Regulatory Matters (Narrative) (Details) (USD $)	3 Months Ended		6 Months Ended			3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		12 Months Ended			6 Months Ended								6 Months Ended				3 Months Ended	6 Months Ended			3 Months Ended	6 Months Ended	3 Months Ended			6 Months Ended		12 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011	Jun. 30, 2012 Duke Energy Indiana [Member]	Jun. 30, 2011 Duke Energy Indiana [Member]	Jun. 30, 2012 Duke Energy Indiana [Member]	Jun. 30, 2011 Duke Energy Indiana [Member]	Jun. 30, 2012 Duke Energy Ohio [Member]	Jun. 30, 2011 Duke Energy Ohio [Member]	Jun. 30, 2012 Duke Energy Ohio [Member]	Jun. 30, 2011 Duke Energy Ohio [Member]	Dec. 31, 2014 Duke Energy Ohio [Member]	Dec. 31, 2013 Duke Energy Ohio [Member]	Dec. 31, 2012 Duke Energy Ohio [Member]	Jun. 30, 2012 Duke Energy Ohio [Member] Ohio Electric Rate Case [Member]	Jun. 30, 2012 Duke Energy Ohio [Member] Ohio Natural Gas Rate Case [Member]	Jun. 30, 2012 Duke Energy Carolinas [Member]	Jun. 30, 2012 Duke Energy Carolinas [Member] Minimum [Member]	Jun. 30, 2012 Duke Energy Carolinas [Member] Maximum [Member]	Jun. 30, 2012 Duke Energy Carolinas [Member] North Carolina Rate Case [Member]	Jun. 30, 2012 Duke Energy Carolinas [Member] South Carolina Rate Case [Member]	Nov. 30, 2009 Edwardsport IGCC Plant [Member] Duke Energy Indiana [Member]	Jun. 30, 2012 Edwardsport IGCC Plant [Member] Duke Energy Indiana [Member] September 7, 2006 [Member]	Jun. 30, 2012 Edwardsport IGCC Plant [Member] Duke Energy Indiana [Member] May 1, 2008 [Member]	Jun. 30, 2012 Edwardsport IGCC Plant [Member] Duke Energy Indiana [Member] November 24, 2009 [Member]	Jun. 30, 2012 Edwardsport IGCC Plant [Member] Duke Energy Indiana [Member] April 16, 2010 [Member]	Sep. 30, 2010 Edwardsport IGCC Plant [Member] Duke Energy Indiana [Member] September 17, 2010 - Settlement Agreement [Member]	Jun. 30, 2012 Edwardsport IGCC Plant [Member] Duke Energy Indiana [Member] September 17, 2010 - Settlement Agreement [Member] basispoints	Jun. 30, 2012 Edwardsport IGCC Plant [Member] Duke Energy Indiana [Member] March 10, 2010 [Member]	Jun. 30, 2012 Edwardsport IGCC Plant [Member] Duke Energy Indiana [Member] June 27, 2011 [Member]	Sep. 30, 2011 Edwardsport IGCC Plant [Member] Duke Energy Indiana [Member] October 19, 2011 [Member]	Jun. 30, 2012 Edwardsport IGCC Plant [Member] Duke Energy Indiana [Member] October 19, 2011 [Member]	Mar. 31, 2012 Edwardsport IGCC Plant [Member] Duke Energy Indiana [Member] April 30, 2012 Settlement Agreement [Member]	Jun. 30, 2012 Edwardsport IGCC Plant [Member] Duke Energy Indiana [Member] April 30, 2012 Settlement Agreement [Member]	Jun. 30, 2012 Dan River Facility [Member] Duke Energy Carolinas [Member]	Jun. 30, 2012 Cliffside Unit 6 [Member] Duke Energy Carolinas [Member] MWh	Jun. 30, 2012 William State Lee III Nuclear Station [Member] Duke Energy Carolinas [Member] MWh	Dec. 31, 2011 Regional Transmission Organization Realignment [Member] Duke Energy Ohio [Member]	Jun. 30, 2012 Regional Transmission Organization Realignment [Member] Duke Energy Ohio [Member]
Ohio ESP non-bypassable stability charge														$ 110,000,000	$ 110,000,000	$ 110,000,000
Approved Rate Increase Amount by State Commission																						309,000,000	93,000,000
Average increase in retail revenues, percentage																	5.10%	6.60%				7.20%	5.98%
Requested Rate Increase Amount to State Commission																	87,000,000	45,000,000
Rate Increase Begin Date																	2013	2013				February 2012	February 6, 2012
Return on equity percentage																						10.50%	10.50%
Capital structure, Equity percentage																						53.00%	53.00%
Capital structure, Long-term debt percentage																						47.00%	47.00%
Required shareholder contribution to low income customers or agencies.																						11,000,000	4,000,000
Estimated capital cost of new utility plant, excluding AFUDC																																						1,800,000,000
Estimated capital cost of new utility plant, including AFUDC																																					710,000,000
Plant capacity, MW																																						825	1,117
Estimated AFUDC on Capital Project																									120,000,000	125,000,000		160,000,000										600,000,000
Revised Afudc Financing Costs																																						400,000,000
Federal Clean Coal Tax Credits								134,000,000											125,000,000																			125,000,000
Edwardsport IGCC original estimated and approved capital cost, including AFUDC																									1,985,000,000
Edwardsport IGCC revised estimated capital cost, including AFUDC																										2,350,000,000		2,880,000,000		2,760,000,000
Edwardsport IGCC estimated additional capital cost																											150,000,000	530,000,000
Edwardsport IGCC - Cost Cap for Customers																														2,975,000,000						2,595,000,000
Edwardsport IGCC basis point reduction in the equity return for project construction costs																														150
Edwardsport IGCC committed costs, as claimed by intervenors																								1,600,000,000
Edwardsport IGCC Impairment charges	0	9,000,000	402,000,000	9,000,000		0	0	400,000,000	0	0	9,000,000	0	9,000,000																44,000,000				222,000,000		400,000,000
Edwardsport IGCC impairment and other charges																																			420,000,000
Edwarsport IGCC original customer rate increase																															19.00%
Edwardsport IGCC revised customer rate increase																															16.00%
Edwardsport IGCC revised estimated capital costs, excluding AFUDC																															2,720,000,000	2,820,000,000		2,980,000,000
Edwardsport IGCC legal fee charges from settlement																																			20,000,000
MVP project costs approved by MISO																																								5,200,000,000
MISO exit fees not eligible for recovery																																								121,000,000
MISO Exit Liability	23,000,000		23,000,000		32,000,000																																			110,000,000	97,000,000
MISO exit recorded to regulatory assets																																								74,000,000
MISO exit fees recorded to expense																																								36,000,000
Indiana Carbon Sequestration requested amount of environmental cost recovery								121,000,000
Indiana Carbon Sequestration recommended approval amount of environmental cost recovery								33,000,000
Amended deferral amount to cover environmental cost								42,000,000
VC Summer Ownership Percentage																				5.00%	10.00%
EPA Compliance Capital Costs								$ 450,000,000