Investments - Fixed Maturities by Maturity Periods (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Amortized Cost:
Due in one year or less	$ 1,126
Due after one year through five years	5,670
Due after five years through ten years	6,650
Due after ten years	3,327
Mortgage and other asset-backed securities	534
Amortized Cost	17,307	$ 17,278
Fair Value:
Due in one year or less	1,136
Due after one year through five years	6,015
Due after five years through ten years	6,904
Due after ten years	3,938
Mortgage and other asset-backed securities	576
Total fair value	$ 18,569