LOANS AND ALLOWANCE FOR CREDIT LOSSES - Summary of Troubled Debt Restructuring (Details) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2022 Contract	Dec. 31, 2021 USD ($) Contract
Troubled Debt Restructurings:
Number of Contracts \| Contract	0	1
Pre-Modification Outstanding Recorded Investment		$ 17
Post-Modification Outstanding Recorded Investment		$ 14
Commercial and industrial
Troubled Debt Restructurings:
Number of Contracts \| Contract		1
Pre-Modification Outstanding Recorded Investment		$ 17
Post-Modification Outstanding Recorded Investment		$ 14

Troubled Debt Restructuring [Abstract]

No definition available.

Name:	gnty_TroubledDebtRestructuringAbstract
Namespace Prefix:	gnty_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=123577603&loc=SL6953676-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsNumberOfContracts2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, after troubled debt restructuring, of modified financing receivable.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount, before troubled debt restructuring, of financing receivable to be modified.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: