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	Deferred employee stock ownership plan (“ESOP”) expense	Treasury stock	Accumulated other comprehensive income (loss)	Noncontrolling interest
Increase (decrease) in equity [Roll forward]
Total equity			$ 1,930		$ 3,310	$ 44,033	$ 21	$ (3)	$ (28,085)	$ 118	$ 0
Balance, beginning of year at Dec. 31, 2018			1,930		3,310	44,033	21	(3)	(28,085)	118	0
Increase (decrease) in equity [Roll forward]
Acquisition			0								0
Preferred stock issuance, net of issuance costs			1,414
Preferred stock redemption			(1,096)
Forward contract on accelerated share repurchase agreement					75
Equity incentive plans activity					78
Net income	$ 4,847					4,847					0
Dividends on common stock (declared per share of $3.24, $2.16 and $2.00)						(658)
Dividends on preferred stock						(169)
Payments								3
Shares acquired									(1,810)
Shares reissued under equity incentive plans, net									149
Change in unrealized net capital gains and losses	1,889									1,889	0
Change in unrealized foreign currency translation adjustments	(10)									(10)
Change in unamortized pension and other postretirement prior service credit	(47)									(47)
Balance, end of year at Dec. 31, 2019	25,998	$ 0	2,248	$ 9	3,463	48,074	(88)	0	(29,746)	1,950	0
Increase (decrease) in equity [Roll forward]
Total Allstate shareholders’ equity	25,998
Total equity	25,998	0	2,248	9	3,463	48,074	(88)	0	(29,746)	1,950	0
Acquisition			0								0
Preferred stock issuance, net of issuance costs			0
Preferred stock redemption			(278)
Forward contract on accelerated share repurchase agreement					(38)
Equity incentive plans activity					73
Net income	5,576					5,576					0
Dividends on common stock (declared per share of $3.24, $2.16 and $2.00)						(680)
Dividends on preferred stock						(115)
Payments								0
Shares acquired									(1,700)
Shares reissued under equity incentive plans, net									115
Change in unrealized net capital gains and losses	1,293									1,293	0
Change in unrealized foreign currency translation adjustments	52									52
Change in unamortized pension and other postretirement prior service credit	9									9
Balance, end of year at Dec. 31, 2020	30,217	0	1,970	9	3,498	52,767	0	0	(31,331)	3,304	0
Increase (decrease) in equity [Roll forward]
Total Allstate shareholders’ equity	30,217
Total equity	30,217	0	1,970	9	3,498	52,767	$ 0	0	(31,331)	3,304	0
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					111
Net income	1,566					1,599					(33)
Dividends on common stock (declared per share of $3.24, $2.16 and $2.00)						(958)
Dividends on preferred stock						(114)
Payments								0
Shares acquired									(3,262)
Shares reissued under equity incentive plans, net									122
Change in unrealized net capital gains and losses	(2,582)									(2,582)	(3)
Change in unrealized foreign currency translation adjustments	(8)									(8)
Change in unamortized pension and other postretirement prior service credit	(59)									(59)
Balance, end of year at Dec. 31, 2021	25,127	0	1,970	9	3,722	53,294		0	(34,471)	655	(52)
Increase (decrease) in equity [Roll forward]
Total Allstate shareholders’ equity	25,179
Total equity	$ 25,127	$ 0	$ 1,970	$ 9	$ 3,722	$ 53,294		$ 0	$ (34,471)	$ 655	$ (52)