Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Pre- tax
Other comprehensive (loss) income	$ (71)	$ 181	$ (288)	$ 277
Tax
Other comprehensive (loss) income	15	(63)	61	(97)
After- tax
Other comprehensive (loss) income, after-tax	(56)	118	(227)	180
Accumulated Net Investment Gain (Loss)
Pre- tax
Unrealized net holding gains and losses arising during the period, net of related offsets	(94)	178	(320)	281
Less: reclassification adjustment of realized capital gains and losses	(17)	(3)	(21)	(1)
Other comprehensive (loss) income	(77)	181	(299)	282
Tax
Unrealized net holding gains and losses arising during the period, net of related offsets	20	(62)	67	(99)
Less: reclassification adjustment of realized capital gains and losses	4	1	4	0
Other comprehensive (loss) income	16	(63)	63	(99)
After- tax
Unrealized net holding gains and losses arising during the period, net of related offsets	(74)	116	(253)	182
Less: reclassification adjustment of realized capital gains and losses	(13)	(2)	(17)	(1)
Other comprehensive (loss) income, after-tax	(61)	118	(236)	183
Accumulated Foreign Currency Adjustment
Pre- tax
Other comprehensive (loss) income	6	0	11	(5)
Tax
Other comprehensive (loss) income	(1)	0	(2)	2
After- tax
Other comprehensive (loss) income, after-tax	$ 5	$ 0	$ 9	$ (3)

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