Ancillary Costs and Expenses

No definition available.

Name:	bfs_AncillaryCostsAndExpenses
Namespace Prefix:	bfs_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

Name:	bfs_DeferredCompensationArrangementWithIndividualContributionsByPlanParticipantsPercentageOfSalaryMaximum
Namespace Prefix:	bfs_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

Name:	bfs_DeferredCompensationArrangementwithIndividualEmployerContributionPercentageDeferredCompensation
Namespace Prefix:	bfs_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Operating Leases Annual Increase in Rent Expense

+ References

No definition available.

+ Details

Name:	bfs_OperatingLeasesAnnualIncreaseInRentExpense
Namespace Prefix:	bfs_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Real Estate, Equity Interests Issued Or Issuable, Value Assigned

+ References

No definition available.

+ Details

Name:	bfs_RealEstateEquityInterestsIssuedOrIssuableValueAssigned
Namespace Prefix:	bfs_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

Name:	bfs_RealEstateEquityInterestsIssuedOrIssuableValueAssignedPerShare
Namespace Prefix:	bfs_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

Name:	bfs_RealEstateEquityInterestsIssuedorIssuableNumberofShares
Namespace Prefix:	bfs_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Related Party Transaction, Area of Real Estate Acquired

+ References

No definition available.

+ Details

Name:	bfs_RelatedPartyTransactionAreaofRealEstateAcquired
Namespace Prefix:	bfs_
Data Type:	num:areaItemType
Balance Type:	na
Period Type:	duration

- Definition

Area of land held.

+ References

No definition available.

+ Details

Name:	us-gaap_AreaOfLand
Namespace Prefix:	us-gaap_
Data Type:	num:areaItemType
Balance Type:	na
Period Type:	instant

- Definition

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

+ References

No definition available.

+ Details

Name:	us-gaap_DeferredCompensationArrangementWithIndividualContributionsByEmployer
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 710
-SubTopic 10
-Section 30
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6409875&loc=d3e20015-108363

+ Details

Name:	us-gaap_DeferredCompensationArrangementWithIndividualRecordedLiability
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

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

+ References

No definition available.

+ Details

Name:	us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

Name:	us-gaap_DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(k)(1))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.17)
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.15(3),(4))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Name:	us-gaap_DueToRelatedPartiesCurrentAndNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4304-108586

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4332-108586

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4313-108586

+ Details

Name:	us-gaap_NoncashOrPartNoncashAcquisitionNoncashFinancialOrEquityInstrumentConsiderationSharesIssued1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.2(a),(d))
-URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227

+ Details

Name:	us-gaap_OperatingInsuranceAndClaimsCostsProduction
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 55
-Paragraph 53
-URI http://asc.fasb.org/extlink&oid=77888399&loc=SL77918982-209971

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918686-209980

+ Details

Name:	us-gaap_OperatingLeaseCost
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4313-108586

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4332-108586

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4304-108586

+ Details

Name:	us-gaap_OtherSignificantNoncashTransactionValueOfConsiderationGiven1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

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.

+ References

No definition available.

+ Details

Name:	us-gaap_RelatedPartyTransactionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_SubsidiarySaleOfStockAxis=bfs_ContributionAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=bfs_BFSaulRealEstateInvestmentTrustMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=bfs_LandContributedInContributionAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=bfs_LeaseholdInterestContributedInContributionAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=bfs_AshbrookMarketplaceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementScenarioAxis=srt_ScenarioForecastMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Related Party Transactions (Details)			1 Months Ended	3 Months Ended	6 Months Ended
Related Party Transactions (Details)	Nov. 05, 2019 USD ($) a $ / shares shares	May 09, 2018 shares	Aug. 31, 2016 a	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 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					$ 200,900	$ 180,100
Deferred compensation, employee contribution, percentage					2.00%
Deferred compensation, company contribution, amount					$ 109,400	$ 113,200
Deferred compensation, company contribution, percentage					3	3
Deferred compensation, cumulative unfunded liability					$ 3,300,000		$ 3,100,000
Ancillary costs and expenses					4,200,000	$ 4,400,000
Liability due to The Saul Organization for the Company's share of these ancillary costs and expenses					$ 740,300		$ 918,700
Percentage of annual increase in base rent					3.00%
Rent expense					$ 407,600	386,100
Insurance commissions and fees expense					$ 224,400	$ 172,800
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 [Member]
Related Party Transaction [Line Items]
Area of land \| a	6.8
BF Saul Real Estate Investment Trust \| Leasehold Interest Contributed In Contribution Agreement [Member]
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 \| Subsequent Event \| Forecast \| Ashbrook Marketplace \| BF Saul Real Estate Investment Trust
Related Party Transaction [Line Items]
Partnership units potentially issuable				$ 3,500,000
Maximum \| Subsequent Event \| Forecast \| Ashbrook Marketplace \| BF Saul Real Estate Investment Trust
Related Party Transaction [Line Items]
Partnership units potentially issuable				$ 4,000,000.0