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	954			398	398
Other comprehensive income, net of tax	90	(3)	4	1		1
Balance at Jun. 30, 2011				9,315	9,336	(19)	(2)
Balance at Mar. 31, 2011
Net income	441			193
Other comprehensive income, net of tax	62
Balance at Jun. 30, 2011				9,315			(2)
Balance at Dec. 31, 2011				9,454	9,473	(17)	(2)
Net income	747			477	477
Other comprehensive income, net of tax	(90)	(15)	6	2		2
Balance at Jun. 30, 2012				9,933	9,950	(15)	(2)
Balance at Mar. 31, 2012
Net income	448			211
Other comprehensive income, net of tax	(150)
Balance at Jun. 30, 2012				$ 9,933			$ (2)