Investments and Cash - Internally Managed Investment Portfolio (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Schedule of Cost-method Investments [Line Items]
Fixed-maturity securities	$ 11,416	$ 11,258
Other invested assets	215	126
Internally managed portfolio	11,631	11,384
Fixed Maturities, Managed Internally [Member]
Schedule of Cost-method Investments [Line Items]
Fixed-maturity securities	746	835
Other Invested Assets, Internally Managed [Member]
Schedule of Cost-method Investments [Line Items]
Other invested assets	119	46
Other, Internally Managed [Member]
Schedule of Cost-method Investments [Line Items]
Other invested assets	97	79
Internally Managed Portfolio [Member]
Schedule of Cost-method Investments [Line Items]
Internally managed portfolio	$ 962	$ 960