Derivatives (Embedded Derivatives) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Embedded Derivative, Fair Value of Embedded Derivative, Net [Abstract]
Embedded derivatives within asset host contracts	$ 12	$ 55
Embedded derivatives within liability host contracts	418	872
Ceded guaranteed minimum benefits | Premiums, reinsurance and other receivables
Embedded Derivative, Fair Value of Embedded Derivative, Net [Abstract]
Embedded derivatives within asset host contracts	144	143
Direct guaranteed minimum benefits | Policyholder account balances [Member]
Embedded Derivative, Fair Value of Embedded Derivative, Net [Abstract]
Embedded derivatives within liability host contracts	32	361
Assumed guaranteed minimum benefits | Policyholder account balances [Member]
Embedded Derivative, Fair Value of Embedded Derivative, Net [Abstract]
Embedded derivatives within liability host contracts	291	523
Funds withheld on ceded reinsurance | Other liabilities
Embedded Derivative, Fair Value of Embedded Derivative, Net [Abstract]
Embedded derivatives within liability host contracts	25	(30)
Fixed annuities with equity indexed returns | Policyholder account balances [Member]
Embedded Derivative, Fair Value of Embedded Derivative, Net [Abstract]
Embedded derivatives within liability host contracts	70	18
Options embedded in debt or equity securities [Member] | Investments
Embedded Derivative, Fair Value of Embedded Derivative, Net [Abstract]
Embedded derivatives within asset host contracts	$ (132)	$ (88)