Investments - Fixed Maturities by Maturity Periods (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Amortized Cost:
Due in one year or less	$ 1,533
Due after one year through five years	6,359
Due after five years through ten years	6,888
Due after ten years	3,352
Mortgage and other asset-backed securities	552
Amortized Cost	18,684	$ 18,456
Fair Value:
Due in one year or less	1,541
Due after one year through five years	6,652
Due after five years through ten years	7,216
Due after ten years	4,085
Mortgage and other asset-backed securities	593
Total fair value	$ 20,087