Investments - Fixed Maturities by Maturity Periods (Details) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Amortized Cost:
Due in one year or less	$ 1,473
Due after one year through five years	6,449
Due after five years through ten years	6,996
Due after ten years	3,331
Mortgage and other asset-backed securities	496
Amortized Cost	18,745	$ 18,456
Fair Value:
Due in one year or less	1,480
Due after one year through five years	6,813
Due after five years through ten years	7,477
Due after ten years	4,239
Mortgage and other asset-backed securities	529
Total fair value	$ 20,538