Income Taxes - Components of Income Tax Expense (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Federal
Current	$ 490	$ 404
Deferred	12	68
Federal income tax	502	472
State
Current	58	50
Deferred	(2)	5
State income tax	56	55
Total income tax provision	$ 558	$ 527