INCOME TAXES (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
INCOME TAXES
Statutory federal income tax rate (as a percent)									35.00%
Income	$ 98	$ 105	$ 56	$ 128	$ 94	$ 101	$ 54	$ 127	$ 387	$ 376	$ 348
Income Tax Expense									168	159	167
Preferred stock dividends											9
Income Before Income Tax Expense									555	535	524
Reconciliation between actual income tax expense and the amount calculated from the application of the statutory federal income tax
Income taxes on above at statutory federal income tax rate									194	187	183
Increases (decreases) attributed to:
State income taxes (less federal income tax effect)									15	9	14
Amortization of state investment tax credits (less federal income tax effect)									(16)	(18)	(6)
Allowance for equity funds used during construction									(5)	(8)	(10)
Deductible dividends-Stock Purchase Savings Plan									(9)	(9)	(8)
Amortization of federal investment tax credits									(3)	(3)	(3)
Domestic production activities deduction									(6)		(4)
Other differences, net									(2)	1	1
Total income tax expense									$ 168	$ 159	$ 167