Invested Assets - Fair Value and Amortized Cost of Fixed Maturities by Contractual Maturity (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Schedule of Available-For-Sale Securities [Line Items]
Due in one year or less, Fair Value	$ 2,192
Due after one year through five years, Fair Value	14,105
Due after five years through ten years, Fair Value	11,328
Due after ten years, Fair Value	7,841
Subtotal fixed maturities, Fair Value	35,466
Total fixed maturities, Fair Value	37,300	38,076
Due in one year or less, Amortized Cost	2,161
Due after one year through five years, Amortized Cost	13,532
Due after five years through ten years, Amortized Cost	10,699
Due after ten years, Amortized Cost	7,679
Subtotal fixed maturities, Amortized Cost	34,071
Total fixed maturities, Amortized Cost	35,837	35,398
Residential mortgage-backed securities [Member]
Schedule of Available-For-Sale Securities [Line Items]
Taxable, Fair Value	361
Taxable, Amortized Cost	336
Commercial mortgage-backed securities [Member]
Schedule of Available-For-Sale Securities [Line Items]
Taxable, Fair Value	1,473
Taxable, Amortized Cost	$ 1,430