Invested Assets - Components of Unrealized Appreciation or Depreciation of Investments (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Investments Debt And Equity Securities [Abstract]
Fixed maturities, Gross unrealized appreciation	$ 1,650	$ 1,457
Fixed maturities, Gross unrealized depreciation	156	325
Fixed maturities, Unrealized appreciation (depreciation), Net	1,494	1,132
Equity securities, Gross Unrealized Appreciation	766	756
Equity securities, Gross Unrealized Depreciation	14	3
Equity securities, Unrealized appreciation (depreciation), Net	752	753
Total fixed maturities and equity securities, Unrealized appreciation (depreciation), Net	2,246	1,885
Deferred income tax liability	786	660
Total fixed maturities and equity securities, Unrealized appreciation (depreciation), Net of tax	$ 1,460	$ 1,225