Investments and Cash - Distribution of Fixed-Maturity Securities by Contractual Maturity (Details) - USD ($) $ in Millions		Sep. 30, 2015	Dec. 31, 2014
Amortized Cost
Amortized cost		$ 10,242	$ 9,972
Estimated Fair Value
Estimated Fair Value		11,162	11,258
Fixed Maturities [Member]
Amortized Cost
Due within one year		260
Due after one year through five years		1,579
Due after five years through 10 years		2,241
Due after 10 years		4,321
Amortized cost		10,242
Estimated Fair Value
Due within one year		261
Due after one year through five years		1,637
Due after five years through 10 years		2,349
Due after 10 years		4,511
Estimated Fair Value		10,640	10,491
Fixed Maturities [Member] | RMBS [Member]
Amortized Cost
Amortized cost		1,349
Estimated Fair Value
Estimated Fair Value	[1]	1,371	1,285
Fixed Maturities [Member] | CMBS [Member]
Amortized Cost
Amortized cost		492
Estimated Fair Value
Estimated Fair Value	[1]	$ 511	$ 659

[1] Government-agency obligations were approximately 55% of mortgage backed securities as of September 30, 2015 and 44% as of December 31, 2014 based on fair value.