$FISI
FINANCIAL INSTITUTIONS INC Stock $fisi

$fisi Overview Financials Valuation SEC Filings Company Website

2024 Q1 Form 10-K Financial Statement

#000095017024030754 Filed on March 13, 2024

Income Statement

Concept	2024 Q1	2023 Q4	2023
Revenue	$78.41M		$286.1M
YoY Change	22.96%		45.91%
Cost Of Revenue
YoY Change
Gross Profit
YoY Change
Gross Profit Margin
Selling, General & Admin
YoY Change
% of Gross Profit
Research & Development
YoY Change
% of Gross Profit
Depreciation & Amortization	$2.027M	$1.991M	$8.091M
YoY Change	-1.98%	-4.0%	-0.26%
% of Gross Profit
Operating Expenses
YoY Change
Operating Profit
YoY Change
Interest Expense	$38.33M		$120.4M
YoY Change	74.58%		319.06%
% of Operating Profit
Other Income/Expense, Net
YoY Change
Pretax Income	$2.426M	$14.94M	$63.05M
YoY Change	-83.68%	3.31%	-11.16%
Income Tax	$356.0K	$5.156M	$12.79M
% Of Pretax Income	14.67%	34.52%	20.28%
Net Earnings	$1.705M	$9.415M	$48.81M
YoY Change	-85.9%	-19.69%	-13.73%
Net Earnings / Revenue	2.17%		17.06%
Basic Earnings Per Share	$0.11		$3.17
Diluted Earnings Per Share	$0.11	$0.61	$3.15
COMMON SHARES
Basic Shares Outstanding	15.41M	15.40M	15.38M
Diluted Shares Outstanding	15.54M		15.48M

Balance Sheet

Concept	2024 Q1	2023 Q4	2023
SHORT-TERM ASSETS
Cash & Short-Term Investments
YoY Change
Cash & Equivalents	$237.0M	$124.4M
Short-Term Investments
Other Short-Term Assets
YoY Change
Inventory
Prepaid Expenses
Receivables
Other Receivables
Total Short-Term Assets
YoY Change
LONG-TERM ASSETS
Property, Plant & Equipment	$39.80M	$39.90M	$71.43M
YoY Change	-4.35%	-4.96%	-2.3%
Goodwill	$67.07M	$67.07M
YoY Change	0.0%	0.0%
Intangibles
YoY Change
Long-Term Investments
YoY Change
Other Assets			$48.73M
YoY Change			-8.79%
Total Long-Term Assets
YoY Change
TOTAL ASSETS
Total Short-Term Assets
Total Long-Term Assets
Total Assets	$6.299B	$6.161B	$6.161B
YoY Change	5.56%	6.27%	6.27%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable
YoY Change
Accrued Expenses	$33.68M	$33.79M	$33.79M
YoY Change	1.6%	1.68%	1.68%
Deferred Revenue
YoY Change
Short-Term Debt	$133.0M	$185.0M	$185.0M
YoY Change	14.66%	-9.76%
Long-Term Debt Due
YoY Change
Total Short-Term Liabilities	$133.0M	$185.0M	$185.0M
YoY Change	301.23%	456.74%	456.74%
LONG-TERM LIABILITIES
Long-Term Debt	$124.6M	$124.5M	$124.5M
YoY Change	0.25%	67.78%	67.78%
Other Long-Term Liabilities	$198.5M	$183.6M	$183.6M
YoY Change	53.38%	22.6%	22.6%
Total Long-Term Liabilities	$323.1M	$308.2M	$308.2M
YoY Change	27.35%	37.57%	37.57%
TOTAL LIABILITIES
Total Short-Term Liabilities	$133.0M	$185.0M	$185.0M
Total Long-Term Liabilities	$323.1M	$308.2M	$308.2M
Total Liabilities	$5.853B	$5.706B	$5.706B
YoY Change	5.57%	5.83%	5.83%
SHAREHOLDERS EQUITY
Retained Earnings	$448.8M	$451.7M
YoY Change	4.74%	7.2%
Common Stock	$161.0K	$161.0K
YoY Change	0.0%	0.0%
Preferred Stock
YoY Change
Treasury Stock (at cost)	$18.85M	$20.24M
YoY Change	-11.01%	-9.37%
Treasury Stock Shares
Shareholders Equity	$445.7M	$454.8M	$454.8M
YoY Change
Total Liabilities & Shareholders Equity	$6.299B	$6.161B	$6.161B
YoY Change	5.56%	6.27%	6.27%

Cashflow Statement

Concept	2024 Q1	2023 Q4	2023
OPERATING ACTIVITIES
Net Income	$1.705M	$9.415M	$48.81M
YoY Change	-85.9%	-19.69%	-13.73%
Depreciation, Depletion And Amortization	$2.027M	$1.991M	$8.091M
YoY Change	-1.98%	-4.0%	-0.26%
Cash From Operating Activities	$12.29M	-$47.71M	$10.89M
YoY Change	87.29%	-395.48%	-91.84%
INVESTING ACTIVITIES
Capital Expenditures	$1.174M	$1.292M	$2.992M
YoY Change	38.44%	-52.64%	-64.25%
Acquisitions			$0.00
YoY Change
Other Investing Activities	-$24.99M	-$25.70M	$0.00
YoY Change	-84.74%	-83.63%
Cash From Investing Activities	-$26.16M	-$26.99M	-$310.1M
YoY Change	-84.1%	-83.1%	-4.63%
FINANCING ACTIVITIES
Cash Dividend Paid	$4.982M
YoY Change	3.55%
Common Stock Issuance & Retirement, Net
YoY Change
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	126.5M	6.972M	293.2M
YoY Change	-24.5%	-95.51%	20.68%
NET CHANGE
Cash From Operating Activities	12.29M	-47.71M	10.89M
Cash From Investing Activities	-26.16M	-26.99M	-310.1M
Cash From Financing Activities	126.5M	6.972M	293.2M
Net Change In Cash	112.6M	-67.72M	-6.024M
YoY Change	1084.22%	-669.83%	-111.73%
FREE CASH FLOW
Cash From Operating Activities	$12.29M	-$47.71M	$10.89M
Capital Expenditures	$1.174M	$1.292M	$2.992M
Free Cash Flow	$11.12M	-$49.00M	$7.902M
YoY Change	94.54%	-465.19%	-93.69%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value
CY2023	dei	Entity Central Index Key EntityCentralIndexKey	0000862831
CY2023	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	FY
CY2023	dei	Amendment Flag AmendmentFlag	false
CY2023Q4	us-gaap	Commitments And Contingencies CommitmentsAndContingencies
CY2022Q4	us-gaap	Commitments And Contingencies CommitmentsAndContingencies
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CY2023Q4	us-gaap	Operating Lease Liability Statement Of Financial Position Extensible List OperatingLeaseLiabilityStatementOfFinancialPositionExtensibleList	http://fasb.org/us-gaap/2023#OtherLiabilities
CY2022Q4	us-gaap	Operating Lease Liability Statement Of Financial Position Extensible List OperatingLeaseLiabilityStatementOfFinancialPositionExtensibleList	http://fasb.org/us-gaap/2023#OtherLiabilities
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CY2021	us-gaap	Defined Benefit Plan Net Periodic Benefit Cost Credit Excluding Service Cost Statement Of Income Or Comprehensive Income Extensible List DefinedBenefitPlanNetPeriodicBenefitCostCreditExcludingServiceCostStatementOfIncomeOrComprehensiveIncomeExtensibleList	http://fasb.org/us-gaap/2023#LaborAndRelatedExpense
CY2022	us-gaap	Defined Benefit Plan Net Periodic Benefit Cost Credit Excluding Service Cost Statement Of Income Or Comprehensive Income Extensible List DefinedBenefitPlanNetPeriodicBenefitCostCreditExcludingServiceCostStatementOfIncomeOrComprehensiveIncomeExtensibleList	http://fasb.org/us-gaap/2023#LaborAndRelatedExpense
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CY2023	dei	Document Type DocumentType	10-K
CY2023	dei	Document Annual Report DocumentAnnualReport	true
CY2023	dei	Document Period End Date DocumentPeriodEndDate	2023-12-31
CY2023	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-31
CY2023	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2023
CY2023	dei	Document Transition Report DocumentTransitionReport	false
CY2023	dei	Entity File Number EntityFileNumber	000-26481
CY2023	dei	Entity Registrant Name EntityRegistrantName	Financial Institutions, Inc.
CY2023	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	NY
CY2023	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	16-0816610
CY2023	dei	Entity Address Address Line1 EntityAddressAddressLine1	220 LIBERTY STREET
CY2023	dei	Entity Address City Or Town EntityAddressCityOrTown	WARSAW
CY2023	dei	Entity Address State Or Province EntityAddressStateOrProvince	NY
CY2023	dei	Entity Address Postal Zip Code EntityAddressPostalZipCode	14569
CY2023	dei	City Area Code CityAreaCode	585
CY2023	dei	Local Phone Number LocalPhoneNumber	786-1100
CY2023	dei	Security12b Title Security12bTitle	Common stock, par value $0.01 per share
CY2023	dei	Trading Symbol TradingSymbol	FISI
CY2023	dei	Security Exchange Name SecurityExchangeName	NASDAQ
CY2023	dei	Entity Well Known Seasoned Issuer EntityWellKnownSeasonedIssuer	No
CY2023	dei	Entity Voluntary Filers EntityVoluntaryFilers	No
CY2023	dei	Entity Current Reporting Status EntityCurrentReportingStatus	Yes
CY2023	dei	Entity Interactive Data Current EntityInteractiveDataCurrent	Yes
CY2023	dei	Entity Filer Category EntityFilerCategory	Accelerated Filer
CY2023	dei	Entity Small Business EntitySmallBusiness	false
CY2023	dei	Entity Emerging Growth Company EntityEmergingGrowthCompany	false
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CY2023	dei	Auditor Firm AuditorFirmId	49
CY2023	dei	Auditor Name AuditorName	RSM US LLP
CY2023	dei	Auditor Location AuditorLocation	Chicago, Illinois
CY2023	dei	Auditor Name AuditorName	RSM US LLP
CY2023	dei	Auditor Location AuditorLocation	Chicago, Illinois
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CY2022Q4	us-gaap	Cash And Due From Banks CashAndDueFromBanks	130466000
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CY2023Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	39902000
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CY2022Q4	us-gaap	Noninterest Bearing Deposit Liabilities NoninterestBearingDepositLiabilities	1139214000
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CY2021	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	71000
CY2023	us-gaap	Gain Loss On Sale Of Other Assets GainLossOnSaleOfOtherAssets	-6000
CY2022	us-gaap	Gain Loss On Sale Of Other Assets GainLossOnSaleOfOtherAssets	-16000
CY2021	us-gaap	Gain Loss On Sale Of Other Assets GainLossOnSaleOfOtherAssets	441000
CY2023	fisi	Gain Loss On Tax Credit Investments GainLossOnTaxCreditInvestments	-252000
CY2022	fisi	Gain Loss On Tax Credit Investments GainLossOnTaxCreditInvestments	-815000
CY2021	fisi	Gain Loss On Tax Credit Investments GainLossOnTaxCreditInvestments	-431000
CY2023	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	5286000
CY2022	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	4678000
CY2021	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	4246000
CY2023	us-gaap	Noninterest Income NoninterestIncome	48244000
CY2022	us-gaap	Noninterest Income NoninterestIncome	46271000
CY2021	us-gaap	Noninterest Income NoninterestIncome	46906000
CY2023	us-gaap	Labor And Related Expense LaborAndRelatedExpense	71889000
CY2022	us-gaap	Labor And Related Expense LaborAndRelatedExpense	69633000
CY2021	us-gaap	Labor And Related Expense LaborAndRelatedExpense	60893000
CY2023	us-gaap	Occupancy Net OccupancyNet	14798000
CY2022	us-gaap	Occupancy Net OccupancyNet	15103000
CY2021	us-gaap	Occupancy Net OccupancyNet	14371000
CY2023	us-gaap	Professional Fees ProfessionalFees	5259000
CY2022	us-gaap	Professional Fees ProfessionalFees	5592000
CY2021	us-gaap	Professional Fees ProfessionalFees	6535000
CY2023	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	20110000
CY2022	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	17638000
CY2021	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	14112000
CY2023	us-gaap	Supplies And Postage Expense SuppliesAndPostageExpense	1873000
CY2022	us-gaap	Supplies And Postage Expense SuppliesAndPostageExpense	1943000
CY2021	us-gaap	Supplies And Postage Expense SuppliesAndPostageExpense	1769000
CY2023	us-gaap	Federal Deposit Insurance Corporation Premium Expense FederalDepositInsuranceCorporationPremiumExpense	4902000
CY2022	us-gaap	Federal Deposit Insurance Corporation Premium Expense FederalDepositInsuranceCorporationPremiumExpense	2440000
CY2021	us-gaap	Federal Deposit Insurance Corporation Premium Expense FederalDepositInsuranceCorporationPremiumExpense	2624000
CY2023	us-gaap	Marketing And Advertising Expense MarketingAndAdvertisingExpense	1926000
CY2022	us-gaap	Marketing And Advertising Expense MarketingAndAdvertisingExpense	2013000
CY2021	us-gaap	Marketing And Advertising Expense MarketingAndAdvertisingExpense	1704000
CY2023	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	910000
CY2022	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	986000
CY2021	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	1060000
CY2023	us-gaap	Restructuring Charges RestructuringCharges	114000
CY2022	us-gaap	Restructuring Charges RestructuringCharges	1619000
CY2021	us-gaap	Restructuring Charges RestructuringCharges	111000
CY2023	us-gaap	Other Noninterest Expense OtherNoninterestExpense	15444000
CY2022	us-gaap	Other Noninterest Expense OtherNoninterestExpense	12395000
CY2021	us-gaap	Other Noninterest Expense OtherNoninterestExpense	9571000
CY2023	us-gaap	Noninterest Expense NoninterestExpense	137225000
CY2022	us-gaap	Noninterest Expense NoninterestExpense	129362000
CY2021	us-gaap	Noninterest Expense NoninterestExpense	112750000
CY2023	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	63053000
CY2022	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	70970000
CY2021	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	97222000
CY2023	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	12789000
CY2022	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	14397000
CY2021	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	19525000
CY2023	us-gaap	Net Income Loss NetIncomeLoss	50264000
CY2022	us-gaap	Net Income Loss NetIncomeLoss	56573000
CY2021	us-gaap	Net Income Loss NetIncomeLoss	77697000
CY2023	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	1459000
CY2022	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	1459000
CY2021	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	1460000
CY2023	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	48805000
CY2022	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	55114000
CY2021	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	76237000
CY2023	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	3.17
CY2022	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	3.58
CY2021	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	4.81
CY2023	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	3.15
CY2022	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	3.56
CY2021	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	4.78
CY2023	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.2
CY2022	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.16
CY2021	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.08
CY2023	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	15376000
CY2022	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	15384000
CY2021	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	15841000
CY2023	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	15475000
CY2022	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	15471000
CY2021	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	15937000
CY2023	us-gaap	Net Income Loss NetIncomeLoss	50264000
CY2022	us-gaap	Net Income Loss NetIncomeLoss	56573000
CY2021	us-gaap	Net Income Loss NetIncomeLoss	77697000
CY2023	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	16728000
CY2022	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	-123663000
CY2021	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	-19714000
CY2023	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax	-824000
CY2022	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax	3575000
CY2021	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax	1476000
CY2023	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-1642000
CY2022	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	4192000
CY2021	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-2903000
CY2023	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	17546000
CY2022	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-124280000
CY2021	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-15335000
CY2023	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	67810000
CY2022	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	-67707000
CY2021	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	62362000
CY2020Q4	us-gaap	Stockholders Equity StockholdersEquity	468363000
CY2021	us-gaap	Net Income Loss NetIncomeLoss	77697000
CY2021	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-15335000
CY2021	us-gaap	Stock Issued During Period Value New Issues StockIssuedDuringPeriodValueNewIssues	301000
CY2021	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	9235000
CY2021	us-gaap	Stock Repurchased During Period Value StockRepurchasedDuringPeriodValue	43000
CY2021	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	1743000
CY2021	us-gaap	Stock Granted During Period Value Sharebased Compensation StockGrantedDuringPeriodValueSharebasedCompensation	191000
CY2021	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.08
CY2021	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	17080000
CY2021Q4	us-gaap	Stockholders Equity StockholdersEquity	505142000
CY2022	us-gaap	Net Income Loss NetIncomeLoss	56573000
CY2022	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-124280000
CY2022	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	15340000
CY2022	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	2551000
CY2022	us-gaap	Stock Granted During Period Value Sharebased Compensation StockGrantedDuringPeriodValueSharebasedCompensation	199000
CY2022	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.16
CY2022	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	17781000
CY2022Q4	us-gaap	Stockholders Equity StockholdersEquity	405605000
CY2023	us-gaap	Net Income Loss NetIncomeLoss	50264000
CY2023	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	17546000
CY2023	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	571000
CY2023	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	1674000
CY2023	us-gaap	Stock Granted During Period Value Sharebased Compensation StockGrantedDuringPeriodValueSharebasedCompensation	195000
CY2023	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.2
CY2023	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	18458000
CY2023Q4	us-gaap	Stockholders Equity StockholdersEquity	454796000
CY2023	us-gaap	Profit Loss ProfitLoss	50264000
CY2022	us-gaap	Profit Loss ProfitLoss	56573000
CY2021	us-gaap	Profit Loss ProfitLoss	77697000
CY2023	us-gaap	Depreciation And Amortization DepreciationAndAmortization	8091000
CY2022	us-gaap	Depreciation And Amortization DepreciationAndAmortization	8112000
CY2021	us-gaap	Depreciation And Amortization DepreciationAndAmortization	8049000
CY2023	us-gaap	Accretion Amortization Of Discounts And Premiums Investments AccretionAmortizationOfDiscountsAndPremiumsInvestments	-3466000
CY2022	us-gaap	Accretion Amortization Of Discounts And Premiums Investments AccretionAmortizationOfDiscountsAndPremiumsInvestments	-4970000
CY2021	us-gaap	Accretion Amortization Of Discounts And Premiums Investments AccretionAmortizationOfDiscountsAndPremiumsInvestments	-5493000
CY2023	fisi	Provision For Credit Losses ProvisionForCreditLosses	13681000
CY2022	fisi	Provision For Credit Losses ProvisionForCreditLosses	13311000
CY2021	fisi	Provision For Credit Losses ProvisionForCreditLosses	-8336000
CY2023	us-gaap	Share Based Compensation ShareBasedCompensation	1674000
CY2022	us-gaap	Share Based Compensation ShareBasedCompensation	2551000
CY2021	us-gaap	Share Based Compensation ShareBasedCompensation	1743000
CY2023	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-1348000
CY2022	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-4382000
CY2021	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	5218000
CY2023	us-gaap	Proceeds From Sale Of Loans Held For Sale ProceedsFromSaleOfLoansHeldForSale	19316000
CY2022	us-gaap	Proceeds From Sale Of Loans Held For Sale ProceedsFromSaleOfLoansHeldForSale	31556000
CY2021	us-gaap	Proceeds From Sale Of Loans Held For Sale ProceedsFromSaleOfLoansHeldForSale	81334000
CY2023	us-gaap	Payments For Origination And Purchases Of Loans Held For Sale PaymentsForOriginationAndPurchasesOfLoansHeldForSale	19570000
CY2022	us-gaap	Payments For Origination And Purchases Of Loans Held For Sale PaymentsForOriginationAndPurchasesOfLoansHeldForSale	24677000
CY2021	us-gaap	Payments For Origination And Purchases Of Loans Held For Sale PaymentsForOriginationAndPurchasesOfLoansHeldForSale	80281000
CY2023	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	12106000
CY2022	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	5542000
CY2021	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	2947000
CY2023	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	566000
CY2022	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	1227000
CY2021	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	2950000
CY2023	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	-3576000
CY2022	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	-15000
CY2021	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	71000
CY2023	us-gaap	Gain Loss On Sale Of Other Assets GainLossOnSaleOfOtherAssets	-6000
CY2022	us-gaap	Gain Loss On Sale Of Other Assets GainLossOnSaleOfOtherAssets	-16000
CY2021	us-gaap	Gain Loss On Sale Of Other Assets GainLossOnSaleOfOtherAssets	441000
CY2023	us-gaap	Restructuring Costs RestructuringCosts	114000
CY2022	us-gaap	Restructuring Costs RestructuringCosts	1619000
CY2021	us-gaap	Restructuring Costs RestructuringCosts	392000
CY2023	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	56076000
CY2022	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	29902000
CY2021	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	9342000
CY2023	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	372000
CY2022	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	80580000
CY2021	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	-2596000
CY2023	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	10894000
CY2022	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	133573000
CY2021	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	72962000
CY2023	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	51472000
CY2022	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	75269000
CY2021	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	784064000
CY2023	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	3145000
CY2022	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	38551000
CY2021	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	18425000
CY2023	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	83412000
CY2022	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	122591000
CY2021	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	150919000
CY2023	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	43601000
CY2022	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	54479000
CY2021	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	83684000
CY2023	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	50515000
CY2022	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	6252000
CY2021	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	51891000
CY2023	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	420234000
CY2022	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	376251000
CY2021	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	90058000
CY2023	us-gaap	Payments To Acquire Life Insurance Policies PaymentsToAcquireLifeInsurancePolicies	53655000
CY2022	us-gaap	Payments To Acquire Life Insurance Policies PaymentsToAcquireLifeInsurancePolicies	35564000
CY2021	us-gaap	Payments To Acquire Life Insurance Policies PaymentsToAcquireLifeInsurancePolicies	20056000
CY2023	us-gaap	Proceeds From Life Insurance Policies ProceedsFromLifeInsurancePolicies	43880000
CY2022	us-gaap	Proceeds From Life Insurance Policies ProceedsFromLifeInsurancePolicies	25522000
CY2021	us-gaap	Proceeds From Life Insurance Policies ProceedsFromLifeInsurancePolicies	0
CY2023	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	0
CY2022	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	0
CY2021	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	-3510000
CY2023	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	2992000
CY2022	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	8369000
CY2021	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	9403000
CY2023	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	0
CY2022	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	0
CY2021	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	1420000
CY2023	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-310090000
CY2022	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-325160000
CY2021	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-633422000
CY2023	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	283488000
CY2022	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	102334000
CY2021	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	548723000
CY2023	us-gaap	Proceeds From Repayments Of Short Term Debt ProceedsFromRepaymentsOfShortTermDebt	-20000000
CY2022	us-gaap	Proceeds From Repayments Of Short Term Debt ProceedsFromRepaymentsOfShortTermDebt	175000000
CY2021	us-gaap	Proceeds From Repayments Of Short Term Debt ProceedsFromRepaymentsOfShortTermDebt	24700000
CY2023	us-gaap	Payments For Repurchase Of Preferred Stock And Preference Stock PaymentsForRepurchaseOfPreferredStockAndPreferenceStock	0
CY2022	us-gaap	Payments For Repurchase Of Preferred Stock And Preference Stock PaymentsForRepurchaseOfPreferredStockAndPreferenceStock	0
CY2021	us-gaap	Payments For Repurchase Of Preferred Stock And Preference Stock PaymentsForRepurchaseOfPreferredStockAndPreferenceStock	43000
CY2023	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	50000000
CY2022	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	0
CY2021	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	0
CY2023	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	571000
CY2022	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	15340000
CY2021	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	9235000
CY2023	us-gaap	Payments Of Dividends Preferred Stock And Preference Stock PaymentsOfDividendsPreferredStockAndPreferenceStock	1459000
CY2022	us-gaap	Payments Of Dividends Preferred Stock And Preference Stock PaymentsOfDividendsPreferredStockAndPreferenceStock	1459000
CY2021	us-gaap	Payments Of Dividends Preferred Stock And Preference Stock PaymentsOfDividendsPreferredStockAndPreferenceStock	1460000
CY2023	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	18286000
CY2022	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	17594000
CY2021	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	16991000
CY2023	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	293172000
CY2022	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	242941000
CY2021	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	545694000
CY2023	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	-6024000
CY2022	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	51354000
CY2021	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	-14766000
CY2022Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Including Disposal Group And Discontinued Operations CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations	130466000
CY2021Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Including Disposal Group And Discontinued Operations CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations	79112000
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Including Disposal Group And Discontinued Operations CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations	93878000
CY2023Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Including Disposal Group And Discontinued Operations CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations	124442000
CY2022Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Including Disposal Group And Discontinued Operations CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations	130466000
CY2021Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Including Disposal Group And Discontinued Operations CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations	79112000
CY2023	us-gaap	Use Of Estimates UseOfEstimates	<p style="margin-left:3.333%;font-size:10pt;margin-top:6pt;font-family:Times New Roman;margin-bottom:0;text-align:justify;"><span style="color:#000000;white-space:pre-wrap;font-weight:bold;font-size:10pt;font-family:Times New Roman;font-style:italic;min-width:fit-content;">(b.) Use of Estimates</span></p><p style="margin-left:3.333%;font-size:10pt;margin-top:6pt;font-family:Times New Roman;margin-bottom:0;text-align:justify;"><span style="color:#000000;white-space:pre-wrap;font-size:10pt;font-family:Times New Roman;min-width:fit-content;">In preparing the consolidated financial statements in conformity with GAAP, management is required to make estimates and assumptions that affect the reported amount of assets and liabilities as of the date of the statement of financial condition and reported amounts of revenue and expenses during the reporting period. Material estimates relate to the determination of the allowance for credit losses, the carrying value of goodwill and deferred tax assets, and assumptions used in the defined benefit pension plan accounting. These estimates and assumptions are based on management’s best estimates and judgment and are evaluated on an ongoing basis using historical experience and other factors, including the current economic environment. The Company adjusts these estimates and assumptions when facts and circumstances dictate. As future events cannot be determined with precision, actual results could differ significantly from the Company’s estimates.</span></p>
CY2023	us-gaap	Interest Paid Net InterestPaidNet	133847000
CY2022	us-gaap	Interest Paid Net InterestPaidNet	32571000
CY2021	us-gaap	Interest Paid Net InterestPaidNet	14709000
CY2023	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	6298000
CY2022	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	3398000
CY2021	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	10832000
CY2023	us-gaap	Transfer To Other Real Estate TransferToOtherRealEstate	142000
CY2022	us-gaap	Transfer To Other Real Estate TransferToOtherRealEstate	19000
CY2021	us-gaap	Transfer To Other Real Estate TransferToOtherRealEstate	0
CY2023Q4	us-gaap	Dividends Payable Current And Noncurrent DividendsPayableCurrentAndNoncurrent	4982000
CY2022Q4	us-gaap	Dividends Payable Current And Noncurrent DividendsPayableCurrentAndNoncurrent	4811000
CY2021Q4	us-gaap	Dividends Payable Current And Noncurrent DividendsPayableCurrentAndNoncurrent	4624000
CY2023	us-gaap	Stock Issued During Period Value Acquisitions StockIssuedDuringPeriodValueAcquisitions	0
CY2022	us-gaap	Stock Issued During Period Value Acquisitions StockIssuedDuringPeriodValueAcquisitions	0
CY2021	us-gaap	Stock Issued During Period Value Acquisitions StockIssuedDuringPeriodValueAcquisitions	301000
CY2023	us-gaap	Fair Value Of Assets Acquired FairValueOfAssetsAcquired	0
CY2022	us-gaap	Fair Value Of Assets Acquired FairValueOfAssetsAcquired	0
CY2021	us-gaap	Fair Value Of Assets Acquired FairValueOfAssetsAcquired	712000
CY2023	fisi	Days Past Due When Loans Are Generally Charged Off In Full In Days DaysPastDueWhenLoansAreGenerallyChargedOffInFullInDays	P120D
CY2023	fisi	Number Of Identified Portfolio Segments NumberOfIdentifiedPortfolioSegments	6
CY2023	fisi	Number Of Designated Segments NumberOfDesignatedSegments	6
CY2023	fisi	Days Past Due When Loans Are Generally Placed On Nonaccrual Status In Days DaysPastDueWhenLoansAreGenerallyPlacedOnNonaccrualStatusInDays	P90D
CY2023Q4	us-gaap	Other Real Estate OtherRealEstate	142000
CY2022Q4	us-gaap	Other Real Estate OtherRealEstate	19000
CY2023Q4	us-gaap	Federal Home Loan Bank Stock FederalHomeLoanBankStock	11000000
CY2022Q4	us-gaap	Federal Home Loan Bank Stock FederalHomeLoanBankStock	13000000
CY2023Q4	us-gaap	Federal Reserve Bank Stock FederalReserveBankStock	6400000
CY2022Q4	us-gaap	Federal Reserve Bank Stock FederalReserveBankStock	6400000
CY2023Q4	us-gaap	Investment Related Liabilities InvestmentRelatedLiabilities	14000000
CY2022Q4	us-gaap	Investment Related Liabilities InvestmentRelatedLiabilities	4800000
CY2023	us-gaap	Prior Period Reclassification Adjustment Description PriorPeriodReclassificationAdjustmentDescription	<p style="margin-left:3.333%;font-size:10pt;margin-top:6pt;font-family:Times New Roman;margin-bottom:0;text-align:justify;"><span style="color:#000000;white-space:pre-wrap;font-weight:bold;font-size:10pt;font-family:Times New Roman;font-style:italic;min-width:fit-content;">(x.) Reclassifications</span></p><p style="margin-left:3.333%;font-size:10pt;margin-top:6pt;font-family:Times New Roman;margin-bottom:0;text-align:justify;"><span style="color:#000000;white-space:pre-wrap;font-size:10pt;font-family:Times New Roman;min-width:fit-content;">Certain items in prior financial statements have been reclassified to conform to the current presentation. These reclassifications did not result in any changes to previously reported net income or shareholders’ equity.</span></p>
CY2020Q3	fisi	Number Of Bank Branch Closure NumberOfBankBranchClosure	6
CY2020Q3	fisi	Percentage Of Branch Network PercentageOfBranchNetwork	0.10
CY2020Q3	fisi	Percentage Of Branch Network Impact PercentageOfBranchNetworkImpact	0.06
CY2020Q4	fisi	Number Of Additional Branches Planned To Close NumberOfAdditionalBranchesPlannedToClose	1
CY2020	fisi	Pre Tax Expense Related Branch Closures PreTaxExpenseRelatedBranchClosures	1700000
CY2023	fisi	Valuation Adjustments On Restructuring Charges ValuationAdjustmentsOnRestructuringCharges	200000
CY2022	fisi	Valuation Adjustments On Restructuring Charges ValuationAdjustmentsOnRestructuringCharges	1600000
CY2023Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Loss HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss	11164000
CY2023	us-gaap	Restructuring Costs And Asset Impairment Charges RestructuringCostsAndAssetImpairmentCharges	114000
CY2022	us-gaap	Restructuring Costs And Asset Impairment Charges RestructuringCostsAndAssetImpairmentCharges	1619000
CY2021	us-gaap	Restructuring Costs And Asset Impairment Charges RestructuringCostsAndAssetImpairmentCharges	122000
CY2020Q4	us-gaap	Restructuring Reserve RestructuringReserve	1245000
CY2021	us-gaap	Restructuring Costs And Asset Impairment Charges RestructuringCostsAndAssetImpairmentCharges	122000
CY2021	us-gaap	Payments For Restructuring PaymentsForRestructuring	192000
CY2021	us-gaap	Restructuring Reserve Period Increase Decrease RestructuringReservePeriodIncreaseDecrease	730000
CY2021Q4	us-gaap	Restructuring Reserve RestructuringReserve	445000
CY2022	us-gaap	Restructuring Costs And Asset Impairment Charges RestructuringCostsAndAssetImpairmentCharges	1619000
CY2022	us-gaap	Payments For Restructuring PaymentsForRestructuring	59000
CY2022	us-gaap	Restructuring Reserve Period Increase Decrease RestructuringReservePeriodIncreaseDecrease	1703000
CY2022Q4	us-gaap	Restructuring Reserve RestructuringReserve	302000
CY2023	us-gaap	Restructuring Costs And Asset Impairment Charges RestructuringCostsAndAssetImpairmentCharges	114000
CY2023	us-gaap	Other Restructuring Costs OtherRestructuringCosts	82000
CY2023	us-gaap	Payments For Restructuring PaymentsForRestructuring	53000
CY2023	us-gaap	Restructuring Reserve Period Increase Decrease RestructuringReservePeriodIncreaseDecrease	200000
CY2023Q4	us-gaap	Restructuring Reserve RestructuringReserve	245000
CY2023	us-gaap	Impairment Of Long Lived Assets Held For Use ImpairmentOfLongLivedAssetsHeldForUse	629000
CY2022	us-gaap	Impairment Of Long Lived Assets Held For Use ImpairmentOfLongLivedAssetsHeldForUse	1500000
CY2023	fisi	Gain Loss On Sale Of Long Lived Assets Held For Sale GainLossOnSaleOfLongLivedAssetsHeldForSale	44000
CY2023Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	1037990000
CY2023Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	1286000
CY2023Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	151546000
CY2023Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	887730000
CY2023Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	148160000
CY2023Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Gain HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain	34000
CY2023Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	137030000
CY2023Q4	fisi	Allowance For Credit Losses Amortized Cost AllowanceForCreditLossesAmortizedCost	-4000
CY2023Q4	fisi	Held To Maturity Securities Net HeldToMaturitySecuritiesNet	148156000
CY2022Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	1127057000
CY2022Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	338000
CY2022Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	173024000
CY2022Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	954371000
CY2022Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	188980000
CY2022Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Gain HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain	24000
CY2022Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Loss HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss	14816000
CY2022Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	174188000
CY2022Q4	fisi	Allowance For Credit Losses Amortized Cost AllowanceForCreditLossesAmortizedCost	-5000
CY2022Q4	fisi	Held To Maturity Securities Net HeldToMaturitySecuritiesNet	188975000
CY2023Q4	fisi	Debt Securities Available For Sale And Held To Maturity Restricted DebtSecuritiesAvailableForSaleAndHeldToMaturityRestricted	845200000
CY2022Q4	fisi	Debt Securities Available For Sale And Held To Maturity Restricted DebtSecuritiesAvailableForSaleAndHeldToMaturityRestricted	850400000
CY2023	us-gaap	Interest Income Securities Taxable InterestIncomeSecuritiesTaxable	22048000
CY2022	us-gaap	Interest Income Securities Taxable InterestIncomeSecuritiesTaxable	22498000
CY2021	us-gaap	Interest Income Securities Taxable InterestIncomeSecuritiesTaxable	16736000
CY2023	us-gaap	Interest Income Securities Tax Exempt InterestIncomeSecuritiesTaxExempt	1575000
CY2022	us-gaap	Interest Income Securities Tax Exempt InterestIncomeSecuritiesTaxExempt	2043000
CY2021	us-gaap	Interest Income Securities Tax Exempt InterestIncomeSecuritiesTaxExempt	2355000
CY2023	us-gaap	Interest And Dividend Income Securities InterestAndDividendIncomeSecurities	23623000
CY2022	us-gaap	Interest And Dividend Income Securities InterestAndDividendIncomeSecurities	24541000
CY2021	us-gaap	Interest And Dividend Income Securities InterestAndDividendIncomeSecurities	19091000
CY2023	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	50515000
CY2022	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	6252000
CY2021	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	51891000
CY2023	us-gaap	Debt Securities Available For Sale Realized Gain DebtSecuritiesAvailableForSaleRealizedGain	0
CY2022	us-gaap	Debt Securities Available For Sale Realized Gain DebtSecuritiesAvailableForSaleRealizedGain	0
CY2021	us-gaap	Debt Securities Available For Sale Realized Gain DebtSecuritiesAvailableForSaleRealizedGain	251000
CY2023	us-gaap	Debt Securities Available For Sale Realized Loss DebtSecuritiesAvailableForSaleRealizedLoss	3576000
CY2022	us-gaap	Debt Securities Available For Sale Realized Loss DebtSecuritiesAvailableForSaleRealizedLoss	15000
CY2021	us-gaap	Debt Securities Available For Sale Realized Loss DebtSecuritiesAvailableForSaleRealizedLoss	180000
CY2023Q4	us-gaap	Available For Sale Securities Debt Maturities Within One Year Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost	37000
CY2023Q4	us-gaap	Available For Sale Securities Debt Maturities Within One Year Fair Value AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue	36000
CY2023Q4	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost	41028000
CY2023Q4	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	37505000
CY2023Q4	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost	133978000
CY2023Q4	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	119497000
CY2023Q4	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost	862947000
CY2023Q4	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue	730692000
CY2023Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	1037990000
CY2023Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	887730000
CY2023Q4	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount	26357000
CY2023Q4	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Fair Value HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearFairValue	26202000
CY2023Q4	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsNetCarryingAmount	30785000
CY2023Q4	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	30100000
CY2023Q4	us-gaap	Held To Maturity Securities Debt Maturities After Five Through Ten Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsNetCarryingAmount	30028000
CY2023Q4	us-gaap	Held To Maturity Securities Debt Maturities After Five Through Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	27140000
CY2023Q4	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsNetCarryingAmount	60990000
CY2023Q4	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsFairValue	53588000
CY2023Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	148160000
CY2023Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	137030000
CY2023Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months	8000
CY2023Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	0
CY2023Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger	835522000
CY2023Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	151546000
CY2023Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position DebtSecuritiesAvailableForSaleUnrealizedLossPosition	835530000
CY2023Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position Accumulated Loss DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss	151546000
CY2023Q4	fisi	Investment Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value InvestmentSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue	8000
CY2023Q4	fisi	Investment Securities Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss InvestmentSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	0
CY2023Q4	fisi	Investment Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value InvestmentSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue	835522000
CY2023Q4	fisi	Investment Securities Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss InvestmentSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	151546000
CY2023Q4	fisi	Investment Securities Continuous Unrealized Loss Position Fair Value InvestmentSecuritiesContinuousUnrealizedLossPositionFairValue	835530000
CY2023Q4	fisi	Investment Securities Accumulated Unrecognized Holding Loss InvestmentSecuritiesAccumulatedUnrecognizedHoldingLoss	151546000
CY2022Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months	193800000
CY2022Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	17922000
CY2022Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger	760210000
CY2022Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	155102000
CY2022Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position DebtSecuritiesAvailableForSaleUnrealizedLossPosition	954010000
CY2022Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position Accumulated Loss DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss	173024000
CY2022Q4	fisi	Investment Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value InvestmentSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue	193800000
CY2022Q4	fisi	Investment Securities Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss InvestmentSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	17922000
CY2022Q4	fisi	Investment Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value InvestmentSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue	760210000
CY2022Q4	fisi	Investment Securities Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss InvestmentSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	155102000
CY2022Q4	fisi	Investment Securities Continuous Unrealized Loss Position Fair Value InvestmentSecuritiesContinuousUnrealizedLossPositionFairValue	954010000
CY2022Q4	fisi	Investment Securities Accumulated Unrecognized Holding Loss InvestmentSecuritiesAccumulatedUnrecognizedHoldingLoss	173024000
CY2023Q4	fisi	Investment Securities In Unrealized Loss Position Number Of Positions InvestmentSecuritiesInUnrealizedLossPositionNumberOfPositions	201
CY2022Q4	fisi	Investment Securities In Unrealized Loss Position Number Of Positions InvestmentSecuritiesInUnrealizedLossPositionNumberOfPositions	226
CY2023Q4	fisi	Investment Securities In Unrealized Loss Positions Twelve Months Or Longer Qualitative Disclosure Number Of Positions InvestmentSecuritiesInUnrealizedLossPositionsTwelveMonthsOrLongerQualitativeDisclosureNumberOfPositions	198
CY2023Q4	fisi	Investment Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value InvestmentSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue	835500000
CY2023Q4	fisi	Investment Securities Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss InvestmentSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	151500000
CY2023Q4	fisi	Investment Securities In Unrealized Loss Positions Less Than Twelve Months Qualitative Disclosure Number Of Positions InvestmentSecuritiesInUnrealizedLossPositionsLessThanTwelveMonthsQualitativeDisclosureNumberOfPositions	3
CY2023Q4	fisi	Investment Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value InvestmentSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue	8000
CY2022Q4	fisi	Investment Securities In Unrealized Loss Positions Twelve Months Or Longer Qualitative Disclosure Number Of Positions InvestmentSecuritiesInUnrealizedLossPositionsTwelveMonthsOrLongerQualitativeDisclosureNumberOfPositions	127
CY2022Q4	fisi	Investment Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value InvestmentSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue	760200000
CY2022Q4	fisi	Investment Securities Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss InvestmentSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	155100000
CY2022Q4	fisi	Investment Securities In Unrealized Loss Positions Less Than Twelve Months Qualitative Disclosure Number Of Positions InvestmentSecuritiesInUnrealizedLossPositionsLessThanTwelveMonthsQualitativeDisclosureNumberOfPositions	99
CY2022Q4	fisi	Investment Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value InvestmentSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue	193800000
CY2022Q4	fisi	Investment Securities Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss InvestmentSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	17900000
CY2023Q4	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	0
CY2023	us-gaap	Other Than Temporary Impairment Loss Debt Securities Available For Sale OtherThanTemporaryImpairmentLossDebtSecuritiesAvailableForSale	0
CY2023Q4	fisi	Residential Real Estate Mortgages Serviced For Others ResidentialRealEstateMortgagesServicedForOthers	269400000
CY2022Q4	fisi	Residential Real Estate Mortgages Serviced For Others ResidentialRealEstateMortgagesServicedForOthers	275300000
CY2023Q4	us-gaap	Escrow Deposit EscrowDeposit	4800000
CY2022Q4	us-gaap	Escrow Deposit EscrowDeposit	4800000
CY2022Q4	fisi	Mortgage Servicing Assets Before Valuation Allowance MortgageServicingAssetsBeforeValuationAllowance	1470000
CY2021Q4	fisi	Mortgage Servicing Assets Before Valuation Allowance MortgageServicingAssetsBeforeValuationAllowance	1518000
CY2020Q4	fisi	Mortgage Servicing Assets Before Valuation Allowance MortgageServicingAssetsBeforeValuationAllowance	1376000
CY2023	us-gaap	Servicing Asset At Fair Value Additions ServicingAssetAtFairValueAdditions	436000
CY2022	us-gaap	Servicing Asset At Fair Value Additions ServicingAssetAtFairValueAdditions	210000
CY2021	us-gaap	Servicing Asset At Fair Value Additions ServicingAssetAtFairValueAdditions	520000
CY2023	us-gaap	Amortization Of Mortgage Servicing Rights Ms Rs AmortizationOfMortgageServicingRightsMSRs	446000
CY2022	us-gaap	Amortization Of Mortgage Servicing Rights Ms Rs AmortizationOfMortgageServicingRightsMSRs	258000
CY2021	us-gaap	Amortization Of Mortgage Servicing Rights Ms Rs AmortizationOfMortgageServicingRightsMSRs	378000
CY2023Q4	fisi	Mortgage Servicing Assets Before Valuation Allowance MortgageServicingAssetsBeforeValuationAllowance	1460000
CY2022Q4	fisi	Mortgage Servicing Assets Before Valuation Allowance MortgageServicingAssetsBeforeValuationAllowance	1470000
CY2021Q4	fisi	Mortgage Servicing Assets Before Valuation Allowance MortgageServicingAssetsBeforeValuationAllowance	1518000
CY2023Q4	fisi	Mortgage Servicing Assets Valuation Allowance MortgageServicingAssetsValuationAllowance	78000
CY2022Q4	fisi	Mortgage Servicing Assets Valuation Allowance MortgageServicingAssetsValuationAllowance	0
CY2021Q4	fisi	Mortgage Servicing Assets Valuation Allowance MortgageServicingAssetsValuationAllowance	1000
CY2023Q4	fisi	Mortgage Servicing Assets Net Of Valuation Allowance MortgageServicingAssetsNetOfValuationAllowance	1382000
CY2022Q4	fisi	Mortgage Servicing Assets Net Of Valuation Allowance MortgageServicingAssetsNetOfValuationAllowance	1470000
CY2021Q4	fisi	Mortgage Servicing Assets Net Of Valuation Allowance MortgageServicingAssetsNetOfValuationAllowance	1517000
CY2023Q4	us-gaap	Loans And Leases Receivable Gross Carrying Amount LoansAndLeasesReceivableGrossCarryingAmount	4416251000
CY2023Q4	fisi	Loans And Leases Receivable Deferred Loan Fees Costs LoansAndLeasesReceivableDeferredLoanFeesCosts	-45888000
CY2023Q4	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	4462139000
CY2023Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	51082000
CY2023Q4	us-gaap	Loans And Leases Receivable Net Reported Amount LoansAndLeasesReceivableNetReportedAmount	4411057000
CY2022Q4	us-gaap	Loans And Leases Receivable Gross Carrying Amount LoansAndLeasesReceivableGrossCarryingAmount	3998718000
CY2022Q4	fisi	Loans And Leases Receivable Deferred Loan Fees Costs LoansAndLeasesReceivableDeferredLoanFeesCosts	-51731000
CY2022Q4	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	4050449000
CY2022Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	45413000
CY2022Q4	us-gaap	Loans And Leases Receivable Net Reported Amount LoansAndLeasesReceivableNetReportedAmount	4005036000
CY2023Q4	us-gaap	Loans And Leases Receivable Related Parties LoansAndLeasesReceivableRelatedParties	40000000
CY2022Q4	us-gaap	Loans And Leases Receivable Related Parties LoansAndLeasesReceivableRelatedParties	37800000
CY2023	us-gaap	Loans And Leases Receivable Related Parties Additions LoansAndLeasesReceivableRelatedPartiesAdditions	10700000
CY2023	us-gaap	Loans And Leases Receivable Related Parties Proceeds LoansAndLeasesReceivableRelatedPartiesProceeds	8500000
CY2023Q4	us-gaap	Financing Receivable Recorded Investment Nonaccrual Status FinancingReceivableRecordedInvestmentNonaccrualStatus	26639000
CY2023Q4	us-gaap	Notes Receivable Gross NotesReceivableGross	4416251000
CY2023Q4	us-gaap	Financing Receivable Nonaccrual No Allowance FinancingReceivableNonaccrualNoAllowance	21316000
CY2022Q4	us-gaap	Financing Receivable Recorded Investment Nonaccrual Status FinancingReceivableRecordedInvestmentNonaccrualStatus	10197000
CY2022Q4	us-gaap	Notes Receivable Gross NotesReceivableGross	3998718000
CY2022Q4	us-gaap	Financing Receivable Nonaccrual No Allowance FinancingReceivableNonaccrualNoAllowance	8185000
CY2023	us-gaap	Financing Receivable Nonaccrual Interest Income FinancingReceivableNonaccrualInterestIncome	0
CY2022	us-gaap	Financing Receivable Nonaccrual Interest Income FinancingReceivableNonaccrualInterestIncome	0
CY2021	us-gaap	Financing Receivable Nonaccrual Interest Income FinancingReceivableNonaccrualInterestIncome	0
CY2023	us-gaap	Interest Income Operating InterestIncomeOperating	589000
CY2022	us-gaap	Interest Income Operating InterestIncomeOperating	391000
CY2021	us-gaap	Interest Income Operating InterestIncomeOperating	211000
CY2023Q4	us-gaap	Notes Receivable Net NotesReceivableNet	935000
CY2023Q4	fisi	Financial Receivables Percentage Of Total Loans FinancialReceivablesPercentageOfTotalLoans	0
CY2023Q4	fisi	Collateral Dependent Loans On Business Assets CollateralDependentLoansOnBusinessAssets	8698000
CY2023Q4	fisi	Collateral Dependent Loans On Real Property CollateralDependentLoansOnRealProperty	31575000
CY2023Q4	fisi	Collateral Dependent Loans CollateralDependentLoans	40273000
CY2023Q4	fisi	Collateral Dependent Loan With Specific Reserve CollateralDependentLoanWithSpecificReserve	2757000
CY2022Q4	fisi	Collateral Dependent Loans On Business Assets CollateralDependentLoansOnBusinessAssets	147000
CY2022Q4	fisi	Collateral Dependent Loans On Real Property CollateralDependentLoansOnRealProperty	22585000
CY2022Q4	fisi	Collateral Dependent Loans CollateralDependentLoans	22732000
CY2022Q4	fisi	Collateral Dependent Loan With Specific Reserve CollateralDependentLoanWithSpecificReserve	1278000
CY2022Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	45413000
CY2023	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	20769000
CY2023	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	12225000
CY2023	fisi	Financing Receivable Allowance For Loan Losses Provision Credit FinancingReceivableAllowanceForLoanLossesProvisionCredit	14213000
CY2023Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	51082000
CY2021Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	39676000
CY2022	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	16720000
CY2022	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	11482000
CY2022	fisi	Financing Receivable Allowance For Loan Losses Provision Credit FinancingReceivableAllowanceForLoanLossesProvisionCredit	10975000
CY2022Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	45413000
CY2020Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	52420000
CY2021	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	13219000
CY2021	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	7459000
CY2021	fisi	Financing Receivable Allowance For Loan Losses Provision Credit FinancingReceivableAllowanceForLoanLossesProvisionCredit	-6984000
CY2021Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	39676000
CY2023Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	102989000
CY2022Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	101199000
CY2023Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	63087000
CY2022Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	59213000
CY2023Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	39902000
CY2022Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	41986000
CY2023Q2	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0
CY2023	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0
CY2022	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0
CY2021	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0
CY2021Q4	us-gaap	Goodwill Goodwill	67071000
CY2022	us-gaap	Goodwill Period Increase Decrease GoodwillPeriodIncreaseDecrease	0
CY2022Q4	us-gaap	Goodwill Goodwill	67071000
CY2023	us-gaap	Goodwill Period Increase Decrease GoodwillPeriodIncreaseDecrease	0
CY2022Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	31120000
CY2023Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	33788000
CY2022Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	33229000
CY2023Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P20Y7M6D
CY2023Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.0391
CY2023	us-gaap	Operating Lease Cost OperatingLeaseCost	3082000
CY2022	us-gaap	Operating Lease Cost OperatingLeaseCost	2885000
CY2023Q4	us-gaap	Goodwill Goodwill	67071000
CY2023Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Next Twelve Months FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths	838000
CY2023Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Two FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo	766000
CY2023Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Three FiniteLivedIntangibleAssetsAmortizationExpenseYearThree	694000
CY2023Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Four FiniteLivedIntangibleAssetsAmortizationExpenseYearFour	623000
CY2023Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Five FiniteLivedIntangibleAssetsAmortizationExpenseYearFive	551000
CY2023Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense After Year Five FiniteLivedIntangibleAssetsAmortizationExpenseAfterYearFive	1961000
CY2023Q4	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	5433000
CY2023	us-gaap	Lessee Operating Lease Description LesseeOperatingLeaseDescription	The Company is obligated under a number of non-cancellable operating lease agreements for land, buildings and equipment with terms, including renewal options reasonably certain to be exercised, extending through 2061.
CY2023	us-gaap	Lessee Operating Sublease Option To Extend LesseeOperatingSubleaseOptionToExtend	Two building leases were subleased with terms that extended through December 31, 2024.
CY2023	fisi	Number Of Buildings Subleased NumberOfBuildingsSubleased	2
CY2023Q4	fisi	Operating Lease Right Of Use Asset Gross OperatingLeaseRightOfUseAssetGross	38684000
CY2022Q4	fisi	Operating Lease Right Of Use Asset Gross OperatingLeaseRightOfUseAssetGross	36723000
CY2023Q4	fisi	Operating Lease Right Of Use Asset Accumulated Amortization OperatingLeaseRightOfUseAssetAccumulatedAmortization	7160000
CY2022Q4	fisi	Operating Lease Right Of Use Asset Accumulated Amortization OperatingLeaseRightOfUseAssetAccumulatedAmortization	5603000
CY2023Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	31524000
CY2021	us-gaap	Operating Lease Cost OperatingLeaseCost	2830000
CY2023	us-gaap	Variable Lease Cost VariableLeaseCost	406000
CY2022	us-gaap	Variable Lease Cost VariableLeaseCost	475000
CY2021	us-gaap	Variable Lease Cost VariableLeaseCost	427000
CY2023	us-gaap	Sublease Income SubleaseIncome	106000
CY2022	us-gaap	Sublease Income SubleaseIncome	69000
CY2021	us-gaap	Sublease Income SubleaseIncome	23000
CY2023	us-gaap	Lease Cost LeaseCost	3382000
CY2022	us-gaap	Lease Cost LeaseCost	3291000
CY2021	us-gaap	Lease Cost LeaseCost	3234000
CY2023	us-gaap	Operating Lease Payments OperatingLeasePayments	2963000
CY2022	us-gaap	Operating Lease Payments OperatingLeasePayments	2587000
CY2021	us-gaap	Operating Lease Payments OperatingLeasePayments	2647000
CY2023	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	2249000
CY2022	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	11006000
CY2021	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	4251000
CY2023Q4	us-gaap	Lessee Operating Lease Liability Payments Due Next Rolling Twelve Months LesseeOperatingLeaseLiabilityPaymentsDueNextRollingTwelveMonths	2984000
CY2023Q4	us-gaap	Lessee Operating Lease Liability Payments Due In Rolling Year Two LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearTwo	2887000
CY2023Q4	us-gaap	Lessee Operating Lease Liability Payments Due In Rolling Year Three LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearThree	2733000
CY2023Q4	us-gaap	Lessee Operating Lease Liability Payments Due In Rolling Year Four LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearFour	2703000
CY2023Q4	us-gaap	Lessee Operating Lease Liability Payments Due In Rolling Year Five LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearFive	2420000
CY2023Q4	us-gaap	Lessee Operating Lease Liability Payments Due After Rolling Year Five LesseeOperatingLeaseLiabilityPaymentsDueAfterRollingYearFive	37013000
CY2023Q4	us-gaap	Lessee Operating Lease Liability Payments Due LesseeOperatingLeaseLiabilityPaymentsDue	50740000
CY2023Q4	us-gaap	Lessee Operating Lease Liability Undiscounted Excess Amount LesseeOperatingLeaseLiabilityUndiscountedExcessAmount	16952000
CY2023Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	33788000
CY2023Q4	fisi	Tax Credit Investments TaxCreditInvestments	68253000
CY2022Q4	fisi	Tax Credit Investments TaxCreditInvestments	55568000
CY2023Q4	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	48733000
CY2022Q4	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	53427000
CY2023Q4	us-gaap	Derivative Fair Value Of Derivative Asset DerivativeFairValueOfDerivativeAsset	43506000
CY2022Q4	us-gaap	Derivative Fair Value Of Derivative Asset DerivativeFairValueOfDerivativeAsset	54557000
CY2023Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	31524000
CY2022Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	31120000
CY2023Q4	us-gaap	Federal Home Loan Bank Stock And Federal Reserve Bank Stock FederalHomeLoanBankStockAndFederalReserveBankStock	17406000
CY2022Q4	us-gaap	Federal Home Loan Bank Stock And Federal Reserve Bank Stock FederalHomeLoanBankStockAndFederalReserveBankStock	19385000
CY2023Q4	us-gaap	Interest Receivable InterestReceivable	24481000
CY2023Q4	us-gaap	Time Deposit Maturities After Year Five TimeDepositMaturitiesAfterYearFive	0
CY2022Q4	us-gaap	Time Deposit Maturities After Year Five TimeDepositMaturitiesAfterYearFive	0
CY2023Q4	us-gaap	Time Deposits TimeDeposits	1404696000
CY2022Q4	us-gaap	Time Deposits TimeDeposits	1282872000
CY2023Q4	us-gaap	Line Of Credit LineOfCredit	0
CY2022Q4	us-gaap	Interest Receivable InterestReceivable	19371000
CY2023Q4	us-gaap	Other Assets Miscellaneous OtherAssetsMiscellaneous	80454000
CY2022Q4	us-gaap	Other Assets Miscellaneous OtherAssetsMiscellaneous	29564000
CY2023Q4	us-gaap	Other Assets OtherAssets	314357000
CY2022Q4	us-gaap	Other Assets OtherAssets	262992000
CY2023Q4	us-gaap	Derivative Asset Fair Value Of Collateral DerivativeAssetFairValueOfCollateral	40350000
CY2022Q4	us-gaap	Derivative Asset Fair Value Of Collateral DerivativeAssetFairValueOfCollateral	54300000
CY2023Q4	us-gaap	Derivative Fair Value Of Derivative Liability DerivativeFairValueOfDerivativeLiability	37521000
CY2022Q4	us-gaap	Derivative Fair Value Of Derivative Liability DerivativeFairValueOfDerivativeLiability	47751000
CY2023Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	33788000
CY2022Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	33229000
CY2023Q4	us-gaap	Interest Payable Current And Noncurrent InterestPayableCurrentAndNoncurrent	19412000
CY2022Q4	us-gaap	Interest Payable Current And Noncurrent InterestPayableCurrentAndNoncurrent	5983000
CY2023Q4	fisi	Other Liabilities Miscellaneous OtherLiabilitiesMiscellaneous	52570000
CY2022Q4	fisi	Other Liabilities Miscellaneous OtherLiabilitiesMiscellaneous	41758000
CY2023Q4	us-gaap	Other Liabilities OtherLiabilities	183641000
CY2022Q4	us-gaap	Other Liabilities OtherLiabilities	183021000
CY2023Q4	us-gaap	Other Receivables OtherReceivables	37900000
CY2023Q4	us-gaap	Noninterest Bearing Deposit Liabilities NoninterestBearingDepositLiabilities	1010614000
CY2022Q4	us-gaap	Noninterest Bearing Deposit Liabilities NoninterestBearingDepositLiabilities	1139214000
CY2023Q4	us-gaap	Interest Bearing Deposit Liabilities InterestBearingDepositLiabilities	713158000
CY2022Q4	us-gaap	Interest Bearing Deposit Liabilities InterestBearingDepositLiabilities	863822000
CY2023Q4	us-gaap	Deposits Savings Deposits DepositsSavingsDeposits	2084444000
CY2022Q4	us-gaap	Deposits Savings Deposits DepositsSavingsDeposits	1643516000
CY2023Q4	us-gaap	Time Deposit Maturities Year One TimeDepositMaturitiesYearOne	1310495000
CY2022Q4	us-gaap	Time Deposit Maturities Year One TimeDepositMaturitiesYearOne	1238202000
CY2023Q4	us-gaap	Time Deposit Maturities Year Two TimeDepositMaturitiesYearTwo	79684000
CY2022Q4	us-gaap	Time Deposit Maturities Year Two TimeDepositMaturitiesYearTwo	35046000
CY2023Q4	us-gaap	Time Deposit Maturities Year Three TimeDepositMaturitiesYearThree	12391000
CY2022Q4	us-gaap	Time Deposit Maturities Year Three TimeDepositMaturitiesYearThree	4952000
CY2023Q4	us-gaap	Time Deposit Maturities Year Four TimeDepositMaturitiesYearFour	1634000
CY2022Q4	us-gaap	Time Deposit Maturities Year Four TimeDepositMaturitiesYearFour	3386000
CY2023Q4	us-gaap	Time Deposit Maturities Year Five TimeDepositMaturitiesYearFive	492000
CY2022Q4	us-gaap	Time Deposit Maturities Year Five TimeDepositMaturitiesYearFive	1286000
CY2023Q4	us-gaap	Deposits Deposits	5212912000
CY2022Q4	us-gaap	Deposits Deposits	4929424000
CY2023Q4	us-gaap	Deposit Liability Uninsured DepositLiabilityUninsured	1820000000
CY2023Q4	fisi	Percentage Of Deposit Liability Uninsured PercentageOfDepositLiabilityUninsured	0.35
CY2022Q4	us-gaap	Deposit Liability Uninsured DepositLiabilityUninsured	1290000000
CY2022Q4	fisi	Percentage Of Deposit Liability Uninsured PercentageOfDepositLiabilityUninsured	0.26
CY2023Q4	us-gaap	Time Deposits At Or Above Fdic Insurance Limit TimeDepositsAtOrAboveFDICInsuranceLimit	302600000
CY2022Q4	us-gaap	Time Deposits At Or Above Fdic Insurance Limit TimeDepositsAtOrAboveFDICInsuranceLimit	258700000
CY2023	us-gaap	Interest Expense Demand Deposit Accounts InterestExpenseDemandDepositAccounts	7127000
CY2022	us-gaap	Interest Expense Demand Deposit Accounts InterestExpenseDemandDepositAccounts	2180000
CY2021	us-gaap	Interest Expense Demand Deposit Accounts InterestExpenseDemandDepositAccounts	1156000
CY2023	us-gaap	Interest Expense Savings Deposits InterestExpenseSavingsDeposits	41424000
CY2022	us-gaap	Interest Expense Savings Deposits InterestExpenseSavingsDeposits	9778000
CY2021	us-gaap	Interest Expense Savings Deposits InterestExpenseSavingsDeposits	3363000
CY2023	us-gaap	Interest Expense Time Deposits InterestExpenseTimeDeposits	58810000
CY2022	us-gaap	Interest Expense Time Deposits InterestExpenseTimeDeposits	11036000
CY2021	us-gaap	Interest Expense Time Deposits InterestExpenseTimeDeposits	3599000
CY2023	us-gaap	Interest Expense Deposits InterestExpenseDeposits	107361000
CY2022	us-gaap	Interest Expense Deposits InterestExpenseDeposits	22994000
CY2021	us-gaap	Interest Expense Deposits InterestExpenseDeposits	8118000
CY2023Q4	us-gaap	Short Term Borrowings ShortTermBorrowings	185000000
CY2022Q4	us-gaap	Short Term Borrowings ShortTermBorrowings	205000000
CY2023Q4	us-gaap	Federal Home Loan Bank Advances Long Term FederalHomeLoanBankAdvancesLongTerm	50000000
CY2022Q4	us-gaap	Federal Home Loan Bank Advances Long Term FederalHomeLoanBankAdvancesLongTerm	0
CY2023Q4	us-gaap	Subordinated Debt SubordinatedDebt	74532000
CY2022Q4	us-gaap	Subordinated Debt SubordinatedDebt	74222000
CY2023Q4	us-gaap	Long Term Debt LongTermDebt	124532000
CY2022Q4	us-gaap	Long Term Debt LongTermDebt	74222000
CY2023Q4	us-gaap	Debt Longterm And Shortterm Combined Amount DebtLongtermAndShorttermCombinedAmount	309532000
CY2022Q4	us-gaap	Debt Longterm And Shortterm Combined Amount DebtLongtermAndShorttermCombinedAmount	279222000
CY2023Q2	us-gaap	Short Term Debt Lender ShortTermDebtLender	FRB
CY2023Q4	us-gaap	Short Term Debt Weighted Average Interest Rate ShortTermDebtWeightedAverageInterestRate	0.0529
CY2022Q4	us-gaap	Short Term Debt Weighted Average Interest Rate ShortTermDebtWeightedAverageInterestRate	0.046
CY2022Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	16099556
CY2020Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	16099556
CY2021Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	16099556
CY2022Q2	us-gaap	Stock Repurchase Program Number Of Shares Authorized To Be Repurchased StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased	766447
CY2023	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	0
CY2020Q4	us-gaap	Stock Repurchase Program Number Of Shares Authorized To Be Repurchased StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased	801879
CY2022Q4	us-gaap	Line Of Credit LineOfCredit	0
CY2023	us-gaap	Debt Instrument Maturity Date DebtInstrumentMaturityDate	2026-01-20
CY2023Q4	us-gaap	Interest Rate Cash Flow Hedge Gain Loss To Be Reclassified During Next12 Months Net InterestRateCashFlowHedgeGainLossToBeReclassifiedDuringNext12MonthsNet	2600000
CY2023Q4	us-gaap	Capital Units Authorized CapitalUnitsAuthorized	50210000
CY2023Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	50000000
CY2023Q4	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	0.01
CY2023Q4	us-gaap	Preferred Stock Shares Authorized PreferredStockSharesAuthorized	210000
CY2023Q4	us-gaap	Preferred Stock Par Or Stated Value Per Share PreferredStockParOrStatedValuePerShare	100
CY2023Q4	us-gaap	Preferred Stock Shares Outstanding PreferredStockSharesOutstanding	172921
CY2023Q4	us-gaap	Preferred Stock Shares Issued PreferredStockSharesIssued	172921
CY2022Q4	us-gaap	Preferred Stock Shares Outstanding PreferredStockSharesOutstanding	172921
CY2022Q4	us-gaap	Preferred Stock Shares Issued PreferredStockSharesIssued	172921
CY2022Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	16099556
CY2023Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	16099556
CY2021Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	16099556
CY2022	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-3250000
CY2021	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	4384000
CY2023	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	-212000
CY2022	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	-1132000
CY2022Q1	us-gaap	Stock Repurchased During Period Shares StockRepurchasedDuringPeriodShares	461191
CY2022Q1	us-gaap	Treasury Stock Acquired Average Cost Per Share TreasuryStockAcquiredAverageCostPerShare	31.99
CY2021	us-gaap	Stock Repurchased During Period Shares StockRepurchasedDuringPeriodShares	340688
CY2021	us-gaap	Treasury Stock Acquired Average Cost Per Share TreasuryStockAcquiredAverageCostPerShare	26.44
CY2023	us-gaap	Other Comprehensive Income Loss Before Tax Portion Attributable To Parent OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent	23590000
CY2023	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	6044000
CY2023	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	17546000
CY2022	us-gaap	Other Comprehensive Income Loss Before Tax Portion Attributable To Parent OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent	-167092000
CY2022	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	-42812000
CY2022	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-124280000
CY2021	us-gaap	Other Comprehensive Income Loss Before Tax Portion Attributable To Parent OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent	-20617000
CY2021	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	-5282000
CY2021	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-15335000
CY2023	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Expiration Period SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod	P10Y
CY2023	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross	0
CY2022	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross	0
CY2021	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross	0
CY2023Q4	us-gaap	Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized	0
CY2021	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	834000
CY2023	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-1348000
CY2022	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-4382000
CY2021	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	5218000
CY2023	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	12789000
CY2022	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	14397000
CY2021	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	19525000
CY2023	us-gaap	Share Based Compensation ShareBasedCompensation	1674000
CY2022	us-gaap	Share Based Compensation ShareBasedCompensation	2551000
CY2021	us-gaap	Share Based Compensation ShareBasedCompensation	1743000
CY2023	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	444000
CY2022	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	486000
CY2021	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	265000
CY2023	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	13302000
CY2022	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	15371000
CY2021	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	11453000
CY2023	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	835000
CY2022	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	3408000
CY2021	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	2854000
CY2023	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	14137000
CY2022	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	18779000
CY2021	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	14307000
CY2023	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-1136000
CY2023	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.21
CY2022	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.21
CY2021	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.21
CY2023	us-gaap	Effective Income Tax Rate Reconciliation Tax Exempt Income EffectiveIncomeTaxRateReconciliationTaxExemptIncome	-0.008
CY2022	us-gaap	Effective Income Tax Rate Reconciliation Tax Exempt Income EffectiveIncomeTaxRateReconciliationTaxExemptIncome	-0.009
CY2021	us-gaap	Effective Income Tax Rate Reconciliation Tax Exempt Income EffectiveIncomeTaxRateReconciliationTaxExemptIncome	-0.007
CY2023	fisi	Effective Income Tax Rate Reconciliation Tax Credit And Adjustments Percent EffectiveIncomeTaxRateReconciliationTaxCreditAndAdjustmentsPercent	-0.021
CY2022	fisi	Effective Income Tax Rate Reconciliation Tax Credit And Adjustments Percent EffectiveIncomeTaxRateReconciliationTaxCreditAndAdjustmentsPercent	-0.026
CY2021	fisi	Effective Income Tax Rate Reconciliation Tax Credit And Adjustments Percent EffectiveIncomeTaxRateReconciliationTaxCreditAndAdjustmentsPercent	-0.026
CY2023	fisi	Effective Income Tax Rate Reconciliation Non Taxable Earnings On Company Owned Life Insurance EffectiveIncomeTaxRateReconciliationNonTaxableEarningsOnCompanyOwnedLifeInsurance	0.009
CY2022	fisi	Effective Income Tax Rate Reconciliation Non Taxable Earnings On Company Owned Life Insurance EffectiveIncomeTaxRateReconciliationNonTaxableEarningsOnCompanyOwnedLifeInsurance	0
CY2021	fisi	Effective Income Tax Rate Reconciliation Non Taxable Earnings On Company Owned Life Insurance EffectiveIncomeTaxRateReconciliationNonTaxableEarningsOnCompanyOwnedLifeInsurance	-0.006
CY2023	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.008
CY2022	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.025
CY2021	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.03
CY2023	us-gaap	Effective Income Tax Rate Reconciliation Nondeductible Expense EffectiveIncomeTaxRateReconciliationNondeductibleExpense	0.003
CY2022	us-gaap	Effective Income Tax Rate Reconciliation Nondeductible Expense EffectiveIncomeTaxRateReconciliationNondeductibleExpense	0.002
CY2021	us-gaap	Effective Income Tax Rate Reconciliation Nondeductible Expense EffectiveIncomeTaxRateReconciliationNondeductibleExpense	0
CY2023	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	0.002
CY2022	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	0.001
CY2021	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	0
CY2023	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.203
CY2022	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.203
CY2021	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.201
CY2023	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	12789000
CY2022	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	14397000
CY2021	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	19525000
CY2023	us-gaap	Income Tax Effects Allocated Directly To Equity IncomeTaxEffectsAllocatedDirectlyToEquity	6044000
CY2022	us-gaap	Income Tax Effects Allocated Directly To Equity IncomeTaxEffectsAllocatedDirectlyToEquity	-42812000
CY2021	us-gaap	Income Tax Effects Allocated Directly To Equity IncomeTaxEffectsAllocatedDirectlyToEquity	-5282000
CY2023Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Allowance For Doubtful Accounts DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAllowanceForDoubtfulAccounts	14011000
CY2022Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Allowance For Doubtful Accounts DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAllowanceForDoubtfulAccounts	12695000
CY2023Q4	fisi	Deferred Tax Assets Leases Right Of Use Obligations DeferredTaxAssetsLeasesRightOfUseObligations	8657000
CY2022Q4	fisi	Deferred Tax Assets Leases Right Of Use Obligations DeferredTaxAssetsLeasesRightOfUseObligations	8505000
CY2023Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Employee Compensation DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeCompensation	1471000
CY2022Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Employee Compensation DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeCompensation	1615000
CY2023Q4	us-gaap	Deferred Tax Assets Equity Method Investments DeferredTaxAssetsEquityMethodInvestments	785000
CY2022Q4	us-gaap	Deferred Tax Assets Equity Method Investments DeferredTaxAssetsEquityMethodInvestments	1381000
CY2023Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Employee Benefits DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeBenefits	92000
CY2022Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Employee Benefits DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeBenefits	179000
CY2023Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Share Based Compensation Cost DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost	930000
CY2022Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Share Based Compensation Cost DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost	975000
CY2023Q4	fisi	Net Unrealized Loss On Securities Available For Sales NetUnrealizedLossOnSecuritiesAvailableForSales	38549000
CY2022Q4	fisi	Net Unrealized Loss On Securities Available For Sales NetUnrealizedLossOnSecuritiesAvailableForSales	44312000
CY2023Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Pensions DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsPensions	297000
CY2022Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Pensions DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsPensions	229000
CY2023Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	1395000
CY2022Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	1206000
CY2023Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	66187000
CY2022Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	71097000
CY2023Q4	us-gaap	Deferred Tax Liabilities Leasing Arrangements DeferredTaxLiabilitiesLeasingArrangements	8077000
CY2022Q4	us-gaap	Deferred Tax Liabilities Leasing Arrangements DeferredTaxLiabilitiesLeasingArrangements	7964000
CY2023Q4	us-gaap	Deferred Tax Liabilities Prepaid Expenses DeferredTaxLiabilitiesPrepaidExpenses	929000
CY2022Q4	us-gaap	Deferred Tax Liabilities Prepaid Expenses DeferredTaxLiabilitiesPrepaidExpenses	637000
CY2023Q4	us-gaap	Deferred Tax Liabilities Goodwill And Intangible Assets Intangible Assets DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsIntangibleAssets	2760000
CY2022Q4	us-gaap	Deferred Tax Liabilities Goodwill And Intangible Assets Intangible Assets DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsIntangibleAssets	2580000
CY2023Q4	fisi	Deferred Tax Liabilities Depreciation And Amortization DeferredTaxLiabilitiesDepreciationAndAmortization	3833000
CY2022Q4	fisi	Deferred Tax Liabilities Depreciation And Amortization DeferredTaxLiabilitiesDepreciationAndAmortization	4080000
CY2023Q4	us-gaap	Deferred Tax Liabilities Mortgage Servicing Rights DeferredTaxLiabilitiesMortgageServicingRights	354000
CY2022Q4	us-gaap	Deferred Tax Liabilities Mortgage Servicing Rights DeferredTaxLiabilitiesMortgageServicingRights	377000
CY2023Q4	fisi	Deferred Loan Origination Costs DeferredLoanOriginationCosts	154000
CY2022Q4	fisi	Deferred Loan Origination Costs DeferredLoanOriginationCosts	401000
CY2023Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	1347000
CY2022Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	1631000
CY2023Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	17454000
CY2022Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	17670000
CY2023Q4	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	48733000
CY2022Q4	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	53427000
CY2023Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	0
CY2022Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	0
CY2023	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Expense UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense	0
CY2022	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Expense UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense	0
CY2021	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Expense UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense	0
CY2023Q4	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Accrued UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued	0
CY2022Q4	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Accrued UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued	0
CY2023	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	48805000
CY2022	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	55114000
CY2021	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	76237000
CY2023	us-gaap	Weighted Average Number Of Shares Issued Basic WeightedAverageNumberOfSharesIssuedBasic	16100000
CY2022	us-gaap	Weighted Average Number Of Shares Issued Basic WeightedAverageNumberOfSharesIssuedBasic	16100000
CY2021	us-gaap	Weighted Average Number Of Shares Issued Basic WeightedAverageNumberOfSharesIssuedBasic	16100000
CY2023	us-gaap	Weighted Average Number Of Shares Restricted Stock WeightedAverageNumberOfSharesRestrictedStock	8000
CY2022	us-gaap	Weighted Average Number Of Shares Restricted Stock WeightedAverageNumberOfSharesRestrictedStock	5000
CY2021	us-gaap	Weighted Average Number Of Shares Restricted Stock WeightedAverageNumberOfSharesRestrictedStock	5000
CY2023	us-gaap	Weighted Average Number Of Shares Treasury Stock WeightedAverageNumberOfSharesTreasuryStock	716000
CY2022	us-gaap	Weighted Average Number Of Shares Treasury Stock WeightedAverageNumberOfSharesTreasuryStock	711000
CY2021	us-gaap	Weighted Average Number Of Shares Treasury Stock WeightedAverageNumberOfSharesTreasuryStock	254000
CY2023	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	15376000
CY2022	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	15384000
CY2021	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	15841000
CY2023	fisi	Incremental Common Shares Attributable To Vesting Of Restricted Stock Awards IncrementalCommonSharesAttributableToVestingOfRestrictedStockAwards	99000
CY2022	fisi	Incremental Common Shares Attributable To Vesting Of Restricted Stock Awards IncrementalCommonSharesAttributableToVestingOfRestrictedStockAwards	87000
CY2021	fisi	Incremental Common Shares Attributable To Vesting Of Restricted Stock Awards IncrementalCommonSharesAttributableToVestingOfRestrictedStockAwards	96000
CY2023	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	15475000
CY2022	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	15471000
CY2021	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	15937000
CY2023	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	3.17
CY2022	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	3.58
CY2021	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	4.81
CY2023	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	3.15
CY2022	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	3.56
CY2021	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	4.78
CY2023	us-gaap	Incremental Common Shares Attributable To Participating Nonvested Shares With Non Forfeitable Dividend Rights IncrementalCommonSharesAttributableToParticipatingNonvestedSharesWithNonForfeitableDividendRights	0
CY2022	us-gaap	Incremental Common Shares Attributable To Participating Nonvested Shares With Non Forfeitable Dividend Rights IncrementalCommonSharesAttributableToParticipatingNonvestedSharesWithNonForfeitableDividendRights	0
CY2021	us-gaap	Incremental Common Shares Attributable To Participating Nonvested Shares With Non Forfeitable Dividend Rights IncrementalCommonSharesAttributableToParticipatingNonvestedSharesWithNonForfeitableDividendRights	0
CY2022Q4	us-gaap	Defined Benefit Plan Pension Plans With Accumulated Benefit Obligations In Excess Of Plan Assets Aggregate Projected Benefit Obligation DefinedBenefitPlanPensionPlansWithAccumulatedBenefitObligationsInExcessOfPlanAssetsAggregateProjectedBenefitObligation	0
CY2021Q4	us-gaap	Defined Benefit Plan Pension Plans With Accumulated Benefit Obligations In Excess Of Plan Assets Aggregate Projected Benefit Obligation DefinedBenefitPlanPensionPlansWithAccumulatedBenefitObligationsInExcessOfPlanAssetsAggregateProjectedBenefitObligation	0
CY2023Q4	us-gaap	Defined Benefit Plan Pension Plans With Accumulated Benefit Obligations In Excess Of Plan Assets Aggregate Projected Benefit Obligation DefinedBenefitPlanPensionPlansWithAccumulatedBenefitObligationsInExcessOfPlanAssetsAggregateProjectedBenefitObligation	0
CY2022Q4	us-gaap	Defined Benefit Plan Benefit Obligation DefinedBenefitPlanBenefitObligation	74172000
CY2021Q4	us-gaap	Defined Benefit Plan Benefit Obligation DefinedBenefitPlanBenefitObligation	97682000
CY2023	us-gaap	Defined Benefit Plan Service Cost DefinedBenefitPlanServiceCost	1788000
CY2022	us-gaap	Defined Benefit Plan Service Cost DefinedBenefitPlanServiceCost	3485000
CY2023	us-gaap	Defined Benefit Plan Service Cost DefinedBenefitPlanServiceCost	1788000
CY2022	us-gaap	Defined Benefit Plan Service Cost DefinedBenefitPlanServiceCost	3485000
CY2023	us-gaap	Defined Benefit Plan Interest Cost DefinedBenefitPlanInterestCost	3421000
CY2022	us-gaap	Defined Benefit Plan Interest Cost DefinedBenefitPlanInterestCost	2588000
CY2023	us-gaap	Defined Benefit Plan Actuarial Gain Loss DefinedBenefitPlanActuarialGainLoss	-3507000
CY2022	us-gaap	Defined Benefit Plan Actuarial Gain Loss DefinedBenefitPlanActuarialGainLoss	25055000
CY2023	us-gaap	Defined Benefit Plan Benefit Obligation Benefits Paid DefinedBenefitPlanBenefitObligationBenefitsPaid	4638000
CY2022	us-gaap	Defined Benefit Plan Benefit Obligation Benefits Paid DefinedBenefitPlanBenefitObligationBenefitsPaid	4528000
CY2023	fisi	Prior Year Service Costs Due To Plan Amendments PriorYearServiceCostsDueToPlanAmendments	-3905000
CY2022	fisi	Prior Year Service Costs Due To Plan Amendments PriorYearServiceCostsDueToPlanAmendments	0
CY2023Q4	us-gaap	Defined Benefit Plan Benefit Obligation DefinedBenefitPlanBenefitObligation	74345000
CY2022Q4	us-gaap	Defined Benefit Plan Benefit Obligation DefinedBenefitPlanBenefitObligation	74172000
CY2022Q4	us-gaap	Defined Benefit Plan Fair Value Of Plan Assets DefinedBenefitPlanFairValueOfPlanAssets	73276000
CY2021Q4	us-gaap	Defined Benefit Plan Fair Value Of Plan Assets DefinedBenefitPlanFairValueOfPlanAssets	104227000
CY2023	us-gaap	Defined Benefit Plan Actual Return On Plan Assets DefinedBenefitPlanActualReturnOnPlanAssets	4549000
CY2022	us-gaap	Defined Benefit Plan Actual Return On Plan Assets DefinedBenefitPlanActualReturnOnPlanAssets	-26422000
CY2023	us-gaap	Defined Benefit Plan Plan Assets Benefits Paid DefinedBenefitPlanPlanAssetsBenefitsPaid	4639000
CY2022	us-gaap	Defined Benefit Plan Plan Assets Benefits Paid DefinedBenefitPlanPlanAssetsBenefitsPaid	4529000
CY2023Q4	us-gaap	Defined Benefit Plan Fair Value Of Plan Assets DefinedBenefitPlanFairValueOfPlanAssets	73186000
CY2022Q4	us-gaap	Defined Benefit Plan Fair Value Of Plan Assets DefinedBenefitPlanFairValueOfPlanAssets	73276000
CY2023Q4	us-gaap	Defined Benefit Plan Funded Status Of Plan DefinedBenefitPlanFundedStatusOfPlan	-1159000
CY2022Q4	us-gaap	Defined Benefit Plan Funded Status Of Plan DefinedBenefitPlanFundedStatusOfPlan	-896000
CY2023Q4	us-gaap	Defined Benefit Plan Accumulated Benefit Obligation DefinedBenefitPlanAccumulatedBenefitObligation	73900000
CY2022Q4	us-gaap	Defined Benefit Plan Accumulated Benefit Obligation DefinedBenefitPlanAccumulatedBenefitObligation	70200000
CY2023Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Next Twelve Months DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths	4359000
CY2023Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Year Two DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo	4532000
CY2023Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Year Three DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree	4856000
CY2023Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Year Four DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour	4854000
CY2023Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Year Five DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive	5103000
CY2023Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Five Fiscal Years Thereafter DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter	26149000
CY2021	us-gaap	Defined Benefit Plan Service Cost DefinedBenefitPlanServiceCost	4196000
CY2023	us-gaap	Number Of Reportable Segments NumberOfReportableSegments	1
CY2023	us-gaap	Defined Benefit Plan Interest Cost DefinedBenefitPlanInterestCost	3421000
CY2022	us-gaap	Defined Benefit Plan Interest Cost DefinedBenefitPlanInterestCost	2588000
CY2021	us-gaap	Defined Benefit Plan Interest Cost DefinedBenefitPlanInterestCost	2202000
CY2023	us-gaap	Defined Benefit Plan Expected Return On Plan Assets DefinedBenefitPlanExpectedReturnOnPlanAssets	3511000
CY2022	us-gaap	Defined Benefit Plan Expected Return On Plan Assets DefinedBenefitPlanExpectedReturnOnPlanAssets	4565000
CY2021	us-gaap	Defined Benefit Plan Expected Return On Plan Assets DefinedBenefitPlanExpectedReturnOnPlanAssets	5225000
CY2023	us-gaap	Defined Benefit Plan Amortization Of Gains Losses DefinedBenefitPlanAmortizationOfGainsLosses	-1264000
CY2022	us-gaap	Defined Benefit Plan Amortization Of Gains Losses DefinedBenefitPlanAmortizationOfGainsLosses	-250000
CY2021	us-gaap	Defined Benefit Plan Amortization Of Gains Losses DefinedBenefitPlanAmortizationOfGainsLosses	-724000
CY2023	us-gaap	Defined Benefit Plan Amortization Of Prior Service Cost Credit DefinedBenefitPlanAmortizationOfPriorServiceCostCredit	-492000
CY2022	us-gaap	Defined Benefit Plan Amortization Of Prior Service Cost Credit DefinedBenefitPlanAmortizationOfPriorServiceCostCredit	0
CY2021	us-gaap	Defined Benefit Plan Amortization Of Prior Service Cost Credit DefinedBenefitPlanAmortizationOfPriorServiceCostCredit	0
CY2023	us-gaap	Defined Benefit Plan Net Periodic Benefit Cost DefinedBenefitPlanNetPeriodicBenefitCost	2470000
CY2022	us-gaap	Defined Benefit Plan Net Periodic Benefit Cost DefinedBenefitPlanNetPeriodicBenefitCost	1758000
CY2021	us-gaap	Defined Benefit Plan Net Periodic Benefit Cost DefinedBenefitPlanNetPeriodicBenefitCost	1897000
CY2023	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Discount Rate DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate	0.0498
CY2022	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Discount Rate DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate	0.027
CY2021	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Discount Rate DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate	0.0232
CY2023	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Rate Of Compensation Increase DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease	0.03
CY2022	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Rate Of Compensation Increase DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease	0.03
CY2021	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Rate Of Compensation Increase DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease	0.03
CY2023	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Expected Long Term Return On Assets DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets	0.06
CY2022	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Expected Long Term Return On Assets DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets	0.0525
CY2021	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Expected Long Term Return On Assets DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets	0.0525
CY2023Q4	us-gaap	Defined Benefit Plan Assumptions Used Calculating Benefit Obligation Discount Rate DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate	0.0478
CY2022Q4	us-gaap	Defined Benefit Plan Assumptions Used Calculating Benefit Obligation Discount Rate DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate	0.0498
CY2021Q4	us-gaap	Defined Benefit Plan Assumptions Used Calculating Benefit Obligation Discount Rate DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate	0.027
CY2023Q4	us-gaap	Defined Benefit Plan Assumptions Used Calculating Benefit Obligation Rate Of Compensation Increase DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease	0.04
CY2022Q4	us-gaap	Defined Benefit Plan Assumptions Used Calculating Benefit Obligation Rate Of Compensation Increase DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease	0.03
CY2021Q4	us-gaap	Defined Benefit Plan Assumptions Used Calculating Benefit Obligation Rate Of Compensation Increase DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease	0.03
CY2023	fisi	Investment Strategy Percentage In Long Term Growth InvestmentStrategyPercentageInLongTermGrowth	0.97
CY2023	fisi	Investment Strategy Percentage In Near Term Benefit Payments InvestmentStrategyPercentageInNearTermBenefitPayments	0.03
CY2023Q4	us-gaap	Cash Equivalents At Carrying Value CashEquivalentsAtCarryingValue	1202000
CY2023Q4	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	22714000
CY2023Q4	fisi	Fixed Income Securities FixedIncomeSecurities	26052000
CY2023Q4	us-gaap	Investments And Cash InvestmentsAndCash	73186000
CY2023Q4	us-gaap	Defined Benefit Plan Weighted Average Asset Allocations DefinedBenefitPlanWeightedAverageAssetAllocations	0.98
CY2022Q4	us-gaap	Cash Equivalents At Carrying Value CashEquivalentsAtCarryingValue	12156000
CY2022Q4	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	18356000
CY2022Q4	fisi	Fixed Income Securities FixedIncomeSecurities	15901000
CY2022Q4	us-gaap	Investments And Cash InvestmentsAndCash	73276000
CY2022Q4	us-gaap	Defined Benefit Plan Weighted Average Asset Allocations DefinedBenefitPlanWeightedAverageAssetAllocations	0.96
CY2023Q4	us-gaap	Pension And Other Postretirement And Postemployment Benefit Plans Liabilities Current And Noncurrent PensionAndOtherPostretirementAndPostemploymentBenefitPlansLiabilitiesCurrentAndNoncurrent	0
CY2022Q4	us-gaap	Pension And Other Postretirement And Postemployment Benefit Plans Liabilities Current And Noncurrent PensionAndOtherPostretirementAndPostemploymentBenefitPlansLiabilitiesCurrentAndNoncurrent	0
CY2023Q4	fisi	Fair Value Assets Level1 To Level2 Transfer Amount FairValueAssetsLevel1ToLevel2TransferAmount	0
CY2022Q4	fisi	Fair Value Assets Level1 To Level2 Transfer Amount FairValueAssetsLevel1ToLevel2TransferAmount	0
CY2022Q4	fisi	Fair Value Assets Level1 To Level2 Transfer Amount FairValueAssetsLevel1ToLevel2TransferAmount	0
CY2021Q4	fisi	Fair Value Assets Level1 To Level2 Transfer Amount FairValueAssetsLevel1ToLevel2TransferAmount	0
CY2023Q4	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Value FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue	0
CY2022Q4	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Value FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue	0
CY2023Q4	us-gaap	Goodwill Goodwill	67071000
CY2023Q4	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	5433000
CY2023Q4	us-gaap	Assets Assets	6160881000
CY2022Q4	us-gaap	Goodwill Goodwill	67071000
CY2022Q4	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	6343000
CY2022Q4	us-gaap	Assets Assets	5797272000
CY2023	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	165715000
CY2023	fisi	Provision Benefit For Credit Losses ProvisionBenefitForCreditLosses	13681000
CY2023	us-gaap	Noninterest Income NoninterestIncome	48244000
CY2023	us-gaap	Noninterest Expense NoninterestExpense	137225000
CY2023	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	63053000
CY2023	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	12789000
CY2023	us-gaap	Net Income Loss NetIncomeLoss	50264000
CY2022	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	167372000
CY2022	fisi	Provision Benefit For Credit Losses ProvisionBenefitForCreditLosses	13311000
CY2022	us-gaap	Noninterest Income NoninterestIncome	46271000
CY2022	us-gaap	Noninterest Expense NoninterestExpense	129362000
CY2022	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	70970000
CY2022	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	14397000
CY2022	us-gaap	Net Income Loss NetIncomeLoss	56573000
CY2021	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	154730000
CY2021	fisi	Provision Benefit For Credit Losses ProvisionBenefitForCreditLosses	-8336000
CY2021	us-gaap	Noninterest Income NoninterestIncome	46906000
CY2021	us-gaap	Noninterest Expense NoninterestExpense	112750000
CY2021	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	97222000
CY2021	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	19525000
CY2021	us-gaap	Net Income Loss NetIncomeLoss	77697000
CY2023Q4	ecd	Non Rule10b51 Arr Adopted Flag NonRule10b51ArrAdoptedFlag	false
CY2023Q4	ecd	Rule10b51 Arr Adopted Flag Rule10b51ArrAdoptedFlag	false
CY2023Q4	ecd	Rule10b51 Arr Trmntd Flag Rule10b51ArrTrmntdFlag	false
CY2023Q4	ecd	Non Rule10b51 Arr Trmntd Flag NonRule10b51ArrTrmntdFlag	false

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$FISI
FINANCIAL INSTITUTIONS INC Stock $fisi

2024 Q1 Form 10-K Financial Statement

#000095017024030754 Filed on March 13, 2024

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$FISI FINANCIAL INSTITUTIONS INC Stock $fisi

2024 Q1 Form 10-K Financial Statement

#000095017024030754 Filed on March 13, 2024

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$FISI
FINANCIAL INSTITUTIONS INC Stock $fisi