Represents the maturity period of advances.

No definition available.

Name:	all_AdvancesMaturityPeriod
Namespace Prefix:	all_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Agent Loans

+ References

No definition available.

+ Details

Name:	all_AgentLoans
Namespace Prefix:	all_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Represents the amount available for borrowings under the agreement.

+ References

No definition available.

+ Details

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

- Definition

Represents the amount of loan outstanding under the Liquidity Agreement as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	all_AmountOfLoanOutstandingUnderAgreement
Namespace Prefix:	all_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the commitment fee as a percentage of the amount of the capital and surplus maximum that remains available at the beginning of the period.

+ References

No definition available.

+ Details

Name:	all_CommitmentFeeAsPercentageOfCapitalAndSurplusThatRemainsAvailableAtBeginningOfPeriod
Namespace Prefix:	all_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the percentage of voting stock to be held as per terms of the agreement.

+ References

No definition available.

+ Details

Name:	all_DebtInstrumentCovenantVotingStockHoldingPercentage
Namespace Prefix:	all_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the written notice period to demand payables.

+ References

No definition available.

+ Details

Name:	all_DemandPayablesWrittenNoticePeriod
Namespace Prefix:	all_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the amount of fees and commissions earned from providing services such as leasing of space or maintaining: (1) depositor accounts; (2) transfer agent; (3) fiduciary and trust; (4) brokerage and underwriting; (5) mortgage; (6) credit cards; (7) correspondent clearing; and (8) other such services and activities performed for others.

+ References

No definition available.

+ Details

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

- Definition

Gain or loss on transaction between entities under common control recorded directly to equity.

+ References

No definition available.

+ Details

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

- Definition

Represents the percentage of risk based capital for adequacy needs as defined by the National Association of Insurance Commissioners.

+ References

No definition available.

+ Details

Name:	all_StatutoryAccountingPracticesRiskBasedCapitalRatio
Namespace Prefix:	all_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the risk-based capital ratio at which agreement will be terminated.

+ References

No definition available.

+ Details

Name:	all_StatutoryAccountingPracticesRiskBasedCapitalRatioTerminationTerm
Namespace Prefix:	all_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Excludes cash and cash equivalents within disposal group and discontinued operation.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 210
-Section 45
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=118262064&loc=SL116631418-115840

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.1)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 210
-Section 45
-Paragraph 21
-URI http://asc.fasb.org/extlink&oid=118262064&loc=SL116631419-115840

+ Details

Name:	us-gaap_Cash
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Maximum potential amount of future undiscounted payments that could be required under the credit derivative, before reduction for potential recoveries under recourse or collateralization provisions.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4K
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5708775-113959

+ Details

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

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount, after accumulated amortization, of deferred policy acquisition costs and present value of future profits from insurance contract acquired in business combination.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=35755530&loc=d3e11264-158415

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.7)
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 20
-Section S99
-Paragraph 2
-Subparagraph (2)
-URI http://asc.fasb.org/extlink&oid=27015749&loc=d3e569990-122904

+ Details

Name:	us-gaap_DeferredPolicyAcquisitionCostsAndValueOfBusinessAcquired
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=118943654&loc=d3e12069-110248

+ Details

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

- Definition

Amount of interest expense incurred on a debt or other obligation to related party.

+ References

No definition available.

+ Details

Name:	us-gaap_InterestExpenseRelatedParty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of interest income earned from interest-bearing assets owed to the entity by related party.

+ References

No definition available.

+ Details

Name:	us-gaap_InterestIncomeRelatedParty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Sum of the carrying amounts as of the balance sheet date of all investments.

+ References

+ Details

Name:	us-gaap_Investments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, before effect of reinsurance, of present value of future benefit to be paid to or on behalf of policyholder and related expense less present value of future net premium receivable under insurance contract.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 50
-Paragraph 6
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=117419472&loc=d3e14931-158439

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 55
-Paragraph 29E
-URI http://asc.fasb.org/extlink&oid=117419784&loc=SL117819541-158441

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(13)(a)(1))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 65
-Paragraph 2
-Subparagraph (g)(1)
-URI http://asc.fasb.org/extlink&oid=117419843&loc=SL117420844-207641

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 50
-Paragraph 6
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=117419472&loc=d3e14931-158439

+ Details

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

- Definition

The amount for notes payable (written promise to pay), due to related parties.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(k)(1))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.17)
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

+ Details

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

- Definition

Cash outflow in the form of capital distributions and dividends to common shareholders, preferred shareholders and noncontrolling interests.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3291-108585

+ Details

Name:	us-gaap_PaymentsOfDividends
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of cash outflow to acquire investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3213-108585

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3151-108585

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=118954083&loc=d3e26853-111562

+ Details

Name:	us-gaap_PaymentsToAcquireAvailableForSaleSecuritiesDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- 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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 25
-Paragraph 14
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=117419144&loc=d3e13193-158430

+ Details

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

- Definition

Amount, after valuation allowance, recoverable under reinsurance contracts including premium paid under reinsurance contracts. Examples include, but are not limited to, settled and unsettled claims, incurred but not reported losses, loss adjustment expense, premium paid, policy benefits and policy reserves.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.(a),6)
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 20
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=99397103&loc=d3e6824-158387

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 310
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=99404803&loc=d3e21409-158489

+ Details

Name:	us-gaap_ReinsuranceRecoverables
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Expenses recognized resulting from transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party.

+ References

+ Details

Name:	us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_RelatedPartyTransactionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_TypeOfArrangementAxis=all_LiquidityAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=all_IntercompanyLoanAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=all_RevolvingLoanCreditAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=us-gaap_CapitalSupportAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ProductOrServiceAxis=all_StructuredSettlementAnnuitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ConsolidatedEntitiesAxis=srt_ParentCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=us-gaap_SubsidiaryOfCommonParentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=all_ALICReinsuranceCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditDerivativesByContractTypeAxis=us-gaap_HybridInstrumentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=srt_AffiliatedEntityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=all_AllstateFinancialServicesLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CounterpartyNameAxis=all_AllstateFinanceCompanyAgencyLoansLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=us-gaap_BeneficialOwnerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CounterpartyNameAxis=all_AllstateAssuranceCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_UnderlyingAssetClassAxis=us-gaap_CollateralizedLoanObligationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Related Party Transactions - Narrative and Other (Details) - USD ($)			12 Months Ended
	Dec. 01, 2020	Dec. 02, 2016	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 16, 2019	Dec. 31, 2017	Dec. 22, 2016
Related Party Transactions
Allocation of operating expenses			$ 191,000,000	$ 211,000,000	$ 235,000,000
Cash			36,000,000	43,000,000	52,000,000		$ 145,000,000
Notes due to related parties			214,000,000	214,000,000
Interest expense			7,000,000	5,000,000	5,000,000
Total reserve for life-contingent contract benefits			11,800,000,000	11,272,000,000
Surplus note			5,335,000,000	4,406,000,000	5,444,000,000
Total investments			34,798,000,000	33,607,000,000
Contractholder funds			16,481,000,000	16,711,000,000	17,470,000,000		18,592,000,000
Reinsurance Recoverables, Including Reinsurance Premium Paid			1,989,000,000	2,490,000,000
Deferred policy acquisition costs			973,000,000	947,000,000	1,232,000,000		$ 1,156,000,000
Liquidity agreement
Related Party Transactions
Amount of loan outstanding under agreement			0	0
Liquidity agreement \| Maximum
Related Party Transactions
Amount available for borrowings under the agreement			$ 1,000,000,000
Advances maturity period (in days)			364 days
Liquidity agreement \| Minimum
Related Party Transactions
Notice period for payables on demand (in days)			10 days
Intercompany loan agreement
Related Party Transactions
Amount of loan outstanding under agreement			$ 0	0
Intercompany loan agreement \| Maximum
Related Party Transactions
Amount available for borrowings under the agreement			1,000,000,000
Revolving loan credit agreement
Related Party Transactions
Amount of loan outstanding under agreement			0	0
Capital support agreement
Related Party Transactions
Amount of loan outstanding under agreement			$ 0	0
Commitment fee as a percentage of the amount of the capital and surplus maximum that remains available at the beginning of the period			1.00%
Capital support agreement \| Maximum
Related Party Transactions
Amount available for borrowings under the agreement			$ 1,000,000,000
Capital support agreement \| Minimum
Related Party Transactions
Percentage of risk-based capital ratio			150.00%
Minimum risk-based capital ratio at which agreement will be terminated (as a percent)			300.00%
Voting stock to be held as per agreement (as a percent)			50.00%
Structured settlement annuities \| AIC
Related Party Transactions
Total reserve for life-contingent contract benefits			$ 4,730,000,000	4,570,000,000
Subsidiary of Common Parent \| ALIC Reinsurance Company \| Hybrid Instrument
Related Party Transactions
Credit derivative, maximum exposure, undiscounted			1,750,000,000
Affiliate
Related Party Transactions
Fee and commission expenses			3,000,000	3,000,000	3,000,000
Allstate Financial Services, LLC
Related Party Transactions
Payments of dividends			0	75,000,000	250,000,000
Allstate Finance Company Agency Loans LLC \| Beneficial Owner
Related Party Transactions
Agent loans			568,000,000	612,000,000
Cash			0	1,000,000
Notes due to related parties			214,000,000	214,000,000
Allstate Assurance Company
Related Party Transactions
Total reserve for life-contingent contract benefits	$ 118,000,000
Gain (Loss) on the transaction	(59,000,000)
Total investments	534,000,000
Contractholder funds	256,000,000
Reinsurance Recoverables, Including Reinsurance Premium Paid	397,000,000
Deferred policy acquisition costs	$ 245,000,000
Allstate Assurance Company \| Subsidiary of Common Parent
Related Party Transactions
Surplus note		$ 40,000,000
Notes payable interest rate (as a percent)		3.07%
Interest income, related party			1,000,000	1,000,000	$ 1,000,000
Collateralized Loan Obligations
Related Party Transactions
Agent loans, fair value						$ 222,000,000		$ 419,000,000
Collateralized Loan Obligations \| Affiliate
Related Party Transactions
Agent loans, fair value			$ 641,000,000	$ 641,000,000