Share Based Compensation Arrangement by Share Based Payment Award, Fair Value Assumptions, Volatility

No definition available.

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

- 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

+ Details

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

- Definition

The risk-free interest rate assumption that is used in valuing an option on its own shares.

+ References

+ Details

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

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Definition

Weighted average price at which option holders acquired shares when converting their stock options into shares.

+ References

No definition available.

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Expected term of award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-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=116856206&loc=d3e5070-113901

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-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=115993241&loc=d3e301413-122809

+ Details

Name:	us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	srt_TitleOfIndividualAxis=srt_DirectorMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardDateAxis=bfs_May52017Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardDateAxis=bfs_May112018Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardDateAxis=bfs_May32019Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_TitleOfIndividualAxis=srt_OfficerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Stock Option Plan - Stock Options Issued (Detail)	12 Months Ended
Stock Option Plan - Stock Options Issued (Detail)	Dec. 31, 2019 $ / shares	Dec. 31, 2018 $ / shares	Dec. 31, 2017 $ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price (in usd per share)	$ 44.53	$ 42.98	$ 46.97
Directors \| May 5, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price (in usd per share)	$ 59.41
Volatility	0.173
Expected life (years)	5 years
Assumed yield	3.45%
Risk-free rate	1.89%
Directors \| May 11, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price (in usd per share)	$ 49.46
Volatility	0.192
Expected life (years)	5 years
Assumed yield	3.70%
Risk-free rate	2.84%
Directors \| May 3, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price (in usd per share)	$ 55.71
Volatility	0.236
Expected life (years)	5 years
Assumed yield	3.75%
Risk-free rate	2.33%
Officers \| May 5, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price (in usd per share)	$ 59.41
Volatility	0.170
Expected life (years)	7 years
Assumed yield	3.50%
Risk-free rate	2.17%
Officers \| May 11, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price (in usd per share)	$ 49.46
Volatility	0.177
Expected life (years)	7 years
Assumed yield	3.75%
Risk-free rate	2.94%
Officers \| May 3, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price (in usd per share)	$ 55.71
Volatility	0.206
Expected life (years)	7 years
Assumed yield	3.80%
Risk-free rate	2.43%