Invested Assets - Components of Unrealized Appreciation or Depreciation of Investments (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Investments Debt And Equity Securities [Abstract]
Fixed maturities, Gross unrealized appreciation	$ 1,822	$ 1,457
Fixed maturities, Gross unrealized depreciation	73	325
Fixed maturities, Unrealized appreciation (depreciation), Net	1,749	1,132
Equity securities, Gross Unrealized Appreciation	878	756
Equity securities, Gross Unrealized Depreciation	15	3
Equity securities, Unrealized appreciation (depreciation), Net	863	753
Total fixed maturities and equity securities, Unrealized appreciation (depreciation), Net	2,612	1,885
Deferred income tax liability	914	660
Total fixed maturities and equity securities, Unrealized appreciation (depreciation), Net of tax	$ 1,698	$ 1,225