Debt Instrument, Notice Period Required for Redemption

No definition available.

Name:	gnty_DebtInstrumentNoticePeriodRequiredforRedemption
Namespace Prefix:	gnty_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt Instrument, Par Value

+ References

No definition available.

+ Details

Name:	gnty_DebtInstrumentParValue
Namespace Prefix:	gnty_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Financial Instruments Subject To Mandatory Redemption, Settlement Terms, Liquidation Value

+ References

No definition available.

+ Details

Name:	gnty_FinancialInstrumentsSubjectToMandatoryRedemptionSettlementTermsLiquidationValue
Namespace Prefix:	gnty_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Financial Instruments Subject to Mandatory Redemption, Number of Trusts

+ References

No definition available.

+ Details

Name:	gnty_FinancialInstrumentsSubjecttoMandatoryRedemptionNumberofTrusts
Namespace Prefix:	gnty_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

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

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
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_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph e
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

+ Details

Name:	us-gaap_DebtInstrumentRedemptionPricePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3291-108585

+ Details

Name:	us-gaap_RepaymentsOfDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SubordinatedDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=gnty_SubordinatedDebenturesIIMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=gnty_SubordinatedDebenturesIIIMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=gnty_SubordinatedDCBDebenturesIMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=gnty_OtherSubordinatedDebenturesIssuedinJuly2015Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=gnty_DirectorsandRelatedPartiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=gnty_OtherSubordinatedDebenturesIssuedinJuly20152.50MaturingJuly12017Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=gnty_OtherSubordinatedDebenturesIssuedinJuly20154.00MaturingJanuary12019Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=gnty_OtherSubordinatedDebenturesIssuedinDecember2015Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ScheduleOfSharesSubjectToMandatoryRedemptionBySettlementTermsAxis=us-gaap_TrustPreferredSecuritiesSubjectToMandatoryRedemptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

SUBORDINATED DEBENTURES - Narrative (Details)	1 Months Ended	9 Months Ended	12 Months Ended
SUBORDINATED DEBENTURES - Narrative (Details)	Jul. 31, 2018 USD ($)	Sep. 30, 2018 USD ($) trust $ / shares	Dec. 31, 2017	Jul. 31, 2017 USD ($)	May 31, 2017 USD ($)	Dec. 31, 2015 USD ($)	Jul. 31, 2015 USD ($)
Federal Home Loan Bank advances
Debt Instrument [Line Items]
Debenture term		30 years
Federal Home Loan Bank advances \| Trust II Debentures
Debt Instrument [Line Items]
Debenture issued		$ 3,093,000
Federal Home Loan Bank advances \| Trust II Debentures \| Minimum
Debt Instrument [Line Items]
Notice period required for redemption of debentures		30 days
Federal Home Loan Bank advances \| Trust II Debentures \| Maximum
Debt Instrument [Line Items]
Notice period required for redemption of debentures		60 days
Redemption price of debentures as a percentage of principal		100.00%
Federal Home Loan Bank advances \| Trust II Debentures \| 3 Month LIBOR
Debt Instrument [Line Items]
Spread on variable rate		3.35%
Federal Home Loan Bank advances \| Trust III Debentures
Debt Instrument [Line Items]
Debenture issued		$ 2,062,000
Federal Home Loan Bank advances \| Trust III Debentures \| Minimum
Debt Instrument [Line Items]
Notice period required for redemption of debentures		30 days
Federal Home Loan Bank advances \| Trust III Debentures \| Maximum
Debt Instrument [Line Items]
Notice period required for redemption of debentures		60 days
Redemption price of debentures as a percentage of principal		100.00%
Federal Home Loan Bank advances \| Trust III Debentures \| 3 Month LIBOR
Debt Instrument [Line Items]
Spread on variable rate		1.67%	1.67%
Federal Home Loan Bank advances \| DCB Trust I Debentures
Debt Instrument [Line Items]
Debenture issued		$ 5,155,000
Federal Home Loan Bank advances \| DCB Trust I Debentures \| Minimum
Debt Instrument [Line Items]
Notice period required for redemption of debentures		30 days
Federal Home Loan Bank advances \| DCB Trust I Debentures \| Maximum
Debt Instrument [Line Items]
Notice period required for redemption of debentures		60 days
Redemption price of debentures as a percentage of principal		100.00%
Federal Home Loan Bank advances \| DCB Trust I Debentures \| 3 Month LIBOR
Debt Instrument [Line Items]
Spread on variable rate		1.80%
Federal Home Loan Bank advances \| Other Debentures Issued in July 2015
Debt Instrument [Line Items]
Notice period required for redemption of debentures		30 days
Redemption price of debentures as a percentage of principal		100.00%
Debenture issued							$ 4,000,000
Federal Home Loan Bank advances \| Other Debentures Issued in July 2015 \| Directors and Related Parties
Debt Instrument [Line Items]
Debenture issued					$ 2,000,000		$ 3,000,000
Federal Home Loan Bank advances \| Other Subordinated Debentures, 2.50%
Debt Instrument [Line Items]
Debenture issued, par value per instrument issued				$ 500,000
Stated interest rate		25.00%		2.50%
Federal Home Loan Bank advances \| Other Subordinated Debentures, 4.00%
Debt Instrument [Line Items]
Debenture issued, par value per instrument issued		$ 500,000
Stated interest rate		4.00%
Federal Home Loan Bank advances \| Other Debentures Issued in December 2015
Debt Instrument [Line Items]
Notice period required for redemption of debentures		30 days
Redemption price of debentures as a percentage of principal		100.00%
Debenture issued		$ 2,000,000				$ 5,000,000
Debentures that matured and were repaid	$ 1,000
Debenture issued, par value per instrument issued		$ 500,000
Federal Home Loan Bank advances \| Other Debentures Issued in December 2015 \| Directors and Related Parties
Debt Instrument [Line Items]
Debenture issued						$ 2,500,000
Federal Home Loan Bank advances \| Other Debentures Issued in December 2015 \| Minimum
Debt Instrument [Line Items]
Stated interest rate		3.50%
Federal Home Loan Bank advances \| Other Debentures Issued in December 2015 \| Maximum
Debt Instrument [Line Items]
Stated interest rate		5.00%
Capital trust pass-through securities
Debt Instrument [Line Items]
Number of trusts \| trust		3
Liquidation value per share (in USD per share) \| $ / shares		$ 1,000,000