Variable Interest Entities (Schedule of Consolidated VIEs) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Regulatory assets, current	$ 1,906	$ 1,437
Other, current assets	1,092	634
Regulatory assets, noncurrent	12,616	12,442
Property, plant and equipment, cost	132,677	127,507
Accumulated depreciation and amortization	(43,200)	(41,537)
Other noncurrent assets	3,112	2,960
Current Liabilities: Other	1,703	1,865
Current maturities of long-term debt	3,455	3,244
Long-Term Debt	50,507	49,035
Deferred income taxes	7,765	6,621
Noncurrent Liabilities: Other	1,477	1,581
Duke Energy Carolinas [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Regulatory assets, current	435	299
Other, current assets	55	19
Regulatory assets, noncurrent	3,188	2,853
Property, plant and equipment, cost	44,086	42,939
Accumulated depreciation and amortization	(15,536)	(15,063)
Other noncurrent assets	1,009	979
Current Liabilities: Other	419	486
Current maturities of long-term debt	506	1,205
Long-Term Debt	9,589	8,598
Deferred income taxes	3,639	3,413
Noncurrent Liabilities: Other	508	566
Duke Energy Progress [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Regulatory assets, current	677	352
Other, current assets	112	97
Regulatory assets, noncurrent	3,822	3,507
Property, plant and equipment, cost	31,091	29,583
Accumulated depreciation and amortization	(11,484)	(10,903)
Other noncurrent assets	653	599
Current Liabilities: Other	353	376
Current maturities of long-term debt	603	3
Long-Term Debt	7,401	7,204
Deferred income taxes	2,076	1,883
Noncurrent Liabilities: Other	48	45
Duke Energy Florida [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Regulatory assets, current	445	389
Other, current assets	27	86
Regulatory assets, noncurrent	2,165	2,503
Property, plant and equipment, cost	18,722	17,730
Accumulated depreciation and amortization	(5,161)	(4,947)
Other noncurrent assets	315	284
Current Liabilities: Other	315	334
Current maturities of long-term debt	269	768
Long-Term Debt	7,102	6,327
Deferred income taxes	2,012	1,761
Noncurrent Liabilities: Other	56	108
DEFPF [Member] \| Duke Energy Florida [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Receivables of VIEs	7	4
Regulatory assets, current	52	51
Other, current assets	14	40
Regulatory assets, noncurrent	1,055	1,091
Current Liabilities: Other	3	10
Current maturities of long-term debt	53	53
Long-Term Debt	1,111	1,164
DERF [Member] \| Duke Energy Carolinas [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Receivables of VIEs	795	640
Long-Term Debt	450	450
DEPR [Member] \| Duke Energy Progress [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Receivables of VIEs	635	459
Long-Term Debt	300	300
DEFR [Member] \| Duke Energy Florida [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Receivables of VIEs	456	317
Long-Term Debt	225	225
Cinergy Receivables [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Receivables of VIEs	504	545
Long-Term Debt	325	325
Commercial Renewables [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Other, current assets	203	174
Property, plant and equipment, cost	4,025	3,923
Accumulated depreciation and amortization	(695)	(591)
Other noncurrent assets	268	50
Current maturities of long-term debt	175	170
Long-Term Debt	1,604	1,700
Deferred income taxes		(148)
Noncurrent Liabilities: Other	$ 225	$ 241

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