Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Pre- tax
Other comprehensive income (loss)	$ 434	$ (217)
Tax
Other comprehensive income (loss)	(91)	46
After- tax
Other comprehensive income (loss), after-tax	343	(171)
Accumulated Net Investment Gain (Loss)
Pre- tax
Unrealized net holding gains and losses arising during the period, net of related offsets	430	(224)
Less: reclassification adjustment of realized capital gains and losses	(8)	(2)
Other comprehensive income (loss)	438	(222)
Tax
Unrealized net holding gains and losses arising during the period, net of related offsets	(90)	47
Less: reclassification adjustment of realized capital gains and losses	2	0
Other comprehensive income (loss)	(92)	47
After- tax
Unrealized net holding gains and losses arising during the period, net of related offsets	340	(177)
Less: reclassification adjustment of realized capital gains and losses	(6)	(2)
Other comprehensive income (loss), after-tax	346	(175)
Accumulated Foreign Currency Adjustment
Pre- tax
Other comprehensive income (loss)	(4)	5
Tax
Other comprehensive income (loss)	1	(1)
After- tax
Other comprehensive income (loss), after-tax	$ (3)	$ 4