Deferred Policy Acquisition Costs - Policy Acquisition Costs Deferred and Related Amortization Reflected in Operating Results (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Balance, beginning of year	$ 1,206	$ 1,210	$ 1,142
Costs deferred during year
Commissions and brokerage	1,979	1,919	1,910
Premium taxes and assessments	263	247	235
Underwriting and policy issuance costs	271	248	248
Total costs deferred during year	2,513	2,414	2,393
Foreign currency translation effect	(10)	(7)	5
Amortization during year	(2,454)	(2,411)	(2,330)
Balance, end of year	$ 1,255	$ 1,206	$ 1,210