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v3.20.1

Employee Benefit Plans (Details Textual) - USD ($) | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Employee Benefit Plans |  |  |
Administrative expense | $ 2,400 | $ 1,100 | $ 1,700
Discretionary contribution | 250,000 | 265,000 | 255,000
Deferred Compensation Expense Non Qualified Plan | $ 135,000 | $ 149,000 | $ 211,000

X
- Definition The compensation expense recognized during the period pertaining to non qualified deferred compensation plan. + References No definition available. + Details
Name: | sga_DeferredCompensationExpenseNonQualifiedPlan
Namespace Prefix: | sga_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_CompensationAndRetirementDisclosureAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of administrative expense incurred by defined contribution plan. + References No definition available. + Details
Name: | us-gaap_DefinedContributionPlanAdministrativeExpenses
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of discretionary contributions made by an employer to a defined contribution plan. + References No definition available. + Details
Name: | us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration