Investments - Available-for-Sale Fixed Maturity Securities by Contractual Maturity (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Investments, Debt and Equity Securities [Abstract]
Cost or Amortized Cost, Due in one year or less	$ 2,329	$ 2,420
Cost or Amortized Cost, Due after one year through five years	8,888	9,496
Cost or Amortized Cost, Due after five years through ten years	12,446	11,667
Cost or Amortized Cost, Due after ten years	13,827	15,692
Cost or Amortized Cost, Total	37,490	39,275
Estimated Fair Value, Due in one year or less	2,368	2,455
Estimated Fair Value, Due after one year through five years	9,455	10,068
Estimated Fair Value, Due after five years through ten years	12,951	11,954
Estimated Fair Value, Due after ten years	15,906	16,720
Estimated Fair Value, Total	$ 40,680	$ 41,197