Income Taxes (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Jun. 30, 2011	Dec. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Mar. 31, 2010
Income Taxes [Abstract]
Income tax (expense) benefit after-tax		$ 15	$ 28	$ 21	$ 12
Additional income tax (expense) benefit after-tax	17		(3)
Reversal of federal tax benefits			22
Reversal of valuation allowance				8
Additional state income tax expense (benefit) after-tax			(2)	6
Adjustment to accrued interest on uncertain tax positions		15		15
Reduction to tax expenses		4			13
Reversal of accrued state interest receivable						6
Other adjustments to income tax benefit						2
State tax benefit carryforward					7
Receipt Of Refund					6
Refund of taxes paid in prior years					138
Unrecognized tax benefits that would impact effective tax rate			29
Interest and penalties related to uncertain tax positions after-tax			14	1	3
Interest and penalties related to uncertain tax positions pre-tax			23	2	5
Accrued interest payable		12	4	12	13
Other taxes for continuing operations			445	427	358
Adjustments relating to unresolved tax matters				$ 1