v3.25.3

Loans - Schedule of Past due Financing Receivables (Details) - USD ($) $ in Thousands | Sep. 30, 2025 | Dec. 31, 2024
--- | --- | ---
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | $ 2,286,173 | $ 2,702,080
Unearned income | (6,432) | (8,300)
Total loans net of unearned income | 2,279,741 | 2,693,780
Recorded Investment 90 Days Accruing | 0 | 11,502
Total Past Due |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 135,432 | 176,146
30-89 Days Past Due |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 21,167 | 56,115
90 Days or Greater |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 114,265 | 120,031
Current |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 2,150,741 | 2,525,934
Real Estate: |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 1,844,638 | 2,141,373
Recorded Investment 90 Days Accruing | 0 | 11,502
Real Estate: | Total Past Due |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 108,616 | 162,796
Real Estate: | 30-89 Days Past Due |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 20,066 | 53,285
Real Estate: | 90 Days or Greater |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 88,550 | 109,511
Real Estate: | Current |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 1,736,022 | 1,978,577
Real Estate: | Construction & land development |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 231,156 | 330,048
Recorded Investment 90 Days Accruing | 0 | 7,394
Real Estate: | Construction & land development | Total Past Due |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 8,751 | 12,580
Real Estate: | Construction & land development | 30-89 Days Past Due |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 44 | 1,562
Real Estate: | Construction & land development | 90 Days or Greater |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 8,707 | 11,018
Real Estate: | Construction & land development | Current |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 222,405 | 317,468
Real Estate: | Farmland |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 31,685 | 35,991
Recorded Investment 90 Days Accruing | 0 | 0
Real Estate: | Farmland | Total Past Due |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 7,061 | 2,619
Real Estate: | Farmland | 30-89 Days Past Due |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 4,284 | 0
Real Estate: | Farmland | 90 Days or Greater |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 2,777 | 2,619
Real Estate: | Farmland | Current |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 24,624 | 33,372
Real Estate: | 1- 4 family |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 441,017 | 450,371
Recorded Investment 90 Days Accruing | 0 | 0
Real Estate: | 1- 4 family | Total Past Due |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 13,395 | 22,970
Real Estate: | 1- 4 family | 30-89 Days Past Due |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 2,859 | 12,917
Real Estate: | 1- 4 family | 90 Days or Greater |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 10,536 | 10,053
Real Estate: | 1- 4 family | Current |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 427,622 | 427,401
Real Estate: | Multifamily |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 137,582 | 165,121
Recorded Investment 90 Days Accruing | 0 | 0
Real Estate: | Multifamily | Total Past Due |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 23,998 | 27,741
Real Estate: | Multifamily | 30-89 Days Past Due |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 0 | 199
Real Estate: | Multifamily | 90 Days or Greater |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 23,998 | 27,542
Real Estate: | Multifamily | Current |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 113,584 | 137,380
Real Estate: | Non-farm non-residential |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 1,003,198 | 1,159,842
Recorded Investment 90 Days Accruing | 0 | 4,108
Real Estate: | Non-farm non-residential | Total Past Due |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 55,411 | 96,886
Real Estate: | Non-farm non-residential | 30-89 Days Past Due |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 12,879 | 38,607
Real Estate: | Non-farm non-residential | 90 Days or Greater |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 42,532 | 58,279
Real Estate: | Non-farm non-residential | Current |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 947,787 | 1,062,956
Non-Real Estate: |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 441,535 | 560,707
Recorded Investment 90 Days Accruing | 0 | 0
Non-Real Estate: | Total Past Due |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 26,816 | 13,350
Non-Real Estate: | 30-89 Days Past Due |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 1,101 | 2,830
Non-Real Estate: | 90 Days or Greater |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 25,715 | 10,520
Non-Real Estate: | Current |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 414,719 | 547,357
Non-Real Estate: | Agricultural |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 44,737 | 40,722
Recorded Investment 90 Days Accruing | 0 | 0
Non-Real Estate: | Agricultural | Total Past Due |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 1,918 | 2,669
Non-Real Estate: | Agricultural | 30-89 Days Past Due |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 32 | 677
Non-Real Estate: | Agricultural | 90 Days or Greater |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 1,886 | 1,992
Non-Real Estate: | Agricultural | Current |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 42,819 | 38,053
Non-Real Estate: | Commercial and industrial |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 227,077 | 257,518
Recorded Investment 90 Days Accruing | 0 | 0
Non-Real Estate: | Commercial and industrial | Total Past Due |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 5,894 | 8,055
Non-Real Estate: | Commercial and industrial | 30-89 Days Past Due |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 555 | 1,293
Non-Real Estate: | Commercial and industrial | 90 Days or Greater |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 5,339 | 6,762
Non-Real Estate: | Commercial and industrial | Current |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 221,183 | 249,463
Non-Real Estate: | Commercial leases |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 134,958 | 220,200
Recorded Investment 90 Days Accruing | 0 | 0
Non-Real Estate: | Commercial leases | Total Past Due |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 18,358 | 1,533
Non-Real Estate: | Commercial leases | 30-89 Days Past Due |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 0 | 0
Non-Real Estate: | Commercial leases | 90 Days or Greater |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 18,358 | 1,533
Non-Real Estate: | Commercial leases | Current |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 116,600 | 218,667
Non-Real Estate: | Consumer and other |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 34,763 | 42,267
Recorded Investment 90 Days Accruing | 0 | 0
Non-Real Estate: | Consumer and other | Total Past Due |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 646 | 1,093
Non-Real Estate: | Consumer and other | 30-89 Days Past Due |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 514 | 860
Non-Real Estate: | Consumer and other | 90 Days or Greater |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | 132 | 233
Non-Real Estate: | Consumer and other | Current |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total Loans before Unearned Income | $ 34,117 | $ 41,174

X
- Definition Amount of fee received for commitment to originate or purchase financing receivable where likelihood of commitment being exercised is remote, to be recognized as service income. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 310 -SubTopic 20 -Name Accounting Standards Codification -Section 45 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147481598/310-20-45-2 + Details
Name: | us-gaap_FinancingReceivableDeferredIncome
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amortized cost excluding accrued interest, of financing receivable 90 days or more past due and still accruing. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 16 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479319/326-20-50-16 + Details
Name: | us-gaap_FinancingReceivableExcludingAccruedInterest90DaysOrMorePastDueStillAccruing
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amortized cost excluding accrued interest, before allowance for credit loss, of financing receivable. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479344/326-20-45-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 3B -Publisher FASB -URI https://asc.fasb.org/1943274/2147479319/326-20-50-3B Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479319/326-20-50-5 + Details
Name: | us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amortized cost excluding accrued interest, before allowance for credit loss, fee, and loan in process, of financing receivable. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(7)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1 + Details
Name: | us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLossFeeAndLoanInProcess
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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 Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 12 -Subparagraph (a)(3) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479294/326-20-55-12 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 12 -Subparagraph (a)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479294/326-20-55-12 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 12 -Subparagraph (a)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479294/326-20-55-12 Reference 4: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 12 -Subparagraph (d)(4) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479294/326-20-55-12 Reference 5: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 12 -Subparagraph (d)(3) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479294/326-20-55-12 Reference 6: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 12 -Subparagraph (d)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479294/326-20-55-12 Reference 7: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 12 -Subparagraph (d)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479294/326-20-55-12 Reference 8: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 12 -Subparagraph (b)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479294/326-20-55-12 Reference 9: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 12 -Subparagraph (c)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479294/326-20-55-12 Reference 10: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 12 -Subparagraph (c)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479294/326-20-55-12 Reference 11: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 14 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479319/326-20-50-14 Reference 12: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 12 -Subparagraph (e)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479294/326-20-55-12 Reference 13: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 12 -Subparagraph (e)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479294/326-20-55-12 Reference 14: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 12 -Subparagraph (b)(4) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479294/326-20-55-12 Reference 15: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 12 -Subparagraph (b)(3) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479294/326-20-55-12 Reference 16: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 12 -Subparagraph (b)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479294/326-20-55-12 Reference 17: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 80 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479294/326-20-55-80 + Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_FinancingReceivablesPeriodPastDueAxis=us-gaap_FinancialAssetPastDueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablesPeriodPastDueAxis=fgbi_FinancingReceivables30To89DaysPastDueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablesPeriodPastDueAxis=us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablesPeriodPastDueAxis=us-gaap_FinancialAssetNotPastDueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialRealEstatePortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=fgbi_ConstructionAndLandDevelopmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=fgbi_FarmlandMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=fgbi_OneToFourFamilyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=fgbi_Multi-FamilyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=fgbi_NonFarmNonResidentialMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=fgbi_NonRealEstatePortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=fgbi_AgriculturalMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=fgbi_CommercialAndIndustrialMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=fgbi_CommercialLeasesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=fgbi_ConsumerAndOtherMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |