Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 512	$ 689	$ 940	$ 566	$ 355	$ 644	$ 193	$ 491	$ 2,707	$ 1,683	$ 2,448
Other comprehensive income (loss):
Change in gross unrealized investment losses/gains									450	(189)	149
Effect of income taxes									(105)	51	(55)
Total change in unrealized investment gains/losses, net of tax									345	(138)	94
Reclassification adjustment for net realized gains included in investment income									(34)	(53)	(14)
Effect of income taxes									8	17	5
Total reclassification adjustment, net of tax									(26)	(36)	(9)
Other comprehensive income (loss), net of tax									319	(174)	85
Comprehensive income attributable to our equity method investment in Kindred at Home									(4)	(4)	0
Comprehensive income									$ 3,022	$ 1,505	$ 2,533