Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Revenues
Property and casualty insurance premiums (net of reinsurance ceded and indemnification programs of $1,869, $1,904 and $1,141)	$ 47,737	$ 44,039	$ 38,167
Other revenue	2,344	2,172	1,065
Net investment income	2,403	3,293	1,590
Net gains (losses) on investments and derivatives	(1,072)	1,084	1,087
Total revenues	51,412	50,588	41,909
Costs and expenses
Property and casualty insurance claims and claims expense (net of reinsurance ceded and indemnification programs of $1,600, $3,484 and $530)	37,264	29,318	22,001
Shelter-in-Place Payback expense	0	29	948
Accident, health and other policy benefits (net of reinsurance ceded of $28, $86 and $15)	1,061	1,049	549
Amortization of deferred policy acquisition costs	6,644	6,252	5,477
Operating costs and expenses	7,446	7,260	5,494
Pension and other postretirement remeasurement (gains) losses	116	(644)	(51)
Restructuring and related charges	51	170	253
Amortization of purchased intangibles	353	376	118
Interest expense	335	330	318
Total costs and expenses	53,270	44,140	35,107
(Loss) income from operations before income tax expense	(1,858)	6,448	6,802
Income tax (benefit) expense	(494)	1,289	1,373
Net (loss) income from continuing operations	(1,364)	5,159	5,429
(Loss) income from discontinued operations, net of tax	0	(3,593)	147
Net (loss) income	(1,364)	1,566	5,576
Less: Net loss attributable to noncontrolling interest	(53)	(33)	0
Net (loss) income attributable to Allstate	(1,311)	1,599	5,576
Less: Preferred stock dividends	105	114	115
Net (loss) income applicable to common shareholders ,Basic	(1,416)	1,485	5,461
Net (loss) income applicable to common shareholders , Dilluted	$ (1,416)	$ 1,485	$ 5,461
Basic
Continuing operations (in dollars per share)	$ (5.22)	$ 17.23	$ 17.06
Discontinued operations (in dollars per share)	0	(12.19)	0.47
Basic, Total (in dollars per share)	(5.22)	5.04	17.53
Diluted
Continuing operations (in dollars per share)	(5.22)	16.98	16.84
Discontinued operations (in dollars per share)	0	(12.02)	0.47
Diluted, Total (in dollars per share)	$ (5.22)	$ 4.96	$ 17.31
Weighted average common shares - Basic (in shares)	271.2	294.8	311.6
Weighted average common shares - Diluted (in shares)	271.2	299.1	315.5
Property and casualty insurance premiums
Revenues
Property and casualty insurance premiums (net of reinsurance ceded and indemnification programs of $1,869, $1,904 and $1,141)	$ 45,904	$ 42,218	$ 37,073
Accident and health insurance premiums and contract charges (net of reinsurance ceded of $38, $78 and $13)
Revenues
Property and casualty insurance premiums (net of reinsurance ceded and indemnification programs of $1,869, $1,904 and $1,141)	$ 1,833	$ 1,821	$ 1,094