Investments - Change in unrealized net capital gains and losses (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Change in Unrealized Gain (Loss) Recognized in Accumulated Other Comprehensive Income (Loss)
Change in unrealized net capital gains and losses	$ 373	$ 312	$ (1,455)
Amounts recognized for:
Insurance reserves	(315)	0	28
DAC and DSI	(49)	(78)	114
Amounts recognized	(364)	(78)	142
Deferred income taxes	145	(81)	459
Increase (decrease) in unrealized net capital gains and losses, after-tax	154	153	(854)
EMA limited partnerships
Change in Unrealized Gain (Loss) Recognized in Accumulated Other Comprehensive Income (Loss)
Change in unrealized net capital gains and losses	3	0	0
Fixed income securities
Change in Unrealized Gain (Loss) Recognized in Accumulated Other Comprehensive Income (Loss)
Change in unrealized net capital gains and losses	147	251	(1,436)
Equity securities
Change in Unrealized Gain (Loss) Recognized in Accumulated Other Comprehensive Income (Loss)
Change in unrealized net capital gains and losses	226	66	(27)
Derivative instruments
Change in Unrealized Gain (Loss) Recognized in Accumulated Other Comprehensive Income (Loss)
Change in unrealized net capital gains and losses	$ (3)	$ (5)	$ 8