Reserve for Future Policy Benefits and Contractholder Funds - Schedule of Contractholder Funds Activity (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2023	Sep. 30, 2022
Contractholder funds activity
Beginning balance	$ 879	$ 890
Deposits	99	102
Interest credited	25	25
Benefits	(8)	(15)
Surrenders and partial withdrawals	(15)	(16)
Contract charges	(90)	(88)
Other adjustments	(6)	(5)
Ending balance	884	893
Components of contractholder funds	$ 884	$ 893
Weighted-average crediting rate	4.26%	4.28%
Net amount at risk	$ 11,550	$ 11,796
Cash surrender value	728	728
Interest- sensitive life
Contractholder funds activity
Ending balance	837	841
Components of contractholder funds	837	841
Fixed annuities
Contractholder funds activity
Ending balance	47	52
Components of contractholder funds	$ 47	$ 52

Decrease in the liability for policyholder contract deposits resulting from benefits paid out of contract holder funds.

No definition available.

Name:	all_BenefitsPaidFromContractHolderFunds
Namespace Prefix:	all_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

An amount that an insurer deducts from a contract holder's account, as compensation for services rendered.

+ References

No definition available.

+ Details

Name:	all_ContractCharges
Namespace Prefix:	all_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Increase in the liability for policyholder contract deposits resulting from amounts received during the period from the insured.

+ References

No definition available.

+ Details

Name:	all_DepositsToContractHolderFunds
Namespace Prefix:	all_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Increase in the liability for policyholder contract deposits resulting from interest credited during the period by the insurer to policy owner accounts.

+ References

No definition available.

+ Details

Name:	all_InterestToContractHolderFunds
Namespace Prefix:	all_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Movement in Policyholder Contract Deposits

+ References

No definition available.

+ Details

Name:	all_MovementInPolicyholderContractDepositsRollForward
Namespace Prefix:	all_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Other adjustments during the period to the liability for policyholder contract deposits, not specified elsewhere in the taxonomy.

+ References

No definition available.

+ Details

Name:	all_PolicyholderContractDepositsAdjustmentsOther
Namespace Prefix:	all_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Decrease in the liability for policyholder contract deposits resulting from surrenders and partial withdrawals out of contract holder funds.

+ References

No definition available.

+ Details

Name:	all_SurrendersAndPartialWithdrawalsFromContractHolderFunds
Namespace Prefix:	all_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of cash to be paid to policyholder upon termination and surrender of long-duration contract issued by insurance entity.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 29F
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480046/944-40-55-29F

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
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-Section 50
-Paragraph 7A
-Subparagraph (b)(3)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480081/944-40-50-7A

+ Details

Name:	us-gaap_CashSurrenderValueDuePolicyholdersAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of guaranteed benefit in excess of current account balance of policyholder account balance.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 29F
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480046/944-40-55-29F

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 7A
-Subparagraph (b)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480081/944-40-50-7A

+ Details

Name:	us-gaap_PolicyholderAccountBalanceNetAmountAtRisk
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Weighted-average crediting rate for liability for policyholder account balance, calculated at a point in time.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 29F
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480046/944-40-55-29F

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 7A
-Subparagraph (b)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480081/944-40-50-7A

+ Details

Name:	us-gaap_PolicyholderAccountBalanceWeightedAverageCreditingRate
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of liability due to policyholder for deposit held under long-duration contract issued by insurance entity.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 25
-Paragraph 14
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479250/944-40-25-14

+ Details

Name:	us-gaap_PolicyholderContractDeposits
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	srt_ProductOrServiceAxis=us-gaap_InterestSensitiveLifeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ProductOrServiceAxis=us-gaap_FixedAnnuityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: