Regulatory Matters (Details) (USD $)	1 Months Ended			6 Months Ended		0 Months Ended				1 Months Ended		3 Months Ended		0 Months Ended					1 Months Ended	6 Months Ended	1 Months Ended	6 Months Ended		0 Months Ended	1 Months Ended	6 Months Ended	1 Months Ended	6 Months Ended	12 Months Ended						6 Months Ended
	Aug. 31, 2011	Jul. 31, 2011	Jan. 31, 2008	Jun. 30, 2011	Jun. 30, 2010	Nov. 24, 2009 Duke Energy Indiana [Member] IGCC Power Plan [Member]	May 01, 2008 Duke Energy Indiana [Member] IGCC Power Plan [Member]	Oct. 20, 2007 Duke Energy Indiana [Member] IGCC Power Plan [Member]	Sep. 07, 2006 Duke Energy Indiana [Member] IGCC Power Plan [Member]	Sep. 30, 2010 Duke Energy Indiana [Member] IGCC Power Plan [Member]	Apr. 30, 2010 Duke Energy Indiana [Member] IGCC Power Plan [Member]	Sep. 30, 2010 Duke Energy Indiana [Member] IGCC Power Plan [Member]	Aug. 31, 2007 Duke Energy Indiana [Member] IGCC Power Plan [Member]	Apr. 26, 2011 Duke Energy Ohio [Member] PJM Transmission Expansion Cost [Member]	Apr. 26, 2011 Duke Energy Ohio [Member] RTO Realignment Cost [Member]	Oct. 30, 2009 Duke Energy Indiana [Member] Edwardsport IGCC Plant [Member]	Jul. 07, 2009 Duke Energy Indiana [Member] Edwardsport IGCC Plant [Member]	Sep. 07, 2006 Duke Energy Indiana [Member] Edwardsport IGCC Plant [Member] mW	Jul. 31, 2011 Duke Energy Indiana [Member] Edwardsport IGCC Plant [Member]	Jun. 30, 2011 Duke Energy Indiana [Member] Edwardsport IGCC Plant [Member]	Jun. 30, 2008 Duke Energy Carolinas [Member] Dan River Facility [Member] mW	Jun. 30, 2011 Duke Energy Carolinas [Member] Dan River Facility [Member]	Jun. 30, 2011 Duke Energy Carolinas [Member] Buck Facility [Member]	Mar. 21, 2007 Duke Energy Carolinas [Member] Cliffside Unit 6 [Member] mW	Mar. 31, 2010 Duke Energy Carolinas [Member] Cliffside Unit 6 [Member]	Jun. 30, 2011 Duke Energy Carolinas [Member] Cliffside Unit 6 [Member]	Dec. 31, 2007 Duke Energy Carolinas [Member] William State Lee III Nuclear Station [Member] mW	Jun. 30, 2011 Duke Energy Carolinas [Member] William State Lee III Nuclear Station [Member]	Dec. 31, 2013 Duke Energy Carolinas [Member] William State Lee III Nuclear Station [Member]	Dec. 31, 2009 Duke Energy Carolinas [Member] William State Lee III Nuclear Station [Member]	Jul. 14, 2010 Duke Energy Indiana [Member] Storm Cost Deferrals [Member]	Jan. 11, 2011 Duke Energy Ohio [Member] Storm Cost Recovery [Member]	Dec. 31, 2010 Duke Energy Ohio [Member] Storm Cost Recovery [Member]	Dec. 11, 2009 Duke Energy Ohio [Member] Storm Cost Recovery [Member]	Jun. 30, 2011 Duke Energy Indiana [Member]	Jun. 30, 2010 Duke Energy Indiana [Member]	Jun. 30, 2011 Duke Energy Carolinas [Member]	Jun. 30, 2010 Duke Energy Carolinas [Member]
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
Public utilities disallowance of deferred storm costs																																	17,000,000
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
Costs necessary to keep project available, not to exceed		120,000,000
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
Project cost consisting of labor productivity trends																			100,000,000
Project cost, start-up even risk																			30,000,000
Increase in AFUDC financing costs resulting from delay in CWIP				123,000,000	110,000,000														115,000,000																39,000,000	23,000,000	82,000,000	83,000,000
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																														230,000,000
Basis point reduction in the equity return for project construction costs										150
Request approval to continue to incur project development and pre-construction costs																													459,000,000
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	20,000,000
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
Amended deferral amount to cover environmental cost																$ 42,000,000