Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Pre- tax
Unrealized net holding gains and losses arising during the period, net of related offsets	$ 105	$ 329
Less: reclassification adjustment of realized capital gains and losses	4	(41)
Unrealized net capital gains and losses	101	370
Unrealized foreign currency translation adjustments	(5)	(3)
Other comprehensive income	96	367
Tax
Unrealized net holding gains and losses arising during the period, net of related offsets	(37)	(115)
Less: reclassification adjustment of realized capital gains and losses	(1)	14
Unrealized net capital gains and losses	(36)	(129)
Unrealized foreign currency translation adjustments	2	1
Other comprehensive income (loss)	(34)	(128)
After- tax
Unrealized net holding gains and losses arising during the period, net of related offsets	68	214
Less: reclassification adjustment of realized capital gains and losses	3	(27)
Unrealized net capital gains and losses	65	241
Unrealized foreign currency translation adjustments	(3)	(2)
Other comprehensive income, after-tax	$ 62	$ 239