Variable Interest Entities (Schedule of Non-Consolidated VIEs) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Variable Interest Entities [Line Items]
Investments in equity method unconsolidated affiliates	$ 1,168	$ 1,175
Other noncurrent assets	3,087	2,960
Taxes accrued	494	551
Current Liabilities: Other	1,699	1,865
Deferred income taxes	6,977	6,621
Noncurrent Liabilities: Other	1,457	1,581
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Investments in equity method unconsolidated affiliates	803	919
Other noncurrent assets		17
Total assets	803	936
Taxes accrued	1	(29)
Current Liabilities: Other	4	4
Deferred income taxes	10	42
Noncurrent Liabilities: Other	11	12
Total liabilities	26	29
Net assets	777	907
Pipeline Investments [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Investments in equity method unconsolidated affiliates	566	697
Other noncurrent assets		17
Total assets	566	714
Taxes accrued	1	(29)
Deferred income taxes	10	42
Total liabilities	11	13
Net assets	555	701
Commercial Renewables [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Investments in equity method unconsolidated affiliates	192	180
Total assets	192	180
Net assets	192	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	4	4
Noncurrent Liabilities: Other	11	12
Total liabilities	15	16
Net assets	30	26
Duke Energy Ohio [Member]
Variable Interest Entities [Line Items]
Receivables from affiliated companies	71	133
Other noncurrent assets	63	21
Taxes accrued	127	190
Current Liabilities: Other	71	71
Deferred income taxes	778	781
Noncurrent Liabilities: Other	96	108
Duke Energy Ohio [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Receivables from affiliated companies	58	87
Total assets	58	87
Net assets	58	87
Duke Energy Indiana [Member]
Variable Interest Entities [Line Items]
Receivables from affiliated companies	89	125
Other noncurrent assets	224	189
Taxes accrued	54	95
Current Liabilities: Other	123	104
Deferred income taxes	957	925
Noncurrent Liabilities: Other	14	18
Duke Energy Indiana [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Receivables from affiliated companies	87	106
Total assets	87	106
Net assets	$ 87	$ 106