Condensed Consolidated Statements Of Common Stockholder's Equity And Comprehensive Income - Indiana (USD $) In Millions, unless otherwise specified	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 (Losses) Gains On Cash Flow Hedges [Member]		Duke Energy Indiana [Member]		Retained Earnings [Member]	Net (Losses) Gains On Cash Flow Hedges [Member]		Total
Balance at Dec. 31, 2008	$ 1	$ 868	$ 1,714	$ 11		$ 2,594
Net income (loss)			201			201		1,075			1,085
Other comprehensive income (loss)
Reclassification into earnings from cash flow hedges				(1)	[1]	(1)	[1]		(18)	[2]	(18)	[2]
Total comprehensive income (loss)						200					1,457
Capital contribution from parent		140				140
Balance at Dec. 31, 2009	1	1,008	1,915	10		2,934
Net income (loss)			285			285		1,320			1,323
Other comprehensive income (loss)
Reclassification into earnings from cash flow hedges				(2)	[1]	(2)	[1]		(3)	[2]	(3)	[2]
Total comprehensive income (loss)						283					1,696
Capital contribution from parent		350				350
Balance at Dec. 31, 2010	1	1,358	2,200	8		3,567					22,522
Net income (loss)			168			168		1,706			1,714
Other comprehensive income (loss)
Reclassification into earnings from cash flow hedges				(1)	[1]	(1)	[1]		(4)	[2]	(4)	[2]
Total comprehensive income (loss)						167					1,471
Balance at Dec. 31, 2011	$ 1	$ 1,358	$ 2,368	$ 7		$ 3,734					$ 22,772

[1] a) Net of $1 tax benefit in 2011, 2010 and 2009.

[2] Net of $1 tax expense in 2011, insignificant tax expense in 2010 and $10 tax expense in 2009.