Investments - Fixed Maturities by Maturity Periods (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014
Amortized Cost:
Due in one year or less	$ 1,152
Due after one year through five years	5,681
Due after five years through ten years	6,531
Due after ten years	3,267
Mortgage and other asset-backed securities	647
Total amortized cost	17,278
Fair Value:
Due in one year or less	1,166
Due after one year through five years	6,051
Due after five years through ten years	6,891
Due after ten years	4,140
Mortgage and other asset-backed securities	735
Total fair value	$ 18,983