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Income Taxes (Income Tax Contingencies) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Income Tax Disclosure [Abstract]      
Balance, beginning of period $ (88) $ (98) $ (90)
Increases related to prior year tax positions 0 (1) (11)
Decreases related to prior year tax positions 1 11 2
Settlements 0 0 1
Decrease related to lapse of statute of limitations 13 0 0
Balance, end of period $ (74) $ (88) $ (98)