Income Taxes - Unrecognized Tax Benefits (Details 3) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Unrecognized Tax Benefits
Income Tax Examination, Penalties and Interest Expense	$ 147,000,000	$ 184,000,000	$ (54,000,000)
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	4,200,000,000	4,000,000,000	3,800,000,000
Reconciliation of the beginning and ending amount of unrecognized tax benefits
Balance at January 1,	7,189,000,000	7,767,000,000	6,608,000,000
Increases based on tax positions related to the current period	680,000,000	516,000,000	813,000,000
Decreases based on tax positions related to the current period	0	(110,000,000)	(24,000,000)
Increases based on tax positions related to prior periods	234,000,000	496,000,000	1,681,000,000
Decreases based on tax positions related to prior periods	(853,000,000)	(1,433,000,000)	(1,198,000,000)
Decreases related to settlements with taxing authorities	(50,000,000)	(16,000,000)	(74,000,000)
Decreases related to a lapse of applicable statute of limitations	(42,000,000)	(31,000,000)	(39,000,000)
Balance at December 31,	7,158,000,000	7,189,000,000	7,767,000,000
Income tax expense, penalties and interest expense
Income Tax Examination, Penalties and Interest Accrued	$ 1,900,000,000	$ 1,700,000,000