Investments - Fixed Maturities by Contractual Maturity Periods (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Amortized Cost:
Due in one year or less	$ 1,405
Due after one year through five years	6,717
Due after five years through ten years	8,481
Due after ten years	3,586
Mortgage and other asset-backed securities	450
Amortized Cost	20,639	$ 19,942
Fair Value:
Due in one year or less	1,416
Due after one year through five years	6,976
Due after five years through ten years	8,667
Due after ten years	4,196
Mortgage and other asset-backed securities	479
Total fair value	$ 21,734