Number of communities combined in the predecessor financial statement.

No definition available.

Name:	jan_NumberOfCombinedCommunities
Namespace Prefix:	jan_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of life plan communities directly owned by the reporting entity as of the reporting date.

+ References

No definition available.

+ Details

Name:	jan_NumberOfDirectlyOwnedLifePlanCommunities
Namespace Prefix:	jan_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of senior housing communities held by the reporting entity through unconsolidated joint venture as of the reporting date.

+ References

No definition available.

+ Details

Name:	jan_NumberOfSeniorHousingCommunitiesHeldThroughUnconsolidatedJointVenture
Namespace Prefix:	jan_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of voting and economic rights.

+ References

No definition available.

+ Details

Name:	jan_PercentageOfVotingAndEconomicRights
Namespace Prefix:	jan_
Data Type:	dtr-types:percentItemType
Balance Type:	na
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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 808
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479402/808-10-50-1

+ Details

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

- Definition

Number of common units issued of limited liability company (LLC).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480008/505-10-S99-1

+ Details

Name:	us-gaap_CommonUnitIssued
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

The number of shares issued or sold by the subsidiary or equity method investee per stock transaction.

+ References

No definition available.

+ Details

Name:	us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Details

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

- Details

Name:	us-gaap_StatementClassOfStockAxis=jan_ClassA1CommonStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_OwnershipAxis=jan_JanusLivingOPMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsidiarySaleOfStockAxis=us-gaap_IPOMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=jan_JanusLivingOPCommonUnitsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Business (Details)		1 Months Ended	12 Months Ended
Business (Details)	Mar. 23, 2026 shares	Mar. 31, 2026 shares	Dec. 31, 2025 property plan
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of life plan communities \| plan			15
Number of senior housing communities held through JV \| property			19
Number of combined properties \| property			15
Healthpeak
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Percentage of voting and economic rights	81.60%
Class A-1 Shares \| Janus Living OP
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Common unit, issued (in shares)	187,222,996	187,222,996
Class A-1 Shares \| IPO
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of shares issued in transaction (in shares)		48,300,000
Class A-1 Shares \| Healthpeak
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of shares issued in transaction (in shares)	138,816,246	138,816,246
Janus Living OP Common Units \| Healthpeak
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of shares issued in transaction (in shares)	75,917,780	75,917,780