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

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