Condensed Consolidated Statements of Comprehensive Income (Loss) (unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Statement of Comprehensive Income [Abstract]
Net income	$ 2,458	$ 596
Changes in:
Unrealized net capital gains and losses	(518)	420
Unrealized foreign currency translation adjustments	(28)	(45)
Unamortized pension and other postretirement prior service credit	(1)	0
Discount rate for reserve for future policy benefits	0	5
Other comprehensive (loss) income, after-tax	(547)	380
Comprehensive income	1,911	976
Less: Comprehensive income attributable to noncontrolling interest	1	5
Comprehensive income attributable to Allstate	$ 1,910	$ 971