Variable Interest Entities (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended		12 Months Ended
	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Variable Interest Entities [Line Items]
Asset impairment charges	$ (16)		$ 80
Cinergy Receivables [Member]
Variable Interest Entities [Line Items]
Minimum equity balance required by Cinergy Receivables		$ 3
Cinergy Receivables [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Percent of proceeds received as cash		75.00%
Percent of proceeds received as subordinated note		25.00%
Duke American Transmission Company [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Variable Interest Entity Ownership Interest		50.00%
Atlantic Coast Pipeline [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Variable Interest Entity Ownership Interest		40.00%
Sabal Trail Transmission Pipeline [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Variable Interest Entity Ownership Interest		7.50%
OVEC [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Variable Interest Entity Ownership Interest		9.00%
Duke Energy Carolinas [Member]
Variable Interest Entities [Line Items]
Asset impairment charges	3		3
Duke Energy Progress [Member]
Variable Interest Entities [Line Items]
Asset impairment charges	$ (18)		(18)
Duke Energy Florida [Member]
Variable Interest Entities [Line Items]
Asset impairment charges			1
Duke Energy Ohio [Member]
Variable Interest Entities [Line Items]
Asset impairment charges			94
Duke Energy Ohio [Member] | Cinergy Receivables [Member]
Variable Interest Entities [Line Items]
Fixed interest rate added to LIBOR to compute variable rate		1.00%
Duke Energy Ohio [Member] | Other VIEs [Member]
Variable Interest Entities [Line Items]
Asset impairment charges			$ 94	$ 94
Duke Energy Indiana [Member] | Cinergy Receivables [Member]
Variable Interest Entities [Line Items]
Fixed interest rate added to LIBOR to compute variable rate		1.00%