Condensed Consolidated Statements of Comprehensive Income (unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Statement of Comprehensive Income [Abstract]
Net (loss) income	$ (1,024)	$ 1,631	$ (378)	$ 244
Changes in:
Unrealized net capital gains and losses	(1,143)	484	(2,736)	(1,016)
Unrealized foreign currency translation adjustments	(47)	(3)	(47)	31
Unamortized pension and other postretirement prior service credit	(15)	(14)	(30)	(29)
Other comprehensive (loss) income, after-tax	(1,205)	467	(2,813)	(1,014)
Comprehensive (loss) income	(2,229)	2,098	(3,191)	(770)
Less: Comprehensive (loss) income attributable to noncontrolling interest	(17)	5	(39)	(1)
Comprehensive (loss) income attributable to Allstate	$ (2,212)	$ 2,093	$ (3,152)	$ (769)