Income Taxes (Reconciliation of Unrecognized Tax Benefits) (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Reconciliation of Unrecognized Tax Benefits
Balance at beginning of period	$ 4,065,000,000	$ 4,045,000,000	$ 3,711,000,000
Increases based on tax positions related to the current period	51,000,000	299,000,000	412,000,000
Increases based on tax positions related to prior periods	267,000,000	127,000,000	70,000,000
Decreases based on tax positions related to prior periods	(141,000,000)	(21,000,000)	(79,000,000)
Decreases related to settlements with taxing authorities	(146,000,000)	(260,000,000)	(56,000,000)
Decreases related to a lapse of applicable statute of limitations		(125,000,000)	(13,000,000)
Balance at end of period	4,096,000,000	4,065,000,000	4,045,000,000
Amount of unrecognized tax benefits, amount if recognized, would favorably affect the effective tax rate in future periods	1,400,000,000	1,600,000,000	1,800,000,000
Recognized interest expense (benefit) (net of federal and state income tax benefits)	50,000,000	(10,000,000)	56,000,000
Interest expense accrued	$ 293,000,000	$ 243,000,000	$ 330,000,000