XML 64 R50.htm IDEA: XBRL DOCUMENT
v3.20.4

Long-Term Lease Obligations - Additional Information (Detail) | 12 Months Ended
--- | ---
Dec. 31, 2020 USD ($) property | Dec. 31, 2019 USD ($) property | Dec. 31, 2018 USD ($)
Leases Disclosure [Line Items] |  |  |
Number of properties subject to noncancelable long-term lease | property | 0 | 0 |
Rent expense | $ 799,300 | $ 806,500 |
Rent expense |  |  | $ 779,800
Flagship Center |  |  |
Leases Disclosure [Line Items] |  |  |
Number of developed parcels | property | 2 |  |
90-year Ground Leasehold Interest |  |  |
Leases Disclosure [Line Items] |  |  |
Ground leasehold interest period | 90 years |  |
Minimum annual lease rent over lease term | $ 1 |  |
99-year Ground Lease |  |  |
Leases Disclosure [Line Items] |  |  |
Ground leasehold interest period | 99 years |  |
Minimum annual lease rent over lease term | $ 1 |  |
Percent of underlying land held under a 99-year ground lease | 3.40% |  |

X
- Definition Annual Rental Payments Over Lease Term + References No definition available. + Details
Name: | bfs_AnnualRentalPaymentsOverLeaseTerm
Namespace Prefix: | bfs_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Lease Expiration Period + References No definition available. + Details
Name: | bfs_LeaseExpirationPeriod
Namespace Prefix: | bfs_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Lessee Leasing Arrangements, Number of Properties Under Lease + References No definition available. + Details
Name: | bfs_LesseeLeasingArrangementsNumberofPropertiesUnderLease
Namespace Prefix: | bfs_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of Developed Parcels + References No definition available. + Details
Name: | bfs_NumberofDevelopedParcels
Namespace Prefix: | bfs_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of Lease Commitment + References No definition available. + Details
Name: | bfs_PercentageOfLeaseCommitment
Namespace Prefix: | bfs_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- 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_LesseeLeaseDescriptionLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of operating lease expense. Excludes sublease income. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 45 -Paragraph 4 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121603541&loc=SL77918638-209977 + Details
Name: | us-gaap_OperatingLeaseExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Rental expense for the reporting period incurred under operating leases, including minimum and any contingent rent expense, net of related sublease income. + References Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=121573735&loc=d3e41499-112717 + Details
Name: | us-gaap_OperatingLeasesRentExpenseNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=bfs_FlagshipCenterMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | bfs_CapitalizedCostByTypeAxis=bfs_NinetyYearGroundLeaseMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | bfs_CapitalizedCostByTypeAxis=bfs_NinetyNineYearGroundLeaseMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |