Investments - Fixed Maturities by Maturity Periods (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Amortized Cost:
Due in one year or less	$ 1,065
Due after one year through five years	5,736
Due after five years through ten years	6,537
Due after ten years	3,299
Mortgage and other asset-backed securities	615
Amortized Cost	17,252	17,278
Fair Value:
Due in one year or less	1,081
Due after one year through five years	6,123
Due after five years through ten years	6,981
Due after ten years	4,247
Mortgage and other asset-backed securities	709
Total fair value	$ 19,141