General - Schedule of Condensed Consolidated Statements of Financial Position (unaudited) (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022	Dec. 31, 2021
Assets
Deferred policy acquisition costs	$ 5,824	$ 5,442	$ 5,291
Reinsurance and indemnification recoverables, net	9,083	9,619
Deferred income taxes	816	382
Other assets, net	6,196	5,904
Total assets	101,176	97,989
Liabilities
Reserve for future policy benefits	1,309	1,322
Contractholder funds	884	879	893	$ 890
Unearned premiums	24,518	22,299
Total liabilities	86,729	80,626
Equity
Retained income	48,491	50,970
Accumulated other comprehensive income (loss):
Unrealized net capital gains and losses	(2,512)	(2,255)
Discount rate for reserve for future policy benefits	28	(1)
Total accumulated other comprehensive loss	(2,570)	(2,392)
Total Allstate shareholders’ equity	14,593	17,488	17,683
Total equity	14,447	17,363	17,571
Total liabilities and equity	$ 101,176	97,989
As reported
Assets
Deferred policy acquisition costs		5,418
Reinsurance and indemnification recoverables, net		9,606
Deferred income taxes		386
Other assets, net		5,905
Total assets		97,957
Liabilities
Reserve for future policy benefits		1,273
Contractholder funds		897
Unearned premiums		22,311
Total liabilities		80,607
Equity
Retained income		50,954
Accumulated other comprehensive income (loss):
Unrealized net capital gains and losses		(2,253)
Discount rate for reserve for future policy benefits		0
Total accumulated other comprehensive loss		(2,389)
Total Allstate shareholders’ equity		17,475	17,673
Total equity		17,350	17,561
Total liabilities and equity		97,957
Impact of change
Assets
Deferred policy acquisition costs		24
Reinsurance and indemnification recoverables, net		13
Deferred income taxes		(4)
Other assets, net		(1)
Total assets		32
Liabilities
Reserve for future policy benefits		49
Contractholder funds		(18)
Unearned premiums		(12)
Total liabilities		19
Equity
Retained income		16
Accumulated other comprehensive income (loss):
Unrealized net capital gains and losses		(2)
Discount rate for reserve for future policy benefits		(1)
Total accumulated other comprehensive loss		(3)
Total Allstate shareholders’ equity		13	10
Total equity		13	$ 10
Total liabilities and equity		$ 32