Condensed Consolidated Statements of Comprehensive Income (Loss) (unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Statement of Comprehensive Income [Abstract]
Net income	$ 596	$ 1,198
Changes in:
Unrealized net capital gains and losses	420	(215)
Unrealized foreign currency translation adjustments	(45)	8
Unamortized pension and other postretirement prior service credit	0	(1)
Discount rate for reserve for future policy benefits	5	25
Other comprehensive income (loss), after-tax	380	(183)
Comprehensive income	976	1,015
Less: Comprehensive income (loss) attributable to noncontrolling interest	5	(19)
Comprehensive income attributable to Allstate	$ 971	$ 1,034