Condensed Consolidated Statements of Equity - Indiana (USD $) In Millions	Total	Retained Earnings [Member]	Net Gains (Losses) on Cash Flow Hedges [Member]	Pension And OPEB Related Adjustments To AOCI [Member]	Duke Energy Indiana [Member]	Duke Energy Indiana [Member] Common Stock [Member]	Duke Energy Indiana [Member] Additional Paid In Capital [Member]	Duke Energy Indiana [Member] Retained Earnings [Member]	Duke Energy Indiana [Member] Net Gains (Losses) on Cash Flow Hedges [Member]
Balance at Dec. 31, 2010			$ 8		$ 3,567	$ 1	$ 1,358	$ 2,200
Net income	1,424	1,418			113			113
Other comprehensive income, net of tax	(198)		(49)	(6)	(1)				(1)
Transfer of Vermillion Generating Station					0
Balance at Sep. 30, 2011					3,679	1	1,358	2,313	7
Balance at Jun. 30, 2011
Net income	470				(31)
Other comprehensive income, net of tax	(288)
Balance at Sep. 30, 2011					3,679	1	1,358
Balance at Dec. 31, 2011						1
Net income		1,333
Balance at Jun. 30, 2012
Balance at Dec. 31, 2011	22,772				3,734	1	1,358	2,368	7
Net income	1,345				(109)			(109)
Other comprehensive income, net of tax	(110)		(19)	(15)	(1)				(1)
Transfer of Vermillion Generating Station					26		26
Balance at Sep. 30, 2012	40,905				3,650	1	1,384	2,259	6
Balance at Jun. 30, 2012
Net income	598				(19)
Other comprehensive income, net of tax	(20)
Balance at Sep. 30, 2012	$ 40,905				$ 3,650	$ 1