General - Schedule of condensed consolidated statements of financial position (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022	Dec. 31, 2021
Assets
Deferred policy acquisition costs	$ 5,471	$ 5,442	$ 4,843
Reinsurance and indemnification recoverables, net	9,528	9,619
Deferred income taxes	345	382
Other assets, net	5,758	5,904
Total assets	99,631	97,989
Liabilities
Reserve for future policy benefits	1,338	1,322
Components of contractholder funds	878	879	891	$ 890
Unearned premiums	22,499	22,299
Total liabilities	82,258	80,626
Equity
Retained income	50,388	50,970
Unrealized net capital gains and losses	(1,573)	(2,255)
Accumulated other comprehensive income:
Discount rate for reserve for future policy benefits	(10)	(1)
Total AOCI	(1,673)	(2,392)
Total Allstate shareholders’ equity	17,494	17,488	23,075
Total equity	17,373	17,363	23,001
Total liabilities and equity	$ 99,631	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
Components of contractholder funds		897
Unearned premiums		22,311
Total liabilities		80,607
Equity
Retained income		50,954
Unrealized net capital gains and losses		(2,253)
Accumulated other comprehensive income:
Discount rate for reserve for future policy benefits		0
Total AOCI		(2,389)
Total Allstate shareholders’ equity		17,475	23,212
Total equity		17,350	23,138
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
Components of contractholder funds		(18)
Unearned premiums		(12)
Total liabilities		19
Equity
Retained income		16
Unrealized net capital gains and losses		(2)
Accumulated other comprehensive income:
Discount rate for reserve for future policy benefits		(1)
Total AOCI		(3)
Total Allstate shareholders’ equity		13	(137)
Total equity		13	$ (137)
Total liabilities and equity		$ 32