Invested Assets - Fair Value and Amortized Cost of Fixed Maturities by Contractual Maturity (Detail) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Schedule of Available-For-Sale Securities [Line Items]
Due in one year or less, Fair Value	$ 2,239
Due after one year through five years, Fair Value	12,211
Due after five years through ten years, Fair Value	13,567
Due after ten years, Fair Value	8,700
Subtotal fixed maturities, Fair Value	36,717
Total fixed maturities, Fair Value	37,880	$ 38,780
Due in one year or less, Amortized Cost	2,220
Due after one year through five years, Amortized Cost	11,745
Due after five years through ten years, Amortized Cost	12,939
Due after ten years, Amortized Cost	8,434
Subtotal fixed maturities, Amortized Cost	35,338
Fixed maturities, Amortized Cost	36,467	$ 36,958
Residential Mortgage-backed Securities [Member]
Schedule of Available-For-Sale Securities [Line Items]
Taxable, Fair Value	174
Taxable, Amortized Cost	158
Commercial Mortgage-backed Securities [Member]
Schedule of Available-For-Sale Securities [Line Items]
Taxable, Fair Value	989
Taxable, Amortized Cost	$ 971