Invested Assets - Fair Value and Amortized Cost of Fixed Maturities by Contractual Maturity (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Schedule of Available-For-Sale Securities [Line Items]
Due in one year or less, Fair Value	$ 2,460
Due after one year through five years, Fair Value	12,329
Due after five years through ten years, Fair Value	13,321
Due after ten years, Fair Value	9,139
Subtotal fixed maturities, Fair Value	37,249
Total fixed maturities, Fair Value	38,457	38,780
Due in one year or less, Amortized Cost	2,438
Due after one year through five years, Amortized Cost	11,794
Due after five years through ten years, Amortized Cost	12,449
Due after ten years, Amortized Cost	8,639
Subtotal fixed maturities, Amortized Cost	35,320
Fixed maturities, Amortized Cost	36,483	36,958
Residential Mortgage-backed Securities [Member]
Schedule of Available-For-Sale Securities [Line Items]
Taxable, Fair Value	194
Taxable, Amortized Cost	175
Commercial Mortgage-backed Securities [Member]
Schedule of Available-For-Sale Securities [Line Items]
Taxable, Fair Value	1,014
Taxable, Amortized Cost	$ 988