Condensed Consolidated Statements of Shareholders’ Equity (unaudited) - USD ($) $ in Millions	Total	Preferred stock par value	Preferred stock additional capital paid-in	Common stock par value	Common stock additional capital paid-in	Retained income	Treasury stock	Accumulated other comprehensive income (loss)	Noncontrolling interest
Balance, beginning of period at Dec. 31, 2023					$ 3,854	$ 49,716	$ (37,110)	$ (700)	$ (140)
Increase (decrease) in equity
Equity incentive plans activity, net					133
Net income (loss)	$ 2,709					2,739			(30)
Dividends on common stock (declared per share of $1.00, $0.92, $3.00, and $2.76)						(732)
Dividends on preferred stock						(88)
Shares reissued under equity incentive plans, net							104
Change in unrealized net capital gains and losses	965							965	8
Change in unrealized foreign currency translation adjustments	(1)							(1)
Change in unamortized pension and other postretirement prior service credit	(1)							(1)
Change in discount rate for reserve for future policy benefits	(12)							(12)
Capital transactions for noncontrolling interest									123
Balance, end of period at Sep. 30, 2024	20,838	$ 0	$ 2,001	$ 9	3,987	51,635	(37,006)	251	(39)
Balance, beginning of period at Jun. 30, 2024					3,927	50,718	(37,036)	(1,026)	(20)
Increase (decrease) in equity
Equity incentive plans activity, net					60
Net income (loss)	1,164					1,190			(26)
Dividends on common stock (declared per share of $1.00, $0.92, $3.00, and $2.76)						(244)
Dividends on preferred stock						(29)
Shares reissued under equity incentive plans, net							30
Change in unrealized net capital gains and losses	1,299							1,299	7
Change in unrealized foreign currency translation adjustments	14							14
Change in unamortized pension and other postretirement prior service credit	0
Change in discount rate for reserve for future policy benefits	(36)							(36)
Balance, end of period at Sep. 30, 2024	20,838	0	2,001	9	3,987	51,635	(37,006)	251	(39)
Increase (decrease) in equity
Total Allstate shareholders’ equity	20,877
Total Allstate shareholders’ equity	21,442
Balance, beginning of period at Dec. 31, 2024	21,367				4,029	53,288	(36,996)	(889)	(75)
Increase (decrease) in equity
Equity incentive plans activity, net					88
Net income (loss)	6,439					6,450			(11)
Dividends on common stock (declared per share of $1.00, $0.92, $3.00, and $2.76)						(797)
Dividends on preferred stock						(88)
Shares acquired							(812)
Shares reissued under equity incentive plans, net							35
Change in unrealized net capital gains and losses	1,122							1,122	3
Change in unrealized foreign currency translation adjustments	79							79
Change in unamortized pension and other postretirement prior service credit	(1)							(1)
Change in discount rate for reserve for future policy benefits	(13)
Capital transactions for noncontrolling interest									67
Balance, end of period at Sep. 30, 2025	27,489	0	2,001	9	4,117	58,853	(37,773)	298	(16)
Balance, beginning of period at Jun. 30, 2025					4,084	55,400	(37,418)	(57)	(14)
Increase (decrease) in equity
Equity incentive plans activity, net					33
Net income (loss)	3,744					3,746			(2)
Dividends on common stock (declared per share of $1.00, $0.92, $3.00, and $2.76)						(264)
Dividends on preferred stock						(29)
Shares acquired							(363)
Shares reissued under equity incentive plans, net							8
Change in unrealized net capital gains and losses	315							315
Change in unrealized foreign currency translation adjustments	40							40
Change in unamortized pension and other postretirement prior service credit	(1)							(1)
Change in discount rate for reserve for future policy benefits	1							1
Balance, end of period at Sep. 30, 2025	27,489	$ 0	$ 2,001	$ 9	$ 4,117	$ 58,853	$ (37,773)	$ 298	$ (16)
Increase (decrease) in equity
Total Allstate shareholders’ equity	$ 27,505