Condensed Consolidated Statements of Equity - Carolinas (USD $) In Millions	Total	Accumulated Net Gain Loss From Designated Or Qualifying Cash Flow Hedges [Member]	Other Equity [Member]	Duke Energy Carolinas [Member]	Duke Energy Carolinas [Member] Members Equity [Member]	Duke Energy Carolinas [Member] Accumulated Net Gain Loss From Designated Or Qualifying Cash Flow Hedges [Member]	Duke Energy Carolinas [Member] Other Equity [Member]
Balance at Dec. 31, 2010				$ 8,916	$ 8,938	$ (20)	$ (2)
Net income	1,424			709	709
Other comprehensive income, net of tax	(198)	(49)	7	3		3
Distributions to parent				0
Balance at Sep. 30, 2011				9,628	9,647	(17)	(2)
Balance at Jun. 30, 2011
Net income	470			311
Other comprehensive income, net of tax	(288)
Balance at Sep. 30, 2011				9,628			(2)
Balance at Dec. 31, 2011				9,454	9,473	(17)	(2)
Net income	1,345			735	735
Other comprehensive income, net of tax	(110)	(19)	9	2		2
Distributions to parent				(250)	(250)
Balance at Sep. 30, 2012				9,941	9,958	(15)	(2)
Balance at Jun. 30, 2012
Net income	598			258
Other comprehensive income, net of tax	(20)
Balance at Sep. 30, 2012				$ 9,941			$ (2)