Revenues from external customers attributed to all foreign countries in total from which the entity derives revenues.

No definition available.

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

- Definition

This element represents the minimum percentage of premiums from a single jurisdiction to be considered as significant for the disclosure of a concentration of risk.

+ References

No definition available.

+ Details

Name:	all_MinimumPercentageOfPremiumsToBeConsideredAsSignificant
Namespace Prefix:	all_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

This element represents the amount of premiums earned as a percentage of consolidated revenues.

+ References

No definition available.

+ Details

Name:	all_PremiumEarnedAsPercentageOfConsolidatedRevenues
Namespace Prefix:	all_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Income from agency and brokerage operations (includes sales of annuities and supplemental contracts); service charges, commissions, and fees from the sale of insurance and related services; and management fees from separate accounts, deferred annuities, and universal life products.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.13(c),(d))
-URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.4)
-URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

+ Details

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

- Definition

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8672-108599

+ Details

Name:	us-gaap_NumberOfReportableSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of states the entity operates in as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	us-gaap_NumberOfStatesInWhichEntityOperates
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

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

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=all_AllstateProtectionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=all_AllstateLifeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=all_ProtectionServicesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=us-gaap_NonUsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Reportable Segments - Narrative (Details) $ in Millions	12 Months Ended
Reportable Segments - Narrative (Details) $ in Millions	Dec. 31, 2020 USD ($) segment state	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Segment Reporting Information
Number of reportable segments \| segment	7
Allstate Protection
Segment Reporting Information
Premium earned as percentage of consolidated revenues	79.40%
Number of states in which entity operates \| state	50
Minimum percentage of premiums to be considered as significant	5.00%
Revenues from external customers generated outside the United States	$ 1,570	$ 1,370	$ 1,200
Allstate Life
Segment Reporting Information
Number of states in which entity operates \| state	50
Minimum percentage of premiums to be considered as significant	5.00%
Consumer product protection plans \| Protection Services
Segment Reporting Information
Insurance premiums, commissions and fees	$ 909	633	503
Consumer product protection plans \| Protection Services \| Non-US
Segment Reporting Information
Insurance premiums, commissions and fees	$ 188	$ 95	$ 61