Investments - Change in Unrealized Net Capital Gains and Losses (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Change in Unrealized Gain (Loss) Recognized in Accumulated Other Comprehensive Income (Loss)
Change in unrealized net capital gains and losses	$ (798)
Amount recognized for:
Insurance reserves	315
DAC and DSI	128
Amounts recognized	443
Deferred income taxes	75
Decrease in unrealized net capital gains and losses, after-tax	(280)
Cumulative effect of change in accounting principle		$ 308
Fixed income securities
Change in Unrealized Gain (Loss) Recognized in Accumulated Other Comprehensive Income (Loss)
Change in unrealized net capital gains and losses	(796)
Equity securities
Change in Unrealized Gain (Loss) Recognized in Accumulated Other Comprehensive Income (Loss)
Change in unrealized net capital gains and losses	0
Derivatives
Change in Unrealized Gain (Loss) Recognized in Accumulated Other Comprehensive Income (Loss)
Change in unrealized net capital gains and losses	$ (2)
Accounting Standards Update 2016-01
Amount recognized for:
Cumulative effect of change in accounting principle		$ 308