Business Dispositions and Discontinued Operations - Reconciliation of the Major Line Items Constituting Pretax Profit (Loss) of Discontinued Operations (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Benefits, losses and expenses
(Loss) income from discontinued operations, net of tax	$ 169	$ 75
Run-Off Life and Annuity Business | Discontinued Operations, Held-for-sale
Revenues
Earned premiums	27	36
Fee income and other	232	223
Net investment income	312	318
Net realized capital losses	21	(45)
Total revenues	592	532
Benefits, losses and expenses
Benefits, losses and loss adjustment expenses	328	333
Amortization of DAC	41	19
Insurance operating costs and other expenses	101	94
Total benefits, losses and expenses	470	446
Income before income taxes	122	86
Income tax expense	15	11
Income from operations of discontinued operations, net of tax	107	75
Discontinued Operation, Amount of Adjustment to Prior Period Gain (Loss) on Disposal, Net of Tax	62	0
(Loss) income from discontinued operations, net of tax	$ 169	$ 75