Investments (Maturities of Fixed Maturity Securities) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Available-for-sale Securities, Debt Maturities [Abstract]
Amortized Cost, Due in one year or less	$ 15,423
Amortized Cost, Due after one year through five years	68,766
Amortized Cost, Due after five years through ten years	67,522
Amortized Cost, Due after ten years	117,338
Amortized Cost, Subtotal	330,354	$ 332,964
Amortized Cost, RMBS, CMBS and ABS	61,305
Estimated Fair Value, Due in one year or less	15,517
Estimated Fair Value, Due after one year through five years	72,018
Estimated Fair Value, Due after five years through ten years	70,282
Estimated Fair Value, Due after ten years	130,930
Estimated fair value, Mortgage-backed and asset-backed securities	62,142
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $330,354 and $332,964, respectively; includes $3,422 and $4,277, respectively, relating to variable interest entities)	$ 350,889	$ 351,402