Condensed Consolidated Statements of Comprehensive Income (Loss) (unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Statement of Comprehensive Income [Abstract]
Net loss	$ (1,375)	$ (1,022)	$ (1,696)	$ (372)
Changes in:
Unrealized net capital gains and losses	(272)	(1,144)	410	(2,738)
Unrealized foreign currency translation adjustments	28	(47)	78	(47)
Unamortized pension and other postretirement prior service credit	(5)	(15)	(9)	(30)
Discount rate for reserve for future policy benefits	8	85	(1)	180
Other comprehensive (loss) income, after-tax	(241)	(1,121)	478	(2,635)
Comprehensive loss	(1,616)	(2,143)	(1,218)	(3,007)
Less: Comprehensive loss attributable to noncontrolling interest	(24)	(17)	(20)	(39)
Comprehensive loss attributable to Allstate	$ (1,592)	$ (2,126)	$ (1,198)	$ (2,968)