OTHER FINANCIAL DATA - VARIABLE INTEREST ENTITIES (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Variable Interest Entities Disclosure [Abstract]
Equity of variable interest entity	$ 72		$ 76
Secured debt of variable interest entity	342
Amounts Associated With Variable Interest Entities, Operating Revenues, Electric	(1)
Amounts Associated With Variable Interest Entities, Total Operating Revenues	(1)
Amounts Associated With Variable Interest Entities, Cost of Electric Fuel And Purchased Power	(17)	(19)
Amounts Associated With Variable Interest Entities, Operation And Maintenance	17	4
Amounts Associated With Variable Interest Entities, Depreciation And Amortization	7	6
Amounts Associated With Variable Interest Entities, Total Operating Expenses	7	(9)
Amounts Associated With Variable Interest Entities, Operating Income (Loss)	(8)	9
Amounts Associated With Variable Interest Entities, Interest Expense	(3)	(3)
Amounts Associated With Variable Interest Entities, Net Income (Loss)	(11)	6
Amounts Associated With Variable Interest Entities, (Earnings) Losses Attributable Noncontrolling Interests	$ 11	$ (6)