Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statement of Comprehensive Income [Abstract]
Net (loss) income	$ (213)	$ (1,342)	$ 1,581
Changes in:
Unrealized net capital gains and losses	1,651	(2,853)	(2,583)
Unrealized foreign currency translation adjustments	67	(150)	(8)
Unamortized pension and other postretirement prior service credit	(16)	(43)	(59)
Discount rate for reserve for future policy benefits	(10)	228	49
Other comprehensive income (loss), after-tax	1,692	(2,818)	(2,601)
Comprehensive income (loss)	1,479	(4,160)	(1,020)
Less: Comprehensive loss attributable to noncontrolling interest	(15)	(73)	(36)
Comprehensive income (loss) attributable to Allstate	$ 1,494	$ (4,087)	$ (984)