Variable Interest Entities (Schedule of Non-Consolidated VIEs) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Variable Interest Entities [Line Items]
Investments in equity method unconsolidated affiliates	$ 1,328	$ 1,175
Other noncurrent assets	3,112	2,960
Taxes accrued	674	551
Current Liabilities: Other	1,703	1,865
Deferred income taxes	7,765	6,621
Noncurrent Liabilities: Other	1,477	1,581
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Investments in equity method unconsolidated affiliates	966	919
Other noncurrent assets		17
Total assets	966	936
Taxes accrued		(29)
Current Liabilities: Other	3	4
Deferred income taxes	14	42
Noncurrent Liabilities: Other	11	12
Total liabilities	28	29
Net assets	938	907
Pipeline Investments [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Investments in equity method unconsolidated affiliates	729	697
Other noncurrent assets		17
Total assets	729	714
Taxes accrued		(29)
Deferred income taxes	14	42
Total liabilities	14	13
Net assets	715	701
Commercial Renewables [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Investments in equity method unconsolidated affiliates	190	180
Total assets	190	180
Net assets	190	180
Other VIEs [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Investments in equity method unconsolidated affiliates	47	42
Total assets	47	42
Current Liabilities: Other	3	4
Noncurrent Liabilities: Other	11	12
Total liabilities	14	16
Net assets	33	26
Duke Energy Ohio [Member]
Variable Interest Entities [Line Items]
Receivables from affiliated companies	71	133
Other noncurrent assets	62	21
Taxes accrued	159	190
Current Liabilities: Other	67	71
Deferred income taxes	790	781
Noncurrent Liabilities: Other	113	108
Duke Energy Ohio [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Receivables from affiliated companies	56	87
Total assets	56	87
Net assets	56	87
Duke Energy Indiana [Member]
Variable Interest Entities [Line Items]
Receivables from affiliated companies	98	125
Other noncurrent assets	233	189
Taxes accrued	44	95
Current Liabilities: Other	109	104
Deferred income taxes	988	925
Noncurrent Liabilities: Other	31	18
Duke Energy Indiana [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Receivables from affiliated companies	94	106
Total assets	94	106
Net assets	$ 94	$ 106