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
Increase (decrease) in equity
Total equity			$ 1,970		$ 3,788	$ 50,970	$ (36,857)	$ (2,392)	$ (125)
Balance, beginning of period at Dec. 31, 2022			1,970		3,788	50,970	(36,857)	(2,392)	(125)
Increase (decrease) in equity
Preferred stock issuance, net of issuance costs			587
Preferred stock redemption			(556)
Equity incentive plans activity, net					23
Net income (loss)	$ (1,700)					(1,677)			(23)
Dividends on common stock (declared per share of $0.92, $0.89, $2.76, and $2.67 )						(703)
Dividends on preferred stock						(99)
Shares acquired							(333)
Shares reissued under equity incentive plans, net							41
Change in unrealized net capital gains and losses	(257)							(257)	2
Change in unrealized foreign currency translation adjustments	64							64
Change in unamortized pension and other postretirement prior service credit	(14)							(14)
Change in discount rate for reserve for future policy benefits	29							29
Capital transaction for noncontrolling interest									0
Balance, end of period at Sep. 30, 2023	14,447	$ 0	2,001	$ 9	3,811	48,491	(37,149)	(2,570)	(146)
Increase (decrease) in equity
Total equity			2,001		3,786	48,766	(37,131)	(1,914)	(145)
Balance, beginning of period at Jun. 30, 2023			2,001		3,786	48,766	(37,131)	(1,914)	(145)
Increase (decrease) in equity
Preferred stock issuance, net of issuance costs			0
Preferred stock redemption			0
Equity incentive plans activity, net					25
Net income (loss)	(4)					(5)			1
Dividends on common stock (declared per share of $0.92, $0.89, $2.76, and $2.67 )						(234)
Dividends on preferred stock						(36)
Shares acquired							(26)
Shares reissued under equity incentive plans, net							8
Change in unrealized net capital gains and losses	(667)							(667)	(2)
Change in unrealized foreign currency translation adjustments	(14)							(14)
Change in unamortized pension and other postretirement prior service credit	(5)							(5)
Change in discount rate for reserve for future policy benefits	30							30
Capital transaction for noncontrolling interest									0
Balance, end of period at Sep. 30, 2023	14,447	0	2,001	9	3,811	48,491	(37,149)	(2,570)	(146)
Increase (decrease) in equity
Total Allstate shareholders’ equity	14,593
Total equity	14,447	0	2,001	9	3,811	48,491	(37,149)	(2,570)	(146)
Total Allstate shareholders’ equity	17,770
Total equity	17,630		2,001		3,854	49,716	(37,110)	(700)	(140)
Balance, beginning of period at Dec. 31, 2023	17,630		2,001		3,854	49,716	(37,110)	(700)	(140)
Increase (decrease) in equity
Preferred stock issuance, net of issuance costs			0
Preferred stock redemption			0
Equity incentive plans activity, net					133
Net income (loss)	2,709					2,739			(30)
Dividends on common stock (declared per share of $0.92, $0.89, $2.76, and $2.67 )						(732)
Dividends on preferred stock						(88)
Shares acquired							0
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)
Capital transaction 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)
Increase (decrease) in equity
Total equity			2,001		3,927	50,718	(37,036)	(1,026)	(20)
Balance, beginning of period at Jun. 30, 2024			2,001		3,927	50,718	(37,036)	(1,026)	(20)
Increase (decrease) in equity
Preferred stock issuance, net of issuance costs			0
Preferred stock redemption			0
Equity incentive plans activity, net					60
Net income (loss)	1,164					1,190			(26)
Dividends on common stock (declared per share of $0.92, $0.89, $2.76, and $2.67 )						(244)
Dividends on preferred stock						(29)
Shares acquired							0
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							0
Change in discount rate for reserve for future policy benefits	(36)							(36)
Capital transaction for noncontrolling interest									0
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 equity	$ 20,838	$ 0	$ 2,001	$ 9	$ 3,987	$ 51,635	$ (37,006)	$ 251	$ (39)