Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Pre- tax
Other comprehensive (loss) income	$ (67)	$ 82	$ (355)	$ 359
Tax
Other comprehensive (loss) income	14	(29)	75	(126)
After- tax
Other comprehensive (loss) income, after-tax	(53)	53	(280)	233
Accumulated Net Investment Gain (Loss)
Pre- tax
Unrealized net holding gains and losses arising during the period, net of related offsets	(64)	90	(379)	366
Less: reclassification adjustment of realized capital gains and losses	(8)	21	(24)	15
Other comprehensive (loss) income	(56)	69	(355)	351
Tax
Unrealized net holding gains and losses arising during the period, net of related offsets	14	(31)	80	(128)
Less: reclassification adjustment of realized capital gains and losses	2	(7)	5	(5)
Other comprehensive (loss) income	12	(24)	75	(123)
After- tax
Unrealized net holding gains and losses arising during the period, net of related offsets	(50)	59	(299)	238
Less: reclassification adjustment of realized capital gains and losses	(6)	14	(19)	10
Other comprehensive (loss) income, after-tax	(44)	45	(280)	228
Accumulated Foreign Currency Adjustment
Pre- tax
Other comprehensive (loss) income	(11)	13	0	8
Tax
Other comprehensive (loss) income	2	(5)	0	(3)
After- tax
Other comprehensive (loss) income, after-tax	$ (9)	$ 8	$ 0	$ 5

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