Investments in Limited Partnerships - Investments in Community Development Entities (Details) - USD ($)	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Investments in Limited Partnerships
Investments in Community Development Entities Net Carrying Amount	$ 567,000
Investments In Limited Partnerships For Federal Or Historic Tax Credits	863,000
Usage of Investment in Community Development Entities Federal New Market Tax Credits	100,000	$ 480,000	$ 480,000
Actual Amortization of Investment in Community Development Entities	$ 80,000	$ 365,000	$ 575,000
credit allowance period	7 years
Community Development Entities, Minimum Period Before Redemption	7 years
credit allowance period for federal rehabilitation/historic tax credits	5 years

Represents the monetary amount of Actual Amortization of Investment in Community Development Entities, during the indicated time period.

No definition available.

Name:	gsbc_ActualAmortizationOfInvestmentInCommunityDevelopmentEntities
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Represents the Community Development Entities, Minimum Period Before Redemption.

No definition available.

Name:	gsbc_CommunityDevelopmentEntitiesMinimumPeriodBeforeRedemption
Namespace Prefix:	gsbc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Represents the credit allowance period.

No definition available.

Name:	gsbc_CreditAllowancePeriod
Namespace Prefix:	gsbc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Represents the credit allowance period for federal rehabilitation/historic tax credits

No definition available.

Name:	gsbc_CreditAllowancePeriodForFederalRehabilitationHistoricTaxCredits
Namespace Prefix:	gsbc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Represents the monetary amount of Investments in Community Development Entities Net Carrying Amount, as of the indicated date.

No definition available.

Name:	gsbc_InvestmentsInCommunityDevelopmentEntitiesNetCarryingAmount
Namespace Prefix:	gsbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

No definition available.

Name:	gsbc_InvestmentsInLimitedPartnershipsAbstract
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Data Type:	xbrli:stringItemType
Balance Type:	na
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Investments In Limited Partnerships For Federal Or Historic Tax Credits

No definition available.

Name:	gsbc_InvestmentsInLimitedPartnershipsForFederalOrHistoricTaxCredits
Namespace Prefix:	gsbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Represents the monetary amount of Usage of Investment in Community Development Entities Federal New Market Tax Credits, as of the indicated date.

No definition available.

Name:	gsbc_UsageOfInvestmentInCommunityDevelopmentEntitiesFederalNewMarketTaxCredits
Namespace Prefix:	gsbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant