Condensed Consolidated Statements Of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 499	$ 450	$ 2,264	$ 1,015
Other comprehensive income:
Change in gross unrealized investment gains/losses	26	(9)	152	150
Effect of income taxes	(9)	3	(56)	(55)
Total change in unrealized investment gains/losses, net of tax	17	(6)	96	95
Reclassification adjustment for net realized gains included in investment income	0	(26)	(28)	(65)
Effect of income taxes	0	10	10	24
Total reclassification adjustment, net of tax	0	(16)	(18)	(41)
Other comprehensive income (loss), net of tax	17	(22)	78	54
Comprehensive income	$ 516	$ 428	$ 2,342	$ 1,069