Consolidated Statements of Comprehensive Income (unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement of Comprehensive Income [Abstract]
Investments with no other-than-temporary impairment, tax provision (benefit)	$ 30	$ 31	$ 53	$ 62
Investments with other-than-temporary impairment, tax provision (benefit)	23	(3)	51	(13)
Reclassification adjustment for gains (losses) included in net income (loss), tax provision (benefit)	$ 5	$ 4	$ 26	$ 0