — 18 104 — December 31, 2016 Intercompany income tax receivable $ 1 $ — $ — $ 37 $ — $ — $ — Intercompany income tax payable — 37 90 — 1 3 38 The following table presents expenses for the three and nine months ended September 30, 2017 , and 2016 , 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 2017 2016 2017 2016 Cardinal Transportation Costs $ 2 $ 3 $ 6 $ 7 Pine Needle Natural Gas Storage Costs 2 3 6 8 Hardy Storage Natural Gas Storage Costs 2 2 7 7 Total $ 6 $ 8 $ 19 $ 22 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) 2017 2016 2017 2016 Duke Energy Carolinas Corporate governance and shared service expenses (a) $ 205 $ 204 $ 645 $ 620 Indemnification coverages (b) 5 5 17 16 JDA revenue (c) 9 10 42 21 JDA expense (c) 39 36 91 127 Intercompany natural gas purchases (d) 3 — 5 — Progress Energy Corporate governance and shared service expenses (a) $ 208 $ 182 $ 555 $ 515 Indemnification coverages (b) 10 9 29 25 JDA revenue (c) 39 36 91 127 JDA expense (c) 9 10 42 21 Intercompany natural gas purchases (d) 19 — 57 — Duke Energy Progress Corporate governance and shared service expenses (a) $ 114 $ 103 $ 321 $ 292 Indemnification coverages (b) 4 4 11 10 JDA revenue (c) 39 36 91 127 JDA expense (c) 9 10 42 21 Intercompany natural gas purchases (d) 19 — 57 — Duke Energy Florida Corporate governance and shared service expenses (a) $ 94 $ 79 $ 234 $ 223 Indemnification coverages (b) 6 5 18 15 Duke Energy Ohio Corporate governance and shared service expenses (a) $ 90 $ 89 $ 275 $ 261 Indemnification coverages (b) 1 1 3 4 Duke Energy Indiana Corporate governance and shared service expenses (a) $ 93 $ 96 $ 281 $ 279 Indemnification coverages (b) 2 2 6 6 Piedmont Corporate governance and shared service expenses (a) $ 10 $ — $ 25 $ — Indemnification coverages (b) 1 — 2 — Intercompany natural gas sales (d) 22 — 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 Regulated natural gas revenues, and Duke Energy Carolinas and Duke Energy Progress record the related purchases in Fuel used in electric generation and purchased power on their respective Condensed Consolidated Statements of Operations and Comprehensive Income. The amounts are not eliminated in accordance with rate-based accounting regulations. For the three and nine months ended September 30, 2016 , which was prior to the Piedmont acquisition, Piedmont recorded $19 million and $57 million , respectively, of natural gas sales with Duke Energy Progress and $1 million and $ 3 million , respectively, with Duke Energy Carolinas.

Derivatives and Hedging (Tables

Derivatives and Hedging (Tables)	9 Months Ended
	Sep. 30, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Notional Amounts of Outstanding Derivative Positions	The following table shows notional amounts of outstanding derivatives related to interest rate risk. September 30, 2017 Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Cash flow hedges (a) $ 703 $ — $ — $ — $ — $ — Undesignated contracts 927 400 500 250 250 27 Total notional amount $ 1,630 $ 400 $ 500 $ 250 $ 250 $ 27 December 31, 2016 Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Cash flow hedges (a) $ 750 $ — $ — $ — $ — $ — Undesignated contracts 927 400 500 250 250 27 Total notional amount $ 1,677 $ 400 $ 500 $ 250 $ 250 $ 27 (a) Duke Energy includes amounts related to consolidated VIEs of $703 million and $750 million as of September 30, 2017 , and December 31, 2016 , respectively. 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, 2017 Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy Carolinas Energy Progress Florida Indiana Piedmont Electricity (gigawatt-hours) 112 — — — — 112 — Natural gas (millions of dekatherms) 786 103 193 124 69 1 489 December 31, 2016 Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy Carolinas Energy Progress Florida Indiana Piedmont Electricity (gigawatt-hours) 147 — — — — 147 — Natural gas (millions of dekatherms) 890 91 269 118 151 1 529
Location And Fair Value Of Derivatives Recognized in the 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, 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 $ 48 $ 6 $ 10 $ 5 $ 4 $ 2 $ 28 $ 2 Noncurrent 6 2 4 3 1 — — — Total Derivative Assets – Commodity Contracts $ 54 $ 8 $ 14 $ 8 $ 5 $ 2 $ 28 $ 2 Interest Rate Contracts Designated as Hedging Instruments Noncurrent $ 14 $ — $ — $ — $ — $ — $ — $ — Not Designated as Hedging Instruments Current 1 — 1 — 1 — — — Total Derivative Assets – Interest Rate Contracts $ 15 $ — $ 1 $ — $ 1 $ — $ — $ — Total Derivative Assets $ 69 $ 8 $ 15 $ 8 $ 6 $ 2 $ 28 $ 2 Derivative Liabilities 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 Commodity Contracts Not Designated as Hedging Instruments Current $ 29 $ 1 $ 11 $ 2 $ 9 $ — $ — $ 18 Noncurrent 113 1 7 1 — — — 105 Total Derivative Liabilities – Commodity Contracts $ 142 $ 2 $ 18 $ 3 $ 9 $ — $ — $ 123 Interest Rate Contracts Designated as Hedging Instruments Current $ 7 $ — $ — $ — $ — $ — $ — $ — Noncurrent 9 — — — — — — — Not Designated as Hedging Instruments Current 24 23 — — — 1 — — Noncurrent 9 — 4 4 — 4 — — Total Derivative Liabilities – Interest Rate Contracts $ 49 $ 23 $ 4 $ 4 $ — $ 5 $ — $ — Total Derivative Liabilities $ 191 $ 25 $ 22 $ 7 $ 9 $ 5 $ — $ 123 Derivative Assets December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Commodity Contracts Not Designated as Hedging Instruments Current $ 108 $ 23 $ 61 $ 35 $ 26 $ 4 $ 16 $ 3 Noncurrent 32 10 21 10 11 1 — — Total Derivative Assets – Commodity Contracts $ 140 $ 33 $ 82 $ 45 $ 37 $ 5 $ 16 $ 3 Interest Rate Contracts Designated as Hedging Instruments Noncurrent $ 19 $ — $ — $ — $ — $ — $ — $ — Not Designated as Hedging Instruments Current 3 — 3 1 2 — — — Total Derivative Assets – Interest Rate Contracts $ 22 $ — $ 3 $ 1 $ 2 $ — $ — $ — Total Derivative Assets $ 162 $ 33 $ 85 $ 46 $ 39 $ 5 $ 16 $ 3 Derivative Liabilities December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Commodity Contracts Not Designated as Hedging Instruments Current $ 43 $ — $ 12 $ — $ 12 $ — $ 2 $ 35 Noncurrent 166 1 7 1 — — — 152 Total Derivative Liabilities – Commodity Contracts $ 209 $ 1 $ 19 $ 1 $ 12 $ — $ 2 $ 187 Interest Rate Contracts Designated as Hedging Instruments Current $ 8 $ — $ — $ — $ — $ — $ — $ — Noncurrent 8 — — — — — — — Not Designated as Hedging Instruments — Current 1 — — — — 1 — — Noncurrent 26 15 6 6 — 5 — — Total Derivative Liabilities – Interest Rate Contracts $ 43 $ 15 $ 6 $ 6 $ — $ 6 $ — $ — Total Derivative Liabilities $ 252 $ 16 $ 25 $ 7 $ 12 $ 6 $ 2 $ 187
Offsetting Assets	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, 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 $ 49 $ 6 $ 11 $ 5 $ 5 $ 2 $ 28 $ 2 Gross amounts offset (3 ) — (3 ) (1 ) (2 ) — — — Net amounts presented in Current Assets: Other $ 46 $ 6 $ 8 $ 4 $ 3 $ 2 $ 28 $ 2 Noncurrent Gross amounts recognized $ 20 $ 2 $ 4 $ 3 $ 1 $ — $ — $ — Gross amounts offset (2 ) (1 ) (1 ) (1 ) — — — — Net amounts presented in Other Noncurrent Assets: Other $ 18 $ 1 $ 3 $ 2 $ 1 $ — $ — $ — Derivative Assets December 31, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Current Gross amounts recognized $ 111 $ 23 $ 64 $ 36 $ 28 $ 4 $ 16 $ 3 Gross amounts offset (11 ) — (11 ) — (11 ) — — — Net amounts presented in Current Assets: Other $ 100 $ 23 $ 53 $ 36 $ 17 $ 4 $ 16 $ 3 Noncurrent Gross amounts recognized $ 51 $ 10 $ 21 $ 10 $ 11 $ 1 $ — $ — Gross amounts offset (2 ) (1 ) (1 ) (1 ) — — — — Net amounts presented in Other Noncurrent Assets: Other $ 49 $ 9 $ 20 $ 9 $ 11 $ 1 $ — $ —
Offsetting Liabilities	Derivative Liabilities 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 Current Gross amounts recognized $ 60 $ 24 $ 11 $ 2 $ 9 $ 1 $ — $ 18 Gross amounts offset (4 ) (1 ) (3 ) (1 ) (2 ) — — — Net amounts presented in Current Liabilities: Other $ 56 $ 23 $ 8 $ 1 $ 7 $ 1 $ — $ 18 Noncurrent Gross amounts recognized $ 131 $ 1 $ 11 $ 5 $ — $ 4 $ — $ 105 Gross amounts offset (2 ) (1 ) (1 ) (1 ) — — — — Net amounts presented in Other Noncurrent Liabilities: Other $ 129 $ — $ 10 $ 4 $ — $ 4 $ — $ 105 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, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Current Gross amounts recognized $ 52 $ — $ 12 $ — $ 12 $ 1 $ 2 $ 35 Gross amounts offset (11 ) — (11 ) — (11 ) — — — Net amounts presented in Current Liabilities: Other $ 41 $ — $ 1 $ — $ 1 $ 1 $ 2 $ 35 Noncurrent Gross amounts recognized $ 200 $ 16 $ 13 $ 7 $ — $ 5 $ — $ 152 Gross amounts offset (2 ) (1 ) (1 ) (1 ) — — — — Net amounts presented in Other Noncurrent Liabilities: Other $ 198 $ 15 $ 12 $ 6 $ — $ 5 $ — $ 152
Derivative 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, 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 $ 40 $ 25 $ 15 $ 6 $ 9 Fair value of collateral already posted — — — — — Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered 40 25 15 6 9 December 31, 2016 Duke Duke Duke Duke Energy Progress Energy Energy (in millions) Energy Carolinas Energy Progress Florida Aggregate fair value of derivatives in a net liability position $ 34 $ 16 $ 18 $ 6 $ 12 Fair value of collateral already posted — — — — — Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered 34 16 18 6 12 The Duke Energy Registrants have elected to offset cash collateral and fair values of derivatives. For amounts to be netted, the derivative and cash collateral must be executed with the same counterparty under the same master netting arrangement.

Investments in Debt and Equit38

Investments in Debt and Equity Securities (Tables)	9 Months Ended
	Sep. 30, 2017
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	The following table presents the estimated fair value of investments in AFS securities. September 30, 2017 December 31, 2016 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 $ — $ — $ 129 $ — $ — $ 111 Equity securities 2,549 28 4,627 2,092 54 4,106 Corporate debt securities 16 2 600 10 8 528 Municipal bonds 5 2 334 3 10 331 U.S. government bonds 10 4 984 10 8 984 Other debt securities — 1 120 — 3 124 Total NDTF $ 2,580 $ 37 $ 6,794 $ 2,115 $ 83 $ 6,184 Other Investments Cash and cash equivalents $ — $ — $ 15 $ — $ — $ 25 Equity securities 52 — 115 38 — 104 Corporate debt securities 1 — 64 1 1 66 Municipal bonds 3 1 83 2 1 82 U.S. government bonds — — 44 — 1 51 Other debt securities — — 37 — 2 42 Total Other Investments $ 56 $ 1 $ 358 $ 41 $ 5 $ 370 Total Investments $ 2,636 $ 38 $ 7,152 $ 2,156 $ 88 $ 6,554
Investments Classified by Contractual Maturity Date	The table below summarizes the maturity date for debt securities. (in millions) September 30, 2017 Due in one year or less $ 92 Due after one through five years 584 Due after five through 10 years 514 Due after 10 years 1,076 Total $ 2,266
Schedule of Realized Gain (Loss)	Realized gains and losses, which were determined on a specific identification basis, from sales of AFS securities were as follows. Three Months Ended Nine Months Ended September 30, September 30, (in millions) 2017 2016 2017 2016 Realized gains $ 37 $ 82 $ 170 $ 200 Realized losses 25 42 124 134
Duke Energy Carolinas [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	The following table presents the estimated fair value of investments in AFS securities. September 30, 2017 December 31, 2016 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 $ — $ — $ 34 $ — $ — $ 18 Equity securities 1,395 14 2,553 1,157 28 2,245 Corporate debt securities 9 2 395 5 6 354 Municipal bonds 1 — 52 1 2 67 U.S. government bonds 3 3 466 2 5 458 Other debt securities — 1 113 — 3 116 Total NDTF $ 1,408 $ 20 $ 3,613 $ 1,165 $ 44 $ 3,258 Other Investments Other debt securities — — — — 1 3 Total Investments $ 1,408 $ 20 $ 3,613 $ 1,165 $ 45 $ 3,261
Investments Classified by Contractual Maturity Date	The table below summarizes the maturity date for debt securities. (in millions) September 30, 2017 Due in one year or less $ 5 Due after one through five years 218 Due after five through 10 years 264 Due after 10 years 539 Total $ 1,026
Schedule of Realized Gain (Loss)	Realized gains and losses, which were determined on a specific identification basis, from sales of AFS securities were as follows. Three Months Ended Nine Months Ended September 30, September 30, (in millions) 2017 2016 2017 2016 Realized gains $ 20 $ 58 $ 110 $ 125 Realized losses 13 28 76 84
Progress Energy [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	The following table presents the estimated fair value of investments in AFS securities. September 30, 2017 December 31, 2016 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 $ — $ — $ 95 $ — $ — $ 93 Equity securities 1,154 14 2,074 935 26 1,861 Corporate debt securities 7 — 205 5 2 174 Municipal bonds 4 2 282 2 8 264 U.S. government bonds 7 1 518 8 3 526 Other debt securities — — 7 — — 8 Total NDTF $ 1,172 $ 17 $ 3,181 $ 950 $ 39 $ 2,926 Other Investments Cash and cash equivalents $ — $ — $ 11 $ — $ — $ 21 Municipal bonds 3 — 47 2 — 44 Total Other Investments $ 3 $ — $ 58 $ 2 $ — $ 65 Total Investments $ 1,175 $ 17 $ 3,239 $ 952 $ 39 $ 2,991
Investments Classified by Contractual Maturity Date	The table below summarizes the maturity date for debt securities. (in millions) September 30, 2017 Due in one year or less $ 74 Due after one through five years 309 Due after five through 10 years 194 Due after 10 years 482 Total $ 1,059
Schedule of Realized Gain (Loss)	Realized gains and losses, which were determined on a specific identification basis, from sales of AFS securities were as follows. Three Months Ended Nine Months Ended September 30, September 30, (in millions) 2017 2016 2017 2016 Realized gains $ 16 $ 21 $ 58 $ 71 Realized losses 12 13 47 49
Duke Energy Progress [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	The following table presents the estimated fair value of investments in AFS securities. September 30, 2017 December 31, 2016 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 $ — $ — $ 46 $ — $ — $ 45 Equity securities 882 11 1,683 704 21 1,505 Corporate debt securities 5 — 144 4 1 120 Municipal bonds 4 2 281 2 8 263 U.S. government bonds 5 1 303 5 2 275 Other debt securities — — 4 — — 5 Total NDTF $ 896 $ 14 $ 2,461 $ 715 $ 32 $ 2,213 Other Investments Cash and cash equivalents $ — $ — $ 1 $ — $ — $ 1 Total Investments $ 896 $ 14 $ 2,462 $ 715 $ 32 $ 2,214
Investments Classified by Contractual Maturity Date	The table below summarizes the maturity date for debt securities. (in millions) September 30, 2017 Due in one year or less $ 16 Due after one through five years 209 Due after five through 10 years 136 Due after 10 years 371 Total $ 732
Schedule of Realized Gain (Loss)	Realized gains and losses, which were determined on a specific identification basis, from sales of AFS securities were as follows. Three Months Ended Nine Months Ended September 30, September 30, (in millions) 2017 2016 2017 2016 Realized gains $ 14 $ 18 $ 49 $ 60 Realized losses 11 11 41 42
Duke Energy Florida [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	The following table presents the estimated fair value of investments in AFS securities. September 30, 2017 December 31, 2016 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 $ — $ — $ 49 $ — $ — $ 48 Equity securities 272 3 391 231 5 356 Corporate debt securities 2 — 61 1 1 54 Municipal bonds — — 1 — — 1 U.S. government bonds 2 — 215 3 1 251 Other debt securities — — 3 — — 3 Total NDTF (a) $ 276 $ 3 $ 720 $ 235 $ 7 $ 713 Other Investments Cash and cash equivalents $ — $ — $ — $ — $ — $ 4 Municipal bonds 3 — 47 2 — 44 Total Other Investments $ 3 $ — $ 47 $ 2 $ — $ 48 Total Investments $ 279 $ 3 $ 767 $ 237 $ 7 $ 761 (a) During the nine months ended September 30, 2017 , Duke Energy Florida continued to receive reimbursements from the NDTF for costs related to ongoing decommissioning activity of the Crystal River Unit 3 nuclear plant.
Investments Classified by Contractual Maturity Date	The table below summarizes the maturity date for debt securities. (in millions) September 30, 2017 Due in one year or less $ 58 Due after one through five years 100 Due after five through 10 years 58 Due after 10 years 111 Total $ 327
Schedule of Realized Gain (Loss)	Realized gains and losses, which were determined on a specific identification basis, from sales of AFS securities were as follows. Three Months Ended Nine Months Ended September 30, September 30, (in millions) 2017 2016 2017 2016 Realized gains $ 2 $ 3 $ 9 $ 11 Realized losses 1 2 6 7
Duke Energy Indiana [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	The following table presents the estimated fair value of investments in AFS securities. September 30, 2017 December 31, 2016 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 $ 44 $ — $ 91 $ 33 $ — $ 79 Corporate debt securities — — 3 — — 2 Municipal bonds — 1 28 — 1 28 U.S. government bonds — — — — — 1 Total Investments $ 44 $ 1 $ 122 $ 33 $ 1 $ 110
Investments Classified by Contractual Maturity Date	The table below summarizes the maturity date for debt securities. (in millions) September 30, 2017 Due in one year or less $ 4 Due after one through five years 12 Due after five through 10 years 8 Due after 10 years 7 Total $ 31

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurement Amounts For Assets And Liabilities	The following tables provide recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets. Derivative amounts in the tables below for all Duke Energy Registrants exclude cash collateral, which is disclosed in Note 10 . See Note 11 for additional information related to investments by major security type for the Duke Energy Registrants. September 30, 2017 (in millions) Total Fair Value Level 1 Level 2 Level 3 Not Categorized NDTF equity securities $ 4,627 $ 4,549 $ — $ — $ 78 NDTF debt securities 2,167 617 1,550 — — Other trading and AFS equity securities 116 116 — — — Other AFS debt securities 243 59 184 — — Derivative assets 69 4 35 30 — Total assets 7,222 5,345 1,769 30 78 Derivative liabilities (191 ) — (68 ) (123 ) — Net assets (liabilities) $ 7,031 $ 5,345 $ 1,701 $ (93 ) $ 78 December 31, 2016 (in millions) Total Fair Value Level 1 Level 2 Level 3 Not Categorized NDTF equity securities $ 4,106 $ 4,029 $ — $ — $ 77 NDTF debt securities 2,078 632 1,446 — — Other trading and AFS equity securities 104 104 — — — Other trading and AFS debt securities 266 75 186 5 — Derivative assets 162 5 136 21 — Total assets 6,716 4,845 1,768 26 77 Derivative liabilities (252 ) (2 ) (63 ) (187 ) — Net assets (liabilities) $ 6,464 $ 4,843 $ 1,705 $ (161 ) $ 77
Reconciliation Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Using Unobservable Inputs	The following tables provide reconciliations of beginning and ending balances of assets and liabilities measured at fair value using Level 3 measurements. Amounts included in earnings for derivatives are primarily included in Cost of natural gas on the Duke Energy Registrants' 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, 2017 Three Months Ended September 30, 2016 (in millions) Investments Derivatives (net) Total Investments Derivatives (net) Total Balance at beginning of period $ — $ (91 ) $ (91 ) $ 4 $ 34 $ 38 Purchases, sales, issuances and settlements: Settlements — (12 ) (12 ) — (9 ) (9 ) Total gains (losses) included on the Condensed Consolidated Balance Sheet — 10 10 — (2 ) (2 ) Balance at end of period $ — $ (93 ) $ (93 ) $ 4 $ 23 $ 27 Nine Months Ended September 30, 2017 Nine Months Ended September 30, 2016 (in millions) Investments Derivatives (net) Total Investments Derivatives (net) Total Balance at beginning of period $ 5 $ (166 ) $ (161 ) $ 5 $ 10 $ 15 Total pretax realized or unrealized gains included in comprehensive income 1 — 1 — — — Purchases, sales, issuances and settlements: Purchases — 55 55 — 34 34 Sales (6 ) — (6 ) (1 ) — (1 ) Settlements — (30 ) (30 ) — (22 ) (22 ) Total gains included on the Condensed Consolidated Balance Sheet — 48 48 — 1 1 Balance at end of period $ — $ (93 ) $ (93 ) $ 4 $ 23 $ 27
Quantitative Information Table - Level 3	The following tables include quantitative information about the Duke Energy Registrants' derivatives classified as Level 3. September 30, 2017 Fair Value Investment Type (in millions) Valuation Technique Unobservable Input Range Duke Energy Ohio Financial Transmission Rights (FTRs) $ 2 RTO auction pricing FTR price – per megawatt-hour (MWh) $ — - $ 1.08 Duke Energy Indiana FTRs 28 RTO auction pricing FTR price – per MWh (0.82 ) - 6.19 Piedmont Natural gas contracts (123 ) Discounted cash flow Forward natural gas curves – price per million British thermal unit (MMBtu) 2.12 - 3.36 Duke Energy Total Level 3 derivatives $ (93 ) December 31, 2016 Fair Value Investment Type (in millions) Valuation Technique Unobservable Input Range Duke Energy Ohio FTRs $ 5 RTO auction pricing FTR price – per MWh $ 0.77 - $ 3.52 Duke Energy Indiana FTRs 16 RTO auction pricing FTR price – per MWh (0.83 ) - 9.32 Piedmont Natural gas contracts (187 ) Discounted cash flow Forward natural gas curves – price per MMBtu 2.31 - 4.18 Duke Energy Total Level 3 derivatives $ (166 )
Schedule Of Long Term Debt Fair Value	The fair value and book value of long-term debt, including current maturities, is summarized in the following table. Estimates determined are not necessarily indicative of amounts that could have been settled in current markets. Fair value of long-term debt uses Level 2 measurements. September 30, 2017 December 31, 2016 (in millions) Book Value Fair Value Book Value Fair Value Duke Energy $ 51,414 $ 53,985 $ 47,895 $ 49,161 Duke Energy Carolinas 9,525 10,653 9,603 10,494 Progress Energy 17,637 19,615 17,541 19,107 Duke Energy Progress 7,557 8,075 7,011 7,357 Duke Energy Florida 6,696 7,475 6,125 6,728 Duke Energy Ohio 2,067 2,242 1,884 2,020 Duke Energy Indiana 3,785 4,407 3,786 4,260 Piedmont 2,036 2,193 1,821 1,933
Duke Energy Carolinas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurement Amounts For Assets And Liabilities	The following tables provide recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets. September 30, 2017 (in millions) Total Fair Value Level 1 Level 2 Level 3 Not Categorized NDTF equity securities $ 2,553 $ 2,475 $ — $ — $ 78 NDTF debt securities 1,060 178 882 — — Derivative assets 8 — 8 — — Total assets 3,621 2,653 890 — 78 Derivative liabilities (25 ) — (25 ) — — Net assets $ 3,596 $ 2,653 $ 865 $ — $ 78 December 31, 2016 (in millions) Total Fair Value Level 1 Level 2 Level 3 Not Categorized NDTF equity securities $ 2,245 $ 2,168 $ — $ — $ 77 NDTF debt securities 1,013 178 835 — — Other AFS debt securities 3 — — 3 — Derivative assets 33 — 33 — — Total assets 3,294 2,346 868 3 77 Derivative liabilities (16 ) — (16 ) — — Net assets $ 3,278 $ 2,346 $ 852 $ 3 $ 77
Reconciliation Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Using Unobservable Inputs	The following table provides 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) 2017 2016 2017 2016 Balance at beginning of period $ — $ 3 $ 3 $ 3 Total pretax realized or unrealized gains included in comprehensive income — — 1 — Purchases, sales, issuances and settlements: Sales — — (4 ) — Balance at end of period $ — $ 3 $ — $ 3
Progress Energy [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurement Amounts For Assets And Liabilities	The following tables provide recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets. September 30, 2017 December 31, 2016 (in millions) Total Fair Value Level 1 Level 2 Total Fair Value Level 1 Level 2 NDTF equity securities $ 2,074 $ 2,074 $ — $ 1,861 $ 1,861 $ — NDTF debt securities 1,107 439 668 1,065 454 611 Other AFS debt securities 58 11 47 65 21 44 Derivative assets 15 1 14 85 — 85 Total assets 3,254 2,525 729 3,076 2,336 740 Derivative liabilities (22 ) — (22 ) (25 ) — (25 ) Net assets $ 3,232 $ 2,525 $ 707 $ 3,051 $ 2,336 $ 715
Duke Energy Progress [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurement Amounts For Assets And Liabilities	The following table provides recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets. September 30, 2017 December 31, 2016 (in millions) Total Fair Value Level 1 Level 2 Total Fair Value Level 1 Level 2 NDTF equity securities $ 1,683 $ 1,683 $ — $ 1,505 $ 1,505 $ — NDTF debt securities 778 231 547 708 207 501 Other AFS debt securities 1 1 — 1 1 — Derivative assets 8 1 7 46 — 46 Total assets 2,470 1,916 554 2,260 1,713 547 Derivative liabilities (7 ) — (7 ) (7 ) — (7 ) Net assets $ 2,463 $ 1,916 $ 547 $ 2,253 $ 1,713 $ 540
Duke Energy Florida [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurement Amounts For Assets And Liabilities	The following table provides recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets. September 30, 2017 December 31, 2016 (in millions) Total Fair Value Level 1 Level 2 Total Fair Value Level 1 Level 2 NDTF equity securities $ 391 $ 391 $ — $ 356 $ 356 $ — NDTF debt securities 329 208 121 357 247 110 Other AFS debt securities 47 — 47 48 4 44 Derivative assets 6 — 6 39 — 39 Total assets 773 599 174 800 607 193 Derivative liabilities (9 ) — (9 ) (12 ) — (12 ) Net assets $ 764 $ 599 $ 165 $ 788 $ 607 $ 181
Duke Energy Ohio [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurement Amounts For Assets And Liabilities	The following table provides recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets. September 30, 2017 December 31, 2016 (in millions) Total Fair Value Level 2 Level 3 Total Fair Value Level 2 Level 3 Derivative assets $ 2 $ — $ 2 $ 5 $ — $ 5 Derivative liabilities (5 ) (5 ) — (6 ) (6 ) — Net (liabilities) assets $ (3 ) $ (5 ) $ 2 $ (1 ) $ (6 ) $ 5
Reconciliation Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Using Unobservable Inputs	The following table provides a reconciliation of beginning and ending balances of assets and liabilities measured at fair value using Level 3 measurements. Derivatives (net) Three Months Ended September 30, Nine Months Ended September 30, (in millions) 2017 2016 2017 2016 Balance at beginning of period $ 3 $ 5 $ 5 $ 3 Purchases, sales, issuances and settlements: Purchases — — 3 5 Settlements (1 ) (2 ) (3 ) (4 ) Total losses included on the Condensed Consolidated Balance Sheet — — (3 ) (1 ) Balance at end of period $ 2 $ 3 $ 2 $ 3
Duke Energy Indiana [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurement Amounts For Assets And Liabilities	The following table provides recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets. September 30, 2017 December 31, 2016 (in millions) Total Fair Value Level 1 Level 2 Level 3 Total Fair Value Level 1 Level 2 Level 3 Other AFS equity securities $ 91 $ 91 $ — $ — $ 79 $ 79 $ — $ — Other AFS debt securities 31 — 31 — 31 — 31 — Derivative assets 28 — — 28 16 — — 16 Total assets 150 91 31 28 126 79 31 16 Derivative liabilities — — — — (2 ) (2 ) — — Net assets $ 150 $ 91 $ 31 $ 28 $ 124 $ 77 $ 31 $ 16
Reconciliation Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Using Unobservable Inputs	The following table provides a reconciliation of beginning and ending balances of assets and liabilities measured at fair value using Level 3 measurements. Derivatives (net) Three Months Ended September 30, Nine Months Ended September 30, (in millions) 2017 2016 2017 2016 Balance at beginning of period $ 51 $ 29 $ 16 $ 7 Purchases, sales, issuances and settlements: Purchases — — 52 29 Settlements (11 ) (7 ) (27 ) (18 ) Total (losses) gains included on the Condensed Consolidated Balance Sheet (12 ) (2 ) (13 ) 2 Balance at end of period $ 28 $ 20 $ 28 $ 20
Piedmont Natural Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurement Amounts For Assets And Liabilities	The following table provides recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets. September 30, 2017 December 31, 2016 (in millions) Total Fair Value Level 1 Level 3 Total Fair Value Level 1 Level 3 Other trading equity securities $ 1 $ 1 $ — $ 4 $ 4 $ — Other trading debt securities — — — 1 1 — Derivative assets 2 2 — 3 3 — Total assets 3 3 — 8 8 — Derivative liabilities (123 ) — (123 ) (187 ) — (187 ) Net (liabilities) assets $ (120 ) $ 3 $ (123 ) $ (179 ) $ 8 $ (187 )
Reconciliation Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Using Unobservable Inputs	The following table provides a reconciliation of beginning and ending balances of assets and liabilities measured at fair value using Level 3 measurements. Derivatives (net) Three Months Ended September 30, Nine Months Ended September 30, (in millions) 2017 2016 2017 2016 Balance at beginning of period $ (145 ) $ (190 ) $ (187 ) $ (149 ) Total gains (losses) and settlements 22 (5 ) 64 (46 ) Balance at end of period $ (123 ) $ (195 ) $ (123 ) $ (195 )

Variable Interest Entities (Tab

Variable Interest Entities (Tables)	9 Months Ended
	Sep. 30, 2017
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 described above. Duke Energy Duke Energy Duke Energy Duke Energy Carolinas Progress Florida (in millions) CRC DERF DEPR DEFR Expiration date December 2018 December 2018 February 2019 April 2019 Credit facility amount $ 325 $ 425 $ 300 $ 225 Amounts borrowed at September 30, 2017 325 425 300 225 Amounts borrowed at December 31, 2016 325 425 300 225
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, 2017 Duke Energy Duke Duke Pipeline Commercial Other Energy Energy (in millions) Investments Renewables VIEs (a) Total Ohio Indiana Receivables from affiliated companies $ — $ — $ — $ — $ 46 $ 75 Investments in equity method unconsolidated affiliates 895 172 39 1,106 — — Other noncurrent assets 18 — — 18 — — Total assets $ 913 $ 172 $ 39 $ 1,124 $ 46 $ 75 Other current liabilities — — 3 3 — — Deferred income taxes 29 — — 29 — — Other noncurrent liabilities — — 12 12 — — Total liabilities $ 29 $ — $ 15 $ 44 $ — $ — Net assets $ 884 $ 172 $ 24 $ 1,080 $ 46 $ 75 (a) Duke Energy holds a 50 percent equity interest in Duke-American Transmission Company, LLC (DATC). As of December 31, 2016, DATC was considered a VIE due to having insufficient equity to finance its own activities without subordinated financial support. However, DATC has sufficient equity to finance its own activities as of September 30, 2017, and, therefore, is no longer considered a VIE. Duke Energy's investment in DATC was $45 million at September 30, 2017. December 31, 2016 Duke Energy Duke Duke Pipeline Commercial Other Energy Energy (in millions) Investments Renewables VIEs Total Ohio Indiana Piedmont (a) Receivables from affiliated companies $ — $ — $ — $ — $ 82 $ 101 $ — Investments in equity method unconsolidated affiliates 487 174 90 751 — — 139 Other noncurrent assets 12 — — 12 — — — Total assets $ 499 $ 174 $ 90 $ 763 $ 82 $ 101 $ 139 Other current liabilities — — 3 3 — — — Other noncurrent liabilities — — 13 13 — — 4 Total liabilities $ — $ — $ 16 $ 16 $ — $ — 4 Net assets $ 499 $ 174 $ 74 $ 747 $ 82 $ 101 $ 135 (a) In April 2017, Piedmont transferred its non-consolidated VIE investments to a wholly owned subsidiary of Duke Energy. See "Pipeline Investments" section below for additional detail.
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, 2017 December 31, 2016 Receivables of VIEs $ 6 $ 6 Current Assets: Regulatory assets 51 50 Current Assets: Other 20 53 Other Noncurrent Assets: Regulatory assets 1,101 1,142 Current Liabilities: Other 3 17 Current maturities of long-term debt 53 62 Long-Term Debt 1,164 1,217
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, 2017 December 31, 2016 Current Assets: Other $ 399 $ 223 Property, plant and equipment, cost 3,923 3,419 Accumulated depreciation and amortization (556 ) (453 ) Current maturities of long-term debt 162 198 Long-Term Debt 1,780 1,097 Deferred income taxes 223 275 Other Noncurrent Liabilities: Other 247 252
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 2017 2016 ACP 47 % $ 595 $ 265 Sabal Trail 7.5 % 218 140 Constitution 24 % 82 82 Total $ 895 $ 487
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 2017 2016 2017 2016 Anticipated credit loss ratio 0.5 % 0.5 % 0.3 % 0.3 % Discount rate 2.0 % 1.5 % 2.0 % 1.5 % Receivable turnover rate 13.4 % 13.3 % 10.7 % 10.6 % The following table shows the gross and net receivables sold. Duke Energy Ohio Duke Energy Indiana (in millions) September 30, 2017 December 31, 2016 September 30, 2017 December 31, 2016 Receivables sold $ 209 $ 267 $ 304 $ 306 Less: Retained interests 46 82 75 101 Net receivables sold $ 163 $ 185 $ 229 $ 205 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) 2017 2016 2017 2016 2017 2016 2017 2016 Sales Receivables sold $ 438 $ 481 $ 1,392 $ 1,442 $ 720 $ 722 $ 2,047 $ 1,980 Loss recognized on sale 2 2 7 7 3 3 9 8 Cash flows Cash proceeds from receivables sold $ 434 $ 468 $ 1,421 $ 1,432 $ 713 $ 703 $ 2,064 $ 1,958 Collection fees received 1 1 1 1 — — 1 1 Return received on retained interests — 1 2 2 2 2 5 4

Common Stock (Tables)

Common Stock (Tables)	9 Months Ended
	Sep. 30, 2017
Earnings Per Share [Abstract]
Schedule Of Earnings Per Share	The following table presents Duke Energy’s basic and diluted EPS calculations and reconciles the weighted average number of common 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) 2017 2016 2017 2016 Income from continuing operations attributable to Duke Energy common stockholders excluding impact of participating securities $ 954 $ 998 $ 2,356 $ 2,194 Weighted average shares outstanding – basic 700 689 700 689 Equity Forwards — 2 — 1 Weighted average shares outstanding – diluted 700 691 700 690 Earnings per share from continuing operations attributable to Duke Energy common stockholders Basic $ 1.36 $ 1.44 $ 3.37 $ 3.19 Diluted $ 1.36 $ 1.44 $ 3.37 $ 3.18 Potentially dilutive items excluded from the calculation (a) 2 2 2 2 Dividends declared per common share $ 0.89 $ 0.855 $ 2.60 $ 2.505 (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, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule Of Stock-Based Compensation Expense	Pretax stock-based compensation costs, the tax benefit associated with stock-based compensation expense and stock-based compensation costs capitalized are included in the following table. Three Months Ended Nine Months Ended September 30, September 30, (in millions) 2017 2016 2017 2016 Restricted stock unit awards $ 10 $ 8 $ 30 $ 25 Performance awards 7 4 20 14 Pretax stock-based compensation cost $ 17 $ 12 $ 50 $ 39 Tax benefit associated with stock-based compensation expense $ 6 $ 5 $ 18 $ 14 Stock-based compensation costs capitalized 1 — 2 2

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	9 Months Ended
	Sep. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan Disclosures	The following table presents 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, 2017 $ 43 $ 14 $ 12 $ 9 $ 4 $ 1 $ 2 $ 2 2016 39 13 12 8 3 1 2 2 Nine Months Ended September 30, 2017 $ 147 $ 49 $ 42 $ 30 $ 13 $ 3 $ 7 $ 5 2016 130 44 39 27 11 3 6 5
Qualified Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Schedule of Defined Benefit Plans Disclosures	The following table includes information related to the Duke Energy Registrants' contributions to its U.S. qualified defined benefit pension plans. Duke Duke Energy (in millions) Energy Ohio Piedmont Anticipated 2017 contributions $ 19 $ 4 $ 11 Contributions made during the nine months ended September 30, 2017 8 4 — Remaining estimated contributions to be made in 2017 $ 11 $ — $ 11
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, 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 Three Months Ended September 30, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Service cost $ 36 $ 12 $ 11 $ 6 $ 4 $ 1 $ 2 $ 3 Interest cost on projected benefit obligation 83 21 27 12 14 5 7 2 Expected return on plan assets (128 ) (35 ) (42 ) (21 ) (21 ) (6 ) (10 ) (6 ) Amortization of actuarial loss 33 8 14 6 7 1 3 2 Amortization of prior service credit (4 ) (2 ) (1 ) — (1 ) — — (1 ) Other 2 1 1 — 1 — — — Net periodic pension costs $ 22 $ 5 $ 10 $ 3 $ 4 $ 1 $ 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 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 Nine Months Ended September 30, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Service cost $ 109 $ 36 $ 32 $ 18 $ 14 $ 3 $ 6 $ 8 Interest cost on projected benefit obligation 249 64 80 37 42 15 21 7 Expected return on plan assets (386 ) (106 ) (126 ) (62 ) (63 ) (20 ) (31 ) (18 ) Amortization of actuarial loss 99 24 41 17 21 3 9 6 Amortization of prior service credit (12 ) (6 ) (3 ) (1 ) (1 ) — — (2 ) Other 6 2 2 1 1 — — — Net periodic pension costs $ 65 $ 14 $ 26 $ 10 $ 14 $ 1 $ 5 $ 1
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, 2017 Duke Duke Duke Duke Energy Progress Energy Energy (in millions) Energy Carolinas Energy Progress Florida Service cost $ — $ — $ — $ — $ — Interest cost on projected benefit obligation 4 — 1 1 1 Amortization of actuarial loss 2 — 1 — — Net periodic pension costs $ 6 $ — $ 2 $ 1 $ 1 Three Months Ended September 30, 2016 Duke Duke Duke Duke Energy Progress Energy Energy (in millions) Energy Carolinas Energy Progress Florida Service cost $ 1 $ — $ — $ — $ — Interest cost on projected benefit obligation 4 — 2 — — Amortization of actuarial loss 2 — 1 1 1 Amortization of prior service credit (1 ) — — — — Net periodic pension costs $ 6 $ — $ 3 $ 1 $ 1 Nine Months Ended September 30, 2017 Duke Duke Duke Duke Energy Progress Energy Energy (in millions) Energy Carolinas Energy Progress Florida Service cost $ — $ — $ — $ — $ — 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 Nine Months Ended September 30, 2016 Duke Duke Duke Duke Energy Progress Energy Energy (in millions) Energy Carolinas Energy Progress Florida Service cost $ 2 $ — $ — $ — $ — Interest cost on projected benefit obligation 11 1 4 1 1 Amortization of actuarial loss 6 — 2 1 1 Amortization of prior service credit (1 ) — — — — Net periodic pension costs $ 18 $ 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, 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 $ — Three Months Ended September 30, 2016 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 $ — $ — $ — $ — $ 1 Interest cost on accumulated post-retirement benefit obligation 9 2 4 2 3 — 1 — Expected return on plan assets (2 ) (2 ) (1 ) — — — — — Amortization of actuarial loss (gain) 2 — 5 3 2 (1 ) — — Amortization of prior service credit (35 ) (4 ) (26 ) (16 ) (8 ) — (1 ) — Net periodic other post-retirement benefit costs $ (26 ) $ (4 ) $ (17 ) $ (11 ) $ (3 ) $ (1 ) $ — $ 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 $ — Nine Months Ended September 30, 2016 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Service cost $ 2 $ — $ 1 $ — $ — $ — $ — $ 1 Interest cost on accumulated post-retirement benefit obligation 26 6 11 6 6 1 3 1 Expected return on plan assets (9 ) (6 ) (1 ) — — — (1 ) (1 ) Amortization of actuarial loss (gain) 5 (2 ) 16 9 7 (2 ) (1 ) — Amortization of prior service credit (106 ) (10 ) (77 ) (50 ) (26 ) — (1 ) — Net periodic other post-retirement benefit costs $ (82 ) $ (12 ) $ (50 ) $ (35 ) $ (13 ) $ (1 ) $ — $ 1

Income Taxes (Tables)

Income Taxes (Tables)	9 Months Ended
	Sep. 30, 2017
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, 2017 2016 2017 2016 Duke Energy 27.6 % 34.0 % 30.4 % 31.7 % Duke Energy Carolinas 32.9 % 34.3 % 34.1 % 34.4 % Progress Energy 29.1 % 32.8 % 31.9 % 34.7 % Duke Energy Progress 31.7 % 31.4 % 32.4 % 33.5 % Duke Energy Florida 34.8 % 36.0 % 36.1 % 37.0 % Duke Energy Ohio 33.3 % 36.8 % 34.4 % 32.5 % Duke Energy Indiana 38.3 % 35.2 % 39.0 % 34.0 % Piedmont (a) 47.6 % 40.0 % 36.1 % 37.7 % (a) Piedmont is in a net loss position for the three months ended September 30, 2017, and 2016.

Organization and Basis of Pre45

Organization and Basis of Presentation (Schedule of Unbilled Revenues with Restricted Receivables) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	$ 771	$ 831
Duke Energy Carolinas [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	307	313
Progress Energy [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	216	161
Duke Energy Progress [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	113	102
Duke Energy Florida [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	103	59
Duke Energy Ohio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	2	2
Duke Energy Indiana [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	29	32
Piedmont Natural Gas [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	4	77
Cinergy Receivables [Member] | Duke Energy Ohio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	70	97
Cinergy Receivables [Member] | Duke Energy Indiana [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	$ 119	$ 123

Organization and Basis of Pre46

Organization and Basis of Presentation (Schedule of Net Income Attributable to Noncontrolling Interest) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Schedule of Net Income Attributable to Noncontrolling Interest [Abstract]
Income From Continuing Operations	$ 957	$ 1,001	$ 2,365	$ 2,202
Income From Continuing Operations Attributable to Noncontrolling Interests	1	2	5	5
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	956	999	2,360	2,197
(Loss) Income From Discontinued Operations, net of tax	(2)	180	(4)	190
Income From Discontinued Operations Attributable to Noncontrolling Interests, net of tax		3		8
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent		177		182
Net Income	955	1,181	2,361	2,392
Net Income (Loss) Attributable to Noncontrolling Interests	1	5	5	13
Net Income (Loss) Attributable to Parent	$ 954	$ 1,176	$ 2,356	$ 2,379

Organization and Basis of Pre47

Organization and Basis of Presentation (Schedule of Inventory) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Public Utilities, Inventory [Line Items]
Inventory	$ 3,265	$ 3,522
Materials and supplies [Member]
Public Utilities, Inventory [Line Items]
Inventory	2,335	2,374
Coal [Member]
Public Utilities, Inventory [Line Items]
Inventory	581	774
Natural gas, oil and other fuel [Member]
Public Utilities, Inventory [Line Items]
Inventory	349	374
Duke Energy Carolinas [Member]
Public Utilities, Inventory [Line Items]
Inventory	1,000	1,055
Duke Energy Carolinas [Member] | Materials and supplies [Member]
Public Utilities, Inventory [Line Items]
Inventory	767	767
Duke Energy Carolinas [Member] | Coal [Member]
Public Utilities, Inventory [Line Items]
Inventory	197	251
Duke Energy Carolinas [Member] | Natural gas, oil and other fuel [Member]
Public Utilities, Inventory [Line Items]
Inventory	36	37
Progress Energy [Member]
Public Utilities, Inventory [Line Items]
Inventory	1,584	1,717
Progress Energy [Member] | Materials and supplies [Member]
Public Utilities, Inventory [Line Items]
Inventory	1,132	1,167
Progress Energy [Member] | Coal [Member]
Public Utilities, Inventory [Line Items]
Inventory	231	314
Progress Energy [Member] | Natural gas, oil and other fuel [Member]
Public Utilities, Inventory [Line Items]
Inventory	221	236
Duke Energy Progress [Member]
Public Utilities, Inventory [Line Items]
Inventory	1,018	1,076
Duke Energy Progress [Member] | Materials and supplies [Member]
Public Utilities, Inventory [Line Items]
Inventory	780	813
Duke Energy Progress [Member] | Coal [Member]
Public Utilities, Inventory [Line Items]
Inventory	130	148
Duke Energy Progress [Member] | Natural gas, oil and other fuel [Member]
Public Utilities, Inventory [Line Items]
Inventory	108	115
Duke Energy Florida [Member]
Public Utilities, Inventory [Line Items]
Inventory	566	641
Duke Energy Florida [Member] | Materials and supplies [Member]
Public Utilities, Inventory [Line Items]
Inventory	351	354
Duke Energy Florida [Member] | Coal [Member]
Public Utilities, Inventory [Line Items]
Inventory	101	166
Duke Energy Florida [Member] | Natural gas, oil and other fuel [Member]
Public Utilities, Inventory [Line Items]
Inventory	114	121
Duke Energy Ohio [Member]
Public Utilities, Inventory [Line Items]
Inventory	139	137
Duke Energy Ohio [Member] | Materials and supplies [Member]
Public Utilities, Inventory [Line Items]
Inventory	83	84
Duke Energy Ohio [Member] | Coal [Member]
Public Utilities, Inventory [Line Items]
Inventory	17	19
Duke Energy Ohio [Member] | Natural gas, oil and other fuel [Member]
Public Utilities, Inventory [Line Items]
Inventory	39	34
Duke Energy Indiana [Member]
Public Utilities, Inventory [Line Items]
Inventory	450	504
Duke Energy Indiana [Member] | Materials and supplies [Member]
Public Utilities, Inventory [Line Items]
Inventory	312	312
Duke Energy Indiana [Member] | Coal [Member]
Public Utilities, Inventory [Line Items]
Inventory	136	190
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	53	66
Piedmont Natural Gas [Member] | Materials and supplies [Member]
Public Utilities, Inventory [Line Items]
Inventory	2	1
Piedmont Natural Gas [Member] | Natural gas, oil and other fuel [Member]
Public Utilities, Inventory [Line Items]
Inventory	$ 51	$ 65

Organization and Basis of Pre48

Organization and Basis of Presentation (Schedule of Excise Taxes) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	$ 107	$ 107	$ 289	$ 285
Duke Energy Carolinas [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	9	6	27	21
Progress Energy [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	67	65	168	161
Duke Energy Progress [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	5	4	14	13
Duke Energy Florida [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	62	61	154	148
Duke Energy Ohio [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	24	26	75	77
Duke Energy Indiana [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	6	10	16	26
Piedmont Natural Gas [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	$ 1	$ 1	$ 3	$ 2

Acquisitions and Dispositions -

Acquisitions and Dispositions - Acquisitions (Narrative) (Details) - USD ($) $ in Millions	Oct. 03, 2016	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Business Acquisition [Line Items]
Asset Impairment Charges		$ 207	$ 10	$ 216	$ 14
Piedmont Natural Gas [Member]
Business Acquisition [Line Items]
Payments to acquire businesses	$ 5,000
Long-term debt assumed	$ 2,002
Unrealized Losses on Forward-Starting Interest Rate Swaps			22		190
Asset Impairment Charges		$ 7
Business Combination, After Tax Integration Related Costs			$ 41		$ 161

Acquisitions and Dispositions50

Acquisitions and Dispositions - Dispositions (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016USD ($)
DEI Brazil Holdings [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Enterprise Value	$ 1,200
DEI Latin American [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Enterprise Value	1,200
International Energy [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from Divestiture of Businesses	1,900
Obligations [Member] | International Energy [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Tax obligations	$ 78

Acquisitions and Dispositions51

Acquisitions and Dispositions (Purchase Price Allocation) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016	Oct. 03, 2016
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Goodwill	$ 19,418	$ 19,425
Piedmont Natural Gas [Member]
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Current assets			$ 497
Property, plant and equipment, net			4,714
Goodwill			3,353
Other long-term assets			804
Total assets			9,368
Current liabilities, including current maturities of long-term debt			576
Long-term liabilities			1,790
Long-term debt			2,002
Total liabilities			4,368
Total purchase price			$ 5,000

Acquisitions and Dispositions52

Acquisitions and Dispositions (Pro Forma Information) (Details) - Piedmont Natural Gas [Member] - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2016
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Operating Revenues	$ 6,713	$ 17,927
Net income attributable to Duke Energy Corporation	$ 1,180	$ 2,552

Acquisitions and Dispositions53

Acquisitions and Dispositions (Discontinued Operations) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income From Discontinued Operations, net of tax	$ (2)	$ 180	$ (4)	$ 190
International Energy [Member] | Discontinued Operations, Disposed of by Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Operating Revenues		245		761
Fuel used in electric generation and purchased power		60		177
Cost of natural gas		11		34
Operation, maintenance and other		85		240
Deprecation and amortization		18		62
Property and other taxes		1		6
Impairment Charges		0		194
Gains on Sales of Other Assets and Other, net		(3)		(2)
Other Income and Expenses, net		14		35
Interest Expense		19		63
Income before income taxes		62		18
Income tax expense (benefit)		4		(48)
Income From Discontinued Operations, net of tax		58		66
Other Disposal Groups [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income tax expense (benefit)		(122)		(122)
Income From Discontinued Operations, net of tax		122		124
Previously Remitted Earnings [Member] | International Energy [Member] | Discontinued Operations, Disposed of by Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income tax expense (benefit)				(95)
Duke Energy Ohio [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income From Discontinued Operations, net of tax	$ (1)	34	$ (1)	36
Duke Energy Ohio [Member] | Midwest Generation Business [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income tax expense (benefit)		$ (34)		$ (34)

Acquisitions and Dispositions54

Acquisitions and Dispositions (Cash Flow Statement) (Details) - International Energy [Member] $ in Millions	9 Months Ended
	Sep. 30, 2016USD ($)
Operating Activities	$ 201
Investing Activities	$ (35)

Business Segments (Narrative) (

Business Segments (Narrative) (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)segment	Sep. 30, 2016USD ($)	Oct. 31, 2017	Oct. 02, 2016
Segment Reporting Information [Line Items]
Impairment charges	$ 207	$ 10	$ 216	$ 14
Net income	954	1,176	2,356	2,379
Interest Expense	498	464	$ 1,475	1,431
Duke Energy Carolinas [Member]
Segment Reporting Information [Line Items]
Number of Reportable Segments | segment			1
Net income	466	494	$ 1,009	1,026
Interest Expense	108	102	314	316
Progress Energy [Member]
Segment Reporting Information [Line Items]
Impairment charges	135	1	$ 137	4
Number of Reportable Segments | segment			1
Net income	341	446	$ 814	927
Interest Expense	193	177	$ 595	497
Duke Energy Progress [Member]
Segment Reporting Information [Line Items]
Impairment charges		1		1
Number of Reportable Segments | segment			1
Net income	246	271	$ 547	539
Interest Expense	65	61	217	188
Duke Energy Florida [Member]
Segment Reporting Information [Line Items]
Impairment charges	135	1	$ 137	4
Number of Reportable Segments | segment			1
Net income	120	206	$ 368	487
Interest Expense	71	62	211	143
Duke Energy Ohio [Member]
Segment Reporting Information [Line Items]
Impairment charges			$ 1
Number of Reportable Segments | segment			2
Net income	55	89	$ 127	171
Interest Expense	22	22	$ 67	63
Duke Energy Indiana [Member]
Segment Reporting Information [Line Items]
Impairment charges		8		8
Number of Reportable Segments | segment			1
Net income	121	129	$ 318	309
Interest Expense	44	45	132	136
Piedmont Natural Gas [Member]
Segment Reporting Information [Line Items]
Impairment charges			$ 7
Number of Reportable Segments | segment			1
Net income	(11)	(12)	$ 76	94
Interest Expense	20	17	59	50
Commercial Renewables [Member]
Segment Reporting Information [Line Items]
Impairment charges	69		69
Equity Method Investment, Other than Temporary Impairment		71		71
Other [Member] | Progress Energy [Member]
Segment Reporting Information [Line Items]
Interest Expense	$ 56	55	$ 167	166
National Methanol Company [Member] | Other [Member]
Segment Reporting Information [Line Items]
Equity Method Investment, Ownership Percentage	25.00%		25.00%
National Methanol Company [Member] | Other [Member] | Subsequent Event [Member]
Segment Reporting Information [Line Items]
Equity Method Investment, Ownership Percentage					17.50%
SouthStar [Member] | Piedmont Natural Gas [Member]
Segment Reporting Information [Line Items]
Equity Method Investment, Ownership Percentage						15.00%
Net income		$ 2		$ 12

Business Segments (Business Seg

Business Segments (Business Segment Data) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Segment Reporting Information [Line Items]
Operating revenues	$ 6,482	$ 6,576	$ 17,766	$ 17,166
Segment income	956	999	2,360	2,197
Add back noncontrolling interests	1	2	5	5
(Loss) Income From Discontinued Operations, net of tax	(2)	180	(4)	190
Net income	955	1,181	2,361	2,392
Net income	954	1,176	2,356	2,379
Segment assets	136,325		136,325		$ 132,761
Electric Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Operating revenues	6,129	6,340	16,234	16,430
Gas Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Operating revenues	272	89	1,243	358
Commercial Renewables [Member]
Segment Reporting Information [Line Items]
Operating revenues	95	139	333	365
Other [Member]
Segment Reporting Information [Line Items]
Operating revenues	35	32	103	91
Total Reportable Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	6,496	6,568	17,810	17,153
Operating Segments [Member] | Electric Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Operating revenues	6,122	6,332	16,211	16,406
Segment income	1,020	1,189	2,384	2,557
Segment assets	118,323		118,323
Operating Segments [Member] | Gas Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Operating revenues	249	89	1,175	355
Segment income	19	15	179	63
Segment assets	11,361		11,361
Operating Segments [Member] | Commercial Renewables [Member]
Segment Reporting Information [Line Items]
Operating revenues	95	139	333	365
Segment income	(49)	(24)	2	13
Segment assets	4,216		4,216
Operating Segments [Member] | Total Reportable Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	6,466	6,560	17,719	17,126
Segment income	990	1,180	2,565	2,633
Segment assets	133,900		133,900
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues	(49)	(24)	(147)	(78)
Segment assets	185		185
Intersegment Eliminations [Member] | Electric Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Operating revenues	7	8	23	24
Intersegment Eliminations [Member] | Gas Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Operating revenues	23		68	3
Intersegment Eliminations [Member] | Other [Member]
Segment Reporting Information [Line Items]
Operating revenues	19	16	56	51
Intersegment Eliminations [Member] | Total Reportable Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	30	8	91	27
Corporate, Non-Segment [Member] | Other [Member]
Segment Reporting Information [Line Items]
Operating revenues	16	16	47	40
Segment income	(34)	(181)	(205)	(436)
Segment assets	2,240		2,240
Duke Energy Ohio [Member]
Segment Reporting Information [Line Items]
Operating revenues	471	489	1,426	1,433
Segment income	56	55	128	135
(Loss) Income From Discontinued Operations, net of tax	(1)	34	(1)	36
Net income	55	89	127	171
Segment assets	7,765		7,765		$ 7,528
Duke Energy Ohio [Member] | Electric Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Operating revenues	371	390	1,036	1,053
Duke Energy Ohio [Member] | Gas Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Operating revenues	90	89	360	358
Duke Energy Ohio [Member] | Other [Member]
Segment Reporting Information [Line Items]
Operating revenues	10	10	30	22
Duke Energy Ohio [Member] | Total Reportable Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	461	479	1,396	1,411
Duke Energy Ohio [Member] | Operating Segments [Member] | Electric Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Segment income	50	52	96	107
Segment assets	5,006		5,006
Duke Energy Ohio [Member] | Operating Segments [Member] | Gas Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Segment income	14	12	56	57
Segment assets	2,708		2,708
Duke Energy Ohio [Member] | Operating Segments [Member] | Total Reportable Segments [Member]
Segment Reporting Information [Line Items]
Segment income	64	64	152	164
Segment assets	7,714		7,714
Duke Energy Ohio [Member] | Corporate, Non-Segment [Member] | Other [Member]
Segment Reporting Information [Line Items]
Segment income	(8)	$ (9)	(24)	$ (29)
Segment assets	$ 51		$ 51

Business Segments (Schedule of

Business Segments (Schedule of Segment Reporting Information, by Segment) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Segment income	$ 956	$ 999	$ 2,360	$ 2,197
Duke Energy Carolinas [Member] | Other [Member]
Segment Reporting Information [Line Items]
Segment income	(6)	(16)	(18)	(50)
Progress Energy [Member] | Other [Member]
Segment Reporting Information [Line Items]
Segment income	(32)	(45)	(120)	(139)
Duke Energy Progress [Member] | Other [Member]
Segment Reporting Information [Line Items]
Segment income	(4)	(10)	(11)	(26)
Duke Energy Florida [Member] | Other [Member]
Segment Reporting Information [Line Items]
Segment income	(2)	(5)	(7)	(14)
Duke Energy Indiana [Member] | Other [Member]
Segment Reporting Information [Line Items]
Segment income	(2)	$ (3)	(5)	(10)
Piedmont Natural Gas [Member] | Other [Member]
Segment Reporting Information [Line Items]
Segment income	$ (5)		$ (18)	$ 7

Regulatory Matters (Narrative)

Regulatory Matters (Narrative) (Details) $ in Millions	1 Months Ended		3 Months Ended		9 Months Ended
	Oct. 31, 2017USD ($)	Dec. 31, 2015USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)MW	Sep. 30, 2016USD ($)	Dec. 31, 2016USD ($)
Public Utilities, General Disclosures [Line Items]
Public Utilities, Property, Plant and Equipment, Net			$ 84,862		$ 84,862		$ 82,520
Generation Facilities To Be Retired Net			441		441		529
Asset Impairment Charges			207	$ 10	216	$ 14
Electric Domestic Regulated Revenue			6,091	6,303	$ 16,122	16,321
Generation Facilities To Be Retired [Member]
Public Utilities, General Disclosures [Line Items]
Capacity (in MW) | MW					1,738
Public Utilities, Property, Plant and Equipment, Net			$ 405		$ 405
Atlantic Coast Pipeline (ACP) [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage			47.00%		47.00%
Long-term Purchase Commitment, Period					20 years
Sabal Trail Transmission Pipeline [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage			7.50%		7.50%
Estimated capital cost			$ 3,200		$ 3,200
Long-term Purchase Commitment, Period					25 years
Constitution Pipeline [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage			24.00%		24.00%
Estimated Contributions			$ 229		$ 229
Minimum [Member] | Atlantic Coast Pipeline (ACP) [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost			5,000		5,000
Maximum [Member] | Atlantic Coast Pipeline (ACP) [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost			$ 5,500		$ 5,500
Dominion Resources [Member] | Atlantic Coast Pipeline (ACP) [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage			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%
Spectra Energy Partners [Member] | Sabal Trail Transmission Pipeline [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage			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%
Williams Partners L.P. [Member] | Constitution Pipeline [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage			41.00%		41.00%
Duke Energy Carolinas [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Property, Plant and Equipment, Net			$ 27,352		$ 27,352		26,762
Duke Energy Carolinas [Member] | William States Lee Combined Cycle Facility [Member] | NCEMC [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost of new utility plant, including AFUDC			$ 600		$ 600
Joint owner ownership percentage			13.00%		13.00%
Duke Energy Carolinas [Member] | 2017 NC Rate Case [Member] | NCUC [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount					$ 647
Requested Rate Increase, Percentage					13.60%
Progress Energy [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Property, Plant and Equipment, Net			$ 31,340		$ 31,340		30,181
Generation Facilities To Be Retired Net			441		441		529
Asset Impairment Charges			135	1	137	4
Duke Energy Progress [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Property, Plant and Equipment, Net			18,752		18,752		18,387
Generation Facilities To Be Retired Net			441		441		529
Asset Impairment Charges				1		1
Duke Energy Progress [Member] | 2017 NC Rate Case [Member] | NCUC [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount					$ 477
Requested Rate Increase, Percentage					14.90%
Duke Energy Progress [Member] | Storm Cost Deferrals [Member] | NCUC [Member]
Public Utilities, General Disclosures [Line Items]
Amount of Regulatory Costs Not yet Approved			116		$ 116
Duke Energy Progress [Member] | Western Carolinas Modernization Plan [Member] | Asheville Plant [Member] | Generation Facilities To Be Retired [Member]
Public Utilities, General Disclosures [Line Items]
Capacity (in MW) | MW					376
Generation Facilities To Be Retired Net			405		$ 405		492
Duke Energy Progress [Member] | Western Carolinas Modernization Plan [Member] | NCUC [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost			893		893
Duke Energy Florida [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Property, Plant and Equipment, Net			12,586		12,586		11,790
Asset Impairment Charges			$ 135	1	$ 137	4
Duke Energy Florida [Member] | Hurricane Irma Storm Damage [Member] | FPSC [Member]
Public Utilities, General Disclosures [Line Items]
Customers Experiencing Outages			1,300,000		1,300,000
Amount of Regulatory Costs Not yet Approved			$ 500		$ 500
Duke Energy Florida [Member] | Hurricane Irma Storm Damage [Member] | FPSC [Member] | Storm Costs [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets			400		400
Duke Energy Florida [Member] | Hurricane Irma Storm Damage [Member] | FPSC [Member] | Storm Costs [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Liabilities			60		60
Amount of Regulatory Costs Not yet Approved			132		132
Duke Energy Florida [Member] | 2017 Second Revised and Restated Settlement | FPSC [Member]
Public Utilities, General Disclosures [Line Items]
Approved Rate Increase (Decrease), Amount					$ 67
Asset Impairment Charges			135
Approved return on equity percentage					9.50%
Duke Energy Florida [Member] | 2017 Second Revised and Restated Settlement | FPSC [Member] | Under-recovered Fuel [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets			196		$ 196
Regulatory Asset, Amortization Period					24 months
Duke Energy Florida [Member] | Levy Nuclear Project [Member] | FPSC [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount					$ 82
Duke Energy Florida [Member] | Hines Chiller Uprate Project [Member] | FPSC [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost			150		150
Approved Rate Increase (Decrease), Amount					19
Duke Energy Ohio [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Property, Plant and Equipment, Net			5,851		5,851		5,547
Asset Impairment Charges					1
Electric Domestic Regulated Revenue			371	390	1,036	1,053
Duke Energy Ohio [Member] | Regional Transmission Organization Realignment [Member]
Public Utilities, General Disclosures [Line Items]
Exit obligation			90		90		90
Regulatory Assets			$ 71		$ 71		71
Approved MVP Proposals			17		17
MISO estimate of Duke Energy Ohio's MVP obligation					$ 2,700
Duke Energy Ohio [Member] | Duke Energy Kentucky Rate Case [Member] | KPSC [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount					$ 49
Requested Rate Increase, Percentage					15.00%
Duke Energy Ohio [Member] | Woodsdale Station Fuel System [Member] | KPSC [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost			$ 55		$ 55
Duke Energy Ohio [Member] | East Bend Coal Ash Basin Filing [Member] | KPSC [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost			93		93
Duke Energy Ohio [Member] | 2017 Ohio Base Rate Case [Member] | PUCO [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount					$ 15
Requested Return on Equity, Percentage					10.40%
Duke Energy Ohio [Member] | 2017 Ohio Base Rate Case [Member] | PUCO [Member] | Minimum [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount					$ (18)
Requested Return on Equity, Percentage					9.22%
Duke Energy Ohio [Member] | 2017 Ohio Base Rate Case [Member] | PUCO [Member] | Maximum [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount					$ (29)
Requested Return on Equity, Percentage					10.24%
Duke Energy Ohio [Member] | Natural Gas Pipeline Extension [Member] | OPSB [Member]
Public Utilities, General Disclosures [Line Items]
Estimated Capital Cost Excluding AFUDC			110		$ 110
Duke Energy Ohio [Member] | Advanced Metering Infrastructure Project [Member] | KPSC [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost			49		49
Regulatory Assets			7		7
Duke Energy Ohio [Member] | Accelerated Natural Gas Service Line Replacement Rider [Member] | PUCO [Member]
Public Utilities, General Disclosures [Line Items]
Amount of Regulatory Costs Not yet Approved			240		240
Duke Energy Ohio [Member] | Energy Efficiency Cost Recovery [Member] | PUCO [Member]
Public Utilities, General Disclosures [Line Items]
Electric Domestic Regulated Revenue		$ 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
Duke Energy Ohio [Member] | MGP Cost Recovery [Member] | PUCO [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets			36		36
Duke Energy Indiana [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Property, Plant and Equipment, Net			10,124		10,124		9,924
Asset Impairment Charges				$ 8		8
Duke Energy Indiana [Member] | Benton County Wind Farm Dispute [Member]
Public Utilities, General Disclosures [Line Items]
Loss contingency, damages sought, value					16
Litigation Settlement, Amount Awarded to Other Party					29
Duke Energy Indiana [Member] | Coal Combustion Residual Plan [Member] | IURC [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount					$ 380
Federal Mandate Costs Recovered Through Tracker Mechanism					80.00%
Federally Mandated Costs Recovered In Future Rate Case					20.00%
Percentage of Costs Recovered through Existing Rider					60.00%
Percentage Recovered Through Future Rate Case					40.00%
Interest Rate on Intermediary Debt for Electric Utility Plant Construction					4.73%
Duke Energy Indiana [Member] | Coal Combustion Residual Plan [Member] | IURC [Member] | Maximum [Member]
Public Utilities, General Disclosures [Line Items]
Approved Rate Increase (Decrease), Amount					$ 365
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, Percentage					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, Percentage					9.70%
Duke Energy Indiana [Member] | Grid Infrastructure Improvement Plan [Member] | IURC [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Property, Plant and Equipment, Net			43		$ 43
Asset Impairment Charges						$ 8
Piedmont Natural Gas [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Property, Plant and Equipment, Net			$ 5,125		5,125		$ 4,814
Asset Impairment Charges					$ 7
Piedmont Natural Gas [Member] | South Carolina RSA Filing [Member] | PSCSC [Member]
Public Utilities, General Disclosures [Line Items]
Requested Return on Equity, Percentage					12.60%
Approved return on equity percentage					10.20%
Piedmont Natural Gas [Member] | NCUC IMR Petition Filed October 2017 [Member] | NCUC [Member] | Subsequent Event [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount	$ 8.9
Piedmont Natural Gas [Member] | NCUC IMR Petition Filed May 2017 [Member] | NCUC [Member]
Public Utilities, General Disclosures [Line Items]
Approved Rate Increase (Decrease), Amount					$ 11.6

Regulatory Matters (Schedule of

Regulatory Matters (Schedule of Net Carrying Value Of Facilities and Megawatt Capacity) (Details) $ in Millions	9 Months Ended
	Sep. 30, 2017USD ($)MW	Dec. 31, 2016USD ($)
Public Utilities, General Disclosures [Line Items]
Public Utilities, Property, Plant and Equipment, Net	$ 84,862	$ 82,520
Duke Energy Carolinas [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Property, Plant and Equipment, Net	27,352	26,762
Progress Energy [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Property, Plant and Equipment, Net	31,340	30,181
Duke Energy Florida [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Property, Plant and Equipment, Net	12,586	11,790
Duke Energy Indiana [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Property, Plant and Equipment, Net	$ 10,124	$ 9,924
Generation Facilities To Be Retired [Member]
Public Utilities, General Disclosures [Line Items]
Capacity (in MW) | MW	1,738
Public Utilities, Property, Plant and Equipment, Net	$ 405
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	$ 164
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	873
Public Utilities, Property, Plant and Equipment, Net	$ 111
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	873
Public Utilities, Property, Plant and Equipment, Net	$ 111
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	$ 130

Commitments and Contingencies60

Commitments and Contingencies (Narrative) (Details) gal in Millions	1 Months Ended	3 Months Ended	9 Months Ended
	Feb. 28, 2014Tgal	Sep. 30, 2017USD ($)plantclaim	Sep. 30, 2017USD ($)plantclaim	Dec. 31, 2016USD ($)	Mar. 31, 2014USD ($)
Valuation and Qualifying Accounts [Abstract]
Loss Contingency Accrual		$ 83,000,000	$ 83,000,000	$ 98,000,000
Progress Energy Merger Shareholder Litigation [Member]
Valuation and Qualifying Accounts [Abstract]
Proceeds from Legal Settlements		$ 20,000,000
Coal Ash Insurance Coverage Litigation [Member]
Valuation and Qualifying Accounts [Abstract]
Number of NC and SC Plants with Ash Basins | plant		15	15
NCDEQ State Enforcement Actions [Member]
Valuation and Qualifying Accounts [Abstract]
Number of Plants with No Disputed Facts | plant		7	7
Number of NC Plants with Ash Basins | plant		14	14
Number of Plants with Disputed Facts | plant		7	7
Groundwater Contamination Claims [Member]
Valuation and Qualifying Accounts [Abstract]
Goodwill Payment		$ 5,000	$ 5,000
Water Bill Stipend Period			25 years
Duke Energy Carolinas [Member]
Valuation and Qualifying Accounts [Abstract]
Loss Contingency Accrual		23,000,000	$ 23,000,000	23,000,000
Duke Energy Carolinas [Member] | Groundwater Contamination Claims [Member]
Valuation and Qualifying Accounts [Abstract]
Loss Contingency Accrual		19,000,000	19,000,000
Duke Energy Carolinas [Member] | Asbestos-related Injuries and Damages Claims [Member]
Valuation and Qualifying Accounts [Abstract]
Asbestos-related injuries and damages reserves		486,000,000	486,000,000	512,000,000
Reinsurance retention policy, excess retention, amount reinsured			797,000,000
Probable insurance recoveries		$ 570,000,000	$ 570,000,000	587,000,000
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		120	120
Asbestos-related injuries and damages reserves		$ 29,000,000	$ 29,000,000
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		57	57
Asbestos-related injuries and damages reserves		$ 16,000,000	$ 16,000,000
Duke Energy Carolinas [Member] | Minimum [Member] | North Carolina Ash Basins [Member] | Dan River [Member]
Valuation and Qualifying Accounts [Abstract]
Coal ash released, in tons | T	30,000
Basin water released, in gallons | gal	24
Duke Energy Carolinas [Member] | Maximum [Member] | North Carolina Ash Basins [Member] | Dan River [Member]
Valuation and Qualifying Accounts [Abstract]
Coal ash released, in tons | T	39,000
Basin water released, in gallons | gal	27
Progress Energy [Member]
Valuation and Qualifying Accounts [Abstract]
Loss Contingency Accrual		56,000,000	56,000,000	59,000,000
Duke Energy Progress [Member]
Valuation and Qualifying Accounts [Abstract]
Loss Contingency Accrual		13,000,000	13,000,000	14,000,000
Duke Energy Progress [Member] | Groundwater Contamination Claims [Member]
Valuation and Qualifying Accounts [Abstract]
Loss Contingency Accrual		4,000,000	4,000,000
Duke Energy Florida [Member]
Valuation and Qualifying Accounts [Abstract]
Loss Contingency Accrual		28,000,000	28,000,000	28,000,000
Duke Energy Florida [Member] | Westinghouse Electric Company Litigation [Member]
Valuation and Qualifying Accounts [Abstract]
Gain Contingency, Unrecorded Amount		54,000,000	54,000,000
Loss Contingency, Damages Sought, Original Amount		482,000,000	482,000,000		$ 510,000,000
Loss Contingency, Damages Awarded, Value			30,000,000
Gain Contingency, Dismissed Amount		54,000,000	54,000,000
Loss contingency, damages sought, value			424,000,000
Loss Contingency Damages Awarded and Interest, Value			34,000,000
Duke Energy Florida [Member] | MGP Cost Recovery Action [Member]
Valuation and Qualifying Accounts [Abstract]
Gain Contingency, Unrecorded Amount		$ 43,000,000	$ 43,000,000
Duke Energy Ohio [Member]
Valuation and Qualifying Accounts [Abstract]
Loss Contingency Accrual				$ 4,000,000

Commitments and Contingencies61

Commitments and Contingencies (Schedule of Environmental Loss Contingencies) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	$ 58
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	98	$ 94
Provisions/adjustments	(1)	34
Cash reductions	(13)	(12)
Ending balance	84	116
Duke Energy Carolinas [Member]
Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	20
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	10	10
Provisions/adjustments	2	5
Cash reductions	(2)	(4)
Ending balance	10	11
Progress Energy [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	18	17
Provisions/adjustments	1	5
Cash reductions	(3)	(6)
Ending balance	16	16
Duke Energy Progress [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	3	3
Provisions/adjustments		2
Cash reductions	0	(2)
Ending balance	3	3
Duke Energy Florida [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	14	14
Provisions/adjustments	1	3
Cash reductions	(3)	(4)
Ending balance	12	13
Duke Energy Ohio [Member]
Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	30
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	59	54
Provisions/adjustments	(3)	6
Cash reductions	(7)	(1)
Ending balance	49	59
Duke Energy Indiana [Member]
Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	3
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	10	12
Provisions/adjustments	(2)	20
Cash reductions	(1)	(2)
Ending balance	7	30
Piedmont Natural Gas [Member]
Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	2
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	1	1
Provisions/adjustments	1
Cash reductions	0
Ending balance	$ 2	$ 1

Commitments and Contingencies62

Commitments and Contingencies (Schedule of Legal Reserves) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Loss Contingencies [Line Items]
Reserves for legal matters	$ 83	$ 98
Duke Energy Carolinas [Member]
Loss Contingencies [Line Items]
Reserves for legal matters	23	23
Progress Energy [Member]
Loss Contingencies [Line Items]
Reserves for legal matters	56	59
Duke Energy Progress [Member]
Loss Contingencies [Line Items]
Reserves for legal matters	13	14
Duke Energy Florida [Member]
Loss Contingencies [Line Items]
Reserves for legal matters	28	28
Duke Energy Ohio [Member]
Loss Contingencies [Line Items]
Reserves for legal matters		4
Piedmont Natural Gas [Member]
Loss Contingencies [Line Items]
Reserves for legal matters	$ 2	$ 2

Debt and Credit Facilities (Nar

Debt and Credit Facilities (Narrative) (Details) - USD ($)	9 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Feb. 28, 2017
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Facility size	$ 8,000,000,000		$ 8,000,000,000	$ 7,500,000,000
Parent Company [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Facility size	2,850,000,000
Parent Company [Member] | June 2017 Three Year Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Facility size		$ 1,000,000,000
Long-term Line of Credit	$ 270,000,000
Debt Instrument, Term	3 years
Piedmont Natural Gas [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Facility size	$ 500,000,000			$ 850,000,000
Piedmont Natural Gas [Member] | June 2017 Piedmont Term Loan Facility [Member]
Debt Instrument [Line Items]
Facility size		$ 250,000,000
Long-term Line of Credit	$ 250,000,000
Debt Instrument, Term	18 months
Duke Energy Carolinas [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Facility size	$ 1,350,000,000
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	1,250,000,000
Duke Energy Progress [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

Debt and Credit Facilities (Sum

Debt and Credit Facilities (Summary of Debt Issuances) (Details) - USD ($)	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Debt Instrument [Line Items]
Debt issuances	$ 5,120,000,000
Repayments of Debt	2,035,000,000	$ 988,000,000
Current maturities of long-term debt	2,485,000,000		$ 2,319,000,000
Parent Company [Member]
Debt Instrument [Line Items]
Debt issuances	2,500,000,000
Parent Company [Member] | August 2017 Debt Maturity [Member]
Debt Instrument [Line Items]
Repayments of Debt	700,000,000
Parent Company [Member] | April 2017 Maturity [Member]
Debt Instrument [Line Items]
Repayments of Debt	400,000,000
Duke Energy Progress [Member]
Debt Instrument [Line Items]
Debt issuances	800,000,000
Repayments of Debt	270,000,000	15,000,000
Current maturities of long-term debt	203,000,000		452,000,000
Duke Energy Florida [Member]
Debt Instrument [Line Items]
Debt issuances	900,000,000
Repayments of Debt	341,000,000	12,000,000
Current maturities of long-term debt	567,000,000		326,000,000
Duke Energy Ohio [Member]
Debt Instrument [Line Items]
Debt issuances	100,000,000
Repayments of Debt	2,000,000	$ 53,000,000
Current maturities of long-term debt			$ 1,000,000
Unsecured Debt [Member] | April 2017 Debt Issuance, 3.364% Coupon [Member]
Debt Instrument [Line Items]
Debt issuances	$ 420,000,000
Interest rate	3.364%
Unsecured Debt [Member] | June 2017 Debt Issuance, 2.100% Coupon [Member]
Debt Instrument [Line Items]
Debt issuances	$ 330,000,000
Interest rate	2.10%
Unsecured Debt [Member] | August 2017 Debt Issuance, 2.400% Coupon [Member]
Debt Instrument [Line Items]
Debt issuances	$ 500,000,000
Interest rate	2.40%
Unsecured Debt [Member] | August 2017 Debt Issuance, 3.150% Coupon [Member]
Debt Instrument [Line Items]
Debt issuances	$ 750,000,000
Interest rate	3.15%
Unsecured Debt [Member] | August 2017 Debt Issuance, 3.950% Coupon [Member]
Debt Instrument [Line Items]
Debt issuances	$ 500,000,000
Interest rate	3.95%
Unsecured Debt [Member] | Parent Company [Member] | April 2017 Debt Issuance, 3.364% Coupon [Member]
Debt Instrument [Line Items]
Debt issuances	$ 420,000,000
Unsecured Debt [Member] | Parent Company [Member] | June 2017 Debt Issuance, 2.100% Coupon [Member]
Debt Instrument [Line Items]
Debt issuances	330,000,000
Unsecured Debt [Member] | Parent Company [Member] | August 2017 Debt Issuance, 2.400% Coupon [Member]
Debt Instrument [Line Items]
Debt issuances	500,000,000
Unsecured Debt [Member] | Parent Company [Member] | August 2017 Debt Issuance, 3.150% Coupon [Member]
Debt Instrument [Line Items]
Debt issuances	750,000,000
Unsecured Debt [Member] | Parent Company [Member] | August 2017 Debt Issuance, 3.950% Coupon [Member]
Debt Instrument [Line Items]
Debt issuances	500,000,000
Secured Debt [Member] | February 2017 Debt Issuance, 4.120% Coupon [Member]
Debt Instrument [Line Items]
Debt issuances	$ 587,000,000
Interest rate	4.12%
Secured Debt [Member] | August 2017 Debt Issuance, 4.110% Coupon [Member]
Debt Instrument [Line Items]
Debt issuances	$ 233,000,000
Interest rate	4.11%
First Mortgage [Member] | January 2017 Debt Issuance, 1.850% Coupon [Member]
Debt Instrument [Line Items]
Debt issuances	$ 250,000,000
Interest rate	1.85%
First Mortgage [Member] | January 2017 Debt Issuance, 3.200% Coupon [Member]
Debt Instrument [Line Items]
Debt issuances	$ 650,000,000
Interest rate	3.20%
First Mortgage [Member] | March 2017 Debt Issuance, 3.700% Coupon [Member]
Debt Instrument [Line Items]
Debt issuances	$ 100,000,000
Interest rate	3.70%
First Mortgage [Member] | September 2017 Debt Issuance, Floating Rate [Member]
Debt Instrument [Line Items]
Debt issuances	$ 300,000,000
Interest rate	1.50%
First Mortgage [Member] | September 2017 Debt Issuance, 3.600% Coupon
Debt Instrument [Line Items]
Debt issuances	$ 500,000,000
Interest rate	3.60%
First Mortgage [Member] | Duke Energy Progress [Member] | September 2017 Debt Issuance, Floating Rate [Member]
Debt Instrument [Line Items]
Debt issuances	$ 300,000,000
First Mortgage [Member] | Duke Energy Progress [Member] | September 2017 Debt Issuance, 3.600% Coupon
Debt Instrument [Line Items]
Debt issuances	$ 500,000,000
First Mortgage [Member] | Duke Energy Progress [Member] | Bonds Maturing November 2017, Floating Rate [Member]
Debt Instrument [Line Items]
Interest rate	1.516%
Current maturities of long-term debt	$ 200,000,000
First Mortgage [Member] | Duke Energy Florida [Member] | January 2017 Debt Issuance, 1.850% Coupon [Member]
Debt Instrument [Line Items]
Debt issuances	250,000,000
First Mortgage [Member] | Duke Energy Florida [Member] | January 2017 Debt Issuance, 3.200% Coupon [Member]
Debt Instrument [Line Items]
Debt issuances	650,000,000
First Mortgage [Member] | Duke Energy Florida [Member] | Bonds Maturing September 2017, 5.800% Coupon [Member]
Debt Instrument [Line Items]
Repayments of Debt	250,000,000
First Mortgage [Member] | Duke Energy Ohio [Member] | March 2017 Debt Issuance, 3.700% Coupon [Member]
Debt Instrument [Line Items]
Debt issuances	$ 100,000,000

Debt and Credit Facilities (S65

Debt and Credit Facilities (Summary of Current Maturities of Long-term Debt)(Details) - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Current maturities of long-term debt	$ 2,485,000,000	$ 2,319,000,000
Other Debt Obligations [Member]
Debt Instrument [Line Items]
Current maturities of long-term debt	$ 335,000,000
Parent Company [Member] | Unsecured Debt [Member] | Debt Maturing June 2018, 6.250% Coupon [Member]
Debt Instrument [Line Items]
Interest rate	6.25%
Current maturities of long-term debt	$ 250,000,000
Parent Company [Member] | Unsecured Debt [Member] | Debt Maturing June 2018, 2.100% Coupon [Member]
Debt Instrument [Line Items]
Interest rate	2.10%
Current maturities of long-term debt	$ 500,000,000
Duke Energy Progress [Member]
Debt Instrument [Line Items]
Current maturities of long-term debt	$ 203,000,000	452,000,000
Duke Energy Progress [Member] | First Mortgage Bonds [Member] | Bonds Maturing November 2017, Floating Rate [Member]
Debt Instrument [Line Items]
Interest rate	1.516%
Current maturities of long-term debt	$ 200,000,000
Duke Energy Carolinas [Member]
Debt Instrument [Line Items]
Current maturities of long-term debt	$ 705,000,000	116,000,000
Duke Energy Carolinas [Member] | First Mortgage Bonds [Member] | Bonds Maturing January 2018, 5.250% Coupon [Member]
Debt Instrument [Line Items]
Interest rate	5.25%
Current maturities of long-term debt	$ 400,000,000
Duke Energy Carolinas [Member] | First Mortgage Bonds [Member] | Bonds Maturing April 2018, 5.100% Coupon [Member]
Debt Instrument [Line Items]
Interest rate	5.10%
Current maturities of long-term debt	$ 300,000,000
Duke Energy Florida [Member]
Debt Instrument [Line Items]
Current maturities of long-term debt	$ 567,000,000	$ 326,000,000
Duke Energy Florida [Member] | First Mortgage Bonds [Member] | Bonds Maturing June 2018, 5.650% Coupon [Member]
Debt Instrument [Line Items]
Interest rate	5.65%
Current maturities of long-term debt	$ 500,000,000

Debt and Credit Facilities (Sch

Debt and Credit Facilities (Schedule of Line of Credit Facilities) (Details) - Revolving Credit Facility [Member] - USD ($)	Sep. 30, 2017	Mar. 31, 2017	Feb. 28, 2017
Line of Credit Facility [Line Items]
Facility size	$ 8,000,000,000	$ 8,000,000,000	$ 7,500,000,000
Commercial paper	(1,569,000,000)
Outstanding letters of credit	(60,000,000)
Tax exempt bonds	(81,000,000)
Coal ash set-aside	(500,000,000)
Available capacity	5,790,000,000
Parent Company [Member]
Line of Credit Facility [Line Items]
Facility size	2,850,000,000
Commercial paper	(404,000,000)
Outstanding letters of credit	(51,000,000)
Available capacity	2,395,000,000
Duke Energy Carolinas [Member]
Line of Credit Facility [Line Items]
Facility size	1,350,000,000
Commercial paper	(636,000,000)
Outstanding letters of credit	(4,000,000)
Coal ash set-aside	(250,000,000)
Available capacity	460,000,000
Duke Energy Progress [Member]
Line of Credit Facility [Line Items]
Facility size	1,250,000,000
Commercial paper	(150,000,000)
Outstanding letters of credit	(2,000,000)
Coal ash set-aside	(250,000,000)
Available capacity	848,000,000
Duke Energy Florida [Member]
Line of Credit Facility [Line Items]
Facility size	1,000,000,000
Outstanding letters of credit	(1,000,000)
Available capacity	999,000,000
Duke Energy Ohio [Member]
Line of Credit Facility [Line Items]
Facility size	450,000,000
Commercial paper	(25,000,000)
Available capacity	425,000,000
Duke Energy Indiana [Member]
Line of Credit Facility [Line Items]
Facility size	600,000,000
Commercial paper	(150,000,000)
Tax exempt bonds	(81,000,000)
Available capacity	369,000,000
Piedmont Natural Gas [Member]
Line of Credit Facility [Line Items]
Facility size	500,000,000		$ 850,000,000
Commercial paper	(204,000,000)
Outstanding letters of credit	(2,000,000)
Available capacity	294,000,000
Proceeds Loaned To Subsidiary Registrants [Member] | Parent Company [Member]
Line of Credit Facility [Line Items]
Commercial paper	$ (625,000,000)

Asset Retirement Obligations As

Asset Retirement Obligations Asset Retirement Obligations (ARO by Category) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Asset Retirement Obligations [Line Items]
Total ARO	$ 10,205	$ 10,611
Less: current portion	619	411
Total noncurrent ARO	9,586	10,200
Duke Energy Carolinas [Member]
Asset Retirement Obligations [Line Items]
Total ARO	3,601	3,895
Less: current portion	304	222
Total noncurrent ARO	3,297	3,673
Progress Energy [Member]
Asset Retirement Obligations [Line Items]
Total ARO	5,439	5,475
Less: current portion	250	189
Total noncurrent ARO	5,189	5,286
Duke Energy Progress [Member]
Asset Retirement Obligations [Line Items]
Total ARO	4,676	4,697
Less: current portion	250	189
Total noncurrent ARO	4,426	4,508
Duke Energy Florida [Member]
Asset Retirement Obligations [Line Items]
Total ARO	763	778
Total noncurrent ARO	763	778
Duke Energy Ohio [Member]
Asset Retirement Obligations [Line Items]
Total ARO	81	77
Less: current portion	6
Total noncurrent ARO	75	77
Duke Energy Indiana [Member]
Asset Retirement Obligations [Line Items]
Total ARO	793	866
Less: current portion	58
Total noncurrent ARO	735	866
Piedmont Natural Gas [Member]
Asset Retirement Obligations [Line Items]
Total ARO	15	14
Total noncurrent ARO	15	$ 14
Decommissioning of Nuclear Power Facilities [Member]
Asset Retirement Obligations [Line Items]
Total ARO	5,337
Decommissioning of Nuclear Power Facilities [Member] | Duke Energy Carolinas [Member]
Asset Retirement Obligations [Line Items]
Total ARO	1,916
Decommissioning of Nuclear Power Facilities [Member] | Progress Energy [Member]
Asset Retirement Obligations [Line Items]
Total ARO	3,235
Decommissioning of Nuclear Power Facilities [Member] | Duke Energy Progress [Member]
Asset Retirement Obligations [Line Items]
Total ARO	2,536
Decommissioning of Nuclear Power Facilities [Member] | Duke Energy Florida [Member]
Asset Retirement Obligations [Line Items]
Total ARO	699
Closure of Ash Impoundments [Member]
Asset Retirement Obligations [Line Items]
Total ARO	4,594
Closure of Ash Impoundments [Member] | Duke Energy Carolinas [Member]
Asset Retirement Obligations [Line Items]
Total ARO	1,650
Closure of Ash Impoundments [Member] | Progress Energy [Member]
Asset Retirement Obligations [Line Items]
Total ARO	2,124
Closure of Ash Impoundments [Member] | Duke Energy Progress [Member]
Asset Retirement Obligations [Line Items]
Total ARO	2,105
Closure of Ash Impoundments [Member] | Duke Energy Florida [Member]
Asset Retirement Obligations [Line Items]
Total ARO	19
Closure of Ash Impoundments [Member] | Duke Energy Ohio [Member]
Asset Retirement Obligations [Line Items]
Total ARO	42
Closure of Ash Impoundments [Member] | Duke Energy Indiana [Member]
Asset Retirement Obligations [Line Items]
Total ARO	777
Other [Member]
Asset Retirement Obligations [Line Items]
Total ARO	274
Other [Member] | Duke Energy Carolinas [Member]
Asset Retirement Obligations [Line Items]
Total ARO	35
Other [Member] | Progress Energy [Member]
Asset Retirement Obligations [Line Items]
Total ARO	80
Other [Member] | Duke Energy Progress [Member]
Asset Retirement Obligations [Line Items]
Total ARO	35
Other [Member] | Duke Energy Florida [Member]
Asset Retirement Obligations [Line Items]
Total ARO	45
Other [Member] | Duke Energy Ohio [Member]
Asset Retirement Obligations [Line Items]
Total ARO	39
Other [Member] | Duke Energy Indiana [Member]
Asset Retirement Obligations [Line Items]
Total ARO	16
Other [Member] | Piedmont Natural Gas [Member]
Asset Retirement Obligations [Line Items]
Total ARO	$ 15

Asset Retirement Obligations (A

Asset Retirement Obligations (ARO Rollforward) (Details) $ in Millions	9 Months Ended
	Sep. 30, 2017USD ($)
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of period	$ 10,611
Accretion expense	329
Liabilities settled	(430)
Liabilities incurred in the current year	48
Revision in estimates of cash flows	(353)
Balance at end of period	10,205
Duke Energy Carolinas [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of period	3,895
Accretion expense	140
Liabilities settled	(201)
Liabilities incurred in the current year	5
Revision in estimates of cash flows	(238)
Balance at end of period	3,601
Progress Energy [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of period	5,475
Accretion expense	172
Liabilities settled	(193)
Revision in estimates of cash flows	(15)
Balance at end of period	5,439
Duke Energy Progress [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of period	4,697
Accretion expense	147
Liabilities settled	(152)
Revision in estimates of cash flows	(16)
Balance at end of period	4,676
Duke Energy Florida [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of period	778
Accretion expense	25
Liabilities settled	(41)
Revision in estimates of cash flows	1
Balance at end of period	763
Duke Energy Ohio [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of period	77
Accretion expense	3
Liabilities settled	(4)
Liabilities incurred in the current year	7
Revision in estimates of cash flows	(2)
Balance at end of period	81
Duke Energy Indiana [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of period	866
Accretion expense	25
Liabilities settled	(26)
Liabilities incurred in the current year	27
Revision in estimates of cash flows	(99)
Balance at end of period	793
Piedmont Natural Gas [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of period	14
Accretion expense	1
Liabilities settled	(7)
Liabilities incurred in the current year	7
Balance at end of period	$ 15

Goodwill and Intangible Asset69

Goodwill and Intangible Assets (Details) - USD ($)	3 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Goodwill [Line Items]
Goodwill	$ 19,418,000,000	$ 19,425,000,000
Accumulated impairment charges	(7,000,000)
Impairment Charges	7,000,000
Electric Utilities and Infrastructure [Member]
Goodwill [Line Items]
Goodwill	17,379,000,000	17,379,000,000
Accumulated impairment charges	0
Gas Utilities and Infrastructure [Member]
Goodwill [Line Items]
Goodwill	1,924,000,000	1,924,000,000
Accumulated impairment charges	0
Commercial Renewables [Member]
Goodwill [Line Items]
Goodwill	115,000,000	122,000,000
Accumulated impairment charges	(7,000,000)
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, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
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	$ 205	$ 204	$ 645	$ 620
Duke Energy Carolinas [Member] | Indemnification Coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	5	5	17	16
Duke Energy Carolinas [Member] | Joint Dispatch Agreement [Member] | Duke Energy Progress [Member]
Related Party Transaction [Line Items]
Related party transaction, other revenues from transactions with related party	9	10	42	21
Related party transaction, expenses from transactions with related party	39	36	91	127
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		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	208	182	555	515
Progress Energy [Member] | Indemnification Coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	10	9	29	25
Progress Energy [Member] | Joint Dispatch Agreement [Member] | Duke Energy Carolinas [Member]
Related Party Transaction [Line Items]
Related party transaction, other revenues from transactions with related party	39	36	91	127
Related party transaction, expenses from transactions with related party	9	10	42	21
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	19		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	114	103	321	292
Duke Energy Progress [Member] | Indemnification Coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	4	4	11	10
Duke Energy Progress [Member] | Joint Dispatch Agreement [Member] | Duke Energy Carolinas [Member]
Related Party Transaction [Line Items]
Related party transaction, other revenues from transactions with related party	39	36	91	127
Related party transaction, expenses from transactions with related party	9	10	42	21
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	19		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	94	79	234	223
Duke Energy Florida [Member] | Indemnification Coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	6	5	18	15
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	90	89	275	261
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	4
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	93	96	281	279
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] | Corporate Governance And Shared Service Expenses [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	10		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		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	$ 22		$ 62
Piedmont Natural Gas [Member] | Intercompany Natural Gas Transactions [Member] | Duke Energy Carolinas [Member]
Related Party Transaction [Line Items]
Related party transaction, other revenues from transactions with related party		1		3
Piedmont Natural Gas [Member] | Intercompany Natural Gas Transactions [Member] | Duke Energy Progress [Member]
Related Party Transaction [Line Items]
Related party transaction, other revenues from transactions with related party		$ 19		$ 57

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, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	$ 6	$ 8	$ 19	$ 22
Accounts Payable, Related Parties, Current	2		2		$ 2
Cardinal Pipeline Company, LLC [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	2	3	6	7
Pine Needle LNG Company, LLC [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	2	3	6	8
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 (Int

Related Party Transactions (Intercompany Income Taxes) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Piedmont Natural Gas [Member]
Related Party Transaction [Line Items]
Income taxes receivable	$ 99	$ 9
Affiliated Entity [Member] | Duke Energy Carolinas [Member]
Related Party Transaction [Line Items]
Income taxes receivable		1
Income tax payable	173
Affiliated Entity [Member] | Progress Energy [Member]
Related Party Transaction [Line Items]
Income taxes receivable	170
Income tax payable		37
Affiliated Entity [Member] | Duke Energy Progress [Member]
Related Party Transaction [Line Items]
Income tax payable	46	90
Affiliated Entity [Member] | Duke Energy Florida [Member]
Related Party Transaction [Line Items]
Income taxes receivable	120	37
Affiliated Entity [Member] | Duke Energy Ohio [Member]
Related Party Transaction [Line Items]
Income tax payable	18	1
Affiliated Entity [Member] | Duke Energy Indiana [Member]
Related Party Transaction [Line Items]
Income tax payable	104	3
Affiliated Entity [Member] | Piedmont Natural Gas [Member]
Related Party Transaction [Line Items]
Income taxes receivable	$ 89
Income tax payable		$ 38

Derivatives and Hedging (Notion

Derivatives and Hedging (Notional Amounts of Derivative Instruments) (Details) Mcf in Millions, $ in Millions	3 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)GWhMcf	Sep. 30, 2016USD ($)	Dec. 31, 2016USD ($)GWhMcf	Aug. 31, 2016USD ($)
Commodity Contracts [Member] | Electricity [Member]
Derivative [Line Items]
Notional amount, energy measure, in gigawatt-hours | GWh		112		147
Commodity Contracts [Member] | Natural Gas [Member]
Derivative [Line Items]
Notional amount, volume, in millions of decatherms | Mcf		786		890
Interest Rate Contracts [Member]
Derivative [Line Items]
Notional amount		$ 1,630		$ 1,677
Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Notional amount		703		750
Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Notional amount		927		927
Variable Interest Entity, Primary Beneficiary [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional amount		$ 703		$ 750
Piedmont Natural Gas [Member]
Derivative [Line Items]
Notional amount					$ 1,400
Loss on Interest Rate Derivative Instruments Not Designated as Hedging Instruments	$ 22		$ 190
Duke Energy Carolinas [Member] | Commodity Contracts [Member] | Natural Gas [Member]
Derivative [Line Items]
Notional amount, volume, in millions of decatherms | Mcf		103		91
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		193		269
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		124		118
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		69		151
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		112		147
Duke Energy Indiana [Member] | Commodity Contracts [Member] | Natural Gas [Member]
Derivative [Line Items]
Notional amount, volume, in millions of decatherms | Mcf		1		1
Piedmont Natural Gas [Member] | Commodity Contracts [Member] | Natural Gas [Member]
Derivative [Line Items]
Notional amount, volume, in millions of decatherms | Mcf		489		529

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, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	$ 69	$ 162
Location and fair value amounts of derivatives (Liability)	191	252
Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	49	111
Noncurrent Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	20	51
Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	60	52
Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	131	200
Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	54	140
Location and fair value amounts of derivatives (Liability)	142	209
Interest Rate Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	15	22
Location and fair value amounts of derivatives (Liability)	49	43
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)	14	19
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	8
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	8
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)	48	108
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)	6	32
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)	29	43
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)	113	166
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	3
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)	24	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)	9	26
Duke Energy Carolinas [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	8	33
Location and fair value amounts of derivatives (Liability)	25	16
Duke Energy Carolinas [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	6	23
Duke Energy Carolinas [Member] | Noncurrent Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	2	10
Duke Energy Carolinas [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	24
Duke Energy Carolinas [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	1	16
Duke Energy Carolinas [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	8	33
Location and fair value amounts of derivatives (Liability)	2	1
Duke Energy Carolinas [Member] | Interest Rate Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	23	15
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)	6	23
Duke Energy Carolinas [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)	2	10
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)	1
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)	1	1
Duke Energy Carolinas [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)	23
Duke Energy Carolinas [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)		15
Progress Energy [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	15	85
Location and fair value amounts of derivatives (Liability)	22	25
Progress Energy [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	11	64
Progress Energy [Member] | Noncurrent Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	4	21
Progress Energy [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	11	12
Progress Energy [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	11	13
Progress Energy [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	14	82
Location and fair value amounts of derivatives (Liability)	18	19
Progress Energy [Member] | Interest Rate Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	3
Location and fair value amounts of derivatives (Liability)	4	6
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)	10	61
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)	4	21
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)	11	12
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)	7	7
Progress Energy [Member] | 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	3
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)	4	6
Duke Energy Progress [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	8	46
Location and fair value amounts of derivatives (Liability)	7	7
Duke Energy Progress [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	5	36
Duke Energy Progress [Member] | Noncurrent Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	3	10
Duke Energy Progress [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	2
Duke Energy Progress [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	5	7
Duke Energy Progress [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	8	45
Location and fair value amounts of derivatives (Liability)	3	1
Duke Energy Progress [Member] | Interest Rate Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)		1
Location and fair value amounts of derivatives (Liability)	4	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)	5	35
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)	3	10
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)	2
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)	1	1
Duke Energy Progress [Member] | 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
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)	4	6
Duke Energy Florida [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	6	39
Location and fair value amounts of derivatives (Liability)	9	12
Duke Energy Florida [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	5	28
Duke Energy Florida [Member] | Noncurrent Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	11
Duke Energy Florida [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	9	12
Duke Energy Florida [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	5	37
Location and fair value amounts of derivatives (Liability)	9	12
Duke Energy Florida [Member] | Interest Rate Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	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)	4	26
Duke Energy Florida [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	11
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)	9	12
Duke Energy Florida [Member] | 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	2
Duke Energy Ohio [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	2	5
Location and fair value amounts of derivatives (Liability)	5	6
Duke Energy Ohio [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	2	4
Duke Energy Ohio [Member] | Noncurrent Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)		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)	4	5
Duke Energy Ohio [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	2	5
Duke Energy Ohio [Member] | Interest Rate Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	5	6
Duke Energy Ohio [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	2	4
Duke Energy Ohio [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
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)	4	5
Duke Energy Indiana [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	28	16
Location and fair value amounts of derivatives (Liability)		2
Duke Energy Indiana [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	28	16
Duke Energy Indiana [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)		2
Duke Energy Indiana [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	28	16
Location and fair value amounts of derivatives (Liability)		2
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)	28	16
Duke Energy Indiana [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)		2
Piedmont Natural Gas [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	2	3
Location and fair value amounts of derivatives (Liability)	123	187
Piedmont Natural Gas [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	2	3
Piedmont Natural Gas [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	18	35
Piedmont Natural Gas [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	105	152
Piedmont Natural Gas [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	2	3
Location and fair value amounts of derivatives (Liability)	123	187
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)	2	3
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)	18	35
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)	$ 105	$ 152

Derivatives and Hedging (Schedu

Derivatives and Hedging (Schedule of Offsetting Assets) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	$ 69	$ 162
Net amounts recognized on the Condensed Consolidated Balance Sheet	69	162
Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	49	111
Gross amounts offset	(3)	(11)
Net amounts recognized on the Condensed Consolidated Balance Sheet	46	100
Noncurrent Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	20	51
Gross amounts offset	(2)	(2)
Net amounts recognized on the Condensed Consolidated Balance Sheet	18	49
Duke Energy Carolinas [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	8	33
Net amounts recognized on the Condensed Consolidated Balance Sheet	8	33
Duke Energy Carolinas [Member] | Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	6	23
Net amounts recognized on the Condensed Consolidated Balance Sheet	6	23
Duke Energy Carolinas [Member] | Noncurrent Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	2	10
Gross amounts offset	(1)	(1)
Net amounts recognized on the Condensed Consolidated Balance Sheet	1	9
Progress Energy [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	15	85
Net amounts recognized on the Condensed Consolidated Balance Sheet	15	85
Progress Energy [Member] | Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	11	64
Gross amounts offset	(3)	(11)
Net amounts recognized on the Condensed Consolidated Balance Sheet	8	53
Progress Energy [Member] | Noncurrent Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	4	21
Gross amounts offset	(1)	(1)
Net amounts recognized on the Condensed Consolidated Balance Sheet	3	20
Duke Energy Progress [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	8	46
Net amounts recognized on the Condensed Consolidated Balance Sheet	8	46
Duke Energy Progress [Member] | Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	5	36
Gross amounts offset	(1)
Net amounts recognized on the Condensed Consolidated Balance Sheet	4	36
Duke Energy Progress [Member] | Noncurrent Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	3	10
Gross amounts offset	(1)	(1)
Net amounts recognized on the Condensed Consolidated Balance Sheet	2	9
Duke Energy Florida [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	6	39
Net amounts recognized on the Condensed Consolidated Balance Sheet	6	39
Duke Energy Florida [Member] | Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	5	28
Gross amounts offset	(2)	(11)
Net amounts recognized on the Condensed Consolidated Balance Sheet	3	17
Duke Energy Florida [Member] | Noncurrent Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	1	11
Net amounts recognized on the Condensed Consolidated Balance Sheet	1	11
Duke Energy Ohio [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	2	5
Net amounts recognized on the Condensed Consolidated Balance Sheet	2	5
Duke Energy Ohio [Member] | Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	2	4
Net amounts recognized on the Condensed Consolidated Balance Sheet	2	4
Duke Energy Ohio [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 Indiana [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	28	16
Net amounts recognized on the Condensed Consolidated Balance Sheet	28	16
Duke Energy Indiana [Member] | Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	28	16
Net amounts recognized on the Condensed Consolidated Balance Sheet	28	16
Piedmont Natural Gas [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	2	3
Net amounts recognized on the Condensed Consolidated Balance Sheet	2	3
Piedmont Natural Gas [Member] | Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	2	3
Net amounts recognized on the Condensed Consolidated Balance Sheet	$ 2	$ 3

Derivatives and Hedging (Sche76

Derivatives and Hedging (Schedule of Offsetting Liabilities) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	$ 191	$ 252
Net amounts recognized on the Condensed Consolidated Balance Sheet	191	252
Other Current Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	60	52
Gross amounts offset	(4)	(11)
Net amounts recognized on the Condensed Consolidated Balance Sheet	56	41
Other Noncurrent Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	131	200
Gross amounts offset	(2)	(2)
Net amounts recognized on the Condensed Consolidated Balance Sheet	129	198
Duke Energy Carolinas [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	25	16
Net amounts recognized on the Condensed Consolidated Balance Sheet	25	16
Duke Energy Carolinas [Member] | Other Current Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	24
Gross amounts offset	(1)
Net amounts recognized on the Condensed Consolidated Balance Sheet	23
Duke Energy Carolinas [Member] | Other Noncurrent Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	1	16
Gross amounts offset	(1)	(1)
Net amounts recognized on the Condensed Consolidated Balance Sheet		15
Progress Energy [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	22	25
Net amounts recognized on the Condensed Consolidated Balance Sheet	22	25
Progress Energy [Member] | Other Current Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	11	12
Gross amounts offset	(3)	(11)
Net amounts recognized on the Condensed Consolidated Balance Sheet	8	1
Progress Energy [Member] | Other Noncurrent Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	11	13
Gross amounts offset	(1)	(1)
Net amounts recognized on the Condensed Consolidated Balance Sheet	10	12
Duke Energy Progress [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	7	7
Net amounts recognized on the Condensed Consolidated Balance Sheet	7	7
Duke Energy Progress [Member] | Other Current Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	2
Gross amounts offset	(1)
Net amounts recognized on the Condensed Consolidated Balance Sheet	1
Duke Energy Progress [Member] | Other Noncurrent Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	5	7
Gross amounts offset	(1)	(1)
Net amounts recognized on the Condensed Consolidated Balance Sheet	4	6
Duke Energy Florida [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	9	12
Net amounts recognized on the Condensed Consolidated Balance Sheet	9	12
Duke Energy Florida [Member] | Other Current Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	9	12
Gross amounts offset	(2)	(11)
Net amounts recognized on the Condensed Consolidated Balance Sheet	7	1
Duke Energy Ohio [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	5	6
Net amounts recognized on the Condensed Consolidated Balance Sheet	5	6
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	4	5
Net amounts recognized on the Condensed Consolidated Balance Sheet	4	5
Duke Energy Indiana [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized		2
Net amounts recognized on the Condensed Consolidated Balance Sheet		2
Duke Energy Indiana [Member] | Other Current Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized		2
Net amounts recognized on the Condensed Consolidated Balance Sheet		2
Piedmont Natural Gas [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	123	187
Net amounts recognized on the Condensed Consolidated Balance Sheet	123	187
Piedmont Natural Gas [Member] | Other Current Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	18	35
Net amounts recognized on the Condensed Consolidated Balance Sheet	18	35
Piedmont Natural Gas [Member] | Other Noncurrent Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	105	152
Net amounts recognized on the Condensed Consolidated Balance Sheet	$ 105	$ 152

Derivatives and Hedging (Deriva

Derivatives and Hedging (Derivative Instruments with Credit-Risk Related Contingent Features and Cash Collateral) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
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	$ 40	$ 34
Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered	40	34
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	25	16
Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered	25	16
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	15	18
Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered	15	18
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	6	6
Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered	6	6
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	9	12
Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered	$ 9	$ 12

Investments in Debt and Equit78

Investments in Debt and Equity Securities (Narrative) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading Securities	$ 1	$ 5
Piedmont Natural Gas [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading Securities	$ 1	$ 5

Investments in Debt and Equit79

Investments in Debt and Equity Securities (Available-For-Sale Investments) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	$ 2,636	$ 2,156
Gross Unrealized Holding Losses	38	88
Estimated Fair Value	7,152	6,554
Ndtf [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	2,580	2,115
Gross Unrealized Holding Losses	37	83
Estimated Fair Value	6,794	6,184
Ndtf [Member] | Cash and Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value	129	111
Ndtf [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	2,549	2,092
Gross Unrealized Holding Losses	28	54
Estimated Fair Value	4,627	4,106
Ndtf [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	16	10
Gross Unrealized Holding Losses	2	8
Estimated Fair Value	600	528
Ndtf [Member] | Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	5	3
Gross Unrealized Holding Losses	2	10
Estimated Fair Value	334	331
Ndtf [Member] | US Treasury and Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	10	10
Gross Unrealized Holding Losses	4	8
Estimated Fair Value	984	984
Ndtf [Member] | Other Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Losses	1	3
Estimated Fair Value	120	124
Other Classification [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	56	41
Gross Unrealized Holding Losses	1	5
Estimated Fair Value	358	370
Other Classification [Member] | Cash and Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value	15	25
Other Classification [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	52	38
Estimated Fair Value	115	104
Other Classification [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	1	1
Gross Unrealized Holding Losses		1
Estimated Fair Value	64	66
Other Classification [Member] | Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	3	2
Gross Unrealized Holding Losses	1	1
Estimated Fair Value	83	82
Other Classification [Member] | US Treasury and Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Losses		1
Estimated Fair Value	44	51
Other Classification [Member] | Other Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Losses		2
Estimated Fair Value	37	42
Duke Energy Carolinas [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	1,408	1,165
Gross Unrealized Holding Losses	20	45
Estimated Fair Value	3,613	3,261
Duke Energy Carolinas [Member] | Ndtf [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	1,408	1,165
Gross Unrealized Holding Losses	20	44
Estimated Fair Value	3,613	3,258
Duke Energy Carolinas [Member] | Ndtf [Member] | Cash and Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value	34	18
Duke Energy Carolinas [Member] | Ndtf [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	1,395	1,157
Gross Unrealized Holding Losses	14	28
Estimated Fair Value	2,553	2,245
Duke Energy Carolinas [Member] | Ndtf [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	9	5
Gross Unrealized Holding Losses	2	6
Estimated Fair Value	395	354
Duke Energy Carolinas [Member] | Ndtf [Member] | Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	1	1
Gross Unrealized Holding Losses		2
Estimated Fair Value	52	67
Duke Energy Carolinas [Member] | Ndtf [Member] | US Treasury and Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	3	2
Gross Unrealized Holding Losses	3	5
Estimated Fair Value	466	458
Duke Energy Carolinas [Member] | Ndtf [Member] | Other Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Losses	1	3
Estimated Fair Value	113	116
Duke Energy Carolinas [Member] | Other Classification [Member] | Other Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Losses		1
Estimated Fair Value		3
Progress Energy [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	1,175	952
Gross Unrealized Holding Losses	17	39
Estimated Fair Value	3,239	2,991
Progress Energy [Member] | Ndtf [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	1,172	950
Gross Unrealized Holding Losses	17	39
Estimated Fair Value	3,181	2,926
Progress Energy [Member] | Ndtf [Member] | Cash and Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value	95	93
Progress Energy [Member] | Ndtf [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	1,154	935
Gross Unrealized Holding Losses	14	26
Estimated Fair Value	2,074	1,861
Progress Energy [Member] | Ndtf [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	7	5
Gross Unrealized Holding Losses		2
Estimated Fair Value	205	174
Progress Energy [Member] | Ndtf [Member] | Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	4	2
Gross Unrealized Holding Losses	2	8
Estimated Fair Value	282	264
Progress Energy [Member] | Ndtf [Member] | US Treasury and Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	7	8
Gross Unrealized Holding Losses	1	3
Estimated Fair Value	518	526
Progress Energy [Member] | Ndtf [Member] | Other Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value	7	8
Progress Energy [Member] | Other Classification [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	3	2
Estimated Fair Value	58	65
Progress Energy [Member] | Other Classification [Member] | Cash and Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value	11	21
Progress Energy [Member] | Other Classification [Member] | Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	3	2
Estimated Fair Value	47	44
Duke Energy Progress [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	896	715
Gross Unrealized Holding Losses	14	32
Estimated Fair Value	2,462	2,214
Duke Energy Progress [Member] | Ndtf [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	896	715
Gross Unrealized Holding Losses	14	32
Estimated Fair Value	2,461	2,213
Duke Energy Progress [Member] | Ndtf [Member] | Cash and Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value	46	45
Duke Energy Progress [Member] | Ndtf [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	882	704
Gross Unrealized Holding Losses	11	21
Estimated Fair Value	1,683	1,505
Duke Energy Progress [Member] | Ndtf [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	5	4
Gross Unrealized Holding Losses		1
Estimated Fair Value	144	120
Duke Energy Progress [Member] | Ndtf [Member] | Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	4	2
Gross Unrealized Holding Losses	2	8
Estimated Fair Value	281	263
Duke Energy Progress [Member] | Ndtf [Member] | US Treasury and Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	5	5
Gross Unrealized Holding Losses	1	2
Estimated Fair Value	303	275
Duke Energy Progress [Member] | Ndtf [Member] | Other Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value	4	5
Duke Energy Progress [Member] | Other Classification [Member] | Cash and Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value	1	1
Duke Energy Florida [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	279	237
Gross Unrealized Holding Losses	3	7
Estimated Fair Value	767	761
Duke Energy Florida [Member] | Ndtf [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	276	235
Gross Unrealized Holding Losses	3	7
Estimated Fair Value	720	713
Duke Energy Florida [Member] | Ndtf [Member] | Cash and Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value	49	48
Duke Energy Florida [Member] | Ndtf [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	272	231
Gross Unrealized Holding Losses	3	5
Estimated Fair Value	391	356
Duke Energy Florida [Member] | Ndtf [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	2	1
Gross Unrealized Holding Losses		1
Estimated Fair Value	61	54
Duke Energy Florida [Member] | Ndtf [Member] | Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value	1	1
Duke Energy Florida [Member] | Ndtf [Member] | US Treasury and Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	2	3
Gross Unrealized Holding Losses		1
Estimated Fair Value	215	251
Duke Energy Florida [Member] | Ndtf [Member] | Other Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value	3	3
Duke Energy Florida [Member] | Other Classification [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	3	2
Estimated Fair Value	47	48
Duke Energy Florida [Member] | Other Classification [Member] | Cash and Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value		4
Duke Energy Florida [Member] | Other Classification [Member] | Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	3	2
Estimated Fair Value	47	44
Duke Energy Indiana [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	44	33
Gross Unrealized Holding Losses	1	1
Estimated Fair Value	122	110
Duke Energy Indiana [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Gains	44	33
Estimated Fair Value	91	79
Duke Energy Indiana [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value	3	2
Duke Energy Indiana [Member] | Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Holding Losses	1	1
Estimated Fair Value	$ 28	28
Duke Energy Indiana [Member] | US Treasury and Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value		$ 1

Investments in Debt and Equit80

Investments in Debt and Equity Securities (Maturities) (Details) $ in Millions	Sep. 30, 2017USD ($)
Debt Instrument [Line Items]
Due in one year or less	$ 92
Due after one through five years	584
Due after five through 10 years	514
Due after 10 years	1,076
Total	2,266
Duke Energy Carolinas [Member]
Debt Instrument [Line Items]
Due in one year or less	5
Due after one through five years	218
Due after five through 10 years	264
Due after 10 years	539
Total	1,026
Progress Energy [Member]
Debt Instrument [Line Items]
Due in one year or less	74
Due after one through five years	309
Due after five through 10 years	194
Due after 10 years	482
Total	1,059
Duke Energy Progress [Member]
Debt Instrument [Line Items]
Due in one year or less	16
Due after one through five years	209
Due after five through 10 years	136
Due after 10 years	371
Total	732
Duke Energy Florida [Member]
Debt Instrument [Line Items]
Due in one year or less	58
Due after one through five years	100
Due after five through 10 years	58
Due after 10 years	111
Total	327
Duke Energy Indiana [Member]
Debt Instrument [Line Items]
Due in one year or less	4
Due after one through five years	12
Due after five through 10 years	8
Due after 10 years	7
Total	$ 31

Investments in Debt and Equit81

Investments in Debt and Equity Securities (Realized Gains and Losses)(Details) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Realized gains	$ 37	$ 82	$ 170	$ 200
Realized losses	25	42	124	134
Duke Energy Carolinas [Member]
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Realized gains	20	58	110	125
Realized losses	13	28	76	84
Progress Energy [Member]
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Realized gains	16	21	58	71
Realized losses	12	13	47	49
Duke Energy Progress [Member]
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Realized gains	14	18	49	60
Realized losses	11	11	41	42
Duke Energy Florida [Member]
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Realized gains	2	3	9	11
Realized losses	$ 1	$ 2	$ 6	$ 7

Fair Value Measurements (Fair V

Fair Value Measurements (Fair Value Measurement Amounts for Assets and Liabilities) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Alternative Investment, Fair Value Disclosure	$ 78	$ 77
Derivative assets	69	162
Total assets	7,222	6,716
Derivative liabilities	(191)	(252)
Net assets (liabilities)	7,031	6,464
Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	4	5
Total assets	5,345	4,845
Derivative liabilities	0	(2)
Net assets (liabilities)	5,345	4,843
Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	35	136
Total assets	1,769	1,768
Derivative liabilities	(68)	(63)
Net assets (liabilities)	1,701	1,705
Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	30	21
Total assets	30	26
Derivative liabilities	(123)	(187)
Net assets (liabilities)	(93)	(161)
Equity Securities [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Alternative Investment, Fair Value Disclosure	78	77
Investments	4,627	4,106
Equity Securities [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	4,549	4,029
Equity Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	116	104
Equity Securities [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	116	104
Debt Securities [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	2,167	2,078
Debt Securities [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	617	632
Debt Securities [Member] | Ndtf [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1,550	1,446
Debt Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	243	266
Debt Securities [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	59	75
Debt Securities [Member] | Other Classification [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	184	186
Debt Securities [Member] | Other Classification [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		5
Duke Energy Carolinas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Alternative Investment, Fair Value Disclosure	78	77
Derivative assets	8	33
Total assets	3,621	3,294
Derivative liabilities	(25)	(16)
Net assets (liabilities)	3,596	3,278
Duke Energy Carolinas [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0
Total assets	2,653	2,346
Derivative liabilities	0
Net assets (liabilities)	2,653	2,346
Duke Energy Carolinas [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	8	33
Total assets	890	868
Derivative liabilities	(25)	(16)
Net assets (liabilities)	865	852
Duke Energy Carolinas [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets		3
Net assets (liabilities)		3
Duke Energy Carolinas [Member] | Equity Securities [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Alternative Investment, Fair Value Disclosure	78	77
Investments	2,553	2,245
Duke Energy Carolinas [Member] | Equity Securities [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	2,475	2,168
Duke Energy Carolinas [Member] | Debt Securities [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1,060	1,013
Duke Energy Carolinas [Member] | Debt Securities [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	178	178
Duke Energy Carolinas [Member] | Debt Securities [Member] | Ndtf [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	882	835
Duke Energy Carolinas [Member] | Debt Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		3
Duke Energy Carolinas [Member] | Debt Securities [Member] | Other Classification [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		3
Progress Energy [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	15	85
Total assets	3,254	3,076
Derivative liabilities	(22)	(25)
Net assets (liabilities)	3,232	3,051
Progress Energy [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	1
Total assets	2,525	2,336
Derivative liabilities	0
Net assets (liabilities)	2,525	2,336
Progress Energy [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	14	85
Total assets	729	740
Derivative liabilities	(22)	(25)
Net assets (liabilities)	707	715
Progress Energy [Member] | Equity Securities [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	2,074	1,861
Progress Energy [Member] | Equity Securities [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	2,074	1,861
Progress Energy [Member] | Debt Securities [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1,107	1,065
Progress Energy [Member] | Debt Securities [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	439	454
Progress Energy [Member] | Debt Securities [Member] | Ndtf [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	668	611
Progress Energy [Member] | Debt Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	58	65
Progress Energy [Member] | Debt Securities [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	11	21
Progress Energy [Member] | Debt Securities [Member] | Other Classification [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	47	44
Duke Energy Progress [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	8	46
Total assets	2,470	2,260
Derivative liabilities	(7)	(7)
Net assets (liabilities)	2,463	2,253
Duke Energy Progress [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	1
Total assets	1,916	1,713
Derivative liabilities	0
Net assets (liabilities)	1,916	1,713
Duke Energy Progress [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	7	46
Total assets	554	547
Derivative liabilities	(7)	(7)
Net assets (liabilities)	547	540
Duke Energy Progress [Member] | Equity Securities [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1,683	1,505
Duke Energy Progress [Member] | Equity Securities [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1,683	1,505
Duke Energy Progress [Member] | Debt Securities [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	778	708
Duke Energy Progress [Member] | Debt Securities [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	231	207
Duke Energy Progress [Member] | Debt Securities [Member] | Ndtf [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	547	501
Duke Energy Progress [Member] | Debt Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1	1
Duke Energy Progress [Member] | Debt Securities [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1	1
Duke Energy Florida [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	6	39
Total assets	773	800
Derivative liabilities	(9)	(12)
Net assets (liabilities)	764	788
Duke Energy Florida [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	599	607
Net assets (liabilities)	599	607
Duke Energy Florida [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	6	39
Total assets	174	193
Derivative liabilities	(9)	(12)
Net assets (liabilities)	165	181
Duke Energy Florida [Member] | Equity Securities [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	391	356
Duke Energy Florida [Member] | Equity Securities [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	391	356
Duke Energy Florida [Member] | Debt Securities [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	329	357
Duke Energy Florida [Member] | Debt Securities [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	208	247
Duke Energy Florida [Member] | Debt Securities [Member] | Ndtf [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	121	110
Duke Energy Florida [Member] | Debt Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	47	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		4
Duke Energy Florida [Member] | Debt Securities [Member] | Other Classification [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	47	44
Duke Energy Ohio [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	2	5
Derivative liabilities	(5)	(6)
Net assets (liabilities)	(3)	(1)
Duke Energy Ohio [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilities	(5)	(6)
Net assets (liabilities)	(5)	(6)
Duke Energy Ohio [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	2	5
Net assets (liabilities)	2	5
Duke Energy Indiana [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	28	16
Total assets	150	126
Derivative liabilities		(2)
Net assets (liabilities)	150	124
Duke Energy Indiana [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0
Total assets	91	79
Derivative liabilities	0	(2)
Net assets (liabilities)	91	77
Duke Energy Indiana [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	31	31
Net assets (liabilities)	31	31
Duke Energy Indiana [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	28	16
Total assets	28	16
Net assets (liabilities)	28	16
Duke Energy Indiana [Member] | Equity Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	91	79
Duke Energy Indiana [Member] | Equity Securities [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	91	79
Duke Energy Indiana [Member] | Debt Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	31	31
Duke Energy Indiana [Member] | Debt Securities [Member] | Other Classification [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	31	31
Piedmont Natural Gas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	2	3
Total assets	3	8
Derivative liabilities	(123)	(187)
Net assets (liabilities)	(120)	(179)
Piedmont Natural Gas [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	2	3
Total assets	3	8
Net assets (liabilities)	3	8
Piedmont Natural Gas [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilities	(123)	(187)
Net assets (liabilities)	(123)	(187)
Piedmont Natural Gas [Member] | Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1	4
Piedmont Natural Gas [Member] | Equity Securities [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	$ 1	4
Piedmont Natural Gas [Member] | Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		1
Piedmont Natural Gas [Member] | Debt Securities [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		$ 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, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
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)
Beginning balance	(91,000,000)	34,000,000	(166,000,000)	10,000,000
Purchases			55,000,000	34,000,000
Settlements	(12,000,000)	(9,000,000)	(30,000,000)	(22,000,000)
Total gains (losses) included on the Condensed Consolidated Balance Sheet	10,000,000	(2,000,000)	48,000,000	1,000,000
Ending balance	(93,000,000)	23,000,000	(93,000,000)	23,000,000
Investments and Derivatives, Net
Beginning balance	(91,000,000)	38,000,000	(161,000,000)	15,000,000
Total pretax realized or unrealized gains included in comprehensive income			1,000,000
Purchases			55,000,000	34,000,000
Sales			(6,000,000)	(1,000,000)
Settlements	(12,000,000)	(9,000,000)	(30,000,000)	(22,000,000)
Total gains (losses) included on the Condensed Consolidated Balance Sheet	10,000,000	(2,000,000)	48,000,000	1,000,000
Ending balance	(93,000,000)	27,000,000	(93,000,000)	27,000,000
Investments [Member]
Investments
Beginning balance		4,000,000	5,000,000	5,000,000
Total pretax realized or unrealized gains included in comprehensive income			1,000,000
Sales			(6,000,000)	(1,000,000)
Ending balance		4,000,000		4,000,000
Duke Energy Carolinas [Member] | Investments [Member]
Investments
Beginning balance		3,000,000	3,000,000	3,000,000
Total pretax realized or unrealized gains included in comprehensive income			1,000,000
Sales			(4,000,000)
Ending balance		3,000,000		3,000,000
Duke Energy Ohio [Member]
Derivatives (net)
Beginning balance	3,000,000	5,000,000	5,000,000	3,000,000
Purchases			3,000,000	5,000,000
Settlements	(1,000,000)	(2,000,000)	(3,000,000)	(4,000,000)
Total gains (losses) included on the Condensed Consolidated Balance Sheet			(3,000,000)	(1,000,000)
Ending balance	2,000,000	3,000,000	2,000,000	3,000,000
Duke Energy Indiana [Member]
Derivatives (net)
Beginning balance	51,000,000	29,000,000	16,000,000	7,000,000
Purchases			52,000,000	29,000,000
Settlements	(11,000,000)	(7,000,000)	(27,000,000)	(18,000,000)
Total gains (losses) included on the Condensed Consolidated Balance Sheet	(12,000,000)	(2,000,000)	(13,000,000)	2,000,000
Ending balance	28,000,000	20,000,000	28,000,000	20,000,000
Piedmont Natural Gas [Member]
Derivatives (net)
Beginning balance	(145,000,000)	(190,000,000)	(187,000,000)	(149,000,000)
Total gains (losses) and settlements	22,000,000	(5,000,000)	64,000,000	(46,000,000)
Ending balance	$ (123,000,000)	$ (195,000,000)	$ (123,000,000)	$ (195,000,000)

Fair Value Measurements (Quanti

Fair Value Measurements (Quantitative Level 3 Fair Value Disclosure - Assets) (Details) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2017USD ($)$ / MWh	Dec. 31, 2016USD ($)$ / MWh	Jun. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Jun. 30, 2016USD ($)	Dec. 31, 2015USD ($)
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Net derivative asset (liability)	$ (93)	$ (166)	$ (91)	$ 23	$ 34	$ 10
Duke Energy Ohio [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Net derivative asset (liability)	2	5	3	3	5	3
Duke Energy Ohio [Member] | Financial Transmission Rights [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Net derivative asset (liability)	$ 2	$ 5
Duke Energy Ohio [Member] | Financial Transmission Rights [Member] | Minimum [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Input Price Per Unit | $ / MWh		0.77
Duke Energy Ohio [Member] | Financial Transmission Rights [Member] | Maximum [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Input Price Per Unit | $ / MWh	1.08	3.52
Duke Energy Indiana [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Net derivative asset (liability)	$ 28	$ 16	$ 51	$ 20	$ 29	$ 7
Duke Energy Indiana [Member] | Financial Transmission Rights [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Net derivative asset (liability)	$ 28	$ 16
Duke Energy Indiana [Member] | Financial Transmission Rights [Member] | Minimum [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Input Price Per Unit | $ / MWh	(0.82)	(0.83)
Duke Energy Indiana [Member] | Financial Transmission Rights [Member] | Maximum [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Input Price Per Unit | $ / MWh	6.19	9.32

Fair Value Measurements (Quan85

Fair Value Measurements (Quantitative Level 3 Fair Value Disclosure - Liabilities) (Details) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2017USD ($)$ / MMBTU	Dec. 31, 2016USD ($)$ / MMBTU	Jun. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Jun. 30, 2016USD ($)	Dec. 31, 2015USD ($)
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Net derivative asset (liability)	$ (93)	$ (166)	$ (91)	$ 23	$ 34	$ 10
Duke Energy Indiana [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Net derivative asset (liability)	28	16	51	20	29	7
Duke Energy Ohio [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Net derivative asset (liability)	2	5	3	3	5	3
Piedmont Natural Gas [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Net derivative asset (liability)	(123)	(187)	$ (145)	$ (195)	$ (190)	$ (149)
Derivative Financial Instruments, Liabilities [Member] | Discounted Cash Flow [Member] | Piedmont Natural Gas [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Net derivative asset (liability)	$ (123)	$ (187)
Derivative Financial Instruments, Liabilities [Member] | Minimum [Member] | Discounted Cash Flow [Member] | Piedmont Natural Gas [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Fair Value Input Price Per Unit | $ / MMBTU	2.12	2.31
Derivative Financial Instruments, Liabilities [Member] | Maximum [Member] | Discounted Cash Flow [Member] | Piedmont Natural Gas [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Fair Value Input Price Per Unit | $ / MMBTU	3.36	4.18

Fair Value Measurements (Additi

Fair Value Measurements (Additional Fair Value Disclosure) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	$ 51,414	$ 47,895
Long-term debt, fair value	53,985	49,161
Duke Energy Carolinas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	9,525	9,603
Long-term debt, fair value	10,653	10,494
Progress Energy [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	17,637	17,541
Long-term debt, fair value	19,615	19,107
Duke Energy Progress [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	7,557	7,011
Long-term debt, fair value	8,075	7,357
Duke Energy Florida [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	6,696	6,125
Long-term debt, fair value	7,475	6,728
Duke Energy Ohio [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	2,067	1,884
Long-term debt, fair value	2,242	2,020
Duke Energy Indiana [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	3,785	3,786
Long-term debt, fair value	4,407	4,260
Piedmont Natural Gas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	2,036	1,821
Long-term debt, fair value	$ 2,193	$ 1,933

Variable Interest Entities (Nar

Variable Interest Entities (Narrative) (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016	Jun. 30, 2016
Variable Interest Entities [Line Items]
Debt Instrument, Face Amount	$ 5,120,000,000
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 Progress [Member]
Variable Interest Entities [Line Items]
Debt Instrument, Face Amount	$ 800,000,000
Duke Energy Florida [Member]
Variable Interest Entities [Line Items]
Debt Instrument, Face Amount	900,000,000
Duke Energy Florida [Member] | DEFPF [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Debt Instrument, Face Amount			$ 1,294,000,000
Duke Energy Ohio [Member]
Variable Interest Entities [Line Items]
Debt Instrument, Face Amount	$ 100,000,000
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, 2017	Dec. 31, 2016
Variable Interest Entities [Line Items]
Long-Term Debt	$ 48,929	$ 45,576
Duke Energy Carolinas [Member]
Variable Interest Entities [Line Items]
Long-Term Debt	8,520	9,187
Duke Energy Progress [Member]
Variable Interest Entities [Line Items]
Long-Term Debt	7,204	6,409
Duke Energy Florida [Member]
Variable Interest Entities [Line Items]
Long-Term Debt	$ 6,129	5,799
Cinergy Receivables [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Line of Credit Facility, Expiration Date	Dec. 1, 2018
Facility size	$ 325
Long-Term Debt	$ 325	325
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, 2018
Facility size	$ 425
Long-Term Debt	$ 425	425
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, 2019
Facility size	$ 300
Long-Term Debt	$ 300	300
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, 2019
Facility size	$ 225
Long-Term Debt	$ 225	$ 225

Variable Interest Entities (S89

Variable Interest Entities (Schedule of Consolidated VIEs) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Regulatory assets, current	$ 1,109	$ 1,023
Other, current assets	433	458
Regulatory assets, noncurrent	13,367	12,878
Property, plant and equipment, cost	125,582	121,397
Accumulated depreciation and amortization	(41,161)	(39,406)
Current Liabilities: Other	1,734	2,044
Current maturities of long-term debt	2,485	2,319
Long-Term Debt	48,929	45,576
Deferred income taxes	15,058	14,155
Noncurrent Liabilities: Other	1,624	1,753
Duke Energy Carolinas [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Regulatory assets, current	237	238
Other, current assets	27	37
Regulatory assets, noncurrent	3,077	3,159
Property, plant and equipment, cost	42,321	41,127
Accumulated depreciation and amortization	(14,969)	(14,365)
Current Liabilities: Other	435	468
Current maturities of long-term debt	705	116
Long-Term Debt	8,520	9,187
Deferred income taxes	6,796	6,544
Noncurrent Liabilities: Other	559	607
Duke Energy Progress [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Regulatory assets, current	230	188
Other, current assets	40	57
Regulatory assets, noncurrent	3,588	3,243
Property, plant and equipment, cost	29,104	28,419
Accumulated depreciation and amortization	(10,793)	(10,561)
Current Liabilities: Other	318	365
Current maturities of long-term debt	203	452
Long-Term Debt	7,204	6,409
Deferred income taxes	3,606	3,323
Noncurrent Liabilities: Other	44	51
Duke Energy Florida [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Regulatory assets, current	211	213
Other, current assets	154	125
Regulatory assets, noncurrent	2,850	2,480
Property, plant and equipment, cost	17,546	16,434
Accumulated depreciation and amortization	(4,960)	(4,644)
Current Liabilities: Other	310	352
Current maturities of long-term debt	567	326
Long-Term Debt	6,129	5,799
Deferred income taxes	3,076	2,694
Noncurrent Liabilities: Other	106	105
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	6	6
Regulatory assets, current	51	50
Other, current assets	20	53
Regulatory assets, noncurrent	1,101	1,142
Current Liabilities: Other	3	17
Current maturities of long-term debt	53	62
Long-Term Debt	1,164	1,217
DERF [Member] | Duke Energy Carolinas [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Long-Term Debt	425	425
DEPR [Member] | Duke Energy Progress [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Long-Term Debt	300	300
DEFR [Member] | Duke Energy Florida [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Long-Term Debt	225	225
Cinergy Receivables [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Long-Term Debt	325	325
Renewables [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Other, current assets	399	223
Property, plant and equipment, cost	3,923	3,419
Accumulated depreciation and amortization	(556)	(453)
Current maturities of long-term debt	162	198
Long-Term Debt	1,780	1,097
Deferred income taxes	223	275
Noncurrent Liabilities: Other	$ 247	$ 252

Variable Interest Entities (S90

Variable Interest Entities (Schedule of Non-Consolidated VIEs) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Variable Interest Entities [Line Items]
Investments in equity method unconsolidated affiliates	$ 1,366	$ 925
Other noncurrent assets	2,792	2,769
Taxes accrued	627	384
Current Liabilities: Other	1,734	2,044
Deferred income taxes	15,058	14,155
Noncurrent Liabilities: Other	1,624	1,753
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Investments in equity method unconsolidated affiliates	1,106	751
Other noncurrent assets	18	12
Total assets	1,124	763
Current Liabilities: Other	3	3
Deferred income taxes	29
Noncurrent Liabilities: Other	12	13
Total liabilities	44	16
Net assets	1,080	747
Pipeline Investments [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Investments in equity method unconsolidated affiliates	895	487
Other noncurrent assets	18	12
Total assets	913	499
Deferred income taxes	29
Total liabilities	29
Net assets	884	499
Renewables [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Investments in equity method unconsolidated affiliates	172	174
Total assets	172	174
Net assets	172	174
Other VIEs [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Investments in equity method unconsolidated affiliates	39	90
Total assets	39	90
Current Liabilities: Other	3	3
Noncurrent Liabilities: Other	12	13
Total liabilities	15	16
Net assets	24	74
Duke Energy Ohio [Member]
Variable Interest Entities [Line Items]
Receivables from affiliated companies	81	129
Other noncurrent assets	27	23
Taxes accrued	157	178
Current Liabilities: Other	74	91
Deferred income taxes	1,512	1,443
Noncurrent Liabilities: Other	134	166
Duke Energy Ohio [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Receivables from affiliated companies	46	82
Total assets	46	82
Net assets	46	82
Duke Energy Indiana [Member]
Variable Interest Entities [Line Items]
Receivables from affiliated companies	83	114
Other noncurrent assets	170	147
Taxes accrued	146	31
Current Liabilities: Other	111	93
Deferred income taxes	1,979	1,900
Noncurrent Liabilities: Other	65	27
Duke Energy Indiana [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Receivables from affiliated companies	75	101
Total assets	75	101
Net assets	75	101
Piedmont Natural Gas [Member]
Variable Interest Entities [Line Items]
Receivables from affiliated companies	8	7
Investments in equity method unconsolidated affiliates	76	212
Other noncurrent assets	11	21
Taxes accrued	30	67
Current Liabilities: Other	72	102
Deferred income taxes	1,046	931
Noncurrent Liabilities: Other	$ 141	189
Piedmont Natural Gas [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Investments in equity method unconsolidated affiliates		139
Total assets		139
Noncurrent Liabilities: Other		4
Total liabilities		4
Net assets		$ 135

Variable Interest Entities Vari

Variable Interest Entities Variable Interest Entities (Joint-Venture Ownership Information) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Investments in equity method unconsolidated affiliates	$ 1,366	$ 925
Duke American Transmission Company [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	50.00%
Investments in equity method unconsolidated affiliates	$ 45

Variable Interest Entities (Pip

Variable Interest Entities (Pipeline Investments) (Details) - USD ($)	Dec. 31, 2016	Oct. 31, 2017	Sep. 30, 2017
Variable Interest Entities [Line Items]
Investments in Joint Ventures	$ 925,000,000		$ 1,366,000,000
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Liabilities	16,000,000		44,000,000
Investments in Joint Ventures	751,000,000		$ 1,106,000,000
Variable Interest Entity, Not Primary Beneficiary [Member] | Atlantic Coast Pipeline [Member]
Variable Interest Entities [Line Items]
Variable Interest Entity Ownership Interest			47.00%
Investments in Joint Ventures	265,000,000		$ 595,000,000
Variable Interest Entity, Not Primary Beneficiary [Member] | Sabal Trail Transmission Pipeline [Member]
Variable Interest Entities [Line Items]
Variable Interest Entity Ownership Interest			7.50%
Investments in Joint Ventures	140,000,000		$ 218,000,000
Variable Interest Entity, Not Primary Beneficiary [Member] | Constitution Pipeline [Member]
Variable Interest Entities [Line Items]
Variable Interest Entity Ownership Interest			24.00%
Investments in Joint Ventures	82,000,000		$ 82,000,000
Variable Interest Entity, Not Primary Beneficiary [Member] | Pipeline Investments [Member]
Variable Interest Entities [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Liabilities			29,000,000
Investments in Joint Ventures	487,000,000		895,000,000
Piedmont Natural Gas [Member]
Variable Interest Entities [Line Items]
Investments in Joint Ventures	212,000,000		$ 76,000,000
Piedmont Natural Gas [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Liabilities	4,000,000
Investments in Joint Ventures	$ 139,000,000
Piedmont Natural Gas [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Atlantic Coast Pipeline [Member]
Variable Interest Entities [Line Items]
Variable Interest Entity Ownership Interest	7.00%
Piedmont Natural Gas [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Constitution Pipeline [Member]
Variable Interest Entities [Line Items]
Variable Interest Entity Ownership Interest	24.00%
Subsequent Event [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Atlantic Coast Pipeline [Member]
Variable Interest Entities [Line Items]
Variable Interest Entity Not Consolidated Line Of Credit Facility Maximum Borrowing Capacity		$ 3,400,000,000
Subsequent Event [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Atlantic Coast Pipeline [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		$ 570,000,000

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, 2017	Sep. 30, 2016
Duke Energy Ohio [Member]
Variable Interest Entities [Line Items]
Anticipated credit loss ratio	0.50%	0.50%
Discount rate	2.00%	1.50%
Receivable turnover rate	13.40%	13.30%
Duke Energy Indiana [Member]
Variable Interest Entities [Line Items]
Anticipated credit loss ratio	0.30%	0.30%
Discount rate	2.00%	1.50%
Receivable turnover rate	10.70%	10.60%

Variable Interest Entities (Rec

Variable Interest Entities (Receivables Sold)(Details) - Variable Interest Entity, Not Primary Beneficiary [Member] - Cinergy Receivables [Member] - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Duke Energy Ohio [Member]
Variable Interest Entities [Line Items]
Receivables sold	$ 209	$ 267
Less: Retained interests	46	82
Net receivables sold	163	185
Duke Energy Indiana [Member]
Variable Interest Entities [Line Items]
Receivables sold	304	306
Less: Retained interests	75	101
Net receivables sold	$ 229	$ 205

Variable Interest Entities (Sal

Variable Interest Entities (Sales and Cash Flows)(Details) - Variable Interest Entity, Not Primary Beneficiary [Member] - Cinergy Receivables [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Duke Energy Ohio [Member]
Variable Interest Entities [Line Items]
Receivables sold	$ 438	$ 481	$ 1,392	$ 1,442
Loss recognized on sale	2	2	7	7
Cash proceeds from receivables sold	434	468	1,421	1,432
Collection fees received	1	1	1	1
Return received on retained interests	0	1	2	2
Duke Energy Indiana [Member]
Variable Interest Entities [Line Items]
Receivables sold	720	722	2,047	1,980
Loss recognized on sale	3	3	9	8
Cash proceeds from receivables sold	713	703	2,064	1,958
Collection fees received	0		1	1
Return received on retained interests	$ 2	$ 2	$ 5	$ 4

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, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Common Stock [Line Items]
Income from continuing operations attributable to Duke Energy common stockholders excluding impact of participating securities	$ 954	$ 998	$ 2,356	$ 2,194
Average shares, basic	700	689	700	689
Incremental Common Shares Attributable to Dilutive Effect of Equity Forward Agreements		2		1
Average shares, diluted	700	691	700	690
EPS, basic (usd per share)	$ 1.36	$ 1.44	$ 3.37	$ 3.19
EPS, diluted (usd per share)	$ 1.36	$ 1.44	$ 3.37	$ 3.18
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)	$ 0.89	$ 0.855	$ 2.6	$ 2.505

Common Stock (Equity Securities

Common Stock (Equity Securities Offering) (Details) - Piedmont Natural Gas [Member] - shares shares in Millions	Sep. 30, 2016	Mar. 31, 2016
Forward Contract Indexed to Issuer's Equity [Line Items]
Shares offered		10.6
Settlement Alternatives, Shares	10.6

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, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pretax stock-based compensation cost	$ 17	$ 12	$ 50	$ 39
Tax benefit associated with stock-based compensation expense	6	5	18	14
Stock-based compensation costs capitalized	1		2	2
Restricted Stock Units Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pretax stock-based compensation cost	10	8	30	25
Performance Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pretax stock-based compensation cost	$ 7	4	$ 20	14
Piedmont Natural Gas [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pretax stock-based compensation cost		$ 2		$ 5

Employee Benefit Plans (Plan Co

Employee Benefit Plans (Plan Contributions) (Details) - Qualified Pension Plan [Member] - USD ($)	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Employer Contributions, Current Fiscal Year	$ 19,000,000
Contributions by Employer	8,000,000	$ 0
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year	11,000,000
Duke Energy Ohio [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Employer Contributions, Current Fiscal Year	4,000,000
Contributions by Employer	4,000,000
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year	0
Piedmont Natural Gas [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Employer Contributions, Current Fiscal Year	11,000,000
Contributions by Employer	0
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year	$ 11,000,000

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, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Qualified Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 40	$ 36	$ 120	$ 109
Interest cost on projected benefit obligation	82	83	246	249
Expected return on plan assets	(136)	(128)	(408)	(386)
Amortization of actuarial loss (gain)	36	33	108	99
Amortization of prior service credit	(6)	(4)	(18)	(12)
Other	2	2	6	6
Net periodic costs	18	22	54	65
Qualified Pension Plan [Member] | Duke Energy Carolinas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	12	12	36	36
Interest cost on projected benefit obligation	20	21	60	64
Expected return on plan assets	(35)	(35)	(106)	(106)
Amortization of actuarial loss (gain)	8	8	24	24
Amortization of prior service credit	(2)	(2)	(6)	(6)
Other		1		2
Net periodic costs	3	5	8	14
Qualified Pension Plan [Member] | Progress Energy [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	12	11	36	32
Interest cost on projected benefit obligation	25	27	75	80
Expected return on plan assets	(43)	(42)	(129)	(126)
Amortization of actuarial loss (gain)	14	14	42	41
Amortization of prior service credit	(1)	(1)	(3)	(3)
Other	1	1	3	2
Net periodic costs	8	10	24	26
Qualified Pension Plan [Member] | Duke Energy Progress [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	6	6	18	18
Interest cost on projected benefit obligation	12	12	36	37
Expected return on plan assets	(21)	(21)	(63)	(62)
Amortization of actuarial loss (gain)	6	6	18	17
Amortization of prior service credit				(1)
Other			1	1
Net periodic costs	3	3	10	10
Qualified Pension Plan [Member] | Duke Energy Florida [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	5	4	15	14
Interest cost on projected benefit obligation	13	14	39	42
Expected return on plan assets	(21)	(21)	(63)	(63)
Amortization of actuarial loss (gain)	7	7	21	21
Amortization of prior service credit		(1)		(1)
Other		1		1
Net periodic costs	4	4	12	14
Qualified Pension Plan [Member] | Duke Energy Ohio [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	1	1	3	3
Interest cost on projected benefit obligation	4	5	14	15
Expected return on plan assets	(7)	(6)	(21)	(20)
Amortization of actuarial loss (gain)	1	1	3	3
Net periodic costs	(1)	1	(1)	1
Qualified Pension Plan [Member] | Duke Energy Indiana [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	2	2	6	6
Interest cost on projected benefit obligation	7	7	21	21
Expected return on plan assets	(11)	(10)	(33)	(31)
Amortization of actuarial loss (gain)	3	3	9	9
Net periodic costs	1	2	3	5
Qualified Pension Plan [Member] | Piedmont Natural Gas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	3	3	9	8
Interest cost on projected benefit obligation	3	2	9	7
Expected return on plan assets	(6)	(6)	(18)	(18)
Amortization of actuarial loss (gain)	3	2	9	6
Amortization of prior service credit	(1)	(1)	(3)	(2)
Other			1
Net periodic costs	2		7	1
Non-Qualified Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		1		2
Interest cost on projected benefit obligation	4	4	10	11
Amortization of actuarial loss (gain)	2	2	6	6
Amortization of prior service credit		(1)		(1)
Net periodic costs	6	6	16	18
Non-Qualified Pension Plan [Member] | Duke Energy Carolinas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost on projected benefit obligation			1	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	2	3	4
Amortization of actuarial loss (gain)	1	1	3	2
Net periodic costs	2	3	6	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		2	1
Amortization of actuarial loss (gain)		1		1
Net periodic costs	1	1	2	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		2	1
Amortization of actuarial loss (gain)		1		1
Net periodic costs	1	1	2	2
Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	1		3	2
Interest cost on projected benefit obligation	9	9	27	26
Expected return on plan assets	(3)	(2)	(10)	(9)
Amortization of actuarial loss (gain)	2	2	6	5
Amortization of prior service credit	(29)	(35)	(87)	(106)
Net periodic costs	(20)	(26)	(61)	(82)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Carolinas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost on projected benefit obligation	2	2	6	6
Expected return on plan assets	(2)	(2)	(6)	(6)
Amortization of actuarial loss (gain)			(2)	(2)
Amortization of prior service credit	(2)	(4)	(6)	(10)
Net periodic costs	(2)	(4)	(8)	(12)
Other Post-Retirement Benefit Plans [Member] | Progress Energy [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		1		1
Interest cost on projected benefit obligation	4	4	11	11
Expected return on plan assets		(1)		(1)
Amortization of actuarial loss (gain)	5	5	15	16
Amortization of prior service credit	(21)	(26)	(63)	(77)
Net periodic costs	(12)	(17)	(37)	(50)
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	6	6
Amortization of actuarial loss (gain)	3	3	9	9
Amortization of prior service credit	(14)	(16)	(41)	(50)
Net periodic costs	(9)	(11)	(26)	(35)
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	2	3	6	6
Amortization of actuarial loss (gain)	2	2	6	7
Amortization of prior service credit	(8)	(8)	(23)	(26)
Net periodic costs	(4)	(3)	(11)	(13)
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)	(1)	(2)
Net periodic costs		(1)	(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	1	3
Expected return on plan assets				(1)
Amortization of actuarial loss (gain)				(1)
Amortization of prior service credit		(1)		(1)
Net periodic costs	$ 1		$ 1
Other Post-Retirement Benefit Plans [Member] | Piedmont Natural Gas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		1		1
Interest cost on projected benefit obligation				1
Expected return on plan assets				(1)
Net periodic costs		$ 1		$ 1

Employee Benefit Plans (Employe

Employee Benefit Plans (Employee Savings Plans) (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Jan. 31, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Defined Contribution Plan Disclosure [Line Items]
Contributions by Employer				$ 8
Duke Energy Ohio [Member]
Defined Contribution Plan Disclosure [Line Items]
Contributions by Employer				4
Piedmont Natural Gas [Member]
Defined Contribution Plan Disclosure [Line Items]
Contributions by Employer					$ 1
Employee Savings Plan [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions		$ 43	$ 39	147	130
Employee Savings Plan [Member] | Duke Energy Carolinas [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions		14	13	49	44
Employee Savings Plan [Member] | Progress Energy [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions		12	12	42	39
Employee Savings Plan [Member] | Duke Energy Progress [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions		9	8	30	27
Employee Savings Plan [Member] | Duke Energy Florida [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions		4	3	13	11
Employee Savings Plan [Member] | Duke Energy Ohio [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions		1	1	3	3
Employee Savings Plan [Member] | Duke Energy Indiana [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions		2	2	7	6
Employee Savings Plan [Member] | Piedmont Natural Gas [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions		$ 2	$ 2	$ 5	$ 5
Pension Plan [Member] | Piedmont Natural Gas [Member]
Defined Contribution Plan Disclosure [Line Items]
Contributions by Employer	$ 2

Income Taxes (Effective Tax Rat

Income Taxes (Effective Tax Rates) (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
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	27.60%	34.00%	30.40%	31.70%
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	32.90%	34.30%	34.10%	34.40%
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	29.10%	32.80%	31.90%	34.70%
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	31.70%	31.40%	32.40%	33.50%
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	34.80%	36.00%	36.10%	37.00%
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	33.30%	36.80%	34.40%	32.50%
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	38.30%	35.20%	39.00%	34.00%
Piedmont Natural Gas [Member]
Reconciliation of Income Tax Expense at the U.S. Federal Statutory Tax Rate to the Actual Tax Expense from Continuing Operations [Abstract]
Effective tax rate	47.60%	40.00%	36.10%	37.70%

Income Taxes Income Taxes (Taxe

Income Taxes Income Taxes (Taxes on Foreign Earnings) (Details) - Discontinued Operations, Disposed of by Sale [Member] - International Energy [Member] - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income tax benefit	$ 4	$ (48)
Previously Remitted Earnings [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income tax benefit		$ (95)