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Related Party Transactions (Details)		1 Months Ended	3 Months Ended
	May 09, 2018 shares	Aug. 31, 2016 a	Mar. 31, 2021 USD ($)	Mar. 31, 2020 USD ($)	Mar. 05, 2021 a	Dec. 31, 2020 USD ($)	Nov. 05, 2019 a
Related Party Transaction [Line Items]
Company contribution to a multi employer 401K plan at discretionary amount of employee's cash compensation, maximum percentage			6.00%
Company contribution to a multi employer 401K plan at discretionary amount of employee's cash compensation, amount			$ 123,100	$ 120,700
Deferred compensation, employee contribution			2.00%
Deferred compensation, company contribution			$ 33,400	$ 49,500
Deferred compensation, company contribution (in percent)			3	3
Deferred compensation, cumulative unfunded liability			$ 2,900,000			$ 2,900,000
Ancillary costs and expenses			2,000,000.0	$ 2,200,000
Liability due to The Saul Organization for the Company's share of these ancillary costs and expenses			$ 869,700			$ 782,700
Percentage of annual increase in base rent			3.00%
Rent expense			$ 202,900	202,300
Insurance commissions and fees expense			99,100	$ 105,200
BF Saul Real Estate Investment Trust | Contribution Agreement
Related Party Transaction [Line Items]
Area of land | a							10.3
Twinbrook Metro Station | BF Saul Real Estate Investment Trust | Contribution Agreement
Related Party Transaction [Line Items]
Area of land | a					6.8
Twinbrook Metro Station Leasehold Interest | BF Saul Real Estate Investment Trust | Contribution Agreement
Related Party Transaction [Line Items]
Area of land | a					1.3
Ashbrook Marketplace | BF Saul Real Estate Investment Trust
Related Party Transaction [Line Items]
Area of real estate acquired (in acres) | a		13.7
Limited partnership units issued for purchase (in shares) | shares	176,680
Minimum | Ashbrook Marketplace | BF Saul Real Estate Investment Trust | Pro Forma
Related Party Transaction [Line Items]
Partnership units potentially issuable			3,000,000.0
Maximum | Ashbrook Marketplace | BF Saul Real Estate Investment Trust | Pro Forma
Related Party Transaction [Line Items]
Partnership units potentially issuable			$ 3,300,000

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