Variable Interest Entities (Sales and Cash Flows)(Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Duke Energy Ohio [Member]
CRC Receivable Sales	$ 490	$ 521	$ 1,100	$ 1,240
Gain (Loss) on Sale of Accounts Receivable	3	5	7	11
Cash Flows Between Transferor and Transferee, Proceeds from New Transfers	484	560	1,120	1,337
CRC Return Received on Retained Interests	1	3	3	7
CRC Collection Fees Received	1	0	1	0
Duke Energy Indiana [Member]
CRC Receivable Sales	701	630	1,407	1,298
Gain (Loss) on Sale of Accounts Receivable	3	4	6	8
Cash Flows Between Transferor and Transferee, Proceeds from New Transfers	673	646	1,397	1,355
CRC Return Received on Retained Interests	1	3	3	7
CRC Collection Fees Received	$ 1	$ 0	$ 1	$ 0