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		$ 3,722	$ 53,288	$ (34,471)	$ 426	$ (52)
Balance, beginning of period at Dec. 31, 2021			1,970		3,722	53,288	(34,471)	426	(52)
Increase (decrease) in equity
Preferred stock issuance, net of issuance costs			0
Preferred stock redemption			0
Equity incentive plans activity, net					43
Noncontrolling income (loss)	$ (1,046)					(1,012)			(34)
Dividends on common stock (declared per share of $0.89, $0.85, $2.67 and $2.55)						(698)
Dividends on preferred stock						(79)
Shares acquired							(2,142)
Shares reissued under equity incentive plans, net							95
Change in unrealized net capital gains and losses	(3,527)							(3,527)	(26)
Change in unrealized foreign currency translation adjustments	(135)							(135)
Change in unamortized pension and other postretirement prior service credit	(38)							(38)
Change in discount rate for reserve for future policy benefits	232							232
Balance, end of period at Sep. 30, 2022	17,571	$ 0	1,970	$ 9	3,765	51,499	(36,518)	(3,042)	(112)
Increase (decrease) in equity
Total equity			1,970		3,740	52,412	(35,858)	(2,209)	(91)
Balance, beginning of period at Jun. 30, 2022			1,970		3,740	52,412	(35,858)	(2,209)	(91)
Increase (decrease) in equity
Preferred stock issuance, net of issuance costs			0
Preferred stock redemption			0
Equity incentive plans activity, net					25
Noncontrolling income (loss)	(674)					(659)			(15)
Dividends on common stock (declared per share of $0.89, $0.85, $2.67 and $2.55)						(228)
Dividends on preferred stock						(26)
Shares acquired							(665)
Shares reissued under equity incentive plans, net							5
Change in unrealized net capital gains and losses	(789)							(789)	(6)
Change in unrealized foreign currency translation adjustments	(88)							(88)
Change in unamortized pension and other postretirement prior service credit	(8)							(8)
Change in discount rate for reserve for future policy benefits	52							52
Balance, end of period at Sep. 30, 2022	17,571	0	1,970	9	3,765	51,499	(36,518)	(3,042)	(112)
Increase (decrease) in equity
Total Allstate shareholders’ equity	17,683
Total equity	17,571	0	1,970	9	3,765	51,499	(36,518)	(3,042)	(112)
Total Allstate shareholders’ equity	17,488
Total equity	17,363		1,970		3,788	50,970	(36,857)	(2,392)	(125)
Balance, beginning of period at Dec. 31, 2022	17,363		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
Noncontrolling income (loss)	(1,700)					(1,677)			(23)
Dividends on common stock (declared per share of $0.89, $0.85, $2.67 and $2.55)						(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
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
Noncontrolling income (loss)	(4)					(5)			1
Dividends on common stock (declared per share of $0.89, $0.85, $2.67 and $2.55)						(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
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)