Investments (Maturities of Fixed Maturity Securities) (Details) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Available-for-sale Securities, Debt Maturities [Abstract]
Amortized Cost, Due in one year or less	$ 13,404
Amortized Cost, Due after one year through five years	80,755
Amortized Cost, Due after five years through ten years	69,842
Amortized Cost, Due after ten years	114,317
Amortized Cost, RMBS, CMBS and ABS	72,503
Amortized Cost, Subtotal	350,821	$ 332,964
Estimated Fair Value, Due in one year or less	13,499
Estimated Fair Value, Due after one year through five years	85,064
Estimated Fair Value, Due after five years through ten years	74,476
Estimated Fair Value, Due after ten years	140,196
Estimated fair value, Mortgage-backed and asset-backed securities	74,273
Available-for-sale Securities, Debt Securities	$ 387,508	$ 351,402