Goodwill, Intangible Assets And Impairments (Schedule of Carrying Value of Emission Allowances) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Gross carrying value at beginning of period	$ 660
Purchases of emission allowances	9		14		93
Gross carrying value at end of period	570		660
Duke Energy Corp [Member]
Gross carrying value at beginning of period	175		274
Purchases of emission allowances	4		14
Sales and consumption of emission allowances	(39)	[1],[2]	(66)	[1],[2]
Impairment of emission allowances	(79)
Other changes	5		(47)
Gross carrying value at end of period	66		175
Duke Energy Ohio [Member]
Purchases of emission allowances	6		12		25
Duke Energy Indiana [Member]
Purchases of emission allowances	$ 2		$ 1		$ 68

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

[2] See Note 3 for a discussion of gains and losses on sales of emission allowances by USFE&G and Commercial Power.