Related Party Transactions(AssetsLiabilities)(Details) (USD $) In Millions, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2012	Dec. 31, 2011
Duke Energy Carolinas [Member]
Receivables	$ 0	$ 2
Accounts payable	(97)	(157)
Noncurent assets	111	111
Noncurrent liabilities	(64)	(64)
Deferred income taxes	(4,891)	(4,555)
Accrued taxes	(10)	(14)
Other current assets	95	95
Duke Energy Ohio [Member]
Receivables	7	15
Accounts payable	(73)	(84)
Noncurent assets	28	22
Noncurrent liabilities	(34)	0
Deferred income taxes	(1,882)	(1,798)
Accrued taxes	(4)
Other current assets	98	76
Duke Energy Indiana [Member]
Receivables	16	18
Accounts payable	(38)	(72)
Noncurent assets	2	2
Noncurrent liabilities	(22)	(22)
Deferred income taxes	(835)	(927)
Accrued taxes	0	(25)
Other current assets	7	13
Other current liabilities	$ (8)