Variable Interest Entities (Receivables Sold)(Details) (Variable Interest Entity, Not Primary Beneficiary [Member], Cinergy Receivables [Member], USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Duke Energy Ohio [Member]
Variable Interest Entity [Line Items]
Receivables sold	$ 273	$ 290
Less: retained interests	91	114
Net receivables sold	182	176
Duke Energy Indiana [Member]
Variable Interest Entity [Line Items]
Receivables sold	310	340
Less: retained interests	113	143
Net receivables sold	$ 197	$ 197