Income Taxes - Provision for Income Taxes (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Current:
Federal	$ 559	$ 664	$ 325
State	45	60	57
Foreign	22	8	1
Total current tax expense	626	732	383
Deferred:
Federal	(172)	(34)	13
State	(6)	(3)	6
Deferred Foreign Income Tax Expense (Benefit)	(7)	0	0
Total deferred tax expense (benefit)	(185)	(37)	19
Provision for income taxes	$ 441	$ 695	$ 402