Federal and Foreign Income Tax - Income Tax Expense and Taxes Paid (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income tax expense and taxes paid
Current tax, United States									$ 791	$ 276	$ 260
Current tax, Foreign									91	143	236
Deferred tax, principally United States									10	32	25
Federal and foreign income tax	217	198	217	260	(39)	194	123	173	892	451	521
Federal and foreign income taxes paid									$ 789	$ 472	$ 598