Derivatives (Embedded Derivatives) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Embedded Derivative, Fair Value of Embedded Derivative, Net [Abstract]
Embedded derivatives within asset host contracts	$ 157	$ 12
Embedded derivatives within liability host contracts	485	418
Ceded guaranteed minimum benefits | Premiums, reinsurance and other receivables
Embedded Derivative, Fair Value of Embedded Derivative, Net [Abstract]
Embedded derivatives within asset host contracts	157	144
Direct guaranteed minimum benefits | Policyholder account balances
Embedded Derivative, Fair Value of Embedded Derivative, Net [Abstract]
Embedded derivatives within liability host contracts	23	32
Assumed guaranteed minimum benefits | Policyholder account balances
Embedded Derivative, Fair Value of Embedded Derivative, Net [Abstract]
Embedded derivatives within liability host contracts	392	291
Funds withheld on ceded reinsurance | Other liabilities
Embedded Derivative, Fair Value of Embedded Derivative, Net [Abstract]
Embedded derivatives within liability host contracts	2	25
Fixed annuities with equity indexed returns | Policyholder account balances
Embedded Derivative, Fair Value of Embedded Derivative, Net [Abstract]
Embedded derivatives within liability host contracts	68	70
Options embedded in debt or equity securities [Member] | Other
Embedded Derivative, Fair Value of Embedded Derivative, Net [Abstract]
Embedded derivatives within asset host contracts	$ 0	$ (132)