Investments and Cash - Distribution of Fixed-Maturity Securities by Contractual Maturity (Details) - USD ($) $ in Millions		Mar. 31, 2016	Dec. 31, 2015
Amortized Cost
Amortized cost		$ 10,123	$ 10,275
Estimated Fair Value
Estimated Fair Value		11,047	11,023
Fixed Maturities [Member]
Amortized Cost
Due within one year		469
Due after one year through five years		1,654
Due after five years through 10 years		2,195
Due after 10 years		4,052
Amortized cost		10,123
Estimated Fair Value
Due within one year		470
Due after one year through five years		1,719
Due after five years through 10 years		2,320
Due after 10 years		4,284
Estimated Fair Value		10,588	10,627
Fixed Maturities [Member] | RMBS [Member]
Amortized Cost
Amortized cost		1,222
Estimated Fair Value
Estimated Fair Value	[1]	1,239	1,245
Fixed Maturities [Member] | CMBS [Member]
Amortized Cost
Amortized cost		531
Estimated Fair Value
Estimated Fair Value	[1]	$ 556	$ 513

[1] Government-agency obligations were approximately 52% of mortgage backed securities as of March 31, 2016 and 54% as of December 31, 2015 based on fair value.