Variable Interest Entities (Receivables Sold)(Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Duke Energy Ohio [Member]
Variable Interest Entity [Line Items]
CRC Gross Receivables Sold	$ 304	$ 282
CRC Retained Interests	115	97
CRC Net Receivables Sold	189	185
Duke Energy Indiana [Member]
Variable Interest Entity [Line Items]
CRC Gross Receivables Sold	317	289
CRC Retained Interests	135	116
CRC Net Receivables Sold	$ 182	$ 173