General - Schedule of condensed consolidated statements of financial position (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022	Jun. 30, 2022	Dec. 31, 2021
Assets
Deferred policy acquisition costs	$ 5,607	$ 5,442	$ 5,049
Reinsurance and indemnification recoverables, net	9,151	9,619
Deferred income taxes	480	382
Other assets, net	6,278	5,904
Total assets	100,514	97,989
Liabilities
Reserve for future policy benefits	1,339	1,322
Components of contractholder funds	881	879	892	$ 890
Unearned premiums	23,355	22,299
Total liabilities	85,142	80,626
Equity
Retained income	48,766	50,970
Accumulated other comprehensive income (loss):
Unrealized net capital gains and losses	(1,845)	(2,255)
Discount rate for reserve for future policy benefits	(2)	(1)
Total accumulated other comprehensive income	(1,914)	(2,392)
Total Allstate shareholders’ equity	15,517	17,488	20,064
Total equity	15,372	17,363	19,973
Total liabilities and equity	$ 100,514	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
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 income		(2,389)
Total Allstate shareholders’ equity		17,475	20,115
Total equity		17,350	20,024
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
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 income		(3)
Total Allstate shareholders’ equity		13	(51)
Total equity		13	$ (51)
Total liabilities and equity		$ 32