Claim and Claim Adjustment Expense Reserves - Impact of Loss Portfolio Transfer on Consolidated Statements of Income (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Insurance [Abstract]
Net A&EP adverse development before consideration of LPT		$ 363	$ 261
Provision for uncollectible third party reinsurance on A&EP		140
Additional amounts ceded under LPT		503	261
Retroactive reinsurance benefit recognized	(13)	(314)	(261)
Pretax impact of unrecognized deferred retroactive reinsurance benefit	$ (13)	$ 189