Variable Interest Entities (Schedule of Consolidated VIEs) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Regulatory assets, current	$ 1,741	$ 1,437
Other, current assets	437	634
Regulatory assets, noncurrent	12,505	12,442
Property, plant and equipment, cost	130,616	127,507
Accumulated depreciation and amortization	(42,499)	(41,537)
Other noncurrent assets	3,087	2,960
Current Liabilities: Other	1,699	1,865
Current maturities of long-term debt	2,852	3,244
Long-Term Debt	49,863	49,035
Deferred income taxes	6,977	6,621
Noncurrent Liabilities: Other	1,457	1,581
Duke Energy Carolinas [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Regulatory assets, current	420	299
Other, current assets	21	19
Regulatory assets, noncurrent	3,234	2,853
Property, plant and equipment, cost	43,429	42,939
Accumulated depreciation and amortization	(15,248)	(15,063)
Other noncurrent assets	1,036	979
Current Liabilities: Other	412	486
Current maturities of long-term debt	505	1,205
Long-Term Debt	9,589	8,598
Deferred income taxes	3,507	3,413
Noncurrent Liabilities: Other	515	566
Duke Energy Progress [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Regulatory assets, current	532	352
Other, current assets	33	97
Regulatory assets, noncurrent	3,573	3,507
Property, plant and equipment, cost	30,535	29,583
Accumulated depreciation and amortization	(11,296)	(10,903)
Other noncurrent assets	635	599
Current Liabilities: Other	344	376
Current maturities of long-term debt	603	3
Long-Term Debt	6,605	7,204
Deferred income taxes	1,957	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	439	389
Other, current assets	183	86
Regulatory assets, noncurrent	2,163	2,503
Property, plant and equipment, cost	18,353	17,730
Accumulated depreciation and amortization	(5,079)	(4,947)
Other noncurrent assets	307	284
Current Liabilities: Other	357	334
Current maturities of long-term debt	269	768
Long-Term Debt	7,183	6,327
Deferred income taxes	2,007	1,761
Noncurrent Liabilities: Other	58	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	51	51
Other, current assets	31	40
Regulatory assets, noncurrent	1,071	1,091
Current Liabilities: Other	10	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	704	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	568	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	394	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	498	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	168	174
Property, plant and equipment, cost	4,017	3,923
Accumulated depreciation and amortization	(661)	(591)
Other noncurrent assets	256	50
Current maturities of long-term debt	175	170
Long-Term Debt	1,605	1,700
Deferred income taxes		(148)
Noncurrent Liabilities: Other	$ 228	$ 241

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