XML 100 R80.htm IDEA: XBRL DOCUMENT
v3.19.1

SUBORDINATED DEBENTURES - Narrative (Details) | 1 Months Ended | 12 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | ---
Jul. 31, 2018 USD ($) | Dec. 31, 2018 USD ($) trust $ / shares | Jul. 31, 2017 USD ($) | May 31, 2017 USD ($) | Dec. 31, 2015 USD ($) | Jul. 31, 2015 USD ($)
Subordinated debentures |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Debenture term |  | 30 years |  |  |  |
Subordinated debentures | Trust II Debentures |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Debenture issued |  | $ 3,093,000 |  |  |  |
Subordinated debentures | Trust II Debentures | Minimum |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Notice period required for redemption of debentures |  | 30 days |  |  |  |
Subordinated debentures | 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% |  |  |  |
Subordinated debentures | Trust II Debentures | 3 Month LIBOR |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Spread on variable rate |  | 3.35% |  |  |  |
Subordinated debentures | Trust III Debentures |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Debenture issued |  | $ 2,062,000 |  |  |  |
Subordinated debentures | Trust III Debentures | Minimum |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Notice period required for redemption of debentures |  | 30 days |  |  |  |
Subordinated debentures | Trust III Debentures | Maximum |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Redemption price of debentures as a percentage of principal |  | 100.00% |  |  |  |
Subordinated debentures | Trust III Debentures | 3 Month LIBOR |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Spread on variable rate |  | 1.67% |  |  |  |
Subordinated debentures | DCB Trust I Debentures |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Debenture issued |  | $ 5,155,000 |  |  |  |
Subordinated debentures | DCB Trust I Debentures | Minimum |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Notice period required for redemption of debentures |  | 30 days |  |  |  |
Subordinated debentures | 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% |  |  |  |
Subordinated debentures | DCB Trust I Debentures | 3 Month LIBOR |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Spread on variable rate |  | 1.80% |  |  |  |
Subordinated debentures | 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
Debentures that matured and were paid off | $ 1,000,000 |  |  |  |  |
Subordinated debentures | Other Debentures Issued in July 2015 | Directors and Related Parties |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Debenture issued |  |  |  | $ 2,000,000 |  | $ 3,000,000
Subordinated debentures | Other Subordinated Debentures Issued in July 2015, 2.50%, Maturing July 1, 2017 |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Stated interest rate |  |  | 2.50% |  |  |
Debenture issued, par value per instrument issued |  |  | $ 500,000 |  |  |
Subordinated debentures | Other Subordinated Debentures Issued in July 2015, 4.00%, Maturing January 1, 2019 |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Stated interest rate |  | 4.00% |  |  |  |
Debenture issued, par value per instrument issued |  | $ 500,000 |  |  |  |
Subordinated debentures | Other Debentures Issued in December 2015 |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Redemption price of debentures as a percentage of principal |  | 100.00% |  |  |  |
Debenture issued |  | $ 2,000,000 |  |  | $ 5,000,000 |
Debenture issued, par value per instrument issued |  | $ 500,000 |  |  |  |
Subordinated debentures | Other Debentures Issued in December 2015 | Directors and Related Parties |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Debenture issued |  |  |  |  | $ 2,500,000 |
Subordinated debentures | Other Debentures Issued in December 2015 | Minimum |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Stated interest rate |  | 3.50% |  |  |  |
Subordinated debentures | 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 |  |  |  |

X
- Definition Debt Instrument, Notice Period Required for Redemption + References No definition available. + Details
Name: | gnty_DebtInstrumentNoticePeriodRequiredforRedemption
Namespace Prefix: | gnty_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- 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

X
- 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

X
- 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

X
- 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

X
- 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

X
- 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

X
- 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

X
- 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

X
- 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

X
- 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

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

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

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

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

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

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

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

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

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

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

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