Consolidated Statements of Comprehensive Income (unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 317	$ 59
Unrealized holding gains (losses) arising during the period on:
Investments with no other-than-temporary impairment, net of tax provision (benefit) of $23 and $31	44	95
Investments with other-than-temporary impairment, net of tax provision (benefit) of $28 and $(10)	50	(17)
Unrealized holding gains (losses) arising during the period, net of tax	94	78
Less: reclassification adjustment for gains (losses) included in net income (loss), net of tax provision (benefit) of $21 and $(4)	39	(6)
Change in net unrealized gains (losses) on investments	55	84
Other, net of tax provision	2	(2)
Other comprehensive income (loss)	57	82
Comprehensive income (loss)	$ 374	$ 141