Regulatory Matters (Narrative) (Details) (USD $)	0 Months Ended		1 Months Ended		3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended		0 Months Ended		1 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
	Feb. 06, 2012	Jan. 31, 2008	Feb. 29, 2012	Jan. 31, 2008	Mar. 31, 2012 MW	Dec. 31, 2011	Mar. 31, 2012 Duke Energy Indiana [Member]	Dec. 31, 2012 Duke Energy Ohio [Member]	Dec. 31, 2011 Duke Energy Ohio [Member]	Feb. 06, 2012 Duke Energy Carolinas [Member]	Jan. 25, 2012 Duke Energy Carolinas [Member]	Feb. 29, 2012 Duke Energy Carolinas [Member]	Feb. 29, 2008 Duke Energy Carolinas [Member]	Dec. 31, 2009 Duke Energy Carolinas [Member]	Mar. 31, 2012 Duke Energy Carolinas [Member]	Dec. 31, 2011 Duke Energy Carolinas [Member]	Sep. 07, 2006 IGCC Power Plan [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	Mar. 31, 2012 Buck Facility [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, amount												309,000,000
Return on equity										10.50%			10.50%
Capital structure equity percentage	53.00%											53.00%
long term debt, regulatory assets percentage			47.00%							47.00%
Customer bills increase in the near term														7.20%
Amount of shareholder contribution to agencies														11,000,000
Terms of agreement											5.98%
Loans Receivable, Gross, Commercial, Development										93,000,000
Contibution advances										4,000,000
Estimated capital cost		1,800,000,000																	2,350,000,000
Plant capacity, MW																													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
Pre-tax impairment charge					402,000,000		400,000,000																								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, MW																																					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																																				710,000,000
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
Committed to retire MW					1,667
Retired MW					311
Generation facilities to be retired, net					79,000,000	80,000,000									79,000,000	80,000,000																			79,000,000
Estimate cost																	$ 1,985,000,000