Consolidated Statements of Shareholders’ Equity - 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	Retained income Cumulative effect of change in accounting principle	Treasury stock	Accumulated other comprehensive income (loss)	Accumulated other comprehensive income (loss) Cumulative effect of change in accounting principle	Noncontrolling interest
Increase (decrease) in equity [Roll forward]
Total equity	$ (298)		$ 1,970		$ 3,498	$ 52,767	$ (21)	$ (31,331)	$ 3,304	$ (277)	$ 0
Balance, beginning of year at Dec. 31, 2020	(298)		1,970		3,498	52,767	(21)	(31,331)	3,304	(277)	0
Increase (decrease) in equity [Roll forward]
Acquisition			450								(16)
Preferred stock issuance, net of issuance costs			0
Preferred stock redemption			(450)
Forward contract on accelerated share repurchase agreement					113
Equity incentive plans activity, net					111
Net (loss) income	1,581					1,614					(33)
Dividends on common stock (declared per share of $3.56, $3.40 and $3.24)						(958)
Dividends on preferred stock						(114)
Shares acquired								(3,262)
Shares reissued under equity incentive plans, net								122
Change in unrealized net capital gains and losses	(2,583)								(2,583)		(3)
Change in unrealized foreign currency translation adjustments	(8)								(8)
Change in unamortized pension and other postretirement prior service credit	(59)								(59)
Change in discount rate for reserve for future policy benefits	49								49
Balance, end of year at Dec. 31, 2021	24,892	$ 0	1,970	$ 9	3,722	53,288	0	(34,471)	426	0	(52)
Increase (decrease) in equity [Roll forward]
Total Allstate shareholders’ equity	24,944
Total equity	24,892	0	1,970	9	3,722	53,288	0	(34,471)	426	0	(52)
Acquisition			0								0
Preferred stock issuance, net of issuance costs			0
Preferred stock redemption			0
Forward contract on accelerated share repurchase agreement					0
Equity incentive plans activity, net					66
Net (loss) income	(1,342)					(1,289)					(53)
Dividends on common stock (declared per share of $3.56, $3.40 and $3.24)						(924)
Dividends on preferred stock						(105)
Shares acquired								(2,496)
Shares reissued under equity incentive plans, net								110
Change in unrealized net capital gains and losses	(2,853)								(2,853)		(20)
Change in unrealized foreign currency translation adjustments	(150)								(150)
Change in unamortized pension and other postretirement prior service credit	(43)								(43)
Change in discount rate for reserve for future policy benefits	228								228
Balance, end of year at Dec. 31, 2022	17,363	0	1,970	9	3,788	50,970	0	(36,857)	(2,392)	0	(125)
Increase (decrease) in equity [Roll forward]
Total Allstate shareholders’ equity	17,488
Total equity	17,363	0	1,970	9	3,788	50,970	$ 0	(36,857)	(2,392)	$ 0	(125)
Acquisition			0								0
Preferred stock issuance, net of issuance costs			587
Preferred stock redemption			(556)
Forward contract on accelerated share repurchase agreement					0
Equity incentive plans activity, net					66
Net (loss) income	(213)					(188)					(25)
Dividends on common stock (declared per share of $3.56, $3.40 and $3.24)						(938)
Dividends on preferred stock						(128)
Shares acquired								(332)
Shares reissued under equity incentive plans, net								79
Change in unrealized net capital gains and losses	1,651								1,651		10
Change in unrealized foreign currency translation adjustments	67								67
Change in unamortized pension and other postretirement prior service credit	(16)								(16)
Change in discount rate for reserve for future policy benefits	(10)								(10)
Balance, end of year at Dec. 31, 2023	17,630	0	2,001	9	3,854	49,716		(37,110)	(700)		(140)
Increase (decrease) in equity [Roll forward]
Total Allstate shareholders’ equity	17,770
Total equity	$ 17,630	$ 0	$ 2,001	$ 9	$ 3,854	$ 49,716		$ (37,110)	$ (700)		$ (140)