Financing Receivables, Impaired, Troubled Debt Restructuring, Increase in Allowance for Loan Losses

No definition available.

Name:	gnty_FinancingReceivablesImpairedTroubledDebtRestructuringIncreaseinAllowanceforLoanLosses
Namespace Prefix:	gnty_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Troubled Debt Restructuring [Abstract]

+ References

No definition available.

+ Details

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

- Definition

Amount of allowance for credit losses related to receivables which had been measured under a general allowance for credit losses methodology that are now identified as troubled debt restructurings.

+ References

No definition available.

+ Details

Name:	us-gaap_AllowanceForCreditLossesChangeInMethodOfCalculatingImpairment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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_FinancingReceivableModificationsLineItems
Namespace Prefix:	us-gaap_
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/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953676-111524

+ Details

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

- Definition

Post-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ References

+ Details

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

- Definition

Pre-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ References

+ Details

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

- Definition

The amount of the outstanding recorded investment related to financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=82895541&loc=d3e18845-111554

+ Details

Name:	us-gaap_FinancingReceivableModificationsRecordedInvestment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Reflects the amount of the write-down related to a troubled debt restructuring.

+ References

+ Details

Name:	us-gaap_FinancingReceivablesImpairedTroubledDebtRestructuringWriteDown
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:

- Details

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

- Details

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

- Details

Name:	us-gaap_FinancialInstrumentPerformanceStatusAxis=us-gaap_NonperformingFinancingReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentPerformanceStatusAxis=us-gaap_PerformingFinancingReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

LOANS AND ALLOWANCE FOR LOAN LOSSES - Troubled Debt Restructuring (Details)	6 Months Ended
	Jun. 30, 2018 USD ($) contract	Jun. 30, 2017 USD ($) contract	Dec. 31, 2017 USD ($)
Financing Receivable, Modifications [Line Items]
Total	$ 737,000		$ 657,000
Specific reserves on TDRs	$ 14,000		17,000
Troubled Debt Restructurings:
Number of Contracts \| contract	2	2
Pre-Modification Outstanding Recorded Investment	$ 93,000	$ 45,000
Post-Modification Outstanding Recorded Investment	$ 93,000	24,000
Increase in allowance for loan losses due to TDRs		0
Troubled debt restructuring charge-offs		$ 0
Commercial and industrial
Troubled Debt Restructurings:
Number of Contracts \| contract		1
Pre-Modification Outstanding Recorded Investment		$ 34,000
Post-Modification Outstanding Recorded Investment		$ 13,000
1-4 family residential
Troubled Debt Restructurings:
Number of Contracts \| contract	1	1
Pre-Modification Outstanding Recorded Investment	$ 15,000	$ 11,000
Post-Modification Outstanding Recorded Investment	$ 15,000	$ 11,000
Farmland
Troubled Debt Restructurings:
Number of Contracts \| contract	1
Pre-Modification Outstanding Recorded Investment	$ 78,000
Post-Modification Outstanding Recorded Investment	78,000
Nonaccrual TDRs
Financing Receivable, Modifications [Line Items]
Total	0		0
Performing TDRs
Financing Receivable, Modifications [Line Items]
Total	$ 737,000		$ 657,000