Variable Interest Entities (Schedule of Non-Consolidated VIEs) (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Variable Interest Entities [Line Items]
Investments in equity method unconsolidated affiliates	$ 501	$ 358
Investments and other assets	3,205	3,008
Other current liabilities	2,052	2,188
Deferred credits and other liabilities	32,982	31,364
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Investments in equity method unconsolidated affiliates	348	188
Investments and other assets		4
Total assets	348	192
Other current liabilities	2	3
Deferred credits and other liabilities	14	14
Total liabilities	16	17
Net assets	332	175
Renewables [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Investments in equity method unconsolidated affiliates	223	150
Total assets	223	150
Total liabilities	0
Net assets	223	150
Other VIEs [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Investments in equity method unconsolidated affiliates	125	38
Investments and other assets		4
Total assets	125	42
Other current liabilities	2	3
Deferred credits and other liabilities	14	14
Total liabilities	16	17
Net assets	109	25
Duke Energy Ohio [Member]
Variable Interest Entities [Line Items]
Investments and other assets	17	23
Other current liabilities	151	66
Deferred credits and other liabilities	2,006	2,281
Duke Energy Ohio [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Receivables	43	91
Total assets	43	91
Total liabilities	0
Net assets	43	91
Duke Energy Indiana [Member]
Variable Interest Entities [Line Items]
Other current liabilities	89	98
Deferred credits and other liabilities	3,309	2,730
Duke Energy Indiana [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Receivables	64	113
Total assets	64	113
Total liabilities	0
Net assets	$ 64	$ 113