Invested Assets - Change in Unrealized Appreciation or Depreciation of Investments Carried at Fair Value (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Investments, Debt and Equity Securities [Abstract]
Change in unrealized appreciation of fixed maturities	$ 134	$ 2	$ (275)	$ 619
Change in unrealized appreciation of equity securities	(163)	(73)	(164)	37
Net unrealized gains (losses) recognized in other comprehensive income or loss, Before Tax	(29)	(71)	(439)	656
Deferred income tax (credit)	(10)	(25)	(154)	229
Net unrealized gains (losses) recognized in other comprehensive income or loss, Net of Tax	$ (19)	$ (46)	$ (285)	$ 427