Ancillary Costs and Expenses

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- Definition

Deferred Compensation Arrangement with Individual, Contributions by Plan Participants, Percentage of Salary, Maximum

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Deferred Compensation Arrangement with Individual, Employer Contribution, Percentage Deferred Compensation

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- Definition

Operating Leases Annual Increase in Rent Expense

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Real Estate, Equity Interests Issued Or Issuable, Value Assigned

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Real Estate, Equity Interests Issued Or Issuable, Value Assigned Per Share

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Real Estate, Equity Interests Issued or Issuable, Number of Shares

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Related Party Transaction, Area of Real Estate Acquired

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Area of land held.

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Amount of contributions made by employer into fund established for purposes of making future disbursement to individual in accordance with deferred compensation arrangement.

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The carrying amount of the liability as of the balance sheet date to an individual under a deferred compensation arrangement. This amount may be the result of periodic accruals made over the period of active employment, or reflect termination benefits resulting contractual terms or a death benefit.

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- Definition

Amount of discretionary contributions made by an employer to a defined contribution plan.

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Maximum percentage of employee gross pay the employee may contribute to a defined contribution plan.

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Carrying amount as of the balance sheet date of obligations due all related parties.

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The number of shares issued as [noncash or part noncash] consideration for a business or asset acquired. Noncash is defined as transactions during a period that affect recognized assets or liabilities but that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

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- Definition

Insurance and claims costs directly related to goods produced and sold, or services rendered, during the reporting period.

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Amount of single lease cost, calculated by allocation of remaining cost of lease over remaining lease term. Includes, but is not limited to, single lease cost, after impairment of right-of-use asset, calculated by amortization of remaining right-of-use asset and accretion of lease liability.

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The value of the noncash (or part noncash) consideration given (for example, liability, equity) in a transaction. Noncash is defined as transactions during a period that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of a transaction not resulting in cash receipts or cash payments in the period.

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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.

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Related Party Transactions (Details)			1 Months Ended	9 Months Ended		12 Months Ended
Related Party Transactions (Details)	Nov. 05, 2019 USD ($) a $ / shares shares	May 09, 2018 shares	Aug. 31, 2016 a	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	May 31, 2021 USD ($)	Dec. 31, 2019 USD ($)
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				$ 255,200	$ 264,300
Deferred compensation, employee contribution				2.00%
Deferred compensation, company contribution				$ 164,800	$ 186,300
Deferred compensation, company contribution (in percent)				3	3
Deferred compensation, cumulative unfunded liability				$ 2,800,000			$ 3,100,000
Ancillary costs and expenses				6,000,000.0	$ 6,400,000
Liability due to The Saul Organization for the Company's share of these ancillary costs and expenses				$ 659,000			$ 918,700
Percentage of annual increase in base rent				3.00%
Rent expense				$ 609,200	593,500
Insurance commissions and fees expense				$ 320,300	$ 284,900
Contribution Agreement
Related Party Transaction [Line Items]
Number of partnership units issued in transaction (in shares) \| shares	1,416,071
Value of units issued (in dollars per share) \| $ / shares	$ 56.00
Value assigned to units issued	$ 79,300,000
BF Saul Real Estate Investment Trust \| Land Contributed In Contribution Agreement
Related Party Transaction [Line Items]
Area of land \| a	6.8
BF Saul Real Estate Investment Trust \| Leasehold Interest Contributed In 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 \| Forecast
Related Party Transaction [Line Items]
Partnership units potentially issuable						$ 3,200,000
Maximum \| Ashbrook Marketplace \| BF Saul Real Estate Investment Trust \| Forecast
Related Party Transaction [Line Items]
Partnership units potentially issuable						$ 3,500,000