Duke Energy (DUK) 10-Q 10 May 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information	3 Months Ended
	Mar. 31, 2018shares
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	Mar. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding	701,007,267
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
	Mar. 31, 2018	Mar. 31, 2017
Operating Revenues
Regulated electric	$ 5,284	$ 4,913
Regulated natural gas	700	646
Nonregulated electric and other	151	170
Total operating revenues	6,135	5,729
Operating Expenses
Fuel used in electric generation and purchased power	1,676	1,449
Cost of natural gas	313	258
Operation, maintenance and other	1,464	1,468
Depreciation and amortization	967	859
Property and other taxes	316	304
Impairment charges	43
Total operating expenses	4,779	4,338
(Loss) Gains on Sales of Other Assets and Other, net	(100)	11
Operating Income	1,256	1,402
Other Income and Expenses
Equity in (losses) earnings of unconsolidated affiliates	(24)	29
Other income and expenses, net	86	121
Total other income and expenses	62	150
Interest Expense	515	491
Income Before Income Taxes	803	1,061
Income Tax Expense	181	344
Net income	622	717
Less: Net Income Attributable to Noncontrolling Interests	2	1
Net Income Attributable to Parent	620	716
Other Comprehensive Income (Loss), net of tax
Pension and OPEB adjustments	1	1
Net unrealized gain on cash flow hedges	12	2
Reclassification into earnings from cash flow hedges	1	1
Unrealized gains on available-for-sale securities	(3)	4
Other Comprehensive Income, net of tax	11	8
Comprehensive Income	633	725
Less: Comprehensive Income Attributable to Noncontrolling Interests	2	1
Comprehensive Income Attributable to Parent	$ 631	$ 724
Net income attributable to Duke Energy Corporation common stockholders
Basic (usd per share)	$ 0.88	$ 1.02
Diluted (usd per share)	$ 0.88	$ 1.02
Weighted average shares outstanding
Basic (shares)	701	700
Diluted (shares)	701	700
Duke Energy Carolinas [Member]
Operating Revenues
Total operating revenues	$ 1,763	$ 1,716
Operating Expenses
Fuel used in electric generation and purchased power	473	428
Operation, maintenance and other	451	495
Depreciation and amortization	272	254
Property and other taxes	72	68
Impairment charges	13
Total operating expenses	1,281	1,245
Operating Income	482	471
Other Income and Expenses
Total other income and expenses	39	50
Interest Expense	107	103
Income Before Income Taxes	414	418
Income Tax Expense	91	148
Net Income Attributable to Parent	323	270
Other Comprehensive Income (Loss), net of tax
Reclassification into earnings from cash flow hedges	1
Other Comprehensive Income, net of tax	1
Comprehensive Income Attributable to Parent	324	270
Progress Energy [Member]
Operating Revenues
Total operating revenues	2,576	2,179
Operating Expenses
Fuel used in electric generation and purchased power	976	726
Operation, maintenance and other	623	560
Depreciation and amortization	384	313
Property and other taxes	123	117
Impairment charges	29
Total operating expenses	2,135	1,716
(Loss) Gains on Sales of Other Assets and Other, net	6	8
Operating Income	447	471
Other Income and Expenses
Total other income and expenses	35	40
Interest Expense	209	206
Income Before Income Taxes	273	305
Income Tax Expense	36	104
Net income	237	201
Less: Net Income Attributable to Noncontrolling Interests	2	2
Net Income Attributable to Parent	235	199
Other Comprehensive Income (Loss), net of tax
Pension and OPEB adjustments		1
Net unrealized gain on cash flow hedges	2
Reclassification into earnings from cash flow hedges		1
Unrealized gains on available-for-sale securities		1
Other Comprehensive Income, net of tax	2	3
Comprehensive Income	239	204
Less: Comprehensive Income Attributable to Noncontrolling Interests	2	2
Comprehensive Income Attributable to Parent	237	202
Duke Energy Progress [Member]
Operating Revenues
Total operating revenues	1,460	1,219
Operating Expenses
Fuel used in electric generation and purchased power	509	364
Operation, maintenance and other	381	362
Depreciation and amortization	235	181
Property and other taxes	35	40
Impairment charges	32
Total operating expenses	1,192	947
(Loss) Gains on Sales of Other Assets and Other, net	1	2
Operating Income	269	274
Other Income and Expenses
Total other income and expenses	18	31
Interest Expense	81	82
Income Before Income Taxes	206	223
Income Tax Expense	29	76
Net Income Attributable to Parent	177	147
Other Comprehensive Income (Loss), net of tax
Comprehensive Income Attributable to Parent	177	147
Duke Energy Florida [Member]
Operating Revenues
Total operating revenues	1,115	959
Operating Expenses
Fuel used in electric generation and purchased power	467	362
Operation, maintenance and other	237	195
Depreciation and amortization	150	132
Property and other taxes	88	77
Impairment charges		1
Total operating expenses	942	767
Operating Income	173	192
Other Income and Expenses
Total other income and expenses	21	20
Interest Expense	71	70
Income Before Income Taxes	123	142
Income Tax Expense	20	52
Net Income Attributable to Parent	103	90
Other Comprehensive Income (Loss), net of tax
Unrealized gains on available-for-sale securities		1
Other Comprehensive Income, net of tax		1
Comprehensive Income Attributable to Parent	103	91
Duke Energy Ohio [Member]
Operating Revenues
Regulated electric	336	337
Regulated natural gas	174	170
Nonregulated electric and other	14	11
Total operating revenues	524	518
Operating Expenses
Fuel used in electric generation and purchased power	92	97
Fuel used in electric generation and purchased power – nonregulated	15	15
Cost of natural gas	54	54
Operation, maintenance and other	131	131
Depreciation and amortization	70	67
Property and other taxes	77	72
Total operating expenses	439	436
(Loss) Gains on Sales of Other Assets and Other, net	(106)
Operating Income	(21)	82
Other Income and Expenses
Total other income and expenses	6	5
Interest Expense	22	22
Income Before Income Taxes	(37)	65
Income Tax Expense	(12)	23
Net Income Attributable to Parent	(25)	42
Other Comprehensive Income (Loss), net of tax
Comprehensive Income Attributable to Parent	(25)	42
Duke Energy Indiana [Member]
Operating Revenues
Total operating revenues	731	758
Operating Expenses
Fuel used in electric generation and purchased power	232	251
Operation, maintenance and other	181	176
Depreciation and amortization	130	125
Property and other taxes	20	22
Total operating expenses	563	574
Operating Income	168	184
Other Income and Expenses
Total other income and expenses	7	10
Interest Expense	40	44
Income Before Income Taxes	135	150
Income Tax Expense	35	59
Net Income Attributable to Parent	100	91
Other Comprehensive Income (Loss), net of tax
Comprehensive Income Attributable to Parent	100	91
Piedmont Natural Gas [Member]
Operating Revenues
Total operating revenues	553	500
Operating Expenses
Cost of natural gas	259	205
Operation, maintenance and other	82	77
Depreciation and amortization	39	35
Property and other taxes	12	13
Total operating expenses	392	330
Operating Income	161	170
Other Income and Expenses
Equity in (losses) earnings of unconsolidated affiliates	2	3
Other income and expenses, net	3
Total other income and expenses	5	3
Interest Expense	21	20
Income Before Income Taxes	145	153
Income Tax Expense	35	58
Net Income Attributable to Parent	110	95
Other Comprehensive Income (Loss), net of tax
Comprehensive Income Attributable to Parent	$ 110	$ 95

Condensed Consolidated Stateme3

Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest [Abstract]
Net income	$ 622	$ 717
Other Comprehensive Income, net of tax
Pension and OPEB adjustments	1	1
Net unrealized gains on cash flow hedges	12	2
Reclassification into earnings from cash flow hedges	1	1
Unrealized (losses) gains on available-for-sale securities	(3)	4
Other Comprehensive Income, net of tax	11	8
Comprehensive Income	633	725
Less: Comprehensive Income Attributable to Noncontrolling Interests	2	1
Comprehensive Income Attributable to Parent	$ 631	$ 724

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Current Assets
Cash and cash equivalents	$ 421	$ 358
Receivables (net of allowance for doubtful accounts)	759	779
Receivables of VIEs (net of allowance for doubtful accounts)	1,984	1,995
Inventory	3,149	3,250
Regulatory assets	1,544	1,437
Other	422	634
Total current assets	8,279	8,453
Property, Plant and Equipment
Cost	129,281	127,507
Accumulated depreciation and amortization	(42,307)	(41,537)
Generation facilities to be retired, net	399	421
Net property, plant and equipment	87,373	86,391
Other Noncurrent Assets
Goodwill	19,396	19,396
Regulatory assets	12,218	12,442
Nuclear decommissioning trust funds	7,024	7,097
Investments in equity method unconsolidated affiliates	1,189	1,175
Other	3,062	2,960
Total other noncurrent assets	42,889	43,070
Total Assets	138,541	137,914
Current Liabilities
Accounts payable	2,391	3,043
Notes payable and commercial paper	2,969	2,163
Taxes accrued	422	551
Interest accrued	542	525
Current maturities of long-term debt	3,951	3,244
Asset retirement obligations	676	689
Regulatory liabilities	505	402
Other	1,542	1,865
Total current liabilities	12,998	12,482
Long-Term Debt	49,030	49,035
Other Noncurrent Liabilities
Deferred income taxes	6,855	6,621
Asset retirement obligations	9,484	9,486
Regulatory liabilities	15,283	15,330
Accrued pension and other post-retirement benefit costs	1,018	1,103
Investment tax credits	537	539
Other	1,538	1,581
Total other noncurrent liabilities	34,715	34,660
Commitments and Contingencies
Equity
Common stock	1	1
Additional paid-in capital	38,839	38,792
Retained earnings	3,021	3,013
Accumulated other comprehensive loss	(69)	(67)
Total Parent stockholders' equity	41,792	41,739
Noncontrolling interests	6	(2)
Total equity	41,798	41,737
Total Liabilities and Equity	138,541	137,914
Duke Energy Carolinas [Member]
Current Assets
Cash and cash equivalents	3	16
Receivables (net of allowance for doubtful accounts)	194	200
Receivables of VIEs (net of allowance for doubtful accounts)	634	640
Receivables from affiliated companies	106	95
Inventory	980	971
Regulatory assets	331	299
Other	42	19
Total current assets	2,290	2,240
Property, Plant and Equipment
Cost	43,562	42,939
Accumulated depreciation and amortization	(15,404)	(15,063)
Net property, plant and equipment	28,158	27,876
Other Noncurrent Assets
Regulatory assets	2,825	2,853
Nuclear decommissioning trust funds	3,734	3,772
Other	1,023	979
Total other noncurrent assets	7,582	7,604
Total Assets	38,030	37,720
Current Liabilities
Accounts payable	726	842
Accounts payable to affiliated companies	259	209
Notes payable to affiliated companies	45	104
Taxes accrued	84	234
Interest accrued	144	108
Current maturities of long-term debt	805	1,205
Asset retirement obligations	281	337
Regulatory liabilities	116	126
Other	369	486
Total current liabilities	2,829	3,651
Long-Term Debt	9,589	8,598
Long-Term Debt Payable to Affiliated Companies	300	300
Other Noncurrent Liabilities
Deferred income taxes	3,493	3,413
Asset retirement obligations	3,318	3,273
Regulatory liabilities	6,208	6,231
Accrued pension and other post-retirement benefit costs	95	95
Investment tax credits	231	232
Other	532	566
Total other noncurrent liabilities	13,877	13,810
Commitments and Contingencies
Equity
Member's equity	11,441	11,368
Accumulated other comprehensive loss	(6)	(7)
Total member's equity	11,435	11,361
Total Liabilities and Equity	38,030	37,720
Progress Energy [Member]
Current Assets
Cash and cash equivalents	20	40
Receivables (net of allowance for doubtful accounts)	122	123
Receivables of VIEs (net of allowance for doubtful accounts)	815	780
Receivables from affiliated companies	2	31
Notes receivable from affiliated companies	113	240
Inventory	1,537	1,592
Regulatory assets	869	741
Other	259	334
Total current assets	3,737	3,881
Property, Plant and Equipment
Cost	47,915	47,323
Accumulated depreciation and amortization	(16,060)	(15,857)
Generation facilities to be retired, net	399	421
Net property, plant and equipment	32,254	31,887
Other Noncurrent Assets
Goodwill	3,655	3,655
Regulatory assets	5,872	6,010
Nuclear decommissioning trust funds	3,290	3,324
Other	990	931
Total other noncurrent assets	13,807	13,920
Total Assets	49,798	49,688
Current Liabilities
Accounts payable	760	1,006
Accounts payable to affiliated companies	284	251
Notes payable to affiliated companies	982	805
Taxes accrued	109	101
Interest accrued	213	212
Current maturities of long-term debt	1,820	771
Asset retirement obligations	326	295
Regulatory liabilities	272	213
Other	637	729
Total current liabilities	5,403	4,383
Long-Term Debt	15,787	16,916
Long-Term Debt Payable to Affiliated Companies	150	150
Other Noncurrent Liabilities
Deferred income taxes	3,603	3,502
Asset retirement obligations	5,091	5,119
Regulatory liabilities	5,227	5,306
Accrued pension and other post-retirement benefit costs	527	545
Other	307	302
Total other noncurrent liabilities	14,755	14,774
Commitments and Contingencies
Equity
Additional paid-in capital	9,142	9,143
Retained earnings	4,591	4,350
Accumulated other comprehensive loss	(29)	(25)
Total Parent stockholders' equity	13,704	13,468
Noncontrolling interests	(1)	(3)
Total equity	13,703	13,465
Total Liabilities and Equity	49,798	49,688
Duke Energy Progress [Member]
Current Assets
Cash and cash equivalents	8	20
Receivables (net of allowance for doubtful accounts)	50	56
Receivables of VIEs (net of allowance for doubtful accounts)	497	459
Receivables from affiliated companies	5	3
Inventory	1,002	1,017
Regulatory assets	476	352
Other	55	97
Total current assets	2,093	2,004
Property, Plant and Equipment
Cost	29,866	29,583
Accumulated depreciation and amortization	(11,012)	(10,903)
Generation facilities to be retired, net	399	421
Net property, plant and equipment	19,253	19,101
Other Noncurrent Assets
Regulatory assets	3,480	3,507
Nuclear decommissioning trust funds	2,568	2,588
Other	641	599
Total other noncurrent assets	6,689	6,694
Total Assets	28,035	27,799
Current Liabilities
Accounts payable	342	402
Accounts payable to affiliated companies	208	179
Notes payable to affiliated companies	354	240
Taxes accrued	36	64
Interest accrued	86	102
Current maturities of long-term debt	603	3
Asset retirement obligations	323	295
Regulatory liabilities	184	139
Other	324	376
Total current liabilities	2,460	1,800
Long-Term Debt	6,604	7,204
Long-Term Debt Payable to Affiliated Companies	150	150
Other Noncurrent Liabilities
Deferred income taxes	1,932	1,883
Asset retirement obligations	4,356	4,378
Regulatory liabilities	3,973	3,999
Accrued pension and other post-retirement benefit costs	246	248
Investment tax credits	142	143
Other	46	45
Total other noncurrent liabilities	10,695	10,696
Commitments and Contingencies
Equity
Total member's equity	8,126	7,949
Total Liabilities and Equity	28,035	27,799
Duke Energy Florida [Member]
Current Assets
Cash and cash equivalents	6	13
Receivables (net of allowance for doubtful accounts)	71	65
Receivables of VIEs (net of allowance for doubtful accounts)	318	321
Receivables from affiliated companies	1	2
Notes receivable from affiliated companies	153	313
Inventory	535	574
Regulatory assets	393	389
Other	40	86
Total current assets	1,517	1,763
Property, Plant and Equipment
Cost	18,040	17,730
Accumulated depreciation and amortization	(5,042)	(4,947)
Net property, plant and equipment	12,998	12,783
Other Noncurrent Assets
Regulatory assets	2,391	2,503
Nuclear decommissioning trust funds	722	736
Other	301	284
Total other noncurrent assets	3,414	3,523
Total Assets	17,929	18,069
Current Liabilities
Accounts payable	416	602
Accounts payable to affiliated companies	82	74
Taxes accrued	72	34
Interest accrued	74	56
Current maturities of long-term debt	768	768
Asset retirement obligations	3	0
Regulatory liabilities	88	74
Other	299	334
Total current liabilities	1,802	1,942
Long-Term Debt	6,247	6,327
Other Noncurrent Liabilities
Deferred income taxes	1,812	1,761
Asset retirement obligations	735	742
Regulatory liabilities	1,254	1,307
Accrued pension and other post-retirement benefit costs	248	264
Other	110	108
Total other noncurrent liabilities	4,159	4,182
Commitments and Contingencies
Equity
Member's equity	5,723	5,614
Accumulated other comprehensive loss	(2)	4
Total member's equity	5,721	5,618
Total Liabilities and Equity	17,929	18,069
Duke Energy Ohio [Member]
Current Assets
Cash and cash equivalents	12	12
Receivables (net of allowance for doubtful accounts)	69	68
Receivables from affiliated companies	77	133
Notes receivable from affiliated companies		14
Inventory	108	133
Regulatory assets	43	49
Other	24	39
Total current assets	333	448
Property, Plant and Equipment
Cost	8,892	8,732
Accumulated depreciation and amortization	(2,729)	(2,691)
Net property, plant and equipment	6,163	6,041
Other Noncurrent Assets
Goodwill	920	920
Regulatory assets	432	445
Other	48	21
Total other noncurrent assets	1,400	1,386
Total Assets	7,896	7,875
Current Liabilities
Accounts payable	269	313
Accounts payable to affiliated companies	72	62
Notes payable to affiliated companies	130	29
Taxes accrued	145	190
Interest accrued	33	21
Current maturities of long-term debt	3	3
Asset retirement obligations	4	3
Regulatory liabilities	53	36
Other	66	71
Total current liabilities	775	728
Long-Term Debt	2,039	2,039
Long-Term Debt Payable to Affiliated Companies	25	25
Other Noncurrent Liabilities
Deferred income taxes	766	781
Asset retirement obligations	79	81
Regulatory liabilities	888	891
Accrued pension and other post-retirement benefit costs	81	59
Other	105	108
Total other noncurrent liabilities	1,919	1,920
Commitments and Contingencies
Equity
Common stock	762	762
Additional paid-in capital	2,670	2,670
Retained earnings	(294)	(269)
Total Parent stockholders' equity	3,138	3,163
Total Liabilities and Equity	7,896	7,875
Duke Energy Indiana [Member]
Current Assets
Cash and cash equivalents	15	9
Receivables (net of allowance for doubtful accounts)	56	57
Receivables from affiliated companies	99	125
Inventory	453	450
Regulatory assets	170	165
Other	30	30
Total current assets	823	836
Property, Plant and Equipment
Cost	15,104	14,948
Accumulated depreciation and amortization	(4,759)	(4,662)
Net property, plant and equipment	10,345	10,286
Other Noncurrent Assets
Regulatory assets	976	978
Other	234	189
Total other noncurrent assets	1,210	1,167
Total Assets	12,378	12,289
Current Liabilities
Accounts payable	157	196
Accounts payable to affiliated companies	73	78
Notes payable to affiliated companies	149	161
Taxes accrued	94	95
Interest accrued	52	57
Current maturities of long-term debt	62	3
Asset retirement obligations	65	54
Regulatory liabilities	20	24
Other	83	104
Total current liabilities	755	772
Long-Term Debt	3,570	3,630
Long-Term Debt Payable to Affiliated Companies	150	150
Other Noncurrent Liabilities
Deferred income taxes	941	925
Asset retirement obligations	713	727
Regulatory liabilities	1,743	1,723
Accrued pension and other post-retirement benefit costs	110	76
Investment tax credits	147	147
Other	28	18
Total other noncurrent liabilities	3,682	3,616
Commitments and Contingencies
Equity
Total member's equity	4,221	4,121
Total Liabilities and Equity	12,378	12,289
Piedmont Natural Gas [Member]
Current Assets
Cash and cash equivalents	12	19
Receivables (net of allowance for doubtful accounts)	251	275
Receivables from affiliated companies	7	7
Inventory	29	66
Regulatory assets	48	95
Other	21	52
Total current assets	368	514
Property, Plant and Equipment
Cost	6,861	6,725
Accumulated depreciation and amortization	(1,500)	(1,479)
Net property, plant and equipment	5,361	5,246
Other Noncurrent Assets
Goodwill	49	49
Regulatory assets	274	283
Investments in equity method unconsolidated affiliates	62	61
Other	66	65
Total other noncurrent assets	451	458
Total Assets	6,180	6,218
Current Liabilities
Accounts payable	128	125
Accounts payable to affiliated companies	32	13
Notes payable to affiliated companies	107	364
Taxes accrued	65	19
Interest accrued	24	31
Current maturities of long-term debt	250	250
Regulatory liabilities	45	3
Other	55	69
Total current liabilities	706	874
Long-Term Debt	1,787	1,787
Other Noncurrent Liabilities
Deferred income taxes	558	564
Asset retirement obligations	15	15
Regulatory liabilities	1,179	1,141
Accrued pension and other post-retirement benefit costs	4	5
Other	159	170
Total other noncurrent liabilities	1,915	1,895
Commitments and Contingencies
Equity
Common stock	860	860
Retained earnings	912	802
Total Parent stockholders' equity	1,772	1,662
Total Liabilities and Equity	$ 6,180	$ 6,218

Condensed Consolidated Balance5

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Allowance for doubtful accounts - receivables	$ 17	$ 14
Regulatory assets, current	1,544	1,437
Other, current assets	422	634
Regulatory assets, noncurrent	12,218	12,442
Current maturities of long-term debt	3,951	3,244
Long-Term Debt	$ 49,030	$ 49,035
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	2,000,000,000	2,000,000,000
Common stock, shares outstanding	701,000,000	700,000,000
Variable Interest Entity [Member]
Allowance for doubtful accounts - receivables of VIEs	$ 57	$ 54
Regulatory assets, current	51	51
Regulatory assets, noncurrent	1,082	1,091
Current maturities of long-term debt	225	225
Long-Term Debt	4,275	4,306
Duke Energy Carolinas [Member]
Allowance for doubtful accounts - receivables	2	2
Regulatory assets, current	331	299
Other, current assets	42	19
Regulatory assets, noncurrent	2,825	2,853
Current maturities of long-term debt	805	1,205
Long-Term Debt	9,589	8,598
Duke Energy Carolinas [Member] | Variable Interest Entity [Member]
Allowance for doubtful accounts - receivables of VIEs	7	7
Progress Energy [Member]
Allowance for doubtful accounts - receivables	4	4
Regulatory assets, current	869	741
Other, current assets	259	334
Regulatory assets, noncurrent	5,872	6,010
Current maturities of long-term debt	1,820	771
Long-Term Debt	$ 15,787	$ 16,916
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	100	100
Common stock, shares outstanding	100	100
Progress Energy [Member] | Variable Interest Entity [Member]
Allowance for doubtful accounts - receivables of VIEs	$ 7	$ 7
Regulatory assets, current	51	51
Regulatory assets, noncurrent	1,082	1,091
Current maturities of long-term debt	53	53
Long-Term Debt	1,660	1,689
Duke Energy Progress [Member]
Allowance for doubtful accounts - receivables	2	1
Regulatory assets, current	476	352
Other, current assets	55	97
Regulatory assets, noncurrent	3,480	3,507
Current maturities of long-term debt	603	3
Long-Term Debt	6,604	7,204
Duke Energy Progress [Member] | Variable Interest Entity [Member]
Allowance for doubtful accounts - receivables of VIEs	5	5
Duke Energy Florida [Member]
Allowance for doubtful accounts - receivables	3	3
Regulatory assets, current	393	389
Other, current assets	40	86
Regulatory assets, noncurrent	2,391	2,503
Current maturities of long-term debt	768	768
Long-Term Debt	6,247	6,327
Duke Energy Florida [Member] | Variable Interest Entity [Member]
Allowance for doubtful accounts - receivables of VIEs	2	2
Regulatory assets, current	51	51
Other, current assets	13	40
Regulatory assets, noncurrent	1,082	1,091
Current maturities of long-term debt	53	53
Long-Term Debt	1,361	1,389
Duke Energy Ohio [Member]
Allowance for doubtful accounts - receivables	3	3
Regulatory assets, current	43	49
Other, current assets	24	39
Regulatory assets, noncurrent	432	445
Current maturities of long-term debt	3	3
Long-Term Debt	$ 2,039	$ 2,039
Common stock, par value	$ 8.50	$ 8.50
Common stock, shares authorized	120,000,000	120,000,000
Common stock, shares outstanding	90,000,000	90,000,000
Duke Energy Indiana [Member]
Allowance for doubtful accounts - receivables	$ 2	$ 2
Regulatory assets, current	170	165
Other, current assets	30	30
Regulatory assets, noncurrent	976	978
Current maturities of long-term debt	62	3
Long-Term Debt	3,570	3,630
Piedmont Natural Gas [Member]
Allowance for doubtful accounts - receivables	4	2
Regulatory assets, current	48	95
Other, current assets	21	52
Regulatory assets, noncurrent	274	283
Current maturities of long-term debt	250	250
Long-Term Debt	$ 1,787	$ 1,787
Common stock, shares authorized	100	100
Common stock, shares outstanding	100	100

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 622	$ 717
Net income (attributable to parent)	620	716
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and accretion (including amortization of nuclear fuel)	1,089	991
Equity component of AFUDC	(55)	(62)
Losses (gains) on sales of other assets	100	(11)
Impairment charges	43
Deferred income taxes	199	342
Equity in losses (earnings) of unconsolidated affiliates	24	(29)
Accrued pension and other post-retirement benefit costs	15	6
Contributions to qualified pension plans	(141)
Payments for asset retirement obligations	(122)	(134)
Payment for disposal of other assets	(105)
Other rate case adjustments	37
Provision for rate refunds	158
(Increase) decrease in
Net realized and unrealized mark-to-market and hedging transactions	4	(38)
Receivables	64	343
Inventory	101	155
Other current assets	27	(22)
Increase (decrease) in
Accounts payable	(327)	(463)
Taxes accrued	(107)	(28)
Other current liabilities	(171)	(478)
Other assets	(59)	(45)
Other liabilities	(5)	2
Net cash provided by operating activities	1,391	1,246
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(2,087)	(2,160)
Cost of removal, net of salvage	(81)	(39)
Contributions to equity method investments	(74)	(175)
Purchases of debt and equity securities	(958)	(1,386)
Proceeds from sales and maturities of debt and equity securities	930	1,405
Other	6	(6)
Net cash used in investing activities	(2,264)	(2,361)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from the issuance of long-term debt	1,240	1,563
Proceeds from the issuance of common stock	21
Payments for the redemption of long-term debt	(487)	(408)
Proceeds from issuance of short-term debt with original maturities greater than 90 days	135	25
Payments for the redemption of short-term debt with original maturities greater than 90 days	(50)	(7)
Notes payable and commercial paper	706	1,045
Dividends paid	(599)	(600)
Other	(19)	(22)
Net cash provided by financing activities	947	1,596
Net increase in cash, cash equivalents and restricted cash	74	481
Cash, cash equivalents and restricted cash at beginning of period	505	541
Cash, cash equivalents and restricted cash at end of period	579	1,022
Cash and cash equivalents at beginning of period	358
Cash and cash equivalents at end of period	421
Significant non-cash transactions:
Accrued capital expenditures	799	575
Non-cash dividends	26
Duke Energy Carolinas [Member]
CASH FLOWS FROM OPERATING ACTIVITIES
Net income (attributable to parent)	323	270
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and accretion (including amortization of nuclear fuel)	347	339
Equity component of AFUDC	(21)	(30)
Impairment charges	13
Deferred income taxes	80	162
Accrued pension and other post-retirement benefit costs	1
Contributions to qualified pension plans	(46)
Payments for asset retirement obligations	(55)	(65)
Provision for rate refunds	61
(Increase) decrease in
Net realized and unrealized mark-to-market and hedging transactions		3
Receivables	19	66
Receivable from affiliated companies	(11)	54
Inventory	(9)	4
Other current assets	(144)	(26)
Increase (decrease) in
Accounts payable	(76)	(131)
Accounts payable to affiliated companies	50	3
Taxes accrued	(129)	(53)
Other current liabilities	(23)	(125)
Other assets	12	(3)
Other liabilities	(43)	(2)
Net cash provided by operating activities	349	466
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(621)	(563)
Cost of removal, net of salvage	(17)	(16)
Purchases of debt and equity securities	(494)	(722)
Proceeds from sales and maturities of debt and equity securities	494	722
Notes receivable from affiliated companies		66
Other	(4)	(4)
Net cash used in investing activities	(642)	(517)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from the issuance of long-term debt	991
Payments for the redemption of long-term debt	(401)	(113)
Notes payable to affiliated companies	(59)	337
Distributions to parent	(250)	(175)
Other	(1)	(1)
Net cash provided by financing activities	280	48
Net increase (decrease) in cash and cash equivalents	(13)	(3)
Cash and cash equivalents at beginning of period	16	14
Cash and cash equivalents at end of period	3	11
Significant non-cash transactions:
Accrued capital expenditures	267	164
Progress Energy [Member]
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	237	201
Net income (attributable to parent)	235	199
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and accretion (including amortization of nuclear fuel)	439	365
Equity component of AFUDC	(26)	(24)
Losses (gains) on sales of other assets	(6)	(9)
Impairment charges	29
Deferred income taxes	71	220
Accrued pension and other post-retirement benefit costs	6	(3)
Contributions to qualified pension plans	(45)
Payments for asset retirement obligations	(55)	(60)
Other rate case adjustments	37
Provision for rate refunds	33
(Increase) decrease in
Net realized and unrealized mark-to-market and hedging transactions	4	(2)
Receivables	(33)	115
Receivable from affiliated companies	29	100
Inventory	55	65
Other current assets	(60)	(212)
Increase (decrease) in
Accounts payable	(53)	(228)
Accounts payable to affiliated companies	33	(32)
Taxes accrued	8	12
Other current liabilities	(82)	(121)
Other assets	(86)	(58)
Other liabilities	(8)	(14)
Net cash provided by operating activities	527	315
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(762)	(1,011)
Cost of removal, net of salvage	(41)
Purchases of debt and equity securities	(406)	(629)
Proceeds from sales and maturities of debt and equity securities	411	635
Notes receivable from affiliated companies	127	(104)
Other	1	5
Net cash used in investing activities	(670)	(1,104)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from the issuance of long-term debt		892
Payments for the redemption of long-term debt	(80)	(288)
Notes payable to affiliated companies	177	137
Other	(2)	(4)
Net cash provided by financing activities	95	737
Net increase in cash, cash equivalents and restricted cash	(48)	(52)
Cash, cash equivalents and restricted cash at beginning of period	87	110
Cash, cash equivalents and restricted cash at end of period	39	58
Cash and cash equivalents at beginning of period	40
Cash and cash equivalents at end of period	20
Significant non-cash transactions:
Accrued capital expenditures	316	219
Duke Energy Progress [Member]
CASH FLOWS FROM OPERATING ACTIVITIES
Net income (attributable to parent)	177	147
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and accretion (including amortization of nuclear fuel)	284	228
Equity component of AFUDC	(14)	(13)
Losses (gains) on sales of other assets	(1)	(3)
Impairment charges	32
Deferred income taxes	42	120
Accrued pension and other post-retirement benefit costs	4	(5)
Contributions to qualified pension plans	(25)
Payments for asset retirement obligations	(44)	(47)
Other rate case adjustments	37
Provision for rate refunds	33
(Increase) decrease in
Net realized and unrealized mark-to-market and hedging transactions	2	(2)
Receivables	(31)	65
Receivable from affiliated companies	(2)	(1)
Inventory	15	23
Other current assets	(88)	(60)
Increase (decrease) in
Accounts payable	(39)	(192)
Accounts payable to affiliated companies	29	17
Taxes accrued	(28)	(68)
Other current liabilities	(64)	(81)
Other assets	18	(44)
Other liabilities	(5)	(10)
Net cash provided by operating activities	332	74
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(424)	(474)
Cost of removal, net of salvage	(31)	(9)
Purchases of debt and equity securities	(284)	(476)
Proceeds from sales and maturities of debt and equity securities	281	470
Notes receivable from affiliated companies		165
Other	1
Net cash used in investing activities	(457)	(324)
CASH FLOWS FROM FINANCING ACTIVITIES
Payments for the redemption of long-term debt		(250)
Notes payable to affiliated companies	114	502
Other	(1)	(2)
Net cash provided by financing activities	113	250
Net increase (decrease) in cash and cash equivalents	(12)
Cash and cash equivalents at beginning of period	20	11
Cash and cash equivalents at end of period	8	11
Significant non-cash transactions:
Accrued capital expenditures	137	66
Duke Energy Florida [Member]
CASH FLOWS FROM OPERATING ACTIVITIES
Net income (attributable to parent)	103	90
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and accretion (including amortization of nuclear fuel)	152	134
Equity component of AFUDC	(12)	(11)
Impairment charges		1
Deferred income taxes	29	100
Accrued pension and other post-retirement benefit costs	1	1
Contributions to qualified pension plans	(20)
Payments for asset retirement obligations	(11)	(14)
(Increase) decrease in
Net realized and unrealized mark-to-market and hedging transactions	2
Receivables	(2)	51
Receivable from affiliated companies		(1)
Inventory	39	42
Other current assets	42	(72)
Increase (decrease) in
Accounts payable	(13)	(35)
Accounts payable to affiliated companies	8	(48)
Taxes accrued	38	29
Other current liabilities	(17)	(47)
Other assets	(107)	(13)
Other liabilities	(5)	(5)
Net cash provided by operating activities	227	202
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(338)	(538)
Cost of removal, net of salvage	(10)	9
Purchases of debt and equity securities	(122)	(153)
Proceeds from sales and maturities of debt and equity securities	129	165
Notes receivable from affiliated companies	160	(293)
Other		4
Net cash used in investing activities	(181)	(806)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from the issuance of long-term debt		892
Payments for the redemption of long-term debt	(80)	(38)
Notes payable to affiliated companies		(297)
Other		(1)
Net cash provided by financing activities	(80)	556
Net increase in cash, cash equivalents and restricted cash	(34)	(48)
Cash, cash equivalents and restricted cash at beginning of period	53	69
Cash, cash equivalents and restricted cash at end of period	19	21
Cash and cash equivalents at beginning of period	13
Cash and cash equivalents at end of period	6
Significant non-cash transactions:
Accrued capital expenditures	179	153
Duke Energy Ohio [Member]
CASH FLOWS FROM OPERATING ACTIVITIES
Net income (attributable to parent)	(25)	42
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and accretion (including amortization of nuclear fuel)	71	68
Equity component of AFUDC	(4)	(2)
Losses (gains) on sales of other assets	106
Deferred income taxes	(15)	30
Accrued pension and other post-retirement benefit costs	1	1
Payments for asset retirement obligations	(1)	(2)
Provision for rate refunds	16
(Increase) decrease in
Net realized and unrealized mark-to-market and hedging transactions		1
Receivables	(1)	7
Receivable from affiliated companies	56	41
Inventory	25	19
Other current assets	19	9
Increase (decrease) in
Accounts payable	(27)	(10)
Accounts payable to affiliated companies	(95)	1
Taxes accrued	(45)	(52)
Other current liabilities	20	9
Other assets		(6)
Other liabilities	(13)	(3)
Net cash provided by operating activities	88	153
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(188)	(143)
Cost of removal, net of salvage	(14)	(8)
Notes receivable from affiliated companies	14	(85)
Net cash used in investing activities	(188)	(236)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from the issuance of long-term debt		93
Payments for the redemption of long-term debt		(1)
Notes payable to affiliated companies	101	(8)
Other	(1)	(1)
Net cash provided by financing activities	100	83
Cash and cash equivalents at beginning of period	12	13
Cash and cash equivalents at end of period	12	13
Significant non-cash transactions:
Accrued capital expenditures	64	57
Duke Energy Indiana [Member]
CASH FLOWS FROM OPERATING ACTIVITIES
Net income (attributable to parent)	100	91
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and accretion (including amortization of nuclear fuel)	131	126
Equity component of AFUDC	(4)	(6)
Deferred income taxes	17	37
Accrued pension and other post-retirement benefit costs	2	1
Contributions to qualified pension plans	(8)
Payments for asset retirement obligations	(11)	(7)
Provision for rate refunds	26
(Increase) decrease in
Receivables		44
Receivable from affiliated companies	26	26
Inventory	(3)	26
Other current assets	(23)	(2)
Increase (decrease) in
Accounts payable	21	(32)
Accounts payable to affiliated companies	(5)	1
Taxes accrued	(1)	41
Other current liabilities	(10)	(15)
Other assets	(1)	(11)
Other liabilities		(3)
Net cash provided by operating activities	257	317
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(231)	(189)
Cost of removal, net of salvage	(7)	(15)
Purchases of debt and equity securities	(6)	(4)
Proceeds from sales and maturities of debt and equity securities	3	2
Notes receivable from affiliated companies		(113)
Other	3	3
Net cash used in investing activities	(238)	(316)
CASH FLOWS FROM FINANCING ACTIVITIES
Payments for the redemption of long-term debt		(2)
Notes payable to affiliated companies	(12)
Other	(1)	(1)
Net cash provided by financing activities	(13)	(3)
Net increase (decrease) in cash and cash equivalents	6	(2)
Cash and cash equivalents at beginning of period	9	17
Cash and cash equivalents at end of period	15	15
Significant non-cash transactions:
Accrued capital expenditures	64	84
Piedmont Natural Gas [Member]
CASH FLOWS FROM OPERATING ACTIVITIES
Net income (attributable to parent)	110	95
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and accretion (including amortization of nuclear fuel)	39	37
Deferred income taxes	(7)	50
Equity in losses (earnings) of unconsolidated affiliates	(2)	(3)
Accrued pension and other post-retirement benefit costs	(1)	3
Provision for rate refunds	23
(Increase) decrease in
Net realized and unrealized mark-to-market and hedging transactions		(41)
Receivables	22	40
Inventory	37	37
Other current assets	79	24
Increase (decrease) in
Accounts payable	(15)	(31)
Accounts payable to affiliated companies	19	(5)
Taxes accrued	46	2
Other current liabilities	18	(17)
Other assets	4	25
Other liabilities	(1)	(1)
Net cash provided by operating activities	371	215
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(121)	(141)
Cost of removal, net of salvage	(2)	(1)
Contributions to equity method investments		(12)
Other	2	(2)
Net cash used in investing activities	(121)	(156)
CASH FLOWS FROM FINANCING ACTIVITIES
Notes payable and commercial paper		(330)
Notes payable to affiliated companies	(257)	261
Net cash provided by financing activities	(257)	(69)
Net increase (decrease) in cash and cash equivalents	(7)	(10)
Cash and cash equivalents at beginning of period	19	25
Cash and cash equivalents at end of period	12	15
Significant non-cash transactions:
Accrued capital expenditures	$ 52	$ 24

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]		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]	Piedmont Natural Gas [Member]	Piedmont Natural Gas [Member]Common Stock [Member]	Piedmont Natural Gas [Member]Retained Earnings [Member]
Beginning Balance at Dec. 31, 2016	$ 41,041		$ 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
Beginning Balance (member's equity) at Dec. 31, 2016														$ 10,772	$ 10,781	$ (9)														$ 7,358	$ 4,900	$ 4,899		$ 1						$ 4,067
Beginning Balance (parent) at Dec. 31, 2016																																				$ 2,996	$ 762	$ 2,695	$ (461)		$ 1,672	$ 860	$ 812
Net income	717				716						716		1				201				199						199		2
Net income (attributable to parent)	716													270	270		199													147	90	90				42			42	91	95		95
Other comprehensive income (loss)	8						3	4		1	8						3						1	1		1	3				1			1
Common stock issuances, including dividend reinvestment and employee benefits, shares			0
Common stock issuances, including dividend reinvestment and employee benefits	1			1							1
Distributions to noncontrolling interest in subsidiaries	(2)												(2)
Distributions/dividends to parent	(600)				(600)						(600)			(175)	(175)
Other	21	[1]			21	[1]					21	[1]					1		0								0		1
Ending Balance at Mar. 31, 2017	41,186		$ 1	38,742	2,521		(17)	3		(71)	41,179		7				12,012		8,094		3,963		(22)	2		(15)	12,022		(10)
Ending Balance, in shares at Mar. 31, 2017			700,000,000
Ending Balance (member's equity) at Mar. 31, 2017														10,867	10,876	(9)														7,505	4,991	4,989		2						4,158
Ending Balance (parent) at Mar. 31, 2017																																				$ 3,038	762	2,695	(419)		$ 1,767	860	907
Beginning Balance at Dec. 31, 2017	$ 41,737		$ 1	38,792	3,013		(10)	12		(69)	41,739		(2)				$ 13,465		9,143		4,350		(18)	5		(12)	13,468		(3)
Beginning Balance, in shares at Dec. 31, 2017	700,000,000		700,000,000														100																			90,000,000					100
Beginning Balance (member's equity) at Dec. 31, 2017														11,361	11,368	(7)														7,949	5,618	5,614		4						4,121
Beginning Balance (parent) at Dec. 31, 2017	$ 41,739																$ 13,468																			$ 3,163	762	2,670	(269)		$ 1,662	860	802
Net income	622				620						620		2				237				235						235		2
Net income (attributable to parent)	620													323	323		235													177	103	103				$ (25)			(25)	100	$ 110		110
Other comprehensive income (loss)	11						13	(3)		1	11			1		1	2						2				2
Common stock issuances, including dividend reinvestment and employee benefits, shares			1,000,000
Common stock issuances, including dividend reinvestment and employee benefits	47			47							47
Distributions to noncontrolling interest in subsidiaries	(1)												(1)
Distributions/dividends to parent	(625)				(625)						(625)			(250)	(250)
Other	7				13	[2]		(13)	[2]				7				(1)	[2]	(1)	[2]	6	[2]		(6)	[2]		(1)	[2]				6	[3]	(6)	[3]
Ending Balance at Mar. 31, 2018	$ 41,798		$ 1	$ 38,839	$ 3,021		$ 3	$ (4)		$ (68)	$ 41,792		$ 6				$ 13,703		$ 9,142		$ 4,591		$ (16)	$ (1)		$ (12)	$ 13,704		$ (1)
Ending Balance, in shares at Mar. 31, 2018	701,000,000		701,000,000														100																			90,000,000					100
Ending Balance (member's equity) at Mar. 31, 2018														$ 11,435	$ 11,441	$ (6)														$ 8,126	$ 5,721	$ 5,723		$ (2)						$ 4,221
Ending Balance (parent) at Mar. 31, 2018	$ 41,792																$ 13,704																			$ 3,138	$ 762	$ 2,670	$ (294)		$ 1,772	$ 860	$ 912
[1]	Cumulative-effect adjustment due to implementation of a new accounting standard related to stock-based compensation and the associated income taxes.
[2]	Amounts in Retained Earnings and Accumulated Other Comprehensive Loss represent a cumulative-effect adjustment due to implementation of a new accounting standard related to Financial Instruments Classification and Measurement. See Note 1 for more information.
[3]	Amounts in Member's Equity and Accumulated Other Comprehensive Income (Loss) represent a cumulative-effect adjustment due to implementation of a new accounting standard related to Financial Instruments Classification and Measurement. See Note 1 for more information.

Organization and Basis of Prese

Organization and Basis of Presentation	3 Months Ended
	Mar. 31, 2018
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 Duke Energy Corporation • • • • • • • • • • • • • • • • Duke Energy Carolinas, LLC • • • • • • • • • • • • • • Progress Energy, Inc. • • • • • • • • • • • • • • • Duke Energy Progress, LLC • • • • • • • • • • • • • • Duke Energy Florida, LLC • • • • • • • • • • • • • • Duke Energy Ohio, Inc. • • • • • • • • • • • • • • Duke Energy Indiana, LLC • • • • • • • • • • • • • • Piedmont Natural Gas Company, Inc. • • • • • • • • • • • • • Tables within the notes may not sum across due to (i) Progress Energy's consolidation of Duke Energy Progress, Duke Energy Florida and other subsidiaries that are not registrants and (ii) subsidiaries that are not registrants but included in the consolidated Duke Energy balances. ORGANIZATION AND BASIS OF PRESENTATION NATURE OF OPERATIONS AND BASIS OF CONSOLIDATION Duke Energy Corporation (collectively with its subsidiaries, Duke Energy) is an energy company headquartered in Charlotte, North Carolina, subject to regulation by the Federal Energy Regulatory Commission (FERC). Duke Energy operates in the United States (U.S.) primarily through its direct and indirect subsidiaries. Certain Duke Energy subsidiaries are also subsidiary registrants, including Duke Energy Carolinas, LLC (Duke Energy Carolinas); Progress Energy, Inc. (Progress Energy); Duke Energy Progress, LLC (Duke Energy Progress); Duke Energy Florida, LLC (Duke Energy Florida); Duke Energy Ohio, Inc. (Duke Energy Ohio), Duke Energy Indiana, LLC (Duke Energy Indiana) and Piedmont Natural Gas Company, Inc. (Piedmont). When discussing Duke Energy’s consolidated financial information, it necessarily includes the results of its separate subsidiary registrants (collectively referred to as the Subsidiary Registrants), which, along with Duke Energy, are collectively referred to as the Duke Energy Registrants. These Condensed Consolidated Financial Statements include, after eliminating intercompany transactions and balances, the accounts of the Duke Energy Registrants and subsidiaries where the respective Duke Energy Registrants have control. These Condensed Consolidated Financial Statements also reflect the Duke Energy Registrants’ proportionate share of certain jointly owned generation and transmission facilities. Substantially all of the Subsidiary Registrants' operations qualify for regulatory accounting. Duke Energy Carolinas is a regulated public utility primarily engaged in the generation, transmission, distribution and sale of electricity in portions of North Carolina and South Carolina. Duke Energy Carolinas is subject to the regulatory provisions of the North Carolina Utilities Commission (NCUC), Public Service Commission of South Carolina (PSCSC), U.S. Nuclear Regulatory Commission (NRC) and FERC. Progress Energy is a public utility holding company headquartered in Raleigh, North Carolina, subject to regulation by FERC. Progress Energy conducts operations through its wholly owned subsidiaries, Duke Energy Progress and Duke Energy Florida. Duke Energy Progress is a regulated public utility primarily engaged in the generation, transmission, distribution and sale of electricity in portions of North Carolina and South Carolina. Duke Energy Progress is subject to the regulatory provisions of the NCUC, PSCSC, NRC and FERC. Duke Energy Florida is a regulated public utility primarily engaged in the generation, transmission, distribution and sale of electricity in portions of Florida. Duke Energy Florida is subject to the regulatory provisions of the Florida Public Service Commission (FPSC), NRC and FERC. Duke Energy Ohio is a regulated public utility primarily engaged in the transmission and distribution of electricity in portions of Ohio and Kentucky, the generation and sale of electricity in portions of Kentucky and the transportation and sale of natural gas in portions of Ohio and Kentucky. Duke Energy Ohio conducts competitive auctions for retail electricity supply in Ohio whereby the energy price is recovered from retail customers and recorded in Operating Revenues on the Condensed Consolidated Statements of Operations and Comprehensive Income. Operations in Kentucky are conducted through its wholly owned subsidiary, Duke Energy Kentucky, Inc. (Duke Energy Kentucky). References herein to Duke Energy Ohio collectively include Duke Energy Ohio and its subsidiaries, unless otherwise noted. Duke Energy Ohio is subject to the regulatory provisions of the Public Utilities Commission of Ohio (PUCO), Kentucky Public Service Commission (KPSC) and FERC. Duke Energy Indiana is a regulated public utility primarily engaged in the generation, transmission, distribution and sale of electricity in portions of Indiana. Duke Energy Indiana is subject to the regulatory provisions of the Indiana Utility Regulatory Commission (IURC) and FERC. Piedmont is a regulated public utility primarily engaged in the distribution of natural gas in portions of North Carolina, South Carolina and Tennessee. Piedmont is subject to the regulatory provisions of the NCUC, PSCSC, Tennessee Public Utility Commission (TPUC) and FERC. BASIS OF PRESENTATION These Condensed Consolidated Financial Statements have been prepared in accordance with generally accepted accounting principles (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/A for the year ended December 31, 2017 . The information in these combined notes relates to each of the Duke Energy Registrants as noted in the Index to Combined Notes to Condensed Consolidated Financial Statements. However, none of the registrants make any representations as to information related solely to Duke Energy or the subsidiaries of Duke Energy other than itself. These Condensed Consolidated Financial Statements, in the opinion of the respective companies’ management, reflect all normal recurring adjustments necessary to fairly present the financial position and results of operations of each of the Duke Energy Registrants. Amounts reported in Duke Energy’s interim Condensed Consolidated Statements of Operations and each of the Subsidiary Registrants’ interim Condensed Consolidated Statements of Operations and Comprehensive Income are not necessarily indicative of amounts expected for the respective annual periods due to effects of seasonal temperature variations on energy consumption, regulatory rulings, timing of maintenance on electric generating units, changes in mark-to-market valuations, changing commodity prices and other factors. In preparing financial statements that conform to GAAP, management must make estimates and assumptions that affect the reported amounts of assets and liabilities, the reported amounts of revenues and expenses, and the disclosure of contingent assets and liabilities at the date of the financial statements. Actual results could differ from those estimates. Certain prior year amounts have been reclassified to conform to the current year presentation. REVENUE Duke Energy recognizes revenue as customers obtain control of promised goods and services in an amount that reflects consideration expected in exchange for those goods or services. Generally, the delivery of electricity and natural gas results in the transfer of control to customers at the time the commodity is delivered and the amount of revenue recognized is equal to the amount billed to each customer, including estimated volumes delivered when billings have not yet occurred. See Note 12 for further information. CASH, CASH EQUIVALENTS AND RESTRICTED CASH Duke Energy, Progress Energy and Duke Energy Florida have restricted cash balances related primarily to collateral assets, escrow deposits and variable interest entities (VIEs). See Note 11 for additional information. Restricted cash amounts are included in Other within Current Assets and Other Noncurrent Assets. The following table presents the components of Cash, cash equivalents and restricted cash included in the Condensed Consolidated Balance Sheets. March 31, 2018 December 31, 2017 Duke Duke Duke Progress Energy Duke Progress Energy Energy Energy Florida Energy Energy Florida Current Assets Cash and cash equivalents $ 421 $ 20 $ 6 $ 358 $ 40 $ 13 Other 149 13 13 138 40 40 Other Noncurrent Assets Other 9 6 — 9 7 — Total Cash, cash equivalents and restricted cash $ 579 $ 39 $ 19 $ 505 $ 87 $ 53 INVENTORY Inventory is used for operations and is recorded primarily using the average cost method. Inventory related to regulated operations is valued at historical cost. Inventory related to nonregulated operations is valued at the lower of cost or market. Materials and supplies are recorded as inventory when purchased and subsequently charged to expense or capitalized to property, plant and equipment when installed. Inventory, including excess or obsolete inventory, is written-down to the lower of cost or market value. Once inventory has been written-down, it creates a new cost basis for the inventory that is not subsequently written-up. Provisions for inventory write-offs were not material at March 31, 2018 , and December 31, 2017 . The components of inventory are presented in the tables below. March 31, 2018 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Materials and supplies $ 2,293 $ 763 $ 1,095 $ 767 $ 329 $ 82 $ 310 $ 1 Coal 551 176 221 125 96 13 141 — Natural gas, oil and other fuel 305 41 221 110 110 13 2 28 Total inventory $ 3,149 $ 980 $ 1,537 $ 1,002 $ 535 $ 108 $ 453 $ 29 December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Materials and supplies $ 2,293 $ 744 $ 1,118 $ 774 $ 343 $ 82 $ 309 $ 2 Coal 603 192 255 139 116 17 139 — Natural gas, oil and other fuel 354 35 219 104 115 34 2 64 Total inventory $ 3,250 $ 971 $ 1,592 $ 1,017 $ 574 $ 133 $ 450 $ 66 EXCISE TAXES Certain excise taxes levied by state or local governments are required to be paid even if not collected from the customer. These taxes are recognized on a gross basis. Otherwise, excise taxes are accounted for on a net basis. Excise taxes accounted for on a gross basis within both Operating revenues and Property and other taxes on the Condensed Consolidated Statements of Operations were as follows. Three Months Ended March 31, (in millions) 2018 2017 Duke Energy $ 99 $ 91 Duke Energy Carolinas 8 9 Progress Energy 54 46 Duke Energy Progress 5 5 Duke Energy Florida 49 41 Duke Energy Ohio 30 28 Duke Energy Indiana 6 7 Piedmont 1 1 NEW ACCOUNTING STANDARDS The new accounting standards adopted for 2018 and 2017 had no material impact on the presentation or results of operations, cash flows or financial position of the Duke Energy Registrants. While immaterial, adoption of the following accounting standards had the most significant impact on the Duke Energy results of operations, cash flows and financial position for the three months ended March 31, 2018 . Revenue from Contracts with Customers. In May 2014, the Financial Accounting Standards Board (FASB) issued revised accounting guidance for revenue recognition from contracts with customers. The core principle of this guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration expected in exchange for those goods or services. The amendments also required disclosure of sufficient information to allow users to understand the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. The majority of Duke Energy’s revenue is in scope of the new guidance. Other revenue arrangements, such as alternative revenue programs and certain purchase power agreements (PPAs) and lighting tariffs accounted for as leases, are excluded from the scope of this guidance and, therefore, are accounted for and evaluated for separate presentation and disclosure under other relevant accounting guidance. Duke Energy elected the modified retrospective method of adoption effective January 1, 2018. Under the modified retrospective method of adoption, prior year reported results are not restated. Adoption of this standard did not result in a material change in the timing or pattern of revenue recognition and a cumulative-effect adjustment was not recorded at January 1, 2018. Duke Energy utilized certain practical expedients including applying this guidance to open contracts at the date of adoption, expensing costs to obtain a contract where the amortization period of the asset would have been one year or less, ignoring the effects of a significant financing when the period between transfer of the good or service and payment is one year or less and recognizing revenues for certain contracts under the invoice practical expedient, which allows revenue recognition to be consistent with invoiced amounts (including estimated billings) provided certain criteria are met, including consideration of whether the invoiced amounts reasonably represent the value provided to customers. In preparation for adoption, Duke Energy identified material revenue streams and reviewed representative contracts and tariffs, including those associated with certain long-term customer contracts such as wholesale contracts, PPAs, and other customer arrangements. Duke Energy also monitored the activities of the power and utilities industry revenue recognition task force and has reviewed published positions on specific industry issues to evaluate the impact, if any, on Duke Energy’s specific contracts and conclusions. Duke Energy applied the available practical expedient to portfolios of tariffs and contracts with similar characteristics. The vast majority of sales, including energy provided to retail customers, are from tariff offerings that provide natural gas or electricity without a defined contractual term ("at-will"). In most circumstances, revenue from contracts with customers is equivalent to the electricity or natural gas supplied and billed in that period (including estimated billings). As such, adoption of the new rules did not result in a shift in the timing or pattern of revenue recognition for such sales. While there have been changes to the captions and descriptions of revenues in Duke Energy’s financial statements, the most significant impact as a result of adopting the standard are additional disclosures around the nature, amount, timing, and uncertainty of revenues and cash flows arising from contracts with customers. See Note 12 for further information. Financial Instruments Classification and Measurement. In January 2018, Duke Energy adopted FASB guidance, which revised the classification and measurement of certain financial instruments. The adopted guidance changes the presentation of realized and unrealized gains and losses in certain equity securities that were previously recorded in accumulated other comprehensive income (AOCI). These gains and losses are now recorded in net income. An entity's equity investments that are accounted for under the equity method of accounting are not included within the scope of the new guidance. This guidance had a minimal impact on the Duke Energy Registrant's Condensed Consolidated Statements of Operations and Comprehensive Income as changes in the fair value of most of the Duke Energy Registrants' equity securities are deferred as regulatory assets or liabilities pursuant to accounting guidance for regulated operations. The resulting adjustment of unrealized gains and losses in AOCI to retained earnings was immaterial. The primary impact to Duke Energy as a result of implementing this guidance is adding disclosure requirements to present separately the financial assets and financial liabilities by measurement category and form of financial asset. See Notes 9 and 10 for further information. Statement of Cash Flows. In November 2016, the FASB issued revised accounting guidance to reduce diversity in practice for the presentation and classification of restricted cash on the Condensed Consolidated Statements of Cash Flows. Under the updated guidance, restricted cash and restricted cash equivalents are included within beginning-of-period and end-of-period cash and cash equivalents on the Condensed Consolidated Statements of Cash Flows. Duke Energy adopted this guidance on January 1, 2018. The guidance has been applied using a retrospective transition method to each period presented. The adoption by Duke Energy of the revised guidance resulted in a change to the amount of Cash, cash equivalents and restricted cash explained when reconciling the beginning-of-period and end-of-period total amounts shown on the Condensed Consolidated Statements of Cash Flows. In addition, a reconciliation has been provided of Cash, cash equivalents and restricted cash reported within the Condensed Consolidated Balance Sheets that sums to the total of the same such amounts in the Condensed Consolidated Statements of Cash Flows. Prior to adoption, the Duke Energy Registrants reflected changes in noncurrent restricted cash within Cash Flows from Investing Activities and changes in current restricted cash within Cash Flows from Operating Activities on the Condensed Consolidated Statement of Cash Flows. In August 2016, the FASB issued accounting guidance addressing diversity in practice for eight separate cash flow issues. The guidance requires entities to classify distributions received from equity method investees using either the cumulative earnings approach or the nature of the distribution approach. Duke Energy adopted this guidance on January 1, 2018, and has elected the nature of distribution approach. Duke Energy will categorize all distributions received based on legal documentation describing the nature of the activities generating the distribution. Cash inflows resulting in a return on investment (surplus) will be reflected in Cash Flows from Operating Activities on the Condensed Consolidated Statements of Cash Flows, whereas cash inflows resulting in a return of investment (capital) will be reflected in Cash Flows from Investing Activities on the Condensed Consolidated Statements of Cash Flows. The guidance has been applied using the retrospective transition method to each period presented. There are no changes to the Condensed Consolidated Statements of Cash Flows for the periods presented as a result of this accounting change. Retirement Benefits. In March 2017, the FASB issued revised accounting guidance for the presentation of net periodic costs related to benefit plans. Previous guidance required the aggregation of all the components of net periodic costs on the Condensed Consolidated Statement of Operations and did not require the disclosure of the location of net periodic costs on the Condensed Consolidated Statement of Operations. Under the amended guidance, the service cost component of net periodic costs is included within Operating Income within the same line as other compensation expenses. All other components of net periodic costs are outside of Operating Income. In addition, the updated guidance permits only the service cost component of net periodic costs to be capitalized to Inventory or Property, Plant and Equipment. This represents a change from previous guidance, which permitted all components of net periodic costs to be eligible for capitalization. Duke Energy adopted this guidance on January 1, 2018. Under previous guidance, Duke Energy presented the total non-capitalized net periodic costs within Operation, maintenance and other on the Condensed Consolidated Statement of Operations. The adoption of this guidance resulted in a retrospective change to reclassify the presentation of the non-service cost (benefit) components of net periodic costs to Other income and expenses. Duke Energy utilized the practical expedient for retrospective presentation. The change in components of net periodic costs eligible for capitalization is applicable prospectively. Since Duke Energy’s service cost component is greater than the total net periodic costs, the change results in increased capitalization of net periodic costs, higher Operation, maintenance and other and higher Other income and expenses. The resulting prospective impact to Duke Energy is an immaterial increase in Net Income. See Note 15 for further information. For Duke Energy, the retrospective change resulted in higher Operation, maintenance and other and higher Other income and expenses, net, of $156 million , $131 million and $96 million for the years ended December 31, 2017, 2016 and 2015, respectively. There was no change to Net Income for these prior periods. The following new Accounting Standards Updates (ASUs) have been issued, but have not yet been adopted by Duke Energy, as of March 31, 2018 . Leases. In February 2016, the FASB issued revised accounting guidance for leases. The core principle of this guidance is that a lessee should recognize the assets and liabilities that arise from leases on the balance sheet. For Duke Energy, this guidance is effective for interim and annual periods beginning January 1, 2019. The guidance will be applied using a modified retrospective approach. Upon adoption, Duke Energy expects to elect certain of the practical expedients upon adoption: Practical Expedient Description Package of transition practical expedients (for leases commenced prior to adoption date and must be adopted as a package) Do not need to reassess whether any expired or existing contracts are/or contain leases, do not need to reassess the lease classification for any expired or existing leases and do not need to reassess initial direct costs for any existing leases. Short-term lease expedient (elect by class of underlying asset) Elect as an accounting policy to not apply the recognition requirements to short-term leases by asset class. Lease and non-lease components (elect by class of underlying asset) Duke Energy will likely elect as an accounting policy to not separate non-lease components from lease components and instead account for each lease and associated non-lease component as a single lease component. Hindsight expedient (when determining lease term) Elect to use hindsight to determine the lease term. Easement expedient Elect to carry forward current accounting treatment for existing easements. Duke Energy is currently evaluating the financial statement impact of adopting this standard and is continuing to monitor industry implementation issues, including pipeline laterals, pole attachments and renewable PPAs. Other than an expected increase in assets and liabilities, the ultimate impact of the new standard has not yet been determined. Significant system enhancements, including additional processes and controls, will be required to facilitate the identification, tracking and reporting of potential leases based upon requirements of the new lease standard. Duke Energy has begun the implementation of a third-party software tool to help with the adoption and ongoing accounting under the new standard.

Business Segments

Business Segments	3 Months Ended
	Mar. 31, 2018
Segment Reporting [Abstract]
Business Segments	BUSINESS SEGMENTS Operating segments are determined based on information used by the chief operating decision-maker in deciding how to allocate resources and evaluate the performance of the business. Duke Energy evaluates segment performance based on segment income. Segment income is defined as income from continuing operations net of income attributable to noncontrolling interests. Segment income includes intercompany revenues and expenses that are eliminated on the Condensed Consolidated Financial Statements. Certain governance costs are allocated to each segment. In addition, direct interest expense and income taxes are included in segment income. Duke Energy Duke Energy's segment structure includes the following segments: Electric Utilities and Infrastructure, Gas Utilities and Infrastructure and Commercial Renewables. The Electric Utilities and Infrastructure segment includes Duke Energy's regulated electric utilities in the Carolinas, Florida and the Midwest. The regulated electric utilities conduct operations through the Subsidiary Registrants that are substantially all regulated and, accordingly, qualify for regulatory accounting treatment. Electric Utilities and Infrastructure also includes Duke Energy's electric transmission infrastructure investments. The Gas Utilities and Infrastructure segment includes Piedmont, Duke Energy's natural gas local distribution companies in Ohio and Kentucky, and Duke Energy's natural gas storage and midstream pipeline investments. Gas Utilities and Infrastructure's operations are substantially all regulated and, accordingly, qualify for regulatory accounting treatment. Commercial Renewables is primarily comprised of nonregulated utility scale wind and solar generation assets located throughout the U.S. The remainder of Duke Energy’s operations is presented as Other, which is primarily comprised of interest expense on holding company debt, unallocated corporate costs and Duke Energy’s wholly owned captive insurance company, Bison Insurance Company Limited (Bison). Other also includes Duke Energy's 17.5 percent interest in National Methanol Company (NMC), a large regional producer of methyl tertiary butyl ether located in Saudi Arabia. The investment in NMC is accounted for under the equity method of accounting. Business segment information is presented in the following tables. Segment assets presented exclude intercompany assets. Three Months Ended March 31, 2018 Electric Gas Total Utilities and Utilities and Commercial Reportable (in millions) Infrastructure Infrastructure Renewables Segments Other Eliminations Consolidated Unaffiliated revenues $ 5,315 $ 702 $ 101 $ 6,118 $ 17 $ — $ 6,135 Intersegment revenues 8 25 — 33 18 (51 ) — Total revenues $ 5,323 $ 727 $ 101 $ 6,151 $ 35 $ (51 ) $ 6,135 Segment income (loss) (a)(b)(c) $ 750 $ 116 $ 20 $ 886 $ (266 ) $ — $ 620 Add back noncontrolling interests 2 Net income $ 622 Segment assets $ 120,021 $ 11,396 $ 4,265 $ 135,682 $ 2,682 $ 177 $ 138,541 Three Months Ended March 31, 2017 Electric Gas Total Utilities and Utilities and Commercial Reportable (in millions) Infrastructure Infrastructure Renewables Segments Other Eliminations Consolidated Unaffiliated revenues $ 4,939 $ 648 $ 128 $ 5,715 $ 14 $ — $ 5,729 Intersegment revenues 8 22 — 30 19 (49 ) — Total revenues $ 4,947 $ 670 $ 128 $ 5,745 $ 33 $ (49 ) $ 5,729 Segment income (loss) $ 635 $ 133 $ 25 $ 793 $ (77 ) $ — $ 716 Add back noncontrolling interests 1 Net income $ 717 (a) Electric Utilities and Infrastructure includes regulatory charges related to NCUC orders and settlements. See Note 3 for additional information. (b) Gas Utilities and Infrastructure includes an impairment of the investment in Constitution Pipeline Company, LLC (Constitution). See Note 3 for additional information. (c) Other includes the loss on the sale of the retired Beckjord generating station (Beckjord) described below and a valuation allowance recorded against the alternative minimum tax credits subject to sequestration. See Note 16 for additional information on the valuation allowance. Beckjord, a nonregulated facility retired during 2014, was sold on February 26, 2018, at a pretax loss of $106 million recorded within (Loss) Gains on Sales of Other Assets and Other, net and $1 million recorded within Operation, maintenance and other on Duke Energy's Condensed Consolidated Statements of Operations. The sale included the transfer of coal ash basins and other real property and indemnification from any and all potential future claims related to the property, whether arising under environmental laws or otherwise. Duke Energy Ohio Duke Energy Ohio has two reportable operating segments, Electric Utilities and Infrastructure and Gas Utilities and Infrastructure. Electric Utilities and Infrastructure transmits and distributes electricity in portions of Ohio and generates, distributes and sells electricity in portions of Northern Kentucky. Gas Utilities and Infrastructure transports and sells natural gas in portions of Ohio and Northern Kentucky. 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 7 for additional information on related party transactions. Three Months Ended March 31, 2018 Electric Gas Total Utilities and Utilities and Reportable (in millions) Infrastructure Infrastructure Segments Other Eliminations Consolidated Total revenues $ 336 $ 174 $ 510 $ 14 $ — $ 524 Segment income (loss)/Net income (loss) (a) 33 34 67 (92 ) — (25 ) Segment assets $ 5,165 $ 2,709 $ 7,874 $ 25 $ (3 ) $ 7,896 Three Months Ended March 31, 2017 Electric Gas Total Utilities and Utilities and Reportable (in millions) Infrastructure Infrastructure Segments Other Consolidated Total revenues $ 337 $ 170 $ 507 $ 11 $ 518 Segment income (loss)/Net income (loss) 24 26 50 (8 ) 42 (a) Other includes the loss on the sale of the retired Beckjord generating station described above.

Regulatory Matters

Regulatory Matters	3 Months Ended
	Mar. 31, 2018
Regulated Operations [Abstract]
Regulatory Matters	REGULATORY MATTERS RATE-RELATED INFORMATION The NCUC, PSCSC, FPSC, IURC, PUCO, TPUC and KPSC approve rates for retail electric and natural gas services within their states. The FERC approves rates for electric sales to wholesale customers served under cost-based rates (excluding Ohio and Indiana), as well as sales of transmission service. The FERC also regulates certification and siting of new interstate natural gas pipeline projects. Duke Energy Carolinas and Duke Energy Progress Ash Basin Closure Costs Deferral – North Carolina 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 is still awaiting an order in its case and, as such, 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 the William States Lee Combined Cycle Facility discussed below, grid improvement projects, AMI, investments in customer service technologies, costs of complying with coal combustion residuals (CCR) regulations and the North Carolina Coal Ash Management Act of 2014 (Coal Ash Act) and recovery of costs related to licensing and development of the William States Lee III Nuclear Station (Lee Nuclear Station) discussed below. On February 28, 2018, Duke Energy Carolinas and the North Carolina Public Staff filed an Agreement and Stipulation of Partial Settlement resolving certain portions of the proceeding, pending NCUC approval. Terms of the settlement include a return on equity of 9.9 percent and a capital structure of 52 percent equity and 48 percent debt. As a result of the settlement, Duke Energy Carolinas recorded a pretax charge of approximately $4 million to Operations, maintenance and other on the Condensed Consolidated Statements of Operations. The settlement does not include agreement on portions of the rate case relating to recovery of costs for Lee Nuclear Station and coal ash basin deferred costs, a rider for recovery of grid improvement projects or the manner in which the Federal Tax Cut and Jobs Act (Tax Act) should be addressed in this case, which will be decided by the NCUC separately. Taking into consideration the settled portions and Duke Energy Carolinas’ requested recovery of the non-settled portions, the requested base rate increase is reduced to approximately $472 million . The evidentiary hearing for this matter concluded on March 22, 2018, and a decision and revised customer rates are expected by mid–2018. Duke Energy Carolinas cannot predict the outcome of this matter. FERC Formula Rate Matter On July 31, 2017, Piedmont Municipal Power Agency (PMPA) filed a complaint with FERC against Duke Energy Carolinas alleging that Duke Energy Carolinas misapplied the formula rate under the PPA between the parties by including in its rates amortization expense associated with regulatory assets and recorded in a certain account without FERC approval. Duke Energy Carolinas disagreed with PMPA as it believed it was properly applying its FERC filed rate. On February 15, 2018, FERC issued an order ruling in favor of PMPA and ordered Duke Energy Carolinas to refund to PMPA all amounts improperly collected under the PPA. Duke Energy Carolinas has issued to PMPA and similarly situated wholesale customers refunds of approximately $25 million . William States Lee Combined Cycle Facility On April 9, 2014, the PSCSC granted Duke Energy Carolinas and North Carolina Electric Membership Corporation (NCEMC) a Certificate of Environmental Compatibility and Public Convenience and Necessity for the construction and operation of a 750-megawatt (MW) combined-cycle natural gas-fired generating plant at Duke Energy Carolinas' existing William States Lee Generating Station in Anderson, South Carolina. Duke Energy Carolinas began construction in July 2015 and its share of the cost to build the facility was approximately $650 million , including allowance for funds used during construction (AFUDC). The project commenced commercial operation on April 5, 2018. NCEMC will own approximately 13 percent of the project. Lee Nuclear Station In December 2007, Duke Energy Carolinas applied to the NRC for combined operating licenses (COLs) for two Westinghouse Electric Company (Westinghouse) AP1000 reactors for the proposed William States Lee III Nuclear Station to be located at a site in Cherokee County, South Carolina. The NCUC and PSCSC concurred with the prudency of Duke Energy Carolinas incurring certain project development and preconstruction costs through several separately issued orders, although full cost recovery is not guaranteed. In December 2016, the NRC issued a COL for each reactor. Duke Energy Carolinas is not required to build the nuclear reactors as a result of the COLs being issued. On March 29, 2017, Westinghouse filed for voluntary Chapter 11 bankruptcy in the U.S. Bankruptcy Court for the Southern District of New York. As part of its 2017 North Carolina Rate Case discussed above, Duke Energy Carolinas is seeking NCUC approval to cancel the development of the Lee Nuclear Station project due to the Westinghouse bankruptcy filing and other market activity and is requesting recovery of incurred licensing and development costs. Duke Energy Carolinas will maintain the license issued by the NRC in December 2016 as an option for potential future development. AFUDC was suspended effective January 1, 2018, as currently only immaterial costs to maintain the license are being incurred. As of March 31, 2018, Duke Energy Carolinas has incurred approximately $558 million of costs, including AFUDC, related to the project. These project costs are included in Net property, plant and equipment on Duke Energy Carolinas’ Condensed Consolidated Balance Sheets. Duke Energy Carolinas cannot predict the outcome of this matter. Duke Energy Progress 2017 North Carolina Rate Case On June 1, 2017, Duke Energy Progress filed an application with the NCUC for a rate increase for retail customers of approximately $477 million , which represented an approximate 14.9 percent increase in annual base revenues. Subsequent to the filing, Duke Energy Progress adjusted the requested amount to $420 million , representing an approximate 13 percent increase. The rate increase is driven by capital investments subsequent to the previous base rate case, costs of complying with CCR regulations and the Coal Ash Act, costs relating to storm recovery, investments in customer service technologies and recovery of costs associated with renewable purchased power. On December 16, 2016, Duke Energy Progress filed a petition with the NCUC requesting an accounting order to defer certain costs incurred in connection with response to Hurricane Matthew and other significant storms in 2016. The final estimate of incremental operation and maintenance and capital costs of $116 million was filed with the NCUC in September 2017. On July 10, 2017, the NCUC consolidated Duke Energy Progress' storm deferral request into the Duke Energy Progress rate case docket for decision. On November 22, 2017, Duke Energy Progress and the North Carolina Public Staff filed an Agreement and Stipulation of Partial Settlement resolving certain portions of the proceeding. Terms of the settlement included a return on equity of 9.9 percent and a capital structure of 52 percent equity and 48 percent debt. As a result of the settlement, in 2017 Duke Energy Progress recorded pretax charges totaling approximately $25 million to Impairment charges and Operation, maintenance and other on the Condensed Consolidated Statements of Operations, principally related to disallowances from rate base of certain projects at the Mayo and Sutton plants. On February 23, 2018, the NCUC issued an order approving the stipulation. The order also included the following material components not covered in the stipulation: • recovery of the remaining $234 million of deferred coal ash basin closure costs over a five -year period with a return at Duke Energy Progress' weighted average cost of capital, excluding $9.5 million of retail deferred coal ash basin costs related to ash hauling at Duke Energy Progress' Asheville Plant; • assessment of a $30 million management penalty ratably over a five-year period by reducing the annual recovery of the deferred coal ash costs; • denial of Duke Energy Progress' request for recovery of future estimated ongoing annual coal ash costs of $129 million with approval to defer such costs with a return at Duke Energy Progress' weighted average cost of capital, to be considered for recovery in the next rate case; • and approval to recover $51 million of the approximately $80 million deferred storm costs over a five -year period with amortization beginning in October 2016. The order did not allow the deferral of the associated capital costs or a return on the deferred balance during the deferral period. The order also impacted certain amounts that were similarly recorded on Duke Energy Carolinas' Condensed Consolidated Balance Sheets. As a result of the order, Duke Energy Progress and Duke Energy Carolinas recorded pretax charges of $68 million and $14 million , respectively, in the first quarter of 2018 to Impairment charges, Operation, maintenance and other and Interest Expense on the Condensed Consolidated Statements of Operations. These charges primarily related to the coal ash basin disallowance and management penalty and deferred storm cost adjustments. Revised customer rates became effective on March 16, 2018. South Carolina Rate Case In December 2016, the PSCSC approved a rate case settlement agreement among the Office of Regulatory Staff, intervenors and Duke Energy Progress. Terms of the settlement agreement included an approximate $56 million increase in revenues over a two-year period. An increase of approximately $38 million in revenues was effective January 1, 2017, and an additional increase of approximately $18.5 million in revenues was effective January 1, 2018. Duke Energy Progress amortized approximately $18.5 million from the cost of removal reserve in 2017. Other settlement terms included a rate of return on equity of 10.1 percent , recovery of coal ash costs incurred from January 1, 2015, through June 30, 2016, over a 15 ‑ year period and ongoing deferral of allocated ash basin closure costs from July 1, 2016, until the next base rate case. The settlement also provides that Duke Energy Progress will not seek an increase in rates in South Carolina to occur prior to 2019, with limited exceptions. Western Carolinas Modernization Plan On November 4, 2015, Duke Energy Progress announced a Western Carolinas Modernization Plan, which included retirement of the existing Asheville coal-fired plant, the construction of two 280‑MW combined-cycle natural gas plants having dual-fuel capability, with the option to build a third natural gas simple cycle unit in 2023 based upon the outcome of initiatives to reduce the region's power demand. The plan also included upgrades to existing transmission lines and substations, installation of solar generation and a pilot battery storage project. These investments will be made within the next seven years. Duke Energy Progress is also working with the local natural gas distribution company to upgrade an existing natural gas pipeline to serve the natural gas plant. On March 28, 2016, the NCUC issued an order approving a CPCN for the new combined-cycle natural gas plants, but denying the CPCN for the contingent simple cycle unit without prejudice to Duke Energy Progress to refile for approval in the future. On March 28, 2018, Duke Energy Progress filed an annual progress report for the construction of the combined-cycle plants with the NCUC, with an estimated cost of $893 million . Site preparation activities for the combined-cycle plants are complete and construction of these plants began in 2017, with an expected in-service date in late 2019. Duke Energy Progress plans to file for future approvals related to the proposed solar generation and pilot battery storage project. The carrying value of the 376 -MW Asheville coal-fired plant, including associated ash basin closure costs, of $365 million and $385 million is included in Generation facilities to be retired, net on Duke Energy Progress' Condensed Consolidated Balance Sheets as of March 31, 2018 , and December 31, 2017 , respectively. Duke Energy Progress' request for a regulatory asset at the time of retirement with amortization over a 10 -year period was approved by the NCUC on February 23, 2018. Shearon Harris Nuclear Plant Expansion In 2006, Duke Energy Progress selected a site at Harris to evaluate for possible future nuclear expansion. On February 19, 2008, Duke Energy Progress filed its COL application with the NRC for two Westinghouse AP1000 reactors at Harris, which the NRC docketed for review. On May 2, 2013, Duke Energy Progress filed a letter with the NRC requesting the NRC to suspend its review activities associated with the COL at the Harris site. The NCUC and PSCSC approved deferral of retail costs. Total deferred costs were approximately $47 million as of December 31, 2017, and are recorded in Regulatory assets on Duke Energy Progress’ Condensed Consolidated Balance Sheets. On November 17, 2016, the FERC approved Duke Energy Progress’ rate recovery request filing for the wholesale ratepayers’ share of the abandonment costs, including a debt only return to be recovered through revised formula rates and amortized over a 15 -year period beginning May 1, 2014. As part of the settlement agreement for the 2017 North Carolina Rate Case discussed above, Duke Energy Progress will amortize the regulatory asset over an eight -year period. NCUC approved the settlement on February 23, 2018. Duke Energy Florida Storm Restoration Cost Recovery In September 2017, Duke Energy Florida’s service territory suffered significant damage from Hurricane Irma, resulting in approximately 1.3 million customers experiencing outages. In the fourth quarter of 2017, Duke Energy Florida also incurred preparation costs related to Hurricane Nate. On December 28, 2017, Duke Energy Florida filed a petition with the FPSC to recover incremental storm restoration costs for hurricanes Irma and Nate and to replenish the storm reserve. The estimated recovery amount is approximately $513 million , which includes reestablishment of a $132 million storm reserve. On February 6, 2018, the FPSC approved a stipulation that would apply tax savings resulting from the Tax Act toward storm costs effective January 2018 in lieu of implementing a storm surcharge. Storm costs are currently expected to be fully recovered by approximately mid-2021. The evidentiary hearing in this matter is scheduled for the week of October 15, 2018. At March 31, 2018, Duke Energy Florida's Condensed Consolidated Balance Sheets included approximately $338 million of recoverable costs under the FPSC's storm rule in Regulatory assets within Current Assets and Other Noncurrent Assets related to storm recovery. Citrus County Combined Cycle Facility On October 2, 2014, the FPSC granted Duke Energy Florida a Determination of Need for the construction of a 1,640-MW combined-cycle natural gas plant in Citrus County, Florida. On May 5, 2015, the Florida Department of Environmental Protection approved Duke Energy Florida's Site Certification Application. The project has received all required permits and approvals and construction began in October 2015. The facility is expected to be commercially available by the end of 2018 at an estimated cost of $1.5 billion , including AFUDC. On April 2, 2018, Duke Energy Florida filed a petition seeking approval to include in base rates the revenue requirements associated with the new facility. The annual retail revenue requirement is approximately $200 million . The plant will receive natural gas from the Sabal Trail Transmission, LLC (Sabal Trail) pipeline discussed below. Duke Energy Ohio 2017 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. On February 15, 2018, the procedural schedule was suspended to facilitate ongoing settlement discussions. On April 13, 2018, Duke Energy Ohio filed a Motion to consolidate this proceeding with several other cases currently pending before the Commission, including, but not limited to, its Electric Base Rate Case. Additionally, on April 13, 2018, Duke Energy Ohio, along with certain intervenors, filed a Stipulation and Recommendation (Stipulation) with the PUCO resolving certain issues in this proceeding. The Stipulation establishes a regulatory model for the next seven years via the approval of the ESP and continues the current model for procuring supply for non-shopping customers, including recovery mechanisms. The Stipulation is subject to the review and approval of PUCO. An evidentiary hearing to review the Stipulation and other issues in the cases will be scheduled at a later date. Duke Energy Ohio cannot predict the outcome of this matter. Electric 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. 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 . On February 15, 2018, the procedural schedule was suspended to facilitate ongoing settlement discussions. On April 13, 2018, Duke Energy Ohio filed a Motion to consolidate this proceeding with several other cases currently pending before the Commission. On April 13, 2018, Duke Energy Ohio, along with certain intervenors, filed the Stipulation with the PUCO resolving certain issues in this proceeding. Major components of the Stipulation include a $19 million annual base distribution rate decrease with a return on equity of 9.84 percent based upon a capital structure of 50.75 percent equity and 49.25 percent debt. Upon approval of new rates, Duke Energy Ohio's rider for recovering its initial SmartGrid implementation ends as the costs will be recovered through base rates. The Stipulation also renews 14 existing riders, some of which were included in the Company's ESP, and two new riders including the Enhanced Service Reliability Rider to recover vegetation management costs not included in base rates, up to $10 million per year (operation and maintenance only) and the Power Forward Rider to recover costs incurred to enhance the customer experience and further transform the grid (operation and maintenance and capital). The Stipulation is subject to the review and approval of PUCO. An evidentiary hearing to review the Stipulation and other issues in the cases will be scheduled at a later date. Duke Energy Ohio has requested new rates go into effect June 1, 2018. In addition to the changes in revenue attributable to the Stipulation, Duke Energy Ohio’s capital-related riders, including the Distribution Capital Investments Rider, will begin to reflect the lower federal income tax rate associated with the Tax Act beginning with updates to be reflected in customers’ bills beginning April 1, 2018. At that time, all impacts of the lower federal income tax rate will be incorporated into customer rates, resulting in lower electric revenue of approximately $20 million on an annualized basis. All other implications of the Tax Act, including the quantification and timing of any refunds associated with excess accumulated deferred income taxes, will be deferred to PUCO’s open investigation, which is pending. Duke Energy Ohio 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. Duke Energy Ohio is seeking deferral authority for net costs incurred from January 1, 2018, 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. On April 13, 2018, Duke Energy Ohio filed a Motion to consolidate this proceeding with several other cases currently pending before the Commission. Also on April 13, 2018, Duke Energy Ohio, along with certain intervenors, filed a Stipulation with the PUCO resolving certain issues in this proceeding. The Stipulation, if approved, would activate Rider PSR for recovery of net costs incurred since January 1, 2018. The Stipulation is subject to the review and approval of PUCO. An evidentiary hearing to review the Stipulation and other issues in the cases will be scheduled at a later date. See Note 11 for additional discussion of Duke Energy Ohio's ownership interest in OVEC. Duke Energy Ohio cannot predict the outcome of this matter. 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. In December 2016, the PUCO granted the intervenors request for 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. 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. The PUCO approved the waiver request up to a total cost of $56 million . On November 21, 2017, the PUCO granted Duke Energy Ohio's and intervenor's applications for rehearing of the September 27, 2017, order. On January 10, 2018, the PUCO denied the Ohio Consumers' Counsel’s application for rehearing of the PUCO order granting Duke Energy Ohio's waiver request. Duke Energy Ohio cannot predict the outcome of this matter. 2014 Electric Security Plan In April 2015, the PUCO modified and approved Duke Energy Ohio's proposed ESP, with a three-year term and an effective date of June 1, 2015. The PUCO approved a competitive procurement process for SSO load, a distribution capital investment rider and a tracking mechanism for incremental distribution expenses caused by major storms. The PUCO also approved a placeholder tariff for a price stabilization rider, but denied Duke Energy Ohio's specific request to include Duke Energy Ohio's entitlement to generation from OVEC in the rider at this time; however, the order allows Duke Energy Ohio to submit additional information to request recovery in the future. On May 4, 2015, Duke Energy Ohio filed an application for rehearing requesting the PUCO to modify or amend certain aspects of the order. On May 28, 2015, the PUCO granted all applications for rehearing filed in the case for future consideration. On March 21, 2018, the PUCO issued an order denying the Company's issues on rehearing. On April 20, 2018, Duke Energy Ohio filed a second application for rehearing based upon the Commission’s March 21, 2018, Order. Natural Gas Pipeline Extension Duke Energy Ohio is proposing to install a new natural gas pipeline (the Central Corridor Project) in its Ohio service territory to increase system reliability and enable the retirement of older infrastructure. The pipeline is expected to cost approximately $112 million , excluding AFUDC. On January 20, 2017, Duke Energy Ohio filed an amended application with the Ohio Power Siting Board (OPSB) 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. In April 2018, Duke Energy Ohio filed a motion with OPSB to establish a procedural schedule and filed supplemental information supporting its application. If approved, construction of the pipeline extension is expected to be completed before the 2020/2021 winter season. Duke Energy Ohio cannot predict the outcome of this matter. 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. Subsequent to the filing, Duke Energy Kentucky adjusted the requested amount to $30.1 million , in part to reflect the benefits of the Tax Act, representing an approximate 9 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. An evidentiary hearing ended on March 8, 2018, and the KPSC issued an order on April 13, 2018. Major components of the Order include approval of an $8.4 million increase in base rates with a return on equity at 9.725 percent based upon a capital structure of 49 percent equity on a total allocable capitalization of approximately $650 million . The Order excludes $50 million of rate base being recovered with carrying costs elsewhere (e.g., through rider mechanisms). The Order approves the Environmental Surcharge Mechanism Rider to begin recovery in June 2018 of capital-related environmental costs, including costs related to ash and ash disposal and environmental operation and maintenance expenses formerly recovered in base rates, including expenses for environmental reagents and emission allowances. The incremental revenue from this rider will be approximately $13 million on an annualized basis. The order implements the impact of the Tax Act by lowering the income tax component of the revenue requirement, flowing back protected excess deferred income taxes (EDIT) under allowable normalization rules and unprotected EDIT over 10 years. The Order settles all matters related to the Tax Act. The Order denies requests to implement riders for certain transmission costs and distribution capital investments. Duke Energy Kentucky implemented new base rates on May 1, 2018. Duke Energy Indiana FERC Transmission Return on Equity Complaint Customer groups have filed with the FERC complaints against MISO and its transmission-owning members, including Duke Energy Indiana, alleging, among other things, that the current base rate of return on equity earned by MISO transmission owners of 12.38 percent is unjust and unreasonable. The complaints claim, among other things, that the current base rate of return on equity earned by MISO transmission owners should be reduced to 8.67 percent . On January 5, 2015, the FERC issued an order accepting the MISO transmission owners' adder of 0.50 percent to the base rate of return on equity based on participation in an RTO subject to it being applied to a return on equity that is shown to be just and reasonable in the pending return on equity complaints. On December 22, 2015, the presiding FERC ALJ in the first complaint issued an Initial Decision in which the base rate of return on equity was set at 10.32 percent . On September 28, 2016, the Initial Decision in the first complaint was affirmed by FERC, but is subject to rehearing requests. On June 30, 2016, the presiding FERC ALJ in the second complaint issued an Initial Decision setting the base rate of return on equity at 9.70 percent . The Initial Decision in the second complaint is pending FERC review. On April 14, 2017, the U.S. Court of Appeals for the District of Columbia Circuit, in Emera Maine v. FERC , reversed and remanded certain aspects of the methodology employed by FERC to establish rates of return on equity. This decision may affect the outcome of the complaints against Duke Energy Indiana. Duke Energy Indiana currently believes these matters will not have a material impact on its results of operations, cash flows and financial position. Benton County Wind Farm Dispute On December 16, 2013, Benton County Wind Farm LLC (BCWF) filed a lawsuit against Duke Energy Indiana seeking damages for past generation losses alleging Duke Energy Indiana violated its obligations under a 2006 PPA by refusing to offer electricity to the market at negative prices. Damage claims continue to increase during times that BCWF is not dispatched. Under 2013 revised MISO market rules, Duke Energy Indiana is required to make a price offer to MISO for the powe

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments And Contingencies	COMMITMENTS AND CONTINGENCIES ENVIRONMENTAL The Duke Energy Registrants are subject to federal, state and local regulations regarding air and water quality, hazardous and solid waste disposal and other environmental matters. These regulations can be changed from time to time, imposing new obligations on the Duke Energy Registrants. The following environmental matters impact all of the Duke Energy Registrants. Remediation Activities In addition to asset retirement obligations (ARO) recorded as a result of various environmental regulations, the Duke Energy Registrants are responsible for environmental remediation at various sites. These include certain properties that are part of ongoing operations and sites formerly owned or used by Duke Energy entities. These sites are in various stages of investigation, remediation and monitoring. Managed in conjunction with relevant federal, state and local agencies, remediation activities vary based upon site conditions and location, remediation requirements, complexity and sharing of responsibility. If remediation activities involve joint and several liability provisions, strict liability, or cost recovery or contribution actions, the Duke Energy Registrants could potentially be held responsible for environmental impacts caused by other potentially responsible parties and may also benefit from insurance policies or contractual indemnities that cover some or all cleanup costs. Liabilities are recorded when losses become probable and are reasonably estimable. The total costs that may be incurred cannot be estimated because the extent of environmental impact, allocation among potentially responsible parties, remediation alternatives and/or regulatory decisions have not yet been determined at all sites. Additional costs associated with remediation activities are likely to be incurred in the future and could be significant. Costs are typically expensed as Operation, maintenance and other on the Condensed Consolidated Statements of Operations unless regulatory recovery of the costs is deemed probable. The following tables contain information regarding reserves for probable and estimable costs related to the various environmental sites. These reserves are recorded in Accounts Payable within Current Liabilities and Other within Other Noncurrent Liabilities on the Condensed Consolidated Balance Sheets. Three Months Ended March 31, 2018 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Balance at beginning of period $ 81 $ 10 $ 15 $ 3 $ 12 $ 47 $ 5 $ 2 Provisions/adjustments 4 1 3 1 1 — 1 — Cash reductions (5 ) — (2 ) (1 ) (1 ) (3 ) — — Balance at end of period $ 80 $ 11 $ 16 $ 3 $ 12 $ 44 $ 6 $ 2 Three Months Ended March 31, 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 6 1 — — 1 4 (1 ) 1 Cash reductions (6 ) — (1 ) — (1 ) (4 ) — — Balance at end of period $ 98 $ 11 $ 17 $ 3 $ 14 $ 59 $ 9 $ 2 Additional losses in excess of recorded reserves that could be incurred for the stages of investigation, remediation and monitoring for environmental sites that have been evaluated at this time are not material except as presented in the table below. (in millions) Duke Energy $ 57 Duke Energy Carolinas 19 Duke Energy Ohio 30 Piedmont 2 LITIGATION Duke Energy Carolinas and Duke Energy Progress Coal Ash Insurance Coverage Litigation In March 2017, Duke Energy Carolinas and Duke Energy Progress filed a civil action in North Carolina Superior Court against various insurance providers. The lawsuit seeks payment for coal ash-related liabilities covered by third-party liability insurance policies. The insurance policies were issued between 1971 and 1986 and provide third-party liability insurance for property damage. The civil action seeks damages for breach of contract and indemnification for costs arising from the Coal Ash Act and the EPA CCR rule at 15 coal-fired plants in North Carolina and South Carolina. The parties are engaged in discovery. Duke Energy Carolinas and Duke Energy Progress cannot predict the outcome of this matter. NCDEQ State Enforcement Actions In the first quarter of 2013, the Southern Environmental Law Center (SELC) sent notices of intent to sue Duke Energy Carolinas and Duke Energy Progress related to alleged Clean Water Act (CWA) violations from coal ash basins at two of their coal-fired power plants in North Carolina. The NCDEQ filed enforcement actions against Duke Energy Carolinas and Duke Energy Progress alleging violations of water discharge permits and North Carolina groundwater standards. The cases have been consolidated and are being heard before a single judge in the North Carolina Superior Court. On August 16, 2013, the NCDEQ filed an enforcement action against Duke Energy Carolinas and Duke Energy Progress related to their remaining plants in North Carolina, alleging violations of the CWA and violations of the North Carolina groundwater standards. Both of these cases have been assigned to the judge handling the enforcement actions discussed above. SELC is representing several environmental groups who have been permitted to intervene in these cases. The court issued orders in 2016 granting Motions for Partial Summary Judgment for seven of the 14 North Carolina plants named in the enforcement actions. On February 13, 2017, the court issued an order denying motions for partial summary judgment brought by both the environmental groups and Duke Energy Carolinas and Duke Energy Progress for the remaining seven plants. On March 15, 2017, Duke Energy Carolinas and Duke Energy Progress filed a Notice of Appeal to challenge the trial court’s order. The parties were unable to reach an agreement at mediation in April 2017. The parties submitted briefs to the court on remaining issues to be tried and a ruling is pending. On August 22, 2017, Duke Energy Carolinas and Duke Energy Progress filed a Petition for Discretionary Review, requesting the North Carolina Supreme Court to accept the appeal. On August 24, 2017, SELC filed a motion to dismiss the appeal. Duke Energy Carolinas' and Duke Energy Progress’ opening appellate briefs were filed on October 12, 2017, and briefing is now complete. Argument was held on February 8, 2018. It is not possible to predict any liability or estimate any damages Duke Energy Carolinas or Duke Energy Progress might incur in connection with these matters. Federal Citizens Suits On June 13, 2016, the Roanoke River Basin Association (RRBA) filed a federal citizen suit in the Middle District of North Carolina alleging unpermitted discharges to surface water and groundwater violations at the Mayo Plant. On August 19, 2016, Duke Energy Progress filed a Motion to Dismiss. On April 26, 2017, the court entered an order dismissing four of the claims in the federal citizen suit. Two claims relating to alleged violations of National Pollutant Discharge Elimination System (NPDES) permit provisions survived the motion to dismiss, and Duke Energy Progress filed its response on May 10, 2017. Duke Energy Progress and RRBA each filed motions for summary judgment on March 23, 2018. On May 16, 2017, RRBA filed a federal citizen suit in the U.S. District Court for the Middle District of North Carolina, which asserts two claims relating to alleged violations of NPDES permit provisions at the Roxboro plant and one claim relating to the use of nearby water bodies. Duke Energy Progress and RRBA each filed motions for summary judgment on April 17, 2018. On May 8, 2018, on motion from Duke Energy Progress, the Court ordered trial in both of the above matters to be consolidated and has set a trial date for December 3, 2018. On June 20, 2017, RRBA filed a federal citizen suit in the U.S. District Court for the Middle District of North Carolina challenging the closure plans at the Mayo Plant under the EPA CCR Rule. Duke Energy Progress filed a motion to dismiss, which was granted by the court on March 30, 2018. RRBA had until April 30, 2018 to file an appeal to the Fourth Circuit but did not do so. On August 2, 2017, RRBA filed a federal citizen suit in the U.S. District Court for the Middle District of North Carolina challenging the closure plans at the Roxboro Plant under the EPA CCR Rule. Duke Energy Progress filed a motion to dismiss on October 2, 2017. On December 6, 2017, various parties filed a federal citizen suit in the U.S. District Court for the Middle District of North Carolina for alleged violations at Duke Energy Carolinas' Belews Creek Steam Station (Belews Creek) under the CWA. Duke Energy Carolinas filed a motion to dismiss on February 5, 2018. It is not possible to predict whether Duke Energy Carolinas or Duke Energy Progress will incur any liability or to estimate the damages, if any, they might incur in connection with these matters. Groundwater Contamination Claims Beginning in May 2015, a number of residents living in the vicinity of the North Carolina facilities with ash basins received letters from the NCDEQ advising them not to drink water from the private wells on their land tested by the NCDEQ as the samples were found to have certain substances at levels higher than the criteria set by the North Carolina Department of Health and Human Services (DHHS). Results of Comprehensive Site Assessments testing performed by Duke Energy under the Coal Ash Act have been consistent with historical data provided to state regulators over many years. The DHHS and NCDEQ sent follow-up letters on October 15, 2015, to residents near coal ash basins who had their wells tested, stating that private well samplings at a considerable distance from coal ash basins, as well as some municipal water supplies, contain similar levels of vanadium and hexavalent chromium, which led investigators to believe these constituents are naturally occurring. In March 2016, DHHS rescinded the advisories. Duke Energy Carolinas and Duke Energy Progress have received formal demand letters from residents near Duke Energy Carolinas' and Duke Energy Progress' coal ash basins. The residents claim damages for nuisance and diminution in property value, among other things. The parties held three days of mediation discussions that ended at an impasse. On January 6, 2017, Duke Energy Carolinas and Duke Energy Progress received the plaintiffs' notice of their intent to file suits should the matter not settle. The NCDEQ preliminarily approved Duke Energy’s permanent water solution plans on January 13, 2017, and as a result shortly thereafter, Duke Energy issued a press release, providing additional details regarding the homeowner compensation package. This package consists of three components: (i) a $5,000 goodwill payment to each eligible well owner to support the transition to a new water supply, (ii) where a public water supply is available and selected by the eligible well owner, a stipend to cover 25 years of water bills and (iii) the Property Value Protection Plan. The Property Value Protection Plan is a program offered by Duke Energy designed to guarantee eligible plant neighbors the fair market value of their residential property should they decide to sell their property during the time that the plan is offered. Duke Energy Carolinas and Duke Energy Progress have recognized reserves of $16 million and $3 million , respectively. On August 23, 2017, a class-action suit was filed in Wake County Superior Court, North Carolina, against Duke Energy Carolinas and Duke Energy Progress on behalf of certain property owners living near coal ash impoundments at Allen, Asheville, Belews Creek, Buck, Cliffside, Lee, Marshall, Mayo and Roxboro. The class is defined as those who are “well-eligible” under the Coal Ash Act or those to whom Duke Energy has promised a permanent replacement water supply and seeks declaratory and injunctive relief, along with compensatory damages. Plaintiffs allege that Duke Energy’s improper maintenance of coal ash impoundments caused harm, particularly through groundwater contamination. Despite NCDEQ’s preliminary approval, Plaintiffs contend that Duke Energy’s proposed permanent water solutions plan fails to comply with the Coal Ash Act. On September 28, 2017, Duke Energy Carolinas and Duke Energy Progress filed a Motion to Dismiss and Motion to Strike the class designation. The parties entered into a Settlement Agreement on January 24, 2018, which resulted in the dismissal of the underlying class action on January 25, 2018. On September 14, 2017, a complaint was filed against Duke Energy Progress in New Hanover County Superior Court by a group of homeowners residing approximately 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. On March 6, 2018, Plaintiffs' counsel voluntarily dismissed the action without prejudice. It is not possible to estimate the maximum exposure of loss, if any, that may occur in connection with future claims that might be made by these residents. Asbestos-related Injuries and Damages Claims Duke Energy Carolinas has experienced numerous claims for indemnification and medical cost reimbursement related to asbestos exposure. These claims relate to damages for bodily injuries alleged to have arisen from exposure to or use of asbestos in connection with construction and maintenance activities conducted on its electric generation plants prior to 1985. As of March 31, 2018 , there were 143 asserted claims for non-malignant cases with cumulative relief sought of up to $37 million , and 58 asserted claims for malignant cases with cumulative relief sought of up to $19 million . Based on Duke Energy Carolinas’ experience, it is expected that the ultimate resolution of most of these claims likely will be less than the amount claimed. Duke Energy Carolinas has recognized asbestos-related reserves of $487 million at March 31, 2018 , and $489 million at December 31, 2017 . These reserves are classified in Other within Other Noncurrent Liabilities and Other within Current Liabilities on the Condensed Consolidated Balance Sheets. These reserves are based upon the minimum amount of the range of loss for current and future asbestos claims through 2037, are recorded on an undiscounted basis and incorporate anticipated inflation. In light of the uncertainties inherent in a longer-term forecast, management does not believe they can reasonably estimate the indemnity and medical costs that might be incurred after 2037 related to such potential claims. It is possible Duke Energy Carolinas may incur asbestos liabilities in excess of the recorded reserves. Duke Energy Carolinas has third-party insurance to cover certain losses related to asbestos-related injuries and damages above an aggregate self-insured retention. Duke Energy Carolinas’ cumulative payments began to exceed the self-insurance retention in 2008. Future payments up to the policy limit will be reimbursed by the third-party insurance carrier. The insurance policy limit for potential future insurance recoveries indemnification and medical cost claim payments is $797 million in excess of the self-insured retention. Receivables for insurance recoveries were $585 million at March 31, 2018 , and December 31, 2017 . These amounts are classified in Other within Other Noncurrent Assets and Receivables within Current Assets on the Condensed Consolidated Balance Sheets. Duke Energy Carolinas is not aware of any uncertainties regarding the legal sufficiency of insurance claims. Duke Energy Carolinas believes the insurance recovery asset is probable of recovery as the insurance carrier continues to have a strong financial strength rating. Duke Energy Progress and Duke Energy Florida Spent Nuclear Fuel Matters On October 16, 2014, Duke Energy Progress and Duke Energy Florida sued the U.S. in the U.S. Court of Federal Claims. The lawsuit claimed the Department of Energy breached a contract in failing to accept spent nuclear fuel under the Nuclear Waste Policy Act of 1982 and asserted damages for the cost of on-site storage. Duke Energy Progress and Duke Energy Florida asserted damages for the period January 1, 2011, through December 31, 2013, of $48 million and $25 million , respectively. On November 17, 2017, the Court awarded Duke Energy Progress and Duke Energy Florida $48 million and $21 million , respectively, subject to appeal. No appeals were filed and Duke Energy Progress and Duke Energy Florida recognized the recoveries in the first quarter of 2018. Claims for all periods through 2013 have been resolved. Additional claims will be filed in 2018. Duke Energy Progress Gypsum Supply Agreement Matter On June 30, 2017, CertainTeed Gypsum NC, Inc. (CertainTeed) filed a declaratory judgment action against Duke Energy Progress in the North Carolina Business Court relating to a gypsum supply agreement. In its complaint, CertainTeed sought an order from the court declaring that the minimum amount of gypsum Duke Energy Progress must provide to CertainTeed under the supply agreement is 50,000 tons per month through 2029. On January 29, 2018, CertainTeed filed a request to amend its Complaint and seek a preliminary injunction requiring Duke Energy Progress to provide 50,000 tons of gypsum per month through the trial date. In advance of the hearing on the Motion for Preliminary Injunction, the parties reached an agreement under which Duke Energy Progress would deliver 50,000 tons of gypsum per month through June 2018. If the Court determines that Duke Energy Progress was not obligated to provide that amount per month, CertainTeed will reimburse Duke Energy Progress. Discovery is currently underway and trial is set for July 2018. If Duke Energy Progress does not prevail at trial, Duke Energy Progress will either have to purchase additional gypsum on the open market to fulfill its contractual obligation through 2029 or pay some amount of liquidated damages. Duke Energy Progress cannot predict the outcome of this matter. Duke Energy Florida Class Action Lawsuit On February 22, 2016, a lawsuit was filed in the U.S. District Court for the Southern District of Florida on behalf of a putative class of Duke Energy Florida and FP&L’s customers in Florida. The suit alleges the State of Florida’s nuclear power plant cost recovery statutes (NCRS) are unconstitutional and pre-empted by federal law. Plaintiffs claim they are entitled to repayment of all money paid by customers of Duke Energy Florida and FP&L as a result of the NCRS, as well as an injunction against any future charges under those statutes. The constitutionality of the NCRS has been challenged unsuccessfully in a number of prior cases on alternative grounds. Duke Energy Florida and FP&L filed motions to dismiss the complaint on May 5, 2016. On September 21, 2016, the Court granted the motions to dismiss with prejudice. Plaintiffs filed a motion for reconsideration, which was denied. On January 4, 2017, plaintiffs filed a notice of appeal to the Eleventh Circuit U.S. Court of Appeals. 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 an EPC contract. Duke Energy Florida recognized an exit obligation as a result of the termination of the EPC. On March 31, 2014, Westinghouse filed a separate lawsuit against Duke Energy Florida in U.S. District Court for the Western District of Pennsylvania alleging damages under the same EPC contract in excess of $510 million for engineering and design work, costs to end supplier contracts and an alleged termination fee. On June 9, 2014, the judge in the North Carolina case ruled that the litigation would proceed in the Western District of North Carolina. On July 11, 2016, Duke Energy Florida and Westinghouse filed separate Motions for Summary Judgment. On September 29, 2016, the court issued its ruling, granting Westinghouse a $30 million termination fee claim and dismissing Duke Energy Florida's $54 million refund claim. Westinghouse's claim for termination costs continued to trial. Following a trial on the matter, the court issued an order in December 2016 denying Westinghouse’s claim for termination costs and reaffirming its earlier ruling in favor of Westinghouse on the $30 million termination fee. Judgment was entered against Duke Energy Florida in the amount of approximately $34 million , which includes prejudgment interest. Westinghouse 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. On March 29, 2017, Westinghouse filed Chapter 11 bankruptcy in the Southern District of New York, which automatically stayed the appeal. On May 23, 2017, the bankruptcy court entered an order lifting the stay with respect to the appeal. Briefing of the appeal concluded on October 20, 2017. Westinghouse and Duke Energy Florida executed a settlement agreement resolving this matter on April 5, 2018, which has been filed with the bankruptcy court for approval. The settlement provides that the appeal will be dismissed and Duke Energy Florida will pay the judgment amount of approximately $34 million . This reserve is classified in Other within Other Noncurrent Liabilities on the Condensed Consolidated Balance Sheet. In light of the settlement, the Fourth Circuit Court agreed to stay the appeal pending bankruptcy court approval of the settlement. Duke Energy cannot predict the ultimate outcome of this appeal or the bankruptcy court's approval of the pending settlement. 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, which affirmed the trial court's ruling on April 10, 2018. 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 related to the termination of an EPC contract discussed above. Reserves are classified on the Condensed Consolidated Balance Sheets in Other within Other Noncurrent Liabilities and Accounts payable and Other within Current Liabilities. The reasonably possible range of loss in excess of recorded reserves is not material, other than as described above. (in millions) March 31, 2018 December 31, 2017 Reserves for Legal Matters Duke Energy $ 74 $ 88 Duke Energy Carolinas 20 30 Progress Energy 51 55 Duke Energy Progress 10 13 Duke Energy Florida 24 24 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	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Debt And Credit Facilities	DEBT AND CREDIT FACILITIES SUMMARY OF SIGNIFICANT DEBT ISSUANCES The following table summarizes significant debt issuances (in millions). Three Months Ended March 31, 2018 Duke Duke Maturity Interest Duke Energy Energy Issuance Date Date Rate Energy (Parent) Carolinas Unsecured Debt March 2018 (a) April 2025 3.950 % $ 250 $ 250 $ — First Mortgage Bonds March 2018 (b) March 2023 3.050 % 500 — 500 March 2018 (b) March 2048 3.950 % 500 — 500 Total issuances $ 1,250 $ 250 $ 1,000 (a) Debt issued to pay down short-term debt. (b) Debt issued to repay at maturity a $ 300 million first mortgage bond due April 2018, pay down intercompany short-term debt and for general corporate purposes. 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 March 31, 2018 Unsecured Debt Duke Energy (Parent) June 2018 6.250 % $ 250 Duke Energy (Parent) June 2018 2.100 % 500 Piedmont December 2018 2.821 % (b) 250 Progress Energy March 2019 7.050 % 450 First Mortgage Bonds Duke Energy Carolinas April 2018 5.100 % 300 Duke Energy Florida June 2018 5.650 % 500 Duke Energy Carolinas November 2018 7.000 % 500 Duke Energy Progress January 2019 5.300 % 600 Other (a) 601 Current maturities of long-term debt $ 3,951 (a) Includes capital lease obligations, amortizing debt and small bullet maturities. (b) Debt issuance has a floating interest rate. AVAILABLE CREDIT FACILITIES Master Credit Facility In January 2018, Duke Energy extended the termination date of substantially all of its existing $8 billion Master Credit Facility capacity from March 16, 2022 to March 16, 2023. In May 2018, Duke Energy completed the extension process with 100 percent of all commitments to the Master Credit Facility extending to March 16, 2023 . The Duke Energy Registrants, excluding Progress Energy (Parent), have borrowing capacity under the Master Credit Facility up to a specified sublimit for each borrower. Duke Energy has the unilateral ability at any time to increase or decrease the borrowing sublimits of each borrower, subject to a maximum sublimit for each borrower. The amount available under the Master Credit Facility has been reduced to backstop issuances of commercial paper, certain letters of credit and variable-rate demand tax-exempt bonds that may be put to the Duke Energy Registrants at the option of the holder. Duke Energy Carolinas and Duke Energy Progress are also required to each maintain $250 million of available capacity under the Master Credit Facility as security to meet obligations under plea agreements reached with the U.S. Department of Justice in 2015 related to violations at North Carolina facilities with ash basins. The table below includes the current borrowing sublimits and available capacity under the Master Credit Facility. March 31, 2018 Duke Duke Duke Duke Duke Duke Duke Energy Energy Energy Energy Energy Energy (in millions) Energy (Parent) Carolinas Progress Florida Ohio Indiana Piedmont Facility size (a) $ 8,000 $ 2,650 $ 1,550 $ 1,250 $ 800 $ 450 $ 600 $ 700 Reduction to backstop issuances Commercial paper (b) (2,602 ) (1,281 ) (340 ) (464 ) — (140 ) (282 ) (95 ) Outstanding letters of credit (59 ) (50 ) (4 ) (2 ) (1 ) — — (2 ) Tax-exempt bonds (81 ) — — — — — (81 ) — Coal ash set-aside (500 ) — (250 ) (250 ) — — — — Available capacity under the Master Credit Facility $ 4,758 $ 1,319 $ 956 $ 534 $ 799 $ 310 $ 237 $ 603 (a) Represents the sublimit of each borrower. (b) Duke Energy issued $625 million of commercial paper and loaned the proceeds through the money pool to Duke Energy Carolinas, Duke Energy Progress, Duke Energy Ohio and Duke Energy Indiana. The balances are classified as Long-Term Debt Payable to Affiliated Companies on the Condensed Consolidated Balance Sheets. Three-Year Revolving Credit Facility Duke Energy (Parent) has a $1.0 billion revolving credit facility (the Three Year Revolver) through June 2020. As of March 31, 2018 , $500 million has been drawn under the Three Year Revolver. This balance is classified as Long-Term Debt on Duke Energy's Condensed Consolidated Balance Sheets. Any undrawn commitments can be drawn, and borrowings can be prepaid, at any time throughout the term of the facility. The terms and conditions of the Three Year Revolver are generally consistent with those governing Duke Energy's Master Credit Facility.

Goodwill

Goodwill	3 Months Ended
	Mar. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	GOODWILL Duke Energy The following table presents the goodwill by reportable operating segment included on Duke Energy's Condensed Consolidated Balance Sheets at March 31, 2018 , and December 31, 2017 . Electric Utilities Gas Utilities Commercial (in millions) and Infrastructure and Infrastructure Renewables Total Goodwill balance $ 17,379 $ 1,924 $ 122 $ 19,425 Accumulated impairment charges — — (29 ) (29 ) Goodwill, adjusted for accumulated impairment charges $ 17,379 $ 1,924 $ 93 $ 19,396 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 March 31, 2018 , and December 31, 2017 . Progress Energy Progress Energy's Goodwill is included in the Electric Utilities and Infrastructure operating segment and there are no accumulated impairment charges. Piedmont Piedmont's Goodwill is included in the Gas Utilities and Infrastructure operating segment and there are no accumulated impairment charges.

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2018
Related Party Transactions [Abstract]
Related Party Transactions	RELATED PARTY TRANSACTIONS The Subsidiary Registrants engage in related party transactions in accordance with applicable state and federal commission regulations. Refer to the Condensed Consolidated Balance Sheets of the Subsidiary Registrants for balances due to or due from related parties. Material amounts related to transactions with related parties included on the Condensed Consolidated Statements of Operations and Comprehensive Income are presented in the following table. Three Months Ended March 31, (in millions) 2018 2017 Duke Energy Carolinas Corporate governance and shared service expenses (a) $ 220 $ 221 Indemnification coverages (b) 6 6 JDA revenue (c) 34 16 JDA expense (c) 54 31 Intercompany natural gas purchases (d) 4 1 Progress Energy Corporate governance and shared service expenses (a) $ 191 $ 170 Indemnification coverages (b) 8 10 JDA revenue (c) 54 31 JDA expense (c) 34 16 Intercompany natural gas purchases (d) 19 19 Duke Energy Progress Corporate governance and shared service expenses (a) $ 118 $ 100 Indemnification coverages (b) 3 4 JDA revenue (c) 54 31 JDA expense (c) 34 16 Intercompany natural gas purchases (d) 19 19 Duke Energy Florida Corporate governance and shared service expenses (a) $ 73 $ 70 Indemnification coverages (b) 5 6 Duke Energy Ohio Corporate governance and shared service expenses (a) $ 89 $ 92 Indemnification coverages (b) 1 1 Duke Energy Indiana Corporate governance and shared service expenses (a) $ 101 $ 95 Indemnification coverages (b) 2 2 Piedmont Corporate governance and shared service expenses (a) $ 36 $ 5 Indemnification coverages (b) 1 1 Intercompany natural gas sales (d) 23 20 (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. 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/A for the year ended December 31, 2017 , for more information regarding the money pool. These transactions of the Subsidiary Registrants were not material for the three months ended March 31, 2018 , and 2017 . As discussed in Note 11 , certain trade receivables have been sold by Duke Energy Ohio and Duke Energy Indiana to Cinergy Receivables Company LLC (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 months ended March 31, 2018 , and 2017 , which are included in Cost of natural gas on Piedmont's Condensed Consolidated Statements of Operations and Comprehensive Income. Three Months Ended March 31, (in millions) Type of expense 2018 2017 Cardinal Transportation Costs $ 2 $ 2 Pine Needle Natural Gas Storage Costs 2 2 Hardy Storage Natural Gas Storage Costs 2 2 Total $ 6 $ 6 Piedmont had accounts payable to its equity method investments of $2 million at March 31, 2018 , and December 31, 2017 , related to these transactions. These amounts are included in Accounts payable on the Condensed Consolidated Balance Sheets. Intercompany Income Taxes Duke Energy and the Subsidiary Registrants file a consolidated federal income tax return and other state and jurisdictional returns. The Subsidiary Registrants have a tax sharing agreement with Duke Energy for the allocation of consolidated tax liabilities and benefits. Income taxes recorded represent amounts the Subsidiary Registrants would incur as separate C-Corporations. The following table includes the balance of intercompany income tax receivables and payables for the Subsidiary Registrants. Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Carolinas Energy Progress Florida Ohio Indiana Piedmont March 31, 2018 Intercompany income tax receivable $ — $ 183 $ 13 $ 9 $ — $ — $ — Intercompany income tax payable 9 — — — 3 18 43 December 31, 2017 Intercompany income tax receivable $ — $ 168 $ — $ 44 $ 22 $ — $ 7 Intercompany income tax payable 44 — 21 — — 35 —

Derivatives and Hedging

Derivatives and Hedging	3 Months Ended
	Mar. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives and Hedging	DERIVATIVES AND HEDGING The Duke Energy Registrants use commodity and interest rate contracts to manage commodity price risk and interest rate risk. The primary use of commodity derivatives is to hedge the generation portfolio against changes in the prices of electricity and natural gas. Piedmont enters into natural gas supply contracts to provide diversification, reliability and natural gas cost benefits to its customers. Interest rate swaps are used to manage interest rate risk associated with borrowings. All derivative instruments not identified as NPNS are recorded at fair value as assets or liabilities on the Condensed Consolidated Balance Sheets. Cash collateral related to derivative instruments executed under master netting arrangements is offset against the collateralized derivatives on the Condensed Consolidated Balance Sheets. The cash impacts of settled derivatives are recorded as operating activities on the Condensed Consolidated Statements of Cash Flows. INTEREST RATE RISK The Duke Energy Registrants are exposed to changes in interest rates as a result of their issuance or anticipated issuance of variable-rate and fixed-rate debt and commercial paper. Interest rate risk is managed by limiting variable-rate exposures to a percentage of total debt and by monitoring changes in interest rates. To manage risk associated with changes in interest rates, the Duke Energy Registrants may enter into interest rate swaps, U.S. Treasury lock agreements and other financial contracts. In anticipation of certain fixed-rate debt issuances, a series of forward-starting interest rate swaps or Treasury locks may be executed to lock in components of current market interest rates. These instruments are later terminated prior to or upon the issuance of the corresponding debt. Cash Flow Hedges For a derivative designated as hedging the exposure to variable cash flows of a future transaction, referred to as a cash flow hedge, the effective portion of the derivative's gain or loss is initially reported as a component of other comprehensive income and subsequently reclassified into earnings once the future transaction impacts earnings. Amounts for interest rate contracts are reclassified to earnings as interest expense over the term of the related debt. Gains and losses reclassified out of AOCI for the three months ended March 31, 2018 and 2017 were not material. Duke Energy's interest rate derivatives designated as hedges include interest rate swaps used to hedge existing debt within the Commercial Renewables business. Undesignated Contracts Undesignated contracts 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. The following table shows notional amounts of outstanding derivatives related to interest rate risk. March 31, 2018 Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Cash flow hedges (a) $ 660 $ — $ — $ — $ — $ — Undesignated contracts 527 — 500 250 250 27 Total notional amount $ 1,187 $ — $ 500 $ 250 $ 250 $ 27 December 31, 2017 Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Cash flow hedges (a) $ 660 $ — $ — $ — $ — $ — Undesignated contracts 927 400 500 250 250 27 Total notional amount $ 1,587 $ 400 $ 500 $ 250 $ 250 $ 27 (a) Duke Energy includes amounts related to consolidated VIEs of $660 million as of March 31, 2018 , and December 31, 2017 . COMMODITY PRICE RISK The Duke Energy Registrants are exposed to the impact of changes in the prices of electricity purchased and sold in bulk power markets and coal and natural gas purchases, including Piedmont's natural gas supply contracts. Exposure to commodity price risk is influenced by a number of factors including the term of contracts, the liquidity of markets and delivery locations. For the Subsidiary Registrants, bulk power electricity and coal and natural gas purchases flow through fuel adjustment clauses, formula-based contracts or other cost-sharing mechanisms. Differences between the costs included in rates and the incurred costs, including undesignated derivative contracts, are largely deferred as regulatory assets or regulatory liabilities. Piedmont policies allow for the use of financial instruments to hedge commodity price risks. The strategy and objective of these hedging programs are to use the financial instruments to reduce natural gas costs volatility for customers. Volumes The tables below include volumes of outstanding commodity derivatives. Amounts disclosed represent the absolute value of notional volumes of commodity contracts excluding NPNS. The Duke Energy Registrants have netted contractual amounts where offsetting purchase and sale contracts exist with identical delivery locations and times of delivery. Where all commodity positions are perfectly offset, no quantities are shown. March 31, 2018 Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy Carolinas Energy Progress Florida Indiana Piedmont Electricity (gigawatt-hours) 16 — — — — 16 — Natural gas (millions of dekatherms) 765 110 179 149 30 2 474 December 31, 2017 Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy Carolinas Energy Progress Florida Indiana Piedmont Electricity (gigawatt-hours) 34 — — — — 34 — Natural gas (millions of dekatherms) 770 105 183 133 50 2 480 LOCATION AND FAIR VALUE OF DERIVATIVE ASSETS AND LIABILITIES RECOGNIZED ON THE CONDENSED CONSOLIDATED BALANCE SHEETS The following tables show the fair value and balance sheet location of derivative instruments. Although derivatives subject to master netting arrangements are netted on the Condensed Consolidated Balance Sheets, the fair values presented below are shown gross and cash collateral on the derivatives has not been netted against the fair values shown. Derivative Assets March 31, 2018 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Commodity Contracts Not Designated as Hedging Instruments Current $ 14 $ 2 $ 3 $ 2 $ 1 $ 1 $ 7 $ 1 Noncurrent 1 — — — — — — — Total Derivative Assets – Commodity Contracts $ 15 $ 2 $ 3 $ 2 $ 1 $ 1 $ 7 $ 1 Interest Rate Contracts Designated as Hedging Instruments Current $ 1 $ — $ — $ — $ — $ — $ — $ — Noncurrent 21 — — — — — — — Total Derivative Assets – Interest Rate Contracts $ 22 $ — $ — $ — $ — $ — $ — $ — Total Derivative Assets $ 37 $ 2 $ 3 $ 2 $ 1 $ 1 $ 7 $ 1 Derivative Liabilities March 31, 2018 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Commodity Contracts Not Designated as Hedging Instruments Current $ 26 $ 5 $ 8 $ 6 $ 3 $ — $ — $ 13 Noncurrent 140 6 15 6 — — — 119 Total Derivative Liabilities – Commodity Contracts $ 166 $ 11 $ 23 $ 12 $ 3 $ — $ — $ 132 Interest Rate Contracts Designated as Hedging Instruments Current $ 4 $ — $ — $ — $ — $ — $ — $ — Noncurrent 3 — — — — — — — Not Designated as Hedging Instruments Current 3 — 3 2 1 — — — Noncurrent 14 — 11 7 3 4 — — Total Derivative Liabilities – Interest Rate Contracts $ 24 $ — $ 14 $ 9 $ 4 $ 4 $ — $ — Total Derivative Liabilities $ 190 $ 11 $ 37 $ 21 $ 7 $ 4 $ — $ 132 Derivative Assets December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Commodity Contracts Not Designated as Hedging Instruments Current $ 34 $ 2 $ 2 $ 1 $ 1 $ 1 $ 27 $ 2 Noncurrent 1 — 1 1 — — — — Total Derivative Assets – Commodity Contracts $ 35 $ 2 $ 3 $ 2 $ 1 $ 1 $ 27 $ 2 Interest Rate Contracts Designated as Hedging Instruments Current $ 1 $ — $ — $ — $ — $ — $ — $ — Noncurrent 15 — — — — — — — Total Derivative Assets – Interest Rate Contracts $ 16 $ — $ — $ — $ — $ — $ — $ — Total Derivative Assets $ 51 $ 2 $ 3 $ 2 $ 1 $ 1 $ 27 $ 2 Derivative Liabilities December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Commodity Contracts Not Designated as Hedging Instruments Current $ 36 $ 6 $ 18 $ 8 $ 10 $ — $ — $ 11 Noncurrent 146 4 10 4 — — — 131 Total Derivative Liabilities – Commodity Contracts $ 182 $ 10 $ 28 $ 12 $ 10 $ — $ — $ 142 Interest Rate Contracts Designated as Hedging Instruments Current $ 29 $ 25 $ — $ — $ — $ — $ — $ — Noncurrent 6 — — — — — — — Not Designated as Hedging Instruments Current 1 — 1 — — 1 — — Noncurrent 12 — 7 6 2 4 — — Total Derivative Liabilities – Interest Rate Contracts $ 48 $ 25 $ 8 $ 6 $ 2 $ 5 $ — $ — Total Derivative Liabilities $ 230 $ 35 $ 36 $ 18 $ 12 $ 5 $ — $ 142 OFFSETTING ASSETS AND LIABILITIES The following tables present the line items on the Condensed Consolidated Balance Sheets where derivatives are reported. Substantially all of Duke Energy's outstanding derivative contracts are subject to enforceable master netting arrangements. The gross amounts offset in the tables below show the effect of these netting arrangements on financial position, and include collateral posted to offset the net position. The amounts shown are calculated by counterparty. Accounts receivable or accounts payable may also be available to offset exposures in the event of bankruptcy. These amounts are not included in the tables below. Derivative Assets March 31, 2018 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Current Gross amounts recognized $ 15 $ 2 $ 3 $ 2 $ 1 $ 1 $ 7 $ 1 Gross amounts offset (2 ) (1 ) (1 ) (1 ) — — — — Net amounts presented in Current Assets: Other $ 13 $ 1 $ 2 $ 1 $ 1 $ 1 $ 7 $ 1 Noncurrent Gross amounts recognized $ 22 $ — $ — $ — $ — $ — $ — $ — Gross amounts offset — — — — — — — — Net amounts presented in Other Noncurrent Assets: Other $ 22 $ — $ — $ — $ — $ — $ — $ — Derivative Liabilities March 31, 2018 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Current Gross amounts recognized $ 33 $ 5 $ 11 $ 8 $ 4 $ — $ — $ 13 Gross amounts offset (4 ) (2 ) (2 ) (2 ) — — — — Net amounts presented in Current Liabilities: Other $ 29 $ 3 $ 9 $ 6 $ 4 $ — $ — $ 13 Noncurrent Gross amounts recognized $ 157 $ 6 $ 26 $ 13 $ 3 $ 4 $ — $ 119 Gross amounts offset (1 ) — (1 ) (1 ) — — — — Net amounts presented in Other Noncurrent Liabilities: Other $ 156 $ 6 $ 25 $ 12 $ 3 $ 4 $ — $ 119 Derivative Assets December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Current Gross amounts recognized $ 35 $ 2 $ 2 $ 1 $ 1 $ 1 $ 27 $ 2 Gross amounts offset — — — — — — — — Net amounts presented in Current Assets: Other $ 35 $ 2 $ 2 $ 1 $ 1 $ 1 $ 27 $ 2 Noncurrent Gross amounts recognized $ 16 $ — $ 1 $ 1 $ — $ — $ — $ — Gross amounts offset — — — — — — — — Net amounts presented in Other Noncurrent Assets: Other $ 16 $ — $ 1 $ 1 $ — $ — $ — $ — Derivative Liabilities December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Current Gross amounts recognized $ 66 $ 31 $ 19 $ 8 $ 10 $ 1 $ — $ 11 Gross amounts offset (3 ) (2 ) (2 ) (2 ) — — — — Net amounts presented in Current Liabilities: Other $ 63 $ 29 $ 17 $ 6 $ 10 $ 1 $ — $ 11 Noncurrent Gross amounts recognized $ 164 $ 4 $ 17 $ 10 $ 2 $ 4 $ — $ 131 Gross amounts offset (1 ) — (1 ) (1 ) — — — — Net amounts presented in Other Noncurrent Liabilities: Other $ 163 $ 4 $ 16 $ 9 $ 2 $ 4 $ — $ 131 OBJECTIVE CREDIT CONTINGENT FEATURES Certain derivative contracts contain objective credit contingent features. These features include the requirement to post cash collateral or letters of credit if specific events occur, such as a credit rating downgrade below investment grade. The following tables show information with respect to derivative contracts that are in a net liability position and contain objective credit-risk-related payment provisions. March 31, 2018 Duke Duke Duke Duke Energy Progress Energy Energy (in millions) Energy Carolinas Energy Progress Florida Aggregate fair value of derivatives in a net liability position $ 30 $ 10 $ 20 $ 18 $ 2 Fair value of collateral already posted — — — — — Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered 30 10 20 18 2 December 31, 2017 Duke Duke Duke Duke Energy Progress Energy Energy (in millions) Energy Carolinas Energy Progress Florida Aggregate fair value of derivatives in a net liability position $ 59 $ 35 $ 25 $ 15 $ 10 Fair value of collateral already posted — — — — — Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered 59 35 25 15 10 The Duke Energy Registrants have elected to offset cash collateral and fair values of derivatives. For amounts to be netted, the derivative and cash collateral must be executed with the same counterparty under the same master netting arrangement.

Investments in Debt and Equity

Investments in Debt and Equity Securities	3 Months Ended
	Mar. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Investments In Debt And Equity Securities	INVESTMENTS IN DEBT AND EQUITY SECURITIES Duke Energy’s investments in debt and equity securities are primarily comprised of investments held in (i) the nuclear decommissioning trust 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. The Duke Energy Registrants classify investments in debt securities as available-for-sale (AFS) and investments in equity securities as fair value through net income (FV-NI). For investments in debt securities classified as AFS, the unrealized gains and losses are included in other comprehensive income until realized, at which time, they are reported through net income. For investments in equity securities classified as FV-NI, both realized and unrealized gains and losses are reported through net income. Substantially all of Duke Energy’s investments in debt and equity securities qualify for regulatory accounting, and accordingly, all associated realized and unrealized gains and losses on these investments are deferred as a regulatory asset or liability. Duke Energy classifies the majority of investments in debt and equity securities as long term, unless otherwise noted. Investment Trusts The investments within the NDTF investments and the Duke Energy Progress, Duke Energy Florida and Duke Energy Indiana grantor trusts (Investment Trusts) are managed by independent investment managers with discretion to buy, sell and invest pursuant to the objectives set forth by the trust agreements. The Duke Energy Registrants have limited oversight of the day-to-day management of these investments. As a result, the ability to hold investments in unrealized loss positions is outside the control of the Duke Energy Registrants. Accordingly, all unrealized losses associated with debt securities within the Investment Trusts are considered OTTIs and are recognized immediately and deferred to regulatory accounts where appropriate. Other AFS Securities Unrealized gains and losses on all other AFS securities are included in other comprehensive income until realized, unless it is determined the carrying value of an investment is other-than-temporarily impaired. The Duke Energy Registrants analyze all investment holdings each reporting period to determine whether a decline in fair value should be considered other-than-temporary. If an OTTI exists, the unrealized credit loss is included in earnings. There were no material credit losses as of March 31, 2018 , and December 31, 2017 . Other Investments amounts are recorded in Other within Other Noncurrent Assets on the Condensed Consolidated Balance Sheets. DUKE ENERGY The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. March 31, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 143 $ — $ — $ 115 Equity securities 2,751 38 4,857 2,805 27 4,914 Corporate debt securities 7 8 549 17 2 570 Municipal bonds 1 5 333 4 3 344 U.S. government bonds 6 18 1,014 11 7 1,027 Other debt securities — 2 130 — 1 118 Total NDTF Investments $ 2,765 $ 71 $ 7,026 $ 2,837 $ 40 $ 7,088 Other Investments Cash and cash equivalents $ — $ — $ 15 $ — $ — $ 15 Equity securities 57 — 130 59 — 123 Corporate debt securities — 1 64 1 — 57 Municipal bonds 1 1 80 2 1 83 U.S. government bonds — 1 51 — — 41 Other debt securities — — 48 — 1 44 Total Other Investments $ 58 $ 3 $ 388 $ 62 $ 2 $ 363 Total Investments $ 2,823 $ 74 $ 7,414 $ 2,899 $ 42 $ 7,451 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected . The table below summarizes the maturity date for debt securities. (in millions) March 31, 2018 Due in one year or less $ 100 Due after one through five years 535 Due after five through 10 years 530 Due after 10 years 1,104 Total $ 2,269 Realized gains and losses, which were determined on a specific identification basis, from sales of FV-NI and AFS securities for the three months ended March 31, 2018 and from sales of AFS securities for the three months ended March 31, 2017 were as follows. Three Months Ended (in millions) March 31, 2018 FV-NI: Realized gains $ 19 Realized losses 13 AFS: Realized gains 5 Realized losses 13 Three Months Ended (in millions) March 31, 2017 Realized gains $ 93 Realized losses 62 DUKE ENERGY CAROLINAS The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. March 31, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 50 $ — $ — $ 32 Equity securities 1,502 20 2,669 1,531 12 2,692 Corporate debt securities 3 5 333 9 2 359 Municipal bonds — 1 69 — 1 60 U.S. government bonds 2 11 494 3 4 503 Other debt securities — 2 122 — 1 112 Total NDTF Investments $ 1,507 $ 39 $ 3,737 $ 1,543 $ 20 $ 3,758 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected . The table below summarizes the maturity date for debt securities. (in millions) March 31, 2018 Due in one year or less $ 11 Due after one through five years 178 Due after five through 10 years 285 Due after 10 years 544 Total $ 1,018 Realized gains and losses, which were determined on a specific identification basis, from sales of FV-NI and AFS securities for the three months ended March 31, 2018 and from sales of AFS securities for the three months ended March 31, 2017 were as follows. Three Months Ended (in millions) March 31, 2018 FV-NI: Realized gains $ 10 Realized losses 5 AFS: Realized gains 5 Realized losses 10 Three Months Ended (in millions) March 31, 2017 Realized gains $ 66 Realized losses 40 PROGRESS ENERGY The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. March 31, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 93 $ — $ — $ 83 Equity securities 1,249 18 2,188 1,274 15 2,222 Corporate debt securities 4 3 216 8 — 211 Municipal bonds 1 4 264 4 2 284 U.S. government bonds 4 7 520 8 3 524 Other debt securities — — 8 — — 6 Total NDTF Investments $ 1,258 $ 32 $ 3,289 $ 1,294 $ 20 $ 3,330 Other Investments Cash and cash equivalents $ — $ — $ 10 $ — $ — $ 12 Municipal bonds 1 — 47 2 — 47 Total Other Investments $ 1 $ — $ 57 $ 2 $ — $ 59 Total Investments $ 1,259 $ 32 $ 3,346 $ 1,296 $ 20 $ 3,389 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected . The table below summarizes the maturity date for debt securities. (in millions) March 31, 2018 Due in one year or less $ 75 Due after one through five years 300 Due after five through 10 years 198 Due after 10 years 482 Total $ 1,055 Realized gains and losses, which were determined on a specific identification basis, from sales of FV-NI and AFS securities for the three months ended March 31, 2018 and from sales of AFS securities for the three months ended March 31, 2017 were as follows. Three Months Ended (in millions) March 31, 2018 FV-NI: Realized gains $ 9 Realized losses 8 AFS: Realized losses 3 Three Months Ended (in millions) March 31, 2017 Realized gains $ 27 Realized losses 21 DUKE ENERGY PROGRESS The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. March 31, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 59 $ — $ — $ 50 Equity securities 959 14 1,765 980 12 1,795 Corporate debt securities 3 2 153 6 — 149 Municipal bonds 1 4 263 4 2 283 U.S. government bonds 3 5 326 5 2 310 Other debt securities — — 5 — — 4 Total NDTF Investments $ 966 $ 25 $ 2,571 $ 995 $ 16 $ 2,591 Other Investments Cash and cash equivalents $ — $ — $ 1 $ — $ — $ 1 Total Other Investments $ — $ — $ 1 $ — $ — $ 1 Total Investments $ 966 $ 25 $ 2,572 $ 995 $ 16 $ 2,592 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected . The table below summarizes the maturity date for debt securities. (in millions) March 31, 2018 Due in one year or less $ 19 Due after one through five years 216 Due after five through 10 years 144 Due after 10 years 368 Total $ 747 Realized gains and losses, which were determined on a specific identification basis, from sales of FV-NI and AFS securities for the three months ended March 31, 2018 and from sales of AFS securities for the three months ended March 31, 2017 were as follows. Three Months Ended (in millions) March 31, 2018 FV-NI: Realized gains $ 8 Realized losses 8 AFS: Realized losses 2 Three Months Ended (in millions) March 31, 2017 Realized gains $ 24 Realized losses 19 DUKE ENERGY FLORIDA The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. March 31, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 34 $ — $ — $ 33 Equity securities 290 4 423 294 3 427 Corporate debt securities 1 1 63 2 — 62 Municipal bonds — — 1 — — 1 U.S. government bonds 1 2 194 3 1 214 Other debt securities — — 3 — — 2 Total NDTF Investments (b) $ 292 $ 7 $ 718 $ 299 $ 4 $ 739 Other Investments Cash and cash equivalents $ — $ — $ — $ — $ — $ 1 Municipal bonds 1 — 47 2 — 47 Total Other Investments $ 1 $ — $ 47 $ 2 $ — $ 48 Total Investments $ 293 $ 7 $ 765 $ 301 $ 4 $ 787 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected . (b) During the three months ended March 31, 2018 , Duke Energy Florida continued to receive reimbursements from the NDTF for costs related to ongoing decommissioning activity of the Crystal River Unit 3 nuclear plant. The table below summarizes the maturity date for debt securities. (in millions) March 31, 2018 Due in one year or less $ 56 Due after one through five years 84 Due after five through 10 years 54 Due after 10 years 114 Total $ 308 Realized gains and losses, which were determined on a specific identification basis, from sales of FV-NI and AFS securities for the three months ended March 31, 2018 and from sales of AFS securities for the three months ended March 31, 2017 were as follows. Three Months Ended (in millions) March 31, 2018 FV-NI: Realized gains $ 1 AFS: Realized losses 1 Three Months Ended (in millions) March 31, 2017 Realized gains $ 3 Realized losses 2 DUKE ENERGY INDIANA The following table presents the estimated fair value of investments in debt and equity securities; equity investments are measured at FV-NI and debt investments are classified as AFS. March 31, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value Investments Equity securities $ 48 $ — $ 96 $ 49 $ — $ 97 Corporate debt securities — — 5 — — 3 Municipal bonds — 1 26 — 1 28 Total Investments $ 48 $ 1 $ 127 $ 49 $ 1 $ 128 (a) Realized and unrealized gains and losses where regulatory accounting is applied are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected . The table below summarizes the maturity date for debt securities. (in millions) March 31, 2018 Due in one year or less $ 3 Due after one through five years 15 Due after five through 10 years 6 Due after 10 years 7 Total $ 31 Realized gains and losses, which were determined on a specific identification basis, from sales of FV-NI and AFS securities for the three months ended March 31, 2018 , and from sales of AFS securities for the three months ended March 31, 2017 , were insignificant.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	FAIR VALUE MEASUREMENTS Fair value is the exchange price to sell an asset or transfer a liability in an orderly transaction between market participants at the measurement date. The fair value definition focuses on an exit price versus the acquisition cost. Fair value measurements use market data or assumptions market participants would use in pricing the asset or liability, including assumptions about risk and the risks inherent in the inputs to the valuation technique. These inputs may be readily observable, corroborated by market data or generally unobservable. Valuation techniques maximize the use of observable inputs and minimize use of unobservable inputs. A midmarket pricing convention (the midpoint price between bid and ask prices) is permitted for use as a practical expedient. Fair value measurements are classified in three levels based on the fair value hierarchy: Level 1 – Unadjusted quoted prices in active markets for identical assets or liabilities that the reporting entity can access at the measurement date. An active market is one in which transactions for an asset or liability occur with sufficient frequency and volume to provide ongoing pricing information. Level 2 – A fair value measurement utilizing inputs other than quoted prices included in Level 1 that are observable, either directly or indirectly, for an asset or liability. Inputs include (i) quoted prices for similar assets or liabilities in active markets, (ii) quoted prices for identical or similar assets or liabilities in markets that are not active and (iii) inputs other than quoted market prices that are observable for the asset or liability, such as interest rate curves and yield curves observable at commonly quoted intervals, volatilities and credit spreads. A Level 2 measurement cannot have more than an insignificant portion of its valuation based on unobservable inputs. Instruments in this category include non-exchange-traded derivatives, such as over-the-counter forwards, swaps and options; certain marketable debt securities; and financial instruments traded in less-than-active markets. Level 3 – Any fair value measurement that includes unobservable inputs for more than an insignificant portion of the valuation. These inputs may be used with internally developed methodologies that result in management’s best estimate of fair value. Level 3 measurements may include longer-term instruments that extend into periods in which observable inputs are not available. Not Categorized – Certain investments are not categorized within the Fair Value hierarchy. These investments are measured at fair value using the net asset value (NAV) per share practical expedient. The NAV is derived based on the investment cost, less any impairment, plus or minus changes resulting from observable price changes for an identical or similar investment of the same issuer. Fair value accounting guidance permits entities to elect to measure certain financial instruments that are not required to be accounted for at fair value, such as equity method investments or the company’s own debt, at fair value. The Duke Energy Registrants have not elected to record any of these items at fair value. Transfers between levels represent assets or liabilities that were previously (i) categorized at a higher level for which the inputs to the estimate became less observable or (ii) classified at a lower level for which the inputs became more observable during the period. The Duke Energy Registrant’s policy is to recognize transfers between levels of the fair value hierarchy at the end of the period. There were no transfers between levels during the three months ended March 31, 2018 , and 2017 . Valuation methods of the primary fair value measurements disclosed below are as follows. Investments in equity securities The majority of investments in equity securities are valued using Level 1 measurements. Investments in equity securities are typically valued at the closing price in the principal active market as of the last business day of the quarter. Principal active markets for equity prices include published exchanges such as New York Stock Exchange and Nasdaq Stock Market. Foreign equity prices are translated from their trading currency using the currency exchange rate in effect at the close of the principal active market. There was no after-hours market activity that was required to be reflected in the reported fair value measurements. Investments in debt securities Most investments in debt securities are valued using Level 2 measurements because the valuations use interest rate curves and credit spreads applied to the terms of the debt instrument (maturity and coupon interest rate) and consider the counterparty credit rating. If the market for a particular fixed-income security is relatively inactive or illiquid, the measurement is Level 3. Commodity derivatives Commodity derivatives with clearinghouses are classified as Level 1. Other commodity derivatives, including Piedmont's natural gas supply contracts, are primarily valued using internally developed discounted cash flow models that incorporate forward price, adjustments for liquidity (bid-ask spread) and credit or non-performance risk (after reflecting credit enhancements such as collateral), and are discounted to present value. Pricing inputs are derived from published exchange transaction prices and other observable data sources. In the absence of an active market, the last available price may be used. If forward price curves are not observable for the full term of the contract and the unobservable period had more than an insignificant impact on the valuation, the commodity derivative is classified as Level 3. In isolation, increases (decreases) in natural gas forward prices result in favorable (unfavorable) fair value adjustments for natural gas purchase contracts; and increases (decreases) in electricity forward prices result in unfavorable (favorable) fair value adjustments for electricity sales contracts. Duke Energy regularly evaluates and validates pricing inputs used to estimate the fair value of natural gas commodity contracts by a market participant price verification procedure. This procedure provides a comparison of internal forward commodity curves to market participant generated curves. Interest rate derivatives Most over-the-counter interest rate contract derivatives are valued using financial models that utilize observable inputs for similar instruments and are classified as Level 2. Inputs include forward interest rate curves, notional amounts, interest rates and credit quality of the counterparties. Other fair value considerations See Note 11 in Duke Energy's Annual Report on Form 10-K/A for the year ended December 31, 2017, for a discussion of the valuation of goodwill and intangible assets. DUKE ENERGY The following tables provide recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets. Derivative amounts in the tables below for all Duke Energy Registrants exclude cash collateral, which is disclosed in Note 8 . See Note 9 for additional information related to investments by major security type for the Duke Energy Registrants. March 31, 2018 (in millions) Total Fair Value Level 1 Level 2 Level 3 Not Categorized NDTF equity securities $ 4,857 $ 4,785 $ — $ — $ 72 NDTF debt securities 2,169 633 1,536 — — Other equity securities 130 130 — — — Other debt securities 258 66 192 — — Derivative assets 37 2 27 8 — Total assets 7,451 5,616 1,755 8 72 Derivative liabilities (190 ) (1 ) (57 ) (132 ) — Net assets (liabilities) $ 7,261 $ 5,615 $ 1,698 $ (124 ) $ 72 December 31, 2017 (in millions) Total Fair Value Level 1 Level 2 Level 3 Not Categorized NDTF equity securities $ 4,914 $ 4,840 $ — $ — $ 74 NDTF debt securities 2,174 635 1,539 — — Other equity securities 123 123 — — — Other debt securities 241 57 184 — — Derivative assets 51 3 20 28 — Total assets 7,503 5,658 1,743 28 74 Derivative liabilities (230 ) (2 ) (86 ) (142 ) — Net assets (liabilities) $ 7,273 $ 5,656 $ 1,657 $ (114 ) $ 74 The following table provides 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 March 31, 2018 Three Months Ended March 31, 2017 (in millions) Investments Derivatives (net) Total Investments Derivatives (net) Total Balance at beginning of period $ — $ (114 ) $ (114 ) $ 5 $ (166 ) $ (161 ) Purchases, sales, issuances and settlements: Settlements — (14 ) (14 ) — (9 ) (9 ) Total gains included on the Condensed Consolidated Balance Sheet — 4 4 — 40 40 Balance at end of period $ — $ (124 ) $ (124 ) $ 5 $ (135 ) $ (130 ) 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. March 31, 2018 (in millions) Total Fair Value Level 1 Level 2 Not Categorized NDTF equity securities $ 2,669 $ 2,597 $ — $ 72 NDTF debt securities 1,068 209 859 — Derivative assets 2 — 2 — Total assets 3,739 2,806 861 72 Derivative liabilities (11 ) (1 ) (10 ) — Net assets $ 3,728 $ 2,805 $ 851 $ 72 December 31, 2017 (in millions) Total Fair Value Level 1 Level 2 Not Categorized NDTF equity securities $ 2,692 $ 2,618 $ — $ 74 NDTF debt securities 1,066 204 862 — Derivative assets 2 — 2 — Total assets 3,760 2,822 864 74 Derivative liabilities (35 ) (1 ) (34 ) — Net assets $ 3,725 $ 2,821 $ 830 $ 74 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. March 31, 2018 (in millions) Total Fair Value Level 1 Level 2 NDTF equity securities $ 2,188 $ 2,188 $ — NDTF debt securities 1,101 424 677 Other debt securities 57 10 47 Derivative assets 3 — 3 Total assets 3,349 2,622 727 Derivative liabilities (37 ) (1 ) (36 ) Net assets $ 3,312 $ 2,621 $ 691 December 31, 2017 (in millions) Total Fair Value Level 1 Level 2 NDTF equity securities $ 2,222 $ 2,222 $ — NDTF debt securities 1,108 431 677 Other debt securities 59 12 47 Derivative assets 3 1 2 Total assets 3,392 2,666 726 Derivative liabilities (36 ) (1 ) (35 ) Net assets $ 3,356 $ 2,665 $ 691 DUKE ENERGY PROGRESS The following tables provide recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets. March 31, 2018 (in millions) Total Fair Value Level 1 Level 2 NDTF equity securities $ 1,765 $ 1,765 $ — NDTF debt securities 806 254 552 Other debt securities 1 1 — Derivative assets 2 — 2 Total assets 2,574 2,020 554 Derivative liabilities (21 ) (1 ) (20 ) Net assets $ 2,553 $ 2,019 $ 534 December 31, 2017 (in millions) Total Fair Value Level 1 Level 2 NDTF equity securities $ 1,795 $ 1,795 $ — NDTF debt securities 796 243 553 Other debt securities 1 1 — Derivative assets 2 1 1 Total assets 2,594 2,040 554 Derivative liabilities (18 ) (1 ) (17 ) Net assets $ 2,576 $ 2,039 $ 537 DUKE ENERGY FLORIDA The following tables provide recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets. March 31, 2018 (in millions) Total Fair Value Level 1 Level 2 NDTF equity securities $ 423 $ 423 $ — NDTF debt securities 295 170 125 Other debt securities 47 — 47 Derivative assets 1 — 1 Total assets 766 593 173 Derivative liabilities (7 ) — (7 ) Net assets $ 759 $ 593 $ 166 December 31, 2017 (in millions) Total Fair Value Level 1 Level 2 NDTF equity securities $ 427 $ 427 $ — NDTF debt securities 312 188 124 Other debt securities 48 1 47 Derivative assets 1 — 1 Total assets 788 616 172 Derivative liabilities (12 ) — (12 ) Net assets $ 776 $ 616 $ 160 DUKE ENERGY OHIO The following table provides recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets. March 31, 2018 December 31, 2017 (in millions) Total Fair Value Level 2 Level 3 Total Fair Value Level 2 Level 3 Derivative assets $ 1 $ — $ 1 $ 1 $ — $ 1 Derivative liabilities (4 ) (4 ) — (5 ) (5 ) — Net (liabilities) assets $ (3 ) $ (4 ) $ 1 $ (4 ) $ (5 ) $ 1 The following table provides a reconciliation of beginning and ending balances of assets and liabilities measured at fair value using Level 3 measurements. Derivatives (net) Three Months Ended March 31, (in millions) 2018 2017 Balance at beginning of period $ 1 $ 5 Purchases, sales, issuances and settlements: Settlements — (1 ) Total losses included on the Condensed Consolidated Balance Sheet — (3 ) Balance at end of period $ 1 $ 1 DUKE ENERGY INDIANA The following tables provide recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets. March 31, 2018 (in millions) Total Fair Value Level 1 Level 2 Level 3 Other equity securities $ 96 $ 96 $ — $ — Other debt securities 31 — 31 — Derivative assets 7 — — 7 Total assets 134 96 31 7 Derivative liabilities — — — — Net assets $ 134 $ 96 $ 31 $ 7 December 31, 2017 (in millions) Total Fair Value Level 1 Level 2 Level 3 Other equity securities $ 97 $ 97 $ — $ — Other debt securities 31 — 31 — Derivative assets 27 — — 27 Total assets 155 97 31 27 Derivative liabilities — — — — Net assets $ 155 $ 97 $ 31 $ 27 The following table provides a reconciliation of beginning and ending balances of assets and liabilities measured at fair value using Level 3 measurements. Derivatives (net) Three Months Ended March 31, (in millions) 2018 2017 Balance at beginning of period $ 27 $ 16 Purchases, sales, issuances and settlements: Settlements (14 ) (7 ) Total (losses) gains included on the Condensed Consolidated Balance Sheet (6 ) — Balance at end of period $ 7 $ 9 PIEDMONT The following tables provide recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets. March 31, 2018 (in millions) Total Fair Value Level 1 Level 3 Derivative assets $ 1 $ 1 $ — Derivative liabilities (132 ) — (132 ) Net (liabilities) assets $ (131 ) $ 1 $ (132 ) December 31, 2017 (in millions) Total Fair Value Level 1 Level 3 Other debt securities $ 1 $ 1 $ — Derivative assets 2 2 — Total assets 3 3 — Derivative liabilities (142 ) — (142 ) Net (liabilities) assets $ (139 ) $ 3 $ (142 ) The following table provides a reconciliation of beginning and ending balances of assets and liabilities measured at fair value using Level 3 measurements. Derivatives (net) Three Months Ended March 31, (in millions) 2018 2017 Balance at beginning of period $ (142 ) $ (187 ) Total gains and settlements 10 42 Balance at end of period $ (132 ) $ (145 ) QUANTITATIVE INFORMATION ABOUT UNOBSERVABLE INPUTS The following tables include quantitative information about the Duke Energy Registrants' derivatives classified as Level 3. March 31, 2018 Fair Value Investment Type (in millions) Valuation Technique Unobservable Input Range Duke Energy Ohio Financial Transmission Rights (FTRs) $ 1 RTO auction pricing FTR price – per megawatt-hour (MWh) $ — - $ 2.88 Duke Energy Indiana FTRs 7 RTO auction pricing FTR price – per MWh (5.09 ) - 7.58 Piedmont Natural gas contracts (132 ) Discounted cash flow Forward natural gas curves – price per million British thermal unit (MMBtu) 2.15 - 3.65 Duke Energy Total Level 3 derivatives $ (124 ) December 31, 2017 Fair Value Investment Type (in millions) Valuation Technique Unobservable Input Range Duke Energy Ohio FTRs $ 1 RTO auction pricing FTR price – per MWh $ 0.07 - $ 1.41 Duke Energy Indiana FTRs 27 RTO auction pricing FTR price – per MWh (0.77 ) - 7.44 Piedmont Natural gas contracts (142 ) Discounted cash flow Forward natural gas curves – price per MMBtu 2.10 - 2.88 Duke Energy Total Level 3 derivatives $ (114 ) OTHER FAIR VALUE DISCLOSURES The fair value and book value of long-term debt, including current maturities, is summarized in the following table. Estimates determined are not necessarily indicative of amounts that could have been settled in current markets. Fair value of long-term debt uses Level 2 measurements. March 31, 2018 December 31, 2017 (in millions) Book Value Fair Value Book Value Fair Value Duke Energy $ 52,981 $ 54,383 $ 52,279 $ 55,331 Duke Energy Carolinas 10,694 11,556 10,103 11,372 Progress Energy 17,757 19,270 17,837 20,000 Duke Energy Progress 7,357 7,687 7,357 7,992 Duke Energy Florida 7,015 7,632 7,095 7,953 Duke Energy Ohio 2,067 2,217 2,067 2,249 Duke Energy Indiana 3,782 4,322 3,783 4,464 Piedmont 2,037 2,209 2,037 2,209 At both March 31, 2018 , and December 31, 2017 , fair value of cash and cash equivalents, accounts and notes receivable, accounts payable, notes payable and commercial paper, and nonrecourse notes payable of VIEs are not materially different from their carrying amounts because of the short-term nature of these instruments and/or because the stated rates approximate market rates.

Variable Interest Entities

Variable Interest Entities	3 Months Ended
	Mar. 31, 2018
Variable Interest Entities [Abstract]
Variable Interest Entities	VARIABLE INTEREST ENTITIES A VIE is an entity that is evaluated for consolidation using more than a simple analysis of voting control. The analysis to determine whether an entity is a VIE considers contracts with an entity, credit support for an entity, the adequacy of the equity investment of an entity and the relationship of voting power to the amount of equity invested in an entity. This analysis is performed either upon the creation of a legal entity or upon the occurrence of an event requiring re-evaluation, such as a significant change in an entity’s assets or activities. A qualitative analysis of control determines the party that consolidates a VIE. This assessment is based on (i) what party has the power to direct the activities of the VIE that most significantly impact its economic performance and (ii) what party has rights to receive benefits or is obligated to absorb losses that could potentially be significant to the VIE. The analysis of the party that consolidates a VIE is a continual reassessment. CONSOLIDATED VIEs The obligations of the consolidated VIEs discussed in the following paragraphs are nonrecourse to the Duke Energy registrants. The registrants have no requirement to provide liquidity to, purchase assets of or guarantee performance of these VIEs unless noted in the following paragraphs. No financial support was provided to any of the consolidated VIEs during the three months ended March 31, 2018 , and the year ended December 31, 2017 , or is expected to be provided in the future, that was not previously contractually required. Receivables Financing – DERF / DEPR / DEFR Duke Energy Receivables Finance Company, LLC (DERF), Duke Energy Progress Receivables, LLC (DEPR) and Duke Energy Florida Receivables, LLC (DEFR) are bankruptcy remote, special purpose subsidiaries of Duke Energy Carolinas, Duke Energy Progress and Duke Energy Florida, respectively. DERF, DEPR and DEFR are wholly owned limited liability companies with separate legal existence from their parent companies, and their assets are not generally available to creditors of their parent companies. On a revolving basis, DERF, DEPR and DEFR buy certain accounts receivable arising from the sale of electricity and related services from their parent companies. DERF, DEPR and DEFR borrow amounts under credit facilities to buy these receivables. Borrowing availability from the credit facilities is limited to the amount of qualified receivables purchased. The sole source of funds to satisfy the related debt obligations is cash collections from the receivables. Amounts borrowed under the credit facilities are reflected on the Condensed Consolidated Balance Sheets as Long-Term Debt. The most significant activity that impacts the economic performance of DERF, DEPR and DEFR are the decisions made to manage delinquent receivables. Duke Energy Carolinas, Duke Energy Progress and Duke Energy Florida consolidate DERF, DEPR and DEFR, respectively, as they make those decisions. Receivables Financing – CRC CRC is a bankruptcy remote, special purpose entity indirectly owned by Duke Energy. On a revolving basis, CRC buys certain accounts receivable arising from the sale of electricity, natural gas and related services from Duke Energy Ohio and Duke Energy Indiana. CRC borrows amounts under a credit facility to buy the receivables from Duke Energy Ohio and Duke Energy Indiana. Borrowing availability from the credit facility is limited to the amount of qualified receivables sold to CRC. The sole source of funds to satisfy the related debt obligation is cash collections from the receivables. Amounts borrowed under the credit facility are reflected on Duke Energy's Condensed Consolidated Balance Sheets as Long-Term Debt. The proceeds Duke Energy Ohio and Duke Energy Indiana receive from the sale of receivables to CRC are typically 75 percent cash and 25 percent in the form of a subordinated note from CRC. The subordinated note is a retained interest in the receivables sold. Depending on collection experience, additional equity infusions to CRC may be required by Duke Energy to maintain a minimum equity balance of $3 million . CRC is considered a VIE because (i) equity capitalization is insufficient to support its operations, (ii) power to direct the activities that most significantly impact the economic performance of the entity are not performed by the equity holder and (iii) deficiencies in net worth of CRC are funded by Duke Energy. The most significant activities that impact the economic performance of CRC are decisions made to manage delinquent receivables. Duke Energy consolidates CRC as it makes these decisions. Neither Duke Energy Ohio nor Duke Energy Indiana consolidate CRC. Receivables Financing – Credit Facilities The following table summarizes the amounts and expiration dates of the credit facilities and associated restricted receivables described above. Duke Energy Duke Energy Duke Energy Duke Energy Carolinas Progress Florida (in millions) CRC DERF DEPR DEFR Expiration date December 2020 December 2020 February 2021 April 2019 (a) Credit facility amount $ 325 $ 450 $ 300 $ 225 Amounts borrowed at March 31, 2018 325 450 300 225 Amounts borrowed at December 31, 2017 325 450 300 225 Restricted Receivables at March 31, 2018 504 634 497 313 Restricted Receivables at December 31, 2017 545 640 459 317 (a) In April 2018, the credit facility was extended through April 2021 . Nuclear Asset-Recovery Bonds – DEFPF Duke Energy Florida Project Finance, LLC (DEFPF) is a bankruptcy remote, wholly owned special purpose subsidiary of Duke Energy Florida. DEFPF was formed in 2016 for the sole purpose of issuing nuclear asset-recovery bonds to finance Duke Energy Florida's unrecovered regulatory asset related to Crystal River Unit 3. In June 2016, DEFPF issued senior secured bonds and used the proceeds to acquire nuclear asset-recovery property from Duke Energy Florida. The nuclear asset-recovery property acquired includes the right to impose, bill, collect and adjust a non-bypassable nuclear asset-recovery charge from all Duke Energy Florida retail customers until the bonds are paid in full and all financing costs have been recovered. The nuclear asset-recovery bonds are secured by the nuclear asset-recovery property, and cash collections from the nuclear asset-recovery charges are the sole source of funds to satisfy the debt obligation. The bondholders have no recourse to Duke Energy Florida. DEFPF is considered a VIE primarily because the equity capitalization is insufficient to support its operations. Duke Energy Florida has the power to direct the significant activities of the VIE as described above, and therefore Duke Energy Florida is considered the primary beneficiary and consolidates DEFPF. The following table summarizes the impact of DEFPF on Duke Energy Florida's Condensed Consolidated Balance Sheets. (in millions) March 31, 2018 December 31, 2017 Receivables of VIEs $ 4 $ 4 Regulatory Assets: Current 51 51 Current Assets: Other 13 40 Other Noncurrent Assets: Regulatory assets 1,082 1,091 Current Liabilities: Other 3 10 Current maturities of long-term debt 53 53 Long-Term Debt 1,136 1,164 Commercial Renewables Certain of Duke Energy’s renewable energy facilities are VIEs due to Duke Energy issuing guarantees for debt service and operations and maintenance reserves in support of debt financings. Assets are restricted and cannot be pledged as collateral or sold to third parties without prior approval of debt holders. The activities that most significantly impact the economic performance of these renewable energy facilities were decisions associated with siting, negotiating PPAs, engineering, procurement and construction and decisions associated with ongoing operations and maintenance-related activities. Duke Energy consolidates the entities as it is responsible for all of these decisions. The table below presents material balances reported on Duke Energy's Condensed Consolidated Balance Sheets related to renewables VIEs. (in millions) March 31, 2018 December 31, 2017 Current Assets: Other $ 217 $ 174 Property, plant and equipment, cost 4,017 3,923 Other Noncurrent Assets: Other 227 50 Accumulated depreciation and amortization (626 ) (591 ) Current maturities of long-term debt 171 170 Long-Term Debt 1,700 1,700 Other Noncurrent Liabilities: Deferred income taxes — (148 ) Other Noncurrent Liabilities: Other 236 241 NON-CONSOLIDATED VIEs The following tables summarize the impact of non-consolidated VIEs on the Condensed Consolidated Balance Sheets. March 31, 2018 Duke Energy Duke Duke Pipeline Commercial Other Energy Energy (in millions) Investments Renewables VIEs Total Ohio Indiana Receivables from affiliated companies $ — $ — $ — $ — $ 65 $ 86 Investments in equity method unconsolidated affiliates 723 183 45 951 — — Other noncurrent assets 17 — — 17 — — Total assets $ 740 $ 183 $ 45 $ 968 $ 65 $ 86 Taxes accrued (29 ) — — (29 ) — — Other current liabilities — — 3 3 — — Deferred income taxes 32 — — 32 — — Other noncurrent liabilities 8 — 12 20 — — Total liabilities $ 11 $ — $ 15 $ 26 $ — $ — Net assets $ 729 $ 183 $ 30 $ 942 $ 65 $ 86 December 31, 2017 Duke Energy Duke Duke Pipeline Commercial Other Energy Energy (in millions) Investments Renewables VIEs Total Ohio Indiana Receivables from affiliated companies $ — $ — $ — $ — $ 87 $ 106 Investments in equity method unconsolidated affiliates 697 180 42 919 — — Other noncurrent assets 17 — — 17 — — Total assets $ 714 $ 180 $ 42 $ 936 $ 87 $ 106 Taxes accrued (29 ) — — (29 ) — — Other current liabilities — — 4 4 — — Deferred income taxes 42 — — 42 — — Other noncurrent liabilities — — 12 12 — — Total liabilities $ 13 $ — $ 16 $ 29 $ — $ — Net assets $ 701 $ 180 $ 26 $ 907 $ 87 $ 106 The Duke Energy Registrants are not aware of any situations where the maximum exposure to loss significantly exceeds the carrying values shown above except for the power purchase agreement with OVEC, which is discussed below, and various guarantees, some of which are reflected in the table above as Other noncurrent liabilities. For more information on various guarantees, refer to Note 4 . Pipeline Investments Duke Energy has investments in various joint ventures with pipeline projects currently under construction. These entities are considered VIEs due to having insufficient equity to finance their own activities without subordinated financial support. Duke Energy does not have the power to direct the activities that most significantly impact the economic performance, the obligation to absorb losses or the right to receive benefits of these VIEs and therefore does not consolidate these entities. The table below presents Duke Energy's ownership interest and investment balances in these joint ventures. VIE Investment Amount (in millions) Ownership March 31, December 31, Entity Name Interest 2018 2017 ACP 47 % $ 474 $ 397 Sabal Trail 7.5 % 223 219 Constitution (a) 24 % 26 81 Total $ 723 $ 697 (a) During the three months ended March 31, 2018 , Duke Energy recorded an OTTI of $55 million related to Constitution within Equity in (losses) earnings of unconsolidated affiliates on Duke Energy's Condensed Consolidated Statements of Income. See Note 3 for additional information. In 2017, ACP executed a $3.4 billion revolving credit facility with a stated maturity date of October 2021. Duke Energy entered into a guarantee agreement to support its share of the ACP revolving credit facility. Duke Energy's maximum exposure to loss under the terms of the guarantee is limited to 47 percent of the outstanding borrowings under the credit facility, which was $346 million as of March 31, 2018 . On April 30, 2018, Sabal Trail closed on a $1.5 billion offering of senior notes. The notes were issued in three tranches due in 2028, 2038 and 2048. Duke Energy received $112 million of net proceeds as a result of the offering. As a result of the financing, Sabal Trail has sufficient equity to finance its own activities without additional subordinated financial support from other parties and will no longer be considered a VIE. 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. Deterioration in the credit quality or bankruptcy of one or more parties to the ICPA could increase the costs of OVEC. On March 31, 2018, FirstEnergy Solutions (FES), a subsidiary of FirstEnergy and counterparty to the ICPA, filed for Chapter 11 bankruptcy. FES has a power participation ratio of 4.85 percent. Duke Energy Ohio cannot predict the impact of the bankruptcy on its OVEC interests. 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 2018 2017 2018 2017 Anticipated credit loss ratio 0.5 % 0.5 % 0.3 % 0.3 % Discount rate 2.6 % 2.1 % 2.6 % 2.1 % Receivable turnover rate 13.6 % 13.5 % 10.8 % 10.7 % The following table shows the gross and net receivables sold. Duke Energy Ohio Duke Energy Indiana (in millions) March 31, 2018 December 31, 2017 March 31, 2018 December 31, 2017 Receivables sold $ 249 $ 273 $ 297 $ 312 Less: Retained interests 65 87 86 106 Net receivables sold $ 184 $ 186 $ 211 $ 206 The following table shows sales and cash flows related to receivables sold. Duke Energy Ohio Duke Energy Indiana Three Months Ended Three Months Ended March 31, March 31, (in millions) 2018 2017 2018 2017 Sales Receivables sold $ 567 $ 533 $ 694 $ 664 Loss recognized on sale 3 2 3 3 Cash flows Cash proceeds from receivables sold $ 585 $ 559 $ 711 $ 693 Return received on retained interests 2 1 2 2 Cash flows from sales of receivables are reflected within Operating Activities on Duke Energy Ohio’s and Duke Energy Indiana’s Condensed Consolidated Statements of Cash Flows. Collection fees received in connection with servicing transferred accounts receivable are included in Operation, maintenance and other on Duke Energy Ohio’s and Duke Energy Indiana’s Condensed Consolidated Statements of Operations and Comprehensive Income. The loss recognized on sales of receivables is calculated monthly by multiplying receivables sold during the month by the required discount. The required discount is derived monthly utilizing a three-year weighted average formula that considers charge-off history, late charge history and turnover history on the sold receivables, as well as a component for the time value of money. The discount rate, or component for the time value of money, is the prior month-end LIBOR plus a fixed rate of 1.00 percent .

Revenue

Revenue	3 Months Ended
	Mar. 31, 2018
Revenue from Contract with Customer [Abstract]
Revenue	REVENUE As described in Note 1, Duke Energy adopted Revenue from Contracts with Customers effective January 1, 2018, using the modified retrospective method of adoption which does not require restatement of prior year reported results. No cumulative effect adjustment was recorded as the vast majority of Duke Energy’s revenues are at-will and without a defined contractual term. Additionally, comparative disclosures for 2018 operating results with the previous revenue recognition rules are not applicable as Duke Energy’s revenue recognition has not materially changed as a result of the new standard. Duke Energy recognizes revenue consistent with amounts billed under tariff offerings or at contractually agreed upon rates based on actual physical delivery of electric or natural gas service, including estimated volumes delivered when billings have not yet occurred. As such, the majority of Duke Energy’s revenues have fixed pricing based on the contractual terms of the published tariffs, with variability in expected cash flows attributable to the customer’s volumetric demand and ultimate quantities of energy or natural gas supplied and used during the billing period. The stand-alone selling price of related sales are designed to support recovery of prudently incurred costs and an appropriate return on invested assets and are primarily governed by published tariff rates or contractual agreements approved by relevant regulatory bodies. As described in Note 1, certain excise taxes and franchise fees levied by state or local governments are required to be paid even if not collected from the customer. These taxes are recognized on a gross basis as part of revenues. Duke Energy elects to account for all other taxes net of revenues. Performance obligations are satisfied over time as energy or natural gas is delivered and consumed with billings generally occurring monthly and related payments due within 30 days, depending on regulatory requirements. In no event does the timing between payment and delivery of the goods and services exceed one year. Using this output method for revenue recognition provides a faithful depiction of the transfer of electric and natural gas service as customers obtain control of the commodity and benefit from its use at delivery. Additionally, Duke Energy has an enforceable right to consideration for energy or natural gas delivered at any discrete point in time, and will recognize revenue at an amount that reflects the consideration to which Duke Energy is entitled for the energy or natural gas delivered. As described above, the majority of Duke Energy’s tariff revenues are at-will and, as such, related contracts with customers have an expected duration of one year or less and will not have future performance obligations for disclosure. Additionally, other long-term revenue streams, including wholesale contracts, generally provide services that are part of a single performance obligation, the delivery of electricity or natural gas. As such, other than material fixed consideration under long-term contract, related disclosures for future performance obligations are also not applicable. Duke Energy earns substantially all of its revenues through its reportable segments, Electric Utilities and Infrastructure, Gas Utilities and Infrastructure and Commercial Renewables. Electric Utilities and Infrastructure Electric Utilities and Infrastructure earns the majority of its revenues through retail and wholesale electric service through the generation, transmission, distribution and sale of electricity. Duke Energy generally provides retail and wholesale electric service customers with their full electric load requirements or with supplemental load requirements when the customer has other sources of electricity. Retail electric service is generally marketed throughout Duke Energy's electric service territory through standard service offers. The standard service offers are through tariffs determined by regulators in Duke Energy's regulated service territory. Each tariff, which is assigned to customers based on customer class, has multiple components such as an energy charge, a demand charge, a basic facilities charge, and applicable riders. Duke Energy considers each of these components to be aggregated into a single performance obligation for providing electric service, or in the case of distribution only customers in Duke Energy Ohio, for delivering electricity. Electricity is considered a single performance obligation satisfied over time consistent with the series guidance and is provided and consumed over the billing period (generally one month) . Retail electric service is typically provided to at-will customers that can cancel service at any time, without a substantive penalty . Additionally, Duke Energy adheres to applicable regulatory requirements in each jurisdiction to ensure the collectability of amounts billed and appropriate mitigating procedures are followed when necessary. As such, revenue from contracts with customers for such contracts is equivalent to the electricity supplied and billed in that period (including estimated billings). Wholesale electric service is generally provided under long-term contracts using cost-based pricing. FERC regulates costs that may be recovered from customers and the amount of return companies are permitted to earn. Wholesale contracts include both energy and demand charges. For full requirements contracts, Duke Energy considers both charges as a single performance obligation for providing integrated electric service. For contracts where energy and demand charges are considered separate performance obligations, energy and demand are each a distinct performance obligation under the series guidance and are satisfied as energy is delivered and stand-ready service is provided on a monthly basis. This service represents consumption over the billing period and revenue is recognized consistent with billings and unbilled estimates, which generally occur monthly. Contractual amounts owed are typically trued up annually based upon incurred costs in accordance with FERC published filings and the specific customer’s actual peak demand. Estimates of variable consideration related to potential additional billings or refunds owed are updated quarterly. The majority of wholesale revenues are full requirements contracts where the customers purchase the substantial majority of their energy needs and do not have a fixed quantity of contractually required energy or capacity. As such, related forecasted revenues are considered optional purchases. Supplemental requirements contracts that include contracted blocks of energy and capacity at contractually fixed prices have the following estimated remaining performance obligations: Remaining Performance Obligations (in millions) 2018 2019 2020 2021 2022 Thereafter Total Progress Energy $ 69 $ 112 $ 121 $ 80 $ 82 $ 81 $ 545 Duke Energy Progress 7 9 9 9 9 18 61 Duke Energy Florida 62 103 112 71 73 63 484 Duke Energy Indiana 6 9 10 5 — — 30 Revenues for block sales are recognized monthly as energy is delivered and stand-ready service is provided, consistent with invoiced amounts and unbilled estimates. Gas Utilities and Infrastructure Gas Utilities and Infrastructure earns its revenue through retail and wholesale natural gas service through the transportation, distribution and sale of natural gas. Duke Energy generally provides retail and wholesale natural gas service customers with all natural gas load requirements. Additionally, while natural gas can be stored, substantially all natural gas provided by Duke Energy is consumed by customers simultaneously with receipt of delivery. Retail natural gas service is marketed throughout Duke Energy's natural gas service territory using published tariff rates. The tariff rates are established by regulators in Duke Energy's service territories. Each tariff, which is assigned to customers based on customer class, have multiple components, such as a commodity charge , demand charge, customer or monthly charge, and transportation costs. Duke Energy considers each of these components to be aggregated into a single performance obligation for providing natural gas service. For contracts where Duke Energy provides all of the customer’s natural gas needs, the delivery of natural gas is considered a single performance obligation satisfied over time, and revenue is recognized monthly based on billings and unbilled estimates as service is provided and the commodity is consumed over the billing period. Additionally, natural gas service is typically at-will and customers can cancel service at any time, without a substantive penalty . Duke Energy also adheres to applicable regulatory requirements to ensure the collectability of amounts billed and receivable and appropriate mitigating procedures are followed when necessary . Certain long-term individually negotiated contracts exist to provide natural gas service. These contracts are regulated and approved by state commissions. The negotiated contracts have multiple components, including a natural gas and a demand charge, similar to retail natural gas contracts. Duke Energy considers each of these components to be a single performance obligation for providing natural gas service. This service represents consumption over the billing period, generally one month. Fixed capacity payments under long-term contracts for the Gas segment include minimum margin contracts and supply arrangements with municipalities and power generation facilities. Revenues for related sales are recognized monthly as natural gas is delivered and stand-ready service is provided, consistent with invoiced amounts and unbilled estimates. Estimated remaining performance obligations are as follows: Remaining Performance Obligations (in millions) 2018 2019 2020 2021 2022 Thereafter Total Piedmont $ 55 $ 72 $ 70 $ 65 $ 64 $ 482 $ 808 Commercial Renewables Commercial Renewables earns the majority of its revenues through long-term PPAs and generally sells all of its wind and solar facility output, electricity and Renewable Energy Credits (RECs) to customers. The majority of these PPAs have historically been accounted for as leases. For PPAs that are not accounted for as leases, the delivery of electricity and the delivery of RECs are considered separate performance obligations. The delivery of electricity is a performance obligation satisfied over time and represents generation and consumption of the electricity over the billing period, generally one month. The delivery of RECs is a performance obligation satisfied at a point in time and represents delivery of each REC generated by the wind or solar facility. The majority of self-generated RECs are bundled with energy in Duke Energy’s contracts and, as such, related revenues are recognized as energy is generated and delivered as that pattern is consistent with Duke Energy’s performance. Commercial Renewables recognizes revenue based on the energy generated and billed for the period, generally one month, at contractual rates (including estimated billings) according to the invoice practical expedient. Amounts are typically due within 30 days of invoice. Other The remainder of Duke Energy’s operations is presented as Other, which does not include material revenues from contracts with customers. Disaggregated Revenues For the Electric and Gas segments, revenue by customer class is most meaningful to Duke Energy as each respective customer class collectively represents unique customer expectations of service, generally has different energy and demand requirements, and operates under tailored, regulatory approved pricing structures. Additionally, each customer class is impacted differently by weather and a variety of economic factors including the level of population growth, economic investment, employment levels, and regulatory activities in each of Duke Energy’s jurisdictions. As such, analyzing revenues disaggregated by customer class allows Duke Energy to understand the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. For the Commercial Renewables segment, the majority of revenues from contracts with customers are from selling all of the unit-contingent output at contractually defined pricing under long-term PPAs with consistent expectations regarding the timing and certainty of cash flows. Disaggregated revenues are presented as follows: Three Months Ended March 31, 2018 Duke Duke Duke Duke Duke (in millions) Duke Energy Progress Energy Energy Energy Energy By market or type of customer Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Electric Utilities and Infrastructure Residential $ 2,350 $ 781 $ 1,112 $ 516 $ 595 $ 180 $ 278 $ — General 1,375 472 631 299 333 96 178 — Industrial 664 255 208 145 62 30 173 — Wholesale 633 119 446 397 50 — 68 — Other revenues 139 67 129 85 43 14 17 — Total Electric Utilities and Infrastructure revenue from contracts with customers $ 5,161 $ 1,694 $ 2,526 $ 1,442 $ 1,083 $ 320 $ 714 $ — Gas Utilities and Infrastructure Residential $ 413 $ — $ — $ — $ — $ 111 $ — $ 302 Commercial 201 — — — — 49 — 152 Industrial 48 — — — — 7 — 41 Power Generation — — — — — — — 13 Other revenues 55 — — — — 6 — 49 Total Gas Utilities and Infrastructure revenue from contracts with customers $ 717 $ — $ — $ — $ — $ 173 $ — $ 557 Commercial Renewables Revenue from contracts with customers $ 33 $ — $ — $ — $ — $ — $ — $ — Other Revenue from contracts with customers $ 17 $ — $ — $ — $ — $ 14 $ — $ — Total revenue from contracts with customers $ 5,928 $ 1,694 $ 2,526 $ 1,442 $ 1,083 $ 507 $ 714 $ 557 Other revenue sources (a) $ 207 $ 69 $ 50 $ 18 $ 32 $ 17 $ 17 $ (4 ) Total revenues $ 6,135 $ 1,763 $ 2,576 $ 1,460 $ 1,115 $ 524 $ 731 $ 553 (a) Other revenue sources include revenues from leases, derivatives and alternative revenue programs that are not considered revenues from contracts with customers. Piedmont has regulatory mechanisms that periodically provide rate adjustments to refund any over-collection or to recover any under-collection of margin. IMPACT OF WEATHER AND THE TIMING OF BILLING PERIODS Revenues and costs are influenced by seasonal weather patterns. Peak sales of electricity occur during the summer and winter months , which results in higher revenue and cash flows during these periods. By contrast, lower sales of electricity occur during the spring and fall, allowing for scheduled plant maintenance. Residential and general service customers are more impacted by weather than industrial customers. Estimated weather impacts are based on actual current period weather compared to normal weather conditions. Normal weather conditions are defined as the long-term average of actual historical weather conditions. Heating-degree days measure the variation in weather based on the extent the average daily temperature falls below a base temperature. Cooling-degree days measure the variation in weather based on the extent the average daily temperature rises above the base temperature. Each degree of temperature below the base temperature counts as one heating-degree day and each degree of temperature above the base temperature counts as one cooling-degree day. The estimated impact of weather on earnings for Electric Utilities and Infrastructure is based on the temperature variances from a normal condition and customers' historic usage patterns. The methodology used to estimate the impact of weather does not consider all variables that may impact customer response to weather conditions, such as humidity in the summer or wind chill in the winter. The precision of this estimate may also be impacted by applying long-term weather trends to shorter-term periods. Gas Utilities and Infrastructure's costs and revenues are influenced by seasonal patterns due to peak natural gas sales occurring during the winter months as a result of space heating requirements. Residential customers are the most impacted by weather. There are certain regulatory mechanisms for the North Carolina, South Carolina , Tennessee, and Ohio service territories that normalize the margins collected from certain customer classes during the winter. In North Carolina, rate design provides protection from both weather and other usage variations such as conservation, while South Carolina and Tennessee revenues are adjusted solely based on weather. Ohio primarily employs a fixed charge each month regardless of the season and usage. UNBILLED REVENUE Unbilled revenues are recognized by applying customer billing rates to the estimated volumes of energy or natural gas delivered but not yet billed. Unbilled revenues can vary significantly from period to period as a result of seasonality, weather, customer usage patterns, customer mix, average price in effect for customer classes, timing of rendering customer bills and meter reading schedules, and the impact of weather normalization or margin decoupling mechanisms. Unbilled revenues are included within Receivables and Receivables of variable interest entities (VIEs) on the Condensed Consolidated Balance Sheets as shown in the following table. (in millions) March 31, 2018 December 31, 2017 Duke Energy $ 823 $ 944 Duke Energy Carolinas 310 342 Progress Energy 237 228 Duke Energy Progress 167 143 Duke Energy Florida 70 85 Duke Energy Ohio 2 4 Duke Energy Indiana 24 21 Piedmont 45 86 Additionally, Duke Energy Ohio and Duke Energy Indiana sell, on a revolving basis, nearly all of their retail accounts receivable, including receivables for unbilled revenues, to an affiliate, CRC and accounts for the transfers of receivables as sales. Accordingly, the receivables sold are not reflected on the Condensed Consolidated Balance Sheets of Duke Energy Ohio and Duke Energy Indiana. See Note 11 for further information. These receivables for unbilled revenues are shown in the table below. (in millions) March 31, 2018 December 31, 2017 Duke Energy Ohio $ 67 $ 104 Duke Energy Indiana 108 132

Common Stock

Common Stock	3 Months Ended
	Mar. 31, 2018
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 March 31, (in millions, except per-share amounts) 2018 2017 Income from continuing operations attributable to Duke Energy common stockholders excluding impact of participating securities $ 619 $ 715 Weighted average shares outstanding – basic 701 700 Weighted average shares outstanding – diluted 701 700 Earnings per share from continuing operations attributable to Duke Energy common stockholders Basic $ 0.88 $ 1.02 Diluted $ 0.88 $ 1.02 Potentially dilutive items excluded from the calculation (a) 2 2 Dividends declared per common share $ 0.89 $ 0.855 (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 On February 20, 2018, Duke Energy filed a prospectus supplement and executed an Equity Distribution Agreement (the EDA) under which it may sell up to $1 billion of its common stock through an at-the-market offering program, including an equity forward sales component. The EDA was entered into with Wells Fargo Securities, LLC, Citigroup Global Markets Inc., and J.P. Morgan Securities LLC (the Agents). Under the terms of the EDA, Duke Energy may issue and sell, through either of the Agents, shares of common stock through September 23, 2019. There were no transactions under the EDA during the three months ended March 31, 2018 . Separately, in March 2018, Duke Energy marketed an equity offering of 21.3 million shares of common stock through an Underwriting Agreement with Credit Suisse Securities (USA) LLC, J.P. Morgan Securities LLC, Barclays Capital Inc. and Goldman Sachs & Co. LLC, as representatives of several underwriters, Credit Suisse Capital LLC and J.P. Morgan Securities LLC as Forward Sellers, and Credit Suisse Capital LLC and JPMorgan Chase National Bank Associate, acting as forward purchasers. In connection with the offering, Duke Energy entered into equity forward sale agreements with Credit Suisse Securities (USA) LLC as Agent for Credit Suisse Capital LLC and J.P. Morgan Chase Bank, National Association. No amounts have or will be recorded in Duke Energy's Condensed Consolidated Financial Statements with respect to the equity offering until settlements of the Equity Forwards occur, which is expected by December 31, 2018. The Equity Forwards require Duke Energy to either physically settle the transactions by issuing 21.3 million shares in exchange for net proceeds at the then-applicable forward sale price specified by the agreements (initially $74.07 per share), or net settle in whole or in part through the delivery or receipt of cash or shares. If Duke Energy had elected to net share settle the contract as of March 31, 2018, Duke Energy would have been required to deliver 0.9 million shares. The initial forward sale price will be subject to adjustment on a daily basis based on a floating interest rate factor and will decrease by other fixed amounts specified in the relevant forward sale agreement. Until settlement of the Equity Forwards, earnings per share dilution resulting from the agreements, if any, will be determined under the treasury stock method. Share dilution occurs when the average market price of Duke Energy's stock is higher than the average forward sales price.
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 March 31, (in millions, except per-share amounts) 2018 2017 Income from continuing operations attributable to Duke Energy common stockholders excluding impact of participating securities $ 619 $ 715 Weighted average shares outstanding – basic 701 700 Weighted average shares outstanding – diluted 701 700 Earnings per share from continuing operations attributable to Duke Energy common stockholders Basic $ 0.88 $ 1.02 Diluted $ 0.88 $ 1.02 Potentially dilutive items excluded from the calculation (a) 2 2 Dividends declared per common share $ 0.89 $ 0.855 (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 On February 20, 2018, Duke Energy filed a prospectus supplement and executed an Equity Distribution Agreement (the EDA) under which it may sell up to $1 billion of its common stock through an at-the-market offering program, including an equity forward sales component. The EDA was entered into with Wells Fargo Securities, LLC, Citigroup Global Markets Inc., and J.P. Morgan Securities LLC (the Agents). Under the terms of the EDA, Duke Energy may issue and sell, through either of the Agents, shares of common stock through September 23, 2019. There were no transactions under the EDA during the three months ended March 31, 2018 . Separately, in March 2018, Duke Energy marketed an equity offering of 21.3 million shares of common stock through an Underwriting Agreement with Credit Suisse Securities (USA) LLC, J.P. Morgan Securities LLC, Barclays Capital Inc. and Goldman Sachs & Co. LLC, as representatives of several underwriters, Credit Suisse Capital LLC and J.P. Morgan Securities LLC as Forward Sellers, and Credit Suisse Capital LLC and JPMorgan Chase National Bank Associate, acting as forward purchasers. In connection with the offering, Duke Energy entered into equity forward sale agreements with Credit Suisse Securities (USA) LLC as Agent for Credit Suisse Capital LLC and J.P. Morgan Chase Bank, National Association. No amounts have or will be recorded in Duke Energy's Condensed Consolidated Financial Statements with respect to the equity offering until settlements of the Equity Forwards occur, which is expected by December 31, 2018. The Equity Forwards require Duke Energy to either physically settle the transactions by issuing 21.3 million shares in exchange for net proceeds at the then-applicable forward sale price specified by the agreements (initially $74.07 per share), or net settle in whole or in part through the delivery or receipt of cash or shares. If Duke Energy had elected to net share settle the contract as of March 31, 2018, Duke Energy would have been required to deliver 0.9 million shares. The initial forward sale price will be subject to adjustment on a daily basis based on a floating interest rate factor and will decrease by other fixed amounts specified in the relevant forward sale agreement. Until settlement of the Equity Forwards, earnings per share dilution resulting from the agreements, if any, will be determined under the treasury stock method. Share dilution occurs when the average market price of Duke Energy's stock is higher than the average forward sales price.

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2018
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 March 31, (in millions) 2018 2017 Restricted stock unit awards $ 10 $ 8 Performance awards 7 7 Pretax stock-based compensation cost $ 17 $ 15 Tax benefit associated with stock-based compensation expense $ 4 $ 5 Stock-based compensation costs capitalized 1 1

Employee Benefit Plans

Employee Benefit Plans	3 Months Ended
	Mar. 31, 2018
Retirement Benefits [Abstract]
Employee Benefit Plans	EMPLOYEE BENEFIT PLANS DEFINED BENEFIT RETIREMENT PLANS Duke Energy maintains, and the Subsidiary Registrants participate in, qualified and non-qualified, non-contributory defined benefit retirement plans. Duke Energy’s policy is to fund amounts on an actuarial basis to provide assets sufficient to meet benefit payments to be paid to plan participants. The following table includes information related to the Duke Energy Registrants' contributions to its qualified defined benefit pension plans. Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Total anticipated 2018 contributions $ 148 $ 46 $ 45 $ 25 $ 20 $ — $ 8 $ 7 Contributions made during the three months ended March 31, 2018 141 46 45 25 20 — 8 — Remaining estimated 2018 contributions $ 7 $ — $ — $ — $ — $ — $ — $ 7 Duke Energy did not make any contributions to its qualified defined benefit pension plans during the three months ended March 31, 2017 . Duke Energy uses a December 31 measurement date for its defined benefit retirement plan assets and obligations. Components of Net Periodic Benefit Costs The tables below present total net periodic benefit costs prior to capitalization of amounts reflected as Net property, plant and equipment on the Condensed Consolidated Balance Sheets. Only the service cost component of net periodic benefit costs is eligible to be capitalized. The remaining non-capitalized portions of net periodic benefit costs are classified as either: (1) service cost, which is recorded in Operations, maintenance and other on the Condensed Consolidated Statements of Operations; or as (2) components of non-service cost, which is recorded in Other income and expenses, net on the Condensed Consolidated Statements of Operations. See Note 1 for further information on impacts of the retirement benefits accounting standard adopted by Duke Energy on January 1, 2018. Pension and other post-retirement benefit costs presented in the tables below for the Subsidiary Registrants are amounts allocated from Duke Energy for the employees of the respective Subsidiary Registrants. The Condensed Consolidated Statements of Operations of the Subsidiary Registrants also include allocated net periodic benefit costs for their proportionate share of pension and post-retirement benefit costs related to employees of the Duke Energy shared services affiliate. However, in the tables below these amounts are only presented in the Duke Energy column. For additional information on the corporate governance and shared service expenses allocated from the Duke Energy shared service affiliate, see Note 7 . QUALIFIED PENSION PLANS The following tables include the components of net periodic pension costs for qualified pension plans. Three Months Ended March 31, 2018 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Service cost $ 45 $ 15 $ 13 $ 7 $ 5 $ 1 $ 2 $ 2 Interest cost on projected benefit obligation 75 18 24 11 13 5 6 3 Expected return on plan assets (140 ) (37 ) (45 ) (21 ) (23 ) (7 ) (10 ) (6 ) Amortization of actuarial loss 33 7 11 5 6 1 2 3 Amortization of prior service credit (8 ) (2 ) (1 ) — — — — (3 ) Net periodic pension costs $ 5 $ 1 $ 2 $ 2 $ 1 $ — $ — $ (1 ) Three Months Ended March 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Service cost $ 40 $ 12 $ 12 $ 6 $ 5 $ 1 $ 2 $ 3 Interest cost on projected benefit obligation 82 20 25 12 13 5 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 $ 2 NON-QUALIFIED PENSION PLANS Net periodic pension costs for non-qualified pension plans were not material for the three months ended March 31, 2018 and 2017 . 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 March 31, 2018 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Service cost $ 1 $ — $ — $ — $ — $ — $ — $ — Interest cost on accumulated post-retirement benefit obligation 7 2 4 1 1 — 1 — Expected return on plan assets (2 ) (2 ) — — — — — — Amortization of actuarial loss 1 — — — — — 1 — Amortization of prior service credit (5 ) (1 ) (2 ) — (1 ) — — — Net periodic other post-retirement benefit costs $ 2 $ (1 ) $ 2 $ 1 $ — $ — $ 2 $ — Three Months Ended March 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Service cost $ 1 $ — $ — $ — $ — $ — $ — $ — Interest cost on accumulated post-retirement benefit obligation 9 2 4 2 2 — — — Expected return on plan assets (3 ) (2 ) — — — — — — Amortization of actuarial loss (gain) 2 (1 ) 5 3 2 — — — Amortization of prior service credit (29 ) (2 ) (21 ) (14 ) (8 ) — — — Net periodic other post-retirement benefit costs $ (20 ) $ (3 ) $ (12 ) $ (9 ) $ (4 ) $ — $ — $ — EMPLOYEE SAVINGS PLAN Duke Energy sponsors, and the Subsidiary Registrants participate in, an employee savings plan that covers substantially all employees. The following table includes employer contributions made by Duke Energy and expensed by the Subsidiary Registrants. Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Three Months Ended March 31, 2018 $ 70 $ 23 $ 19 $ 13 $ 6 $ 1 $ 3 $ 4 2017 65 22 18 13 5 1 3 2

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	INCOME TAXES Tax Act On December 22, 2017, President Trump signed the Tax Act into law. Among other provisions, the Tax Act lowered the corporate federal income tax rate from 35 percent to 21 percent, limits interest deductions outside of regulated utility operations, requires the normalization of excess deferred taxes associated with property under the average rate assumption method as a prerequisite to qualifying for accelerated depreciation and repealed the federal manufacturing deduction. The Tax Act also repealed the corporate alternative minimum tax (AMT) and stipulates a refund of 50 percent of remaining AMT credit carryforwards (to the extent the credits exceed regular tax for the year) for tax years 2018, 2019 and 2020 with all remaining AMT credits to be refunded in tax year 2021. At this time, AMT credits that are treated as refundable under the Tax Act are among the certain refundable tax credits that are subject to sequestration. During the three months ended March 31, 2018, the company has revised the December 31, 2017, estimate of the income tax effects of the Tax Act by recording a $76 million valuation allowance against these AMT credits based on additional interpretative guidance from the Internal Revenue Service related to the Tax Act. See Note 22 to the Consolidated Financial Statements in the Annual Report on Form 10-K/A for the year ended December 31, 2017 , for information on the U.S. Securities and Exchange Commission staff's guidance on accounting for the Tax Act (Staff Accounting Bulletin No. 118, Income Tax Accounting Implications of the Tax Cuts and Jobs Act). 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 March 31, 2018 2017 Duke Energy 22.5 % 32.4 % Duke Energy Carolinas 22.0 % 35.4 % Progress Energy 13.2 % 34.1 % Duke Energy Progress 14.1 % 34.1 % Duke Energy Florida 16.3 % 36.6 % Duke Energy Ohio 32.4 % 35.4 % Duke Energy Indiana 25.9 % 39.3 % Piedmont 24.1 % 37.9 % The decrease in the effective tax rate (ETR) for Duke Energy and the Subsidiary Registrants for the three months ended March 31, 2018 , is primarily due to the lower statutory federal corporate tax rate under the Tax Act partially offset by a valuation allowance against AMT credits discussed above. The decrease in the ETR for Duke Energy Carolinas for the three months ended March 31, 2018 , is primarily due to the lower statutory federal corporate tax rate under the Tax Act. The decrease in the ETR for Progress Energy for the three months ended March 31, 2018 , is primarily due to the lower statutory federal corporate tax rate under the Tax Act and the amortization of federal and state excess deferred taxes. The decrease in the ETR for Duke Energy Progress for the three months ended March 31, 2018 , is primarily due to the lower statutory federal corporate tax rate under the Tax Act and the amortization of state excess deferred taxes. The decrease in the ETR for Duke Energy Florida for the three months ended March 31, 2018 , is primarily due to the lower statutory federal corporate tax rate under the Tax Act and the amortization of federal excess deferred taxes. The decrease in the ETR for Duke Energy Ohio for the three months ended March 31, 2018 , is primarily due to the lower statutory federal corporate tax rate under the Tax Act partially offset by tax levelization related to federal excess deferred taxes on a pretax loss for the three months ended March 31, 2018. The decrease in the ETR for Duke Energy Indiana for the three months ended March 31, 2018 , is primarily due to the lower statutory federal corporate tax rate under the Tax Act. The decrease in the ETR for Piedmont for the three months ended March 31, 2018 , is primarily due to the lower statutory federal corporate tax rate under the Tax Act.

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2018
Subsequent Events [Abstract]
Subsequent Events	SUBSEQUENT EVENTS For information on subsequent events related to regulatory matters, commitments and contingencies, debt and credit facilities and variable interest entities see Notes 3, 4, 5 and 11, respectively.

Organization and Basis of Pre25

Organization and Basis of Presentation (Policy)	3 Months Ended
	Mar. 31, 2018
Policy Text Block [Line Items]
Basis of Presentation	BASIS OF PRESENTATION These Condensed Consolidated Financial Statements have been prepared in accordance with generally accepted accounting principles (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/A for the year ended December 31, 2017 . The information in these combined notes relates to each of the Duke Energy Registrants as noted in the Index to Combined Notes to Condensed Consolidated Financial Statements. However, none of the registrants make any representations as to information related solely to Duke Energy or the subsidiaries of Duke Energy other than itself. These Condensed Consolidated Financial Statements, in the opinion of the respective companies’ management, reflect all normal recurring adjustments necessary to fairly present the financial position and results of operations of each of the Duke Energy Registrants. Amounts reported in Duke Energy’s interim Condensed Consolidated Statements of Operations and each of the Subsidiary Registrants’ interim Condensed Consolidated Statements of Operations and Comprehensive Income are not necessarily indicative of amounts expected for the respective annual periods due to effects of seasonal temperature variations on energy consumption, regulatory rulings, timing of maintenance on electric generating units, changes in mark-to-market valuations, changing commodity prices and other factors.
Consolidation	These Condensed Consolidated Financial Statements include, after eliminating intercompany transactions and balances, the accounts of the Duke Energy Registrants and subsidiaries where the respective Duke Energy Registrants have control. These Condensed Consolidated Financial Statements also reflect the Duke Energy Registrants’ proportionate share of certain jointly owned generation and transmission facilities.
Use of Estimates	In preparing financial statements that conform to GAAP, management must make estimates and assumptions that affect the reported amounts of assets and liabilities, the reported amounts of revenues and expenses, and the disclosure of contingent assets and liabilities at the date of the financial statements. Actual results could differ from those estimates.
Cash and Cash Equivalents, Restricted Cash and Cash Equivalents	CASH, CASH EQUIVALENTS AND RESTRICTED CASH Duke Energy, Progress Energy and Duke Energy Florida have restricted cash balances related primarily to collateral assets, escrow deposits and variable interest entities (VIEs). See Note 11 for additional information. Restricted cash amounts are included in Other within Current Assets and Other Noncurrent Assets.
Inventory	INVENTORY Inventory is used for operations and is recorded primarily using the average cost method. Inventory related to regulated operations is valued at historical cost. Inventory related to nonregulated operations is valued at the lower of cost or market. Materials and supplies are recorded as inventory when purchased and subsequently charged to expense or capitalized to property, plant and equipment when installed. Inventory, including excess or obsolete inventory, is written-down to the lower of cost or market value. Once inventory has been written-down, it creates a new cost basis for the inventory that is not subsequently written-up.
New Accounting Standards	NEW ACCOUNTING STANDARDS The new accounting standards adopted for 2018 and 2017 had no material impact on the presentation or results of operations, cash flows or financial position of the Duke Energy Registrants. While immaterial, adoption of the following accounting standards had the most significant impact on the Duke Energy results of operations, cash flows and financial position for the three months ended March 31, 2018 . Revenue from Contracts with Customers. In May 2014, the Financial Accounting Standards Board (FASB) issued revised accounting guidance for revenue recognition from contracts with customers. The core principle of this guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration expected in exchange for those goods or services. The amendments also required disclosure of sufficient information to allow users to understand the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. The majority of Duke Energy’s revenue is in scope of the new guidance. Other revenue arrangements, such as alternative revenue programs and certain purchase power agreements (PPAs) and lighting tariffs accounted for as leases, are excluded from the scope of this guidance and, therefore, are accounted for and evaluated for separate presentation and disclosure under other relevant accounting guidance. Duke Energy elected the modified retrospective method of adoption effective January 1, 2018. Under the modified retrospective method of adoption, prior year reported results are not restated. Adoption of this standard did not result in a material change in the timing or pattern of revenue recognition and a cumulative-effect adjustment was not recorded at January 1, 2018. Duke Energy utilized certain practical expedients including applying this guidance to open contracts at the date of adoption, expensing costs to obtain a contract where the amortization period of the asset would have been one year or less, ignoring the effects of a significant financing when the period between transfer of the good or service and payment is one year or less and recognizing revenues for certain contracts under the invoice practical expedient, which allows revenue recognition to be consistent with invoiced amounts (including estimated billings) provided certain criteria are met, including consideration of whether the invoiced amounts reasonably represent the value provided to customers. In preparation for adoption, Duke Energy identified material revenue streams and reviewed representative contracts and tariffs, including those associated with certain long-term customer contracts such as wholesale contracts, PPAs, and other customer arrangements. Duke Energy also monitored the activities of the power and utilities industry revenue recognition task force and has reviewed published positions on specific industry issues to evaluate the impact, if any, on Duke Energy’s specific contracts and conclusions. Duke Energy applied the available practical expedient to portfolios of tariffs and contracts with similar characteristics. The vast majority of sales, including energy provided to retail customers, are from tariff offerings that provide natural gas or electricity without a defined contractual term ("at-will"). In most circumstances, revenue from contracts with customers is equivalent to the electricity or natural gas supplied and billed in that period (including estimated billings). As such, adoption of the new rules did not result in a shift in the timing or pattern of revenue recognition for such sales. While there have been changes to the captions and descriptions of revenues in Duke Energy’s financial statements, the most significant impact as a result of adopting the standard are additional disclosures around the nature, amount, timing, and uncertainty of revenues and cash flows arising from contracts with customers. See Note 12 for further information. Financial Instruments Classification and Measurement. In January 2018, Duke Energy adopted FASB guidance, which revised the classification and measurement of certain financial instruments. The adopted guidance changes the presentation of realized and unrealized gains and losses in certain equity securities that were previously recorded in accumulated other comprehensive income (AOCI). These gains and losses are now recorded in net income. An entity's equity investments that are accounted for under the equity method of accounting are not included within the scope of the new guidance. This guidance had a minimal impact on the Duke Energy Registrant's Condensed Consolidated Statements of Operations and Comprehensive Income as changes in the fair value of most of the Duke Energy Registrants' equity securities are deferred as regulatory assets or liabilities pursuant to accounting guidance for regulated operations. The resulting adjustment of unrealized gains and losses in AOCI to retained earnings was immaterial. The primary impact to Duke Energy as a result of implementing this guidance is adding disclosure requirements to present separately the financial assets and financial liabilities by measurement category and form of financial asset. See Notes 9 and 10 for further information. Statement of Cash Flows. In November 2016, the FASB issued revised accounting guidance to reduce diversity in practice for the presentation and classification of restricted cash on the Condensed Consolidated Statements of Cash Flows. Under the updated guidance, restricted cash and restricted cash equivalents are included within beginning-of-period and end-of-period cash and cash equivalents on the Condensed Consolidated Statements of Cash Flows. Duke Energy adopted this guidance on January 1, 2018. The guidance has been applied using a retrospective transition method to each period presented. The adoption by Duke Energy of the revised guidance resulted in a change to the amount of Cash, cash equivalents and restricted cash explained when reconciling the beginning-of-period and end-of-period total amounts shown on the Condensed Consolidated Statements of Cash Flows. In addition, a reconciliation has been provided of Cash, cash equivalents and restricted cash reported within the Condensed Consolidated Balance Sheets that sums to the total of the same such amounts in the Condensed Consolidated Statements of Cash Flows. Prior to adoption, the Duke Energy Registrants reflected changes in noncurrent restricted cash within Cash Flows from Investing Activities and changes in current restricted cash within Cash Flows from Operating Activities on the Condensed Consolidated Statement of Cash Flows. In August 2016, the FASB issued accounting guidance addressing diversity in practice for eight separate cash flow issues. The guidance requires entities to classify distributions received from equity method investees using either the cumulative earnings approach or the nature of the distribution approach. Duke Energy adopted this guidance on January 1, 2018, and has elected the nature of distribution approach. Duke Energy will categorize all distributions received based on legal documentation describing the nature of the activities generating the distribution. Cash inflows resulting in a return on investment (surplus) will be reflected in Cash Flows from Operating Activities on the Condensed Consolidated Statements of Cash Flows, whereas cash inflows resulting in a return of investment (capital) will be reflected in Cash Flows from Investing Activities on the Condensed Consolidated Statements of Cash Flows. The guidance has been applied using the retrospective transition method to each period presented. There are no changes to the Condensed Consolidated Statements of Cash Flows for the periods presented as a result of this accounting change. Retirement Benefits. In March 2017, the FASB issued revised accounting guidance for the presentation of net periodic costs related to benefit plans. Previous guidance required the aggregation of all the components of net periodic costs on the Condensed Consolidated Statement of Operations and did not require the disclosure of the location of net periodic costs on the Condensed Consolidated Statement of Operations. Under the amended guidance, the service cost component of net periodic costs is included within Operating Income within the same line as other compensation expenses. All other components of net periodic costs are outside of Operating Income. In addition, the updated guidance permits only the service cost component of net periodic costs to be capitalized to Inventory or Property, Plant and Equipment. This represents a change from previous guidance, which permitted all components of net periodic costs to be eligible for capitalization. Duke Energy adopted this guidance on January 1, 2018. Under previous guidance, Duke Energy presented the total non-capitalized net periodic costs within Operation, maintenance and other on the Condensed Consolidated Statement of Operations. The adoption of this guidance resulted in a retrospective change to reclassify the presentation of the non-service cost (benefit) components of net periodic costs to Other income and expenses. Duke Energy utilized the practical expedient for retrospective presentation. The change in components of net periodic costs eligible for capitalization is applicable prospectively. Since Duke Energy’s service cost component is greater than the total net periodic costs, the change results in increased capitalization of net periodic costs, higher Operation, maintenance and other and higher Other income and expenses. The resulting prospective impact to Duke Energy is an immaterial increase in Net Income. See Note 15 for further information. For Duke Energy, the retrospective change resulted in higher Operation, maintenance and other and higher Other income and expenses, net, of $156 million , $131 million and $96 million for the years ended December 31, 2017, 2016 and 2015, respectively. There was no change to Net Income for these prior periods. The following new Accounting Standards Updates (ASUs) have been issued, but have not yet been adopted by Duke Energy, as of March 31, 2018 . Leases. In February 2016, the FASB issued revised accounting guidance for leases. The core principle of this guidance is that a lessee should recognize the assets and liabilities that arise from leases on the balance sheet. For Duke Energy, this guidance is effective for interim and annual periods beginning January 1, 2019. The guidance will be applied using a modified retrospective approach. Upon adoption, Duke Energy expects to elect certain of the practical expedients upon adoption: Practical Expedient Description Package of transition practical expedients (for leases commenced prior to adoption date and must be adopted as a package) Do not need to reassess whether any expired or existing contracts are/or contain leases, do not need to reassess the lease classification for any expired or existing leases and do not need to reassess initial direct costs for any existing leases. Short-term lease expedient (elect by class of underlying asset) Elect as an accounting policy to not apply the recognition requirements to short-term leases by asset class. Lease and non-lease components (elect by class of underlying asset) Duke Energy will likely elect as an accounting policy to not separate non-lease components from lease components and instead account for each lease and associated non-lease component as a single lease component. Hindsight expedient (when determining lease term) Elect to use hindsight to determine the lease term. Easement expedient Elect to carry forward current accounting treatment for existing easements. Duke Energy is currently evaluating the financial statement impact of adopting this standard and is continuing to monitor industry implementation issues, including pipeline laterals, pole attachments and renewable PPAs. Other than an expected increase in assets and liabilities, the ultimate impact of the new standard has not yet been determined. Significant system enhancements, including additional processes and controls, will be required to facilitate the identification, tracking and reporting of potential leases based upon requirements of the new lease standard. Duke Energy has begun the implementation of a third-party software tool to help with the adoption and ongoing accounting under the new standard.
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 securities within the Investment Trusts are considered OTTIs and are recognized immediately and deferred to regulatory accounts where appropriate.
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.
Revenue	certain excise taxes and franchise fees levied by state or local governments are required to be paid even if not collected from the customer. These taxes are recognized on a gross basis as part of revenues. Duke Energy elects to account for all other taxes net of revenues. Duke Energy recognizes revenue consistent with amounts billed under tariff offerings or at contractually agreed upon rates based on actual physical delivery of electric or natural gas service, including estimated volumes delivered when billings have not yet occurred. Additionally, Duke Energy Ohio and Duke Energy Indiana sell, on a revolving basis, nearly all of their retail accounts receivable, including receivables for unbilled revenues, to an affiliate, CRC and accounts for the transfers of receivables as sales. Accordingly, the receivables sold are not reflected on the Condensed Consolidated Balance Sheets of Duke Energy Ohio and Duke Energy Indiana. UNBILLED REVENUE Unbilled revenues are recognized by applying customer billing rates to the estimated volumes of energy or natural gas delivered but not yet billed. Unbilled revenues can vary significantly from period to period as a result of seasonality, weather, customer usage patterns, customer mix, average price in effect for customer classes, timing of rendering customer bills and meter reading schedules, and the impact of weather normalization or margin decoupling mechanisms.

Organization and Basis of Pre26

Organization and Basis of Presentation (Tables)	3 Months Ended
	Mar. 31, 2018
Organization And Basis Of Presentation [Line Items]
Schedule of Cash, Cash Equivalents and Restricted Cash	The following table presents the components of Cash, cash equivalents and restricted cash included in the Condensed Consolidated Balance Sheets. March 31, 2018 December 31, 2017 Duke Duke Duke Progress Energy Duke Progress Energy Energy Energy Florida Energy Energy Florida Current Assets Cash and cash equivalents $ 421 $ 20 $ 6 $ 358 $ 40 $ 13 Other 149 13 13 138 40 40 Other Noncurrent Assets Other 9 6 — 9 7 — Total Cash, cash equivalents and restricted cash $ 579 $ 39 $ 19 $ 505 $ 87 $ 53
Schedule of Utility Inventory	The components of inventory are presented in the tables below. March 31, 2018 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Materials and supplies $ 2,293 $ 763 $ 1,095 $ 767 $ 329 $ 82 $ 310 $ 1 Coal 551 176 221 125 96 13 141 — Natural gas, oil and other fuel 305 41 221 110 110 13 2 28 Total inventory $ 3,149 $ 980 $ 1,537 $ 1,002 $ 535 $ 108 $ 453 $ 29 December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Materials and supplies $ 2,293 $ 744 $ 1,118 $ 774 $ 343 $ 82 $ 309 $ 2 Coal 603 192 255 139 116 17 139 — Natural gas, oil and other fuel 354 35 219 104 115 34 2 64 Total inventory $ 3,250 $ 971 $ 1,592 $ 1,017 $ 574 $ 133 $ 450 $ 66
Schedule of Excise Taxes	Excise taxes accounted for on a gross basis within both Operating revenues and Property and other taxes on the Condensed Consolidated Statements of Operations were as follows. Three Months Ended March 31, (in millions) 2018 2017 Duke Energy $ 99 $ 91 Duke Energy Carolinas 8 9 Progress Energy 54 46 Duke Energy Progress 5 5 Duke Energy Florida 49 41 Duke Energy Ohio 30 28 Duke Energy Indiana 6 7 Piedmont 1 1

Business Segments (Tables)

Business Segments (Tables)	3 Months Ended
	Mar. 31, 2018
Segment Reporting Information [Line Items]
Business Segment Data	Business segment information is presented in the following tables. Segment assets presented exclude intercompany assets. Three Months Ended March 31, 2018 Electric Gas Total Utilities and Utilities and Commercial Reportable (in millions) Infrastructure Infrastructure Renewables Segments Other Eliminations Consolidated Unaffiliated revenues $ 5,315 $ 702 $ 101 $ 6,118 $ 17 $ — $ 6,135 Intersegment revenues 8 25 — 33 18 (51 ) — Total revenues $ 5,323 $ 727 $ 101 $ 6,151 $ 35 $ (51 ) $ 6,135 Segment income (loss) (a)(b)(c) $ 750 $ 116 $ 20 $ 886 $ (266 ) $ — $ 620 Add back noncontrolling interests 2 Net income $ 622 Segment assets $ 120,021 $ 11,396 $ 4,265 $ 135,682 $ 2,682 $ 177 $ 138,541 Three Months Ended March 31, 2017 Electric Gas Total Utilities and Utilities and Commercial Reportable (in millions) Infrastructure Infrastructure Renewables Segments Other Eliminations Consolidated Unaffiliated revenues $ 4,939 $ 648 $ 128 $ 5,715 $ 14 $ — $ 5,729 Intersegment revenues 8 22 — 30 19 (49 ) — Total revenues $ 4,947 $ 670 $ 128 $ 5,745 $ 33 $ (49 ) $ 5,729 Segment income (loss) $ 635 $ 133 $ 25 $ 793 $ (77 ) $ — $ 716 Add back noncontrolling interests 1 Net income $ 717 (a) Electric Utilities and Infrastructure includes regulatory charges related to NCUC orders and settlements. See Note 3 for additional information. (b) Gas Utilities and Infrastructure includes an impairment of the investment in Constitution Pipeline Company, LLC (Constitution). See Note 3 for additional information. (c) Other includes the loss on the sale of the retired Beckjord generating station (Beckjord) described below and a valuation allowance recorded against the alternative minimum tax credits subject to sequestration. See Note 16 for additional information on the valuation allowance.
Duke Energy Ohio [Member]
Segment Reporting Information [Line Items]
Business Segment Data	Three Months Ended March 31, 2018 Electric Gas Total Utilities and Utilities and Reportable (in millions) Infrastructure Infrastructure Segments Other Eliminations Consolidated Total revenues $ 336 $ 174 $ 510 $ 14 $ — $ 524 Segment income (loss)/Net income (loss) (a) 33 34 67 (92 ) — (25 ) Segment assets $ 5,165 $ 2,709 $ 7,874 $ 25 $ (3 ) $ 7,896 Three Months Ended March 31, 2017 Electric Gas Total Utilities and Utilities and Reportable (in millions) Infrastructure Infrastructure Segments Other Consolidated Total revenues $ 337 $ 170 $ 507 $ 11 $ 518 Segment income (loss)/Net income (loss) 24 26 50 (8 ) 42 (a) Other includes the loss on the sale of the retired Beckjord generating station described above.

Regulatory Matters (Tables)

Regulatory Matters (Tables)	3 Months Ended
	Mar. 31, 2018
Regulated Operations [Abstract]
Schedule of Potential Plant Retirements	The table below contains the net carrying value of generating facilities planned for retirement or included in recent IRPs as evaluated for potential retirement due to a lack of requisite environmental control equipment. Dollar amounts in the table below are included in Net property, plant and equipment on the Condensed Consolidated Balance Sheets as of March 31, 2018 , and exclude capitalized asset retirement costs. Remaining Net Capacity Book Value (in MW) (in millions) Duke Energy Carolinas Allen Steam Station Units 1-3 (a) 585 $ 161 Progress Energy and Duke Energy Florida Crystal River Units 1 and 2 (b) 873 104 Duke Energy Indiana Gallagher Units 2 and 4 (c) 280 126 Total Duke Energy 1,738 $ 391 (a) Duke Energy Carolinas will retire Allen Steam Station Units 1 through 3 by December 31, 2024, as part of the resolution of a lawsuit involving alleged New Source Review violations. (b) Duke Energy Florida expects to retire these coal units by the end of 2018 to comply with environmental regulations. (c) Duke Energy Indiana committed to either retire or stop burning coal at Gallagher Units 2 and 4 by December 31, 2022, as part of the settlement of Edwardsport IGCC matters.

Commitments and Contingencies (

Commitments and Contingencies (Table)	3 Months Ended
	Mar. 31, 2018
Valuation and Qualifying Accounts Disclosure [Line Items]
Schedule of Additional Possible Losses in Excess of Recorded Environmental Reserves	Additional losses in excess of recorded reserves that could be incurred for the stages of investigation, remediation and monitoring for environmental sites that have been evaluated at this time are not material except as presented in the table below. (in millions) Duke Energy $ 57 Duke Energy Carolinas 19 Duke Energy Ohio 30 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. Three Months Ended March 31, 2018 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Balance at beginning of period $ 81 $ 10 $ 15 $ 3 $ 12 $ 47 $ 5 $ 2 Provisions/adjustments 4 1 3 1 1 — 1 — Cash reductions (5 ) — (2 ) (1 ) (1 ) (3 ) — — Balance at end of period $ 80 $ 11 $ 16 $ 3 $ 12 $ 44 $ 6 $ 2 Three Months Ended March 31, 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 6 1 — — 1 4 (1 ) 1 Cash reductions (6 ) — (1 ) — (1 ) (4 ) — — Balance at end of period $ 98 $ 11 $ 17 $ 3 $ 14 $ 59 $ 9 $ 2
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 related to the termination of an EPC contract discussed above. Reserves are classified on the Condensed Consolidated Balance Sheets in Other within Other Noncurrent Liabilities and Accounts payable and Other within Current Liabilities. The reasonably possible range of loss in excess of recorded reserves is not material, other than as described above. (in millions) March 31, 2018 December 31, 2017 Reserves for Legal Matters Duke Energy $ 74 $ 88 Duke Energy Carolinas 20 30 Progress Energy 51 55 Duke Energy Progress 10 13 Duke Energy Florida 24 24 Piedmont 2 2

Debt and Credit Facilities (Tab

Debt and Credit Facilities (Tables)	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Schedule of Long-term Debt Instruments	The following table summarizes significant debt issuances (in millions). Three Months Ended March 31, 2018 Duke Duke Maturity Interest Duke Energy Energy Issuance Date Date Rate Energy (Parent) Carolinas Unsecured Debt March 2018 (a) April 2025 3.950 % $ 250 $ 250 $ — First Mortgage Bonds March 2018 (b) March 2023 3.050 % 500 — 500 March 2018 (b) March 2048 3.950 % 500 — 500 Total issuances $ 1,250 $ 250 $ 1,000 (a) Debt issued to pay down short-term debt. (b) Debt issued to repay at maturity a $ 300 million first mortgage bond due April 2018, pay down intercompany short-term debt and for general corporate purposes. 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 March 31, 2018 Unsecured Debt Duke Energy (Parent) June 2018 6.250 % $ 250 Duke Energy (Parent) June 2018 2.100 % 500 Piedmont December 2018 2.821 % (b) 250 Progress Energy March 2019 7.050 % 450 First Mortgage Bonds Duke Energy Carolinas April 2018 5.100 % 300 Duke Energy Florida June 2018 5.650 % 500 Duke Energy Carolinas November 2018 7.000 % 500 Duke Energy Progress January 2019 5.300 % 600 Other (a) 601 Current maturities of long-term debt $ 3,951 (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. March 31, 2018 Duke Duke Duke Duke Duke Duke Duke Energy Energy Energy Energy Energy Energy (in millions) Energy (Parent) Carolinas Progress Florida Ohio Indiana Piedmont Facility size (a) $ 8,000 $ 2,650 $ 1,550 $ 1,250 $ 800 $ 450 $ 600 $ 700 Reduction to backstop issuances Commercial paper (b) (2,602 ) (1,281 ) (340 ) (464 ) — (140 ) (282 ) (95 ) Outstanding letters of credit (59 ) (50 ) (4 ) (2 ) (1 ) — — (2 ) Tax-exempt bonds (81 ) — — — — — (81 ) — Coal ash set-aside (500 ) — (250 ) (250 ) — — — — Available capacity under the Master Credit Facility $ 4,758 $ 1,319 $ 956 $ 534 $ 799 $ 310 $ 237 $ 603 (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.

Goodwill (Tables)

Goodwill (Tables)	3 Months Ended
	Mar. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill By Reportable Operating Segment	The following table presents the goodwill by reportable operating segment included on Duke Energy's Condensed Consolidated Balance Sheets at March 31, 2018 , and December 31, 2017 . Electric Utilities Gas Utilities Commercial (in millions) and Infrastructure and Infrastructure Renewables Total Goodwill balance $ 17,379 $ 1,924 $ 122 $ 19,425 Accumulated impairment charges — — (29 ) (29 ) Goodwill, adjusted for accumulated impairment charges $ 17,379 $ 1,924 $ 93 $ 19,396

Related Party Transactions (Tab

Related Party Transactions (Tables)	3 Months Ended
	Mar. 31, 2018
Related Party Transaction [Line Items]
Schedule of Related Party Transactions, Other Revenue and Expense	Material amounts related to transactions with related parties included on the Condensed Consolidated Statements of Operations and Comprehensive Income are presented in the following table. Three Months Ended March 31, (in millions) 2018 2017 Duke Energy Carolinas Corporate governance and shared service expenses (a) $ 220 $ 221 Indemnification coverages (b) 6 6 JDA revenue (c) 34 16 JDA expense (c) 54 31 Intercompany natural gas purchases (d) 4 1 Progress Energy Corporate governance and shared service expenses (a) $ 191 $ 170 Indemnification coverages (b) 8 10 JDA revenue (c) 54 31 JDA expense (c) 34 16 Intercompany natural gas purchases (d) 19 19 Duke Energy Progress Corporate governance and shared service expenses (a) $ 118 $ 100 Indemnification coverages (b) 3 4 JDA revenue (c) 54 31 JDA expense (c) 34 16 Intercompany natural gas purchases (d) 19 19 Duke Energy Florida Corporate governance and shared service expenses (a) $ 73 $ 70 Indemnification coverages (b) 5 6 Duke Energy Ohio Corporate governance and shared service expenses (a) $ 89 $ 92 Indemnification coverages (b) 1 1 Duke Energy Indiana Corporate governance and shared service expenses (a) $ 101 $ 95 Indemnification coverages (b) 2 2 Piedmont Corporate governance and shared service expenses (a) $ 36 $ 5 Indemnification coverages (b) 1 1 Intercompany natural gas sales (d) 23 20 (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. The following table presents expenses for the three months ended March 31, 2018 , and 2017 , which are included in Cost of natural gas on Piedmont's Condensed Consolidated Statements of Operations and Comprehensive Income. Three Months Ended March 31, (in millions) Type of expense 2018 2017 Cardinal Transportation Costs $ 2 $ 2 Pine Needle Natural Gas Storage Costs 2 2 Hardy Storage Natural Gas Storage Costs 2 2 Total $ 6 $ 6 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 March 31, 2018 Intercompany income tax receivable $ — $ 183 $ 13 $ 9 $ — $ — $ — Intercompany income tax payable 9 — — — 3 18 43 December 31, 2017 Intercompany income tax receivable $ — $ 168 $ — $ 44 $ 22 $ — $ 7 Intercompany income tax payable 44 — 21 — — 35 —

Derivatives and Hedging (Tables

Derivatives and Hedging (Tables)	3 Months Ended
	Mar. 31, 2018
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. March 31, 2018 Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Cash flow hedges (a) $ 660 $ — $ — $ — $ — $ — Undesignated contracts 527 — 500 250 250 27 Total notional amount $ 1,187 $ — $ 500 $ 250 $ 250 $ 27 December 31, 2017 Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Cash flow hedges (a) $ 660 $ — $ — $ — $ — $ — Undesignated contracts 927 400 500 250 250 27 Total notional amount $ 1,587 $ 400 $ 500 $ 250 $ 250 $ 27 (a) Duke Energy includes amounts related to consolidated VIEs of $660 million as of March 31, 2018 , and December 31, 2017 . 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. March 31, 2018 Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy Carolinas Energy Progress Florida Indiana Piedmont Electricity (gigawatt-hours) 16 — — — — 16 — Natural gas (millions of dekatherms) 765 110 179 149 30 2 474 December 31, 2017 Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy Carolinas Energy Progress Florida Indiana Piedmont Electricity (gigawatt-hours) 34 — — — — 34 — Natural gas (millions of dekatherms) 770 105 183 133 50 2 480
Location And Fair Value Of 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 March 31, 2018 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Commodity Contracts Not Designated as Hedging Instruments Current $ 14 $ 2 $ 3 $ 2 $ 1 $ 1 $ 7 $ 1 Noncurrent 1 — — — — — — — Total Derivative Assets – Commodity Contracts $ 15 $ 2 $ 3 $ 2 $ 1 $ 1 $ 7 $ 1 Interest Rate Contracts Designated as Hedging Instruments Current $ 1 $ — $ — $ — $ — $ — $ — $ — Noncurrent 21 — — — — — — — Total Derivative Assets – Interest Rate Contracts $ 22 $ — $ — $ — $ — $ — $ — $ — Total Derivative Assets $ 37 $ 2 $ 3 $ 2 $ 1 $ 1 $ 7 $ 1 Derivative Liabilities March 31, 2018 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Commodity Contracts Not Designated as Hedging Instruments Current $ 26 $ 5 $ 8 $ 6 $ 3 $ — $ — $ 13 Noncurrent 140 6 15 6 — — — 119 Total Derivative Liabilities – Commodity Contracts $ 166 $ 11 $ 23 $ 12 $ 3 $ — $ — $ 132 Interest Rate Contracts Designated as Hedging Instruments Current $ 4 $ — $ — $ — $ — $ — $ — $ — Noncurrent 3 — — — — — — — Not Designated as Hedging Instruments Current 3 — 3 2 1 — — — Noncurrent 14 — 11 7 3 4 — — Total Derivative Liabilities – Interest Rate Contracts $ 24 $ — $ 14 $ 9 $ 4 $ 4 $ — $ — Total Derivative Liabilities $ 190 $ 11 $ 37 $ 21 $ 7 $ 4 $ — $ 132 Derivative Assets December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Commodity Contracts Not Designated as Hedging Instruments Current $ 34 $ 2 $ 2 $ 1 $ 1 $ 1 $ 27 $ 2 Noncurrent 1 — 1 1 — — — — Total Derivative Assets – Commodity Contracts $ 35 $ 2 $ 3 $ 2 $ 1 $ 1 $ 27 $ 2 Interest Rate Contracts Designated as Hedging Instruments Current $ 1 $ — $ — $ — $ — $ — $ — $ — Noncurrent 15 — — — — — — — Total Derivative Assets – Interest Rate Contracts $ 16 $ — $ — $ — $ — $ — $ — $ — Total Derivative Assets $ 51 $ 2 $ 3 $ 2 $ 1 $ 1 $ 27 $ 2 Derivative Liabilities December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Commodity Contracts Not Designated as Hedging Instruments Current $ 36 $ 6 $ 18 $ 8 $ 10 $ — $ — $ 11 Noncurrent 146 4 10 4 — — — 131 Total Derivative Liabilities – Commodity Contracts $ 182 $ 10 $ 28 $ 12 $ 10 $ — $ — $ 142 Interest Rate Contracts Designated as Hedging Instruments Current $ 29 $ 25 $ — $ — $ — $ — $ — $ — Noncurrent 6 — — — — — — — Not Designated as Hedging Instruments Current 1 — 1 — — 1 — — Noncurrent 12 — 7 6 2 4 — — Total Derivative Liabilities – Interest Rate Contracts $ 48 $ 25 $ 8 $ 6 $ 2 $ 5 $ — $ — Total Derivative Liabilities $ 230 $ 35 $ 36 $ 18 $ 12 $ 5 $ — $ 142
Offsetting Assets	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 March 31, 2018 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Current Gross amounts recognized $ 15 $ 2 $ 3 $ 2 $ 1 $ 1 $ 7 $ 1 Gross amounts offset (2 ) (1 ) (1 ) (1 ) — — — — Net amounts presented in Current Assets: Other $ 13 $ 1 $ 2 $ 1 $ 1 $ 1 $ 7 $ 1 Noncurrent Gross amounts recognized $ 22 $ — $ — $ — $ — $ — $ — $ — Gross amounts offset — — — — — — — — Net amounts presented in Other Noncurrent Assets: Other $ 22 $ — $ — $ — $ — $ — $ — $ — Derivative Assets December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Current Gross amounts recognized $ 35 $ 2 $ 2 $ 1 $ 1 $ 1 $ 27 $ 2 Gross amounts offset — — — — — — — — Net amounts presented in Current Assets: Other $ 35 $ 2 $ 2 $ 1 $ 1 $ 1 $ 27 $ 2 Noncurrent Gross amounts recognized $ 16 $ — $ 1 $ 1 $ — $ — $ — $ — Gross amounts offset — — — — — — — — Net amounts presented in Other Noncurrent Assets: Other $ 16 $ — $ 1 $ 1 $ — $ — $ — $ —
Offsetting Liabilities	Derivative Liabilities December 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Current Gross amounts recognized $ 66 $ 31 $ 19 $ 8 $ 10 $ 1 $ — $ 11 Gross amounts offset (3 ) (2 ) (2 ) (2 ) — — — — Net amounts presented in Current Liabilities: Other $ 63 $ 29 $ 17 $ 6 $ 10 $ 1 $ — $ 11 Noncurrent Gross amounts recognized $ 164 $ 4 $ 17 $ 10 $ 2 $ 4 $ — $ 131 Gross amounts offset (1 ) — (1 ) (1 ) — — — — Net amounts presented in Other Noncurrent Liabilities: Other $ 163 $ 4 $ 16 $ 9 $ 2 $ 4 $ — $ 131 Derivative Liabilities March 31, 2018 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Current Gross amounts recognized $ 33 $ 5 $ 11 $ 8 $ 4 $ — $ — $ 13 Gross amounts offset (4 ) (2 ) (2 ) (2 ) — — — — Net amounts presented in Current Liabilities: Other $ 29 $ 3 $ 9 $ 6 $ 4 $ — $ — $ 13 Noncurrent Gross amounts recognized $ 157 $ 6 $ 26 $ 13 $ 3 $ 4 $ — $ 119 Gross amounts offset (1 ) — (1 ) (1 ) — — — — Net amounts presented in Other Noncurrent Liabilities: Other $ 156 $ 6 $ 25 $ 12 $ 3 $ 4 $ — $ 119 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 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. March 31, 2018 Duke Duke Duke Duke Energy Progress Energy Energy (in millions) Energy Carolinas Energy Progress Florida Aggregate fair value of derivatives in a net liability position $ 30 $ 10 $ 20 $ 18 $ 2 Fair value of collateral already posted — — — — — Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered 30 10 20 18 2 December 31, 2017 Duke Duke Duke Duke Energy Progress Energy Energy (in millions) Energy Carolinas Energy Progress Florida Aggregate fair value of derivatives in a net liability position $ 59 $ 35 $ 25 $ 15 $ 10 Fair value of collateral already posted — — — — — Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered 59 35 25 15 10

Investments in Debt and Equit34

Investments in Debt and Equity Securities (Tables)	3 Months Ended
	Mar. 31, 2018
Schedule of Available-for-sale Securities [Line Items]
Debt Securities, Trading, and Equity Securities, FV-NI	The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. March 31, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 143 $ — $ — $ 115 Equity securities 2,751 38 4,857 2,805 27 4,914 Corporate debt securities 7 8 549 17 2 570 Municipal bonds 1 5 333 4 3 344 U.S. government bonds 6 18 1,014 11 7 1,027 Other debt securities — 2 130 — 1 118 Total NDTF Investments $ 2,765 $ 71 $ 7,026 $ 2,837 $ 40 $ 7,088 Other Investments Cash and cash equivalents $ — $ — $ 15 $ — $ — $ 15 Equity securities 57 — 130 59 — 123 Corporate debt securities — 1 64 1 — 57 Municipal bonds 1 1 80 2 1 83 U.S. government bonds — 1 51 — — 41 Other debt securities — — 48 — 1 44 Total Other Investments $ 58 $ 3 $ 388 $ 62 $ 2 $ 363 Total Investments $ 2,823 $ 74 $ 7,414 $ 2,899 $ 42 $ 7,451 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected .
Debt Securities, Available-for-sale	The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. March 31, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 143 $ — $ — $ 115 Equity securities 2,751 38 4,857 2,805 27 4,914 Corporate debt securities 7 8 549 17 2 570 Municipal bonds 1 5 333 4 3 344 U.S. government bonds 6 18 1,014 11 7 1,027 Other debt securities — 2 130 — 1 118 Total NDTF Investments $ 2,765 $ 71 $ 7,026 $ 2,837 $ 40 $ 7,088 Other Investments Cash and cash equivalents $ — $ — $ 15 $ — $ — $ 15 Equity securities 57 — 130 59 — 123 Corporate debt securities — 1 64 1 — 57 Municipal bonds 1 1 80 2 1 83 U.S. government bonds — 1 51 — — 41 Other debt securities — — 48 — 1 44 Total Other Investments $ 58 $ 3 $ 388 $ 62 $ 2 $ 363 Total Investments $ 2,823 $ 74 $ 7,414 $ 2,899 $ 42 $ 7,451 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected .
Available-for-sale Securities	The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. March 31, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 143 $ — $ — $ 115 Equity securities 2,751 38 4,857 2,805 27 4,914 Corporate debt securities 7 8 549 17 2 570 Municipal bonds 1 5 333 4 3 344 U.S. government bonds 6 18 1,014 11 7 1,027 Other debt securities — 2 130 — 1 118 Total NDTF Investments $ 2,765 $ 71 $ 7,026 $ 2,837 $ 40 $ 7,088 Other Investments Cash and cash equivalents $ — $ — $ 15 $ — $ — $ 15 Equity securities 57 — 130 59 — 123 Corporate debt securities — 1 64 1 — 57 Municipal bonds 1 1 80 2 1 83 U.S. government bonds — 1 51 — — 41 Other debt securities — — 48 — 1 44 Total Other Investments $ 58 $ 3 $ 388 $ 62 $ 2 $ 363 Total Investments $ 2,823 $ 74 $ 7,414 $ 2,899 $ 42 $ 7,451 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected .
Investments Classified by Contractual Maturity Date	The table below summarizes the maturity date for debt securities. (in millions) March 31, 2018 Due in one year or less $ 100 Due after one through five years 535 Due after five through 10 years 530 Due after 10 years 1,104 Total $ 2,269
Schedule of Realized Gain (Loss)	Realized gains and losses, which were determined on a specific identification basis, from sales of FV-NI and AFS securities for the three months ended March 31, 2018 and from sales of AFS securities for the three months ended March 31, 2017 were as follows. Three Months Ended (in millions) March 31, 2018 FV-NI: Realized gains $ 19 Realized losses 13 AFS: Realized gains 5 Realized losses 13 Three Months Ended (in millions) March 31, 2017 Realized gains $ 93 Realized losses 62
Duke Energy Carolinas [Member]
Schedule of Available-for-sale Securities [Line Items]
Debt Securities, Trading, and Equity Securities, FV-NI	The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. March 31, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 50 $ — $ — $ 32 Equity securities 1,502 20 2,669 1,531 12 2,692 Corporate debt securities 3 5 333 9 2 359 Municipal bonds — 1 69 — 1 60 U.S. government bonds 2 11 494 3 4 503 Other debt securities — 2 122 — 1 112 Total NDTF Investments $ 1,507 $ 39 $ 3,737 $ 1,543 $ 20 $ 3,758 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected .
Debt Securities, Available-for-sale	The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. March 31, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 50 $ — $ — $ 32 Equity securities 1,502 20 2,669 1,531 12 2,692 Corporate debt securities 3 5 333 9 2 359 Municipal bonds — 1 69 — 1 60 U.S. government bonds 2 11 494 3 4 503 Other debt securities — 2 122 — 1 112 Total NDTF Investments $ 1,507 $ 39 $ 3,737 $ 1,543 $ 20 $ 3,758 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected .
Available-for-sale Securities	The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. March 31, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 50 $ — $ — $ 32 Equity securities 1,502 20 2,669 1,531 12 2,692 Corporate debt securities 3 5 333 9 2 359 Municipal bonds — 1 69 — 1 60 U.S. government bonds 2 11 494 3 4 503 Other debt securities — 2 122 — 1 112 Total NDTF Investments $ 1,507 $ 39 $ 3,737 $ 1,543 $ 20 $ 3,758 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected .
Investments Classified by Contractual Maturity Date	The table below summarizes the maturity date for debt securities. (in millions) March 31, 2018 Due in one year or less $ 11 Due after one through five years 178 Due after five through 10 years 285 Due after 10 years 544 Total $ 1,018
Schedule of Realized Gain (Loss)	Realized gains and losses, which were determined on a specific identification basis, from sales of FV-NI and AFS securities for the three months ended March 31, 2018 and from sales of AFS securities for the three months ended March 31, 2017 were as follows. Three Months Ended (in millions) March 31, 2018 FV-NI: Realized gains $ 10 Realized losses 5 AFS: Realized gains 5 Realized losses 10 Three Months Ended (in millions) March 31, 2017 Realized gains $ 66 Realized losses 40
Progress Energy [Member]
Schedule of Available-for-sale Securities [Line Items]
Debt Securities, Trading, and Equity Securities, FV-NI	The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. March 31, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 93 $ — $ — $ 83 Equity securities 1,249 18 2,188 1,274 15 2,222 Corporate debt securities 4 3 216 8 — 211 Municipal bonds 1 4 264 4 2 284 U.S. government bonds 4 7 520 8 3 524 Other debt securities — — 8 — — 6 Total NDTF Investments $ 1,258 $ 32 $ 3,289 $ 1,294 $ 20 $ 3,330 Other Investments Cash and cash equivalents $ — $ — $ 10 $ — $ — $ 12 Municipal bonds 1 — 47 2 — 47 Total Other Investments $ 1 $ — $ 57 $ 2 $ — $ 59 Total Investments $ 1,259 $ 32 $ 3,346 $ 1,296 $ 20 $ 3,389 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected .
Debt Securities, Available-for-sale	The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. March 31, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 93 $ — $ — $ 83 Equity securities 1,249 18 2,188 1,274 15 2,222 Corporate debt securities 4 3 216 8 — 211 Municipal bonds 1 4 264 4 2 284 U.S. government bonds 4 7 520 8 3 524 Other debt securities — — 8 — — 6 Total NDTF Investments $ 1,258 $ 32 $ 3,289 $ 1,294 $ 20 $ 3,330 Other Investments Cash and cash equivalents $ — $ — $ 10 $ — $ — $ 12 Municipal bonds 1 — 47 2 — 47 Total Other Investments $ 1 $ — $ 57 $ 2 $ — $ 59 Total Investments $ 1,259 $ 32 $ 3,346 $ 1,296 $ 20 $ 3,389 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected .
Available-for-sale Securities	The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. March 31, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 93 $ — $ — $ 83 Equity securities 1,249 18 2,188 1,274 15 2,222 Corporate debt securities 4 3 216 8 — 211 Municipal bonds 1 4 264 4 2 284 U.S. government bonds 4 7 520 8 3 524 Other debt securities — — 8 — — 6 Total NDTF Investments $ 1,258 $ 32 $ 3,289 $ 1,294 $ 20 $ 3,330 Other Investments Cash and cash equivalents $ — $ — $ 10 $ — $ — $ 12 Municipal bonds 1 — 47 2 — 47 Total Other Investments $ 1 $ — $ 57 $ 2 $ — $ 59 Total Investments $ 1,259 $ 32 $ 3,346 $ 1,296 $ 20 $ 3,389 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected .
Investments Classified by Contractual Maturity Date	The table below summarizes the maturity date for debt securities. (in millions) March 31, 2018 Due in one year or less $ 75 Due after one through five years 300 Due after five through 10 years 198 Due after 10 years 482 Total $ 1,055
Schedule of Realized Gain (Loss)	Realized gains and losses, which were determined on a specific identification basis, from sales of FV-NI and AFS securities for the three months ended March 31, 2018 and from sales of AFS securities for the three months ended March 31, 2017 were as follows. Three Months Ended (in millions) March 31, 2018 FV-NI: Realized gains $ 9 Realized losses 8 AFS: Realized losses 3 Three Months Ended (in millions) March 31, 2017 Realized gains $ 27 Realized losses 21
Duke Energy Progress [Member]
Schedule of Available-for-sale Securities [Line Items]
Debt Securities, Trading, and Equity Securities, FV-NI	The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. March 31, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 59 $ — $ — $ 50 Equity securities 959 14 1,765 980 12 1,795 Corporate debt securities 3 2 153 6 — 149 Municipal bonds 1 4 263 4 2 283 U.S. government bonds 3 5 326 5 2 310 Other debt securities — — 5 — — 4 Total NDTF Investments $ 966 $ 25 $ 2,571 $ 995 $ 16 $ 2,591 Other Investments Cash and cash equivalents $ — $ — $ 1 $ — $ — $ 1 Total Other Investments $ — $ — $ 1 $ — $ — $ 1 Total Investments $ 966 $ 25 $ 2,572 $ 995 $ 16 $ 2,592 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected .
Debt Securities, Available-for-sale	The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. March 31, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 59 $ — $ — $ 50 Equity securities 959 14 1,765 980 12 1,795 Corporate debt securities 3 2 153 6 — 149 Municipal bonds 1 4 263 4 2 283 U.S. government bonds 3 5 326 5 2 310 Other debt securities — — 5 — — 4 Total NDTF Investments $ 966 $ 25 $ 2,571 $ 995 $ 16 $ 2,591 Other Investments Cash and cash equivalents $ — $ — $ 1 $ — $ — $ 1 Total Other Investments $ — $ — $ 1 $ — $ — $ 1 Total Investments $ 966 $ 25 $ 2,572 $ 995 $ 16 $ 2,592 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected .
Available-for-sale Securities	The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. March 31, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 59 $ — $ — $ 50 Equity securities 959 14 1,765 980 12 1,795 Corporate debt securities 3 2 153 6 — 149 Municipal bonds 1 4 263 4 2 283 U.S. government bonds 3 5 326 5 2 310 Other debt securities — — 5 — — 4 Total NDTF Investments $ 966 $ 25 $ 2,571 $ 995 $ 16 $ 2,591 Other Investments Cash and cash equivalents $ — $ — $ 1 $ — $ — $ 1 Total Other Investments $ — $ — $ 1 $ — $ — $ 1 Total Investments $ 966 $ 25 $ 2,572 $ 995 $ 16 $ 2,592 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected .
Investments Classified by Contractual Maturity Date	The table below summarizes the maturity date for debt securities. (in millions) March 31, 2018 Due in one year or less $ 19 Due after one through five years 216 Due after five through 10 years 144 Due after 10 years 368 Total $ 747
Schedule of Realized Gain (Loss)	Realized gains and losses, which were determined on a specific identification basis, from sales of FV-NI and AFS securities for the three months ended March 31, 2018 and from sales of AFS securities for the three months ended March 31, 2017 were as follows. Three Months Ended (in millions) March 31, 2018 FV-NI: Realized gains $ 8 Realized losses 8 AFS: Realized losses 2 Three Months Ended (in millions) March 31, 2017 Realized gains $ 24 Realized losses 19
Duke Energy Florida [Member]
Schedule of Available-for-sale Securities [Line Items]
Debt Securities, Trading, and Equity Securities, FV-NI	The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. March 31, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 34 $ — $ — $ 33 Equity securities 290 4 423 294 3 427 Corporate debt securities 1 1 63 2 — 62 Municipal bonds — — 1 — — 1 U.S. government bonds 1 2 194 3 1 214 Other debt securities — — 3 — — 2 Total NDTF Investments (b) $ 292 $ 7 $ 718 $ 299 $ 4 $ 739 Other Investments Cash and cash equivalents $ — $ — $ — $ — $ — $ 1 Municipal bonds 1 — 47 2 — 47 Total Other Investments $ 1 $ — $ 47 $ 2 $ — $ 48 Total Investments $ 293 $ 7 $ 765 $ 301 $ 4 $ 787 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected . (b) During the three months ended March 31, 2018 , Duke Energy Florida continued to receive reimbursements from the NDTF for costs related to ongoing decommissioning activity of the Crystal River Unit 3 nuclear plant.
Debt Securities, Available-for-sale	The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. March 31, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 34 $ — $ — $ 33 Equity securities 290 4 423 294 3 427 Corporate debt securities 1 1 63 2 — 62 Municipal bonds — — 1 — — 1 U.S. government bonds 1 2 194 3 1 214 Other debt securities — — 3 — — 2 Total NDTF Investments (b) $ 292 $ 7 $ 718 $ 299 $ 4 $ 739 Other Investments Cash and cash equivalents $ — $ — $ — $ — $ — $ 1 Municipal bonds 1 — 47 2 — 47 Total Other Investments $ 1 $ — $ 47 $ 2 $ — $ 48 Total Investments $ 293 $ 7 $ 765 $ 301 $ 4 $ 787 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected . (b) During the three months ended March 31, 2018 , Duke Energy Florida continued to receive reimbursements from the NDTF for costs related to ongoing decommissioning activity of the Crystal River Unit 3 nuclear plant.
Available-for-sale Securities	The following table presents the estimated fair value of investments in debt and equity securities; equity investments are classified as FV-NI and debt investments are classified as AFS. March 31, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value NDTF Cash and cash equivalents $ — $ — $ 34 $ — $ — $ 33 Equity securities 290 4 423 294 3 427 Corporate debt securities 1 1 63 2 — 62 Municipal bonds — — 1 — — 1 U.S. government bonds 1 2 194 3 1 214 Other debt securities — — 3 — — 2 Total NDTF Investments (b) $ 292 $ 7 $ 718 $ 299 $ 4 $ 739 Other Investments Cash and cash equivalents $ — $ — $ — $ — $ — $ 1 Municipal bonds 1 — 47 2 — 47 Total Other Investments $ 1 $ — $ 47 $ 2 $ — $ 48 Total Investments $ 293 $ 7 $ 765 $ 301 $ 4 $ 787 (a) Where regulatory accounting is applied, realized and unrealized gains and losses are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected . (b) During the three months ended March 31, 2018 , Duke Energy Florida continued to receive reimbursements from the NDTF for costs related to ongoing decommissioning activity of the Crystal River Unit 3 nuclear plant.
Investments Classified by Contractual Maturity Date	The table below summarizes the maturity date for debt securities. (in millions) March 31, 2018 Due in one year or less $ 56 Due after one through five years 84 Due after five through 10 years 54 Due after 10 years 114 Total $ 308
Schedule of Realized Gain (Loss)	Realized gains and losses, which were determined on a specific identification basis, from sales of FV-NI and AFS securities for the three months ended March 31, 2018 and from sales of AFS securities for the three months ended March 31, 2017 were as follows. Three Months Ended (in millions) March 31, 2018 FV-NI: Realized gains $ 1 AFS: Realized losses 1 Three Months Ended (in millions) March 31, 2017 Realized gains $ 3 Realized losses 2
Duke Energy Indiana [Member]
Schedule of Available-for-sale Securities [Line Items]
Debt Securities, Trading, and Equity Securities, FV-NI	The following table presents the estimated fair value of investments in debt and equity securities; equity investments are measured at FV-NI and debt investments are classified as AFS. March 31, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value Investments Equity securities $ 48 $ — $ 96 $ 49 $ — $ 97 Corporate debt securities — — 5 — — 3 Municipal bonds — 1 26 — 1 28 Total Investments $ 48 $ 1 $ 127 $ 49 $ 1 $ 128 (a) Realized and unrealized gains and losses where regulatory accounting is applied are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected .
Debt Securities, Available-for-sale	The following table presents the estimated fair value of investments in debt and equity securities; equity investments are measured at FV-NI and debt investments are classified as AFS. March 31, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value Investments Equity securities $ 48 $ — $ 96 $ 49 $ — $ 97 Corporate debt securities — — 5 — — 3 Municipal bonds — 1 26 — 1 28 Total Investments $ 48 $ 1 $ 127 $ 49 $ 1 $ 128 (a) Realized and unrealized gains and losses where regulatory accounting is applied are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected .
Available-for-sale Securities	The following table presents the estimated fair value of investments in debt and equity securities; equity investments are measured at FV-NI and debt investments are classified as AFS. March 31, 2018 (a) December 31, 2017 Gross Gross Gross Gross Unrealized Unrealized Estimated Unrealized Unrealized Estimated Holding Holding Fair Holding Holding Fair (in millions) Gains Losses Value Gains Losses Value Investments Equity securities $ 48 $ — $ 96 $ 49 $ — $ 97 Corporate debt securities — — 5 — — 3 Municipal bonds — 1 26 — 1 28 Total Investments $ 48 $ 1 $ 127 $ 49 $ 1 $ 128 (a) Realized and unrealized gains and losses where regulatory accounting is applied are deferred as regulatory assets or liabilities, and there is no impact to net income or other comprehensive income until the gain or loss is amortized or collected .
Investments Classified by Contractual Maturity Date	The table below summarizes the maturity date for debt securities. (in millions) March 31, 2018 Due in one year or less $ 3 Due after one through five years 15 Due after five through 10 years 6 Due after 10 years 7 Total $ 31

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurement Amounts For Assets And Liabilities	The following tables provide recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets. Derivative amounts in the tables below for all Duke Energy Registrants exclude cash collateral, which is disclosed in Note 8 . See Note 9 for additional information related to investments by major security type for the Duke Energy Registrants. March 31, 2018 (in millions) Total Fair Value Level 1 Level 2 Level 3 Not Categorized NDTF equity securities $ 4,857 $ 4,785 $ — $ — $ 72 NDTF debt securities 2,169 633 1,536 — — Other equity securities 130 130 — — — Other debt securities 258 66 192 — — Derivative assets 37 2 27 8 — Total assets 7,451 5,616 1,755 8 72 Derivative liabilities (190 ) (1 ) (57 ) (132 ) — Net assets (liabilities) $ 7,261 $ 5,615 $ 1,698 $ (124 ) $ 72 December 31, 2017 (in millions) Total Fair Value Level 1 Level 2 Level 3 Not Categorized NDTF equity securities $ 4,914 $ 4,840 $ — $ — $ 74 NDTF debt securities 2,174 635 1,539 — — Other equity securities 123 123 — — — Other debt securities 241 57 184 — — Derivative assets 51 3 20 28 — Total assets 7,503 5,658 1,743 28 74 Derivative liabilities (230 ) (2 ) (86 ) (142 ) — Net assets (liabilities) $ 7,273 $ 5,656 $ 1,657 $ (114 ) $ 74
Reconciliation Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Using Unobservable Inputs	The following table provides 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 March 31, 2018 Three Months Ended March 31, 2017 (in millions) Investments Derivatives (net) Total Investments Derivatives (net) Total Balance at beginning of period $ — $ (114 ) $ (114 ) $ 5 $ (166 ) $ (161 ) Purchases, sales, issuances and settlements: Settlements — (14 ) (14 ) — (9 ) (9 ) Total gains included on the Condensed Consolidated Balance Sheet — 4 4 — 40 40 Balance at end of period $ — $ (124 ) $ (124 ) $ 5 $ (135 ) $ (130 )
Quantitative Information Table - Level 3	The following tables include quantitative information about the Duke Energy Registrants' derivatives classified as Level 3. March 31, 2018 Fair Value Investment Type (in millions) Valuation Technique Unobservable Input Range Duke Energy Ohio Financial Transmission Rights (FTRs) $ 1 RTO auction pricing FTR price – per megawatt-hour (MWh) $ — - $ 2.88 Duke Energy Indiana FTRs 7 RTO auction pricing FTR price – per MWh (5.09 ) - 7.58 Piedmont Natural gas contracts (132 ) Discounted cash flow Forward natural gas curves – price per million British thermal unit (MMBtu) 2.15 - 3.65 Duke Energy Total Level 3 derivatives $ (124 ) December 31, 2017 Fair Value Investment Type (in millions) Valuation Technique Unobservable Input Range Duke Energy Ohio FTRs $ 1 RTO auction pricing FTR price – per MWh $ 0.07 - $ 1.41 Duke Energy Indiana FTRs 27 RTO auction pricing FTR price – per MWh (0.77 ) - 7.44 Piedmont Natural gas contracts (142 ) Discounted cash flow Forward natural gas curves – price per MMBtu 2.10 - 2.88 Duke Energy Total Level 3 derivatives $ (114 )
Schedule Of Long Term Debt Fair Value	The fair value and book value of long-term debt, including current maturities, is summarized in the following table. Estimates determined are not necessarily indicative of amounts that could have been settled in current markets. Fair value of long-term debt uses Level 2 measurements. March 31, 2018 December 31, 2017 (in millions) Book Value Fair Value Book Value Fair Value Duke Energy $ 52,981 $ 54,383 $ 52,279 $ 55,331 Duke Energy Carolinas 10,694 11,556 10,103 11,372 Progress Energy 17,757 19,270 17,837 20,000 Duke Energy Progress 7,357 7,687 7,357 7,992 Duke Energy Florida 7,015 7,632 7,095 7,953 Duke Energy Ohio 2,067 2,217 2,067 2,249 Duke Energy Indiana 3,782 4,322 3,783 4,464 Piedmont 2,037 2,209 2,037 2,209
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. March 31, 2018 (in millions) Total Fair Value Level 1 Level 2 Not Categorized NDTF equity securities $ 2,669 $ 2,597 $ — $ 72 NDTF debt securities 1,068 209 859 — Derivative assets 2 — 2 — Total assets 3,739 2,806 861 72 Derivative liabilities (11 ) (1 ) (10 ) — Net assets $ 3,728 $ 2,805 $ 851 $ 72 December 31, 2017 (in millions) Total Fair Value Level 1 Level 2 Not Categorized NDTF equity securities $ 2,692 $ 2,618 $ — $ 74 NDTF debt securities 1,066 204 862 — Derivative assets 2 — 2 — Total assets 3,760 2,822 864 74 Derivative liabilities (35 ) (1 ) (34 ) — Net assets $ 3,725 $ 2,821 $ 830 $ 74
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. March 31, 2018 (in millions) Total Fair Value Level 1 Level 2 NDTF equity securities $ 2,188 $ 2,188 $ — NDTF debt securities 1,101 424 677 Other debt securities 57 10 47 Derivative assets 3 — 3 Total assets 3,349 2,622 727 Derivative liabilities (37 ) (1 ) (36 ) Net assets $ 3,312 $ 2,621 $ 691 December 31, 2017 (in millions) Total Fair Value Level 1 Level 2 NDTF equity securities $ 2,222 $ 2,222 $ — NDTF debt securities 1,108 431 677 Other debt securities 59 12 47 Derivative assets 3 1 2 Total assets 3,392 2,666 726 Derivative liabilities (36 ) (1 ) (35 ) Net assets $ 3,356 $ 2,665 $ 691
Duke Energy Progress [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurement Amounts For Assets And Liabilities	The following tables provide recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets. March 31, 2018 (in millions) Total Fair Value Level 1 Level 2 NDTF equity securities $ 1,765 $ 1,765 $ — NDTF debt securities 806 254 552 Other debt securities 1 1 — Derivative assets 2 — 2 Total assets 2,574 2,020 554 Derivative liabilities (21 ) (1 ) (20 ) Net assets $ 2,553 $ 2,019 $ 534 December 31, 2017 (in millions) Total Fair Value Level 1 Level 2 NDTF equity securities $ 1,795 $ 1,795 $ — NDTF debt securities 796 243 553 Other debt securities 1 1 — Derivative assets 2 1 1 Total assets 2,594 2,040 554 Derivative liabilities (18 ) (1 ) (17 ) Net assets $ 2,576 $ 2,039 $ 537
Duke Energy Florida [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurement Amounts For Assets And Liabilities	The following tables provide recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets. March 31, 2018 (in millions) Total Fair Value Level 1 Level 2 NDTF equity securities $ 423 $ 423 $ — NDTF debt securities 295 170 125 Other debt securities 47 — 47 Derivative assets 1 — 1 Total assets 766 593 173 Derivative liabilities (7 ) — (7 ) Net assets $ 759 $ 593 $ 166 December 31, 2017 (in millions) Total Fair Value Level 1 Level 2 NDTF equity securities $ 427 $ 427 $ — NDTF debt securities 312 188 124 Other debt securities 48 1 47 Derivative assets 1 — 1 Total assets 788 616 172 Derivative liabilities (12 ) — (12 ) Net assets $ 776 $ 616 $ 160
Duke Energy Ohio [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurement Amounts For Assets And Liabilities	The following table provides recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets. March 31, 2018 December 31, 2017 (in millions) Total Fair Value Level 2 Level 3 Total Fair Value Level 2 Level 3 Derivative assets $ 1 $ — $ 1 $ 1 $ — $ 1 Derivative liabilities (4 ) (4 ) — (5 ) (5 ) — Net (liabilities) assets $ (3 ) $ (4 ) $ 1 $ (4 ) $ (5 ) $ 1
Reconciliation Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Using Unobservable Inputs	The following table provides a reconciliation of beginning and ending balances of assets and liabilities measured at fair value using Level 3 measurements. Derivatives (net) Three Months Ended March 31, (in millions) 2018 2017 Balance at beginning of period $ 1 $ 5 Purchases, sales, issuances and settlements: Settlements — (1 ) Total losses included on the Condensed Consolidated Balance Sheet — (3 ) Balance at end of period $ 1 $ 1
Duke Energy Indiana [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurement Amounts For Assets And Liabilities	The following tables provide recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets. March 31, 2018 (in millions) Total Fair Value Level 1 Level 2 Level 3 Other equity securities $ 96 $ 96 $ — $ — Other debt securities 31 — 31 — Derivative assets 7 — — 7 Total assets 134 96 31 7 Derivative liabilities — — — — Net assets $ 134 $ 96 $ 31 $ 7 December 31, 2017 (in millions) Total Fair Value Level 1 Level 2 Level 3 Other equity securities $ 97 $ 97 $ — $ — Other debt securities 31 — 31 — Derivative assets 27 — — 27 Total assets 155 97 31 27 Derivative liabilities — — — — Net assets $ 155 $ 97 $ 31 $ 27
Reconciliation Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Using Unobservable Inputs	The following table provides a reconciliation of beginning and ending balances of assets and liabilities measured at fair value using Level 3 measurements. Derivatives (net) Three Months Ended March 31, (in millions) 2018 2017 Balance at beginning of period $ 27 $ 16 Purchases, sales, issuances and settlements: Settlements (14 ) (7 ) Total (losses) gains included on the Condensed Consolidated Balance Sheet (6 ) — Balance at end of period $ 7 $ 9
Piedmont Natural Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurement Amounts For Assets And Liabilities	The following tables provide recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets. March 31, 2018 (in millions) Total Fair Value Level 1 Level 3 Derivative assets $ 1 $ 1 $ — Derivative liabilities (132 ) — (132 ) Net (liabilities) assets $ (131 ) $ 1 $ (132 ) December 31, 2017 (in millions) Total Fair Value Level 1 Level 3 Other debt securities $ 1 $ 1 $ — Derivative assets 2 2 — Total assets 3 3 — Derivative liabilities (142 ) — (142 ) Net (liabilities) assets $ (139 ) $ 3 $ (142 )
Reconciliation Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Using Unobservable Inputs	The following table provides a reconciliation of beginning and ending balances of assets and liabilities measured at fair value using Level 3 measurements. Derivatives (net) Three Months Ended March 31, (in millions) 2018 2017 Balance at beginning of period $ (142 ) $ (187 ) Total gains and settlements 10 42 Balance at end of period $ (132 ) $ (145 )

Variable Interest Entities (Tab

Variable Interest Entities (Tables)	3 Months Ended
	Mar. 31, 2018
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Schedule Of Variable Interest Entities	The following table summarizes the amounts and expiration dates of the credit facilities and associated restricted receivables described above. Duke Energy Duke Energy Duke Energy Duke Energy Carolinas Progress Florida (in millions) CRC DERF DEPR DEFR Expiration date December 2020 December 2020 February 2021 April 2019 (a) Credit facility amount $ 325 $ 450 $ 300 $ 225 Amounts borrowed at March 31, 2018 325 450 300 225 Amounts borrowed at December 31, 2017 325 450 300 225 Restricted Receivables at March 31, 2018 504 634 497 313 Restricted Receivables at December 31, 2017 545 640 459 317 (a) In April 2018, the credit facility was extended through April 2021 .
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. March 31, 2018 Duke Energy Duke Duke Pipeline Commercial Other Energy Energy (in millions) Investments Renewables VIEs Total Ohio Indiana Receivables from affiliated companies $ — $ — $ — $ — $ 65 $ 86 Investments in equity method unconsolidated affiliates 723 183 45 951 — — Other noncurrent assets 17 — — 17 — — Total assets $ 740 $ 183 $ 45 $ 968 $ 65 $ 86 Taxes accrued (29 ) — — (29 ) — — Other current liabilities — — 3 3 — — Deferred income taxes 32 — — 32 — — Other noncurrent liabilities 8 — 12 20 — — Total liabilities $ 11 $ — $ 15 $ 26 $ — $ — Net assets $ 729 $ 183 $ 30 $ 942 $ 65 $ 86 December 31, 2017 Duke Energy Duke Duke Pipeline Commercial Other Energy Energy (in millions) Investments Renewables VIEs Total Ohio Indiana Receivables from affiliated companies $ — $ — $ — $ — $ 87 $ 106 Investments in equity method unconsolidated affiliates 697 180 42 919 — — Other noncurrent assets 17 — — 17 — — Total assets $ 714 $ 180 $ 42 $ 936 $ 87 $ 106 Taxes accrued (29 ) — — (29 ) — — Other current liabilities — — 4 4 — — Deferred income taxes 42 — — 42 — — Other noncurrent liabilities — — 12 12 — — Total liabilities $ 13 $ — $ 16 $ 29 $ — $ — Net assets $ 701 $ 180 $ 26 $ 907 $ 87 $ 106
DEFPF [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Schedule Of Variable Interest Entities	The following table summarizes the impact of DEFPF on Duke Energy Florida's Condensed Consolidated Balance Sheets. (in millions) March 31, 2018 December 31, 2017 Receivables of VIEs $ 4 $ 4 Regulatory Assets: Current 51 51 Current Assets: Other 13 40 Other Noncurrent Assets: Regulatory assets 1,082 1,091 Current Liabilities: Other 3 10 Current maturities of long-term debt 53 53 Long-Term Debt 1,136 1,164
Commercial Renewables [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Schedule Of Variable Interest Entities	The table below presents material balances reported on Duke Energy's Condensed Consolidated Balance Sheets related to renewables VIEs. (in millions) March 31, 2018 December 31, 2017 Current Assets: Other $ 217 $ 174 Property, plant and equipment, cost 4,017 3,923 Other Noncurrent Assets: Other 227 50 Accumulated depreciation and amortization (626 ) (591 ) Current maturities of long-term debt 171 170 Long-Term Debt 1,700 1,700 Other Noncurrent Liabilities: Deferred income taxes — (148 ) Other Noncurrent Liabilities: Other 236 241
Pipeline Investments [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Schedule Of Variable Interest Entities	The table below presents Duke Energy's ownership interest and investment balances in these joint ventures. VIE Investment Amount (in millions) Ownership March 31, December 31, Entity Name Interest 2018 2017 ACP 47 % $ 474 $ 397 Sabal Trail 7.5 % 223 219 Constitution (a) 24 % 26 81 Total $ 723 $ 697 (a) During the three months ended March 31, 2018 , Duke Energy recorded an OTTI of $55 million related to Constitution within Equity in (losses) earnings of unconsolidated affiliates on Duke Energy's Condensed Consolidated Statements of Income. See Note 3 for additional information.
Cinergy Receivables [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Schedule Of Variable Interest Entities	Key assumptions used in estimating fair value are detailed in the following table. Duke Energy Ohio Duke Energy Indiana 2018 2017 2018 2017 Anticipated credit loss ratio 0.5 % 0.5 % 0.3 % 0.3 % Discount rate 2.6 % 2.1 % 2.6 % 2.1 % Receivable turnover rate 13.6 % 13.5 % 10.8 % 10.7 % The following table shows the gross and net receivables sold. Duke Energy Ohio Duke Energy Indiana (in millions) March 31, 2018 December 31, 2017 March 31, 2018 December 31, 2017 Receivables sold $ 249 $ 273 $ 297 $ 312 Less: Retained interests 65 87 86 106 Net receivables sold $ 184 $ 186 $ 211 $ 206 The following table shows sales and cash flows related to receivables sold. Duke Energy Ohio Duke Energy Indiana Three Months Ended Three Months Ended March 31, March 31, (in millions) 2018 2017 2018 2017 Sales Receivables sold $ 567 $ 533 $ 694 $ 664 Loss recognized on sale 3 2 3 3 Cash flows Cash proceeds from receivables sold $ 585 $ 559 $ 711 $ 693 Return received on retained interests 2 1 2 2

Revenue (Tables)

Revenue (Tables)	3 Months Ended
	Mar. 31, 2018
Revenue from Contract with Customer [Abstract]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction	Estimated remaining performance obligations are as follows: Remaining Performance Obligations (in millions) 2018 2019 2020 2021 2022 Thereafter Total Piedmont $ 55 $ 72 $ 70 $ 65 $ 64 $ 482 $ 808 Supplemental requirements contracts that include contracted blocks of energy and capacity at contractually fixed prices have the following estimated remaining performance obligations: Remaining Performance Obligations (in millions) 2018 2019 2020 2021 2022 Thereafter Total Progress Energy $ 69 $ 112 $ 121 $ 80 $ 82 $ 81 $ 545 Duke Energy Progress 7 9 9 9 9 18 61 Duke Energy Florida 62 103 112 71 73 63 484 Duke Energy Indiana 6 9 10 5 — — 30
Disaggregation of Revenue	Disaggregated revenues are presented as follows: Three Months Ended March 31, 2018 Duke Duke Duke Duke Duke (in millions) Duke Energy Progress Energy Energy Energy Energy By market or type of customer Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Electric Utilities and Infrastructure Residential $ 2,350 $ 781 $ 1,112 $ 516 $ 595 $ 180 $ 278 $ — General 1,375 472 631 299 333 96 178 — Industrial 664 255 208 145 62 30 173 — Wholesale 633 119 446 397 50 — 68 — Other revenues 139 67 129 85 43 14 17 — Total Electric Utilities and Infrastructure revenue from contracts with customers $ 5,161 $ 1,694 $ 2,526 $ 1,442 $ 1,083 $ 320 $ 714 $ — Gas Utilities and Infrastructure Residential $ 413 $ — $ — $ — $ — $ 111 $ — $ 302 Commercial 201 — — — — 49 — 152 Industrial 48 — — — — 7 — 41 Power Generation — — — — — — — 13 Other revenues 55 — — — — 6 — 49 Total Gas Utilities and Infrastructure revenue from contracts with customers $ 717 $ — $ — $ — $ — $ 173 $ — $ 557 Commercial Renewables Revenue from contracts with customers $ 33 $ — $ — $ — $ — $ — $ — $ — Other Revenue from contracts with customers $ 17 $ — $ — $ — $ — $ 14 $ — $ — Total revenue from contracts with customers $ 5,928 $ 1,694 $ 2,526 $ 1,442 $ 1,083 $ 507 $ 714 $ 557 Other revenue sources (a) $ 207 $ 69 $ 50 $ 18 $ 32 $ 17 $ 17 $ (4 ) Total revenues $ 6,135 $ 1,763 $ 2,576 $ 1,460 $ 1,115 $ 524 $ 731 $ 553 (a) Other revenue sources include revenues from leases, derivatives and alternative revenue programs that are not considered revenues from contracts with customers. Piedmont has regulatory mechanisms that periodically provide rate adjustments to refund any over-collection or to recover any under-collection of margin.
Schedule Of Unbilled Revenues With Restricted Receivables	These receivables for unbilled revenues are shown in the table below. (in millions) March 31, 2018 December 31, 2017 Duke Energy Ohio $ 67 $ 104 Duke Energy Indiana 108 132 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) March 31, 2018 December 31, 2017 Duke Energy $ 823 $ 944 Duke Energy Carolinas 310 342 Progress Energy 237 228 Duke Energy Progress 167 143 Duke Energy Florida 70 85 Duke Energy Ohio 2 4 Duke Energy Indiana 24 21 Piedmont 45 86

Common Stock (Tables)

Common Stock (Tables)	3 Months Ended
	Mar. 31, 2018
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 March 31, (in millions, except per-share amounts) 2018 2017 Income from continuing operations attributable to Duke Energy common stockholders excluding impact of participating securities $ 619 $ 715 Weighted average shares outstanding – basic 701 700 Weighted average shares outstanding – diluted 701 700 Earnings per share from continuing operations attributable to Duke Energy common stockholders Basic $ 0.88 $ 1.02 Diluted $ 0.88 $ 1.02 Potentially dilutive items excluded from the calculation (a) 2 2 Dividends declared per common share $ 0.89 $ 0.855 (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)	3 Months Ended
	Mar. 31, 2018
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 March 31, (in millions) 2018 2017 Restricted stock unit awards $ 10 $ 8 Performance awards 7 7 Pretax stock-based compensation cost $ 17 $ 15 Tax benefit associated with stock-based compensation expense $ 4 $ 5 Stock-based compensation costs capitalized 1 1

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	3 Months Ended
	Mar. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan Disclosures	The following table includes employer contributions made by Duke Energy and expensed by the Subsidiary Registrants. Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Three Months Ended March 31, 2018 $ 70 $ 23 $ 19 $ 13 $ 6 $ 1 $ 3 $ 4 2017 65 22 18 13 5 1 3 2
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 qualified defined benefit pension plans. Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Total anticipated 2018 contributions $ 148 $ 46 $ 45 $ 25 $ 20 $ — $ 8 $ 7 Contributions made during the three months ended March 31, 2018 141 46 45 25 20 — 8 — Remaining estimated 2018 contributions $ 7 $ — $ — $ — $ — $ — $ — $ 7
Components of Net Periodic Pension Costs	The following tables include the components of net periodic pension costs for qualified pension plans. Three Months Ended March 31, 2018 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Service cost $ 45 $ 15 $ 13 $ 7 $ 5 $ 1 $ 2 $ 2 Interest cost on projected benefit obligation 75 18 24 11 13 5 6 3 Expected return on plan assets (140 ) (37 ) (45 ) (21 ) (23 ) (7 ) (10 ) (6 ) Amortization of actuarial loss 33 7 11 5 6 1 2 3 Amortization of prior service credit (8 ) (2 ) (1 ) — — — — (3 ) Net periodic pension costs $ 5 $ 1 $ 2 $ 2 $ 1 $ — $ — $ (1 ) Three Months Ended March 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Service cost $ 40 $ 12 $ 12 $ 6 $ 5 $ 1 $ 2 $ 3 Interest cost on projected benefit obligation 82 20 25 12 13 5 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 $ 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 March 31, 2018 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Service cost $ 1 $ — $ — $ — $ — $ — $ — $ — Interest cost on accumulated post-retirement benefit obligation 7 2 4 1 1 — 1 — Expected return on plan assets (2 ) (2 ) — — — — — — Amortization of actuarial loss 1 — — — — — 1 — Amortization of prior service credit (5 ) (1 ) (2 ) — (1 ) — — — Net periodic other post-retirement benefit costs $ 2 $ (1 ) $ 2 $ 1 $ — $ — $ 2 $ — Three Months Ended March 31, 2017 Duke Duke Duke Duke Duke Duke Energy Progress Energy Energy Energy Energy (in millions) Energy Carolinas Energy Progress Florida Ohio Indiana Piedmont Service cost $ 1 $ — $ — $ — $ — $ — $ — $ — Interest cost on accumulated post-retirement benefit obligation 9 2 4 2 2 — — — Expected return on plan assets (3 ) (2 ) — — — — — — Amortization of actuarial loss (gain) 2 (1 ) 5 3 2 — — — Amortization of prior service credit (29 ) (2 ) (21 ) (14 ) (8 ) — — — Net periodic other post-retirement benefit costs $ (20 ) $ (3 ) $ (12 ) $ (9 ) $ (4 ) $ — $ — $ —

Income Taxes (Tables)

Income Taxes (Tables)	3 Months Ended
	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Summary of Effective Tax Rates	The effective tax rates from continuing operations for each of the Duke Energy Registrants are included in the following table. Three Months Ended March 31, 2018 2017 Duke Energy 22.5 % 32.4 % Duke Energy Carolinas 22.0 % 35.4 % Progress Energy 13.2 % 34.1 % Duke Energy Progress 14.1 % 34.1 % Duke Energy Florida 16.3 % 36.6 % Duke Energy Ohio 32.4 % 35.4 % Duke Energy Indiana 25.9 % 39.3 % Piedmont 24.1 % 37.9 %

Organization and Basis of Pre42

Organization and Basis of Presentation (Schedule of Cash and Cash Equivalents) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Cash and Cash Equivalents [Line Items]
Cash and Cash Equivalents, at Carrying Value	$ 421	$ 358
Restricted Cash and Cash Equivalents, Current	149	138
Restricted Cash and Cash Equivalents, Noncurrent	9	9
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	579	505	$ 1,022	$ 541
Progress Energy [Member]
Cash and Cash Equivalents [Line Items]
Cash and Cash Equivalents, at Carrying Value	20	40
Restricted Cash and Cash Equivalents, Current	13	40
Restricted Cash and Cash Equivalents, Noncurrent	6	7
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	39	87	58	110
Duke Energy Florida [Member]
Cash and Cash Equivalents [Line Items]
Cash and Cash Equivalents, at Carrying Value	6	13
Restricted Cash and Cash Equivalents, Current	13	40
Restricted Cash and Cash Equivalents, Noncurrent	0	0
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 19	$ 53	$ 21	$ 69

Organization and Basis of Pre43

Organization and Basis of Presentation (Schedule of Inventory) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Public Utilities, Inventory [Line Items]
Inventory	$ 3,149	$ 3,250
Materials and supplies [Member]
Public Utilities, Inventory [Line Items]
Inventory	2,293	2,293
Coal [Member]
Public Utilities, Inventory [Line Items]
Inventory	551	603
Natural gas, oil and other fuel [Member]
Public Utilities, Inventory [Line Items]
Inventory	305	354
Duke Energy Carolinas [Member]
Public Utilities, Inventory [Line Items]
Inventory	980	971
Duke Energy Carolinas [Member] | Materials and supplies [Member]
Public Utilities, Inventory [Line Items]
Inventory	763	744
Duke Energy Carolinas [Member] | Coal [Member]
Public Utilities, Inventory [Line Items]
Inventory	176	192
Duke Energy Carolinas [Member] | Natural gas, oil and other fuel [Member]
Public Utilities, Inventory [Line Items]
Inventory	41	35
Progress Energy [Member]
Public Utilities, Inventory [Line Items]
Inventory	1,537	1,592
Progress Energy [Member] | Materials and supplies [Member]
Public Utilities, Inventory [Line Items]
Inventory	1,095	1,118
Progress Energy [Member] | Coal [Member]
Public Utilities, Inventory [Line Items]
Inventory	221	255
Progress Energy [Member] | Natural gas, oil and other fuel [Member]
Public Utilities, Inventory [Line Items]
Inventory	221	219
Duke Energy Progress [Member]
Public Utilities, Inventory [Line Items]
Inventory	1,002	1,017
Duke Energy Progress [Member] | Materials and supplies [Member]
Public Utilities, Inventory [Line Items]
Inventory	767	774
Duke Energy Progress [Member] | Coal [Member]
Public Utilities, Inventory [Line Items]
Inventory	125	139
Duke Energy Progress [Member] | Natural gas, oil and other fuel [Member]
Public Utilities, Inventory [Line Items]
Inventory	110	104
Duke Energy Florida [Member]
Public Utilities, Inventory [Line Items]
Inventory	535	574
Duke Energy Florida [Member] | Materials and supplies [Member]
Public Utilities, Inventory [Line Items]
Inventory	329	343
Duke Energy Florida [Member] | Coal [Member]
Public Utilities, Inventory [Line Items]
Inventory	96	116
Duke Energy Florida [Member] | Natural gas, oil and other fuel [Member]
Public Utilities, Inventory [Line Items]
Inventory	110	115
Duke Energy Ohio [Member]
Public Utilities, Inventory [Line Items]
Inventory	108	133
Duke Energy Ohio [Member] | Materials and supplies [Member]
Public Utilities, Inventory [Line Items]
Inventory	82	82
Duke Energy Ohio [Member] | Coal [Member]
Public Utilities, Inventory [Line Items]
Inventory	13	17
Duke Energy Ohio [Member] | Natural gas, oil and other fuel [Member]
Public Utilities, Inventory [Line Items]
Inventory	13	34
Duke Energy Indiana [Member]
Public Utilities, Inventory [Line Items]
Inventory	453	450
Duke Energy Indiana [Member] | Materials and supplies [Member]
Public Utilities, Inventory [Line Items]
Inventory	310	309
Duke Energy Indiana [Member] | Coal [Member]
Public Utilities, Inventory [Line Items]
Inventory	141	139
Duke Energy Indiana [Member] | Natural gas, oil and other fuel [Member]
Public Utilities, Inventory [Line Items]
Inventory	2	2
Piedmont Natural Gas [Member]
Public Utilities, Inventory [Line Items]
Inventory	29	66
Piedmont Natural Gas [Member] | Materials and supplies [Member]
Public Utilities, Inventory [Line Items]
Inventory	1	2
Piedmont Natural Gas [Member] | Natural gas, oil and other fuel [Member]
Public Utilities, Inventory [Line Items]
Inventory	$ 28	$ 64

Organization and Basis of Pre44

Organization and Basis of Presentation (Schedule of Excise Taxes) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	$ 99	$ 91
Duke Energy Carolinas [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	8	9
Progress Energy [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	54	46
Duke Energy Progress [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	5	5
Duke Energy Florida [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	49	41
Duke Energy Ohio [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	30	28
Duke Energy Indiana [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	6	7
Piedmont Natural Gas [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	$ 1	$ 1

Organization and Basis of Pre45

Organization and Basis of Presentation (New Accounting Standards) (Details) - Accounting Standards Update 2017-07 (1) [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Expense [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	$ 156	$ 131	$ 96
Nonoperating Income (Expense) [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	$ 156	$ 131	$ 96

Business Segments (Narrative) (

Business Segments (Narrative) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)segment	Mar. 31, 2017USD ($)
Segment Reporting Information [Line Items]
Loss on Sales of Other Assets and Other, net	$ 100	$ (11)
Operation, maintenance and other	1,464	1,468
Duke Energy Ohio [Member]
Segment Reporting Information [Line Items]
Loss on Sales of Other Assets and Other, net	106
Operation, maintenance and other	$ 131	$ 131
Number of Reportable Segments | segment	2
Beckjord [Member]
Segment Reporting Information [Line Items]
Loss on Sales of Other Assets and Other, net	$ 106
Operation, maintenance and other	$ 1
National Methanol Company [Member]
Segment Reporting Information [Line Items]
Equity Method Investment, Ownership Percentage	17.50%

Business Segments (Business Seg

Business Segments (Business Segment Data) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Segment Reporting Information [Line Items]
Operating revenues	$ 6,135	$ 5,729
Segment income (loss)	620	716
Net Income (Loss) Attributable to Noncontrolling Interest	2	1
Net income	622	717
Segment assets	138,541		$ 137,914
Electric Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Operating revenues	5,315	4,939
Gas Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Operating revenues	702	648
Commercial Renewables [Member]
Segment Reporting Information [Line Items]
Operating revenues	101	128
Total Reportable Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	6,118	5,715
Other Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	17	14
Operating Segments [Member]
Segment Reporting Information [Line Items]
Segment income (loss)	886	793
Segment assets	135,682
Operating Segments [Member] | Electric Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Operating revenues	5,323	4,947
Segment income (loss)	750	635
Segment assets	120,021
Operating Segments [Member] | Gas Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Operating revenues	727	670
Segment income (loss)	116	133
Segment assets	11,396
Operating Segments [Member] | Commercial Renewables [Member]
Segment Reporting Information [Line Items]
Operating revenues	101	128
Segment income (loss)	20	25
Segment assets	4,265
Operating Segments [Member] | Total Reportable Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	6,151	5,745
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues	(51)	(49)
Segment assets	177
Intersegment Eliminations [Member] | Electric Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Operating revenues	8	8
Intersegment Eliminations [Member] | Gas Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Operating revenues	25	22
Intersegment Eliminations [Member] | Total Reportable Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	33	30
Intersegment Eliminations [Member] | Other Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	18	19
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Segment income (loss)	(266)	(77)
Segment assets	2,682
Corporate, Non-Segment [Member] | Other Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	35	33
Duke Energy Ohio [Member]
Segment Reporting Information [Line Items]
Operating revenues	524	518
Segment income (loss)	(25)	42
Segment assets	7,896		$ 7,875
Duke Energy Ohio [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	510	507
Segment income (loss)	67	50
Segment assets	7,874
Duke Energy Ohio [Member] | Operating Segments [Member] | Electric Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Operating revenues	336	337
Segment income (loss)	33	24
Segment assets	5,165
Duke Energy Ohio [Member] | Operating Segments [Member] | Gas Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Operating revenues	174	170
Segment income (loss)	34	26
Segment assets	2,709
Duke Energy Ohio [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Segment assets	(3)
Duke Energy Ohio [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues	14	11
Segment income (loss)	(92)	$ (8)
Segment assets	$ 25

Regulatory Matters (Narrative)

Regulatory Matters (Narrative) (Details) Customers in Millions, $ in Millions	Apr. 13, 2018USD ($)	Apr. 02, 2018USD ($)	Feb. 28, 2018USD ($)	Jun. 30, 2017USD ($)	Dec. 31, 2015USD ($)	Mar. 31, 2018USD ($)CustomersMW	Mar. 31, 2017USD ($)	Dec. 31, 2017USD ($)
Public Utilities, General Disclosures [Line Items]
Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses						$ 1,464	$ 1,468
Public Utilities, Property, Plant and Equipment, Net						87,373		$ 86,391
Loss Before Income Taxes						(803)	(1,061)
Electric Domestic Regulated Revenue						5,284	4,913
Generation Facilities To Be Retired [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Property, Plant and Equipment, Net						$ 391
Capacity (in MW) | MW						1,738
Atlantic Coast Pipeline (ACP) [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage						47.00%
Long-term Purchase Commitment, Period						20 years
Sabal Trail Transmission Pipeline [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage						7.50%
Estimated capital cost						$ 3,200
Long-term Purchase Commitment, Period						25 years
Constitution Pipeline [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage						24.00%
Estimated Contributions						$ 229
Equity Method Investment, Other than Temporary Impairment						$ 55
Dominion Resources [Member] | Atlantic Coast Pipeline (ACP) [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage						48.00%
Southern Company Gas [Member] | Atlantic Coast Pipeline (ACP) [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage						5.00%
Spectra Energy Partners [Member] | Sabal Trail Transmission Pipeline [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage						50.00%
NextEra Energy [Member] | Sabal Trail Transmission Pipeline [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage						42.50%
Williams Partners L.P. [Member] | Constitution Pipeline [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage						41.00%
Minimum [Member] | Atlantic Coast Pipeline (ACP) [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost						$ 6,000
Original estimated capital cost						5,000
Maximum [Member] | Atlantic Coast Pipeline (ACP) [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost						6,500
Original estimated capital cost						5,500
Duke Energy Carolinas [Member]
Public Utilities, General Disclosures [Line Items]
Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses						451	495
Public Utilities, Property, Plant and Equipment, Net						28,158		27,876
Loss Before Income Taxes						(414)	(418)
Duke Energy Carolinas [Member] | William States Lee Combined Cycle Facility [Member] | NCEMC [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost of new utility plant, including AFUDC						$ 650
Joint owner ownership percentage						13.00%
Duke Energy Carolinas [Member] | William State Lee III Nuclear Station [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Property, Plant and Equipment, Net						$ 558
Duke Energy Carolinas [Member] | 2017 North Carolina Rate Case [Member] | NCUC [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount						$ 647
Requested Rate Increase, Percentage						13.60%
Requested Return on Equity, Percentage						9.90%
Public Utilities, Requested Equity Capital Structure, Percentage						52.00%
Public Utilities, Requested Debt Capital Structure, Percentage						48.00%
Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses			$ 4
Requested Rate Increase (Decrease), Amended, Amount						$ 472
Loss Before Income Taxes						14
Duke Energy Carolinas [Member] | FERC Formula Rate Matter [Member] | FERC [Member]
Public Utilities, General Disclosures [Line Items]
Customer Refundable Fees, Refund Payments						25
Progress Energy [Member]
Public Utilities, General Disclosures [Line Items]
Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses						623	560
Public Utilities, Property, Plant and Equipment, Net						32,254		31,887
Loss Before Income Taxes						(273)	(305)
Duke Energy Progress [Member]
Public Utilities, General Disclosures [Line Items]
Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses						381	362
Public Utilities, Property, Plant and Equipment, Net						19,253		19,101
Loss Before Income Taxes						(206)	(223)
Duke Energy Progress [Member] | Asheville Plant [Member] | Generation Facilities To Be Retired [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Property, Plant and Equipment, Net						$ 365		385
Capacity (in MW) | MW						376
Duke Energy Progress [Member] | 2017 North Carolina Rate Case [Member] | NCUC [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount						$ 477
Requested Rate Increase, Percentage						14.90%
Requested Return on Equity, Percentage						9.90%
Public Utilities, Requested Equity Capital Structure, Percentage						52.00%
Public Utilities, Requested Debt Capital Structure, Percentage						48.00%
Requested Rate Increase (Decrease), Amended, Amount						$ 420
Requested Rate Increase (Decrease), Amended, Percentage						13.00%
Estimated Storm Costs - Capital and Operation Maintenance						$ 116
Utilities Operating Expense, Impairments								25
Penalty assessed						30
Estimated future coal ash costs						129
Loss Before Income Taxes						$ 68
Duke Energy Progress [Member] | 2017 North Carolina Rate Case [Member] | NCUC [Member] | Asset retirement obligations - coal ash [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Asset, Amortization Period						5 years
Excluded deferred coal ash costs						$ 9.5
Regulatory Assets						234
Duke Energy Progress [Member] | 2017 North Carolina Rate Case [Member] | NCUC [Member] | Storm Costs [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount						$ 80
Regulatory Asset, Amortization Period						5 years
Approved Rate Increase (Decrease), Amount						$ 51
Duke Energy Progress [Member] | 2016 South Carolina Rate Case Settlement [Member] | PSCSC [Member]
Public Utilities, General Disclosures [Line Items]
Approved Rate Increase (Decrease), Amount						$ 56
Asset Retirement Obligation, Accretion Expense								18.5
Approved return on equity percentage						10.10%
Duke Energy Progress [Member] | 2016 South Carolina Rate Case Settlement Year 1 Increase [Member] | PSCSC [Member]
Public Utilities, General Disclosures [Line Items]
Approved Rate Increase (Decrease), Amount						$ 38
Duke Energy Progress [Member] | 2016 South Carolina Rate Case Settlement Year 2 Increase [Member] | PSCSC [Member]
Public Utilities, General Disclosures [Line Items]
Approved Rate Increase (Decrease), Amount						$ 18.5
Duke Energy Progress [Member] | Western Carolinas Modernization Plan [Member] | NCUC [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Asset, Amortization Period						10 years
Estimated capital cost						$ 893
Duke Energy Progress [Member] | Shearon Harris Nuclear Expansion [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Asset, Amortization Period						8 years
Wholesale Debt Return Amortization Period						15 years
Regulatory Assets								47
Duke Energy Florida [Member]
Public Utilities, General Disclosures [Line Items]
Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses						$ 237	195
Public Utilities, Property, Plant and Equipment, Net						12,998		12,783
Loss Before Income Taxes						(123)	(142)
Duke Energy Florida [Member] | Storm Costs [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets						338
Duke Energy Florida [Member] | Citrus County Station [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost of new utility plant, including AFUDC						1,500
Duke Energy Florida [Member] | Storm Restoration Cost Recovery [Member] | FPSC [Member]
Public Utilities, General Disclosures [Line Items]
Estimated Storm Costs - Capital and Operation Maintenance						$ 513
Customers Experiencing Outages | Customers						1.3
Duke Energy Florida [Member] | Citrus County Combined Cycle Facility [Member] | Subsequent Event [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount		$ 200
Duke Energy Ohio [Member]
Public Utilities, General Disclosures [Line Items]
Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses						$ 131	131
Public Utilities, Property, Plant and Equipment, Net						6,163		6,041
Loss Before Income Taxes						37	(65)
Electric Domestic Regulated Revenue						336	337
Duke Energy Ohio [Member] | 2017 Ohio Electric Base Rate Case [Member] | PUCO [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount						$ 15
Requested Return on Equity, Percentage						10.40%
Approved Rate Increase (Decrease), Amount						$ (20)
Duke Energy Ohio [Member] | 2017 Ohio Electric Base Rate Case [Member] | PUCO [Member] | Minimum [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount						$ (18)
Requested Return on Equity, Percentage						9.22%
Duke Energy Ohio [Member] | 2017 Ohio Electric Base Rate Case [Member] | PUCO [Member] | Maximum [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount						$ (29)
Requested Return on Equity, Percentage						10.24%
Duke Energy Ohio [Member] | 2017 Ohio Electric Base Rate Case [Member] | Subsequent Event [Member] | PUCO [Member]
Public Utilities, General Disclosures [Line Items]
Requested Return on Equity, Percentage	9.84%
Public Utilities, Requested Equity Capital Structure, Percentage	50.75%
Public Utilities, Requested Debt Capital Structure, Percentage	49.25%
Requested Rate Increase (Decrease), Amended, Amount	$ (19)
Duke Energy Ohio [Member] | 2017 Ohio Electric Base Rate Case [Member] | Subsequent Event [Member] | PUCO [Member] | Maximum [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rider Revenue Increase	10
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
Approved Rate Increase (Decrease), One Time Waiver Amount						56
Duke Energy Ohio [Member] | Natural Gas Pipeline Extension [Member] | OPSB [Member]
Public Utilities, General Disclosures [Line Items]
Estimated Capital Cost Excluding AFUDC						112
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%
Requested Rate Increase (Decrease), Amended, Amount						$ 30.1
Requested Rate Increase (Decrease), Amended, Percentage						9.00%
Duke Energy Ohio [Member] | Duke Energy Kentucky Rate Case [Member] | Subsequent Event [Member] | KPSC [Member]
Public Utilities, General Disclosures [Line Items]
Approved Rate Increase (Decrease), Amount	$ 8.4
Approved return on equity percentage	9.725%
Public Utilities, Approved Equity Capital Structure, Percentage	49.00%
Total Allocable Capitalization	$ 650
Costs recovered through existing riders	50
Incremental Rider Revenue	$ 13
Duke Energy Indiana [Member]
Public Utilities, General Disclosures [Line Items]
Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses						$ 181	176
Public Utilities, Property, Plant and Equipment, Net						10,345		10,286
Loss Before Income Taxes						$ (135)	(150)
Duke Energy Indiana [Member] | Benton County Wind Farm Dispute [Member]
Public Utilities, General Disclosures [Line Items]
Litigation Settlement, Amount Awarded to Other Party				$ 29
Duke Energy Indiana [Member] | 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%
Piedmont Natural Gas [Member]
Public Utilities, General Disclosures [Line Items]
Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses						$ 82	77
Public Utilities, Property, Plant and Equipment, Net						5,361		$ 5,246
Loss Before Income Taxes						(145)	$ (153)
Piedmont Natural Gas [Member] | TPUC IMR Petition Filed November 2017 [Member] | TPUC [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount						3.3
Requested Rate Increase (Decrease), Amended, Amount						0.4
Storm Costs [Member] | Duke Energy Florida [Member] | Storm Restoration Cost Recovery [Member] | FPSC [Member]
Public Utilities, General Disclosures [Line Items]
Allowed Storm Reserve						$ 132

Regulatory Matters (Schedule of

Regulatory Matters (Schedule of Net Carrying Value Of Facilities and Megawatt Capacity) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)MW	Dec. 31, 2017USD ($)
Public Utilities, General Disclosures [Line Items]
Public Utilities, Property, Plant and Equipment, Net	$ 87,373	$ 86,391
Duke Energy Carolinas [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Property, Plant and Equipment, Net	28,158	27,876
Progress Energy [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Property, Plant and Equipment, Net	32,254	31,887
Duke Energy Florida [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Property, Plant and Equipment, Net	12,998	12,783
Duke Energy Indiana [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Property, Plant and Equipment, Net	$ 10,345	$ 10,286
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	$ 391
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	$ 161
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	$ 104
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	$ 104
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	$ 126

Commitments and Contingencies50

Commitments and Contingencies (Narrative) (Details)	3 Months Ended
	Mar. 31, 2018USD ($)plantclaimT	Dec. 31, 2017USD ($)
Valuation and Qualifying Accounts [Abstract]
Loss Contingency Accrual	$ 74,000,000	$ 88,000,000
Coal Ash Insurance Coverage Litigation [Member]
Valuation and Qualifying Accounts [Abstract]
Number of NC and SC Plants with Ash Basins | plant	15
NCDEQ State Enforcement Actions [Member]
Valuation and Qualifying Accounts [Abstract]
Number of Plants with No Disputed Facts | plant	7
Number of NC Plants with Ash Basins | plant	14
Number of Plants with Disputed Facts | plant	7
Groundwater Contamination Claims [Member]
Valuation and Qualifying Accounts [Abstract]
Goodwill Payment	$ 5,000
Water Bill Stipend Period	25 years
Duke Energy Carolinas [Member]
Valuation and Qualifying Accounts [Abstract]
Loss Contingency Accrual	$ 20,000,000	30,000,000
Duke Energy Carolinas [Member] | Groundwater Contamination Claims [Member]
Valuation and Qualifying Accounts [Abstract]
Loss Contingency Accrual	16,000,000
Duke Energy Carolinas [Member] | Asbestos-related Injuries and Damages Claims [Member]
Valuation and Qualifying Accounts [Abstract]
Asbestos-related injuries and damages reserves	487,000,000	489,000,000
Reinsurance retention policy, excess retention, amount reinsured	797,000,000
Probable insurance recoveries	$ 585,000,000	585,000,000
Duke Energy Carolinas [Member] | Asbestos-related Injuries and Damages Claims [Member] | Non-Malignant Asbestos Claim [Member]
Valuation and Qualifying Accounts [Abstract]
Loss contingency, pending claims, number | claim	143
Asbestos-related injuries and damages reserves	$ 37,000,000
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	58
Asbestos-related injuries and damages reserves	$ 19,000,000
Progress Energy [Member]
Valuation and Qualifying Accounts [Abstract]
Loss Contingency Accrual	51,000,000	55,000,000
Duke Energy Progress [Member]
Valuation and Qualifying Accounts [Abstract]
Loss Contingency Accrual	10,000,000	13,000,000
Duke Energy Progress [Member] | Groundwater Contamination Claims [Member]
Valuation and Qualifying Accounts [Abstract]
Loss Contingency Accrual	3,000,000
Duke Energy Progress [Member] | Spent Nuclear Fuels [Member]
Valuation and Qualifying Accounts [Abstract]
Gain Contingency, Unrecorded Amount	48,000,000
Litigation Settlement, Amount Awarded from Other Party	$ 48,000,000
Duke Energy Progress [Member] | Gypsum Supply Agreements [Member]
Valuation and Qualifying Accounts [Abstract]
Minimum Amount of Gypsum To Be Supplied | T	50,000
Duke Energy Florida [Member]
Valuation and Qualifying Accounts [Abstract]
Loss Contingency Accrual	$ 24,000,000	$ 24,000,000
Duke Energy Florida [Member] | Spent Nuclear Fuels [Member]
Valuation and Qualifying Accounts [Abstract]
Gain Contingency, Unrecorded Amount	25,000,000
Litigation Settlement, Amount Awarded from Other Party	21,000,000
Duke Energy Florida [Member] | Westinghouse Electric Company Litigation [Member]
Valuation and Qualifying Accounts [Abstract]
Gain Contingency, Unrecorded Amount	54,000,000
Loss Contingency, Damages Sought, Original Amount	510,000,000
Loss Contingency, Damages Awarded, Value	30,000,000
Gain Contingency, Dismissed Amount	54,000,000
Loss Contingency Damages Awarded and Interest, Value	34,000,000
Duke Energy Florida [Member] | MGP Cost Recovery Action [Member]
Valuation and Qualifying Accounts [Abstract]
Gain Contingency, Unrecorded Amount	$ 43,000,000

Commitments and Contingencies51

Commitments and Contingencies (Schedule of Environmental Loss Contingencies) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	$ 57
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	81	$ 98
Provisions/adjustments	4	6
Cash reductions	(5)	(6)
Ending balance	80	98
Duke Energy Carolinas [Member]
Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	19
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	10	10
Provisions/adjustments	1	1
Cash reductions	0
Ending balance	11	11
Progress Energy [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	15	18
Provisions/adjustments	3
Cash reductions	(2)	(1)
Ending balance	16	17
Duke Energy Progress [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	3	3
Provisions/adjustments	1
Cash reductions	(1)
Ending balance	3	3
Duke Energy Florida [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	12	14
Provisions/adjustments	1	1
Cash reductions	(1)	(1)
Ending balance	12	14
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	47	59
Provisions/adjustments		4
Cash reductions	(3)	(4)
Ending balance	44	59
Duke Energy Indiana [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	5	10
Provisions/adjustments	1	(1)
Cash reductions	0
Ending balance	6	9
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	2	1
Provisions/adjustments		1
Cash reductions	0
Ending balance	$ 2	$ 2

Commitments and Contingencies52

Commitments and Contingencies (Schedule of Legal Reserves) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Loss Contingencies [Line Items]
Reserves for legal matters	$ 74	$ 88
Duke Energy Carolinas [Member]
Loss Contingencies [Line Items]
Reserves for legal matters	20	30
Progress Energy [Member]
Loss Contingencies [Line Items]
Reserves for legal matters	51	55
Duke Energy Progress [Member]
Loss Contingencies [Line Items]
Reserves for legal matters	10	13
Duke Energy Florida [Member]
Loss Contingencies [Line Items]
Reserves for legal matters	24	24
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 ($)	May 10, 2018	Mar. 31, 2018
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Facility size		$ 8,000,000,000
Revolving Credit Facility [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Expiration Date	Mar. 16, 2023
Three Year Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Facility size		1,000,000,000
Long-term Line of Credit		500,000,000
Duke Energy Carolinas [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Facility size		1,550,000,000
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 ($)	Mar. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Debt issuances	$ 1,250,000,000
Current maturities of long-term debt	3,951,000,000	$ 3,244,000,000
Parent Company [Member]
Debt Instrument [Line Items]
Debt issuances	250,000,000
Duke Energy Carolinas [Member]
Debt Instrument [Line Items]
Debt issuances	1,000,000,000
Current maturities of long-term debt	805,000,000	$ 1,205,000,000
Duke Energy Carolinas [Member] | Bonds Maturing April 2018, 5.100% Coupon [Member]
Debt Instrument [Line Items]
Current maturities of long-term debt	300,000,000
Unsecured Debt [Member] | March 2018 Debt Issuance 3.950% Coupon Due 2025 [Member]
Debt Instrument [Line Items]
Debt issuances	$ 250,000,000
Interest rate	3.95%
Unsecured Debt [Member] | Parent Company [Member] | March 2018 Debt Issuance 3.950% Coupon Due 2025 [Member]
Debt Instrument [Line Items]
Debt issuances	$ 250,000,000
First Mortgage [Member] | March 2018 Debt Issuance 3.050% Coupon [Member]
Debt Instrument [Line Items]
Debt issuances	$ 500,000,000
Interest rate	3.05%
First Mortgage [Member] | March 2018 Debt Issuance 3.950% Coupon Due 2048 [Member]
Debt Instrument [Line Items]
Debt issuances	$ 500,000,000
Interest rate	3.95%
First Mortgage [Member] | Duke Energy Carolinas [Member] | March 2018 Debt Issuance 3.050% Coupon [Member]
Debt Instrument [Line Items]
Debt issuances	$ 500,000,000
First Mortgage [Member] | Duke Energy Carolinas [Member] | March 2018 Debt Issuance 3.950% Coupon Due 2048 [Member]
Debt Instrument [Line Items]
Debt issuances	$ 500,000,000
First Mortgage [Member] | Duke Energy Carolinas [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

Debt and Credit Facilities (S55

Debt and Credit Facilities (Summary of Current Maturities of Long-term Debt)(Details) - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Current maturities of long-term debt	$ 3,951,000,000	$ 3,244,000,000
Other Debt Obligations [Member]
Debt Instrument [Line Items]
Current maturities of long-term debt	$ 601,000,000
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
Piedmont Natural Gas [Member]
Debt Instrument [Line Items]
Current maturities of long-term debt	$ 250,000,000	250,000,000
Piedmont Natural Gas [Member] | Unsecured Debt [Member] | Debt Maturing December 2018, Floating Rate [Member]
Debt Instrument [Line Items]
Interest rate	2.821%
Current maturities of long-term debt	$ 250,000,000
Progress Energy [Member]
Debt Instrument [Line Items]
Current maturities of long-term debt	$ 1,820,000,000	771,000,000
Progress Energy [Member] | Unsecured Debt [Member] | Debt Maturing March 2019, 7.050% Coupon [Member]
Debt Instrument [Line Items]
Interest rate	7.05%
Current maturities of long-term debt	$ 450,000,000
Duke Energy Carolinas [Member]
Debt Instrument [Line Items]
Current maturities of long-term debt	805,000,000	1,205,000,000
Duke Energy Carolinas [Member] | Bonds Maturing April 2018, 5.100% Coupon [Member]
Debt Instrument [Line Items]
Current maturities of long-term debt	$ 300,000,000
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 Carolinas [Member] | First Mortgage Bonds [Member] | Bonds Maturing November 2018, 7.000% Coupon [Member]
Debt Instrument [Line Items]
Interest rate	7.00%
Current maturities of long-term debt	$ 500,000,000
Duke Energy Florida [Member]
Debt Instrument [Line Items]
Current maturities of long-term debt	$ 768,000,000	768,000,000
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
Duke Energy Progress [Member]
Debt Instrument [Line Items]
Current maturities of long-term debt	$ 603,000,000	$ 3,000,000
Duke Energy Progress [Member] | First Mortgage Bonds [Member] | Bonds Maturing January 2019, 5.300% Coupon [Member]
Debt Instrument [Line Items]
Interest rate	5.30%
Current maturities of long-term debt	$ 600,000,000

Debt and Credit Facilities (Sch

Debt and Credit Facilities (Schedule of Line of Credit Facilities) (Details) - Revolving Credit Facility [Member]	Mar. 31, 2018USD ($)
Line of Credit Facility [Line Items]
Facility size	$ 8,000,000,000
Commercial paper	(2,602,000,000)
Outstanding letters of credit	(59,000,000)
Tax exempt bonds	(81,000,000)
Coal ash set-aside	(500,000,000)
Available capacity	4,758,000,000
Parent Company [Member]
Line of Credit Facility [Line Items]
Facility size	2,650,000,000
Commercial paper	(1,281,000,000)
Outstanding letters of credit	(50,000,000)
Available capacity	1,319,000,000
Duke Energy Carolinas [Member]
Line of Credit Facility [Line Items]
Facility size	1,550,000,000
Commercial paper	(340,000,000)
Outstanding letters of credit	(4,000,000)
Coal ash set-aside	(250,000,000)
Available capacity	956,000,000
Duke Energy Progress [Member]
Line of Credit Facility [Line Items]
Facility size	1,250,000,000
Commercial paper	(464,000,000)
Outstanding letters of credit	(2,000,000)
Coal ash set-aside	(250,000,000)
Available capacity	534,000,000
Duke Energy Florida [Member]
Line of Credit Facility [Line Items]
Facility size	800,000,000
Outstanding letters of credit	(1,000,000)
Available capacity	799,000,000
Duke Energy Ohio [Member]
Line of Credit Facility [Line Items]
Facility size	450,000,000
Commercial paper	(140,000,000)
Available capacity	310,000,000
Duke Energy Indiana [Member]
Line of Credit Facility [Line Items]
Facility size	600,000,000
Commercial paper	(282,000,000)
Tax exempt bonds	(81,000,000)
Available capacity	237,000,000
Piedmont Natural Gas [Member]
Line of Credit Facility [Line Items]
Facility size	700,000,000
Commercial paper	(95,000,000)
Outstanding letters of credit	(2,000,000)
Available capacity	603,000,000
Proceeds Loaned To Subsidiary Registrants [Member] | Parent Company [Member]
Line of Credit Facility [Line Items]
Commercial paper	$ (625,000,000)

Goodwill (Details)

Goodwill (Details) - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Goodwill [Line Items]
Goodwill balance	$ 19,425,000,000	$ 19,425,000,000
Accumulated impairment charges	(29,000,000)	(29,000,000)
Goodwill, adjusted for accumulated impairment charges	19,396,000,000	19,396,000,000
Electric Utilities and Infrastructure [Member]
Goodwill [Line Items]
Goodwill balance	17,379,000,000	17,379,000,000
Goodwill, adjusted for accumulated impairment charges	17,379,000,000	17,379,000,000
Gas Utilities and Infrastructure [Member]
Goodwill [Line Items]
Goodwill balance	1,924,000,000	1,924,000,000
Goodwill, adjusted for accumulated impairment charges	1,924,000,000	1,924,000,000
Commercial Renewables [Member]
Goodwill [Line Items]
Goodwill balance	122,000,000	122,000,000
Accumulated impairment charges	(29,000,000)	(29,000,000)
Goodwill, adjusted for accumulated impairment charges	93,000,000	93,000,000
Duke Energy Ohio [Member]
Goodwill [Line Items]
Accumulated impairment charges	(216,000,000)	(216,000,000)
Goodwill, adjusted for accumulated impairment charges	920,000,000	920,000,000
Duke Energy Ohio [Member] | Electric Utilities and Infrastructure [Member]
Goodwill [Line Items]
Goodwill, adjusted for accumulated impairment charges	596,000,000	596,000,000
Duke Energy Ohio [Member] | Gas Utilities and Infrastructure [Member]
Goodwill [Line Items]
Goodwill, adjusted for accumulated impairment charges	324,000,000	324,000,000
Progress Energy [Member]
Goodwill [Line Items]
Accumulated impairment charges	0	0
Goodwill, adjusted for accumulated impairment charges	3,655,000,000	3,655,000,000
Piedmont Natural Gas [Member]
Goodwill [Line Items]
Accumulated impairment charges	0	0
Goodwill, adjusted for accumulated impairment charges	$ 49,000,000	$ 49,000,000

Related Party Transactions (Oth

Related Party Transactions (Other Revenue and Expense) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Duke Energy Carolinas [Member] | Corporate Governance And Shared Service Expenses [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	$ 220	$ 221
Duke Energy Carolinas [Member] | Indemnification Coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	6	6
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	34	16
Related party transaction, expenses from transactions with related party	54	31
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	4	1
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	191	170
Progress Energy [Member] | Indemnification Coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	8	10
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	54	31
Related party transaction, expenses from transactions with related party	34	16
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	19
Duke Energy Progress [Member] | Corporate Governance And Shared Service Expenses [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	118	100
Duke Energy Progress [Member] | Indemnification Coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	3	4
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	54	31
Related party transaction, expenses from transactions with related party	34	16
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	19
Duke Energy Florida [Member] | Corporate Governance And Shared Service Expenses [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	73	70
Duke Energy Florida [Member] | Indemnification Coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	5	6
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	89	92
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
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	101	95
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
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	36	5
Piedmont Natural Gas [Member] | Indemnification Coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	1	1
Piedmont Natural Gas [Member] | Intercompany Natural Gas Transactions [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, other revenues from transactions with related party	$ 23	$ 20

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
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	$ 6	$ 6
Accounts Payable, Related Parties, Current	2		$ 2
Cardinal Pipeline Company, LLC [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	2	2
Pine Needle LNG Company, LLC [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	2	2
Hardy Storage Company, LLC [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	$ 2	$ 2

Related Party Transactions (Int

Related Party Transactions (Intercompany Income Taxes) (Details) - Affiliated Entity [Member] - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Duke Energy Carolinas [Member]
Related Party Transaction [Line Items]
Income tax payable	$ 9	$ 44
Progress Energy [Member]
Related Party Transaction [Line Items]
Income taxes receivable	183	168
Duke Energy Progress [Member]
Related Party Transaction [Line Items]
Income taxes receivable	13
Income tax payable		21
Duke Energy Florida [Member]
Related Party Transaction [Line Items]
Income taxes receivable	9	44
Duke Energy Ohio [Member]
Related Party Transaction [Line Items]
Income taxes receivable		22
Income tax payable	3
Duke Energy Indiana [Member]
Related Party Transaction [Line Items]
Income tax payable	18	35
Piedmont Natural Gas [Member]
Related Party Transaction [Line Items]
Income taxes receivable		$ 7
Income tax payable	$ 43

Derivatives and Hedging (Notion

Derivatives and Hedging (Notional Amounts of Derivative Instruments) (Details) Mcf in Millions, $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2018USD ($)GWhMcf	Dec. 31, 2017USD ($)GWhMcf
Commodity Contracts [Member] | Electricity [Member]
Derivative [Line Items]
Notional amount, energy measure, in gigawatt-hours | GWh	16	34
Commodity Contracts [Member] | Natural Gas [Member]
Derivative [Line Items]
Notional amount, volume, in millions of decatherms | Mcf	765	770
Interest Rate Contracts [Member]
Derivative [Line Items]
Notional amount	$ 1,187	$ 1,587
Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Notional amount	660	660
Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Notional amount	527	927
Variable Interest Entity, Primary Beneficiary [Member] | Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Notional amount	$ 660	$ 660
Duke Energy Carolinas [Member] | Commodity Contracts [Member] | Natural Gas [Member]
Derivative [Line Items]
Notional amount, volume, in millions of decatherms | Mcf	110	105
Duke Energy Carolinas [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Notional amount		$ 400
Duke Energy Carolinas [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Notional amount		$ 400
Progress Energy [Member] | Commodity Contracts [Member] | Natural Gas [Member]
Derivative [Line Items]
Notional amount, volume, in millions of decatherms | Mcf	179	183
Progress Energy [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Notional amount	$ 500	$ 500
Progress Energy [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Notional amount	$ 500	$ 500
Duke Energy Progress [Member] | Commodity Contracts [Member] | Natural Gas [Member]
Derivative [Line Items]
Notional amount, volume, in millions of decatherms | Mcf	149	133
Duke Energy Progress [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Notional amount	$ 250	$ 250
Duke Energy Progress [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Notional amount	$ 250	$ 250
Duke Energy Florida [Member] | Commodity Contracts [Member] | Natural Gas [Member]
Derivative [Line Items]
Notional amount, volume, in millions of decatherms | Mcf	30	50
Duke Energy Florida [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Notional amount	$ 250	$ 250
Duke Energy Florida [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Notional amount	250	250
Duke Energy Ohio [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Notional amount	27	27
Duke Energy Ohio [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Notional amount	$ 27	$ 27
Duke Energy Indiana [Member] | Commodity Contracts [Member] | Electricity [Member]
Derivative [Line Items]
Notional amount, energy measure, in gigawatt-hours | GWh	16	34
Duke Energy Indiana [Member] | Commodity Contracts [Member] | Natural Gas [Member]
Derivative [Line Items]
Notional amount, volume, in millions of decatherms | Mcf	2	2
Piedmont Natural Gas [Member] | Commodity Contracts [Member] | Natural Gas [Member]
Derivative [Line Items]
Notional amount, volume, in millions of decatherms | Mcf	474	480

Derivatives and Hedging (Locati

Derivatives and Hedging (Location and Fair Value Amounts of Derivatives Reflected in the Condensed Consolidated Balance Sheets) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	$ 37	$ 51
Location and fair value amounts of derivatives (Liability)	190	230
Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	15	35
Noncurrent Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	22	16
Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	33	66
Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	157	164
Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	15	35
Location and fair value amounts of derivatives (Liability)	166	182
Interest Rate Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	22	16
Location and fair value amounts of derivatives (Liability)	24	48
Designated As Hedging Instrument [Member] | Interest Rate Contracts [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	1
Designated As Hedging Instrument [Member] | Interest Rate Contracts [Member] | Noncurrent Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	21	15
Designated As Hedging Instrument [Member] | Interest Rate Contracts [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	4	29
Designated As Hedging Instrument [Member] | Interest Rate Contracts [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	3	6
Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	14	34
Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Noncurrent Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	1
Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	26	36
Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	140	146
Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	3	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)	14	12
Duke Energy Carolinas [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	2	2
Location and fair value amounts of derivatives (Liability)	11	35
Duke Energy Carolinas [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	2	2
Duke Energy Carolinas [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	5	31
Duke Energy Carolinas [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	6	4
Duke Energy Carolinas [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	2	2
Location and fair value amounts of derivatives (Liability)	11	10
Duke Energy Carolinas [Member] | Interest Rate Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)		25
Duke Energy Carolinas [Member] | Designated As Hedging Instrument [Member] | Interest Rate Contracts [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)		25
Duke Energy Carolinas [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	2	2
Duke Energy Carolinas [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	5	6
Duke Energy Carolinas [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	6	4
Progress Energy [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	3	3
Location and fair value amounts of derivatives (Liability)	37	36
Progress Energy [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	3	2
Progress Energy [Member] | Noncurrent Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)		1
Progress Energy [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	11	19
Progress Energy [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	26	17
Progress Energy [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	3	3
Location and fair value amounts of derivatives (Liability)	23	28
Progress Energy [Member] | Interest Rate Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	14	8
Progress Energy [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	3	2
Progress Energy [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Noncurrent Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)		1
Progress Energy [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	8	18
Progress Energy [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	15	10
Progress Energy [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	3	1
Progress Energy [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	11	7
Duke Energy Progress [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	2	2
Location and fair value amounts of derivatives (Liability)	21	18
Duke Energy Progress [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	2	1
Duke Energy Progress [Member] | Noncurrent Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)		1
Duke Energy Progress [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	8	8
Duke Energy Progress [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	13	10
Duke Energy Progress [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	2	2
Location and fair value amounts of derivatives (Liability)	12	12
Duke Energy Progress [Member] | Interest Rate Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	9	6
Duke Energy Progress [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	2	1
Duke Energy Progress [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Noncurrent Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	0	1
Duke Energy Progress [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	6	8
Duke Energy Progress [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	6	4
Duke Energy Progress [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	2
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)	7	6
Duke Energy Florida [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	1
Location and fair value amounts of derivatives (Liability)	7	12
Duke Energy Florida [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	1
Duke Energy Florida [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	4	10
Duke Energy Florida [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	3	2
Duke Energy Florida [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	1
Location and fair value amounts of derivatives (Liability)	3	10
Duke Energy Florida [Member] | Interest Rate Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	4	2
Duke Energy Florida [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	1
Duke Energy Florida [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	3	10
Duke Energy Florida [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	1
Duke Energy Florida [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	3	2
Duke Energy Ohio [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	1
Location and fair value amounts of derivatives (Liability)	4	5
Duke Energy Ohio [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	1
Duke Energy Ohio [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)		1
Duke Energy Ohio [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	4	4
Duke Energy Ohio [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	1
Duke Energy Ohio [Member] | Interest Rate Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	4	5
Duke Energy Ohio [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	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
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	4
Duke Energy Indiana [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	7	27
Duke Energy Indiana [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	7	27
Duke Energy Indiana [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	7	27
Duke Energy Indiana [Member] | Designated As Hedging Instrument [Member] | Interest Rate Contracts [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)		0
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)	7	27
Piedmont Natural Gas [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	2
Location and fair value amounts of derivatives (Liability)	132	142
Piedmont Natural Gas [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	2
Piedmont Natural Gas [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	13	11
Piedmont Natural Gas [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	119	131
Piedmont Natural Gas [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	2
Location and fair value amounts of derivatives (Liability)	132	142
Piedmont Natural Gas [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Current Assets, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Asset)	1	2
Piedmont Natural Gas [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Current Liabilities, Other [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	13	11
Piedmont Natural Gas [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Location and fair value amounts of derivatives (Liability)	$ 119	$ 131

Derivatives and Hedging (Schedu

Derivatives and Hedging (Schedule of Offsetting Assets) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	$ 37	$ 51
Net amounts recognized on the Condensed Consolidated Balance Sheet	37	51
Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	15	35
Gross amounts offset	(2)
Net amounts recognized on the Condensed Consolidated Balance Sheet	13	35
Noncurrent Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	22	16
Net amounts recognized on the Condensed Consolidated Balance Sheet	22	16
Duke Energy Carolinas [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	2	2
Net amounts recognized on the Condensed Consolidated Balance Sheet	2	2
Duke Energy Carolinas [Member] | Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	2	2
Gross amounts offset	(1)
Net amounts recognized on the Condensed Consolidated Balance Sheet	1	2
Progress Energy [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	3	3
Net amounts recognized on the Condensed Consolidated Balance Sheet	3	3
Progress Energy [Member] | Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	3	2
Gross amounts offset	(1)
Net amounts recognized on the Condensed Consolidated Balance Sheet	2	2
Progress Energy [Member] | Noncurrent Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized		1
Net amounts recognized on the Condensed Consolidated Balance Sheet		1
Duke Energy Progress [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	2	2
Net amounts recognized on the Condensed Consolidated Balance Sheet	2	2
Duke Energy Progress [Member] | Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	2	1
Gross amounts offset	(1)
Net amounts recognized on the Condensed Consolidated Balance Sheet	1	1
Duke Energy Progress [Member] | Noncurrent Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized		1
Net amounts recognized on the Condensed Consolidated Balance Sheet		1
Duke Energy Florida [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	1	1
Net amounts recognized on the Condensed Consolidated Balance Sheet	1	1
Duke Energy Florida [Member] | Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	1	1
Net amounts recognized on the Condensed Consolidated Balance Sheet	1	1
Duke Energy Ohio [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	1	1
Net amounts recognized on the Condensed Consolidated Balance Sheet	1	1
Duke Energy Ohio [Member] | Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	1	1
Net amounts recognized on the Condensed Consolidated Balance Sheet	1	1
Duke Energy Indiana [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	7	27
Net amounts recognized on the Condensed Consolidated Balance Sheet	7	27
Duke Energy Indiana [Member] | Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	7	27
Net amounts recognized on the Condensed Consolidated Balance Sheet	7	27
Piedmont Natural Gas [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	1	2
Net amounts recognized on the Condensed Consolidated Balance Sheet	1	2
Piedmont Natural Gas [Member] | Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	1	2
Net amounts recognized on the Condensed Consolidated Balance Sheet	$ 1	$ 2

Derivatives and Hedging (Sche64

Derivatives and Hedging (Schedule of Offsetting Liabilities) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	$ 190	$ 230
Net amounts recognized on the Condensed Consolidated Balance Sheet	190	230
Other Current Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	33	66
Gross amounts offset	(4)	(3)
Net amounts recognized on the Condensed Consolidated Balance Sheet	29	63
Other Noncurrent Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	157	164
Gross amounts offset	(1)	(1)
Net amounts recognized on the Condensed Consolidated Balance Sheet	156	163
Duke Energy Carolinas [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	11	35
Net amounts recognized on the Condensed Consolidated Balance Sheet	11	35
Duke Energy Carolinas [Member] | Other Current Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	5	31
Gross amounts offset	(2)	(2)
Net amounts recognized on the Condensed Consolidated Balance Sheet	3	29
Duke Energy Carolinas [Member] | Other Noncurrent Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	6	4
Net amounts recognized on the Condensed Consolidated Balance Sheet	6	4
Progress Energy [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	37	36
Net amounts recognized on the Condensed Consolidated Balance Sheet	37	36
Progress Energy [Member] | Other Current Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	11	19
Gross amounts offset	(2)	(2)
Net amounts recognized on the Condensed Consolidated Balance Sheet	9	17
Progress Energy [Member] | Other Noncurrent Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	26	17
Gross amounts offset	(1)	(1)
Net amounts recognized on the Condensed Consolidated Balance Sheet	25	16
Duke Energy Progress [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	21	18
Net amounts recognized on the Condensed Consolidated Balance Sheet	21	18
Duke Energy Progress [Member] | Other Current Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	8	8
Gross amounts offset	(2)	(2)
Net amounts recognized on the Condensed Consolidated Balance Sheet	6	6
Duke Energy Progress [Member] | Other Noncurrent Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	13	10
Gross amounts offset	(1)	(1)
Net amounts recognized on the Condensed Consolidated Balance Sheet	12	9
Duke Energy Florida [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	7	12
Net amounts recognized on the Condensed Consolidated Balance Sheet	7	12
Duke Energy Florida [Member] | Other Current Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	4	10
Net amounts recognized on the Condensed Consolidated Balance Sheet	4	10
Duke Energy Florida [Member] | Other Noncurrent Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	3	2
Net amounts recognized on the Condensed Consolidated Balance Sheet	3	2
Duke Energy Ohio [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	4	5
Net amounts recognized on the Condensed Consolidated Balance Sheet	4	5
Duke Energy Ohio [Member] | Other Current Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized		1
Net amounts recognized on the Condensed Consolidated Balance Sheet		1
Duke Energy Ohio [Member] | Other Noncurrent Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	4	4
Net amounts recognized on the Condensed Consolidated Balance Sheet	4	4
Piedmont Natural Gas [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	132	142
Net amounts recognized on the Condensed Consolidated Balance Sheet	132	142
Piedmont Natural Gas [Member] | Other Current Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	13	11
Net amounts recognized on the Condensed Consolidated Balance Sheet	13	11
Piedmont Natural Gas [Member] | Other Noncurrent Liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	119	131
Net amounts recognized on the Condensed Consolidated Balance Sheet	$ 119	$ 131

Derivatives and Hedging (Deriva

Derivatives and Hedging (Derivative Instruments with Credit-Risk Related Contingent Features and Cash Collateral) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Schedule of Information Regarding Derivative Instruments That Contain Credit-Risk Related Contingent Features
Aggregate fair value amounts of derivative instruments in a net liability position	$ 30	$ 59
Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered	30	59
Duke Energy Carolinas [Member]
Schedule of Information Regarding Derivative Instruments That Contain Credit-Risk Related Contingent Features
Aggregate fair value amounts of derivative instruments in a net liability position	10	35
Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered	10	35
Progress Energy [Member]
Schedule of Information Regarding Derivative Instruments That Contain Credit-Risk Related Contingent Features
Aggregate fair value amounts of derivative instruments in a net liability position	20	25
Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered	20	25
Duke Energy Progress [Member]
Schedule of Information Regarding Derivative Instruments That Contain Credit-Risk Related Contingent Features
Aggregate fair value amounts of derivative instruments in a net liability position	18	15
Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered	18	15
Duke Energy Florida [Member]
Schedule of Information Regarding Derivative Instruments That Contain Credit-Risk Related Contingent Features
Aggregate fair value amounts of derivative instruments in a net liability position	2	10
Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered	$ 2	$ 10

Investments in Debt and Equit66

Investments in Debt and Equity Securities (All Debt and Equity Securities Through OCI and FV-NI - ASU 2016-01) (Details) $ in Millions	Mar. 31, 2018USD ($)
Schedule Of Available For Sale Securities And Other Trading Assets [Line Items]
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Gain	$ 2,823
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Loss	74
Debt Securities, Available-for-sale, and Equity Securities, FV-NI	7,414
Ndtf [Member]
Schedule Of Available For Sale Securities And Other Trading Assets [Line Items]
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Gain	2,765
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Loss	71
Cash and cash equivalents	143
Debt Securities, Available-for-sale, and Equity Securities, FV-NI	7,026
Other Classification [Member]
Schedule Of Available For Sale Securities And Other Trading Assets [Line Items]
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Gain	58
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Loss	3
Cash and cash equivalents	15
Debt Securities, Available-for-sale, and Equity Securities, FV-NI	388
Duke Energy Carolinas [Member] | Ndtf [Member]
Schedule Of Available For Sale Securities And Other Trading Assets [Line Items]
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Gain	1,507
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Loss	39
Cash and cash equivalents	50
Debt Securities, Available-for-sale, and Equity Securities, FV-NI	3,737
Progress Energy [Member]
Schedule Of Available For Sale Securities And Other Trading Assets [Line Items]
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Gain	1,259
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Loss	32
Debt Securities, Available-for-sale, and Equity Securities, FV-NI	3,346
Progress Energy [Member] | Ndtf [Member]
Schedule Of Available For Sale Securities And Other Trading Assets [Line Items]
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Gain	1,258
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Loss	32
Cash and cash equivalents	93
Debt Securities, Available-for-sale, and Equity Securities, FV-NI	3,289
Progress Energy [Member] | Other Classification [Member]
Schedule Of Available For Sale Securities And Other Trading Assets [Line Items]
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Gain	1
Cash and cash equivalents	10
Debt Securities, Available-for-sale, and Equity Securities, FV-NI	57
Duke Energy Progress [Member]
Schedule Of Available For Sale Securities And Other Trading Assets [Line Items]
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Gain	966
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Loss	25
Debt Securities, Available-for-sale, and Equity Securities, FV-NI	2,572
Duke Energy Progress [Member] | Ndtf [Member]
Schedule Of Available For Sale Securities And Other Trading Assets [Line Items]
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Gain	966
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Loss	25
Cash and cash equivalents	59
Debt Securities, Available-for-sale, and Equity Securities, FV-NI	2,571
Duke Energy Progress [Member] | Other Classification [Member]
Schedule Of Available For Sale Securities And Other Trading Assets [Line Items]
Cash and cash equivalents	1
Debt Securities, Available-for-sale, and Equity Securities, FV-NI	1
Duke Energy Florida [Member]
Schedule Of Available For Sale Securities And Other Trading Assets [Line Items]
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Gain	293
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Loss	7
Debt Securities, Available-for-sale, and Equity Securities, FV-NI	765
Duke Energy Florida [Member] | Ndtf [Member]
Schedule Of Available For Sale Securities And Other Trading Assets [Line Items]
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Gain	292
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Loss	7
Cash and cash equivalents	34
Debt Securities, Available-for-sale, and Equity Securities, FV-NI	718
Duke Energy Florida [Member] | Other Classification [Member]
Schedule Of Available For Sale Securities And Other Trading Assets [Line Items]
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Gain	1
Debt Securities, Available-for-sale, and Equity Securities, FV-NI	47
Duke Energy Indiana [Member]
Schedule Of Available For Sale Securities And Other Trading Assets [Line Items]
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Gain	48
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Loss	1
Debt Securities, Available-for-sale, and Equity Securities, FV-NI	$ 127

Investments in Debt and Equit67

Investments in Debt and Equity Securities (Equity Securities, FV-NI - ASU 2016-01) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)
Equity Securities, FV-NI, Realized Gain (Loss) [Abstract]
Equity Securities, FV-NI, Realized Gain	$ 19
Equity Securities, FV-NI, Realized Loss	13
Ndtf [Member]
EquitySecuritiesFvNiAccumulatedUnrealizedGainLoss [Abstract]
Equity Securities, FV-NI, Unrealized Gain	2,751
Equity Securities, FV-NI, Unrealized Loss	38
Equity Securities, FV-NI	4,857
Other Classification [Member]
EquitySecuritiesFvNiAccumulatedUnrealizedGainLoss [Abstract]
Equity Securities, FV-NI, Unrealized Gain	57
Equity Securities, FV-NI	130
Duke Energy Carolinas [Member]
Equity Securities, FV-NI, Realized Gain (Loss) [Abstract]
Equity Securities, FV-NI, Realized Gain	10
Equity Securities, FV-NI, Realized Loss	5
Duke Energy Carolinas [Member] | Ndtf [Member]
EquitySecuritiesFvNiAccumulatedUnrealizedGainLoss [Abstract]
Equity Securities, FV-NI, Unrealized Gain	1,502
Equity Securities, FV-NI, Unrealized Loss	20
Equity Securities, FV-NI	2,669
Progress Energy [Member]
Equity Securities, FV-NI, Realized Gain (Loss) [Abstract]
Equity Securities, FV-NI, Realized Gain	9
Equity Securities, FV-NI, Realized Loss	8
Progress Energy [Member] | Ndtf [Member]
EquitySecuritiesFvNiAccumulatedUnrealizedGainLoss [Abstract]
Equity Securities, FV-NI, Unrealized Gain	1,249
Equity Securities, FV-NI, Unrealized Loss	18
Equity Securities, FV-NI	2,188
Duke Energy Progress [Member]
Equity Securities, FV-NI, Realized Gain (Loss) [Abstract]
Equity Securities, FV-NI, Realized Gain	8
Equity Securities, FV-NI, Realized Loss	8
Duke Energy Progress [Member] | Ndtf [Member]
EquitySecuritiesFvNiAccumulatedUnrealizedGainLoss [Abstract]
Equity Securities, FV-NI, Unrealized Gain	959
Equity Securities, FV-NI, Unrealized Loss	14
Equity Securities, FV-NI	1,765
Duke Energy Florida [Member]
Equity Securities, FV-NI, Realized Gain (Loss) [Abstract]
Equity Securities, FV-NI, Realized Gain	1
Duke Energy Florida [Member] | Ndtf [Member]
EquitySecuritiesFvNiAccumulatedUnrealizedGainLoss [Abstract]
Equity Securities, FV-NI, Unrealized Gain	290
Equity Securities, FV-NI, Unrealized Loss	4
Equity Securities, FV-NI	423
Duke Energy Indiana [Member]
EquitySecuritiesFvNiAccumulatedUnrealizedGainLoss [Abstract]
Equity Securities, FV-NI, Unrealized Gain	48
Equity Securities, FV-NI	96
Duke Energy Indiana [Member] | Other Classification [Member]
EquitySecuritiesFvNiAccumulatedUnrealizedGainLoss [Abstract]
Equity Securities, FV-NI	$ 96

Investments in Debt Securities

Investments in Debt Securities and Equity Securities (Available-for-sale, OCI - ASU 2016-01) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	$ 2,269
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract]
Debt Securities, Available-for-Sale, Realized Gain	5
Debt Securities, Available-for-sale, Realized Loss	13
Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	2,169
Other Classification [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	258
Corporate Debt Securities [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	7
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	8
Available-for-sale Securities, Debt Securities	549
Corporate Debt Securities [Member] | Other Classification [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1
Available-for-sale Securities, Debt Securities	64
Municipal Bonds [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	5
Available-for-sale Securities, Debt Securities	333
Municipal Bonds [Member] | Other Classification [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1
Available-for-sale Securities, Debt Securities	80
US Treasury and Government [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	6
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	18
Available-for-sale Securities, Debt Securities	1,014
US Treasury and Government [Member] | Other Classification [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1
Available-for-sale Securities, Debt Securities	51
Other Debt Obligations [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	2
Available-for-sale Securities, Debt Securities	130
Other Debt Obligations [Member] | Other Classification [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	48
Duke Energy Carolinas [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	1,018
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract]
Debt Securities, Available-for-Sale, Realized Gain	5
Debt Securities, Available-for-sale, Realized Loss	10
Duke Energy Carolinas [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	1,068
Duke Energy Carolinas [Member] | Corporate Debt Securities [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	3
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	5
Available-for-sale Securities, Debt Securities	333
Duke Energy Carolinas [Member] | Municipal Bonds [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1
Available-for-sale Securities, Debt Securities	69
Duke Energy Carolinas [Member] | US Treasury and Government [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	2
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	11
Available-for-sale Securities, Debt Securities	494
Duke Energy Carolinas [Member] | Other Debt Obligations [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	2
Available-for-sale Securities, Debt Securities	122
Progress Energy [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	1,055
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract]
Debt Securities, Available-for-sale, Realized Loss	3
Progress Energy [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	1,101
Progress Energy [Member] | Other Classification [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	57
Progress Energy [Member] | Corporate Debt Securities [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	4
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	3
Available-for-sale Securities, Debt Securities	216
Progress Energy [Member] | Municipal Bonds [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	4
Available-for-sale Securities, Debt Securities	264
Progress Energy [Member] | Municipal Bonds [Member] | Other Classification [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1
Available-for-sale Securities, Debt Securities	47
Progress Energy [Member] | US Treasury and Government [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	4
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	7
Available-for-sale Securities, Debt Securities	520
Progress Energy [Member] | Other Debt Obligations [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	8
Duke Energy Progress [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	747
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract]
Debt Securities, Available-for-sale, Realized Loss	2
Duke Energy Progress [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	806
Duke Energy Progress [Member] | Other Classification [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	1
Duke Energy Progress [Member] | Corporate Debt Securities [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	3
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	2
Available-for-sale Securities, Debt Securities	153
Duke Energy Progress [Member] | Municipal Bonds [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	4
Available-for-sale Securities, Debt Securities	263
Duke Energy Progress [Member] | US Treasury and Government [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	3
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	5
Available-for-sale Securities, Debt Securities	326
Duke Energy Progress [Member] | Other Debt Obligations [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	5
Duke Energy Florida [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	308
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract]
Debt Securities, Available-for-sale, Realized Loss	1
Duke Energy Florida [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	295
Duke Energy Florida [Member] | Other Classification [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	47
Duke Energy Florida [Member] | Corporate Debt Securities [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1
Available-for-sale Securities, Debt Securities	63
Duke Energy Florida [Member] | Municipal Bonds [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	1
Duke Energy Florida [Member] | Municipal Bonds [Member] | Other Classification [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1
Available-for-sale Securities, Debt Securities	47
Duke Energy Florida [Member] | US Treasury and Government [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	2
Available-for-sale Securities, Debt Securities	194
Duke Energy Florida [Member] | Other Debt Obligations [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	3
Duke Energy Indiana [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	31
Duke Energy Indiana [Member] | Other Classification [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	31
Duke Energy Indiana [Member] | Corporate Debt Securities [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	5
Duke Energy Indiana [Member] | Municipal Bonds [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1
Available-for-sale Securities, Debt Securities	$ 26

Investments in Debt and Equit69

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

Investments in Debt and Equit70

Investments in Debt and Equity Securities (Maturities) (Details) $ in Millions	Mar. 31, 2018USD ($)
Debt Instrument [Line Items]
Due in one year or less	$ 100
Due after one through five years	535
Due after five through 10 years	530
Due after 10 years	1,104
Total	2,269
Duke Energy Carolinas [Member]
Debt Instrument [Line Items]
Due in one year or less	11
Due after one through five years	178
Due after five through 10 years	285
Due after 10 years	544
Total	1,018
Progress Energy [Member]
Debt Instrument [Line Items]
Due in one year or less	75
Due after one through five years	300
Due after five through 10 years	198
Due after 10 years	482
Total	1,055
Duke Energy Progress [Member]
Debt Instrument [Line Items]
Due in one year or less	19
Due after one through five years	216
Due after five through 10 years	144
Due after 10 years	368
Total	747
Duke Energy Florida [Member]
Debt Instrument [Line Items]
Due in one year or less	56
Due after one through five years	84
Due after five through 10 years	54
Due after 10 years	114
Total	308
Duke Energy Indiana [Member]
Debt Instrument [Line Items]
Due in one year or less	3
Due after one through five years	15
Due after five through 10 years	6
Due after 10 years	7
Total	$ 31

Investments in Debt and Equit71

Investments in Debt and Equity Securities (Realized Gains and Losses)(Details) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2017USD ($)
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Realized gains	$ 93
Realized losses	62
Duke Energy Carolinas [Member]
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Realized gains	66
Realized losses	40
Progress Energy [Member]
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Realized gains	27
Realized losses	21
Duke Energy Progress [Member]
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Realized gains	24
Realized losses	19
Duke Energy Florida [Member]
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Realized gains	3
Realized losses	$ 2

Fair Value Measurements (Fair V

Fair Value Measurements (Fair Value Measurement Amounts for Assets and Liabilities) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Alternative Investment, Fair Value Disclosure	$ 72	$ 74
Available-for-sale Securities, Debt Securities	2,269
Derivative assets	37	51
Total assets	7,451	7,503
Derivative liabilities	(190)	(230)
Net assets (liabilities)	7,261	7,273
Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	2	3
Total assets	5,616	5,658
Derivative liabilities	(1)	(2)
Net assets (liabilities)	5,615	5,656
Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	27	20
Total assets	1,755	1,743
Derivative liabilities	(57)	(86)
Net assets (liabilities)	1,698	1,657
Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	8	28
Total assets	8	28
Derivative liabilities	(132)	(142)
Net assets (liabilities)	(124)	(114)
Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity Securities, FV-NI	4,857
Available-for-sale Securities, Debt Securities	2,169
Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity Securities, FV-NI	4,785
Available-for-sale Securities, Debt Securities	633
Ndtf [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale Securities, Debt Securities	1,536
Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity Securities, FV-NI	130
Available-for-sale Securities, Debt Securities	258
Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity Securities, FV-NI	130
Available-for-sale Securities, Debt Securities	66
Other Classification [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale Securities, Debt Securities	192
Equity Securities [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Alternative Investment, Fair Value Disclosure	72	74
Investments, Fair Value Disclosure		4,914
Equity Securities [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		4,840
Equity Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		123
Equity Securities [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		123
Debt Securities [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		2,174
Debt Securities [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		635
Debt Securities [Member] | Ndtf [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		1,539
Debt Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		241
Debt Securities [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		57
Debt Securities [Member] | Other Classification [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		184
Duke Energy Carolinas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Alternative Investment, Fair Value Disclosure	72	74
Available-for-sale Securities, Debt Securities	1,018
Derivative assets	2	2
Total assets	3,739	3,760
Derivative liabilities	(11)	(35)
Net assets (liabilities)	3,728	3,725
Duke Energy Carolinas [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0
Total assets	2,806	2,822
Derivative liabilities	(1)	(1)
Net assets (liabilities)	2,805	2,821
Duke Energy Carolinas [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	2	2
Total assets	861	864
Derivative liabilities	(10)	(34)
Net assets (liabilities)	851	830
Duke Energy Carolinas [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity Securities, FV-NI	2,669
Available-for-sale Securities, Debt Securities	1,068
Duke Energy Carolinas [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity Securities, FV-NI	2,597
Available-for-sale Securities, Debt Securities	209
Duke Energy Carolinas [Member] | Ndtf [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale Securities, Debt Securities	859
Duke Energy Carolinas [Member] | Equity Securities [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Alternative Investment, Fair Value Disclosure	72	74
Investments, Fair Value Disclosure		2,692
Duke Energy Carolinas [Member] | Equity Securities [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		2,618
Duke Energy Carolinas [Member] | Debt Securities [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		1,066
Duke Energy Carolinas [Member] | Debt Securities [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		204
Duke Energy Carolinas [Member] | Debt Securities [Member] | Ndtf [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		862
Progress Energy [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale Securities, Debt Securities	1,055
Derivative assets	3	3
Total assets	3,349	3,392
Derivative liabilities	(37)	(36)
Net assets (liabilities)	3,312	3,356
Progress Energy [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	1
Total assets	2,622	2,666
Derivative liabilities	(1)	(1)
Net assets (liabilities)	2,621	2,665
Progress Energy [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	3	2
Total assets	727	726
Derivative liabilities	(36)	(35)
Net assets (liabilities)	691	691
Progress Energy [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity Securities, FV-NI	2,188
Available-for-sale Securities, Debt Securities	1,101
Progress Energy [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity Securities, FV-NI	2,188
Available-for-sale Securities, Debt Securities	424
Progress Energy [Member] | Ndtf [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale Securities, Debt Securities	677
Progress Energy [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale Securities, Debt Securities	57
Progress Energy [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale Securities, Debt Securities	10
Progress Energy [Member] | Other Classification [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale Securities, Debt Securities	47
Progress Energy [Member] | Equity Securities [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		2,222
Progress Energy [Member] | Equity Securities [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		2,222
Progress Energy [Member] | Debt Securities [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		1,108
Progress Energy [Member] | Debt Securities [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		431
Progress Energy [Member] | Debt Securities [Member] | Ndtf [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		677
Progress Energy [Member] | Debt Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		59
Progress Energy [Member] | Debt Securities [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		12
Progress Energy [Member] | Debt Securities [Member] | Other Classification [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		47
Duke Energy Progress [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale Securities, Debt Securities	747
Derivative assets	2	2
Total assets	2,574	2,594
Derivative liabilities	(21)	(18)
Net assets (liabilities)	2,553	2,576
Duke Energy Progress [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	1
Total assets	2,020	2,040
Derivative liabilities	(1)	(1)
Net assets (liabilities)	2,019	2,039
Duke Energy Progress [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	2	1
Total assets	554	554
Derivative liabilities	(20)	(17)
Net assets (liabilities)	534	537
Duke Energy Progress [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity Securities, FV-NI	1,765
Available-for-sale Securities, Debt Securities	806
Duke Energy Progress [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity Securities, FV-NI	1,765
Available-for-sale Securities, Debt Securities	254
Duke Energy Progress [Member] | Ndtf [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale Securities, Debt Securities	552
Duke Energy Progress [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale Securities, Debt Securities	1
Duke Energy Progress [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale Securities, Debt Securities	1
Duke Energy Progress [Member] | Equity Securities [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		1,795
Duke Energy Progress [Member] | Equity Securities [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		1,795
Duke Energy Progress [Member] | Debt Securities [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		796
Duke Energy Progress [Member] | Debt Securities [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		243
Duke Energy Progress [Member] | Debt Securities [Member] | Ndtf [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		553
Duke Energy Progress [Member] | Debt Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		1
Duke Energy Progress [Member] | Debt Securities [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		1
Duke Energy Florida [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale Securities, Debt Securities	308
Derivative assets	1	1
Total assets	766	788
Derivative liabilities	(7)	(12)
Net assets (liabilities)	759	776
Duke Energy Florida [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	593	616
Net assets (liabilities)	593	616
Duke Energy Florida [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	1	1
Total assets	173	172
Derivative liabilities	(7)	(12)
Net assets (liabilities)	166	160
Duke Energy Florida [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity Securities, FV-NI	423
Available-for-sale Securities, Debt Securities	295
Duke Energy Florida [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity Securities, FV-NI	423
Available-for-sale Securities, Debt Securities	170
Duke Energy Florida [Member] | Ndtf [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale Securities, Debt Securities	125
Duke Energy Florida [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale Securities, Debt Securities	47
Duke Energy Florida [Member] | Other Classification [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale Securities, Debt Securities	47
Duke Energy Florida [Member] | Equity Securities [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		427
Duke Energy Florida [Member] | Equity Securities [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		427
Duke Energy Florida [Member] | Debt Securities [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		312
Duke Energy Florida [Member] | Debt Securities [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		188
Duke Energy Florida [Member] | Debt Securities [Member] | Ndtf [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		124
Duke Energy Florida [Member] | Debt Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		48
Duke Energy Florida [Member] | Debt Securities [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		1
Duke Energy Florida [Member] | Debt Securities [Member] | Other Classification [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		47
Duke Energy Ohio [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	1	1
Derivative liabilities	(4)	(5)
Net assets (liabilities)	(3)	(4)
Duke Energy Ohio [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilities	(4)	(5)
Net assets (liabilities)	(4)	(5)
Duke Energy Ohio [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	1	1
Net assets (liabilities)	1	1
Duke Energy Indiana [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity Securities, FV-NI	96
Available-for-sale Securities, Debt Securities	31
Derivative assets	7	27
Total assets	134	155
Net assets (liabilities)	134	155
Duke Energy Indiana [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0
Total assets	96	97
Derivative liabilities	0
Net assets (liabilities)	96	97
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	7	27
Total assets	7	27
Net assets (liabilities)	7	27
Duke Energy Indiana [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity Securities, FV-NI	96
Available-for-sale Securities, Debt Securities	31
Duke Energy Indiana [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity Securities, FV-NI	96
Duke Energy Indiana [Member] | Other Classification [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale Securities, Debt Securities	31
Duke Energy Indiana [Member] | Equity Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		97
Duke Energy Indiana [Member] | Equity Securities [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		97
Duke Energy Indiana [Member] | Debt Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		31
Duke Energy Indiana [Member] | Debt Securities [Member] | Other Classification [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		31
Piedmont Natural Gas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	1	2
Total assets		3
Derivative liabilities	(132)	(142)
Net assets (liabilities)	(131)	(139)
Piedmont Natural Gas [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	1	2
Total assets		3
Net assets (liabilities)	1	3
Piedmont Natural Gas [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilities	(132)	(142)
Net assets (liabilities)	$ (132)	(142)
Piedmont Natural Gas [Member] | Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		1
Piedmont Natural Gas [Member] | Debt Securities [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure		$ 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
	Mar. 31, 2018	Mar. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurement Transfers Between Activity Levels	$ 0	$ 0
Derivatives (net)
Beginning balance	(114,000,000)	(166,000,000)
Settlements	(14,000,000)	(9,000,000)
Total gains (losses) included on the Condensed Consolidated Balance Sheet	4,000,000	40,000,000
Ending balance	(124,000,000)	(135,000,000)
Investments and Derivatives, Net
Beginning balance	(114,000,000)	(161,000,000)
Settlements	(14,000,000)	(9,000,000)
Total gains (losses) included on the Condensed Consolidated Balance Sheet	4,000,000	40,000,000
Ending balance	(124,000,000)	(130,000,000)
Investments [Member]
Investments
Beginning balance		5,000,000
Ending balance		5,000,000
Duke Energy Ohio [Member]
Derivatives (net)
Beginning balance	1,000,000	5,000,000
Settlements	0	(1,000,000)
Total gains (losses) included on the Condensed Consolidated Balance Sheet	0	(3,000,000)
Ending balance	1,000,000	1,000,000
Duke Energy Indiana [Member]
Derivatives (net)
Beginning balance	27,000,000	16,000,000
Settlements	(14,000,000)	(7,000,000)
Total gains (losses) included on the Condensed Consolidated Balance Sheet	(6,000,000)	0
Ending balance	7,000,000	9,000,000
Piedmont Natural Gas [Member]
Derivatives (net)
Beginning balance	(142,000,000)	(187,000,000)
Total gains (losses) and settlements	10,000,000	42,000,000
Ending balance	$ (132,000,000)	$ (145,000,000)

Fair Value Measurements (Quanti

Fair Value Measurements (Quantitative Level 3 Fair Value Disclosure - Assets) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)$ / MWh	Mar. 31, 2017USD ($)$ / MWh	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Net derivative asset (liability)	$ (124)	$ (135)	$ (114)	$ (166)
Duke Energy Ohio [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Net derivative asset (liability)	1	$ 1	1	5
Duke Energy Ohio [Member] | Financial Transmission Rights [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Net derivative asset (liability)	$ 1		1
Duke Energy Ohio [Member] | Financial Transmission Rights [Member] | Minimum [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Input Price Per Unit | $ / MWh		0.07
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	2.88	1.41
Duke Energy Indiana [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Net derivative asset (liability)	$ 7	$ 9	27	$ 16
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)	$ 7		$ 27
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	(5.09)	(0.77)
Duke Energy Indiana [Member] | Financial Transmission Rights [Member] | Maximum [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Input Price Per Unit | $ / MWh	7.58	7.44

Fair Value Measurements (Quan75

Fair Value Measurements (Quantitative Level 3 Fair Value Disclosure - Liabilities) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)$ / MMBTU	Mar. 31, 2017USD ($)$ / MMBTU	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Net derivative asset (liability)	$ (124)	$ (135)	$ (114)	$ (166)
Piedmont Natural Gas [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Net derivative asset (liability)	(132)	$ (145)	(142)	$ (187)
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)	$ (132)		$ (142)
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	2.15	2.10
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	3.65	2.88

Fair Value Measurements (Additi

Fair Value Measurements (Additional Fair Value Disclosure) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	$ 52,981	$ 52,279
Long-term debt, fair value	54,383	55,331
Duke Energy Carolinas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	10,694	10,103
Long-term debt, fair value	11,556	11,372
Progress Energy [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	17,757	17,837
Long-term debt, fair value	19,270	20,000
Duke Energy Progress [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	7,357	7,357
Long-term debt, fair value	7,687	7,992
Duke Energy Florida [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	7,015	7,095
Long-term debt, fair value	7,632	7,953
Duke Energy Ohio [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	2,067	2,067
Long-term debt, fair value	2,217	2,249
Duke Energy Indiana [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	3,782	3,783
Long-term debt, fair value	4,322	4,464
Piedmont Natural Gas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	2,037	2,037
Long-term debt, fair value	$ 2,209	$ 2,209

Variable Interest Entities (Nar

Variable Interest Entities (Narrative) (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2016
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Variable Interest Entity, Financial or Other Support, Amount	$ 0	$ 0
Cinergy Receivables [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Percent of proceeds received as cash	75.00%
Percent of proceeds received as subordinated note	25.00%
Minimum equity balance required by Cinergy Receivables	$ 3,000,000
Pioneer Transmission [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Variable Interest Entity Ownership Interest	50.00%
OVEC [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Variable Interest Entity Ownership Interest	9.00%
Duke Energy Ohio [Member] | Cinergy Receivables [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Fixed interest rate added to LIBOR to compute variable rate	1.00%
Duke Energy Indiana [Member] | Cinergy Receivables [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Fixed interest rate added to LIBOR to compute variable rate	1.00%

Variable Interest Entities (Sch

Variable Interest Entities (Schedule of Accounts Receivable Securitizations) (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Apr. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Variable Interest Entities [Line Items]
Long-Term Debt		$ 49,030	$ 49,035
Duke Energy Carolinas [Member]
Variable Interest Entities [Line Items]
Long-Term Debt		9,589	8,598
Duke Energy Progress [Member]
Variable Interest Entities [Line Items]
Long-Term Debt		6,604	7,204
Duke Energy Florida [Member]
Variable Interest Entities [Line Items]
Long-Term Debt		$ 6,247	6,327
Cinergy Receivables [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Line of Credit Facility, Expiration Date		Dec. 1, 2020
Facility size		$ 325
Long-Term Debt		325	325
Accounts Receivable from Securitization		$ 504	545
DERF [Member] | Duke Energy Carolinas [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Line of Credit Facility, Expiration Date		Dec. 1, 2020
Facility size		$ 450
Long-Term Debt		450	450
Accounts Receivable from Securitization		$ 634	640
DEPR [Member] | Duke Energy Progress [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Line of Credit Facility, Expiration Date		Feb. 1, 2021
Facility size		$ 300
Long-Term Debt		300	300
Accounts Receivable from Securitization		$ 497	459
DEFR [Member] | Duke Energy Florida [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Line of Credit Facility, Expiration Date		Apr. 1, 2019
Facility size		$ 225
Long-Term Debt		225	225
Accounts Receivable from Securitization		$ 313	$ 317
Subsequent Event [Member] | DEFR [Member] | Duke Energy Florida [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Line of Credit Facility, Expiration Date	Apr. 1, 2021

Variable Interest Entities (S79

Variable Interest Entities (Schedule of Consolidated VIEs) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Regulatory assets, current	$ 1,544	$ 1,437
Other, current assets	422	634
Regulatory assets, noncurrent	12,218	12,442
Property, plant and equipment, cost	129,281	127,507
Other noncurrent assets	3,062	2,960
Accumulated depreciation and amortization	(42,307)	(41,537)
Current Liabilities: Other	1,542	1,865
Current maturities of long-term debt	3,951	3,244
Long-Term Debt	49,030	49,035
Deferred income taxes	6,855	6,621
Noncurrent Liabilities: Other	1,538	1,581
Duke Energy Carolinas [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Regulatory assets, current	331	299
Other, current assets	42	19
Regulatory assets, noncurrent	2,825	2,853
Property, plant and equipment, cost	43,562	42,939
Other noncurrent assets	1,023	979
Accumulated depreciation and amortization	(15,404)	(15,063)
Current Liabilities: Other	369	486
Current maturities of long-term debt	805	1,205
Long-Term Debt	9,589	8,598
Deferred income taxes	3,493	3,413
Noncurrent Liabilities: Other	532	566
Duke Energy Progress [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Regulatory assets, current	476	352
Other, current assets	55	97
Regulatory assets, noncurrent	3,480	3,507
Property, plant and equipment, cost	29,866	29,583
Other noncurrent assets	641	599
Accumulated depreciation and amortization	(11,012)	(10,903)
Current Liabilities: Other	324	376
Current maturities of long-term debt	603	3
Long-Term Debt	6,604	7,204
Deferred income taxes	1,932	1,883
Noncurrent Liabilities: Other	46	45
Duke Energy Florida [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Regulatory assets, current	393	389
Other, current assets	40	86
Regulatory assets, noncurrent	2,391	2,503
Property, plant and equipment, cost	18,040	17,730
Other noncurrent assets	301	284
Accumulated depreciation and amortization	(5,042)	(4,947)
Current Liabilities: Other	299	334
Current maturities of long-term debt	768	768
Long-Term Debt	6,247	6,327
Deferred income taxes	1,812	1,761
Noncurrent Liabilities: Other	110	108
DEFPF [Member] | Duke Energy Florida [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Receivables of VIEs	4	4
Regulatory assets, current	51	51
Other, current assets	13	40
Regulatory assets, noncurrent	1,082	1,091
Current Liabilities: Other	3	10
Current maturities of long-term debt	53	53
Long-Term Debt	1,136	1,164
DERF [Member] | Duke Energy Carolinas [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Receivables of VIEs	634	640
Long-Term Debt	450	450
DEPR [Member] | Duke Energy Progress [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Receivables of VIEs	497	459
Long-Term Debt	300	300
DEFR [Member] | Duke Energy Florida [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Receivables of VIEs	313	317
Long-Term Debt	225	225
Cinergy Receivables [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Receivables of VIEs	504	545
Long-Term Debt	325	325
Commercial Renewables [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Other, current assets	217	174
Property, plant and equipment, cost	4,017	3,923
Other noncurrent assets	227	50
Accumulated depreciation and amortization	(626)	(591)
Current maturities of long-term debt	171	170
Long-Term Debt	1,700	1,700
Deferred income taxes		(148)
Noncurrent Liabilities: Other	$ 236	$ 241

Variable Interest Entities (S80

Variable Interest Entities (Schedule of Non-Consolidated VIEs) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Variable Interest Entities [Line Items]
Investments in equity method unconsolidated affiliates	$ 1,189	$ 1,175
Other noncurrent assets	3,062	2,960
Taxes accrued	422	551
Current Liabilities: Other	1,542	1,865
Deferred income taxes	6,855	6,621
Noncurrent Liabilities: Other	1,538	1,581
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Investments in equity method unconsolidated affiliates	951	919
Other noncurrent assets	17	17
Total assets	968	936
Taxes accrued	(29)	(29)
Current Liabilities: Other	3	4
Deferred income taxes	32	42
Noncurrent Liabilities: Other	20	12
Total liabilities	26	29
Net assets	942	907
Pipeline Investments [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Investments in equity method unconsolidated affiliates	723	697
Other noncurrent assets	17	17
Total assets	740	714
Taxes accrued	(29)	(29)
Deferred income taxes	32	42
Noncurrent Liabilities: Other	8
Total liabilities	11	13
Net assets	729	701
Commercial Renewables [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Investments in equity method unconsolidated affiliates	183	180
Total assets	183	180
Net assets	183	180
Other VIEs [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Investments in equity method unconsolidated affiliates	45	42
Total assets	45	42
Current Liabilities: Other	3	4
Noncurrent Liabilities: Other	12	12
Total liabilities	15	16
Net assets	30	26
Duke Energy Ohio [Member]
Variable Interest Entities [Line Items]
Receivables from affiliated companies	77	133
Other noncurrent assets	48	21
Taxes accrued	145	190
Current Liabilities: Other	66	71
Deferred income taxes	766	781
Noncurrent Liabilities: Other	105	108
Duke Energy Ohio [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Receivables from affiliated companies	65	87
Total assets	65	87
Net assets	65	87
Duke Energy Indiana [Member]
Variable Interest Entities [Line Items]
Receivables from affiliated companies	99	125
Other noncurrent assets	234	189
Taxes accrued	94	95
Current Liabilities: Other	83	104
Deferred income taxes	941	925
Noncurrent Liabilities: Other	28	18
Duke Energy Indiana [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Receivables from affiliated companies	86	106
Total assets	86	106
Net assets	$ 86	$ 106

Variable Interest Entities (Pip

Variable Interest Entities (Pipeline Investments) (Details) - USD ($) $ in Millions	Apr. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Variable Interest Entities [Line Items]
Investments in Joint Ventures		$ 1,189	$ 1,175
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Liabilities		26	29
Investments in Joint Ventures		$ 951	919
Variable Interest Entity, Not Primary Beneficiary [Member] | Atlantic Coast Pipeline [Member]
Variable Interest Entities [Line Items]
Variable Interest Entity Ownership Interest		47.00%
Equity Method Investment Line Of Credit Facility Maximum Borrowing Capacity			3,400
Investments in Joint Ventures		$ 474	397
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		$ 346
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		$ 223	219
Variable Interest Entity, Not Primary Beneficiary [Member] | Constitution Pipeline [Member]
Variable Interest Entities [Line Items]
Equity Method Investment, Other than Temporary Impairment		$ 55
Variable Interest Entity Ownership Interest		24.00%
Investments in Joint Ventures		$ 26	81
Variable Interest Entity, Not Primary Beneficiary [Member] | Pipeline Investments [Member]
Variable Interest Entities [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Liabilities		11	13
Investments in Joint Ventures		723	697
Piedmont Natural Gas [Member]
Variable Interest Entities [Line Items]
Investments in Joint Ventures		$ 62	$ 61
Subsequent Event [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Sabal Trail Transmission Pipeline [Member]
Variable Interest Entities [Line Items]
Equity Method Investment Long Term Debt	$ 1,500
Proceeds from Equity Method Investment, Distribution, Return of Capital	$ 112

Variable Interest Entities (Fai

Variable Interest Entities (Fair Value Assumptions)(Details) - Variable Interest Entity, Not Primary Beneficiary [Member] - Cinergy Receivables [Member]	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Duke Energy Ohio [Member]
Variable Interest Entities [Line Items]
Anticipated credit loss ratio	0.50%	0.50%
Discount rate	2.60%	2.10%
Receivable turnover rate	13.60%	13.50%
Duke Energy Indiana [Member]
Variable Interest Entities [Line Items]
Anticipated credit loss ratio	0.30%	0.30%
Discount rate	2.60%	2.10%
Receivable turnover rate	10.80%	10.70%

Variable Interest Entities (Rec

Variable Interest Entities (Receivables Sold)(Details) - Variable Interest Entity, Not Primary Beneficiary [Member] - Cinergy Receivables [Member] - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Duke Energy Ohio [Member]
Variable Interest Entities [Line Items]
Receivables sold	$ 249	$ 273
Less: Retained interests	65	87
Net receivables sold	184	186
Duke Energy Indiana [Member]
Variable Interest Entities [Line Items]
Receivables sold	297	312
Less: Retained interests	86	106
Net receivables sold	$ 211	$ 206

Variable Interest Entities (Sal

Variable Interest Entities (Sales and Cash Flows)(Details) - Variable Interest Entity, Not Primary Beneficiary [Member] - Cinergy Receivables [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Duke Energy Ohio [Member]
Variable Interest Entities [Line Items]
Receivables sold	$ 567	$ 533
Loss recognized on sale	3	2
Cash proceeds from receivables sold	585	559
Return received on retained interests	2	1
Duke Energy Indiana [Member]
Variable Interest Entities [Line Items]
Receivables sold	694	664
Loss recognized on sale	3	3
Cash proceeds from receivables sold	711	693
Return received on retained interests	$ 2	$ 2

Revenue (Details)

Revenue (Details)	3 Months Ended
	Mar. 31, 2018USD ($)
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 5,928,000,000
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 0

Revenue Remaining Performance O

Revenue Remaining Performance Obligations (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)
Progress Energy [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	$ 69
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	9 months
Progress Energy [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	$ 112
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Progress Energy [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	$ 121
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Progress Energy [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	$ 80
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Progress Energy [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	$ 82
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Progress Energy [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	$ 81
Progress Energy [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	545
Duke Energy Progress [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	$ 7
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	9 months
Duke Energy Progress [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	$ 9
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Duke Energy Progress [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	$ 9
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Duke Energy Progress [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	$ 9
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Duke Energy Progress [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	$ 9
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Duke Energy Progress [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	$ 18
Duke Energy Progress [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	61
Duke Energy Florida [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	$ 62
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	9 months
Duke Energy Florida [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	$ 103
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Duke Energy Florida [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	$ 112
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Duke Energy Florida [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	$ 71
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Duke Energy Florida [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	$ 73
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Duke Energy Florida [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	$ 63
Duke Energy Florida [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	484
Duke Energy Indiana [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	$ 6
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	9 months
Duke Energy Indiana [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	$ 9
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Duke Energy Indiana [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	$ 10
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Duke Energy Indiana [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	$ 5
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Duke Energy Indiana [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	$ 0
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Duke Energy Indiana [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	$ 0
Duke Energy Indiana [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	30
Piedmont Natural Gas [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	$ 55
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	9 months
Piedmont Natural Gas [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	$ 72
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Piedmont Natural Gas [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	$ 70
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Piedmont Natural Gas [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	$ 65
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Piedmont Natural Gas [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	$ 64
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Piedmont Natural Gas [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	$ 482
Piedmont Natural Gas [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	$ 808

Revenue Disaggregation of Reven

Revenue Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 5,928
Revenue from Sources other than Contracts with Customers	207
Operating revenues	6,135	$ 5,729
Electric Utilities and Infrastructure [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	5,161
Operating revenues	5,315	4,939
Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	2,350
Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | General [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,375
Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	664
Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	633
Electric Utilities and Infrastructure [Member] | Other Revenues [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	139
Gas Utilities and Infrastructure [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	717
Operating revenues	702	648
Gas Utilities and Infrastructure [Member] | Other Revenues [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	55
Gas Utilities and Infrastructure [Member] | Natural Gas, US Regulated [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	413
Gas Utilities and Infrastructure [Member] | Natural Gas, US Regulated [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	48
Gas Utilities and Infrastructure [Member] | Natural Gas, US Regulated [Member] | Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	201
Commercial Renewables [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	33
Operating revenues	101	128
Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	17
Duke Energy Carolinas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,694
Revenue from Sources other than Contracts with Customers	69
Operating revenues	1,763	1,716
Duke Energy Carolinas [Member] | Electric Utilities and Infrastructure [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,694
Duke Energy Carolinas [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	781
Duke Energy Carolinas [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | General [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	472
Duke Energy Carolinas [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	255
Duke Energy Carolinas [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	119
Duke Energy Carolinas [Member] | Electric Utilities and Infrastructure [Member] | Other Revenues [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	67
Progress Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	2,526
Revenue from Sources other than Contracts with Customers	50
Operating revenues	2,576	2,179
Progress Energy [Member] | Electric Utilities and Infrastructure [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	2,526
Progress Energy [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,112
Progress Energy [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | General [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	631
Progress Energy [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	208
Progress Energy [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	446
Progress Energy [Member] | Electric Utilities and Infrastructure [Member] | Other Revenues [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	129
Duke Energy Progress [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,442
Revenue from Sources other than Contracts with Customers	18
Operating revenues	1,460	1,219
Duke Energy Progress [Member] | Electric Utilities and Infrastructure [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,442
Duke Energy Progress [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	516
Duke Energy Progress [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | General [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	299
Duke Energy Progress [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	145
Duke Energy Progress [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	397
Duke Energy Progress [Member] | Electric Utilities and Infrastructure [Member] | Other Revenues [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	85
Duke Energy Florida [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,083
Revenue from Sources other than Contracts with Customers	32
Operating revenues	1,115	959
Duke Energy Florida [Member] | Electric Utilities and Infrastructure [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,083
Duke Energy Florida [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	595
Duke Energy Florida [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | General [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	333
Duke Energy Florida [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	62
Duke Energy Florida [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	50
Duke Energy Florida [Member] | Electric Utilities and Infrastructure [Member] | Other Revenues [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	43
Duke Energy Ohio [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	507
Revenue from Sources other than Contracts with Customers	17
Operating revenues	524	518
Duke Energy Ohio [Member] | Electric Utilities and Infrastructure [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	320
Duke Energy Ohio [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	180
Duke Energy Ohio [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | General [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	96
Duke Energy Ohio [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	30
Duke Energy Ohio [Member] | Electric Utilities and Infrastructure [Member] | Other Revenues [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	14
Duke Energy Ohio [Member] | Gas Utilities and Infrastructure [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	173
Duke Energy Ohio [Member] | Gas Utilities and Infrastructure [Member] | Other Revenues [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	6
Duke Energy Ohio [Member] | Gas Utilities and Infrastructure [Member] | Natural Gas, US Regulated [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	111
Duke Energy Ohio [Member] | Gas Utilities and Infrastructure [Member] | Natural Gas, US Regulated [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	7
Duke Energy Ohio [Member] | Gas Utilities and Infrastructure [Member] | Natural Gas, US Regulated [Member] | Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	49
Duke Energy Ohio [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	14
Duke Energy Indiana [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	714
Revenue from Sources other than Contracts with Customers	17
Operating revenues	731	758
Duke Energy Indiana [Member] | Electric Utilities and Infrastructure [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	714
Duke Energy Indiana [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	278
Duke Energy Indiana [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | General [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	178
Duke Energy Indiana [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	173
Duke Energy Indiana [Member] | Electric Utilities and Infrastructure [Member] | Electricity, US Regulated [Member] | Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	68
Duke Energy Indiana [Member] | Electric Utilities and Infrastructure [Member] | Other Revenues [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	17
Piedmont Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	557
Revenue from Sources other than Contracts with Customers	(4)
Operating revenues	553	$ 500
Piedmont Natural Gas [Member] | Gas Utilities and Infrastructure [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	557
Piedmont Natural Gas [Member] | Gas Utilities and Infrastructure [Member] | Other Revenues [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	49
Piedmont Natural Gas [Member] | Gas Utilities and Infrastructure [Member] | Natural Gas, US Regulated [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	302
Piedmont Natural Gas [Member] | Gas Utilities and Infrastructure [Member] | Natural Gas, US Regulated [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	41
Piedmont Natural Gas [Member] | Gas Utilities and Infrastructure [Member] | Natural Gas, US Regulated [Member] | Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	152
Piedmont Natural Gas [Member] | Gas Utilities and Infrastructure [Member] | Natural Gas, US Regulated [Member] | Power Generation [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 13

Revenue Unbilled Revenues (Deta

Revenue Unbilled Revenues (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	$ 823	$ 944
Duke Energy Carolinas [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	310	342
Progress Energy [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	237	228
Duke Energy Progress [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	167	143
Duke Energy Florida [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	70	85
Duke Energy Ohio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	2	4
Duke Energy Indiana [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	24	21
Piedmont Natural Gas [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	45	86
Cinergy Receivables [Member] | Duke Energy Ohio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	67	104
Cinergy Receivables [Member] | Duke Energy Indiana [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables	$ 108	$ 132

Common Stock (Earnings Per Shar

Common Stock (Earnings Per Share Data)(Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share [Abstract]
Income from continuing operations attributable to Duke Energy common stockholders excluding impact of participating securities	$ 619	$ 715
Average shares, basic	701	700
Average shares, diluted	701	700
EPS, basic (usd per share)	$ 0.88	$ 1.02
EPS, diluted (usd per share)	$ 0.88	$ 1.02
Number of stock options and performance and unvested stock awards excluded from the dilutive securities calculation	2	2
Dividends declared per share (usd per share)	$ 0.89	$ 0.855

Common Stock (Equity Securities

Common Stock (Equity Securities Offering) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Billions	Feb. 20, 2018	Mar. 31, 2018
Forward Contract Indexed to Issuer's Equity [Line Items]
Maximum Value Of Shares To Be Issued Under ATM Program	$ 1
Shares offered		21.3
Settlement Alternatives, Shares		21.3
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share		$ 74.07
Forward Contract Indexed to Issuer's Equity, Shares		0.9

Stock-Based Compensation (Sched

Stock-Based Compensation (Schedule of Stock-Based Compensation Expense) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pretax stock-based compensation cost	$ 17	$ 15
Tax benefit associated with stock-based compensation expense	4	5
Stock-based compensation costs capitalized	1	1
Restricted Stock Units Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pretax stock-based compensation cost	10	8
Performance Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pretax stock-based compensation cost	$ 7	$ 7

Employee Benefit Plans (Plan Co

Employee Benefit Plans (Plan Contributions) (Details) - Qualified Pension Plan [Member] - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Employer Contributions, Current Fiscal Year	$ 148,000,000
Contributions by Employer	141,000,000	$ 0
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year	7,000,000
Duke Energy Carolinas [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Employer Contributions, Current Fiscal Year	46,000,000
Contributions by Employer	46,000,000
Progress Energy [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Employer Contributions, Current Fiscal Year	45,000,000
Contributions by Employer	45,000,000
Duke Energy Progress [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Employer Contributions, Current Fiscal Year	25,000,000
Contributions by Employer	25,000,000
Duke Energy Florida [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Employer Contributions, Current Fiscal Year	20,000,000
Contributions by Employer	20,000,000
Duke Energy Indiana [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Employer Contributions, Current Fiscal Year	8,000,000
Contributions by Employer	8,000,000
Piedmont Natural Gas [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Employer Contributions, Current Fiscal Year	7,000,000
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year	$ 7,000,000

Employee Benefit Plans (Compone

Employee Benefit Plans (Components of Net Periodic Pension Costs) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Qualified Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 45	$ 40
Interest cost on projected benefit obligation	75	82
Expected return on plan assets	(140)	(136)
Amortization of actuarial loss (gain)	33	36
Amortization of prior service credit	(8)	(6)
Other		2
Net periodic costs	5	18
Qualified Pension Plan [Member] | Duke Energy Carolinas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	15	12
Interest cost on projected benefit obligation	18	20
Expected return on plan assets	(37)	(35)
Amortization of actuarial loss (gain)	7	8
Amortization of prior service credit	(2)	(2)
Net periodic costs	1	3
Qualified Pension Plan [Member] | Progress Energy [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	13	12
Interest cost on projected benefit obligation	24	25
Expected return on plan assets	(45)	(43)
Amortization of actuarial loss (gain)	11	14
Amortization of prior service credit	(1)	(1)
Other		1
Net periodic costs	2	8
Qualified Pension Plan [Member] | Duke Energy Progress [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	7	6
Interest cost on projected benefit obligation	11	12
Expected return on plan assets	(21)	(21)
Amortization of actuarial loss (gain)	5	6
Net periodic costs	2	3
Qualified Pension Plan [Member] | Duke Energy Florida [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	5	5
Interest cost on projected benefit obligation	13	13
Expected return on plan assets	(23)	(21)
Amortization of actuarial loss (gain)	6	7
Net periodic costs	1	4
Qualified Pension Plan [Member] | Duke Energy Ohio [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	1	1
Interest cost on projected benefit obligation	5	5
Expected return on plan assets	(7)	(7)
Amortization of actuarial loss (gain)	1	1
Qualified Pension Plan [Member] | Duke Energy Indiana [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	2	2
Interest cost on projected benefit obligation	6	7
Expected return on plan assets	(10)	(11)
Amortization of actuarial loss (gain)	2	3
Net periodic costs		1
Qualified Pension Plan [Member] | Piedmont Natural Gas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	2	3
Interest cost on projected benefit obligation	3	3
Expected return on plan assets	(6)	(6)
Amortization of actuarial loss (gain)	3	3
Amortization of prior service credit	(3)	(1)
Net periodic costs	(1)	2
Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	1	1
Interest cost on projected benefit obligation	7	9
Expected return on plan assets	(2)	(3)
Amortization of actuarial loss (gain)	1	2
Amortization of prior service credit	(5)	(29)
Net periodic costs	2	(20)
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
Expected return on plan assets	(2)	(2)
Amortization of actuarial loss (gain)		(1)
Amortization of prior service credit	(1)	(2)
Net periodic costs	(1)	(3)
Other Post-Retirement Benefit Plans [Member] | Progress Energy [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost on projected benefit obligation	4	4
Amortization of actuarial loss (gain)		5
Amortization of prior service credit	(2)	(21)
Net periodic costs	2	(12)
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	1	2
Amortization of actuarial loss (gain)		3
Amortization of prior service credit		(14)
Net periodic costs	1	(9)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Florida [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost on projected benefit obligation	1	2
Amortization of actuarial loss (gain)		2
Amortization of prior service credit	(1)	(8)
Net periodic costs		$ (4)
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
Amortization of actuarial loss (gain)	1
Net periodic costs	$ 2

Employee Benefit Plans (Employe

Employee Benefit Plans (Employee Savings Plans) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Defined Contribution Plan Disclosure [Line Items]
Employer contributions	$ 70	$ 65
Duke Energy Carolinas [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions	23	22
Progress Energy [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions	19	18
Duke Energy Progress [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions	13	13
Duke Energy Florida [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions	6	5
Duke Energy Ohio [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions	1	1
Duke Energy Indiana [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions	3	3
Piedmont Natural Gas [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions	$ 4	$ 2

Income Taxes (Effective Tax Rat

Income Taxes (Effective Tax Rates) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Tax Disclosure [Line Items]
Tax Cuts and Jobs Act of 2017 Incomplete Accounting Provisional Income Tax Expense Benefit	$ 76
Reconciliation of Income Tax Expense at the U.S. Federal Statutory Tax Rate to the Actual Tax Expense from Continuing Operations [Abstract]
Effective tax rate	22.50%	32.40%
Duke Energy Carolinas [Member]
Reconciliation of Income Tax Expense at the U.S. Federal Statutory Tax Rate to the Actual Tax Expense from Continuing Operations [Abstract]
Effective tax rate	22.00%	35.40%
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	13.20%	34.10%
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	14.10%	34.10%
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	16.30%	36.60%
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	32.40%	35.40%
Duke Energy Indiana [Member]
Reconciliation of Income Tax Expense at the U.S. Federal Statutory Tax Rate to the Actual Tax Expense from Continuing Operations [Abstract]
Effective tax rate	25.90%	39.30%
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	24.10%	37.90%