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