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	$ 200	$ 175
Embedded derivatives within liability host contracts	1,787	2,234
Ceded guaranteed minimum benefits | Premiums, reinsurance and other receivables
Embedded Derivative, Fair Value of Embedded Derivative, Net [Abstract]
Embedded derivatives within asset host contracts	200	227
Direct guaranteed minimum benefits | Policyholder account balances
Embedded Derivative, Fair Value of Embedded Derivative, Net [Abstract]
Embedded derivatives within liability host contracts	802	1,122
Deferred Fixed Annuity [Member] | Policyholder account balances
Embedded Derivative, Fair Value of Embedded Derivative, Net [Abstract]
Embedded derivatives within liability host contracts	(1)	1
Assumed reinsurance on fixed deferred annuities | Policyholder account balances
Embedded Derivative, Fair Value of Embedded Derivative, Net [Abstract]
Embedded derivatives within liability host contracts	370	437
Fixed annuities with equity indexed returns | Policyholder account balances
Embedded Derivative, Fair Value of Embedded Derivative, Net [Abstract]
Embedded derivatives within liability host contracts	616	674
Options embedded in debt or equity securities (1) | Investments
Embedded Derivative, Fair Value of Embedded Derivative, Net [Abstract]
Embedded derivatives within asset host contracts	$ 0	$ (52)