Business Dispositions and Discontinued Operations - Reconciliation of the Major Line Items Constituting Pretax Profit (Loss) of Discontinued Operations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Benefits, losses and expenses
Net realized capital loss on disposal, net of tax	$ (3,257)	$ (81)	$ 6
(Loss) income from discontinued operations, net of tax	(2,869)	283	493
Run-Off Life and Annuity Business | Discontinued Operations, Held-for-sale
Revenues
Earned premiums	106	114	92
Fee income and other	912	931	1,040
Net investment income	1,289	1,384	1,469
Net realized capital losses	(53)	(158)	(144)
Total revenues	2,254	2,271	2,457
Benefits, losses and expenses
Benefits, losses and loss adjustment expenses	1,416	1,390	1,450
Amortization of DAC	45	146	138
Insurance operating costs and other expenses	368	378	367
Total benefits, losses and expenses	1,829	1,914	1,955
Income before income taxes	425	357	502
Income tax expense	37	74	16
Income from operations of discontinued operations, net of tax	388	283	486
Net realized capital loss on disposal, net of tax	(3,257)	0	0
(Loss) income from discontinued operations, net of tax	$ (2,869)	$ 283	$ 486