Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 1,566	$ 5,576	$ 4,847
Changes in:
Unrealized net capital gains and losses	(2,582)	1,293	1,889
Unrealized foreign currency translation adjustments	(8)	52	(10)
Unamortized pension and other postretirement prior service credit	(59)	9	(47)
Other comprehensive (loss) income, after-tax	(2,649)	1,354	1,832
Comprehensive (loss) income	(1,083)	6,930	6,679
Less: Comprehensive loss attributable to noncontrolling interest	(36)	0	0
Comprehensive (loss) income attributable to Allstate	$ (1,047)	$ 6,930	$ 6,679