Investments - Fixed Maturities by Contractual Maturity Periods (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Amortized Cost:
Due in one year or less	$ 1,570
Due after one year through five years	6,481
Due after five years through ten years	8,036
Due after ten years	3,394
Mortgage and other asset-backed securities	461
Amortized Cost	19,942	$ 18,456
Fair Value:
Due in one year or less	1,574
Due after one year through five years	6,731
Due after five years through ten years	8,189
Due after ten years	3,981
Mortgage and other asset-backed securities	486
Total fair value	$ 20,961