Goodwill, Intangible Assets And Impairments (Narrative) (Details) (USD $)	3 Months Ended			12 Months Ended										3 Months Ended		12 Months Ended	3 Months Ended	12 Months Ended		3 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2010	Dec. 31, 2011 mW	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Duke Energy Ohio [Member] mW		Dec. 31, 2010 Duke Energy Ohio [Member]	Dec. 31, 2009 Duke Energy Ohio [Member]	Dec. 31, 2011 Duke Energy Indiana [Member] mW		Dec. 31, 2010 Duke Energy Indiana [Member]	Sep. 30, 2011 Edwardsport IGCC Plant [Member] Duke Energy Indiana [Member]	Sep. 30, 2010 Edwardsport IGCC Plant [Member] Duke Energy Indiana [Member]	Dec. 31, 2010 Edwardsport IGCC Plant [Member] Duke Energy Indiana [Member]	Jun. 30, 2010 Commercial Power [Member]	Dec. 31, 2011 Commercial Power [Member] mW	Dec. 31, 2009 Commercial Power [Member]	Sep. 30, 2011 Emission Allowances [Member] Duke Energy Ohio [Member]
Goodwill impairment charge			$ 500,000,000		$ 175,000,000	$ 130,000,000											$ 500,000,000	$ 413,000,000	$ 371,000,000
Pre-tax impairment charges related to certain generating assets and emission allowances																	160,000,000
Pre-tax impairment charge	$ (59,000,000)	$ (301,000,000)		$ 335,000,000	$ 726,000,000	$ 420,000,000	$ 89,000,000		$ 837,000,000	$ 769,000,000	$ 234,000,000		$ 44,000,000	$ 222,000,000	$ 44,000,000	$ 44,000,000	$ 660,000,000		$ 42,000,000	$ 79,000,000
Coal-fired generation capacity, in megawatts				3,329			948	[1]			1,025	[2],[3]						4,000
Gas-fired generation capacity, in megawatts																		3,600

[1] Includes Wabash River units 2-6 and Gallagher units 1 and 3.

[2] Includes Beckjord and Miami Fort unit 6.

[3] Beckjord has no remaining net book value - See Note 12 for additional information.