OTHER FINANCIAL DATA - VARIABLE INTEREST ENTITIES (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Variable Interest Entities Disclosure [Abstract]
Secured debt of variable interest entity	$ 352
Amounts Associated With Variable Interest Entities, Cost of Electric Fuel And Purchased Power	(19)	(17)
Amounts Associated With Variable Interest Entities, Operation And Maintenance	4	4
Amounts Associated With Variable Interest Entities, Depreciation And Amortization	6	6
Amounts Associated With Variable Interest Entities, Total Operating Expenses	(9)	(7)
Amounts Associated With Variable Interest Entities, Operating Income	9	7
Amounts Associated With Variable Interest Entities, Interest Expense	(3)	(3)
Amounts Associated With Variable Interest Entities, Net Income	6	4
Amounts Associated With Variable Interest Entities, (Earnings) Losses Attributable Noncontrolling Interests	$ (6)	$ (4)