Investments and Cash - Internally Managed Investment Portfolio (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Schedule of Cost-method Investments [Line Items]
Fixed-maturity securities	$ 11,023	$ 11,258
Other invested assets	169	126
Internally managed portfolio	11,192	11,384
Fixed Maturities, Managed Internally [Member]
Schedule of Cost-method Investments [Line Items]
Fixed-maturity securities	1,266	835
Other Invested Assets, Internally Managed [Member]
Schedule of Cost-method Investments [Line Items]
Other invested assets	114	46
Other, Internally Managed [Member]
Schedule of Cost-method Investments [Line Items]
Other invested assets	55	79
Internally Managed Portfolio [Member]
Schedule of Cost-method Investments [Line Items]
Internally managed portfolio	$ 1,435	$ 960