Invested Assets and Related Income - Change in Unrealized Appreciation or Depreciation of Investments Carried at Fair Value (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Investments Debt And Equity Securities [Abstract]
Change in unrealized appreciation of fixed maturities	$ (1,546)	$ 256	$ 964
Change in unrealized appreciation of equity securities	334	171	(17)
Change in unrealized appreciation of fixed maturities and equity securities	(1,212)	427	947
Deferred income tax (credit)	(424)	150	331
Total change in unrealized appreciation (depreciation) of fixed maturities and equity securities, Net of tax	$ (788)	$ 277	$ 616