Investments - Fixed Maturities by Maturity Periods (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Amortized Cost:
Due in one year or less	$ 1,397
Due after one year through five years	6,251
Due after five years through ten years	6,905
Due after ten years	3,363
Mortgage and other asset-backed securities	540
Amortized Cost	18,456	$ 17,278
Fair Value:
Due in one year or less	1,403
Due after one year through five years	6,504
Due after five years through ten years	7,058
Due after ten years	3,917
Mortgage and other asset-backed securities	573
Total fair value	$ 19,455