Invested Assets - Change in Unrealized Appreciation or Depreciation of Investments Carried at Fair Value (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Investments, Debt and Equity Securities [Abstract]
Change in unrealized appreciation of fixed maturities	$ 2	$ (99)	$ 619	$ (1,314)
Change in unrealized appreciation of equity securities	(73)	94	37	239
Change in unrealized appreciation of fixed maturities and equity securities	(71)	(5)	656	(1,075)
Deferred income tax (credit)	(25)	(2)	229	(376)
Total change in unrealized appreciation (depreciation) of fixed maturities and equity securities, Net of tax	$ (46)	$ (3)	$ 427	$ (699)