v2.4.0.6
Income Taxes (Reconciliation of Unrecognized Tax Benefits) (Details) (USD $)
 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Reconciliation of Unrecognized Tax Benefits      
Balance at beginning of period $ 4,045,000,000 $ 3,711,000,000 $ 4,052,000,000
Increases based on tax positions related to the current period 299,000,000 412,000,000 478,000,000
Increases based on tax positions related to prior periods 127,000,000 70,000,000 479,000,000
Decreases based on tax positions related to prior periods (21,000,000) (79,000,000) (881,000,000)
Decreases related to settlements with taxing authorities (260,000,000) (56,000,000) (356,000,000)
Decreases related to a lapse of applicable statute of limitations (125,000,000) (13,000,000) (61,000,000)
Balance at end of period 4,065,000,000 4,045,000,000 3,711,000,000
Amount of unrecognized tax benefits, amount if recognized, would favorably affect the effective tax rate in future periods 1,600,000,000 1,800,000,000 1,700,000,000
Recognized interest expense (benefit) (net of federal and state income tax benefits) (10,000,000) 56,000,000 (93,000,000)
Interest expense accrued 243,000,000 330,000,000 274,000,000
Increase in unrecognized tax benefit $ 299,000,000   $ 345,000,000