Provision for Federal and Foreign Income Tax Expense (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Federal income taxes:
Current	$ 387	$ 912	$ 600
Deferred	925	9	561
Total federal income taxes	1,312	921	1,161
Foreign income taxes:
Current	14	38	8
Deferred	1	5	(5)
Total foreign income taxes	15	43	3
Income tax expense	$ 1,327	$ 964	$ 1,164