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Area of a real estate property.

No definition available.

Name:	us-gaap_AreaOfRealEstateProperty
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:areaItemType
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Percentage investment held by members or limited partners of limited liability company (LLC) or limited partnership (LP).

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

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Data Type:	dtr-types:percentItemType
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The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

No definition available.

Name:	us-gaap_MinorityInterestOwnershipPercentageByParent
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Data Type:	dtr-types:percentItemType
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The number of real estate properties owned as of the balance sheet date.

No definition available.

Name:	us-gaap_NumberOfRealEstateProperties
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
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- References

No definition available.

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Name:	srt_OwnershipAxis=fsp_FSPInvestmentsLLCMember
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Name:	srt_OwnershipAxis=fsp_FSPPropertyManagementLLCMember
Namespace Prefix:
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Name:	srt_OwnershipAxis=fsp_FSPHoldingsLLCMember
Namespace Prefix:
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