Condensed Consolidated Statements of Comprehensive Income (Loss) (unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 1,164	$ (4)	$ 2,709	$ (1,700)
Changes in:
Unrealized net capital gains and losses	1,299	(667)	965	(257)
Unrealized foreign currency translation adjustments	14	(14)	(1)	64
Unamortized pension and other postretirement prior service credit	0	(5)	(1)	(14)
Discount rate for reserve for future policy benefits	(36)	30	(12)	29
Other comprehensive income (loss), after-tax	1,277	(656)	951	(178)
Comprehensive income (loss)	2,441	(660)	3,660	(1,878)
Less: Comprehensive loss attributable to noncontrolling interest	(19)	(1)	(22)	(21)
Comprehensive income (loss) attributable to Allstate	$ 2,460	$ (659)	$ 3,682	$ (1,857)