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Stock Option Plan - Stock Options Issued (Detail) (USD $) | 12 Months Ended
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Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Total grant (in shares) | 1,362,500 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalGrantsInPeriodGross |  |
Vested (in shares) | 716,250 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedInPeriod |  |
Exercised (in shares) | 301,792 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalExercisesInPeriod |  |
Forfeited (in shares) | 312,500 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod |  |
Exercisable at December 31 (in shares) | 380,708 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber | 413,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber | 377,715 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber
Remaining unexercised (in shares) | 748,208 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsRemainingUnexercisedNumber |  |
Exercise price (in usd per share) | $ 37.71 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice | $ 33.15 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice | $ 31.03 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice
Total value at grant date | $ 9,596,150 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodFairValue |  |
Estimated forfeitures | 1,823,557 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeitedInPeriodFairValue |  |
Expensed in previous years | 3,404,622 bfs_AllocatedShareBasedCompensationExpenseInPreviousYears |  |
Future expense | 1,891,071 bfs_EmployeeAndNonEmployeeServiceSharebasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions |  |
Expensed in 2012 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 632,365 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodOneMember |  |
Expensed in 2013 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 879,710 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodTwoMember |  |
Expensed in 2014 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 964,825 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodThreeMember |  |
Directors |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 112,900 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember | 124,400 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember | 110,000 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember
Directors | 5/6/2005 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Grant date | May 06, 2005 |  |
Total grant (in shares) | 30,000 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalGrantsInPeriodGross / bfs_PeriodAxis = bfs_MaySixTwoThousandFiveMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Vested (in shares) | 30,000 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedInPeriod / bfs_PeriodAxis = bfs_MaySixTwoThousandFiveMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Exercised (in shares) | 22,500 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalExercisesInPeriod / bfs_PeriodAxis = bfs_MaySixTwoThousandFiveMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Forfeited (in shares) | 0 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod / bfs_PeriodAxis = bfs_MaySixTwoThousandFiveMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Exercisable at December 31 (in shares) | 7,500 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber / bfs_PeriodAxis = bfs_MaySixTwoThousandFiveMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Remaining unexercised (in shares) | 7,500 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsRemainingUnexercisedNumber / bfs_PeriodAxis = bfs_MaySixTwoThousandFiveMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Exercise price (in usd per share) | $ 33.22 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice / bfs_PeriodAxis = bfs_MaySixTwoThousandFiveMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Volatility | 0.198 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsVolatility / bfs_PeriodAxis = bfs_MaySixTwoThousandFiveMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Expected life (years) | 10 years |  |
Assumed yield | 6.91%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate / bfs_PeriodAxis = bfs_MaySixTwoThousandFiveMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Risk-free rate | 4.28%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate / bfs_PeriodAxis = bfs_MaySixTwoThousandFiveMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Total value at grant date | 71,100 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodFairValue / bfs_PeriodAxis = bfs_MaySixTwoThousandFiveMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Expensed in previous years | 71,100 bfs_AllocatedShareBasedCompensationExpenseInPreviousYears / bfs_PeriodAxis = bfs_MaySixTwoThousandFiveMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Future expense | 0 bfs_EmployeeAndNonEmployeeServiceSharebasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions / bfs_PeriodAxis = bfs_MaySixTwoThousandFiveMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 5/6/2005 | Expensed in 2012 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 0 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodOneMember / bfs_PeriodAxis = bfs_MaySixTwoThousandFiveMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 5/6/2005 | Expensed in 2013 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 0 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodTwoMember / bfs_PeriodAxis = bfs_MaySixTwoThousandFiveMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 5/6/2005 | Expensed in 2014 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 0 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodThreeMember / bfs_PeriodAxis = bfs_MaySixTwoThousandFiveMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 5/1/2006 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Grant date | May 01, 2006 |  |
Total grant (in shares) | 30,000 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalGrantsInPeriodGross / bfs_PeriodAxis = bfs_MayOneTwoThousandSixMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Vested (in shares) | 30,000 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedInPeriod / bfs_PeriodAxis = bfs_MayOneTwoThousandSixMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Exercised (in shares) | 10,000 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalExercisesInPeriod / bfs_PeriodAxis = bfs_MayOneTwoThousandSixMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Forfeited (in shares) | 2,500 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod / bfs_PeriodAxis = bfs_MayOneTwoThousandSixMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Exercisable at December 31 (in shares) | 17,500 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber / bfs_PeriodAxis = bfs_MayOneTwoThousandSixMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Remaining unexercised (in shares) | 17,500 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsRemainingUnexercisedNumber / bfs_PeriodAxis = bfs_MayOneTwoThousandSixMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Exercise price (in usd per share) | $ 40.35 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice / bfs_PeriodAxis = bfs_MayOneTwoThousandSixMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Volatility | 0.206 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsVolatility / bfs_PeriodAxis = bfs_MayOneTwoThousandSixMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Expected life (years) | 9 years |  |
Assumed yield | 5.93%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate / bfs_PeriodAxis = bfs_MayOneTwoThousandSixMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Risk-free rate | 5.11%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate / bfs_PeriodAxis = bfs_MayOneTwoThousandSixMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Total value at grant date | 143,400 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodFairValue / bfs_PeriodAxis = bfs_MayOneTwoThousandSixMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Expensed in previous years | 143,400 bfs_AllocatedShareBasedCompensationExpenseInPreviousYears / bfs_PeriodAxis = bfs_MayOneTwoThousandSixMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Future expense | 0 bfs_EmployeeAndNonEmployeeServiceSharebasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions / bfs_PeriodAxis = bfs_MayOneTwoThousandSixMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 5/1/2006 | Expensed in 2012 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 0 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodOneMember / bfs_PeriodAxis = bfs_MayOneTwoThousandSixMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 5/1/2006 | Expensed in 2013 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 0 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodTwoMember / bfs_PeriodAxis = bfs_MayOneTwoThousandSixMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 5/1/2006 | Expensed in 2014 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 0 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodThreeMember / bfs_PeriodAxis = bfs_MayOneTwoThousandSixMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 4/27/2007 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Grant date | Apr. 27, 2007 |  |
Total grant (in shares) | 30,000 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalGrantsInPeriodGross / bfs_PeriodAxis = bfs_AprilTwentySevenTwoThousandSevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Vested (in shares) | 30,000 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedInPeriod / bfs_PeriodAxis = bfs_AprilTwentySevenTwoThousandSevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Exercised (in shares) | 0 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalExercisesInPeriod / bfs_PeriodAxis = bfs_AprilTwentySevenTwoThousandSevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Forfeited (in shares) | 7,500 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod / bfs_PeriodAxis = bfs_AprilTwentySevenTwoThousandSevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Exercisable at December 31 (in shares) | 22,500 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber / bfs_PeriodAxis = bfs_AprilTwentySevenTwoThousandSevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Remaining unexercised (in shares) | 22,500 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsRemainingUnexercisedNumber / bfs_PeriodAxis = bfs_AprilTwentySevenTwoThousandSevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Exercise price (in usd per share) | $ 54.17 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice / bfs_PeriodAxis = bfs_AprilTwentySevenTwoThousandSevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Volatility | 0.225 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsVolatility / bfs_PeriodAxis = bfs_AprilTwentySevenTwoThousandSevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Expected life (years) | 8 years |  |
Assumed yield | 4.39%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate / bfs_PeriodAxis = bfs_AprilTwentySevenTwoThousandSevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Risk-free rate | 4.65%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate / bfs_PeriodAxis = bfs_AprilTwentySevenTwoThousandSevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Total value at grant date | 285,300 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodFairValue / bfs_PeriodAxis = bfs_AprilTwentySevenTwoThousandSevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Expensed in previous years | 285,300 bfs_AllocatedShareBasedCompensationExpenseInPreviousYears / bfs_PeriodAxis = bfs_AprilTwentySevenTwoThousandSevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Future expense | 0 bfs_EmployeeAndNonEmployeeServiceSharebasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions / bfs_PeriodAxis = bfs_AprilTwentySevenTwoThousandSevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 4/27/2007 | Expensed in 2012 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 0 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodOneMember / bfs_PeriodAxis = bfs_AprilTwentySevenTwoThousandSevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 4/27/2007 | Expensed in 2013 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 0 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodTwoMember / bfs_PeriodAxis = bfs_AprilTwentySevenTwoThousandSevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 4/27/2007 | Expensed in 2014 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 0 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodThreeMember / bfs_PeriodAxis = bfs_AprilTwentySevenTwoThousandSevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 4/25/2008 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Grant date | Apr. 25, 2008 |  |
Total grant (in shares) | 30,000 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalGrantsInPeriodGross / bfs_PeriodAxis = bfs_AprilTwentyFiveTwoThousandEightMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Vested (in shares) | 30,000 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedInPeriod / bfs_PeriodAxis = bfs_AprilTwentyFiveTwoThousandEightMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Exercised (in shares) | 0 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalExercisesInPeriod / bfs_PeriodAxis = bfs_AprilTwentyFiveTwoThousandEightMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Forfeited (in shares) | 7,500 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod / bfs_PeriodAxis = bfs_AprilTwentyFiveTwoThousandEightMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Exercisable at December 31 (in shares) | 22,500 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber / bfs_PeriodAxis = bfs_AprilTwentyFiveTwoThousandEightMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Remaining unexercised (in shares) | 22,500 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsRemainingUnexercisedNumber / bfs_PeriodAxis = bfs_AprilTwentyFiveTwoThousandEightMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Exercise price (in usd per share) | $ 50.15 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice / bfs_PeriodAxis = bfs_AprilTwentyFiveTwoThousandEightMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Volatility | 0.237 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsVolatility / bfs_PeriodAxis = bfs_AprilTwentyFiveTwoThousandEightMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Expected life (years) | 7 years |  |
Assumed yield | 4.09%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate / bfs_PeriodAxis = bfs_AprilTwentyFiveTwoThousandEightMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Risk-free rate | 3.49%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate / bfs_PeriodAxis = bfs_AprilTwentyFiveTwoThousandEightMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Total value at grant date | 254,700 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodFairValue / bfs_PeriodAxis = bfs_AprilTwentyFiveTwoThousandEightMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Expensed in previous years | 254,700 bfs_AllocatedShareBasedCompensationExpenseInPreviousYears / bfs_PeriodAxis = bfs_AprilTwentyFiveTwoThousandEightMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Future expense | 0 bfs_EmployeeAndNonEmployeeServiceSharebasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions / bfs_PeriodAxis = bfs_AprilTwentyFiveTwoThousandEightMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 4/25/2008 | Expensed in 2012 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 0 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodOneMember / bfs_PeriodAxis = bfs_AprilTwentyFiveTwoThousandEightMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 4/25/2008 | Expensed in 2013 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 0 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodTwoMember / bfs_PeriodAxis = bfs_AprilTwentyFiveTwoThousandEightMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 4/25/2008 | Expensed in 2014 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 0 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodThreeMember / bfs_PeriodAxis = bfs_AprilTwentyFiveTwoThousandEightMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 4/24/2009 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Grant date | Apr. 24, 2009 |  |
Total grant (in shares) | 32,500 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalGrantsInPeriodGross / bfs_PeriodAxis = bfs_AprilFourTwoThousandNineMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Vested (in shares) | 32,500 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedInPeriod / bfs_PeriodAxis = bfs_AprilFourTwoThousandNineMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Exercised (in shares) | 20,000 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalExercisesInPeriod / bfs_PeriodAxis = bfs_AprilFourTwoThousandNineMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Forfeited (in shares) | 0 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod / bfs_PeriodAxis = bfs_AprilFourTwoThousandNineMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Exercisable at December 31 (in shares) | 12,500 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber / bfs_PeriodAxis = bfs_AprilFourTwoThousandNineMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Remaining unexercised (in shares) | 12,500 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsRemainingUnexercisedNumber / bfs_PeriodAxis = bfs_AprilFourTwoThousandNineMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Exercise price (in usd per share) | $ 32.68 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice / bfs_PeriodAxis = bfs_AprilFourTwoThousandNineMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Volatility | 0.344 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsVolatility / bfs_PeriodAxis = bfs_AprilFourTwoThousandNineMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Expected life (years) | 6 years |  |
Assumed yield | 4.54%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate / bfs_PeriodAxis = bfs_AprilFourTwoThousandNineMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Risk-free rate | 2.19%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate / bfs_PeriodAxis = bfs_AprilFourTwoThousandNineMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Total value at grant date | 222,950 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodFairValue / bfs_PeriodAxis = bfs_AprilFourTwoThousandNineMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Expensed in previous years | 222,950 bfs_AllocatedShareBasedCompensationExpenseInPreviousYears / bfs_PeriodAxis = bfs_AprilFourTwoThousandNineMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Future expense | 0 bfs_EmployeeAndNonEmployeeServiceSharebasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions / bfs_PeriodAxis = bfs_AprilFourTwoThousandNineMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 4/24/2009 | Expensed in 2012 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 0 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodOneMember / bfs_PeriodAxis = bfs_AprilFourTwoThousandNineMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 4/24/2009 | Expensed in 2013 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 0 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodTwoMember / bfs_PeriodAxis = bfs_AprilFourTwoThousandNineMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 4/24/2009 | Expensed in 2014 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 0 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodThreeMember / bfs_PeriodAxis = bfs_AprilFourTwoThousandNineMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 5/7/2010 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Grant date | May 07, 2010 |  |
Total grant (in shares) | 32,500 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalGrantsInPeriodGross / bfs_PeriodAxis = bfs_MaySevenTwoThousandTenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Vested (in shares) | 32,500 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedInPeriod / bfs_PeriodAxis = bfs_MaySevenTwoThousandTenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Exercised (in shares) | 10,000 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalExercisesInPeriod / bfs_PeriodAxis = bfs_MaySevenTwoThousandTenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Forfeited (in shares) | 2,500 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod / bfs_PeriodAxis = bfs_MaySevenTwoThousandTenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Exercisable at December 31 (in shares) | 20,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber / bfs_PeriodAxis = bfs_MaySevenTwoThousandTenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Remaining unexercised (in shares) | 20,000 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsRemainingUnexercisedNumber / bfs_PeriodAxis = bfs_MaySevenTwoThousandTenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Exercise price (in usd per share) | $ 38.76 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice / bfs_PeriodAxis = bfs_MaySevenTwoThousandTenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Volatility | 0.369 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsVolatility / bfs_PeriodAxis = bfs_MaySevenTwoThousandTenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Expected life (years) | 5 years |  |
Assumed yield | 4.23%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate / bfs_PeriodAxis = bfs_MaySevenTwoThousandTenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Risk-free rate | 2.17%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate / bfs_PeriodAxis = bfs_MaySevenTwoThousandTenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Total value at grant date | 287,950 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodFairValue / bfs_PeriodAxis = bfs_MaySevenTwoThousandTenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Expensed in previous years | 287,950 bfs_AllocatedShareBasedCompensationExpenseInPreviousYears / bfs_PeriodAxis = bfs_MaySevenTwoThousandTenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Future expense | 0 bfs_EmployeeAndNonEmployeeServiceSharebasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions / bfs_PeriodAxis = bfs_MaySevenTwoThousandTenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 5/7/2010 | Expensed in 2012 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 0 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodOneMember / bfs_PeriodAxis = bfs_MaySevenTwoThousandTenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 5/7/2010 | Expensed in 2013 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 0 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodTwoMember / bfs_PeriodAxis = bfs_MaySevenTwoThousandTenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 5/7/2010 | Expensed in 2014 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 0 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodThreeMember / bfs_PeriodAxis = bfs_MaySevenTwoThousandTenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 5/13/2011 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Grant date | May 13, 2011 |  |
Total grant (in shares) | 32,500 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalGrantsInPeriodGross / bfs_PeriodAxis = bfs_MayThirteenTwoThousandElevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Vested (in shares) | 32,500 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedInPeriod / bfs_PeriodAxis = bfs_MayThirteenTwoThousandElevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Exercised (in shares) | 10,000 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalExercisesInPeriod / bfs_PeriodAxis = bfs_MayThirteenTwoThousandElevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Forfeited (in shares) | 2,500 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod / bfs_PeriodAxis = bfs_MayThirteenTwoThousandElevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Exercisable at December 31 (in shares) | 20,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber / bfs_PeriodAxis = bfs_MayThirteenTwoThousandElevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Remaining unexercised (in shares) | 20,000 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsRemainingUnexercisedNumber / bfs_PeriodAxis = bfs_MayThirteenTwoThousandElevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Exercise price (in usd per share) | $ 41.82 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice / bfs_PeriodAxis = bfs_MayThirteenTwoThousandElevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Volatility | 0.358 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsVolatility / bfs_PeriodAxis = bfs_MayThirteenTwoThousandElevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Expected life (years) | 5 years |  |
Assumed yield | 4.16%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate / bfs_PeriodAxis = bfs_MayThirteenTwoThousandElevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Risk-free rate | 1.86%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate / bfs_PeriodAxis = bfs_MayThirteenTwoThousandElevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Total value at grant date | 297,375 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodFairValue / bfs_PeriodAxis = bfs_MayThirteenTwoThousandElevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Expensed in previous years | 297,375 bfs_AllocatedShareBasedCompensationExpenseInPreviousYears / bfs_PeriodAxis = bfs_MayThirteenTwoThousandElevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Future expense | 0 bfs_EmployeeAndNonEmployeeServiceSharebasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions / bfs_PeriodAxis = bfs_MayThirteenTwoThousandElevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 5/13/2011 | Expensed in 2012 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 0 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodOneMember / bfs_PeriodAxis = bfs_MayThirteenTwoThousandElevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 5/13/2011 | Expensed in 2013 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 0 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodTwoMember / bfs_PeriodAxis = bfs_MayThirteenTwoThousandElevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 5/13/2011 | Expensed in 2014 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 0 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodThreeMember / bfs_PeriodAxis = bfs_MayThirteenTwoThousandElevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 5/4/2012 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Grant date | May 04, 2012 |  |
Total grant (in shares) | 35,000 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalGrantsInPeriodGross / bfs_PeriodAxis = bfs_MayFourTwoThousandTwelveMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Vested (in shares) | 35,000 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedInPeriod / bfs_PeriodAxis = bfs_MayFourTwoThousandTwelveMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Exercised (in shares) | 10,000 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalExercisesInPeriod / bfs_PeriodAxis = bfs_MayFourTwoThousandTwelveMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Forfeited (in shares) | 0 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod / bfs_PeriodAxis = bfs_MayFourTwoThousandTwelveMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Exercisable at December 31 (in shares) | 25,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber / bfs_PeriodAxis = bfs_MayFourTwoThousandTwelveMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Remaining unexercised (in shares) | 25,000 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsRemainingUnexercisedNumber / bfs_PeriodAxis = bfs_MayFourTwoThousandTwelveMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Exercise price (in usd per share) | $ 39.29 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice / bfs_PeriodAxis = bfs_MayFourTwoThousandTwelveMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Volatility | 0.348 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsVolatility / bfs_PeriodAxis = bfs_MayFourTwoThousandTwelveMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Expected life (years) | 5 years |  |
Assumed yield | 4.61%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate / bfs_PeriodAxis = bfs_MayFourTwoThousandTwelveMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Risk-free rate | 0.78%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate / bfs_PeriodAxis = bfs_MayFourTwoThousandTwelveMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Total value at grant date | 257,250 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodFairValue / bfs_PeriodAxis = bfs_MayFourTwoThousandTwelveMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Expensed in previous years | 0 bfs_AllocatedShareBasedCompensationExpenseInPreviousYears / bfs_PeriodAxis = bfs_MayFourTwoThousandTwelveMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Future expense | 0 bfs_EmployeeAndNonEmployeeServiceSharebasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions / bfs_PeriodAxis = bfs_MayFourTwoThousandTwelveMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 5/4/2012 | Expensed in 2012 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 257,250 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodOneMember / bfs_PeriodAxis = bfs_MayFourTwoThousandTwelveMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 5/4/2012 | Expensed in 2013 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 0 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodTwoMember / bfs_PeriodAxis = bfs_MayFourTwoThousandTwelveMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 5/4/2012 | Expensed in 2014 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 0 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodThreeMember / bfs_PeriodAxis = bfs_MayFourTwoThousandTwelveMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 5/10/2013 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Grant date | May 10, 2013 |  |
Total grant (in shares) | 35,000 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalGrantsInPeriodGross / bfs_PeriodAxis = bfs_MayTenTwoThousandThirteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Vested (in shares) | 35,000 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedInPeriod / bfs_PeriodAxis = bfs_MayTenTwoThousandThirteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Exercised (in shares) | 7,500 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalExercisesInPeriod / bfs_PeriodAxis = bfs_MayTenTwoThousandThirteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Forfeited (in shares) | 0 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod / bfs_PeriodAxis = bfs_MayTenTwoThousandThirteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Exercisable at December 31 (in shares) | 27,500 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber / bfs_PeriodAxis = bfs_MayTenTwoThousandThirteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Remaining unexercised (in shares) | 27,500 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsRemainingUnexercisedNumber / bfs_PeriodAxis = bfs_MayTenTwoThousandThirteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Exercise price (in usd per share) | $ 44.42 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice / bfs_PeriodAxis = bfs_MayTenTwoThousandThirteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Volatility | 0.333 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsVolatility / bfs_PeriodAxis = bfs_MayTenTwoThousandThirteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Expected life (years) | 5 years |  |
Assumed yield | 4.53%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate / bfs_PeriodAxis = bfs_MayTenTwoThousandThirteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Risk-free rate | 0.82%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate / bfs_PeriodAxis = bfs_MayTenTwoThousandThirteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Total value at grant date | 278,250 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodFairValue / bfs_PeriodAxis = bfs_MayTenTwoThousandThirteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Expensed in previous years | 0 bfs_AllocatedShareBasedCompensationExpenseInPreviousYears / bfs_PeriodAxis = bfs_MayTenTwoThousandThirteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Future expense | 0 bfs_EmployeeAndNonEmployeeServiceSharebasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions / bfs_PeriodAxis = bfs_MayTenTwoThousandThirteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 5/10/2013 | Expensed in 2012 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 0 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodOneMember / bfs_PeriodAxis = bfs_MayTenTwoThousandThirteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 5/10/2013 | Expensed in 2013 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 278,250 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodTwoMember / bfs_PeriodAxis = bfs_MayTenTwoThousandThirteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 5/10/2013 | Expensed in 2014 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 0 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodThreeMember / bfs_PeriodAxis = bfs_MayTenTwoThousandThirteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 5/9/2014 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Grant date | May 09, 2014 |  |
Total grant (in shares) | 30,000 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalGrantsInPeriodGross / bfs_PeriodAxis = bfs_MayNineTwoThousandFourteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Vested (in shares) | 30,000 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedInPeriod / bfs_PeriodAxis = bfs_MayNineTwoThousandFourteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Exercised (in shares) | 0 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalExercisesInPeriod / bfs_PeriodAxis = bfs_MayNineTwoThousandFourteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Forfeited (in shares) | 0 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod / bfs_PeriodAxis = bfs_MayNineTwoThousandFourteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Exercisable at December 31 (in shares) | 30,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber / bfs_PeriodAxis = bfs_MayNineTwoThousandFourteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Remaining unexercised (in shares) | 30,000 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsRemainingUnexercisedNumber / bfs_PeriodAxis = bfs_MayNineTwoThousandFourteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Exercise price (in usd per share) | $ 47.03 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice / bfs_PeriodAxis = bfs_MayNineTwoThousandFourteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Volatility | 0.173 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsVolatility / bfs_PeriodAxis = bfs_MayNineTwoThousandFourteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Expected life (years) | 5 years |  |
Assumed yield | 4.48%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate / bfs_PeriodAxis = bfs_MayNineTwoThousandFourteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Risk-free rate | 1.63%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate / bfs_PeriodAxis = bfs_MayNineTwoThousandFourteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Total value at grant date | 109,500 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodFairValue / bfs_PeriodAxis = bfs_MayNineTwoThousandFourteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Expensed in previous years | 0 bfs_AllocatedShareBasedCompensationExpenseInPreviousYears / bfs_PeriodAxis = bfs_MayNineTwoThousandFourteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Future expense | 0 bfs_EmployeeAndNonEmployeeServiceSharebasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions / bfs_PeriodAxis = bfs_MayNineTwoThousandFourteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 5/9/2014 | Expensed in 2012 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 0 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodOneMember / bfs_PeriodAxis = bfs_MayNineTwoThousandFourteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 5/9/2014 | Expensed in 2013 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 0 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodTwoMember / bfs_PeriodAxis = bfs_MayNineTwoThousandFourteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | 5/9/2014 | Expensed in 2014 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 109,500 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodThreeMember / bfs_PeriodAxis = bfs_MayNineTwoThousandFourteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | Subtotals |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Total grant (in shares) | 317,500 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalGrantsInPeriodGross / bfs_PeriodAxis = bfs_SubtotalMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Vested (in shares) | 317,500 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedInPeriod / bfs_PeriodAxis = bfs_SubtotalMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Exercised (in shares) | 90,000 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalExercisesInPeriod / bfs_PeriodAxis = bfs_SubtotalMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Forfeited (in shares) | 22,500 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod / bfs_PeriodAxis = bfs_SubtotalMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Exercisable at December 31 (in shares) | 205,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber / bfs_PeriodAxis = bfs_SubtotalMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Remaining unexercised (in shares) | 205,000 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsRemainingUnexercisedNumber / bfs_PeriodAxis = bfs_SubtotalMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Total value at grant date | 2,207,775 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodFairValue / bfs_PeriodAxis = bfs_SubtotalMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Expensed in previous years | 1,562,775 bfs_AllocatedShareBasedCompensationExpenseInPreviousYears / bfs_PeriodAxis = bfs_SubtotalMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Future expense | 0 bfs_EmployeeAndNonEmployeeServiceSharebasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions / bfs_PeriodAxis = bfs_SubtotalMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | Subtotals | Expensed in 2012 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 257,250 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodOneMember / bfs_PeriodAxis = bfs_SubtotalMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | Subtotals | Expensed in 2013 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 278,250 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodTwoMember / bfs_PeriodAxis = bfs_SubtotalMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Directors | Subtotals | Expensed in 2014 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 109,500 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodThreeMember / bfs_PeriodAxis = bfs_SubtotalMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Officers | 5/6/2005 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Grant date | May 06, 2005 |  |
Total grant (in shares) | 132,500 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalGrantsInPeriodGross / bfs_PeriodAxis = bfs_MaySixTwoThousandFiveMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Vested (in shares) | 118,750 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedInPeriod / bfs_PeriodAxis = bfs_MaySixTwoThousandFiveMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Exercised (in shares) | 115,750 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalExercisesInPeriod / bfs_PeriodAxis = bfs_MaySixTwoThousandFiveMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Forfeited (in shares) | 13,750 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod / bfs_PeriodAxis = bfs_MaySixTwoThousandFiveMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Exercisable at December 31 (in shares) | 3,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber / bfs_PeriodAxis = bfs_MaySixTwoThousandFiveMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Remaining unexercised (in shares) | 3,000 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsRemainingUnexercisedNumber / bfs_PeriodAxis = bfs_MaySixTwoThousandFiveMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Exercise price (in usd per share) | $ 33.22 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice / bfs_PeriodAxis = bfs_MaySixTwoThousandFiveMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Volatility | 0.207 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsVolatility / bfs_PeriodAxis = bfs_MaySixTwoThousandFiveMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Expected life (years) | 8 years |  |
Assumed yield | 6.37%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate / bfs_PeriodAxis = bfs_MaySixTwoThousandFiveMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Risk-free rate | 4.15%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate / bfs_PeriodAxis = bfs_MaySixTwoThousandFiveMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Total value at grant date | 413,400 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodFairValue / bfs_PeriodAxis = bfs_MaySixTwoThousandFiveMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Estimated forfeitures | 35,100 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeitedInPeriodFairValue / bfs_PeriodAxis = bfs_MaySixTwoThousandFiveMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Expensed in previous years | 378,300 bfs_AllocatedShareBasedCompensationExpenseInPreviousYears / bfs_PeriodAxis = bfs_MaySixTwoThousandFiveMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Future expense | 0 bfs_EmployeeAndNonEmployeeServiceSharebasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions / bfs_PeriodAxis = bfs_MaySixTwoThousandFiveMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Officers | 5/6/2005 | Expensed in 2014 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 0 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodThreeMember / bfs_PeriodAxis = bfs_MaySixTwoThousandFiveMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Officers | 4/27/2007 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Grant date | Apr. 27, 2007 |  |
Total grant (in shares) | 135,000 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalGrantsInPeriodGross / bfs_PeriodAxis = bfs_AprilTwentySevenTwoThousandSevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Vested (in shares) | 67,500 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedInPeriod / bfs_PeriodAxis = bfs_AprilTwentySevenTwoThousandSevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Exercised (in shares) | 3,528 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalExercisesInPeriod / bfs_PeriodAxis = bfs_AprilTwentySevenTwoThousandSevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Forfeited (in shares) | 67,500 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod / bfs_PeriodAxis = bfs_AprilTwentySevenTwoThousandSevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Exercisable at December 31 (in shares) | 63,972 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber / bfs_PeriodAxis = bfs_AprilTwentySevenTwoThousandSevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Remaining unexercised (in shares) | 63,972 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsRemainingUnexercisedNumber / bfs_PeriodAxis = bfs_AprilTwentySevenTwoThousandSevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Exercise price (in usd per share) | $ 54.17 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice / bfs_PeriodAxis = bfs_AprilTwentySevenTwoThousandSevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Volatility | 0.233 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsVolatility / bfs_PeriodAxis = bfs_AprilTwentySevenTwoThousandSevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Expected life (years) | 6 years 6 months |  |
Assumed yield | 4.13%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate / bfs_PeriodAxis = bfs_AprilTwentySevenTwoThousandSevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Risk-free rate | 4.61%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate / bfs_PeriodAxis = bfs_AprilTwentySevenTwoThousandSevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Total value at grant date | 1,339,200 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodFairValue / bfs_PeriodAxis = bfs_AprilTwentySevenTwoThousandSevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Estimated forfeitures | 62,000 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeitedInPeriodFairValue / bfs_PeriodAxis = bfs_AprilTwentySevenTwoThousandSevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Expensed in previous years | 1,277,200 bfs_AllocatedShareBasedCompensationExpenseInPreviousYears / bfs_PeriodAxis = bfs_AprilTwentySevenTwoThousandSevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Future expense | 0 bfs_EmployeeAndNonEmployeeServiceSharebasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions / bfs_PeriodAxis = bfs_AprilTwentySevenTwoThousandSevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Weighted average term of remaining future expense | 2 years 8 months 3 days |  |
Officers | 4/27/2007 | Expensed in 2012 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 0 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodOneMember / bfs_PeriodAxis = bfs_AprilTwentySevenTwoThousandSevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Officers | 4/27/2007 | Expensed in 2013 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 0 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodTwoMember / bfs_PeriodAxis = bfs_AprilTwentySevenTwoThousandSevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Officers | 4/27/2007 | Expensed in 2014 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 0 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodThreeMember / bfs_PeriodAxis = bfs_AprilTwentySevenTwoThousandSevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Officers | 5/13/2011 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Grant date | May 13, 2011 |  |
Total grant (in shares) | 162,500 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalGrantsInPeriodGross / bfs_PeriodAxis = bfs_MayThirteenTwoThousandElevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Vested (in shares) | 105,625 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedInPeriod / bfs_PeriodAxis = bfs_MayThirteenTwoThousandElevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Exercised (in shares) | 46,889 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalExercisesInPeriod / bfs_PeriodAxis = bfs_MayThirteenTwoThousandElevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Forfeited (in shares) | 43,750 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod / bfs_PeriodAxis = bfs_MayThirteenTwoThousandElevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Exercisable at December 31 (in shares) | 47,486 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber / bfs_PeriodAxis = bfs_MayThirteenTwoThousandElevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Remaining unexercised (in shares) | 71,861 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsRemainingUnexercisedNumber / bfs_PeriodAxis = bfs_MayThirteenTwoThousandElevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Exercise price (in usd per share) | $ 41.82 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice / bfs_PeriodAxis = bfs_MayThirteenTwoThousandElevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Volatility | 0.330 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsVolatility / bfs_PeriodAxis = bfs_MayThirteenTwoThousandElevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Expected life (years) | 8 years |  |
Assumed yield | 4.81%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate / bfs_PeriodAxis = bfs_MayThirteenTwoThousandElevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Risk-free rate | 2.75%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate / bfs_PeriodAxis = bfs_MayThirteenTwoThousandElevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Total value at grant date | 1,366,625 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodFairValue / bfs_PeriodAxis = bfs_MayThirteenTwoThousandElevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Estimated forfeitures | 387,550 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeitedInPeriodFairValue / bfs_PeriodAxis = bfs_MayThirteenTwoThousandElevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Expensed in previous years | 186,347 bfs_AllocatedShareBasedCompensationExpenseInPreviousYears / bfs_PeriodAxis = bfs_MayThirteenTwoThousandElevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Future expense | 69,512 bfs_EmployeeAndNonEmployeeServiceSharebasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions / bfs_PeriodAxis = bfs_MayThirteenTwoThousandElevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Officers | 5/13/2011 | Expensed in 2012 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 270,391 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodOneMember / bfs_PeriodAxis = bfs_MayThirteenTwoThousandElevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Officers | 5/13/2011 | Expensed in 2013 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 235,350 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodTwoMember / bfs_PeriodAxis = bfs_MayThirteenTwoThousandElevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Officers | 5/13/2011 | Expensed in 2014 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 217,475 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodThreeMember / bfs_PeriodAxis = bfs_MayThirteenTwoThousandElevenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Officers | 5/4/2012 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Grant date | May 04, 2012 |  |
Total grant (in shares) | 242,500 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalGrantsInPeriodGross / bfs_PeriodAxis = bfs_MayFourTwoThousandTwelveMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Vested (in shares) | 56,250 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedInPeriod / bfs_PeriodAxis = bfs_MayFourTwoThousandTwelveMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Exercised (in shares) | 30,000 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalExercisesInPeriod / bfs_PeriodAxis = bfs_MayFourTwoThousandTwelveMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Forfeited (in shares) | 135,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod / bfs_PeriodAxis = bfs_MayFourTwoThousandTwelveMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Exercisable at December 31 (in shares) | 26,250 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber / bfs_PeriodAxis = bfs_MayFourTwoThousandTwelveMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Remaining unexercised (in shares) | 77,500 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsRemainingUnexercisedNumber / bfs_PeriodAxis = bfs_MayFourTwoThousandTwelveMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Exercise price (in usd per share) | $ 39.29 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice / bfs_PeriodAxis = bfs_MayFourTwoThousandTwelveMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Volatility | 0.315 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsVolatility / bfs_PeriodAxis = bfs_MayFourTwoThousandTwelveMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Expected life (years) | 8 years |  |
Assumed yield | 5.28%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate / bfs_PeriodAxis = bfs_MayFourTwoThousandTwelveMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Risk-free rate | 1.49%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate / bfs_PeriodAxis = bfs_MayFourTwoThousandTwelveMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Total value at grant date | 1,518,050 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodFairValue / bfs_PeriodAxis = bfs_MayFourTwoThousandTwelveMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Estimated forfeitures | 889,690 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeitedInPeriodFairValue / bfs_PeriodAxis = bfs_MayFourTwoThousandTwelveMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Expensed in previous years | 0 bfs_AllocatedShareBasedCompensationExpenseInPreviousYears / bfs_PeriodAxis = bfs_MayFourTwoThousandTwelveMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Future expense | 209,461 bfs_EmployeeAndNonEmployeeServiceSharebasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions / bfs_PeriodAxis = bfs_MayFourTwoThousandTwelveMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Officers | 5/4/2012 | Expensed in 2012 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 104,724 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodOneMember / bfs_PeriodAxis = bfs_MayFourTwoThousandTwelveMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Officers | 5/4/2012 | Expensed in 2013 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 157,083 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodTwoMember / bfs_PeriodAxis = bfs_MayFourTwoThousandTwelveMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Officers | 5/4/2012 | Expensed in 2014 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 157,092 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodThreeMember / bfs_PeriodAxis = bfs_MayFourTwoThousandTwelveMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Officers | 5/10/2013 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Grant date | May 10, 2013 |  |
Total grant (in shares) | 202,500 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalGrantsInPeriodGross / bfs_PeriodAxis = bfs_MayTenTwoThousandThirteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Vested (in shares) | 50,625 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedInPeriod / bfs_PeriodAxis = bfs_MayTenTwoThousandThirteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Exercised (in shares) | 15,625 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalExercisesInPeriod / bfs_PeriodAxis = bfs_MayTenTwoThousandThirteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Forfeited (in shares) | 30,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod / bfs_PeriodAxis = bfs_MayTenTwoThousandThirteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Exercisable at December 31 (in shares) | 35,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber / bfs_PeriodAxis = bfs_MayTenTwoThousandThirteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Remaining unexercised (in shares) | 156,875 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsRemainingUnexercisedNumber / bfs_PeriodAxis = bfs_MayTenTwoThousandThirteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Exercise price (in usd per share) | $ 44.42 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice / bfs_PeriodAxis = bfs_MayTenTwoThousandThirteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Volatility | 0.304 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsVolatility / bfs_PeriodAxis = bfs_MayTenTwoThousandThirteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Expected life (years) | 8 years |  |
Assumed yield | 5.12%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate / bfs_PeriodAxis = bfs_MayTenTwoThousandThirteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Risk-free rate | 1.49%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate / bfs_PeriodAxis = bfs_MayTenTwoThousandThirteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Total value at grant date | 1,401,300 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodFairValue / bfs_PeriodAxis = bfs_MayTenTwoThousandThirteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Estimated forfeitures | 280,468 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeitedInPeriodFairValue / bfs_PeriodAxis = bfs_MayTenTwoThousandThirteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Expensed in previous years | 0 bfs_AllocatedShareBasedCompensationExpenseInPreviousYears / bfs_PeriodAxis = bfs_MayTenTwoThousandThirteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Future expense | 627,895 bfs_EmployeeAndNonEmployeeServiceSharebasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions / bfs_PeriodAxis = bfs_MayTenTwoThousandThirteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Officers | 5/10/2013 | Expensed in 2012 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 0 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodOneMember / bfs_PeriodAxis = bfs_MayTenTwoThousandThirteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Officers | 5/10/2013 | Expensed in 2013 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 209,027 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodTwoMember / bfs_PeriodAxis = bfs_MayTenTwoThousandThirteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Officers | 5/10/2013 | Expensed in 2014 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 283,910 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodThreeMember / bfs_PeriodAxis = bfs_MayTenTwoThousandThirteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Officers | 5/9/2014 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Grant date | May 09, 2014 |  |
Total grant (in shares) | 170,000 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalGrantsInPeriodGross / bfs_PeriodAxis = bfs_MayNineTwoThousandFourteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Vested (in shares) | 0 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedInPeriod / bfs_PeriodAxis = bfs_MayNineTwoThousandFourteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Exercised (in shares) | 0 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalExercisesInPeriod / bfs_PeriodAxis = bfs_MayNineTwoThousandFourteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Forfeited (in shares) | 0 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod / bfs_PeriodAxis = bfs_MayNineTwoThousandFourteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Exercisable at December 31 (in shares) | 0 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber / bfs_PeriodAxis = bfs_MayNineTwoThousandFourteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Remaining unexercised (in shares) | 170,000 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsRemainingUnexercisedNumber / bfs_PeriodAxis = bfs_MayNineTwoThousandFourteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Exercise price (in usd per share) | $ 47.03 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice / bfs_PeriodAxis = bfs_MayNineTwoThousandFourteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Volatility | 0.306 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsVolatility / bfs_PeriodAxis = bfs_MayNineTwoThousandFourteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Expected life (years) | 7 years |  |
Assumed yield | 4.89%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate / bfs_PeriodAxis = bfs_MayNineTwoThousandFourteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Risk-free rate | 2.17%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate / bfs_PeriodAxis = bfs_MayNineTwoThousandFourteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Total value at grant date | 1,349,800 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodFairValue / bfs_PeriodAxis = bfs_MayNineTwoThousandFourteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Estimated forfeitures | 168,749 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeitedInPeriodFairValue / bfs_PeriodAxis = bfs_MayNineTwoThousandFourteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Expensed in previous years | 0 bfs_AllocatedShareBasedCompensationExpenseInPreviousYears / bfs_PeriodAxis = bfs_MayNineTwoThousandFourteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Future expense | 984,203 bfs_EmployeeAndNonEmployeeServiceSharebasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions / bfs_PeriodAxis = bfs_MayNineTwoThousandFourteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Officers | 5/9/2014 | Expensed in 2012 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 0 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodOneMember / bfs_PeriodAxis = bfs_MayNineTwoThousandFourteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Officers | 5/9/2014 | Expensed in 2013 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 0 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodTwoMember / bfs_PeriodAxis = bfs_MayNineTwoThousandFourteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Officers | 5/9/2014 | Expensed in 2014 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 196,848 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodThreeMember / bfs_PeriodAxis = bfs_MayNineTwoThousandFourteenMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Officers | Subtotals |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Total grant (in shares) | 1,045,000 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalGrantsInPeriodGross / bfs_PeriodAxis = bfs_SubtotalMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Vested (in shares) | 398,750 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedInPeriod / bfs_PeriodAxis = bfs_SubtotalMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Exercised (in shares) | 211,792 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsTotalExercisesInPeriod / bfs_PeriodAxis = bfs_SubtotalMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Forfeited (in shares) | 290,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod / bfs_PeriodAxis = bfs_SubtotalMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Exercisable at December 31 (in shares) | 175,708 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber / bfs_PeriodAxis = bfs_SubtotalMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Remaining unexercised (in shares) | 543,208 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsRemainingUnexercisedNumber / bfs_PeriodAxis = bfs_SubtotalMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Total value at grant date | 7,388,375 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodFairValue / bfs_PeriodAxis = bfs_SubtotalMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Estimated forfeitures | 1,823,557 bfs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeitedInPeriodFairValue / bfs_PeriodAxis = bfs_SubtotalMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Expensed in previous years | 1,841,847 bfs_AllocatedShareBasedCompensationExpenseInPreviousYears / bfs_PeriodAxis = bfs_SubtotalMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Future expense | 1,891,071 bfs_EmployeeAndNonEmployeeServiceSharebasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions / bfs_PeriodAxis = bfs_SubtotalMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Officers | Subtotals | Expensed in 2012 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 375,115 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodOneMember / bfs_PeriodAxis = bfs_SubtotalMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Officers | Subtotals | Expensed in 2013 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | 601,460 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodTwoMember / bfs_PeriodAxis = bfs_SubtotalMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |
Officers | Subtotals | Expensed in 2014 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Allocated share based compensation | $ 855,325 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = bfs_ShareBasedCompensationExpensePeriodThreeMember / bfs_PeriodAxis = bfs_SubtotalMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember |  |

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- Definition Employee and Non Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Stock Options + References No definition available. + Details
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- Definition Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Forfeited in Period, Fair Value + References No definition available. + Details
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- Definition Share based Compensation Arrangement by Share based Payment Award, Options, Grants in Period, Fair Value + References No definition available. + Details
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- Definition Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Remaining Unexercised, Number + References No definition available. + Details
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- Definition Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Total Exercises In Period + References No definition available. + Details
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- Definition Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Total Grants in Period, Gross + References No definition available. + Details
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- Definition Share Based Compensation Arrangement by Share Based Payment Award, Options, Vested in Period + References No definition available. + Details
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- Definition Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 14.F) -URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1)(i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 14 -Section F + Details
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- Definition Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2)(iii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 14.D.2) -URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2)(i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 14 -Section D -Subsection 2 + Details
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- Definition The risk-free interest rate assumption that is used in valuing an option on its own shares. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2)(iv) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iv)(3) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Weighted average price at which option holders acquired shares when converting their stock options into shares. + References No definition available. + Details
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