XML 38 R27.htm IDEA: XBRL DOCUMENT
v3.25.1

Organization, Properties, Basis of Presentation, Financial Instruments and Recent Accounting Standards (Details) | 3 Months Ended |
--- | --- | ---
Mar. 31, 2025 ft² property | Mar. 31, 2024 ft² property
Properties |  |
Number of operating properties | 14 |
Number of properties | 15 | 17
Rentable square feet | ft² | 5,020,216 | 5,478,176
Number of properties classified as assets held for sale |  | 1
FSP Investments LLC |  |
Organization |  |
Ownership interest (as a percent) | 100.00% |
FSP Property Management LLC |  |
Organization |  |
Ownership interest (as a percent) | 100.00% |
FSP Holdings LLC |  |
Organization |  |
Ownership interest (as a percent) | 100.00% |
FSP Protective TRS Corp. |  |
Organization |  |
Ownership interest (as a percent) | 100.00% |

X
- Definition Number of real estate properties owned that are classified as assets held for sale. + References No definition available. + Details
Name: | fsp_NumberOfPropertiesClassifiedAsAssetsHeldForSale
Namespace Prefix: | fsp_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of real estate properties owned and consolidated by the entity. + References No definition available. + Details
Name: | fsp_NumberOfPropertiesOwnedAndConsolidated
Namespace Prefix: | fsp_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- References No definition available. + Details
Name: | fsp_OrganizationAndConsolidationLineItems
Namespace Prefix: | fsp_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Area of a real estate property. + References No definition available. + Details
Name: | us-gaap_AreaOfRealEstateProperty
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:areaItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage investment held by members or limited partners of limited liability company (LLC) or limited partnership (LP). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 272 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482987/272-10-50-3 + Details
Name: | us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPMembersOrLimitedPartnersOwnershipInterest
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition The number of real estate properties owned as of the balance sheet date. + References No definition available. + Details
Name: | us-gaap_NumberOfRealEstateProperties
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_RealEstateInvestmentsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | srt_OwnershipAxis=fsp_FSPInvestmentsLLCMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_OwnershipAxis=fsp_FSPPropertyManagementLLCMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_OwnershipAxis=fsp_FSPHoldingsLLCMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_OwnershipAxis=fsp_FSPProtectiveTRSCorpMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |