$FISI
FINANCIAL INSTITUTIONS INC Stock $fisi

$fisi Overview Financials Valuation SEC Filings Company Website

2021 Q4 Form 10-Q Financial Statement

#000095017021003405 Filed on November 08, 2021

Income Statement

Concept	2021 Q4	2021 Q3	2020 Q3
Revenue		$41.23M	$39.72M
YoY Change		3.8%	-6.45%
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	$1.980M	$2.140M	$1.970M
YoY Change	0.51%	8.63%	-4.37%
% of Gross Profit
Operating Expenses
YoY Change
Operating Profit
YoY Change
Interest Expense		$2.954M	$4.220M
YoY Change		-30.0%
% of Operating Profit
Other Income/Expense, Net
YoY Change
Pretax Income	$23.84M	$21.73M	$15.21M
YoY Change	53.91%	42.83%	-11.11%
Income Tax	$4.230M	$4.553M	$2.940M
% Of Pretax Income	17.74%	20.95%	19.33%
Net Earnings	$19.61M	$17.18M	$12.27M
YoY Change	42.1%	39.94%	-4.36%
Net Earnings / Revenue		41.66%	30.9%
Basic Earnings Per Share		$1.06	$0.74
Diluted Earnings Per Share	$1.231M	$1.05	$0.74
COMMON SHARES
Basic Shares Outstanding	15.84M	15.84M	16.03M
Diluted Shares Outstanding		15.94M	16.06M

Balance Sheet

Concept	2021 Q4	2021 Q3	2020 Q3
SHORT-TERM ASSETS
Cash & Short-Term Investments
YoY Change
Cash & Equivalents	$79.11M	$288.4M	$282.1M
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	$40.11M	$40.61M	$81.40M
YoY Change	-1.23%	-50.12%	28.8%
Goodwill	$67.07M	$67.07M	$66.06M
YoY Change	1.53%	1.53%	0.0%
Intangibles
YoY Change
Long-Term Investments
YoY Change
Other Assets
YoY Change
Total Long-Term Assets
YoY Change
TOTAL ASSETS
Total Short-Term Assets
Total Long-Term Assets
Total Assets	$5.521B	$5.623B	$4.959B
YoY Change	12.39%	13.39%	14.46%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable
YoY Change
Accrued Expenses	$23.90M	$24.20M	$21.90M
YoY Change	11.16%	10.5%	-6.01%
Deferred Revenue
YoY Change
Short-Term Debt	$30.00M
YoY Change	466.04%
Long-Term Debt Due
YoY Change
Total Short-Term Liabilities	$23.90M	$24.20M	$21.90M
YoY Change	11.16%	10.5%	-6.01%
LONG-TERM LIABILITIES
Long-Term Debt	$73.90M	$73.80M	$39.30M
YoY Change	0.41%	87.79%	0.0%
Other Long-Term Liabilities	$60.80M	$56.20M	$71.40M
YoY Change	-6.61%	-21.29%	78.5%
Total Long-Term Liabilities	$134.7M	$130.0M	$110.7M
YoY Change	-2.88%	17.43%	39.6%
TOTAL LIABILITIES
Total Short-Term Liabilities	$23.90M	$24.20M	$21.90M
Total Long-Term Liabilities	$134.7M	$130.0M	$110.7M
Total Liabilities	$5.016B	$5.129B	$4.503B
YoY Change	12.86%	13.91%	15.45%
SHAREHOLDERS EQUITY
Retained Earnings	$384.0M	$369.0M
YoY Change	18.21%
Common Stock	$161.0K	$161.0K
YoY Change	0.0%
Preferred Stock
YoY Change
Treasury Stock (at cost)	$9.216M	$6.128M
YoY Change	654.17%
Treasury Stock Shares	$354.1K	$257.5K
Shareholders Equity	$505.1M	$494.0M	$456.4M
YoY Change
Total Liabilities & Shareholders Equity	$5.521B	$5.623B	$4.959B
YoY Change	12.39%	13.39%	14.46%

Cashflow Statement

Concept	2021 Q4	2021 Q3	2020 Q3
OPERATING ACTIVITIES
Net Income	$19.61M	$17.18M	$12.27M
YoY Change	42.1%	39.94%	-4.36%
Depreciation, Depletion And Amortization	$1.980M	$2.140M	$1.970M
YoY Change	0.51%	8.63%	-4.37%
Cash From Operating Activities	$33.49M	$8.520M	$10.13M
YoY Change	44.6%	-15.89%	-15.79%
INVESTING ACTIVITIES
Capital Expenditures	-$1.040M	-$2.080M	-$420.0K
YoY Change	-28.77%	395.24%	-39.13%
Acquisitions
YoY Change
Other Investing Activities	-$116.0M	-$235.5M	-$113.6M
YoY Change	-24.2%	107.26%	-3130.13%
Cash From Investing Activities	-$117.0M	-$237.6M	-$114.1M
YoY Change	-24.24%	108.29%	-3827.45%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net
YoY Change
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	-125.8M	311.1M	266.4M
YoY Change	121.15%	16.78%	1990.97%
NET CHANGE
Cash From Operating Activities	33.49M	8.520M	10.13M
Cash From Investing Activities	-117.0M	-237.6M	-114.1M
Cash From Financing Activities	-125.8M	311.1M	266.4M
Net Change In Cash	-209.3M	82.04M	162.5M
YoY Change	11.23%	-49.5%	483.76%
FREE CASH FLOW
Cash From Operating Activities	$33.49M	$8.520M	$10.13M
Capital Expenditures	-$1.040M	-$2.080M	-$420.0K
Free Cash Flow	$34.53M	$10.60M	$10.55M
YoY Change	40.25%	0.47%	-17.06%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value
	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-31
	us-gaap	Restructuring Reserve Period Increase Decrease RestructuringReservePeriodIncreaseDecrease
	dei	Amendment Flag AmendmentFlag	false
CY2021Q3	us-gaap	Short Term Borrowings ShortTermBorrowings
CY2021Q3	us-gaap	Restructuring Costs RestructuringCosts
CY2019Q4	us-gaap	Restructuring Reserve RestructuringReserve
CY2020Q4	us-gaap	Operating Lease Liability Statement Of Financial Position Extensible List OperatingLeaseLiabilityStatementOfFinancialPositionExtensibleList	http://fasb.org/us-gaap/2021-01-31#OtherLiabilitiesMember
	us-gaap	Restructuring Costs RestructuringCosts
CY2020Q2	us-gaap	Restructuring Reserve RestructuringReserve
	us-gaap	Transfer To Other Real Estate TransferToOtherRealEstate
	us-gaap	Fair Value Of Assets Acquired FairValueOfAssetsAcquired
CY2021Q2	us-gaap	Stock Issued During Period Value Restricted Stock Award Gross StockIssuedDuringPeriodValueRestrictedStockAwardGross
	dei	Entity Central Index Key EntityCentralIndexKey	0000862831
	us-gaap	Restructuring Costs RestructuringCosts
CY2021Q3	us-gaap	Operating Lease Liability Statement Of Financial Position Extensible List OperatingLeaseLiabilityStatementOfFinancialPositionExtensibleList	http://fasb.org/us-gaap/2021-01-31#OtherLiabilitiesMember
	fisi	Noncash Restructuring Charges Against Assets NoncashRestructuringChargesAgainstAssets
CY2020Q4	us-gaap	Operating Lease Right Of Use Asset Statement Of Financial Position Extensible List OperatingLeaseRightOfUseAssetStatementOfFinancialPositionExtensibleList	http://fasb.org/us-gaap/2021-01-31#OtherAssetsMember
CY2021Q3	us-gaap	Restructuring Costs RestructuringCosts
	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	Q3
	us-gaap	Stock Issued1 StockIssued1
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	us-gaap	Payments For Repurchase Of Preferred Stock And Preference Stock PaymentsForRepurchaseOfPreferredStockAndPreferenceStock
CY2020Q3	us-gaap	Restructuring Reserve Period Increase Decrease RestructuringReservePeriodIncreaseDecrease
	dei	Document Type DocumentType	10-Q
	dei	Document Quarterly Report DocumentQuarterlyReport	true
	dei	Document Period End Date DocumentPeriodEndDate	2021-09-30
	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2021
	dei	Document Transition Report DocumentTransitionReport	false
	dei	Entity File Number EntityFileNumber	000-26481
	dei	Entity Registrant Name EntityRegistrantName	Financial Institutions, Inc.
	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	NY
	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	16-0816610
	dei	Entity Address Address Line1 EntityAddressAddressLine1	220 LIBERTY STREET
	dei	Entity Address City Or Town EntityAddressCityOrTown	WARSAW
	dei	Entity Address State Or Province EntityAddressStateOrProvince	NY
	dei	Entity Address Postal Zip Code EntityAddressPostalZipCode	14569
	dei	City Area Code CityAreaCode	585
	dei	Local Phone Number LocalPhoneNumber	786-1100
	dei	Security12b Title Security12bTitle	Common stock, par value $0.01 per share
	dei	Trading Symbol TradingSymbol	FISI
	dei	Security Exchange Name SecurityExchangeName	NASDAQ
	dei	Entity Current Reporting Status EntityCurrentReportingStatus	Yes
	dei	Entity Interactive Data Current EntityInteractiveDataCurrent	Yes
	dei	Entity Filer Category EntityFilerCategory	Accelerated Filer
	dei	Entity Small Business EntitySmallBusiness	false
	dei	Entity Emerging Growth Company EntityEmergingGrowthCompany	false
	dei	Entity Shell Company EntityShellCompany	false
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CY2021Q3	us-gaap	Gain Loss On Sale Of Other Assets GainLossOnSaleOfOtherAssets	138000
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	us-gaap	Gain Loss On Sale Of Other Assets GainLossOnSaleOfOtherAssets	286000
	us-gaap	Gain Loss On Sale Of Other Assets GainLossOnSaleOfOtherAssets	8000
CY2021Q3	fisi	Gain Loss On Tax Credit Investments GainLossOnTaxCreditInvestments	129000
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	fisi	Gain Loss On Tax Credit Investments GainLossOnTaxCreditInvestments	62000
	fisi	Gain Loss On Tax Credit Investments GainLossOnTaxCreditInvestments	-120000
CY2021Q3	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	1069000
CY2020Q3	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	1019000
	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	3094000
	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	3151000
CY2021Q3	us-gaap	Noninterest Income NoninterestIncome	12083000
CY2020Q3	us-gaap	Noninterest Income NoninterestIncome	12217000
	us-gaap	Noninterest Income NoninterestIncome	35232000
	us-gaap	Noninterest Income NoninterestIncome	31840000
CY2021Q3	us-gaap	Labor And Related Expense LaborAndRelatedExpense	15798000
CY2020Q3	us-gaap	Labor And Related Expense LaborAndRelatedExpense	15085000
	us-gaap	Labor And Related Expense LaborAndRelatedExpense	44782000
	us-gaap	Labor And Related Expense LaborAndRelatedExpense	45173000
CY2021Q3	us-gaap	Occupancy Net OccupancyNet	3834000
CY2020Q3	us-gaap	Occupancy Net OccupancyNet	3263000
	us-gaap	Occupancy Net OccupancyNet	10502000
	us-gaap	Occupancy Net OccupancyNet	10407000
CY2021Q3	us-gaap	Professional Fees ProfessionalFees	1600000
CY2020Q3	us-gaap	Professional Fees ProfessionalFees	1242000
	us-gaap	Professional Fees ProfessionalFees	5098000
	us-gaap	Professional Fees ProfessionalFees	4974000
CY2021Q3	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	3579000
CY2020Q3	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	3250000
	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	10160000
	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	8622000
CY2021Q3	us-gaap	Supplies And Postage Expense SuppliesAndPostageExpense	447000
CY2020Q3	us-gaap	Supplies And Postage Expense SuppliesAndPostageExpense	463000
	us-gaap	Supplies And Postage Expense SuppliesAndPostageExpense	1361000
	us-gaap	Supplies And Postage Expense SuppliesAndPostageExpense	1533000
CY2021Q3	us-gaap	Federal Deposit Insurance Corporation Premium Expense FederalDepositInsuranceCorporationPremiumExpense	697000
CY2020Q3	us-gaap	Federal Deposit Insurance Corporation Premium Expense FederalDepositInsuranceCorporationPremiumExpense	594000
	us-gaap	Federal Deposit Insurance Corporation Premium Expense FederalDepositInsuranceCorporationPremiumExpense	1942000
	us-gaap	Federal Deposit Insurance Corporation Premium Expense FederalDepositInsuranceCorporationPremiumExpense	1505000
CY2021Q3	us-gaap	Marketing And Advertising Expense MarketingAndAdvertisingExpense	474000
CY2020Q3	us-gaap	Marketing And Advertising Expense MarketingAndAdvertisingExpense	955000
	us-gaap	Marketing And Advertising Expense MarketingAndAdvertisingExpense	1234000
	us-gaap	Marketing And Advertising Expense MarketingAndAdvertisingExpense	2055000
CY2021Q3	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	264000
CY2020Q3	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	280000
	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	801000
	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	861000
CY2021Q3	us-gaap	Restructuring Charges RestructuringCharges	0
CY2020Q3	us-gaap	Restructuring Charges RestructuringCharges	1362000
	us-gaap	Restructuring Charges RestructuringCharges	0
	us-gaap	Restructuring Charges RestructuringCharges	1362000
CY2021Q3	us-gaap	Other Noninterest Expense OtherNoninterestExpense	2476000
CY2020Q3	us-gaap	Other Noninterest Expense OtherNoninterestExpense	1981000
	us-gaap	Other Noninterest Expense OtherNoninterestExpense	6973000
	us-gaap	Other Noninterest Expense OtherNoninterestExpense	6228000
CY2021Q3	us-gaap	Noninterest Expense NoninterestExpense	29169000
CY2020Q3	us-gaap	Noninterest Expense NoninterestExpense	28475000
	us-gaap	Noninterest Expense NoninterestExpense	82853000
	us-gaap	Noninterest Expense NoninterestExpense	82720000
CY2021Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	21728000
CY2020Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	15213000
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	73385000
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	30235000
CY2021Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	4553000
CY2020Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	2940000
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	15300000
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	5703000
CY2021Q3	us-gaap	Net Income Loss NetIncomeLoss	17175000
CY2020Q3	us-gaap	Net Income Loss NetIncomeLoss	12273000
	us-gaap	Net Income Loss NetIncomeLoss	58085000
	us-gaap	Net Income Loss NetIncomeLoss	24532000
CY2021Q3	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	364000
CY2020Q3	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	365000
	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	1095000
	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	1096000
CY2021Q3	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	16811000
CY2020Q3	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	11908000
	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	56990000
	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	23436000
CY2021Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.06
CY2020Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.74
	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	3.60
	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.46
CY2021Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.05
CY2020Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.74
	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	3.58
	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.46
CY2021Q3	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.27
CY2020Q3	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.26
	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.81
	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.78
CY2021Q3	us-gaap	Net Income Loss NetIncomeLoss	17175000
CY2020Q3	us-gaap	Net Income Loss NetIncomeLoss	12273000
	us-gaap	Net Income Loss NetIncomeLoss	58085000
	us-gaap	Net Income Loss NetIncomeLoss	24532000
CY2021Q3	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	-6400000
CY2020Q3	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	-69000
	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	-15800000
	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	13778000
CY2021Q3	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax	-80000
CY2020Q3	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax	123000
	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax	1143000
	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax	-174000
CY2021Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-138000
CY2020Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-233000
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-413000
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-700000
CY2021Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-6182000
CY2020Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	287000
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-14244000
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	14304000
CY2021Q3	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	10993000
CY2020Q3	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	12560000
	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	43841000
	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	38836000
CY2020Q4	us-gaap	Stockholders Equity StockholdersEquity	468363000
CY2021Q1	us-gaap	Net Income Loss NetIncomeLoss	20710000
CY2021Q1	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-12700000
CY2021Q1	us-gaap	Stock Issued During Period Value New Issues StockIssuedDuringPeriodValueNewIssues	301000
CY2021Q1	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	5963000
CY2021Q1	us-gaap	Stock Repurchased During Period Value StockRepurchasedDuringPeriodValue	6000
CY2021Q1	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	216000
CY2021Q1	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.27
CY2021Q1	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	4272000
CY2021Q1	us-gaap	Stockholders Equity StockholdersEquity	466284000
CY2021Q2	us-gaap	Net Income Loss NetIncomeLoss	20200000
CY2021Q2	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	4638000
CY2021Q2	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	1000
CY2021Q2	us-gaap	Stock Repurchased During Period Value StockRepurchasedDuringPeriodValue	37000
CY2021Q2	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	562000
CY2021Q2	us-gaap	Stock Granted During Period Value Sharebased Compensation StockGrantedDuringPeriodValueSharebasedCompensation	118000
CY2021Q2	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.27
CY2021Q2	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	4272000
CY2021Q2	us-gaap	Stockholders Equity StockholdersEquity	487126000
CY2021Q3	us-gaap	Net Income Loss NetIncomeLoss	17175000
CY2021Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-6182000
CY2021Q3	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	538000
CY2021Q3	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.27
CY2021Q3	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	4277000
CY2021Q3	us-gaap	Stockholders Equity StockholdersEquity	494013000
CY2019Q4	us-gaap	Stockholders Equity StockholdersEquity	438947000
CY2020Q1	us-gaap	Net Income Loss NetIncomeLoss	1127000
CY2020Q1	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	12431000
CY2020Q1	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	196000
CY2020Q1	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	332000
CY2020Q1	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.26
CY2020Q1	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	4164000
CY2020Q1	us-gaap	Stockholders Equity StockholdersEquity	439393000
CY2020Q2	us-gaap	Net Income Loss NetIncomeLoss	11132000
CY2020Q2	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	1586000
CY2020Q2	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	369000
CY2020Q2	us-gaap	Stock Granted During Period Value Sharebased Compensation StockGrantedDuringPeriodValueSharebasedCompensation	95000
CY2020Q2	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.26
CY2020Q2	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	4164000
CY2020Q2	us-gaap	Stockholders Equity StockholdersEquity	448045000
CY2020Q3	us-gaap	Net Income Loss NetIncomeLoss	12273000
CY2020Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	287000
CY2020Q3	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	289000
CY2020Q3	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.26
CY2020Q3	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	4168000
CY2020Q3	us-gaap	Stockholders Equity StockholdersEquity	456361000
	us-gaap	Profit Loss ProfitLoss	58085000
	us-gaap	Profit Loss ProfitLoss	24532000
	us-gaap	Depreciation And Amortization DepreciationAndAmortization	6067000
	us-gaap	Depreciation And Amortization DepreciationAndAmortization	5924000
	us-gaap	Accretion Amortization Of Discounts And Premiums Investments AccretionAmortizationOfDiscountsAndPremiumsInvestments	-3845000
	us-gaap	Accretion Amortization Of Discounts And Premiums Investments AccretionAmortizationOfDiscountsAndPremiumsInvestments	-2313000
	fisi	Provision Benefit For Credit Losses ProvisionBenefitForCreditLosses	-7144000
	fisi	Provision Benefit For Credit Losses ProvisionBenefitForCreditLosses	21689000
	us-gaap	Share Based Compensation ShareBasedCompensation	1316000
	us-gaap	Share Based Compensation ShareBasedCompensation	990000
	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-6885000
	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-2692000
	us-gaap	Proceeds From Sale Of Loans Held For Sale ProceedsFromSaleOfLoansHeldForSale	63331000
	us-gaap	Proceeds From Sale Of Loans Held For Sale ProceedsFromSaleOfLoansHeldForSale	63995000
	us-gaap	Payments For Origination And Purchases Of Loans Held For Sale PaymentsForOriginationAndPurchasesOfLoansHeldForSale	62474000
	us-gaap	Payments For Origination And Purchases Of Loans Held For Sale PaymentsForOriginationAndPurchasesOfLoansHeldForSale	64586000
	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	2126000
	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	1397000
	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	2468000
	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	2261000
	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	71000
	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	1449000
	us-gaap	Gain Loss On Sale Of Other Assets GainLossOnSaleOfOtherAssets	286000
	us-gaap	Gain Loss On Sale Of Other Assets GainLossOnSaleOfOtherAssets	8000
	fisi	Noncash Restructuring Charges Against Assets NoncashRestructuringChargesAgainstAssets	76000
	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	2513000
	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	42243000
	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	-9286000
	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	15491000
	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	39467000
	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	20298000
	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	650713000
	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	215433000
	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	17009000
	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	6008000
	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	115688000
	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	85766000
	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	69954000
	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	73120000
	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	51891000
	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	50207000
	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	59841000
	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	361935000
	us-gaap	Payments For Proceeds From Life Insurance Policies PaymentsForProceedsFromLifeInsurancePolicies	20013000
	us-gaap	Payments For Proceeds From Life Insurance Policies PaymentsForProceedsFromLifeInsurancePolicies	8000
	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	-3425000
	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	-482000
	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	8357000
	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	2800000
	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	1420000
	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	0
	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-516395000
	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-376609000
	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	696596000
	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	809253000
	us-gaap	Proceeds From Repayments Of Short Term Debt ProceedsFromRepaymentsOfShortTermDebt	-5300000
	us-gaap	Proceeds From Repayments Of Short Term Debt ProceedsFromRepaymentsOfShortTermDebt	-270200000
	us-gaap	Payments For Repurchase Of Preferred Stock And Preference Stock PaymentsForRepurchaseOfPreferredStockAndPreferenceStock	43000
	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	5967000
	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	196000
	us-gaap	Payments Of Dividends PaymentsOfDividends	13810000
	us-gaap	Payments Of Dividends PaymentsOfDividends	13423000
	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	671476000
	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	525434000
	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	194548000
	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	169123000
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Including Disposal Group And Discontinued Operations CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations	93878000
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Including Disposal Group And Discontinued Operations CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations	112947000
CY2021Q3	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Including Disposal Group And Discontinued Operations CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations	288426000
CY2020Q3	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Including Disposal Group And Discontinued Operations CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations	282070000
	fisi	Offering Unsecured Personal Loans Percentage OfferingUnsecuredPersonalLoansPercentage	0.0295
	us-gaap	Prior Period Reclassification Adjustment Description PriorPeriodReclassificationAdjustmentDescription	<p style="text-indent:0.0%;font-size:10.0pt;margin-top:8.0pt;line-height:1.3;font-family:Times New Roman;margin-bottom:0.0pt;text-align:justify;"><span style="background-color:rgba(0,0,0,0);color:rgba(0,0,0,1);white-space:pre-wrap;font-weight:bold;font-size:10.0pt;font-family:Times New Roman;">Reclassifications</span></p><p style="text-indent:0.0%;font-size:10.0pt;margin-top:4.0pt;line-height:1.3;font-family:Times New Roman;margin-bottom:0.0pt;text-align:justify;"><span style="background-color:rgba(0,0,0,0);color:rgba(0,0,0,1);white-space:pre-wrap;font-weight:normal;font-size:10.0pt;font-family:Times New Roman;">Certain reclassifications of previously reported amounts have been made to conform to the current year presentation. Such reclassifications did not impact net income or shareholders’ equity as previously reported.</span></p>
	us-gaap	Use Of Estimates UseOfEstimates	<p style="text-indent:0.0%;font-size:10.0pt;margin-top:12.0pt;line-height:1.3;font-family:Times New Roman;margin-bottom:0.0pt;text-align:justify;"><span style="background-color:rgba(0,0,0,0);color:rgba(0,0,0,1);white-space:pre-wrap;font-weight:bold;font-size:10.0pt;font-family:Times New Roman;">Use of Estimates</span></p><p style="text-indent:0.0%;font-size:10.0pt;margin-top:4.0pt;line-height:1.3;font-family:Times New Roman;margin-bottom:0.0pt;text-align:justify;"><span style="background-color:rgba(0,0,0,0);color:rgba(0,0,0,1);white-space:pre-wrap;font-weight:normal;font-size:10.0pt;font-family:Times New Roman;">The preparation of these financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from those estimates. 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.</span></p>
	us-gaap	Interest Paid Net InterestPaidNet	12100000
	us-gaap	Interest Paid Net InterestPaidNet	23533000
	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	10800000
	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	5656000
	us-gaap	Transfer To Other Real Estate TransferToOtherRealEstate	2966000
CY2021Q3	us-gaap	Dividends Payable Current And Noncurrent DividendsPayableCurrentAndNoncurrent	4641000
CY2020Q3	us-gaap	Dividends Payable Current And Noncurrent DividendsPayableCurrentAndNoncurrent	4534000
	us-gaap	Stock Issued1 StockIssued1	301000
	us-gaap	Fair Value Of Assets Acquired FairValueOfAssetsAcquired	712000
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
CY2020	us-gaap	Effect On Future Cash Flows Amount EffectOnFutureCashFlowsAmount	800000
CY2020	fisi	Anticipates Annual Expense Savings Branch Closures AnticipatesAnnualExpenseSavingsBranchClosures	2700000
CY2020Q3	us-gaap	Restructuring Costs RestructuringCosts	1586000
	us-gaap	Restructuring Costs RestructuringCosts	1586000
CY2021Q2	us-gaap	Restructuring Reserve RestructuringReserve	1088000
CY2020Q4	us-gaap	Restructuring Reserve RestructuringReserve	1245000
CY2020Q3	us-gaap	Restructuring Costs RestructuringCosts	1586000
	us-gaap	Restructuring Costs RestructuringCosts	1586000
CY2021Q3	us-gaap	Payments For Restructuring PaymentsForRestructuring	33000
CY2020Q3	us-gaap	Payments For Restructuring PaymentsForRestructuring	249000
	us-gaap	Payments For Restructuring PaymentsForRestructuring	179000
	us-gaap	Payments For Restructuring PaymentsForRestructuring	249000
CY2021Q3	us-gaap	Restructuring Reserve Period Increase Decrease RestructuringReservePeriodIncreaseDecrease	-456000
	us-gaap	Restructuring Reserve Period Increase Decrease RestructuringReservePeriodIncreaseDecrease	-467000
CY2021Q3	us-gaap	Restructuring Reserve RestructuringReserve	599000
CY2020Q3	us-gaap	Restructuring Reserve RestructuringReserve	1337000
CY2021Q3	us-gaap	Restructuring Reserve RestructuringReserve	599000
CY2020Q3	us-gaap	Restructuring Reserve RestructuringReserve	1337000
CY2021Q3	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	16811000
CY2020Q3	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	11908000
	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	56990000
	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	23436000
CY2021Q3	us-gaap	Weighted Average Number Of Shares Issued Basic WeightedAverageNumberOfSharesIssuedBasic	16100000
CY2020Q3	us-gaap	Weighted Average Number Of Shares Issued Basic WeightedAverageNumberOfSharesIssuedBasic	16100000
	us-gaap	Weighted Average Number Of Shares Issued Basic WeightedAverageNumberOfSharesIssuedBasic	16100000
	us-gaap	Weighted Average Number Of Shares Issued Basic WeightedAverageNumberOfSharesIssuedBasic	16100000
CY2021Q3	us-gaap	Weighted Average Number Of Shares Restricted Stock WeightedAverageNumberOfSharesRestrictedStock	5000
CY2020Q3	us-gaap	Weighted Average Number Of Shares Restricted Stock WeightedAverageNumberOfSharesRestrictedStock	7000
	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.46
	us-gaap	Weighted Average Number Of Shares Restricted Stock WeightedAverageNumberOfSharesRestrictedStock	6000
	us-gaap	Weighted Average Number Of Shares Restricted Stock WeightedAverageNumberOfSharesRestrictedStock	5000
CY2021Q3	us-gaap	Weighted Average Number Of Shares Treasury Stock WeightedAverageNumberOfSharesTreasuryStock	258000
CY2020Q3	us-gaap	Weighted Average Number Of Shares Treasury Stock WeightedAverageNumberOfSharesTreasuryStock	62000
	us-gaap	Weighted Average Number Of Shares Treasury Stock WeightedAverageNumberOfSharesTreasuryStock	244000
	us-gaap	Weighted Average Number Of Shares Treasury Stock WeightedAverageNumberOfSharesTreasuryStock	77000
CY2021Q3	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	15837000
CY2020Q3	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	16031000
	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	15850000
	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	16018000
CY2021Q3	fisi	Incremental Common Shares Attributable To Vesting Of Restricted Stock Awards IncrementalCommonSharesAttributableToVestingOfRestrictedStockAwards	99000
CY2020Q3	fisi	Incremental Common Shares Attributable To Vesting Of Restricted Stock Awards IncrementalCommonSharesAttributableToVestingOfRestrictedStockAwards	27000
	fisi	Incremental Common Shares Attributable To Vesting Of Restricted Stock Awards IncrementalCommonSharesAttributableToVestingOfRestrictedStockAwards	90000
	fisi	Incremental Common Shares Attributable To Vesting Of Restricted Stock Awards IncrementalCommonSharesAttributableToVestingOfRestrictedStockAwards	40000
CY2021Q3	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	15936000
CY2020Q3	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	16058000
	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	15940000
	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	16058000
CY2021Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.06
CY2020Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.74
	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	3.60
	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.46
CY2021Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.05
CY2020Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.74
	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	3.58
CY2021Q3	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	0
CY2020Q3	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	71000
	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	4000
	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	49000
CY2021Q3	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	1098976000
CY2021Q3	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	11337000
CY2021Q3	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	12363000
CY2021Q3	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	224164000
CY2021Q3	fisi	Allowance For Credit Losses Amortized Cost AllowanceForCreditLossesAmortizedCost	5000
CY2021Q3	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	1097950000
CY2021Q3	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	218140000
CY2021Q3	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Gain HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain	6352000
CY2021Q3	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Loss HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss	328000
CY2021Q3	fisi	Held To Maturity Securities Net HeldToMaturitySecuritiesNet	218135000
CY2020Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	607665000
CY2020Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	20462000
CY2020Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	68000
CY2020Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	628059000
CY2020Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	271973000
CY2020Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Gain HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain	10062000
CY2020Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	282035000
CY2020Q4	fisi	Allowance For Credit Losses Amortized Cost AllowanceForCreditLossesAmortizedCost	7000
CY2020Q4	fisi	Held To Maturity Securities Net HeldToMaturitySecuritiesNet	271966000
CY2021Q3	fisi	Debt Securities Available For Sale And Held To Maturity Restricted DebtSecuritiesAvailableForSaleAndHeldToMaturityRestricted	861200000
CY2020Q4	fisi	Debt Securities Available For Sale And Held To Maturity Restricted DebtSecuritiesAvailableForSaleAndHeldToMaturityRestricted	567400000
CY2021Q3	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	0
CY2020Q3	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	20576000
	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	51891000
	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	50207000
CY2021Q3	us-gaap	Debt Securities Available For Sale Realized Gain DebtSecuritiesAvailableForSaleRealizedGain	0
CY2020Q3	us-gaap	Debt Securities Available For Sale Realized Gain DebtSecuritiesAvailableForSaleRealizedGain	554000
	us-gaap	Debt Securities Available For Sale Realized Gain DebtSecuritiesAvailableForSaleRealizedGain	251000
	us-gaap	Debt Securities Available For Sale Realized Gain DebtSecuritiesAvailableForSaleRealizedGain	1170000
CY2021Q3	us-gaap	Debt Securities Available For Sale Realized Loss DebtSecuritiesAvailableForSaleRealizedLoss	0
	us-gaap	Debt Securities Available For Sale Realized Loss DebtSecuritiesAvailableForSaleRealizedLoss	180000
	us-gaap	Debt Securities Available For Sale Realized Loss DebtSecuritiesAvailableForSaleRealizedLoss	9000
CY2021Q3	us-gaap	Available For Sale Securities Debt Maturities Within One Year Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost	4863000
CY2021Q3	us-gaap	Available For Sale Securities Debt Maturities Within One Year Fair Value AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue	4891000
CY2021Q3	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost	62802000
CY2021Q3	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	65773000
CY2021Q3	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost	175663000
CY2021Q3	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	180702000
CY2021Q3	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost	855648000
CY2021Q3	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue	846584000
CY2021Q3	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	1098976000
CY2021Q3	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	1097950000
CY2021Q3	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount	36191000
CY2021Q3	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Fair Value HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearFairValue	36543000
CY2021Q3	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsNetCarryingAmount	72707000
CY2021Q3	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	75317000
CY2021Q3	us-gaap	Held To Maturity Securities Debt Maturities After Five Through Ten Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsNetCarryingAmount	20848000
CY2021Q3	us-gaap	Held To Maturity Securities Debt Maturities After Five Through Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	21233000
CY2021Q3	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsNetCarryingAmount	88394000
CY2021Q3	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsFairValue	91071000
CY2021Q3	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	218140000
CY2021Q3	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	224164000
CY2021Q3	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months	768267000
CY2021Q3	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	11822000
CY2021Q3	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger	16849000
CY2021Q3	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	541000
CY2021Q3	us-gaap	Debt Securities Available For Sale Unrealized Loss Position DebtSecuritiesAvailableForSaleUnrealizedLossPosition	785116000
CY2021Q3	us-gaap	Debt Securities Available For Sale Unrealized Loss Position Accumulated Loss DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss	12363000
CY2021Q3	fisi	Investment Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value InvestmentSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue	768267000
CY2021Q3	fisi	Investment Securities Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss InvestmentSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	11822000
CY2021Q3	fisi	Investment Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value InvestmentSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue	16849000
CY2021Q3	fisi	Investment Securities Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss InvestmentSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	541000
CY2021Q3	fisi	Investment Securities Continuous Unrealized Loss Position Fair Value InvestmentSecuritiesContinuousUnrealizedLossPositionFairValue	785116000
CY2021Q3	fisi	Investment Securities Accumulated Unrecognized Holding Loss InvestmentSecuritiesAccumulatedUnrecognizedHoldingLoss	12363000
CY2020Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months	29087000
CY2020Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	68000
CY2020Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger	8000
CY2020Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position DebtSecuritiesAvailableForSaleUnrealizedLossPosition	29095000
CY2020Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position Accumulated Loss DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss	68000
CY2020Q4	fisi	Investment Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value InvestmentSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue	29087000
CY2020Q4	fisi	Investment Securities Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss InvestmentSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	68000
CY2020Q4	fisi	Investment Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value InvestmentSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue	8000
CY2020Q4	fisi	Investment Securities Continuous Unrealized Loss Position Fair Value InvestmentSecuritiesContinuousUnrealizedLossPositionFairValue	29095000
CY2020Q4	fisi	Investment Securities Accumulated Unrecognized Holding Loss InvestmentSecuritiesAccumulatedUnrecognizedHoldingLoss	68000
CY2021Q3	fisi	Investment Securities In Unrealized Loss Position Number Of Positions InvestmentSecuritiesInUnrealizedLossPositionNumberOfPositions	99
CY2020Q4	fisi	Investment Securities In Unrealized Loss Position Number Of Positions InvestmentSecuritiesInUnrealizedLossPositionNumberOfPositions	8
CY2021Q3	fisi	Investment Securities In Unrealized Loss Positions Twelve Months Or Longer Qualitative Disclosure Number Of Positions InvestmentSecuritiesInUnrealizedLossPositionsTwelveMonthsOrLongerQualitativeDisclosureNumberOfPositions	6
CY2021Q3	fisi	Investment Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value InvestmentSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue	16800000
CY2021Q3	fisi	Investment Securities Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss InvestmentSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	541000
CY2021Q3	fisi	Investment Securities In Unrealized Loss Positions Less Than Twelve Months Qualitative Disclosure Number Of Positions InvestmentSecuritiesInUnrealizedLossPositionsLessThanTwelveMonthsQualitativeDisclosureNumberOfPositions	93
CY2021Q3	fisi	Investment Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value InvestmentSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue	768300000
CY2021Q3	fisi	Investment Securities Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss InvestmentSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	11800000
CY2020Q4	fisi	Investment Securities In Unrealized Loss Positions Twelve Months Or Longer Qualitative Disclosure Number Of Positions InvestmentSecuritiesInUnrealizedLossPositionsTwelveMonthsOrLongerQualitativeDisclosureNumberOfPositions	1
CY2020Q4	fisi	Investment Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value InvestmentSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue	8000
CY2020Q4	fisi	Investment Securities In Unrealized Loss Positions Less Than Twelve Months Qualitative Disclosure Number Of Positions InvestmentSecuritiesInUnrealizedLossPositionsLessThanTwelveMonthsQualitativeDisclosureNumberOfPositions	7
CY2020Q4	fisi	Investment Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value InvestmentSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue	29100000
CY2020Q4	fisi	Investment Securities Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss InvestmentSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	68000
CY2021Q3	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	0
CY2020Q4	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	0
CY2021Q3	us-gaap	Loans And Leases Receivable Gross Carrying Amount LoansAndLeasesReceivableGrossCarryingAmount	3609791000
CY2021Q3	fisi	Loans And Leases Receivable Deferred Loan Fees Costs LoansAndLeasesReceivableDeferredLoanFeesCosts	-44108000
CY2021Q3	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	3653899000
CY2021Q3	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	45444000
CY2021Q3	us-gaap	Loans And Leases Receivable Net Reported Amount LoansAndLeasesReceivableNetReportedAmount	3608455000
CY2020Q4	us-gaap	Loans And Leases Receivable Gross Carrying Amount LoansAndLeasesReceivableGrossCarryingAmount	3557908000
CY2020Q4	fisi	Loans And Leases Receivable Deferred Loan Fees Costs LoansAndLeasesReceivableDeferredLoanFeesCosts	-37230000
CY2020Q4	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	3595138000
CY2020Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	52420000
CY2020Q4	us-gaap	Loans And Leases Receivable Net Reported Amount LoansAndLeasesReceivableNetReportedAmount	3542718000
CY2021Q3	us-gaap	Loans Receivable Held For Sale Net Not Part Of Disposal Group LoansReceivableHeldForSaleNetNotPartOfDisposalGroup	5900000
CY2021Q3	us-gaap	Financing Receivable Recorded Investment Nonaccrual Status FinancingReceivableRecordedInvestmentNonaccrualStatus	6675000
CY2021Q3	us-gaap	Notes Receivable Gross NotesReceivableGross	3609791000
CY2021Q3	us-gaap	Financing Receivable Nonaccrual No Allowance FinancingReceivableNonaccrualNoAllowance	5597000
CY2020Q4	us-gaap	Financing Receivable Recorded Investment Nonaccrual Status FinancingReceivableRecordedInvestmentNonaccrualStatus	9286000
CY2020Q4	us-gaap	Notes Receivable Gross NotesReceivableGross	3557908000
CY2020Q4	us-gaap	Financing Receivable Nonaccrual No Allowance FinancingReceivableNonaccrualNoAllowance	8616000
CY2021Q3	us-gaap	Financing Receivable Recorded Investment90 Days Past Due And Still Accruing FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing	0
CY2020Q4	us-gaap	Financing Receivable Recorded Investment90 Days Past Due And Still Accruing FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing	0
	us-gaap	Financing Receivable Nonaccrual Interest Income FinancingReceivableNonaccrualInterestIncome	0
CY2020	us-gaap	Financing Receivable Nonaccrual Interest Income FinancingReceivableNonaccrualInterestIncome	0
	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	0
	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	0
	us-gaap	Financing Receivable Modifications Subsequent Default Number Of Contracts1 FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1	0
	us-gaap	Financing Receivable Modifications Subsequent Default Number Of Contracts1 FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1	0
	fisi	Days Past Due When Loans Are Generally Placed On Nonaccrual Status In Days DaysPastDueWhenLoansAreGenerallyPlacedOnNonaccrualStatusInDays	P90D
	fisi	Days Past Due When Loans Are Generally Placed On Nonaccrual Status In Days DaysPastDueWhenLoansAreGenerallyPlacedOnNonaccrualStatusInDays	P90D
CY2021Q3	fisi	Collateral Dependent Loans On Business Assets CollateralDependentLoansOnBusinessAssets	596000
CY2021Q3	fisi	Collateral Dependent Loans On Real Property CollateralDependentLoansOnRealProperty	65278000
CY2021Q3	fisi	Collateral Dependent Loans CollateralDependentLoans	65874000
CY2021Q3	fisi	Collateral Dependent Loan With Specific Reserve CollateralDependentLoanWithSpecificReserve	11320000
CY2020Q4	fisi	Collateral Dependent Loans On Business Assets CollateralDependentLoansOnBusinessAssets	2379000
CY2020Q4	fisi	Collateral Dependent Loans On Real Property CollateralDependentLoansOnRealProperty	36625000
CY2020Q4	fisi	Collateral Dependent Loans CollateralDependentLoans	39004000
CY2020Q4	fisi	Collateral Dependent Loan With Specific Reserve CollateralDependentLoanWithSpecificReserve	9570000
CY2021Q2	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	46365000
CY2021Q3	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	1959000
CY2021Q3	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	1372000
CY2021Q3	fisi	Financing Receivable Allowance For Loan Losses Provision Credit FinancingReceivableAllowanceForLoanLossesProvisionCredit	-334000
CY2021Q3	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	45444000
CY2020Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	52420000
	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	6552000
	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	5472000
	fisi	Financing Receivable Allowance For Loan Losses Provision Credit FinancingReceivableAllowanceForLoanLossesProvisionCredit	-5896000
CY2021Q3	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	45444000
CY2020Q2	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	46316000
CY2020Q3	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	2203000
CY2020Q3	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	1715000
CY2020Q3	fisi	Financing Receivable Allowance For Loan Losses Provision Credit FinancingReceivableAllowanceForLoanLossesProvisionCredit	3567000
CY2020Q3	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	49395000
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	30482000
	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	17958000
	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	6541000
	fisi	Financing Receivable Allowance For Loan Losses Provision Credit FinancingReceivableAllowanceForLoanLossesProvisionCredit	20736000
CY2020Q3	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	49395000
	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
	us-gaap	Lessee Operating Sublease Option To Extend LesseeOperatingSubleaseOptionToExtend	One building lease was subleased in 2021 for terms that extended through June 30, 2021.
	fisi	Number Of Buildings Subleased NumberOfBuildingsSubleased	1
CY2021Q3	fisi	Operating Lease Right Of Use Asset Gross OperatingLeaseRightOfUseAssetGross	26990000
CY2020Q4	fisi	Operating Lease Right Of Use Asset Gross OperatingLeaseRightOfUseAssetGross	23697000
CY2021Q3	fisi	Operating Lease Right Of Use Asset Accumulated Amortization OperatingLeaseRightOfUseAssetAccumulatedAmortization	4536000
CY2020Q4	fisi	Operating Lease Right Of Use Asset Accumulated Amortization OperatingLeaseRightOfUseAssetAccumulatedAmortization	3741000
CY2021Q3	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	22454000
CY2020Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	19956000
CY2021Q3	us-gaap	Operating Lease Liability OperatingLeaseLiability	24212000
CY2020Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	21507000
CY2021Q3	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P24Y
CY2021Q3	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.0370
CY2021Q3	us-gaap	Operating Lease Cost OperatingLeaseCost	687000
CY2020Q3	us-gaap	Operating Lease Cost OperatingLeaseCost	663000
	us-gaap	Operating Lease Cost OperatingLeaseCost	2162000
	us-gaap	Operating Lease Cost OperatingLeaseCost	2018000
CY2021Q3	us-gaap	Variable Lease Cost VariableLeaseCost	137000
CY2020Q3	us-gaap	Variable Lease Cost VariableLeaseCost	111000
	us-gaap	Variable Lease Cost VariableLeaseCost	325000
	us-gaap	Variable Lease Cost VariableLeaseCost	313000
CY2021Q3	us-gaap	Sublease Income SubleaseIncome	0
CY2020Q3	us-gaap	Sublease Income SubleaseIncome	12000
	us-gaap	Sublease Income SubleaseIncome	23000
	us-gaap	Sublease Income SubleaseIncome	35000
CY2021Q3	us-gaap	Lease Cost LeaseCost	824000
CY2020Q3	us-gaap	Lease Cost LeaseCost	762000
	us-gaap	Lease Cost LeaseCost	2464000
	us-gaap	Lease Cost LeaseCost	2296000
	us-gaap	Operating Lease Payments OperatingLeasePayments	2008000
	us-gaap	Operating Lease Payments OperatingLeasePayments	1947000
	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	4178000
	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	470000
CY2021Q3	us-gaap	Lessee Operating Lease Liability Payments Due Next Rolling Twelve Months LesseeOperatingLeaseLiabilityPaymentsDueNextRollingTwelveMonths	2380000
CY2021Q3	us-gaap	Lessee Operating Lease Liability Payments Due In Rolling Year Two LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearTwo	2048000
CY2021Q3	us-gaap	Lessee Operating Lease Liability Payments Due In Rolling Year Three LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearThree	1508000
CY2021Q3	us-gaap	Lessee Operating Lease Liability Payments Due In Rolling Year Four LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearFour	1416000
CY2021Q3	us-gaap	Lessee Operating Lease Liability Payments Due In Rolling Year Five LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearFive	1338000
CY2021Q3	us-gaap	Lessee Operating Lease Liability Payments Due After Rolling Year Five LesseeOperatingLeaseLiabilityPaymentsDueAfterRollingYearFive	30217000
CY2021Q3	us-gaap	Lessee Operating Lease Liability Payments Due LesseeOperatingLeaseLiabilityPaymentsDue	38907000
CY2021Q3	us-gaap	Lessee Operating Lease Liability Undiscounted Excess Amount LesseeOperatingLeaseLiabilityUndiscountedExcessAmount	14695000
CY2021Q3	us-gaap	Operating Lease Liability OperatingLeaseLiability	24212000
CY2021Q3	us-gaap	Goodwill Goodwill	67100000
CY2020Q4	us-gaap	Goodwill Goodwill	66100000
CY2020Q4	us-gaap	Goodwill Goodwill	66062000
	us-gaap	Goodwill Acquired During Period GoodwillAcquiredDuringPeriod	1009000
CY2021Q3	us-gaap	Goodwill Goodwill	67071000
CY2021Q3	us-gaap	Finite Lived Intangible Assets Gross FiniteLivedIntangibleAssetsGross	16587000
CY2020Q4	us-gaap	Finite Lived Intangible Assets Gross FiniteLivedIntangibleAssetsGross	15925000
CY2021Q3	us-gaap	Finite Lived Intangible Assets Accumulated Amortization FiniteLivedIntangibleAssetsAccumulatedAmortization	8999000
CY2020Q4	us-gaap	Finite Lived Intangible Assets Accumulated Amortization FiniteLivedIntangibleAssetsAccumulatedAmortization	8198000
CY2021Q3	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	7588000
CY2020Q4	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	7727000
CY2021Q3	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	264000
CY2020Q3	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	280000
	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	861000
CY2021Q3	us-gaap	Finite Lived Intangible Assets Amortization Expense Remainder Of Fiscal Year FiniteLivedIntangibleAssetsAmortizationExpenseRemainderOfFiscalYear	260000
CY2021Q3	us-gaap	Finite Lived Intangible Assets Amortization Expense Next Twelve Months FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths	985000
CY2021Q3	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Two FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo	910000
CY2021Q3	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Three FiniteLivedIntangibleAssetsAmortizationExpenseYearThree	838000
CY2021Q3	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Four FiniteLivedIntangibleAssetsAmortizationExpenseYearFour	766000
CY2021Q3	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Five FiniteLivedIntangibleAssetsAmortizationExpenseYearFive	694000
CY2021Q3	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	22454000
CY2020Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	19956000
CY2021Q3	fisi	Tax Credit Investments TaxCreditInvestments	50075000
CY2020Q4	fisi	Tax Credit Investments TaxCreditInvestments	34370000
CY2021Q3	us-gaap	Derivative Fair Value Of Derivative Asset DerivativeFairValueOfDerivativeAsset	16139000
CY2020Q4	us-gaap	Derivative Fair Value Of Derivative Asset DerivativeFairValueOfDerivativeAsset	20120000
CY2021Q3	fisi	Collateral On Derivative Instruments CollateralOnDerivativeInstruments	6180000
CY2020Q4	fisi	Collateral On Derivative Instruments CollateralOnDerivativeInstruments	19630000
CY2021Q3	us-gaap	Other Assets Miscellaneous OtherAssetsMiscellaneous	71165000
CY2020Q4	us-gaap	Other Assets Miscellaneous OtherAssetsMiscellaneous	62010000
CY2021Q3	us-gaap	Other Assets OtherAssets	166013000
CY2020Q4	us-gaap	Other Assets OtherAssets	156086000
CY2021Q3	us-gaap	Interest Rate Cash Flow Hedge Gain Loss To Be Reclassified During Next12 Months Net InterestRateCashFlowHedgeGainLossToBeReclassifiedDuringNext12MonthsNet	142000
CY2020Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	16099556
CY2021Q1	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	16099556
CY2021Q2	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	16099556
CY2021Q3	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	16099556
CY2019Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	16099556
CY2020Q1	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	16099556
CY2020Q2	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	16099556
CY2020Q3	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	16099556
CY2020Q4	us-gaap	Stock Repurchase Program Number Of Shares Authorized To Be Repurchased StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased	801879
	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	238439
	us-gaap	Treasury Stock Acquired Average Cost Per Share TreasuryStockAcquiredAverageCostPerShare	24.30
CY2021Q3	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	0
CY2020	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	0
CY2021Q3	us-gaap	Stock Repurchase Program Remaining Number Of Shares Authorized To Be Repurchased StockRepurchaseProgramRemainingNumberOfSharesAuthorizedToBeRepurchased	563440
CY2021Q3	us-gaap	Other Comprehensive Income Loss Before Tax Portion Attributable To Parent OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent	8312000
CY2021Q3	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	2130000
CY2021Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-6182000
	us-gaap	Other Comprehensive Income Loss Before Tax Portion Attributable To Parent OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent	-19151000
	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	-4907000
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-14244000
CY2020Q3	us-gaap	Other Comprehensive Income Loss Before Tax Portion Attributable To Parent OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent	385000
CY2020Q3	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	98000
CY2020Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	287000
	us-gaap	Other Comprehensive Income Loss Before Tax Portion Attributable To Parent OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent	19231000
	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	4927000
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	14304000
CY2021Q3	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	6351000
CY2021Q3	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-169000
CY2021Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-6182000
	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	-14735000
	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-491000
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-14244000
CY2020Q3	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	401000
CY2020Q3	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	114000
CY2020Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	287000
	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	14506000
	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	202000
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	14304000
CY2021Q3	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-169000
CY2020Q3	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	114000
	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-491000
	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	202000
CY2021Q3	us-gaap	Share Based Compensation ShareBasedCompensation	538000
CY2020Q3	us-gaap	Share Based Compensation ShareBasedCompensation	289000
	us-gaap	Share Based Compensation ShareBasedCompensation	1316000
	us-gaap	Share Based Compensation ShareBasedCompensation	990000
CY2021Q3	us-gaap	Defined Benefit Plan Service Cost DefinedBenefitPlanServiceCost	1049000
CY2020Q3	us-gaap	Defined Benefit Plan Service Cost DefinedBenefitPlanServiceCost	924000
	us-gaap	Defined Benefit Plan Service Cost DefinedBenefitPlanServiceCost	3147000
	us-gaap	Defined Benefit Plan Service Cost DefinedBenefitPlanServiceCost	2770000
CY2021Q3	us-gaap	Defined Benefit Plan Interest Cost DefinedBenefitPlanInterestCost	551000
CY2020Q3	us-gaap	Defined Benefit Plan Interest Cost DefinedBenefitPlanInterestCost	635000
	us-gaap	Defined Benefit Plan Interest Cost DefinedBenefitPlanInterestCost	1653000
	us-gaap	Defined Benefit Plan Interest Cost DefinedBenefitPlanInterestCost	1905000
CY2021Q3	us-gaap	Defined Benefit Plan Expected Return On Plan Assets DefinedBenefitPlanExpectedReturnOnPlanAssets	1306000
CY2020Q3	us-gaap	Defined Benefit Plan Expected Return On Plan Assets DefinedBenefitPlanExpectedReturnOnPlanAssets	1284000
	us-gaap	Defined Benefit Plan Expected Return On Plan Assets DefinedBenefitPlanExpectedReturnOnPlanAssets	3919000
	us-gaap	Defined Benefit Plan Expected Return On Plan Assets DefinedBenefitPlanExpectedReturnOnPlanAssets	3852000
CY2021Q3	us-gaap	Defined Benefit Plan Amortization Of Prior Service Cost Credit DefinedBenefitPlanAmortizationOfPriorServiceCostCredit	-1000
CY2020Q3	us-gaap	Defined Benefit Plan Amortization Of Prior Service Cost Credit DefinedBenefitPlanAmortizationOfPriorServiceCostCredit	-8000
	us-gaap	Defined Benefit Plan Amortization Of Prior Service Cost Credit DefinedBenefitPlanAmortizationOfPriorServiceCostCredit	-2000
	us-gaap	Defined Benefit Plan Amortization Of Prior Service Cost Credit DefinedBenefitPlanAmortizationOfPriorServiceCostCredit	-26000
CY2021Q3	us-gaap	Defined Benefit Plan Amortization Of Gains Losses DefinedBenefitPlanAmortizationOfGainsLosses	-186000
CY2020Q3	us-gaap	Defined Benefit Plan Amortization Of Gains Losses DefinedBenefitPlanAmortizationOfGainsLosses	-321000
	us-gaap	Defined Benefit Plan Amortization Of Gains Losses DefinedBenefitPlanAmortizationOfGainsLosses	-557000
	us-gaap	Defined Benefit Plan Amortization Of Gains Losses DefinedBenefitPlanAmortizationOfGainsLosses	-967000
CY2021Q3	us-gaap	Defined Benefit Plan Net Periodic Benefit Cost DefinedBenefitPlanNetPeriodicBenefitCost	479000
CY2020Q3	us-gaap	Defined Benefit Plan Net Periodic Benefit Cost DefinedBenefitPlanNetPeriodicBenefitCost	588000
	us-gaap	Defined Benefit Plan Net Periodic Benefit Cost DefinedBenefitPlanNetPeriodicBenefitCost	1436000
	us-gaap	Defined Benefit Plan Net Periodic Benefit Cost DefinedBenefitPlanNetPeriodicBenefitCost	1764000
CY2020Q3	fisi	Provision Benefit For Credit Losses ProvisionBenefitForCreditLosses	4028000
CY2020Q3	us-gaap	Noninterest Income NoninterestIncome	12217000
CY2020Q3	us-gaap	Noninterest Expense NoninterestExpense	28475000
CY2020Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	15213000
CY2020Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	2940000
CY2020Q3	us-gaap	Net Income Loss NetIncomeLoss	12273000
CY2021Q3	us-gaap	Fair Value Assets Level2 To Level1 Transfers Amount FairValueAssetsLevel2ToLevel1TransfersAmount	0
CY2021Q3	us-gaap	Fair Value Assets Level1 To Level2 Transfers Amount FairValueAssetsLevel1ToLevel2TransfersAmount	0
CY2021Q3	us-gaap	Fair Value Liabilities Level2 To Level1 Transfers Amount FairValueLiabilitiesLevel2ToLevel1TransfersAmount	0
CY2020Q3	us-gaap	Fair Value Assets Level2 To Level1 Transfers Amount FairValueAssetsLevel2ToLevel1TransfersAmount	0
CY2020Q3	us-gaap	Fair Value Assets Level1 To Level2 Transfers Amount FairValueAssetsLevel1ToLevel2TransfersAmount	0
CY2020Q3	us-gaap	Fair Value Liabilities Level2 To Level1 Transfers Amount FairValueLiabilitiesLevel2ToLevel1TransfersAmount	0
CY2021Q3	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Value FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue	0
CY2020Q3	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Value FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue	0
	us-gaap	Number Of Reportable Segments NumberOfReportableSegments	1
CY2021Q3	us-gaap	Goodwill Goodwill	67071000
CY2021Q3	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	7588000
CY2021Q3	us-gaap	Assets Assets	5623193000
CY2020Q4	us-gaap	Goodwill Goodwill	66062000
CY2020Q4	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	7727000
CY2020Q4	us-gaap	Assets Assets	4912306000
CY2021Q3	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	38273000
CY2021Q3	fisi	Provision Benefit For Credit Losses ProvisionBenefitForCreditLosses	-541000
CY2021Q3	us-gaap	Noninterest Income NoninterestIncome	12083000
CY2021Q3	us-gaap	Noninterest Expense NoninterestExpense	29169000
CY2021Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	21728000
CY2021Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	4553000
CY2021Q3	us-gaap	Net Income Loss NetIncomeLoss	17175000
	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	113862000
	fisi	Provision Benefit For Credit Losses ProvisionBenefitForCreditLosses	-7144000
	us-gaap	Noninterest Income NoninterestIncome	35232000
	us-gaap	Noninterest Expense NoninterestExpense	82853000
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	73385000
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	15300000
	us-gaap	Net Income Loss NetIncomeLoss	58085000
CY2020Q3	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	35499000
	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	102804000
	fisi	Provision Benefit For Credit Losses ProvisionBenefitForCreditLosses	21689000
	us-gaap	Noninterest Income NoninterestIncome	31840000
	us-gaap	Noninterest Expense NoninterestExpense	82720000
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	30235000
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	5703000
	us-gaap	Net Income Loss NetIncomeLoss	24532000

Files In Submission

Name	View Source	Status
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0000950170-21-003405-index.html	Edgar Link	pending
0000950170-21-003405.txt	Edgar Link	pending
0000950170-21-003405-xbrl.zip	Edgar Link	pending
FilingSummary.xml	Edgar Link	unprocessable
Financial_Report.xlsx	Edgar Link	pending
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fisi-20210930_def.xml	Edgar Link	unprocessable
fisi-20210930_htm.xml	Edgar Link	completed
fisi-20210930_lab.xml	Edgar Link	unprocessable
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fisi-ex31_1.htm	Edgar Link	pending
fisi-ex31_2.htm	Edgar Link	pending
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MetaLinks.json	Edgar Link	pending
R1.htm	Edgar Link	pending
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report.css	Edgar Link	pending
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$FISI
FINANCIAL INSTITUTIONS INC Stock $fisi

2021 Q4 Form 10-Q Financial Statement

#000095017021003405 Filed on November 08, 2021

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$FISI FINANCIAL INSTITUTIONS INC Stock $fisi

2021 Q4 Form 10-Q Financial Statement

#000095017021003405 Filed on November 08, 2021

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$FISI
FINANCIAL INSTITUTIONS INC Stock $fisi