Investments - Fixed Maturities by Maturity Periods (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014
Amortized Cost:
Due in one year or less	$ 1,093
Due after one year through five years	5,439
Due after five years through ten years	5,909
Due after ten years	2,794
Mortgage and other asset-backed securities	921
Total amortized cost	16,156
Fair Value:
Due in one year or less	1,112
Due after one year through five years	5,829
Due after five years through ten years	6,253
Due after ten years	3,427
Mortgage and other asset-backed securities	1,029
Total fair value	$ 17,650