Invested Assets and Related Income - Fair Value and Amortized Cost of Fixed Maturities by Contractual Maturity (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Schedule of Available-For-Sale Securities [Line Items]
Due in one year or less, Fair Value	$ 2,947
Due after one year through five years, Fair Value	12,906
Due after five years through ten years, Fair Value	12,814
Due after ten years, Fair Value	8,812
Subtotal fixed maturities, Fair Value	37,479
Total fixed maturities, Fair Value	38,780	37,091
Due in one year or less, Amortized Cost	2,922
Due after one year through five years, Amortized Cost	12,406
Due after five years through ten years, Amortized Cost	12,041
Due after ten years, Amortized Cost	8,328
Subtotal fixed maturities, Amortized Cost	35,697
Fixed maturities, Amortized Cost	36,958	35,959
Residential Mortgage-backed Securities [Member]
Schedule of Available-For-Sale Securities [Line Items]
Taxable, Fair Value	211
Taxable, Amortized Cost	192
Commercial Mortgage-backed Securities [Member]
Schedule of Available-For-Sale Securities [Line Items]
Taxable, Fair Value	1,090
Taxable, Amortized Cost	$ 1,069