Condensed Consolidated Statements of Comprehensive Income (Loss) (unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Statement of Comprehensive Income [Abstract]
Net (loss) income	$ (683)	$ 531	$ (1,061)	$ 775
Changes in:
Unrealized net capital gains and losses	(789)	(336)	(3,525)	(1,352)
Unrealized foreign currency translation adjustments	(88)	(21)	(135)	10
Unamortized pension and other postretirement prior service credit	(8)	(15)	(38)	(44)
Other comprehensive loss, after-tax	(885)	(372)	(3,698)	(1,386)
Comprehensive (loss) income	(1,568)	159	(4,759)	(611)
Less: Comprehensive loss attributable to noncontrolling interest	(21)	(7)	(60)	(8)
Comprehensive (loss) income attributable to Allstate	$ (1,547)	$ 166	$ (4,699)	$ (603)