Reserve for Future Policy Benefits and Contractholder Funds - Schedule of Contractholder Funds Activity (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2024	Mar. 31, 2023
Contractholder funds activity
Beginning balance	$ 888	$ 879
Deposits	34	33
Interest credited	9	8
Benefits	(2)	(4)
Surrenders and partial withdrawals	(6)	(5)
Contract charges	(30)	(30)
Other adjustments	(3)	(3)
Ending balance	890	878
Components of contractholder funds	$ 890	$ 878
Weighted-average crediting rate	4.20%	4.27%
Net amount at risk	$ 11,364	$ 11,780
Cash surrender value	731	722
Interest-sensitive life insurance
Contractholder funds activity
Ending balance	846	830
Components of contractholder funds	846	830
Fixed annuities
Contractholder funds activity
Ending balance	44	48
Components of contractholder funds	$ 44	$ 48

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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-Name Accounting Standards Codification
-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: