Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 3,367	$ 2,707	$ 1,683
Other comprehensive income (loss):
Change in gross unrealized investment gains/losses	393	450	(189)
Effect of income taxes	(89)	(105)	51
Total change in unrealized investment gains/losses, net of tax	304	345	(138)
Reclassification adjustment for net realized gains included in investment income	(90)	(34)	(53)
Effect of income taxes	20	8	17
Total reclassification adjustment, net of tax	(70)	(26)	(36)
Other comprehensive income (loss), net of tax	234	319	(174)
Comprehensive income (loss) attributable to equity method investments	1	(4)	(4)
Comprehensive income	$ 3,602	$ 3,022	$ 1,505