Variable Interest Entities (Sales and Cash Flows)(Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Duke Energy Ohio [Member]
Variable Interest Entity [Line Items]
CRC Receivable Sales	$ 638	$ 610
Gain (Loss) on Sale of Accounts Receivable	(3)	(4)
Cash Flows Between Transferor and Transferee, Proceeds from New Transfers	617	636
CRC Return Received on Retained Interests	1	2
CRC Collection Fees Received	0	0
Duke Energy Indiana [Member]
Variable Interest Entity [Line Items]
CRC Receivable Sales	747	706
Gain (Loss) on Sale of Accounts Receivable	(3)	(3)
Cash Flows Between Transferor and Transferee, Proceeds from New Transfers	725	724
CRC Return Received on Retained Interests	2	2
CRC Collection Fees Received	$ 0	$ 0