Regulatory Matters (Narrative) (Details) (USD $)	1 Months Ended			3 Months Ended		12 Months Ended															0 Months Ended				1 Months Ended		3 Months Ended		0 Months Ended				1 Months Ended	3 Months Ended		12 Months Ended	1 Months Ended	12 Months Ended		0 Months Ended	1 Months Ended	12 Months Ended	1 Months Ended	3 Months Ended	12 Months Ended
	Aug. 31, 2011	Jul. 31, 2011	Jan. 31, 2008	Dec. 31, 2011	Sep. 30, 2011	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Duke Energy Indiana [Member]	Dec. 31, 2010 Duke Energy Indiana [Member]	Dec. 31, 2009 Duke Energy Indiana [Member]	Dec. 31, 2011 Duke Energy Ohio [Member]	Dec. 31, 2010 Duke Energy Ohio [Member]	Dec. 31, 2009 Duke Energy Ohio [Member]	Dec. 31, 2011 Duke Energy Carolinas [Member]	Dec. 31, 2010 Duke Energy Carolinas [Member]	Dec. 31, 2009 Duke Energy Carolinas [Member]	Jul. 14, 2010 Storm Cost Deferrals [Member] Duke Energy Indiana [Member]	Jan. 11, 2011 Storm Cost Recovery [Member] Duke Energy Ohio [Member]	Dec. 11, 2009 Storm Cost Recovery [Member] Duke Energy Ohio [Member]	Nov. 24, 2009 IGCC Power Plan [Member] Duke Energy Indiana [Member]	May 01, 2008 IGCC Power Plan [Member] Duke Energy Indiana [Member]	Nov. 20, 2007 IGCC Power Plan [Member] Duke Energy Indiana [Member]	Sep. 07, 2006 IGCC Power Plan [Member] Duke Energy Indiana [Member]	Sep. 30, 2010 IGCC Power Plan [Member] Duke Energy Indiana [Member]	Apr. 30, 2010 IGCC Power Plan [Member] Duke Energy Indiana [Member]	Sep. 30, 2010 IGCC Power Plan [Member] Duke Energy Indiana [Member]	Aug. 31, 2007 IGCC Power Plan [Member] Duke Energy Indiana [Member]	Apr. 26, 2011 PJM Transmission Expansion Cost [Member] Duke Energy Ohio [Member]	Oct. 30, 2009 Edwardsport IGCC Plant [Member] Duke Energy Indiana [Member]	Jul. 07, 2009 Edwardsport IGCC Plant [Member] Duke Energy Indiana [Member]	Sep. 07, 2006 Edwardsport IGCC Plant [Member] Duke Energy Indiana [Member] mW	Jul. 31, 2011 Edwardsport IGCC Plant [Member] 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, 2011 Edwardsport IGCC Plant [Member] Duke Energy Indiana [Member]	Jun. 30, 2008 Dan River Facility [Member] Duke Energy Carolinas [Member] mW	Dec. 31, 2011 Dan River Facility [Member] Duke Energy Carolinas [Member]	Dec. 31, 2011 Buck Facility [Member] Duke Energy Carolinas [Member]	Mar. 21, 2007 Cliffside Unit 6 [Member] Duke Energy Carolinas [Member] mW	Mar. 31, 2010 Cliffside Unit 6 [Member] Duke Energy Carolinas [Member]	Dec. 31, 2011 Cliffside Unit 6 [Member] Duke Energy Carolinas [Member]	Dec. 31, 2007 William State Lee III Nuclear Station [Member] Duke Energy Carolinas [Member] mW	Mar. 31, 2011 William State Lee III Nuclear Station [Member] Duke Energy Carolinas [Member]	Dec. 31, 2009 William State Lee III Nuclear Station [Member] Duke Energy Carolinas [Member]
Non-bypassable stability charge						$ 110,000,000
Request for rate increase, expressed as a percentage	15.00%	15.00%
Request for rate increase, amount	216,000,000	646,000,000
Return on equity	11.50%	11.50%
Deferral storm expense																		12,000,000	14,000,000	31,000,000
Estimated capital cost																						2,350,000,000
Plant capacity																																618					620			800
Estimated allowance for funds used during construction																						125,000,000		120,000,000		160,000,000
Ownership of project																												100.00%
Approved estimated capital cost																							1,985,000,000
Additional capital cost																					150,000,000
Revised estimated capital cost																										530,000,000							2,820,000,000
Requested revised estimated capital cost included AFUDC, and continuation of the existing cost recovery treatment																										2,880,000,000
Original cost estimate																									2,350,000,000
Authorized estimated capital cost																									2,760,000,000
Increase in AFUDC financing costs resulting from delay in CWIP						260,000,000	234,000,000	153,000,000	88,000,000	56,000,000	29,000,000				168,000,000	174,000,000	125,000,000
Pre-tax impairment charge				(59,000,000)	(301,000,000)	335,000,000	726,000,000	420,000,000	234,000,000	44,000,000		89,000,000	837,000,000	769,000,000	12,000,000																			222,000,000	44,000,000
Cap project cost that could be passed on to customers																									2,975,000,000
Pre-tax charge to earnings due to reduction in the return of equity																											44,000,000
Plant capacity of each reactor																																											1,117
Aggregate maximum amount of project development and pre-construction costs																																													350,000,000
Basis point reduction in the equity return for project construction costs																									150
Counterparty option to purchase maximum ownership interest																																												20.00%
Estimated plant cost excluding allowance for funds used during construction																																									1,800,000,000
Expected net output of plant capacity																																								825
Estimated reduction in AFUDC financing costs																																									400,000,000
AFUDC excluded from cost estimate			600,000,000
Estimated reduction in plant cost due to federal tax credits																																										125,000,000
Estimated plant cost including allowance for funds used during construction																																						716,000,000	700,000,000
Proposed construction costs cap																																				2,720,000,000
Original customer rate increase																																				19.00%
Recovery costs that would not be sought																													121,000,000
Requested amount of environmental cost recovery																															121,000,000
Revised customer rate increase																																				16.00%
Recommended approval amount of environmental cost recovery																															33,000,000
Committed Costs																																				1,600,000,000
Amended deferral amount to cover environmental cost																														42,000,000
Excess estimated project costs, expected to be approved						5,200,000,000
MTEP exit costs												110,000,000
MTEP regulatory assets												$ 74,000,000