Deferred Acquisition Costs - Deferred Policy Acquisition Costs and Asset Reconciliation (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Deferred policy acquisition costs asset at beginning of period	$ 470	$ 477
Capitalized deferred policy acquisition costs	198	170
Amortized deferred policy acquisition costs	(179)	(156)
Amortized shadow deferred policy acquisition costs	2	(8)
Deferred policy acquisition costs asset at end of period	$ 491	$ 483