Variable Interest Entities (Sales and Cash Flows)(Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Duke Energy Ohio [Member]
CRC Receivable Sales	$ 518	$ 592	$ 1,618	$ 1,832
Gain (Loss) on Sale of Accounts Receivable	3	5	10	16
Cash Flows Between Transferor and Transferee, Proceeds from New Transfers	531	615	1,651	1,952
CRC Return Received on Retained Interests	1	3	4	10
CRC Collection Fees Received	0	0	1	1
Duke Energy Indiana [Member]
CRC Receivable Sales	711	711	2,118	2,009
Gain (Loss) on Sale of Accounts Receivable	3	5	9	13
Cash Flows Between Transferor and Transferee, Proceeds from New Transfers	733	696	2,130	2,051
CRC Return Received on Retained Interests	2	3	5	10
CRC Collection Fees Received	$ 0	$ 0	$ 1	$ 1