Organization, Properties, Basis of Presentation, Financial Instruments and Recent Accounting Standards - Variable Interest Entities (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2024 USD ($)	Mar. 31, 2023 USD ($)	Dec. 31, 2023 USD ($)	Jan. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Variable interest entity
Gain on consolidation of Sponsored REIT		$ 394
Cash, cash equivalents and restricted cash	$ 37,779	$ 13,110	$ 127,880		$ 6,632
VIE at Consolidation
Real estate assets	884,733		890,824
Acquired real estate leases	5,971		6,694
Variable interest entities ("VIEs")
Variable interest entity
Gain on consolidation of Sponsored REIT	400
Cash, cash equivalents and restricted cash	2,080		2,167
VIE at Consolidation
Real estate assets	19,269		19,354	$ 19,695
Acquired real estate leases	67		$ 305	305
Total				20,000
Variable interest entities ("VIEs") | FSP Monument Circle LLC
Variable interest entity
Cash, cash equivalents and restricted cash	$ 3,000
Variable interest entities ("VIEs") | Level 3
VIE at Consolidation
Related party mortgage loan receivable				$ 20,000
Debt Securities, Available-for-Sale, Valuation Technique [Extensible Enumeration]				us-gaap:ValuationTechniqueDiscountedCashFlowMember
Variable interest entities ("VIEs") | Level 3 | Exit Cap Rate | Maximum
VIE at Consolidation
Measurement input				7.50
Variable interest entities ("VIEs") | Level 3 | Exit Cap Rate | Minimum
VIE at Consolidation
Measurement input				7.50
Variable interest entities ("VIEs") | Level 3 | Exit Cap Rate | Weighted Average
VIE at Consolidation
Measurement input				7.50
Variable interest entities ("VIEs") | Level 3 | Discount Rate | Maximum
VIE at Consolidation
Measurement input				9.50
Variable interest entities ("VIEs") | Level 3 | Discount Rate | Minimum
VIE at Consolidation
Measurement input				9.50
Variable interest entities ("VIEs") | Level 3 | Discount Rate | Weighted Average
VIE at Consolidation
Measurement input				9.50