Investments - Fixed Maturities by Contractual Maturity Periods (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Amortized Cost:
Due in one year or less	$ 1,365
Due after one year through five years	6,894
Due after five years through ten years	9,260
Due after ten years	3,705
Mortgage and other asset-backed securities	446
Amortized Cost	21,670	$ 19,942
Fair Value:
Due in one year or less	1,377
Due after one year through five years	7,135
Due after five years through ten years	9,528
Due after ten years	4,425
Mortgage and other asset-backed securities	479
Total fair value	$ 22,944