Consolidated Statements of Comprehensive Income (unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 479	$ 129	$ 684	$ 627
Unrealized holding gains (losses) arising during the period on:
Investments with no other-than-temporary impairment, net of tax provision (benefit) of $(14), $17, $48 and $(36)	(33)	41	146	(77)
Investments with other-than-temporary impairment, net of tax provision (benefit) of $8, $(9), $(5) and $(12)	13	(15)	(10)	(23)
Unrealized holding gains (losses) arising during the period, net of tax	(20)	26	136	(100)
Less: reclassification adjustment for gains (losses) included in net income (loss), net of tax provision (benefit) of $(1), $(6), $(1) and $(4)	0	(12)	(1)	(7)
Change in net unrealized gains on investments	(20)	38	137	(93)
Other, net of tax provision	(5)	(4)	(16)	(4)
Other comprehensive income (loss)	(25)	34	121	(97)
Comprehensive income (loss)	$ 454	$ 163	$ 805	$ 530