Derivatives (Embedded Derivatives) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Embedded Derivative, Fair Value of Embedded Derivative, Net [Abstract]
Embedded Derivative, Fair Value of Embedded Derivative Asset	$ 175	$ 360
Embedded Derivative, Fair Value of Embedded Derivative Liability	2,234	3,170
Ceded guaranteed minimum benefits | Premiums, reinsurance and other receivables
Embedded Derivative, Fair Value of Embedded Derivative, Net [Abstract]
Embedded Derivative, Fair Value of Embedded Derivative Asset	227	409
Direct guaranteed minimum benefits | Policyholder account balances
Embedded Derivative, Fair Value of Embedded Derivative, Net [Abstract]
Embedded Derivative, Fair Value of Embedded Derivative Liability	1,122	2,237
Deferred Fixed Annuity [Member] | Policyholder account balances
Embedded Derivative, Fair Value of Embedded Derivative, Net [Abstract]
Embedded Derivative, Fair Value of Embedded Derivative Liability	1	0
Assumed guaranteed minimum benefits | Policyholder account balances
Embedded Derivative, Fair Value of Embedded Derivative, Net [Abstract]
Embedded Derivative, Fair Value of Embedded Derivative Liability	437	741
Other Embedded Derivatives [Member] | Policyholder account balances
Embedded Derivative, Fair Value of Embedded Derivative, Net [Abstract]
Embedded Derivative, Fair Value of Embedded Derivative Liability	674	192
Options embedded in debt or equity securities [Member] | Other Investments [Member]
Embedded Derivative, Fair Value of Embedded Derivative, Net [Abstract]
Embedded Derivative, Fair Value of Embedded Derivative Asset	$ (52)	$ (49)