Federal and Foreign Income Tax - Reconciliation of Effective Income Tax Rate and Statutory Federal Corporate Tax Rate (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 Disclosure [Abstract]
Income before federal and foreign income tax									$ 3,237	$ 1,996	$ 2,199
Tax at statutory federal income tax rate									1,133	699	770
Tax exempt interest income									(222)	(233)	(243)
Other, net									(19)	(15)	(6)
Federal and foreign income tax	$ 217	$ 198	$ 217	$ 260	$ (39)	$ 194	$ 123	$ 173	$ 892	$ 451	$ 521
Income before federal and foreign income tax, percentage of pre-tax income
Tax at statutory federal income tax rate, percentage of pre-tax income									35.00%	35.00%	35.00%
Tax exempt interest income, percentage of pre-tax income									(6.80%)	(11.70%)	(11.00%)
Other, net, percentage of pre-tax income									(0.60%)	(0.70%)	(0.30%)
Actual tax, percentage of pre-tax income									27.60%	22.60%	23.70%