XML 52 R41.htm IDEA: XBRL DOCUMENT
v3.25.3

Loans and Allowance for Loan Losses - Schedule of Current, Accruing Past Due, and Non-Accrual Loans on an Amortized Cost Basis by Loan Portfolio Class (Details) - USD ($) $ in Thousands | Sep. 30, 2025 | Sep. 30, 2024
--- | --- | ---
Financing Receivable, Modified [Line Items] |  |
Amortized cost basis of loans, aging analysis | $ 65,057 | $ 108,296
Current |  |
Financing Receivable, Modified [Line Items] |  |
Amortized cost basis of loans, aging analysis | 52,216 | 73,623
Accruing 30-89 Days Past Due |  |
Financing Receivable, Modified [Line Items] |  |
Amortized cost basis of loans, aging analysis | 139 | 1,111
Non-accrual |  |
Financing Receivable, Modified [Line Items] |  |
Amortized cost basis of loans, aging analysis | 12,702 | 33,562
Total commercial and industrial |  |
Financing Receivable, Modified [Line Items] |  |
Amortized cost basis of loans, aging analysis | 46,409 | 30,594
Total commercial and industrial | Current |  |
Financing Receivable, Modified [Line Items] |  |
Amortized cost basis of loans, aging analysis | 45,593 | 28,984
Total commercial and industrial | Accruing 30-89 Days Past Due |  |
Financing Receivable, Modified [Line Items] |  |
Amortized cost basis of loans, aging analysis | 0 | 1,005
Total commercial and industrial | Non-accrual |  |
Financing Receivable, Modified [Line Items] |  |
Amortized cost basis of loans, aging analysis | 816 | 605
Total commercial and industrial | Commercial, financial and agricultural |  |
Financing Receivable, Modified [Line Items] |  |
Amortized cost basis of loans, aging analysis | 42,378 | 27,599
Total commercial and industrial | Commercial, financial and agricultural | Current |  |
Financing Receivable, Modified [Line Items] |  |
Amortized cost basis of loans, aging analysis | 41,562 | 26,239
Total commercial and industrial | Commercial, financial and agricultural | Accruing 30-89 Days Past Due |  |
Financing Receivable, Modified [Line Items] |  |
Amortized cost basis of loans, aging analysis | 0 | 1,005
Total commercial and industrial | Commercial, financial and agricultural | Non-accrual |  |
Financing Receivable, Modified [Line Items] |  |
Amortized cost basis of loans, aging analysis | 816 | 355
Total commercial and industrial | Owner-occupied |  |
Financing Receivable, Modified [Line Items] |  |
Amortized cost basis of loans, aging analysis | 4,031 | 2,995
Total commercial and industrial | Owner-occupied | Current |  |
Financing Receivable, Modified [Line Items] |  |
Amortized cost basis of loans, aging analysis | 4,031 | 2,745
Total commercial and industrial | Owner-occupied | Accruing 30-89 Days Past Due |  |
Financing Receivable, Modified [Line Items] |  |
Amortized cost basis of loans, aging analysis | 0 | 0
Total commercial and industrial | Owner-occupied | Non-accrual |  |
Financing Receivable, Modified [Line Items] |  |
Amortized cost basis of loans, aging analysis | 0 | 250
Total commercial real estate |  |
Financing Receivable, Modified [Line Items] |  |
Amortized cost basis of loans, aging analysis | 2,333 | 76,497
Total commercial real estate | Current |  |
Financing Receivable, Modified [Line Items] |  |
Amortized cost basis of loans, aging analysis | 2,333 | 44,100
Total commercial real estate | Accruing 30-89 Days Past Due |  |
Financing Receivable, Modified [Line Items] |  |
Amortized cost basis of loans, aging analysis | 0 | 0
Total commercial real estate | Non-accrual |  |
Financing Receivable, Modified [Line Items] |  |
Amortized cost basis of loans, aging analysis | 0 | 32,397
Total commercial real estate | Investment properties |  |
Financing Receivable, Modified [Line Items] |  |
Amortized cost basis of loans, aging analysis | 2,333 | 76,497
Total commercial real estate | Investment properties | Current |  |
Financing Receivable, Modified [Line Items] |  |
Amortized cost basis of loans, aging analysis | 2,333 | 44,100
Total commercial real estate | Investment properties | Accruing 30-89 Days Past Due |  |
Financing Receivable, Modified [Line Items] |  |
Amortized cost basis of loans, aging analysis | 0 | 0
Total commercial real estate | Investment properties | Non-accrual |  |
Financing Receivable, Modified [Line Items] |  |
Amortized cost basis of loans, aging analysis | 0 | 32,397
Total consumer |  |
Financing Receivable, Modified [Line Items] |  |
Amortized cost basis of loans, aging analysis | 16,315 | 1,205
Total consumer | Current |  |
Financing Receivable, Modified [Line Items] |  |
Amortized cost basis of loans, aging analysis | 4,290 | 539
Total consumer | Accruing 30-89 Days Past Due |  |
Financing Receivable, Modified [Line Items] |  |
Amortized cost basis of loans, aging analysis | 139 | 106
Total consumer | Non-accrual |  |
Financing Receivable, Modified [Line Items] |  |
Amortized cost basis of loans, aging analysis | 11,886 | 560
Total consumer | Consumer mortgages |  |
Financing Receivable, Modified [Line Items] |  |
Amortized cost basis of loans, aging analysis | 13,012 | 331
Total consumer | Consumer mortgages | Current |  |
Financing Receivable, Modified [Line Items] |  |
Amortized cost basis of loans, aging analysis | 1,501 | 0
Total consumer | Consumer mortgages | Accruing 30-89 Days Past Due |  |
Financing Receivable, Modified [Line Items] |  |
Amortized cost basis of loans, aging analysis | 0 | 0
Total consumer | Consumer mortgages | Non-accrual |  |
Financing Receivable, Modified [Line Items] |  |
Amortized cost basis of loans, aging analysis | 11,511 | 331
Total consumer | Other consumer loans |  |
Financing Receivable, Modified [Line Items] |  |
Amortized cost basis of loans, aging analysis | 3,303 | 874
Total consumer | Other consumer loans | Current |  |
Financing Receivable, Modified [Line Items] |  |
Amortized cost basis of loans, aging analysis | 2,789 | 539
Total consumer | Other consumer loans | Accruing 30-89 Days Past Due |  |
Financing Receivable, Modified [Line Items] |  |
Amortized cost basis of loans, aging analysis | 139 | 106
Total consumer | Other consumer loans | Non-accrual |  |
Financing Receivable, Modified [Line Items] |  |
Amortized cost basis of loans, aging analysis | $ 375 | $ 229

X
- Definition Amortized cost excluding accrued interest, of financing receivable 12 months after modification for debtor experiencing financial difficulty. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 310 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 42 -Subparagraph (a)(3) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481962/310-10-50-42 + Details
Name: | us-gaap_FinancingReceivableExcludingAccruedInterestModifiedPast12Months
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 310 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 12A -Publisher FASB -URI https://asc.fasb.org/1943274/2147481933/310-10-55-12A Reference 2: http://fasb.org/us-gaap/role/ref/otherTransitionRef -Topic 310 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 34 -Publisher FASB -URI https://asc.fasb.org/1943274/2147481962/310-10-50-34 Reference 3: http://fasb.org/us-gaap/role/ref/otherTransitionRef -Topic 310 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 33 -Publisher FASB -URI https://asc.fasb.org/1943274/2147481962/310-10-50-33 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 310 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 42 -Subparagraph (a)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481962/310-10-50-42 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 310 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 42 -Subparagraph (a)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481962/310-10-50-42 + Details
Name: | us-gaap_FinancingReceivableModificationsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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

X
- Details
Name: | us-gaap_FinancingReceivablesPeriodPastDueAxis=syn_FinancialAsset30To89DaysPastDueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

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

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

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

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

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

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

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

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