Variable Interest Entities (Fair Value Assumptions)(Details) - Cinergy Receivables [Member]	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Duke Energy Ohio [Member]
Variable Interest Entities [Line Items]
Anticipated credit loss ratio	0.60%	0.60%
Discount rate	1.20%	1.20%
Receivable turnover rate	12.90%	12.80%
Duke Energy Indiana [Member]
Variable Interest Entities [Line Items]
Anticipated credit loss ratio	0.30%	0.30%
Discount rate	1.20%	1.20%
Receivable turnover rate	10.60%	10.50%