Goodwill (Schedule of Carrying Value of Emission Allowances) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Finite-Lived Intangible Assets [Line Items]
Gross carrying value at beginning of period	$ 570
Amounts Acquired In Progress Merger	29
Purchases Of Emission Allowances		4
Sales And Consumption Of Emission Allowances	(15)	(39)	[1],[2]
Impairments of emission allowances		(79)
Other Changes To Emission Allowances		5
Gross carrying value at end of period	595	570
Duke Energy Ohio [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying value at beginning of period	310
Purchases Of Emission Allowances		1
Sales And Consumption Of Emission Allowances	(5)	(18)	[1],[2]
Impairments of emission allowances		(79)
Gross carrying value at end of period	306	310
Duke Energy Indiana [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying value at beginning of period	61
Purchases Of Emission Allowances		2
Sales And Consumption Of Emission Allowances	(8)	(21)	[1]
Other Changes To Emission Allowances		7
Gross carrying value at end of period	$ 53	$ 61

[1] Carrying value of emission allowances are recognized via a charge to expense when consumed.

[2] See Note 2 for additional information regarding gains and losses on sales of emission allowances by USFE&G and Commercial Power.