Condensed Consolidated Statements of Comprehensive Income (Loss) (unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Statement of Comprehensive Income [Abstract]
Net (loss) income	$ (321)	$ 650
Changes in:
Unrealized net capital gains and losses	682	(1,594)
Unrealized foreign currency translation adjustments	50	0
Unamortized pension and other postretirement prior service credit	(4)	(15)
Change in discount rate for reserve for future policy benefits	(9)	95
Other comprehensive income (loss), after-tax	719	(1,514)
Comprehensive income (loss)	398	(864)
Less: Comprehensive income (loss) attributable to noncontrolling interest	4	(22)
Comprehensive income (loss) attributable to Allstate	$ 394	$ (842)