Commitments And Contingencies (Details) (USD $)	0 Months Ended		1 Months Ended		3 Months Ended	9 Months Ended	12 Months Ended			60 Months Ended						9 Months Ended
	Sep. 03, 2010	Jun. 30, 2009	Jul. 31, 2010 gal	Sep. 30, 2008	Mar. 31, 2009	Sep. 30, 2011	Dec. 31, 2009	Dec. 31, 2010	Sep. 30, 2011 Duke Energy Ohio [Member] Reserve For Environmental Costs [Member]	Dec. 31, 2015 Duke Energy Carolinas [Member] Coal Combustion Product Management [Member]	Dec. 31, 2015 Duke Energy Ohio [Member] Coal Combustion Product Management [Member]	Dec. 31, 2015 Duke Energy Indiana [Member] Coal Combustion Product Management [Member]	Dec. 31, 2015 Coal Combustion Product Management [Member]	Sep. 30, 2011 Litigation And Legal Proceedings [Member]	Dec. 31, 2010 Litigation And Legal Proceedings [Member]	Sep. 30, 2011 Federal Advance Clean Coal Tax Credits Associated With Its Construction Of Cliffside Unit6 [Member]	Sep. 30, 2011 Federal Advance Clean Coal Tax Credits Associated With Its Construction Of Edwardsport IGCC Plant [Member]	Sep. 30, 2011 Duke Energy Ohio [Member]
Remediation reserve									$ 36,000,000
Aquatic protection requirements for existing facilities, in gallons			2,000,000
Environmental exit costs, anticipated cost										131,000,000	70,000,000	168,000,000	369,000,000					90,000,000
DEIGP electric transmission charges promulgated by ANEEL		69,000,000
Additional electric transmission fine assessed					9,000,000
Pre-tax charge recorded associated with the resolutions							33,000,000
DEIGP's obligation to expand installed generation capacity, percent						15.00%
Daily penalty faced if DEIGP fails to present a detailed expansion plan						16,000
Alleged amount borrowed from a consortium of banks	1,200,000,000
Litigation settlement, gross				150,000,000
Probable insurance recoveries						813,000,000		850,000,000
Investment tax credit																125,000,000	134,000,000
Related injuries and damages claims														830,000,000	900,000,000
Deferred Costs									$ 64,000,000