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Mortgage Notes Payable, Revolving Credit Facility, Interest Expense and Amortization of Deferred Debt Costs - Summary of Notes Payable (Additional Information) (Detail) (USD $) | 0 Months Ended | 12 Months Ended | 0 Months Ended |  |
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Apr. 26, 2012 | Feb. 27, 2013 | Apr. 11, 2012 | Mar. 19, 2013 | May 28, 2013 | Oct. 25, 2013 | Dec. 31, 2014 | Sep. 04, 2013 | Dec. 31, 2013 | Dec. 31, 2012
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate |  |  |  |  |  |  | 3.65%us-gaap_DebtInstrumentInterestRateEffectivePercentage |  |  | 4.85%us-gaap_DebtInstrumentInterestRateEffectivePercentage |
Line of credit facility, maximum borrowing capacity |  |  |  |  |  |  | $ 231,600,000 us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity |  |  |  |
White Oak Shopping Center |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Amortization period | 25 years |  |  |  |  |  |  |  |  |  |
Debt instrument final payment | 18,500,000 bfs_DebtInstrumentFinalPaymentAmount / bfs_RealEstatePropertyNameAxis = bfs_WhiteOakShoppingCenterMember |  |  |  |  |  |  |  |  |  |
Debt instrument amount | 10,500,000 us-gaap_DebtInstrumentFaceAmount / bfs_RealEstatePropertyNameAxis = bfs_WhiteOakShoppingCenterMember |  |  |  |  |  |  |  |  |  |
Northrock |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Amortization period |  | 25 years |  |  |  |  |  |  |  |  |
Debt instrument final payment |  | 14,200,000 bfs_DebtInstrumentFinalPaymentAmount / bfs_RealEstatePropertyNameAxis = bfs_NorthrockMember |  |  |  |  |  |  |  |  |
Debt instrument amount |  | 15,000,000 us-gaap_DebtInstrumentFaceAmount / bfs_RealEstatePropertyNameAxis = bfs_NorthrockMember |  |  |  |  |  |  |  |  |
Interest rate spread on LIBOR |  | 1.65%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1 / bfs_RealEstatePropertyNameAxis = bfs_NorthrockMember |  |  |  |  |  |  |  |  |
Metro Pike Center |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Amortization period |  | 25 years |  |  |  |  |  |  |  |  |
Debt instrument final payment |  | 14,800,000 bfs_DebtInstrumentFinalPaymentAmount / bfs_RealEstatePropertyNameAxis = bfs_MetroPikeCenterMember |  |  |  |  |  |  |  |  |
Debt instrument amount |  | 15,600,000 us-gaap_DebtInstrumentFaceAmount / bfs_RealEstatePropertyNameAxis = bfs_MetroPikeCenterMember |  |  |  |  |  |  |  |  |
Interest rate spread on LIBOR |  | 1.65%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1 / bfs_RealEstatePropertyNameAxis = bfs_MetroPikeCenterMember |  |  |  |  |  |  |  |  |
5.84% due May 2027 | Seven Corners |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Amortization period |  |  | 25 years |  |  |  |  |  |  |  |
Debt instrument amount |  |  | 73,000,000 us-gaap_DebtInstrumentFaceAmount / us-gaap_LongtermDebtTypeAxis = bfs_FivePointEightFourMaturingMayTwentyTwentySevenMember / bfs_RealEstatePropertyNameAxis = bfs_SevenCornersMember |  |  |  |  |  |  |  |
4.04% due April 2028 | Hampshire Langley |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Principal and interest payments |  |  |  | 95,400 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_LongtermDebtTypeAxis = bfs_FourPointZeroFourMaturingAprilTwentyTwentyEightMember / bfs_RealEstatePropertyNameAxis = bfs_HampshireLangleyMember |  |  |  |  |  |  |
Debt instrument final payment |  |  |  | 9,500,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_LongtermDebtTypeAxis = bfs_FourPointZeroFourMaturingAprilTwentyTwentyEightMember / bfs_RealEstatePropertyNameAxis = bfs_HampshireLangleyMember |  |  |  |  |  |  |
Debt instrument amount |  |  |  | 18,000,000 us-gaap_DebtInstrumentFaceAmount / us-gaap_LongtermDebtTypeAxis = bfs_FourPointZeroFourMaturingAprilTwentyTwentyEightMember / bfs_RealEstatePropertyNameAxis = bfs_HampshireLangleyMember |  |  |  |  |  |  |
3.51% due June 2028 | Beacon Center |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Principal and interest payments |  |  |  |  | 203,200 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_LongtermDebtTypeAxis = bfs_ThreePointFiveOneMaturingJuneTwentyTwentyEightMember / bfs_RealEstatePropertyNameAxis = bfs_BeaconCenterMember |  |  |  |  |  |
Amortization period |  |  |  |  | 20 years |  |  |  |  |  |
Debt instrument final payment |  |  |  |  | 11,400,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_LongtermDebtTypeAxis = bfs_ThreePointFiveOneMaturingJuneTwentyTwentyEightMember / bfs_RealEstatePropertyNameAxis = bfs_BeaconCenterMember |  |  |  |  |  |
Debt instrument amount |  |  |  |  | 35,000,000 us-gaap_DebtInstrumentFaceAmount / us-gaap_LongtermDebtTypeAxis = bfs_ThreePointFiveOneMaturingJuneTwentyTwentyEightMember / bfs_RealEstatePropertyNameAxis = bfs_BeaconCenterMember |  |  |  |  |  |
3.99% due September 2028 | Seabreeze Plaza |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Debt instrument amount |  |  |  |  |  |  |  |  | 18,000,000 us-gaap_DebtInstrumentFaceAmount / us-gaap_LongtermDebtTypeAxis = bfs_ThreePointNineNineMaturingSeptemberTwentyTwentyEightMember / bfs_RealEstatePropertyNameAxis = bfs_SeabreezePlazaMember |  |
4.88% due September 2032 | Park Van Ness |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Amortization period |  |  |  |  |  | 25 years |  |  |  |  |
Fixed Rate Mortgage Notes Payable |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate |  |  |  |  |  |  | 5.70%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember | [1] |  |  |
Fixed Rate Mortgage Notes Payable | White Oak Shopping Center |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate | 4.90%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / bfs_RealEstatePropertyNameAxis = bfs_WhiteOakShoppingCenterMember |  |  |  |  |  |  |  |  |  |
Fixed Rate Mortgage Notes Payable | 7.45% due June 2015 |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate |  |  |  |  |  |  | 7.45%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SevenPointFourFiveMaturingJuneTwentyFifteenMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 7.45% due June 2015 | Shops at Fairfax and Boulevard |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Principal and interest payments |  |  |  |  |  |  | 156,000 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SevenPointFourFiveMaturingJuneTwentyFifteenMember / bfs_RealEstatePropertyNameAxis = bfs_ShopsatFairfaxandBoulevardMember |  |  |  |
Amortization period |  |  |  |  |  |  | 23 years |  |  |  |
Debt instrument final payment |  |  |  |  |  |  | 15,200,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SevenPointFourFiveMaturingJuneTwentyFifteenMember / bfs_RealEstatePropertyNameAxis = bfs_ShopsatFairfaxandBoulevardMember |  |  |  |
Amortization of principal |  |  |  |  |  |  | 729,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SevenPointFourFiveMaturingJuneTwentyFifteenMember / bfs_RealEstatePropertyNameAxis = bfs_ShopsatFairfaxandBoulevardMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 6.01% due February 2018 |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate |  |  |  |  |  |  | 6.01%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SixPointZeroOneMaturingFebruaryTwentyEighteenMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 6.01% due February 2018 | Washington Square |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Principal and interest payments |  |  |  |  |  |  | 264,000 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SixPointZeroOneMaturingFebruaryTwentyEighteenMember / bfs_RealEstatePropertyNameAxis = bfs_WashingtonSquareMember |  |  |  |
Amortization period |  |  |  |  |  |  | 27 years 6 months |  |  |  |
Debt instrument final payment |  |  |  |  |  |  | 28,000,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SixPointZeroOneMaturingFebruaryTwentyEighteenMember / bfs_RealEstatePropertyNameAxis = bfs_WashingtonSquareMember |  |  |  |
Amortization of principal |  |  |  |  |  |  | 1,200,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SixPointZeroOneMaturingFebruaryTwentyEighteenMember / bfs_RealEstatePropertyNameAxis = bfs_WashingtonSquareMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 5.88% due January 2019 |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate |  |  |  |  |  |  | 5.88%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointEightEightMaturingJanuaryTwentyNineteenMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 5.88% due January 2019 | Broadlands Village, The Glen and Kentlands Square I |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Principal and interest payments |  |  |  |  |  |  | 306,000 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointEightEightMaturingJanuaryTwentyNineteenMember / bfs_RealEstatePropertyNameAxis = bfs_BroadlandsVillageTheGlenandKentlandsSquareIMember |  |  |  |
Amortization period |  |  |  |  |  |  | 25 years |  |  |  |
Debt instrument final payment |  |  |  |  |  |  | 28,400,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointEightEightMaturingJanuaryTwentyNineteenMember / bfs_RealEstatePropertyNameAxis = bfs_BroadlandsVillageTheGlenandKentlandsSquareIMember |  |  |  |
Amortization of principal |  |  |  |  |  |  | 1,500,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointEightEightMaturingJanuaryTwentyNineteenMember / bfs_RealEstatePropertyNameAxis = bfs_BroadlandsVillageTheGlenandKentlandsSquareIMember |  |  |  |
Number of shopping centers |  |  |  |  |  |  | 3 bfs_NumberOfShoppingCenters / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointEightEightMaturingJanuaryTwentyNineteenMember / bfs_RealEstatePropertyNameAxis = bfs_BroadlandsVillageTheGlenandKentlandsSquareIMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 5.76% due May 2019 |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate |  |  |  |  |  |  | 5.76%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointSevenSixMaturingMayTwentyNineteenMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 5.76% due May 2019 | Olde Forte Village |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Principal and interest payments |  |  |  |  |  |  | 98,000 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointSevenSixMaturingMayTwentyNineteenMember / bfs_RealEstatePropertyNameAxis = bfs_OldeForteVillageMember |  |  |  |
Amortization period |  |  |  |  |  |  | 25 years |  |  |  |
Debt instrument final payment |  |  |  |  |  |  | 9,000,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointSevenSixMaturingMayTwentyNineteenMember / bfs_RealEstatePropertyNameAxis = bfs_OldeForteVillageMember |  |  |  |
Amortization of principal |  |  |  |  |  |  | 495,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointSevenSixMaturingMayTwentyNineteenMember / bfs_RealEstatePropertyNameAxis = bfs_OldeForteVillageMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 5.62% due July 2019 |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate |  |  |  |  |  |  | 5.62%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointSixTwoMaturingJulyTwentyNineteenMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 5.62% due July 2019 | Countryside |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Principal and interest payments |  |  |  |  |  |  | 133,000 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointSixTwoMaturingJulyTwentyNineteenMember / bfs_RealEstatePropertyNameAxis = bfs_CountrysideMember |  |  |  |
Amortization period |  |  |  |  |  |  | 25 years |  |  |  |
Debt instrument final payment |  |  |  |  |  |  | 12,300,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointSixTwoMaturingJulyTwentyNineteenMember / bfs_RealEstatePropertyNameAxis = bfs_CountrysideMember |  |  |  |
Amortization of principal |  |  |  |  |  |  | 682,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointSixTwoMaturingJulyTwentyNineteenMember / bfs_RealEstatePropertyNameAxis = bfs_CountrysideMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 5.79% due September 2019 |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate |  |  |  |  |  |  | 5.79%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointSevenNineMaturingSeptemberTwentyNineteenMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 5.79% due September 2019 | Briggs Chancy MarketPlace |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Principal and interest payments |  |  |  |  |  |  | 133,000 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointSevenNineMaturingSeptemberTwentyNineteenMember / bfs_RealEstatePropertyNameAxis = bfs_BriggsChancyMarketPlaceMember |  |  |  |
Amortization period |  |  |  |  |  |  | 25 years |  |  |  |
Debt instrument final payment |  |  |  |  |  |  | 12,200,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointSevenNineMaturingSeptemberTwentyNineteenMember / bfs_RealEstatePropertyNameAxis = bfs_BriggsChancyMarketPlaceMember |  |  |  |
Amortization of principal |  |  |  |  |  |  | 658,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointSevenNineMaturingSeptemberTwentyNineteenMember / bfs_RealEstatePropertyNameAxis = bfs_BriggsChancyMarketPlaceMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 5.22% due January 2020 |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate |  |  |  |  |  |  | 5.22%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointTwoTwoMaturingJanuaryTwentyTwentyMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 5.22% due January 2020 | Shops at Monocacy |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Principal and interest payments |  |  |  |  |  |  | 112,000 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointTwoTwoMaturingJanuaryTwentyTwentyMember / bfs_RealEstatePropertyNameAxis = bfs_ShopsatMonocacyMember |  |  |  |
Amortization period |  |  |  |  |  |  | 25 years |  |  |  |
Debt instrument final payment |  |  |  |  |  |  | 10,600,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointTwoTwoMaturingJanuaryTwentyTwentyMember / bfs_RealEstatePropertyNameAxis = bfs_ShopsatMonocacyMember |  |  |  |
Amortization of principal |  |  |  |  |  |  | 596,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointTwoTwoMaturingJanuaryTwentyTwentyMember / bfs_RealEstatePropertyNameAxis = bfs_ShopsatMonocacyMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 5.60% due May 2020 |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate |  |  |  |  |  |  | 5.60%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointSixZeroMaturingMayTwentyTwentyMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 5.60% due May 2020 | Boca Valley Plaza |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Principal and interest payments |  |  |  |  |  |  | 75,000 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointSixZeroMaturingMayTwentyTwentyMember / bfs_RealEstatePropertyNameAxis = bfs_BocaValleyPlazaMember |  |  |  |
Amortization period |  |  |  |  |  |  | 30 years |  |  |  |
Debt instrument final payment |  |  |  |  |  |  | 9,100,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointSixZeroMaturingMayTwentyTwentyMember / bfs_RealEstatePropertyNameAxis = bfs_BocaValleyPlazaMember |  |  |  |
Amortization of principal |  |  |  |  |  |  | 278,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointSixZeroMaturingMayTwentyTwentyMember / bfs_RealEstatePropertyNameAxis = bfs_BocaValleyPlazaMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 5.30% due June 2020 |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate |  |  |  |  |  |  | 5.30%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointThreeZeroMaturingJuneTwentyTwentyMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 5.30% due June 2020 | Palm Springs Center |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Principal and interest payments |  |  |  |  |  |  | 75,000 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointThreeZeroMaturingJuneTwentyTwentyMember / bfs_RealEstatePropertyNameAxis = bfs_PalmSpringsCenterMember |  |  |  |
Amortization period |  |  |  |  |  |  | 25 years |  |  |  |
Debt instrument final payment |  |  |  |  |  |  | 7,100,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointThreeZeroMaturingJuneTwentyTwentyMember / bfs_RealEstatePropertyNameAxis = bfs_PalmSpringsCenterMember |  |  |  |
Amortization of principal |  |  |  |  |  |  | 386,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointThreeZeroMaturingJuneTwentyTwentyMember / bfs_RealEstatePropertyNameAxis = bfs_PalmSpringsCenterMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 5.83% due July 2020 |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate |  |  |  |  |  |  | 5.83%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointEightThreeMaturingJulyTwentyTwentyMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 5.83% due July 2020 | Thruway |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Principal and interest payments |  |  |  |  |  |  | 289,000 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointEightThreeMaturingJulyTwentyTwentyMember / bfs_RealEstatePropertyNameAxis = bfs_ThruwayMember |  |  |  |
Amortization period |  |  |  |  |  |  | 25 years |  |  |  |
Debt instrument final payment |  |  |  |  |  |  | 34,800,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointEightThreeMaturingJulyTwentyTwentyMember / bfs_RealEstatePropertyNameAxis = bfs_ThruwayMember |  |  |  |
Amortization of principal |  |  |  |  |  |  | 1,021,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointEightThreeMaturingJulyTwentyTwentyMember / bfs_RealEstatePropertyNameAxis = bfs_ThruwayMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 5.81% due February 2021 |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate |  |  |  |  |  |  | 5.81%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointEightOneMaturingFebruaryTwentyTwentyOneMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 5.81% due February 2021 | Jamestown Place |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Principal and interest payments |  |  |  |  |  |  | 66,000 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointEightOneMaturingFebruaryTwentyTwentyOneMember / bfs_RealEstatePropertyNameAxis = bfs_JamestownPlaceMember |  |  |  |
Amortization period |  |  |  |  |  |  | 25 years |  |  |  |
Debt instrument final payment |  |  |  |  |  |  | 6,100,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointEightOneMaturingFebruaryTwentyTwentyOneMember / bfs_RealEstatePropertyNameAxis = bfs_JamestownPlaceMember |  |  |  |
Amortization of principal |  |  |  |  |  |  | 303,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointEightOneMaturingFebruaryTwentyTwentyOneMember / bfs_RealEstatePropertyNameAxis = bfs_JamestownPlaceMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 6.01% due August 2021 |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate |  |  |  |  |  |  | 6.01%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SixPointZeroOneMaturingAugustTwentyTwentyOneMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 6.01% due August 2021 | Hunt Club Corners |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Principal and interest payments |  |  |  |  |  |  | 42,000 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SixPointZeroOneMaturingAugustTwentyTwentyOneMember / bfs_RealEstatePropertyNameAxis = bfs_HuntClubCornersMember |  |  |  |
Amortization period |  |  |  |  |  |  | 30 years |  |  |  |
Debt instrument final payment |  |  |  |  |  |  | 5,000,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SixPointZeroOneMaturingAugustTwentyTwentyOneMember / bfs_RealEstatePropertyNameAxis = bfs_HuntClubCornersMember |  |  |  |
Amortization of principal |  |  |  |  |  |  | 133,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SixPointZeroOneMaturingAugustTwentyTwentyOneMember / bfs_RealEstatePropertyNameAxis = bfs_HuntClubCornersMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 5.62% due June 2022 |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate |  |  |  |  |  |  | 5.62%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointSixTwoMaturingJuneTwentyTwentyTwoMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 5.62% due June 2022 | Landsowne Town Center |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Principal and interest payments |  |  |  |  |  |  | 230,000 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointSixTwoMaturingJuneTwentyTwentyTwoMember / bfs_RealEstatePropertyNameAxis = bfs_LandsowneTownCenterMember |  |  |  |
Amortization period |  |  |  |  |  |  | 30 years |  |  |  |
Debt instrument final payment |  |  |  |  |  |  | 28,200,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointSixTwoMaturingJuneTwentyTwentyTwoMember / bfs_RealEstatePropertyNameAxis = bfs_LandsowneTownCenterMember |  |  |  |
Amortization of principal |  |  |  |  |  |  | 759,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointSixTwoMaturingJuneTwentyTwentyTwoMember / bfs_RealEstatePropertyNameAxis = bfs_LandsowneTownCenterMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 6.08% due September 2022 |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate |  |  |  |  |  |  | 6.08%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SixPointZeroEightMaturingSeptemberTwentyTwentyTwoMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 6.08% due September 2022 | Orchard Park |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Principal and interest payments |  |  |  |  |  |  | 73,000 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SixPointZeroEightMaturingSeptemberTwentyTwentyTwoMember / bfs_RealEstatePropertyNameAxis = bfs_OrchardParkMember |  |  |  |
Amortization period |  |  |  |  |  |  | 30 years |  |  |  |
Debt instrument final payment |  |  |  |  |  |  | 8,600,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SixPointZeroEightMaturingSeptemberTwentyTwentyTwoMember / bfs_RealEstatePropertyNameAxis = bfs_OrchardParkMember |  |  |  |
Amortization of principal |  |  |  |  |  |  | 212,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SixPointZeroEightMaturingSeptemberTwentyTwentyTwoMember / bfs_RealEstatePropertyNameAxis = bfs_OrchardParkMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 6.43% due April 2023 |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate |  |  |  |  |  |  | 6.43%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SixPointFourThreeMaturingAprilTwentyTwentyThreeMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 6.43% due April 2023 | BJs Wholesale |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Principal and interest payments |  |  |  |  |  |  | 80,000 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SixPointFourThreeMaturingAprilTwentyTwentyThreeMember / bfs_RealEstatePropertyNameAxis = bfs_BJsWholesaleMember |  |  |  |
Amortization period |  |  |  |  |  |  | 30 years |  |  |  |
Debt instrument final payment |  |  |  |  |  |  | 9,300,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SixPointFourThreeMaturingAprilTwentyTwentyThreeMember / bfs_RealEstatePropertyNameAxis = bfs_BJsWholesaleMember |  |  |  |
Amortization of principal |  |  |  |  |  |  | 208,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SixPointFourThreeMaturingAprilTwentyTwentyThreeMember / bfs_RealEstatePropertyNameAxis = bfs_BJsWholesaleMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 6.28% due February 2024 |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate |  |  |  |  |  |  | 6.28%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SixPointTwoEightMaturingFebruaryTwentyTwentyFourMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 6.28% due February 2024 | Great Falls Shopping Center |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Principal and interest payments |  |  |  |  |  |  | 138,000 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SixPointTwoEightMaturingFebruaryTwentyTwentyFourMember / bfs_RealEstatePropertyNameAxis = bfs_GreatFallsShoppingCenterMember |  |  |  |
Amortization period |  |  |  |  |  |  | 26 years |  |  |  |
Debt instrument final payment |  |  |  |  |  |  | 6,300,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SixPointTwoEightMaturingFebruaryTwentyTwentyFourMember / bfs_RealEstatePropertyNameAxis = bfs_GreatFallsShoppingCenterMember |  |  |  |
Amortization of principal |  |  |  |  |  |  | 689,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SixPointTwoEightMaturingFebruaryTwentyTwentyFourMember / bfs_RealEstatePropertyNameAxis = bfs_GreatFallsShoppingCenterMember |  |  |  |
Number of notes |  |  |  |  |  |  | 3 bfs_NumberOfNotes / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SixPointTwoEightMaturingFebruaryTwentyTwentyFourMember / bfs_RealEstatePropertyNameAxis = bfs_GreatFallsShoppingCenterMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 7.35% due June 2024 |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate |  |  |  |  |  |  | 7.35%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SevenPointThreeFiveMaturingJuneTwentyTwentyFourMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 7.35% due June 2024 | Leesburg Pike |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Principal and interest payments |  |  |  |  |  |  | 135,000 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SevenPointThreeFiveMaturingJuneTwentyTwentyFourMember / bfs_RealEstatePropertyNameAxis = bfs_LeesburgPikeMember |  |  |  |
Amortization period |  |  |  |  |  |  | 25 years |  |  |  |
Debt instrument final payment |  |  |  |  |  |  | 11,500,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SevenPointThreeFiveMaturingJuneTwentyTwentyFourMember / bfs_RealEstatePropertyNameAxis = bfs_LeesburgPikeMember |  |  |  |
Amortization of principal |  |  |  |  |  |  | 373,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SevenPointThreeFiveMaturingJuneTwentyTwentyFourMember / bfs_RealEstatePropertyNameAxis = bfs_LeesburgPikeMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 7.60% due June 2024 |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate |  |  |  |  |  |  | 7.60%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SevenPointSixZeroMaturingJuneTwentyTwentyFourMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 7.60% due June 2024 | Village Center |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Principal and interest payments |  |  |  |  |  |  | 119,000 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SevenPointSixZeroMaturingJuneTwentyTwentyFourMember / bfs_RealEstatePropertyNameAxis = bfs_VillageCenterMember |  |  |  |
Amortization period |  |  |  |  |  |  | 25 years |  |  |  |
Debt instrument final payment |  |  |  |  |  |  | 10,100,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SevenPointSixZeroMaturingJuneTwentyTwentyFourMember / bfs_RealEstatePropertyNameAxis = bfs_VillageCenterMember |  |  |  |
Amortization of principal |  |  |  |  |  |  | 314,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SevenPointSixZeroMaturingJuneTwentyTwentyFourMember / bfs_RealEstatePropertyNameAxis = bfs_VillageCenterMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 7.02% due July 2024 |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate |  |  |  |  |  |  | 7.02%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SevenPointZeroTwoMaturingJulyTwentyTwentyFourMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 7.02% due July 2024 | White Oak Shopping Center |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Principal and interest payments |  |  |  |  |  |  | 193,000 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SevenPointZeroTwoMaturingJulyTwentyTwentyFourMember / bfs_RealEstatePropertyNameAxis = bfs_WhiteOakShoppingCenterMember |  |  |  |
Amortization period |  |  |  |  |  |  | 24 years 4 months 24 days |  |  |  |
Debt instrument final payment |  |  |  |  |  |  | 18,500,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SevenPointZeroTwoMaturingJulyTwentyTwentyFourMember / bfs_RealEstatePropertyNameAxis = bfs_WhiteOakShoppingCenterMember |  |  |  |
Amortization of principal |  |  |  |  |  |  | 514,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SevenPointZeroTwoMaturingJulyTwentyTwentyFourMember / bfs_RealEstatePropertyNameAxis = bfs_WhiteOakShoppingCenterMember |  |  |  |
Debt instrument amount |  |  |  |  |  |  |  |  |  |  | 10,500,000.0 us-gaap_DebtInstrumentFaceAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SevenPointZeroTwoMaturingJulyTwentyTwentyFourMember / bfs_RealEstatePropertyNameAxis = bfs_WhiteOakShoppingCenterMember
Fixed Rate Mortgage Notes Payable | 7.45% due July 2024 |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate |  |  |  |  |  |  | 7.45%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SevenPointFourFiveMaturingJulyTwentyTwentyFourMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 7.45% due July 2024 | Avenel Business Park |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Principal and interest payments |  |  |  |  |  |  | 246,000 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SevenPointFourFiveMaturingJulyTwentyTwentyFourMember / bfs_RealEstatePropertyNameAxis = bfs_AvenelBusinessParkMember |  |  |  |
Amortization period |  |  |  |  |  |  | 25 years |  |  |  |
Debt instrument final payment |  |  |  |  |  |  | 20,900,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SevenPointFourFiveMaturingJulyTwentyTwentyFourMember / bfs_RealEstatePropertyNameAxis = bfs_AvenelBusinessParkMember |  |  |  |
Amortization of principal |  |  |  |  |  |  | 664,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SevenPointFourFiveMaturingJulyTwentyTwentyFourMember / bfs_RealEstatePropertyNameAxis = bfs_AvenelBusinessParkMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 7.30% due January 2025 |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate |  |  |  |  |  |  | 7.30%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SevenPointThreeZeroMaturingJulyTwentyTwentyFiveMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 7.30% due January 2025 | Ashburn Village |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Principal and interest payments |  |  |  |  |  |  | 240,000 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SevenPointThreeZeroMaturingJulyTwentyTwentyFiveMember / bfs_RealEstatePropertyNameAxis = bfs_AshburnVillageMember |  |  |  |
Amortization period |  |  |  |  |  |  | 25 years |  |  |  |
Debt instrument final payment |  |  |  |  |  |  | 20,500,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SevenPointThreeZeroMaturingJulyTwentyTwentyFiveMember / bfs_RealEstatePropertyNameAxis = bfs_AshburnVillageMember |  |  |  |
Amortization of principal |  |  |  |  |  |  | 641,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SevenPointThreeZeroMaturingJulyTwentyTwentyFiveMember / bfs_RealEstatePropertyNameAxis = bfs_AshburnVillageMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 6.18% due January 2026 |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate |  |  |  |  |  |  | 6.18%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SixPointOneEightMaturingJanuaryTwentyTwentySixMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 6.18% due January 2026 | Ravenwood |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Principal and interest payments |  |  |  |  |  |  | 111,000 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SixPointOneEightMaturingJanuaryTwentyTwentySixMember / bfs_RealEstatePropertyNameAxis = bfs_RavenwoodMember |  |  |  |
Amortization period |  |  |  |  |  |  | 25 years |  |  |  |
Debt instrument final payment |  |  |  |  |  |  | 10,100,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SixPointOneEightMaturingJanuaryTwentyTwentySixMember / bfs_RealEstatePropertyNameAxis = bfs_RavenwoodMember |  |  |  |
Amortization of principal |  |  |  |  |  |  | 352,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_SixPointOneEightMaturingJanuaryTwentyTwentySixMember / bfs_RealEstatePropertyNameAxis = bfs_RavenwoodMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 5.31% due April 2026 |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate |  |  |  |  |  |  | 5.31%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointThreeOneMaturingAprilTwentyTwentySixMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 5.31% due April 2026 | Clarendon Center |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Principal and interest payments |  |  |  |  |  |  | 753,000 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointThreeOneMaturingAprilTwentyTwentySixMember / bfs_RealEstatePropertyNameAxis = bfs_ClarendonCenterMember |  |  |  |
Amortization period |  |  |  |  |  |  | 25 years |  |  |  |
Debt instrument final payment |  |  |  |  |  |  | 70,500,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointThreeOneMaturingAprilTwentyTwentySixMember / bfs_RealEstatePropertyNameAxis = bfs_ClarendonCenterMember |  |  |  |
Amortization of principal |  |  |  |  |  |  | 2,800,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointThreeOneMaturingAprilTwentyTwentySixMember / bfs_RealEstatePropertyNameAxis = bfs_ClarendonCenterMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 4.30% due October 2026 |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate |  |  |  |  |  |  | 4.30%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FourPointThreeZeroMaturingOctoberTwentyTwentySixMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 4.30% due October 2026 | Severna Park Market Place |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Principal and interest payments |  |  |  |  |  |  | 207,000 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FourPointThreeZeroMaturingOctoberTwentyTwentySixMember / bfs_RealEstatePropertyNameAxis = bfs_SevernaParkMarketplaceMember |  |  |  |
Amortization period |  |  |  |  |  |  | 25 years |  |  |  |
Debt instrument final payment |  |  |  |  |  |  | 20,300,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FourPointThreeZeroMaturingOctoberTwentyTwentySixMember / bfs_RealEstatePropertyNameAxis = bfs_SevernaParkMarketplaceMember |  |  |  |
Amortization of principal |  |  |  |  |  |  | 950,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FourPointThreeZeroMaturingOctoberTwentyTwentySixMember / bfs_RealEstatePropertyNameAxis = bfs_SevernaParkMarketplaceMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 4.53% due November 2026 |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate |  |  |  |  |  |  | 4.53%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FourPointFiveThreeMaturingNovemberTwentyTwentySixMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 4.53% due November 2026 | Kentlands Square II |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Principal and interest payments |  |  |  |  |  |  | 240,000 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FourPointFiveThreeMaturingNovemberTwentyTwentySixMember / bfs_RealEstatePropertyNameAxis = bfs_KentlandsSquareIIMember |  |  |  |
Amortization period |  |  |  |  |  |  | 25 years |  |  |  |
Debt instrument final payment |  |  |  |  |  |  | 23,100,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FourPointFiveThreeMaturingNovemberTwentyTwentySixMember / bfs_RealEstatePropertyNameAxis = bfs_KentlandsSquareIIMember |  |  |  |
Amortization of principal |  |  |  |  |  |  | 1,042,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FourPointFiveThreeMaturingNovemberTwentyTwentySixMember / bfs_RealEstatePropertyNameAxis = bfs_KentlandsSquareIIMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 4.70% due December 2026 |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate |  |  |  |  |  |  | 4.70%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FourPointSevenZeroMaturingDecemberTwentyTwentySixMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 4.70% due December 2026 | Cranberry Square |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Principal and interest payments |  |  |  |  |  |  | 113,000 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FourPointSevenZeroMaturingDecemberTwentyTwentySixMember / bfs_RealEstatePropertyNameAxis = bfs_CranberrySquareMember |  |  |  |
Amortization period |  |  |  |  |  |  | 25 years |  |  |  |
Debt instrument final payment |  |  |  |  |  |  | 10,900,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FourPointSevenZeroMaturingDecemberTwentyTwentySixMember / bfs_RealEstatePropertyNameAxis = bfs_CranberrySquareMember |  |  |  |
Amortization of principal |  |  |  |  |  |  | 473,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FourPointSevenZeroMaturingDecemberTwentyTwentySixMember / bfs_RealEstatePropertyNameAxis = bfs_CranberrySquareMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 5.84% due May 2027 |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate |  |  |  |  |  |  | 5.84%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointEightFourMaturingMayTwentyTwentySevenMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 5.84% due May 2027 | Seven Corners |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Principal and interest payments |  |  | 463,200 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointEightFourMaturingMayTwentyTwentySevenMember / bfs_RealEstatePropertyNameAxis = bfs_SevenCornersMember |  |  |  | 463,200 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointEightFourMaturingMayTwentyTwentySevenMember / bfs_RealEstatePropertyNameAxis = bfs_SevenCornersMember |  |  |  |
Amortization period |  |  |  |  |  |  | 25 years |  |  |  |
Debt instrument final payment |  |  | 42,300,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointEightFourMaturingMayTwentyTwentySevenMember / bfs_RealEstatePropertyNameAxis = bfs_SevenCornersMember |  |  |  | 42,300,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointEightFourMaturingMayTwentyTwentySevenMember / bfs_RealEstatePropertyNameAxis = bfs_SevenCornersMember |  |  |  |
Amortization of principal |  |  |  |  |  |  | 1,500,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointEightFourMaturingMayTwentyTwentySevenMember / bfs_RealEstatePropertyNameAxis = bfs_SevenCornersMember |  |  |  |
Debt instrument amount |  |  |  |  |  |  | 73,000,000 us-gaap_DebtInstrumentFaceAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FivePointEightFourMaturingMayTwentyTwentySevenMember / bfs_RealEstatePropertyNameAxis = bfs_SevenCornersMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 4.04% due April 2028 |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate |  |  |  |  |  |  | 4.04%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FourPointZeroFourMaturingAprilTwentyTwentyEightMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 4.04% due April 2028 | Hampshire Langley |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Principal and interest payments |  |  |  |  |  |  | 95,400 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FourPointZeroFourMaturingAprilTwentyTwentyEightMember / bfs_RealEstatePropertyNameAxis = bfs_HampshireLangleyMember |  |  |  |
Amortization period |  |  |  |  |  |  | 25 years |  |  |  |
Debt instrument final payment |  |  |  |  |  |  | 9,500,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FourPointZeroFourMaturingAprilTwentyTwentyEightMember / bfs_RealEstatePropertyNameAxis = bfs_HampshireLangleyMember |  |  |  |
Amortization of principal |  |  |  |  |  |  | 437,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FourPointZeroFourMaturingAprilTwentyTwentyEightMember / bfs_RealEstatePropertyNameAxis = bfs_HampshireLangleyMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 3.51% due June 2028 |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate |  |  |  |  |  |  | 3.51%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_ThreePointFiveOneMaturingJuneTwentyTwentyEightMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 3.51% due June 2028 | Beacon Center |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Principal and interest payments |  |  |  |  |  |  | 203,200 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_ThreePointFiveOneMaturingJuneTwentyTwentyEightMember / bfs_RealEstatePropertyNameAxis = bfs_BeaconCenterMember |  |  |  |
Amortization period |  |  |  |  |  |  | 20 years |  |  |  |
Debt instrument final payment |  |  |  |  |  |  | 11,400,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_ThreePointFiveOneMaturingJuneTwentyTwentyEightMember / bfs_RealEstatePropertyNameAxis = bfs_BeaconCenterMember |  |  |  |
Amortization of principal |  |  |  |  |  |  | 1,251,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_ThreePointFiveOneMaturingJuneTwentyTwentyEightMember / bfs_RealEstatePropertyNameAxis = bfs_BeaconCenterMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 3.99% due September 2028 |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate |  |  |  |  |  |  | 3.99%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_ThreePointNineNineMaturingSeptemberTwentyTwentyEightMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 3.99% due September 2028 | Seabreeze Plaza |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Principal and interest payments |  |  |  |  |  |  | 94,900 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_ThreePointNineNineMaturingSeptemberTwentyTwentyEightMember / bfs_RealEstatePropertyNameAxis = bfs_SeabreezePlazaMember |  | 94,900 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_ThreePointNineNineMaturingSeptemberTwentyTwentyEightMember / bfs_RealEstatePropertyNameAxis = bfs_SeabreezePlazaMember |  |
Amortization period |  |  |  |  |  |  | 25 years |  | 25 years |  |
Debt instrument final payment |  |  |  |  |  |  | 9,500,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_ThreePointNineNineMaturingSeptemberTwentyTwentyEightMember / bfs_RealEstatePropertyNameAxis = bfs_SeabreezePlazaMember |  | 9,500,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_ThreePointNineNineMaturingSeptemberTwentyTwentyEightMember / bfs_RealEstatePropertyNameAxis = bfs_SeabreezePlazaMember |  |
Amortization of principal |  |  |  |  |  |  | 433,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_ThreePointNineNineMaturingSeptemberTwentyTwentyEightMember / bfs_RealEstatePropertyNameAxis = bfs_SeabreezePlazaMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 4.88% due September 2032 |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate |  |  |  |  |  |  | 4.88%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FourPointEightEightMaturingSeptemberTwentyThirtyTwoMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 4.88% due September 2032 | Park Van Ness |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Principal and interest payments |  |  |  |  |  |  | 413,500 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FourPointEightEightMaturingSeptemberTwentyThirtyTwoMember / bfs_RealEstatePropertyNameAxis = bfs_ParkVanNessMember |  |  |  |
Amortization period |  |  |  |  |  |  | 25 years |  |  |  |
Debt instrument final payment |  |  |  |  |  |  | 39,600,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FourPointEightEightMaturingSeptemberTwentyThirtyTwoMember / bfs_RealEstatePropertyNameAxis = bfs_ParkVanNessMember |  |  |  |
Debt instrument amount |  |  |  |  |  | 71,580,000 us-gaap_DebtInstrumentFaceAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FourPointEightEightMaturingSeptemberTwentyThirtyTwoMember / bfs_RealEstatePropertyNameAxis = bfs_ParkVanNessMember | 71,580,000 us-gaap_DebtInstrumentFaceAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_FourPointEightEightMaturingSeptemberTwentyThirtyTwoMember / bfs_RealEstatePropertyNameAxis = bfs_ParkVanNessMember |  |  |  |
Fixed Rate Mortgage Notes Payable | 8.00% due April 2034 |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate |  |  |  |  |  |  | 8.00%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_EightPercentdueApril2034Member |  |  |  |
Fixed Rate Mortgage Notes Payable | 8.00% due April 2034 | Olney |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Principal and interest payments |  |  |  |  |  |  | 60,400 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_EightPercentdueApril2034Member / bfs_RealEstatePropertyNameAxis = bfs_OlneyMember |  |  |  |
Debt instrument final payment |  |  |  |  |  |  | 14,700,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_EightPercentdueApril2034Member / bfs_RealEstatePropertyNameAxis = bfs_OlneyMember |  |  |  |
Amortization of principal |  |  |  |  |  |  | 119,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_EightPercentdueApril2034Member / bfs_RealEstatePropertyNameAxis = bfs_OlneyMember |  |  |  |
Fixed rate increase on note |  |  |  |  |  |  | 1.50%bfs_FixedRateIncreaseonNote / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_EightPercentdueApril2034Member / bfs_RealEstatePropertyNameAxis = bfs_OlneyMember |  |  |  |
Interest rate |  |  |  |  |  |  | 8.00%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = bfs_FixedRateMortgageNotesPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_EightPercentdueApril2034Member / bfs_RealEstatePropertyNameAxis = bfs_OlneyMember |  |  |  |
Variable Rate Loans Payable |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate spread on LIBOR |  |  |  |  |  |  | 1.53159%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1 / us-gaap_DebtInstrumentAxis = bfs_VariableRateLoansPayableMember |  |  |  |
Variable Rate Loans Payable | Revolving credit facility |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Line of credit facility, maximum borrowing capacity |  |  |  |  |  |  | 275,000,000 us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity / us-gaap_DebtInstrumentAxis = bfs_VariableRateLoansPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_UnsecuredRevolvingCreditFacilityMember |  |  |  |
Interest rate spread on LIBOR |  |  |  |  |  |  | 1.45%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1 / us-gaap_DebtInstrumentAxis = bfs_VariableRateLoansPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_UnsecuredRevolvingCreditFacilityMember |  |  |  |
Debt maturity extension period |  |  |  |  |  |  | 1 year |  |  |  |
Debt instrument fee |  |  |  |  |  |  | 0.15%bfs_DebtInstrumentFeePercentage / us-gaap_DebtInstrumentAxis = bfs_VariableRateLoansPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_UnsecuredRevolvingCreditFacilityMember |  |  |  |
Debt instrument frequency of periodic payment |  |  |  |  |  |  | Monthly |  |  |  |
Variable Rate Loans Payable | Revolving credit facility | One-month LIBOR |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate spread on LIBOR |  |  |  |  |  |  | 1.45%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1 / us-gaap_DebtInstrumentAxis = bfs_VariableRateLoansPayableMember / bfs_DebtInstrumentInterestRateByTypeAxis = bfs_OneMonthLiborMember / us-gaap_LongtermDebtTypeAxis = bfs_UnsecuredRevolvingCreditFacilityMember |  |  |  |
Variable Rate Loans Payable | Northrock loan |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate spread on LIBOR |  |  |  |  |  |  | 1.65%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1 / us-gaap_DebtInstrumentAxis = bfs_VariableRateLoansPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_NorthrockLoanMember |  |  |  |
Variable Rate Loans Payable | Northrock loan | Northrock |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Principal and interest payments |  |  |  |  |  |  | 47,000 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_DebtInstrumentAxis = bfs_VariableRateLoansPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_NorthrockLoanMember / bfs_RealEstatePropertyNameAxis = bfs_NorthrockMember |  |  |  |
Debt instrument final payment |  |  |  |  |  |  | 14,200,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_DebtInstrumentAxis = bfs_VariableRateLoansPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_NorthrockLoanMember / bfs_RealEstatePropertyNameAxis = bfs_NorthrockMember |  |  |  |
Amortization of principal |  |  |  |  |  |  | 277,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear / us-gaap_DebtInstrumentAxis = bfs_VariableRateLoansPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_NorthrockLoanMember / bfs_RealEstatePropertyNameAxis = bfs_NorthrockMember |  |  |  |
Variable Rate Loans Payable | Metro Pike Center bank loan |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate spread on LIBOR |  |  |  |  |  |  | 1.65%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1 / us-gaap_DebtInstrumentAxis = bfs_VariableRateLoansPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_MetroPikeCenterBankLoanMember |  |  |  |
Variable Rate Loans Payable | Metro Pike Center bank loan | Metro Pike Center |  |  |  |  |  |  |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |
Principal and interest payments |  |  |  |  |  |  | 48,000 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_DebtInstrumentAxis = bfs_VariableRateLoansPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_MetroPikeCenterBankLoanMember / bfs_RealEstatePropertyNameAxis = bfs_MetroPikeCenterMember |  |  |  |
Debt instrument final payment |  |  |  |  |  |  | 14,800,000 bfs_DebtInstrumentFinalPaymentAmount / us-gaap_DebtInstrumentAxis = bfs_VariableRateLoansPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_MetroPikeCenterBankLoanMember / bfs_RealEstatePropertyNameAxis = bfs_MetroPikeCenterMember |  |  |  |
Amortization of principal |  |  |  |  |  |  | $ 288,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear / us-gaap_DebtInstrumentAxis = bfs_VariableRateLoansPayableMember / us-gaap_LongtermDebtTypeAxis = bfs_MetroPikeCenterBankLoanMember / bfs_RealEstatePropertyNameAxis = bfs_MetroPikeCenterMember |  |  |  |
[1] | Interest rate and scheduled maturity data presented as of December 31, 2014. Totals computed using weighted averages.

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