Contingencies, Commitments and Guarantees (Contingencies - Narrative) (Details)	12 Months Ended
	Dec. 31, 2017 USD ($) Claims
Loss Contingencies
Reserves for Group Annuity products	$ 510,000,000
Assumed variable annuity guarantee reserves	896,000,000
Minimum
Loss Contingencies
Loss Contingency, Range of Possible Loss, Portion Not Accrued	0
Maximum
Loss Contingencies
Loss Contingency, Range of Possible Loss, Portion Not Accrued	$ 425,000,000
Superfund Site Settlement Agreements
Loss Contingencies
Number of regulatory matters and other claims | Claims	2
Superfund Site Settlement Agreements | Maximum
Loss Contingencies
Maximum estimate of aggregate costs to resolve matter	$ 300,000