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v3.22.1

Note 4 - Periodic Pension Expense (Details Textual) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2022 USD ($) yr
Defined Benefit Plans Number of Plans | 2
Defined Benefit Plans Retirement Age (Year) | yr | 65
Noncontributory Qualified Defined Pension Plans [Member] |
Defined Benefit Plan, Remaining Undistributed Asset Surplus | $ | $ 0.4

X
- Definition Represents the amount of remaining undistributed asset surplus under a defined benefit plan. + References No definition available. + Details
Name: | sgc_DefinedBenefitPlanRemainingUndistributedAssetSurplus
Namespace Prefix: | sgc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Defined benefit plans number of plans + References No definition available. + Details
Name: | sgc_DefinedBenefitPlansNumberOfPlans
Namespace Prefix: | sgc_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Defined benefit plans retirement age + References No definition available. + Details
Name: | sgc_DefinedBenefitPlansRetirementAge
Namespace Prefix: | sgc_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_RetirementPlanTypeAxis=sgc_NoncontributoryQualifiedDefinedPensionPlansMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |