$FISI
FINANCIAL INSTITUTIONS INC Stock $fisi

$fisi Overview Financials Valuation SEC Filings Company Website

2021 Form 10-K Financial Statement

#000095017022003353 Filed on March 10, 2022

Income Statement

Concept	2021	2020 Q4	2020
Revenue	$167.2M		$161.3M
YoY Change	3.66%		-4.44%
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	$8.050M	$1.970M	$7.890M
YoY Change	2.03%	-1.01%	-3.9%
% of Gross Profit
Operating Expenses
YoY Change
Operating Profit
YoY Change
Interest Expense	$12.48M		$22.31M
YoY Change	-44.09%		-42.62%
% of Operating Profit
Other Income/Expense, Net
YoY Change
Pretax Income	$97.22M	$15.49M	$45.72M
YoY Change	112.63%	15.42%	-23.05%
Income Tax	$19.53M	$1.690M	$7.391M
% Of Pretax Income	20.08%	10.91%	16.16%
Net Earnings	$77.70M	$13.80M	$38.33M
YoY Change	102.69%	5.26%	-21.55%
Net Earnings / Revenue	46.47%		23.76%
Basic Earnings Per Share	$4.81		$2.30
Diluted Earnings Per Share	$4.78	$858.2K	$2.30
COMMON SHARES
Basic Shares Outstanding	15.84M		16.02M
Diluted Shares Outstanding	15.94M		16.06M

Balance Sheet

Concept	2021	2020 Q4	2020
SHORT-TERM ASSETS
Cash & Short-Term Investments
YoY Change
Cash & Equivalents		$93.88M
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	$62.20M	$40.61M	$80.50M
YoY Change	-22.73%	-1.97%	-4.39%
Goodwill		$66.06M
YoY Change		0.0%
Intangibles
YoY Change
Long-Term Investments
YoY Change
Other Assets	$6.200M		$6.200M
YoY Change	0.0%		40.91%
Total Long-Term Assets
YoY Change
TOTAL ASSETS
Total Short-Term Assets
Total Long-Term Assets
Total Assets	$5.521B	$4.912B	$4.912B
YoY Change	12.39%	12.05%	12.05%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable
YoY Change
Accrued Expenses	$23.90M	$21.50M	$21.50M
YoY Change	11.16%	-5.7%	-5.7%
Deferred Revenue
YoY Change
Short-Term Debt		$5.300M
YoY Change		-98.08%
Long-Term Debt Due
YoY Change
Total Short-Term Liabilities	$23.90M	$21.50M	$21.50M
YoY Change	11.16%	-5.7%	-5.7%
LONG-TERM LIABILITIES
Long-Term Debt	$73.90M	$73.60M	$73.60M
YoY Change	0.41%	87.28%	87.28%
Other Long-Term Liabilities	$60.80M	$65.10M	$65.10M
YoY Change	-6.61%	25.19%	25.19%
Total Long-Term Liabilities	$134.7M	$138.7M	$138.7M
YoY Change	-2.88%	51.92%	51.92%
TOTAL LIABILITIES
Total Short-Term Liabilities	$23.90M	$21.50M	$21.50M
Total Long-Term Liabilities	$134.7M	$138.7M	$138.7M
Total Liabilities	$5.016B	$4.444B	$4.444B
YoY Change	12.86%	12.64%	12.64%
SHAREHOLDERS EQUITY
Retained Earnings		$324.9M
YoY Change		3.67%
Common Stock		$161.0K
YoY Change		0.0%
Preferred Stock
YoY Change
Treasury Stock (at cost)		$1.222M
YoY Change		-38.13%
Treasury Stock Shares		$57.63K
Shareholders Equity	$505.1M	$468.4M	$468.4M
YoY Change
Total Liabilities & Shareholders Equity	$5.521B	$4.912B	$4.912B
YoY Change	12.39%	12.05%	12.05%

Cashflow Statement

Concept	2021	2020 Q4	2020
OPERATING ACTIVITIES
Net Income	$77.70M	$13.80M	$38.33M
YoY Change	102.69%	5.26%	-21.55%
Depreciation, Depletion And Amortization	$8.050M	$1.970M	$7.890M
YoY Change	2.03%	-1.01%	-3.9%
Cash From Operating Activities	$72.96M	$23.16M	$43.46M
YoY Change	67.9%	39.94%	-24.7%
INVESTING ACTIVITIES
Capital Expenditures	$9.403M	-$1.460M	$4.264M
YoY Change	120.52%	14.96%	17.18%
Acquisitions	$1.420M
YoY Change
Other Investing Activities	$3.510M	-$153.0M	$519.0K
YoY Change	576.3%	124.11%	44.17%
Cash From Investing Activities	-$633.4M	-$154.5M	-$531.1M
YoY Change	19.27%	122.12%	2047.22%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net	$9.235M		$209.0K
YoY Change	4318.66%		-28.67%
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	545.7M	-56.88M	468.5M
YoY Change	16.47%	-295.33%	-2156.38%
NET CHANGE
Cash From Operating Activities	72.96M	23.16M	43.46M
Cash From Investing Activities	-633.4M	-154.5M	-531.1M
Cash From Financing Activities	545.7M	-56.88M	468.5M
Net Change In Cash	-14.77M	-188.2M	-19.07M
YoY Change	-22.57%	688.35%	-287.1%
FREE CASH FLOW
Cash From Operating Activities	$72.96M	$23.16M	$43.46M
Capital Expenditures	$9.403M	-$1.460M	$4.264M
Free Cash Flow	$63.56M	$24.62M	$39.19M
YoY Change	62.18%	38.16%	-27.52%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value
CY2020	us-gaap	Payments For Repurchase Of Preferred Stock And Preference Stock PaymentsForRepurchaseOfPreferredStockAndPreferenceStock
CY2019Q4	us-gaap	Operating Lease Liability Statement Of Financial Position Extensible List OperatingLeaseLiabilityStatementOfFinancialPositionExtensibleList	http://fasb.org/us-gaap/2021-01-31#OtherLiabilities
CY2021Q4	us-gaap	Operating Lease Right Of Use Asset Statement Of Financial Position Extensible List OperatingLeaseRightOfUseAssetStatementOfFinancialPositionExtensibleList	http://fasb.org/us-gaap/2021-01-31#OtherAssets
CY2020Q4	us-gaap	Financing Receivable Originated Three Years Before Latest Fiscal Year FinancingReceivableOriginatedThreeYearsBeforeLatestFiscalYear
CY2019Q4	us-gaap	Operating Lease Right Of Use Asset Statement Of Financial Position Extensible List OperatingLeaseRightOfUseAssetStatementOfFinancialPositionExtensibleList	http://fasb.org/us-gaap/2021-01-31#OtherAssets
CY2020Q4	fisi	Financing Receivable After Deferred Income Offset Amount FinancingReceivableAfterDeferredIncomeOffsetAmount
CY2021Q4	us-gaap	Operating Lease Liability Statement Of Financial Position Extensible List OperatingLeaseLiabilityStatementOfFinancialPositionExtensibleList	http://fasb.org/us-gaap/2021-01-31#OtherLiabilities
CY2020	fisi	Number Of Years Used For Compensation Calculation NumberOfYearsUsedForCompensationCalculation	P5Y
CY2020Q4	fisi	Financing Receivable After Deferred Income Offset Amount FinancingReceivableAfterDeferredIncomeOffsetAmount
CY2020Q4	us-gaap	Operating Lease Right Of Use Asset Statement Of Financial Position Extensible List OperatingLeaseRightOfUseAssetStatementOfFinancialPositionExtensibleList	http://fasb.org/us-gaap/2021-01-31#OtherAssets
CY2021	dei	Amendment Flag AmendmentFlag	false
CY2019	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired
CY2020Q4	us-gaap	Operating Lease Liability Statement Of Financial Position Extensible List OperatingLeaseLiabilityStatementOfFinancialPositionExtensibleList	http://fasb.org/us-gaap/2021-01-31#OtherLiabilities
CY2020Q4	fisi	Financing Receivable After Deferred Income Offset Amount FinancingReceivableAfterDeferredIncomeOffsetAmount
CY2021	dei	Entity Central Index Key EntityCentralIndexKey	0000862831
CY2020Q4	us-gaap	Operating Lease Right Of Use Asset Statement Of Financial Position Extensible List OperatingLeaseRightOfUseAssetStatementOfFinancialPositionExtensibleList	http://fasb.org/us-gaap/2021-01-31#OtherAssets
CY2021Q4	us-gaap	Financing Receivable Originated Two Years Before Latest Fiscal Year FinancingReceivableOriginatedTwoYearsBeforeLatestFiscalYear
CY2021	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	FY
CY2021	us-gaap	Proceeds From Sale Of Held To Maturity Securities ProceedsFromSaleOfHeldToMaturitySecurities	0
CY2021	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-31
CY2021Q4	us-gaap	Financing Receivable Originated Three Years Before Latest Fiscal Year FinancingReceivableOriginatedThreeYearsBeforeLatestFiscalYear
CY2020Q4	fisi	Financing Receivable After Deferred Income Offset Amount FinancingReceivableAfterDeferredIncomeOffsetAmount
CY2019	us-gaap	Payments For Repurchase Of Preferred Stock And Preference Stock PaymentsForRepurchaseOfPreferredStockAndPreferenceStock
CY2020Q4	us-gaap	Commitments And Contingencies CommitmentsAndContingencies
CY2021	fisi	Proceeds From Loans Sold To Others ProceedsFromLoansSoldToOthers
CY2020Q4	us-gaap	Operating Lease Liability Statement Of Financial Position Extensible List OperatingLeaseLiabilityStatementOfFinancialPositionExtensibleList	http://fasb.org/us-gaap/2021-01-31#OtherLiabilities
CY2020Q4	us-gaap	Financing Receivable Originated Three Years Before Latest Fiscal Year FinancingReceivableOriginatedThreeYearsBeforeLatestFiscalYear
CY2021Q4	us-gaap	Financing Receivable Originated Three Years Before Latest Fiscal Year FinancingReceivableOriginatedThreeYearsBeforeLatestFiscalYear
CY2019	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt
CY2021	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt
CY2021Q4	us-gaap	Commitments And Contingencies CommitmentsAndContingencies
CY2020	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired
CY2021	dei	Document Type DocumentType	10-K
CY2021	dei	Document Annual Report DocumentAnnualReport	true
CY2021	dei	Document Period End Date DocumentPeriodEndDate	2021-12-31
CY2021	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2021
CY2021	dei	Document Transition Report DocumentTransitionReport	false
CY2021	dei	Entity File Number EntityFileNumber	000-26481
CY2021	dei	Entity Registrant Name EntityRegistrantName	FINANCIAL INSTITUTIONS, INC.
CY2021	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	NY
CY2021	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	16-0816610
CY2021	dei	Entity Address Address Line1 EntityAddressAddressLine1	220 LIBERTY STREET
CY2021	dei	Entity Address City Or Town EntityAddressCityOrTown	WARSAW
CY2021	dei	Entity Address State Or Province EntityAddressStateOrProvince	NY
CY2021	dei	Entity Address Postal Zip Code EntityAddressPostalZipCode	14569
CY2021	dei	City Area Code CityAreaCode	585
CY2021	dei	Local Phone Number LocalPhoneNumber	786-1100
CY2021	dei	Security12b Title Security12bTitle	Common stock, par value $0.01 per share
CY2021	dei	Trading Symbol TradingSymbol	FISI
CY2021	dei	Security Exchange Name SecurityExchangeName	NASDAQ
CY2021	dei	Entity Well Known Seasoned Issuer EntityWellKnownSeasonedIssuer	No
CY2021	dei	Entity Voluntary Filers EntityVoluntaryFilers	No
CY2021	dei	Entity Current Reporting Status EntityCurrentReportingStatus	Yes
CY2021	dei	Entity Interactive Data Current EntityInteractiveDataCurrent	Yes
CY2021	dei	Entity Filer Category EntityFilerCategory	Accelerated Filer
CY2021	dei	Entity Small Business EntitySmallBusiness	false
CY2021	dei	Entity Emerging Growth Company EntityEmergingGrowthCompany	false
CY2021	dei	Icfr Auditor Attestation Flag IcfrAuditorAttestationFlag	true
CY2021	dei	Entity Shell Company EntityShellCompany	false
CY2021Q2	dei	Entity Public Float EntityPublicFloat	466346000
CY2022Q1	dei	Entity Common Stock Shares Outstanding EntityCommonStockSharesOutstanding	15526641
CY2021	dei	Auditor Firm AuditorFirmId	49
CY2021	dei	Auditor Name AuditorName	RSM US LLP
CY2021	dei	Auditor Location AuditorLocation	Chicago, Illinois
CY2021Q4	us-gaap	Cash And Due From Banks CashAndDueFromBanks	79112000
CY2020Q4	us-gaap	Cash And Due From Banks CashAndDueFromBanks	93878000
CY2021Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	1178515000
CY2020Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	628059000
CY2021Q4	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss DebtSecuritiesHeldToMaturityAllowanceForCreditLoss	5000
CY2020Q4	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss DebtSecuritiesHeldToMaturityAllowanceForCreditLoss	7000
CY2021Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	209820000
CY2020Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	282035000
CY2021Q4	fisi	Held To Maturity Securities Net HeldToMaturitySecuritiesNet	205581000
CY2020Q4	fisi	Held To Maturity Securities Net HeldToMaturitySecuritiesNet	271966000
CY2021Q4	us-gaap	Loans Receivable Held For Sale Net Not Part Of Disposal Group LoansReceivableHeldForSaleNetNotPartOfDisposalGroup	6202000
CY2020Q4	us-gaap	Loans Receivable Held For Sale Net Not Part Of Disposal Group LoansReceivableHeldForSaleNetNotPartOfDisposalGroup	4305000
CY2021Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	39676000
CY2020Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	52420000
CY2021Q4	us-gaap	Loans And Leases Receivable Net Reported Amount LoansAndLeasesReceivableNetReportedAmount	3639760000
CY2020Q4	us-gaap	Loans And Leases Receivable Net Reported Amount LoansAndLeasesReceivableNetReportedAmount	3542718000
CY2021Q4	us-gaap	Bank Owned Life Insurance BankOwnedLifeInsurance	123898000
CY2020Q4	us-gaap	Bank Owned Life Insurance BankOwnedLifeInsurance	100895000
CY2021Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	40111000
CY2020Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	40610000
CY2021Q4	us-gaap	Intangible Assets Net Including Goodwill IntangibleAssetsNetIncludingGoodwill	74400000
CY2020Q4	us-gaap	Intangible Assets Net Including Goodwill IntangibleAssetsNetIncludingGoodwill	73789000
CY2021Q4	us-gaap	Other Assets OtherAssets	173200000
CY2020Q4	us-gaap	Other Assets OtherAssets	156086000
CY2021Q4	us-gaap	Assets Assets	5520779000
CY2020Q4	us-gaap	Assets Assets	4912306000
CY2021Q4	us-gaap	Noninterest Bearing Deposit Liabilities NoninterestBearingDepositLiabilities	1107561000
CY2020Q4	us-gaap	Noninterest Bearing Deposit Liabilities NoninterestBearingDepositLiabilities	1018549000
CY2021Q4	us-gaap	Interest Bearing Deposit Liabilities InterestBearingDepositLiabilities	864528000
CY2020Q4	us-gaap	Interest Bearing Deposit Liabilities InterestBearingDepositLiabilities	731885000
CY2021Q4	us-gaap	Deposits Savings Deposits DepositsSavingsDeposits	1933047000
CY2020Q4	us-gaap	Deposits Savings Deposits DepositsSavingsDeposits	1642340000
CY2021Q4	us-gaap	Time Deposits TimeDeposits	921954000
CY2020Q4	us-gaap	Time Deposits TimeDeposits	885593000
CY2021Q4	us-gaap	Deposits Deposits	4827090000
CY2020Q4	us-gaap	Deposits Deposits	4278367000
CY2021Q4	us-gaap	Short Term Borrowings ShortTermBorrowings	30000000
CY2020Q4	us-gaap	Short Term Borrowings ShortTermBorrowings	5300000
CY2021Q4	us-gaap	Unamortized Debt Issuance Expense UnamortizedDebtIssuanceExpense	1089000
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CY2021Q4	us-gaap	Liabilities Liabilities	5015637000
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CY2020Q4	us-gaap	Preferred Stock Value PreferredStockValue	17328000
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CY2021Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	50000000
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CY2020Q4	us-gaap	Common Stock Value CommonStockValue	161000
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CY2020Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	4912306000
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CY2021	us-gaap	Interest And Other Income InterestAndOtherIncome	216000
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CY2021	us-gaap	Insurance Services Revenue InsuranceServicesRevenue	5750000
CY2020	us-gaap	Insurance Services Revenue InsuranceServicesRevenue	4403000
CY2019	us-gaap	Insurance Services Revenue InsuranceServicesRevenue	4570000
CY2021	fisi	Card Interchange Income CardInterchangeIncome	8498000
CY2020	fisi	Card Interchange Income CardInterchangeIncome	7281000
CY2019	fisi	Card Interchange Income CardInterchangeIncome	6779000
CY2021	us-gaap	Brokerage Commissions Revenue BrokerageCommissionsRevenue	11672000
CY2020	us-gaap	Brokerage Commissions Revenue BrokerageCommissionsRevenue	9535000
CY2019	us-gaap	Brokerage Commissions Revenue BrokerageCommissionsRevenue	9187000
CY2021	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	2947000
CY2020	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	1902000
CY2019	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	1758000
CY2021	fisi	Noninterest Income Investments In Limited Partnerships NoninterestIncomeInvestmentsInLimitedPartnerships	2081000
CY2020	fisi	Noninterest Income Investments In Limited Partnerships NoninterestIncomeInvestmentsInLimitedPartnerships	104000
CY2019	fisi	Noninterest Income Investments In Limited Partnerships NoninterestIncomeInvestmentsInLimitedPartnerships	352000
CY2021	fisi	Noninterest Income Loan Servicing NoninterestIncomeLoanServicing	415000
CY2020	fisi	Noninterest Income Loan Servicing NoninterestIncomeLoanServicing	249000
CY2019	fisi	Noninterest Income Loan Servicing NoninterestIncomeLoanServicing	432000
CY2021	us-gaap	Derivative Gain Loss On Derivative Net DerivativeGainLossOnDerivativeNet	2695000
CY2020	us-gaap	Derivative Gain Loss On Derivative Net DerivativeGainLossOnDerivativeNet	5521000
CY2019	us-gaap	Derivative Gain Loss On Derivative Net DerivativeGainLossOnDerivativeNet	2274000
CY2021	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	2950000
CY2020	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	3858000
CY2019	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	1352000
CY2021	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	71000
CY2020	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	1599000
CY2019	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	1677000
CY2021	us-gaap	Gain Loss On Sale Of Other Assets GainLossOnSaleOfOtherAssets	441000
CY2020	us-gaap	Gain Loss On Sale Of Other Assets GainLossOnSaleOfOtherAssets	-61000
CY2019	us-gaap	Gain Loss On Sale Of Other Assets GainLossOnSaleOfOtherAssets	29000
CY2021	fisi	Gain Loss On Tax Credit Investments GainLossOnTaxCreditInvestments	-431000
CY2020	fisi	Gain Loss On Tax Credit Investments GainLossOnTaxCreditInvestments	-275000
CY2019	fisi	Gain Loss On Tax Credit Investments GainLossOnTaxCreditInvestments	-528000
CY2021	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	4246000
CY2020	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	4250000
CY2019	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	5258000
CY2021	us-gaap	Noninterest Income NoninterestIncome	46906000
CY2020	us-gaap	Noninterest Income NoninterestIncome	43176000
CY2019	us-gaap	Noninterest Income NoninterestIncome	40381000
CY2021	us-gaap	Labor And Related Expense LaborAndRelatedExpense	60893000
CY2020	us-gaap	Labor And Related Expense LaborAndRelatedExpense	59336000
CY2019	us-gaap	Labor And Related Expense LaborAndRelatedExpense	56330000
CY2021	us-gaap	Occupancy Net OccupancyNet	14371000
CY2020	us-gaap	Occupancy Net OccupancyNet	13655000
CY2019	us-gaap	Occupancy Net OccupancyNet	13552000
CY2021	us-gaap	Professional Fees ProfessionalFees	6535000
CY2020	us-gaap	Professional Fees ProfessionalFees	6326000
CY2019	us-gaap	Professional Fees ProfessionalFees	5424000
CY2021	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	14112000
CY2020	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	11645000
CY2019	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	9983000
CY2021	us-gaap	Supplies And Postage Expense SuppliesAndPostageExpense	1769000
CY2020	us-gaap	Supplies And Postage Expense SuppliesAndPostageExpense	1975000
CY2019	us-gaap	Supplies And Postage Expense SuppliesAndPostageExpense	2036000
CY2021	us-gaap	Federal Deposit Insurance Corporation Premium Expense FederalDepositInsuranceCorporationPremiumExpense	2624000
CY2020	us-gaap	Federal Deposit Insurance Corporation Premium Expense FederalDepositInsuranceCorporationPremiumExpense	2242000
CY2019	us-gaap	Federal Deposit Insurance Corporation Premium Expense FederalDepositInsuranceCorporationPremiumExpense	1005000
CY2021	us-gaap	Marketing And Advertising Expense MarketingAndAdvertisingExpense	1704000
CY2020	us-gaap	Marketing And Advertising Expense MarketingAndAdvertisingExpense	2609000
CY2019	us-gaap	Marketing And Advertising Expense MarketingAndAdvertisingExpense	3577000
CY2021	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	1060000
CY2020	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	1134000
CY2019	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	1250000
CY2021	us-gaap	Restructuring Charges RestructuringCharges	111000
CY2020	us-gaap	Restructuring Charges RestructuringCharges	1492000
CY2021	us-gaap	Other Noninterest Expense OtherNoninterestExpense	9571000
CY2020	us-gaap	Other Noninterest Expense OtherNoninterestExpense	8840000
CY2019	us-gaap	Other Noninterest Expense OtherNoninterestExpense	9671000
CY2021	us-gaap	Noninterest Expense NoninterestExpense	112750000
CY2020	us-gaap	Noninterest Expense NoninterestExpense	109254000
CY2019	us-gaap	Noninterest Expense NoninterestExpense	102828000
CY2021	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	97222000
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	45723000
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	59421000
CY2021	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	19525000
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	7391000
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	10559000
CY2021	us-gaap	Net Income Loss NetIncomeLoss	77697000
CY2020	us-gaap	Net Income Loss NetIncomeLoss	38332000
CY2019	us-gaap	Net Income Loss NetIncomeLoss	48862000
CY2021	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	1460000
CY2020	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	1461000
CY2019	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	1461000
CY2021	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	76237000
CY2020	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	36871000
CY2019	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	47401000
CY2021	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	4.81
CY2020	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.30
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.97
CY2021	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	4.78
CY2020	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.30
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.96
CY2021	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.08
CY2020	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.04
CY2019	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.00
CY2021	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	15841000
CY2020	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	16022000
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	15972000
CY2021	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	15937000
CY2020	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	16063000
CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	16031000
CY2021	us-gaap	Net Income Loss NetIncomeLoss	77697000
CY2020	us-gaap	Net Income Loss NetIncomeLoss	38332000
CY2019	us-gaap	Net Income Loss NetIncomeLoss	48862000
CY2021	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	-19714000
CY2020	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	13870000
CY2019	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	9323000
CY2021	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax	1476000
CY2020	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax	202000
CY2019	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax	-242000
CY2021	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-2903000
CY2020	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-2569000
CY2019	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-470000
CY2021	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-15335000
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	16641000
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	9551000
CY2021	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	62362000
CY2020	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	54973000
CY2019	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	58413000
CY2018Q4	us-gaap	Stockholders Equity StockholdersEquity	396293000
CY2019	us-gaap	Net Income Loss NetIncomeLoss	48862000
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	9551000
CY2019	us-gaap	Stock Issued During Period Value New Issues StockIssuedDuringPeriodValueNewIssues	1151000
CY2019	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	293000
CY2019	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	1406000
CY2019	us-gaap	Stock Granted During Period Value Sharebased Compensation StockGrantedDuringPeriodValueSharebasedCompensation	125000
CY2019	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.00
CY2019	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	15977000
CY2019Q4	us-gaap	Stockholders Equity StockholdersEquity	438947000
CY2020	us-gaap	Net Income Loss NetIncomeLoss	38332000
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	16641000
CY2020	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	209000
CY2020	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	1333000
CY2020	us-gaap	Stock Granted During Period Value Sharebased Compensation StockGrantedDuringPeriodValueSharebasedCompensation	165000
CY2020	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.04
CY2020	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	16666000
CY2020Q4	us-gaap	Stockholders Equity StockholdersEquity	468363000
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
CY2021	us-gaap	Profit Loss ProfitLoss	77697000
CY2020	us-gaap	Profit Loss ProfitLoss	38332000
CY2019	us-gaap	Profit Loss ProfitLoss	48862000
CY2021	us-gaap	Depreciation And Amortization DepreciationAndAmortization	8049000
CY2020	us-gaap	Depreciation And Amortization DepreciationAndAmortization	7893000
CY2019	us-gaap	Depreciation And Amortization DepreciationAndAmortization	8213000
CY2021	us-gaap	Accretion Amortization Of Discounts And Premiums Investments AccretionAmortizationOfDiscountsAndPremiumsInvestments	-5493000
CY2020	us-gaap	Accretion Amortization Of Discounts And Premiums Investments AccretionAmortizationOfDiscountsAndPremiumsInvestments	-3474000
CY2019	us-gaap	Accretion Amortization Of Discounts And Premiums Investments AccretionAmortizationOfDiscountsAndPremiumsInvestments	-2069000
CY2021	fisi	Provision For Credit Losses ProvisionForCreditLosses	-8336000
CY2020	fisi	Provision For Credit Losses ProvisionForCreditLosses	27184000
CY2019	fisi	Provision For Credit Losses ProvisionForCreditLosses	8044000
CY2021	us-gaap	Share Based Compensation ShareBasedCompensation	1743000
CY2020	us-gaap	Share Based Compensation ShareBasedCompensation	1333000
CY2019	us-gaap	Share Based Compensation ShareBasedCompensation	1406000
CY2021	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	5218000
CY2020	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-4523000
CY2019	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	369000
CY2021	us-gaap	Proceeds From Sale Of Loans Held For Sale ProceedsFromSaleOfLoansHeldForSale	81334000
CY2020	us-gaap	Proceeds From Sale Of Loans Held For Sale ProceedsFromSaleOfLoansHeldForSale	97238000
CY2019	us-gaap	Proceeds From Sale Of Loans Held For Sale ProceedsFromSaleOfLoansHeldForSale	41479000
CY2021	us-gaap	Payments For Origination And Purchases Of Loans Held For Sale PaymentsForOriginationAndPurchasesOfLoansHeldForSale	80281000
CY2020	us-gaap	Payments For Origination And Purchases Of Loans Held For Sale PaymentsForOriginationAndPurchasesOfLoansHeldForSale	93461000
CY2019	us-gaap	Payments For Origination And Purchases Of Loans Held For Sale PaymentsForOriginationAndPurchasesOfLoansHeldForSale	41626000
CY2021	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	2947000
CY2020	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	1902000
CY2019	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	1758000
CY2021	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	2950000
CY2020	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	3858000
CY2019	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	1352000
CY2021	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	71000
CY2020	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	1599000
CY2019	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	1677000
CY2021	us-gaap	Gain Loss On Sale Of Other Assets GainLossOnSaleOfOtherAssets	441000
CY2020	us-gaap	Gain Loss On Sale Of Other Assets GainLossOnSaleOfOtherAssets	-61000
CY2019	us-gaap	Gain Loss On Sale Of Other Assets GainLossOnSaleOfOtherAssets	29000
CY2021	fisi	Noncash Restructuring Charges Against Assets NoncashRestructuringChargesAgainstAssets	392000
CY2020	fisi	Noncash Restructuring Charges Against Assets NoncashRestructuringChargesAgainstAssets	202000
CY2019	fisi	Noncash Restructuring Charges Against Assets NoncashRestructuringChargesAgainstAssets	0
CY2021	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	9342000
CY2020	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	37565000
CY2019	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	21263000
CY2021	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	-2596000
CY2020	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	10646000
CY2019	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	14973000
CY2021	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	72962000
CY2020	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	43455000
CY2019	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	57710000
CY2021	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	784064000
CY2020	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	396879000
CY2019	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	195660000
CY2021	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	18425000
CY2020	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	7345000
CY2019	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	23494000
CY2021	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	150919000
CY2020	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	97685000
CY2019	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	82358000
CY2021	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	83684000
CY2020	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	93046000
CY2019	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	83508000
CY2021	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	51891000
CY2020	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	107098000
CY2019	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	178059000
CY2020	us-gaap	Proceeds From Sale Of Held To Maturity Securities ProceedsFromSaleOfHeldToMaturitySecurities	52000
CY2019	us-gaap	Proceeds From Sale Of Held To Maturity Securities ProceedsFromSaleOfHeldToMaturitySecurities	0
CY2021	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	90058000
CY2020	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	390932000
CY2019	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	167234000
CY2020	fisi	Proceeds From Loans Sold To Others ProceedsFromLoansSoldToOthers	0
CY2019	fisi	Proceeds From Loans Sold To Others ProceedsFromLoansSoldToOthers	21077000
CY2021	us-gaap	Payments For Proceeds From Life Insurance Policies PaymentsForProceedsFromLifeInsurancePolicies	20056000
CY2020	us-gaap	Payments For Proceeds From Life Insurance Policies PaymentsForProceedsFromLifeInsurancePolicies	30051000
CY2019	us-gaap	Payments For Proceeds From Life Insurance Policies PaymentsForProceedsFromLifeInsurancePolicies	68000
CY2021	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	3510000
CY2020	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	519000
CY2019	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	360000
CY2021	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	9403000
CY2020	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	4264000
CY2019	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	3639000
CY2021	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	1420000
CY2021	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-633422000
CY2020	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-531071000
CY2019	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-24733000
CY2021	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	548723000
CY2020	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	722692000
CY2019	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	188768000
CY2021	us-gaap	Proceeds From Repayments Of Short Term Debt ProceedsFromRepaymentsOfShortTermDebt	24700000
CY2020	us-gaap	Proceeds From Repayments Of Short Term Debt ProceedsFromRepaymentsOfShortTermDebt	-270200000
CY2019	us-gaap	Proceeds From Repayments Of Short Term Debt ProceedsFromRepaymentsOfShortTermDebt	-194000000
CY2021	us-gaap	Payments For Repurchase Of Preferred Stock And Preference Stock PaymentsForRepurchaseOfPreferredStockAndPreferenceStock	43000
CY2020	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	35000000
CY2020	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	779000
CY2021	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	9235000
CY2020	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	209000
CY2019	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	293000
CY2021	us-gaap	Payments Of Dividends Preferred Stock And Preference Stock PaymentsOfDividendsPreferredStockAndPreferenceStock	1460000
CY2020	us-gaap	Payments Of Dividends Preferred Stock And Preference Stock PaymentsOfDividendsPreferredStockAndPreferenceStock	1461000
CY2019	us-gaap	Payments Of Dividends Preferred Stock And Preference Stock PaymentsOfDividendsPreferredStockAndPreferenceStock	1461000
CY2021	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	16991000
CY2020	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	16496000
CY2019	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	15799000
CY2021	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	545694000
CY2020	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	468547000
CY2019	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-22785000
CY2021	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	-14766000
CY2020	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	-19069000
CY2019	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	10192000
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
CY2018Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Including Disposal Group And Discontinued Operations CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations	102755000
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
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Including Disposal Group And Discontinued Operations CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations	112947000
CY2021	us-gaap	Use Of Estimates UseOfEstimates	<p style="margin-left:3.333%;text-indent:0.0%;font-size:10.0pt;margin-top:12.0pt;line-height:1.15;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;font-style:italic;">(b.) Use of Estimates</span></p><p style="margin-left:3.333%;text-indent:0.0%;font-size:10.0pt;margin-top:6.0pt;line-height:1.15;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;">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>
CY2021	us-gaap	Interest Paid Net InterestPaidNet	14709000
CY2020	us-gaap	Interest Paid Net InterestPaidNet	28875000
CY2019	us-gaap	Interest Paid Net InterestPaidNet	37225000
CY2021	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	10832000
CY2020	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	7462000
CY2019	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	9853000
CY2020	us-gaap	Transfer To Other Real Estate TransferToOtherRealEstate	2966000
CY2019	us-gaap	Transfer To Other Real Estate TransferToOtherRealEstate	557000
CY2021Q4	us-gaap	Dividends Payable Current And Noncurrent DividendsPayableCurrentAndNoncurrent	4624000
CY2020Q4	us-gaap	Dividends Payable Current And Noncurrent DividendsPayableCurrentAndNoncurrent	4535000
CY2019Q4	us-gaap	Dividends Payable Current And Noncurrent DividendsPayableCurrentAndNoncurrent	4365000
CY2019	fisi	Decrease Increase In Net Unsettled Security Purchases DecreaseIncreaseInNetUnsettledSecurityPurchases	-2650000
CY2019	fisi	Securities Transferred From Available For Sale To Held To Maturity To Available For Sale At Cost SecuritiesTransferredFromAvailableForSaleToHeldToMaturityToAvailableForSaleAtCost	26175000
CY2019	us-gaap	Stock Issued1 StockIssued1	1151000
CY2021	us-gaap	Stock Issued During Period Value Acquisitions StockIssuedDuringPeriodValueAcquisitions	301000
CY2021	us-gaap	Fair Value Of Assets Acquired FairValueOfAssetsAcquired	712000
CY2021	fisi	Days Past Due When Loans Are Generally Charged Off In Full In Days DaysPastDueWhenLoansAreGenerallyChargedOffInFullInDays	P120D
CY2021	fisi	Number Of Identified Portfolio Segments NumberOfIdentifiedPortfolioSegments	6
CY2021	fisi	Number Of Designated Segments NumberOfDesignatedSegments	6
CY2021	fisi	Days Past Due When Loans Are Generally Placed On Nonaccrual Status In Days DaysPastDueWhenLoansAreGenerallyPlacedOnNonaccrualStatusInDays	P90D
CY2021Q4	us-gaap	Other Real Estate OtherRealEstate	0
CY2020Q4	us-gaap	Other Real Estate OtherRealEstate	3000000.0
CY2021Q4	us-gaap	Federal Home Loan Bank Stock FederalHomeLoanBankStock	4400000
CY2020Q4	us-gaap	Federal Home Loan Bank Stock FederalHomeLoanBankStock	2600000
CY2021Q4	us-gaap	Federal Reserve Bank Stock FederalReserveBankStock	6400000
CY2020Q4	us-gaap	Federal Reserve Bank Stock FederalReserveBankStock	6100000
CY2021Q4	us-gaap	Investment Related Liabilities InvestmentRelatedLiabilities	20200000
CY2020Q4	us-gaap	Investment Related Liabilities InvestmentRelatedLiabilities	17500000
CY2021	us-gaap	Prior Period Reclassification Adjustment Description PriorPeriodReclassificationAdjustmentDescription	<p style="margin-left:3.333%;text-indent:0.0%;font-size:10.0pt;margin-top:12.0pt;line-height:1.15;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;font-style:italic;">(x.) Reclassifications</span></p><p style="margin-left:3.333%;text-indent:0.0%;font-size:10.0pt;margin-top:6.0pt;line-height:1.15;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 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
CY2021	us-gaap	Restructuring Charges RestructuringCharges	111000
CY2021	us-gaap	Effect On Future Cash Flows Amount EffectOnFutureCashFlowsAmount	400000
CY2020	fisi	Anticipates Annual Expense Savings Branch Closures AnticipatesAnnualExpenseSavingsBranchClosures	2700000
CY2021	us-gaap	Restructuring Costs RestructuringCosts	122000
CY2020	us-gaap	Restructuring Costs RestructuringCosts	1734000
CY2020	us-gaap	Restructuring Costs RestructuringCosts	1734000
CY2020	us-gaap	Payments For Restructuring PaymentsForRestructuring	287000
CY2020	us-gaap	Restructuring Reserve Period Increase Decrease RestructuringReservePeriodIncreaseDecrease	-202000
CY2020Q4	us-gaap	Restructuring Reserve RestructuringReserve	1245000
CY2021	us-gaap	Restructuring Costs RestructuringCosts	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
CY2021	us-gaap	Impairment Of Long Lived Assets Held For Use ImpairmentOfLongLivedAssetsHeldForUse	3200000
CY2020	us-gaap	Impairment Of Long Lived Assets Held For Use ImpairmentOfLongLivedAssetsHeldForUse	0
CY2021	fisi	Gain On Sale Of Long Lived Assets Held For Sale GainOnSaleOfLongLivedAssetsHeldForSale	111000
CY2021Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	1184835000
CY2021Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	8446000
CY2021Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	14766000
CY2021Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	1178515000
CY2021Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	205586000
CY2021Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Gain HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain	4683000
CY2021Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Loss HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss	449000
CY2021Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	209820000
CY2021Q4	fisi	Allowance For Credit Losses Amortized Cost AllowanceForCreditLossesAmortizedCost	-5000
CY2021Q4	fisi	Held To Maturity Securities Net HeldToMaturitySecuritiesNet	205581000
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
CY2021Q4	fisi	Debt Securities Available For Sale And Held To Maturity Restricted DebtSecuritiesAvailableForSaleAndHeldToMaturityRestricted	637600000
CY2020Q4	fisi	Debt Securities Available For Sale And Held To Maturity Restricted DebtSecuritiesAvailableForSaleAndHeldToMaturityRestricted	567400000
CY2021	us-gaap	Interest Income Securities Taxable InterestIncomeSecuritiesTaxable	16736000
CY2020	us-gaap	Interest Income Securities Taxable InterestIncomeSecuritiesTaxable	14186000
CY2019	us-gaap	Interest Income Securities Taxable InterestIncomeSecuritiesTaxable	14382000
CY2021	us-gaap	Interest Income Securities Tax Exempt InterestIncomeSecuritiesTaxExempt	2355000
CY2020	us-gaap	Interest Income Securities Tax Exempt InterestIncomeSecuritiesTaxExempt	3278000
CY2019	us-gaap	Interest Income Securities Tax Exempt InterestIncomeSecuritiesTaxExempt	4150000
CY2021	us-gaap	Interest And Dividend Income Securities InterestAndDividendIncomeSecurities	19091000
CY2020	us-gaap	Interest And Dividend Income Securities InterestAndDividendIncomeSecurities	17464000
CY2019	us-gaap	Interest And Dividend Income Securities InterestAndDividendIncomeSecurities	18532000
CY2021	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	51891000
CY2020	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	107098000
CY2019	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	178059000
CY2021	us-gaap	Debt Securities Available For Sale Realized Gain DebtSecuritiesAvailableForSaleRealizedGain	251000
CY2020	us-gaap	Debt Securities Available For Sale Realized Gain DebtSecuritiesAvailableForSaleRealizedGain	1642000
CY2019	us-gaap	Debt Securities Available For Sale Realized Gain DebtSecuritiesAvailableForSaleRealizedGain	2391000
CY2021	us-gaap	Debt Securities Available For Sale Realized Loss DebtSecuritiesAvailableForSaleRealizedLoss	180000
CY2020	us-gaap	Debt Securities Available For Sale Realized Loss DebtSecuritiesAvailableForSaleRealizedLoss	43000
CY2019	us-gaap	Debt Securities Available For Sale Realized Loss DebtSecuritiesAvailableForSaleRealizedLoss	714000
CY2021Q4	us-gaap	Available For Sale Securities Debt Maturities Within One Year Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost	1469000
CY2021Q4	us-gaap	Available For Sale Securities Debt Maturities Within One Year Fair Value AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue	1479000
CY2021Q4	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost	64526000
CY2021Q4	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	66843000
CY2021Q4	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost	178918000
CY2021Q4	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	182096000
CY2021Q4	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost	939922000
CY2021Q4	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue	928097000
CY2021Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	1184835000
CY2021Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	1178515000
CY2021Q4	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount	35419000
CY2021Q4	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Fair Value HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearFairValue	35700000
CY2021Q4	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsNetCarryingAmount	68054000
CY2021Q4	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	70227000
CY2021Q4	us-gaap	Held To Maturity Securities Debt Maturities After Five Through Ten Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsNetCarryingAmount	19209000
CY2021Q4	us-gaap	Held To Maturity Securities Debt Maturities After Five Through Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	19414000
CY2021Q4	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsNetCarryingAmount	82904000
CY2021Q4	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsFairValue	84479000
CY2021Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	205586000
CY2021Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	209820000
CY2021Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months	773484000
CY2021Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	10039000
CY2021Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger	172180000
CY2021Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	4727000
CY2021Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position DebtSecuritiesAvailableForSaleUnrealizedLossPosition	945664000
CY2021Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position Accumulated Loss DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss	14766000
CY2021Q4	fisi	Investment Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value InvestmentSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue	773484000
CY2021Q4	fisi	Investment Securities Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss InvestmentSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	10039000
CY2021Q4	fisi	Investment Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value InvestmentSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue	172180000
CY2021Q4	fisi	Investment Securities Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss InvestmentSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	4727000
CY2021Q4	fisi	Investment Securities Continuous Unrealized Loss Position Fair Value InvestmentSecuritiesContinuousUnrealizedLossPositionFairValue	945664000
CY2021Q4	fisi	Investment Securities Accumulated Unrecognized Holding Loss InvestmentSecuritiesAccumulatedUnrecognizedHoldingLoss	14766000
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
CY2021Q4	fisi	Investment Securities In Unrealized Loss Position Number Of Positions InvestmentSecuritiesInUnrealizedLossPositionNumberOfPositions	116
CY2020Q4	fisi	Investment Securities In Unrealized Loss Position Number Of Positions InvestmentSecuritiesInUnrealizedLossPositionNumberOfPositions	8
CY2021Q4	fisi	Investment Securities In Unrealized Loss Positions Twelve Months Or Longer Qualitative Disclosure Number Of Positions InvestmentSecuritiesInUnrealizedLossPositionsTwelveMonthsOrLongerQualitativeDisclosureNumberOfPositions	28
CY2021Q4	fisi	Investment Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value InvestmentSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue	172200000
CY2021Q4	fisi	Investment Securities Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss InvestmentSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	4700000
CY2021Q4	fisi	Investment Securities In Unrealized Loss Positions Less Than Twelve Months Qualitative Disclosure Number Of Positions InvestmentSecuritiesInUnrealizedLossPositionsLessThanTwelveMonthsQualitativeDisclosureNumberOfPositions	88
CY2021Q4	fisi	Investment Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value InvestmentSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue	773500000
CY2021Q4	fisi	Investment Securities Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss InvestmentSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	10000000.0
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	70
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
CY2021Q4	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	0
CY2021Q4	fisi	Residential Real Estate Mortgages Serviced For Others ResidentialRealEstateMortgagesServicedForOthers	272700000
CY2020Q4	fisi	Residential Real Estate Mortgages Serviced For Others ResidentialRealEstateMortgagesServicedForOthers	241700000
CY2021Q4	us-gaap	Escrow Deposit EscrowDeposit	4900000
CY2020Q4	us-gaap	Escrow Deposit EscrowDeposit	4500000
CY2020Q4	fisi	Mortgage Servicing Assets Before Valuation Allowance MortgageServicingAssetsBeforeValuationAllowance	1376000
CY2019Q4	fisi	Mortgage Servicing Assets Before Valuation Allowance MortgageServicingAssetsBeforeValuationAllowance	1129000
CY2018Q4	fisi	Mortgage Servicing Assets Before Valuation Allowance MortgageServicingAssetsBeforeValuationAllowance	1022000
CY2021	us-gaap	Servicing Asset At Fair Value Additions ServicingAssetAtFairValueAdditions	520000
CY2020	us-gaap	Servicing Asset At Fair Value Additions ServicingAssetAtFairValueAdditions	601000
CY2019	us-gaap	Servicing Asset At Fair Value Additions ServicingAssetAtFairValueAdditions	349000
CY2021	us-gaap	Amortization Of Mortgage Servicing Rights Ms Rs AmortizationOfMortgageServicingRightsMSRs	378000
CY2020	us-gaap	Amortization Of Mortgage Servicing Rights Ms Rs AmortizationOfMortgageServicingRightsMSRs	354000
CY2019	us-gaap	Amortization Of Mortgage Servicing Rights Ms Rs AmortizationOfMortgageServicingRightsMSRs	242000
CY2021Q4	fisi	Mortgage Servicing Assets Before Valuation Allowance MortgageServicingAssetsBeforeValuationAllowance	1518000
CY2020Q4	fisi	Mortgage Servicing Assets Before Valuation Allowance MortgageServicingAssetsBeforeValuationAllowance	1376000
CY2021Q4	fisi	Mortgage Servicing Assets Valuation Allowance MortgageServicingAssetsValuationAllowance	1000
CY2019Q4	fisi	Mortgage Servicing Assets Before Valuation Allowance MortgageServicingAssetsBeforeValuationAllowance	1129000
CY2020Q4	fisi	Mortgage Servicing Assets Valuation Allowance MortgageServicingAssetsValuationAllowance	56000
CY2021Q4	fisi	Mortgage Servicing Assets Net Of Valuation Allowance MortgageServicingAssetsNetOfValuationAllowance	1517000
CY2020Q4	fisi	Mortgage Servicing Assets Net Of Valuation Allowance MortgageServicingAssetsNetOfValuationAllowance	1320000
CY2019Q4	fisi	Mortgage Servicing Assets Net Of Valuation Allowance MortgageServicingAssetsNetOfValuationAllowance	1129000
CY2021Q4	us-gaap	Loans And Leases Receivable Gross Carrying Amount LoansAndLeasesReceivableGrossCarryingAmount	3631355000
CY2021Q4	fisi	Loans And Leases Receivable Deferred Loan Fees Costs LoansAndLeasesReceivableDeferredLoanFeesCosts	-48081000
CY2021Q4	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	3679436000
CY2021Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	39676000
CY2021Q4	us-gaap	Loans And Leases Receivable Net Reported Amount LoansAndLeasesReceivableNetReportedAmount	3639760000
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
CY2021Q4	us-gaap	Loans And Leases Receivable Related Parties LoansAndLeasesReceivableRelatedParties	44700000
CY2020Q4	us-gaap	Loans And Leases Receivable Related Parties LoansAndLeasesReceivableRelatedParties	32800000
CY2021	us-gaap	Loans And Leases Receivable Related Parties Additions LoansAndLeasesReceivableRelatedPartiesAdditions	19000000.0
CY2021	us-gaap	Loans And Leases Receivable Related Parties Proceeds LoansAndLeasesReceivableRelatedPartiesProceeds	7100000
CY2021Q4	us-gaap	Financing Receivable Recorded Investment Nonaccrual Status FinancingReceivableRecordedInvestmentNonaccrualStatus	11369000
CY2021Q4	us-gaap	Notes Receivable Gross NotesReceivableGross	3631355000
CY2021Q4	us-gaap	Financing Receivable Nonaccrual No Allowance FinancingReceivableNonaccrualNoAllowance	5611000
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
CY2021	us-gaap	Impaired Financing Receivable Interest Income Cash Basis Method ImpairedFinancingReceivableInterestIncomeCashBasisMethod	0
CY2020	us-gaap	Impaired Financing Receivable Interest Income Cash Basis Method ImpairedFinancingReceivableInterestIncomeCashBasisMethod	0
CY2019	us-gaap	Impaired Financing Receivable Interest Income Cash Basis Method ImpairedFinancingReceivableInterestIncomeCashBasisMethod	0
CY2021	us-gaap	Interest Income Operating InterestIncomeOperating	211000
CY2020	us-gaap	Interest Income Operating InterestIncomeOperating	430000
CY2019	us-gaap	Interest Income Operating InterestIncomeOperating	508000
CY2021	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	0
CY2020	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	0
CY2021	us-gaap	Financing Receivable Modifications Subsequent Default Number Of Contracts1 FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1	0
CY2020	us-gaap	Financing Receivable Modifications Subsequent Default Number Of Contracts1 FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1	0
CY2021	fisi	Days Past Due When Loans Are Generally Placed On Nonaccrual Status In Days DaysPastDueWhenLoansAreGenerallyPlacedOnNonaccrualStatusInDays	P90D
CY2020	fisi	Days Past Due When Loans Are Generally Placed On Nonaccrual Status In Days DaysPastDueWhenLoansAreGenerallyPlacedOnNonaccrualStatusInDays	P90D
CY2021Q4	fisi	Collateral Dependent Loans On Business Assets CollateralDependentLoansOnBusinessAssets	326000
CY2021Q4	fisi	Collateral Dependent Loans On Real Property CollateralDependentLoansOnRealProperty	38929000
CY2021Q4	fisi	Collateral Dependent Loans CollateralDependentLoans	39255000
CY2021Q4	fisi	Collateral Dependent Loan With Specific Reserve CollateralDependentLoanWithSpecificReserve	5771000
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
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
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	30482000
CY2020	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	21625000
CY2020	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	7810000
CY2020	fisi	Financing Receivable Allowance For Loan Losses Provision Credit FinancingReceivableAllowanceForLoanLossesProvisionCredit	26159000
CY2020Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	52420000
CY2018Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	33914000
CY2019	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	17811000
CY2019	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	6335000
CY2019	fisi	Financing Receivable Allowance For Loan Losses Provision Credit FinancingReceivableAllowanceForLoanLossesProvisionCredit	8044000
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	30482000
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses Individually Evaluated For Impairment1 FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1	693000
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses Collectively Evaluated For Impairment FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment	29789000
CY2019Q4	us-gaap	Notes Receivable Gross NotesReceivableGross	3179465000
CY2019Q4	us-gaap	Financing Receivable Individually Evaluated For Impairment FinancingReceivableIndividuallyEvaluatedForImpairment	4323000
CY2019Q4	us-gaap	Financing Receivable Collectively Evaluated For Impairment FinancingReceivableCollectivelyEvaluatedForImpairment	3175142000
CY2021Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	95031000
CY2020Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	103860000
CY2021Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	54920000
CY2020Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	63250000
CY2021Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	40111000
CY2020Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	40610000
CY2021	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0
CY2019	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0
CY2019Q4	us-gaap	Goodwill Goodwill	66062000
CY2020Q4	us-gaap	Goodwill Goodwill	66062000
CY2021Q4	us-gaap	Goodwill Goodwill	67071000
CY2021Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Next Twelve Months FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths	985000
CY2021Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Two FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo	910000
CY2021Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Three FiniteLivedIntangibleAssetsAmortizationExpenseYearThree	838000
CY2021Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Four FiniteLivedIntangibleAssetsAmortizationExpenseYearFour	766000
CY2021Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Five FiniteLivedIntangibleAssetsAmortizationExpenseYearFive	694000
CY2021	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
CY2021	us-gaap	Lessee Operating Sublease Option To Extend LesseeOperatingSubleaseOptionToExtend	One building lease was subleased with terms that extended through June 30, 2021
CY2020	fisi	Number Of Buildings Subleased NumberOfBuildingsSubleased	1
CY2021Q4	fisi	Operating Lease Right Of Use Asset Gross OperatingLeaseRightOfUseAssetGross	27063000
CY2020Q4	fisi	Operating Lease Right Of Use Asset Gross OperatingLeaseRightOfUseAssetGross	23697000
CY2021Q4	fisi	Operating Lease Right Of Use Asset Accumulated Amortization OperatingLeaseRightOfUseAssetAccumulatedAmortization	4993000
CY2020Q4	fisi	Operating Lease Right Of Use Asset Accumulated Amortization OperatingLeaseRightOfUseAssetAccumulatedAmortization	3741000
CY2021Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	22070000
CY2020Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	19956000
CY2021Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	23867000
CY2020Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	21507000
CY2021Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P24Y
CY2021Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.0371
CY2021	us-gaap	Operating Lease Cost OperatingLeaseCost	2830000
CY2020	us-gaap	Operating Lease Cost OperatingLeaseCost	2673000
CY2019	us-gaap	Operating Lease Cost OperatingLeaseCost	2758000
CY2021	us-gaap	Variable Lease Cost VariableLeaseCost	427000
CY2020	us-gaap	Variable Lease Cost VariableLeaseCost	410000
CY2019	us-gaap	Variable Lease Cost VariableLeaseCost	428000
CY2021	us-gaap	Sublease Income SubleaseIncome	23000
CY2020	us-gaap	Sublease Income SubleaseIncome	46000
CY2019	us-gaap	Sublease Income SubleaseIncome	46000
CY2021	us-gaap	Lease Cost LeaseCost	3234000
CY2020	us-gaap	Lease Cost LeaseCost	3037000
CY2019	us-gaap	Lease Cost LeaseCost	3140000
CY2021	us-gaap	Operating Lease Payments OperatingLeasePayments	2647000
CY2020	us-gaap	Operating Lease Payments OperatingLeasePayments	2599000
CY2019	us-gaap	Operating Lease Payments OperatingLeasePayments	2641000
CY2019	fisi	Initial Recognition Of Operating Lease Right Of Use Assets InitialRecognitionOfOperatingLeaseRightOfUseAssets	23275000
CY2019	fisi	Initial Recognition Of Operating Lease Liabilities InitialRecognitionOfOperatingLeaseLiabilities	23985000
CY2021	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	4251000
CY2020	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	477000
CY2019	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	620000
CY2021Q4	us-gaap	Lessee Operating Lease Liability Payments Due Next Rolling Twelve Months LesseeOperatingLeaseLiabilityPaymentsDueNextRollingTwelveMonths	2215000
CY2021Q4	us-gaap	Lessee Operating Lease Liability Payments Due In Rolling Year Two LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearTwo	1766000
CY2021Q4	us-gaap	Lessee Operating Lease Liability Payments Due In Rolling Year Three LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearThree	1452000
CY2021Q4	us-gaap	Lessee Operating Lease Liability Payments Due In Rolling Year Four LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearFour	1378000
CY2021Q4	us-gaap	Lessee Operating Lease Liability Payments Due In Rolling Year Five LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearFive	1299000
CY2021Q4	us-gaap	Lessee Operating Lease Liability Payments Due After Rolling Year Five LesseeOperatingLeaseLiabilityPaymentsDueAfterRollingYearFive	29575000
CY2021Q4	us-gaap	Lessee Operating Lease Liability Payments Due LesseeOperatingLeaseLiabilityPaymentsDue	37685000
CY2021Q4	us-gaap	Lessee Operating Lease Liability Undiscounted Excess Amount LesseeOperatingLeaseLiabilityUndiscountedExcessAmount	13818000
CY2021Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	23867000
CY2021Q4	fisi	Lessee Operating Lease Lease Not Yet Commenced LesseeOperatingLeaseLeaseNotYetCommenced	13800000
CY2021Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	22070000
CY2020Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	19956000
CY2021Q4	fisi	Tax Credit Investments TaxCreditInvestments	57010000
CY2020Q4	fisi	Tax Credit Investments TaxCreditInvestments	34370000
CY2021Q4	us-gaap	Derivative Fair Value Of Derivative Asset DerivativeFairValueOfDerivativeAsset	16504000
CY2020Q4	us-gaap	Derivative Fair Value Of Derivative Asset DerivativeFairValueOfDerivativeAsset	20120000
CY2021Q4	fisi	Collateral On Derivative Instruments CollateralOnDerivativeInstruments	4640000
CY2020Q4	fisi	Collateral On Derivative Instruments CollateralOnDerivativeInstruments	19630000
CY2021Q4	us-gaap	Other Assets Miscellaneous OtherAssetsMiscellaneous	72976000
CY2020Q4	us-gaap	Other Assets Miscellaneous OtherAssetsMiscellaneous	62010000
CY2021Q4	us-gaap	Other Assets OtherAssets	173200000
CY2020Q4	us-gaap	Other Assets OtherAssets	156086000
CY2021Q4	us-gaap	Noninterest Bearing Deposit Liabilities NoninterestBearingDepositLiabilities	1107561000
CY2020Q4	us-gaap	Noninterest Bearing Deposit Liabilities NoninterestBearingDepositLiabilities	1018549000
CY2021Q4	us-gaap	Interest Bearing Deposit Liabilities InterestBearingDepositLiabilities	864528000
CY2020Q4	us-gaap	Interest Bearing Deposit Liabilities InterestBearingDepositLiabilities	731885000
CY2021Q4	us-gaap	Deposits Savings Deposits DepositsSavingsDeposits	1933047000
CY2020Q4	us-gaap	Deposits Savings Deposits DepositsSavingsDeposits	1642340000
CY2021Q4	us-gaap	Time Deposit Maturities Year One TimeDepositMaturitiesYearOne	880892000
CY2020Q4	us-gaap	Time Deposit Maturities Year One TimeDepositMaturitiesYearOne	841581000
CY2021Q4	us-gaap	Time Deposit Maturities Year Two TimeDepositMaturitiesYearTwo	23572000
CY2020Q4	us-gaap	Time Deposit Maturities Year Two TimeDepositMaturitiesYearTwo	30847000
CY2021Q4	us-gaap	Time Deposit Maturities Year Three TimeDepositMaturitiesYearThree	9881000
CY2020Q4	us-gaap	Time Deposit Maturities Year Three TimeDepositMaturitiesYearThree	5186000
CY2021Q4	us-gaap	Time Deposit Maturities Year Four TimeDepositMaturitiesYearFour	6485000
CY2020Q4	us-gaap	Time Deposit Maturities Year Four TimeDepositMaturitiesYearFour	5417000
CY2021Q4	us-gaap	Time Deposit Maturities Year Five TimeDepositMaturitiesYearFive	1124000
CY2020Q4	us-gaap	Time Deposit Maturities Year Five TimeDepositMaturitiesYearFive	2562000
CY2020Q4	us-gaap	Time Deposit Maturities After Year Five TimeDepositMaturitiesAfterYearFive	0
CY2021Q4	us-gaap	Time Deposits TimeDeposits	921954000
CY2020Q4	us-gaap	Time Deposits TimeDeposits	885593000
CY2021Q4	us-gaap	Deposits Deposits	4827090000
CY2020Q4	us-gaap	Deposits Deposits	4278367000
CY2021Q4	us-gaap	Time Deposits100000 Or More TimeDeposits100000OrMore	220800000
CY2020Q4	us-gaap	Time Deposits100000 Or More TimeDeposits100000OrMore	200700000
CY2021	us-gaap	Interest Expense Demand Deposit Accounts InterestExpenseDemandDepositAccounts	1156000
CY2020	us-gaap	Interest Expense Demand Deposit Accounts InterestExpenseDemandDepositAccounts	1091000
CY2019	us-gaap	Interest Expense Demand Deposit Accounts InterestExpenseDemandDepositAccounts	1372000
CY2021	us-gaap	Interest Expense Savings Deposits InterestExpenseSavingsDeposits	3363000
CY2020	us-gaap	Interest Expense Savings Deposits InterestExpenseSavingsDeposits	4788000
CY2019	us-gaap	Interest Expense Savings Deposits InterestExpenseSavingsDeposits	4365000
CY2021	us-gaap	Interest Expense Time Deposits InterestExpenseTimeDeposits	3599000
CY2020	us-gaap	Interest Expense Time Deposits InterestExpenseTimeDeposits	11943000
CY2019	us-gaap	Interest Expense Time Deposits InterestExpenseTimeDeposits	22757000
CY2021	us-gaap	Interest Expense Deposits InterestExpenseDeposits	8118000
CY2020	us-gaap	Interest Expense Deposits InterestExpenseDeposits	17822000
CY2019	us-gaap	Interest Expense Deposits InterestExpenseDeposits	28494000
CY2021Q4	us-gaap	Federal Home Loan Bank Advances Maturities Summary Due Within One Year Of Balance Sheet Date FederalHomeLoanBankAdvancesMaturitiesSummaryDueWithinOneYearOfBalanceSheetDate	30000000
CY2020Q4	us-gaap	Federal Home Loan Bank Advances Maturities Summary Due Within One Year Of Balance Sheet Date FederalHomeLoanBankAdvancesMaturitiesSummaryDueWithinOneYearOfBalanceSheetDate	5300000
CY2021Q4	us-gaap	Subordinated Debt SubordinatedDebt	73911000
CY2020Q4	us-gaap	Subordinated Debt SubordinatedDebt	73623000
CY2021Q4	us-gaap	Debt Longterm And Shortterm Combined Amount DebtLongtermAndShorttermCombinedAmount	103911000
CY2020Q4	us-gaap	Debt Longterm And Shortterm Combined Amount DebtLongtermAndShorttermCombinedAmount	78923000
CY2021Q4	us-gaap	Short Term Debt Weighted Average Interest Rate ShortTermDebtWeightedAverageInterestRate	0.0034
CY2020Q4	us-gaap	Short Term Debt Weighted Average Interest Rate ShortTermDebtWeightedAverageInterestRate	0.0170
CY2020Q4	us-gaap	Line Of Credit LineOfCredit	0
CY2021Q4	us-gaap	Line Of Credit LineOfCredit	0
CY2021Q4	us-gaap	Interest Rate Cash Flow Hedge Gain Loss To Be Reclassified During Next12 Months Net InterestRateCashFlowHedgeGainLossToBeReclassifiedDuringNext12MonthsNet	53000
CY2021Q4	us-gaap	Capital Units Authorized CapitalUnitsAuthorized	50210000
CY2021Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	50000000
CY2021Q4	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	0.01
CY2021Q4	us-gaap	Preferred Stock Shares Authorized PreferredStockSharesAuthorized	210000
CY2021Q4	us-gaap	Preferred Stock Par Or Stated Value Per Share PreferredStockParOrStatedValuePerShare	100
CY2021Q4	us-gaap	Preferred Stock Shares Outstanding PreferredStockSharesOutstanding	172921
CY2021Q4	us-gaap	Preferred Stock Shares Issued PreferredStockSharesIssued	172921
CY2020Q4	us-gaap	Preferred Stock Shares Issued PreferredStockSharesIssued	173282
CY2020Q4	us-gaap	Preferred Stock Shares Outstanding PreferredStockSharesOutstanding	173282
CY2020Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	16099556
CY2021Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	16099556
CY2019Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	16099556
CY2020Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	16099556
CY2020Q4	us-gaap	Stock Repurchase Program Number Of Shares Authorized To Be Repurchased StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased	801879
CY2021	us-gaap	Stock Repurchased During Period Shares StockRepurchasedDuringPeriodShares	340688
CY2021	us-gaap	Treasury Stock Acquired Average Cost Per Share TreasuryStockAcquiredAverageCostPerShare	26.44
CY2020	us-gaap	Stock Repurchased During Period Shares StockRepurchasedDuringPeriodShares	0
CY2021Q4	us-gaap	Stock Repurchase Program Remaining Number Of Shares Authorized To Be Repurchased StockRepurchaseProgramRemainingNumberOfSharesAuthorizedToBeRepurchased	461191
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
CY2020	us-gaap	Other Comprehensive Income Loss Before Tax Portion Attributable To Parent OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent	22373000
CY2020	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	5732000
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	16641000
CY2019	us-gaap	Other Comprehensive Income Loss Before Tax Portion Attributable To Parent OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent	12664000
CY2019	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	3113000
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	9551000
CY2021	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Expiration Period SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod	P10Y
CY2021	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross	0
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross	0
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross	0
CY2021Q4	us-gaap	Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized	0
CY2021	us-gaap	Share Based Compensation ShareBasedCompensation	1743000
CY2020	us-gaap	Share Based Compensation ShareBasedCompensation	1333000
CY2019	us-gaap	Share Based Compensation ShareBasedCompensation	1406000
CY2021	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	11453000
CY2020	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	10041000
CY2019	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	8882000
CY2021	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	2854000
CY2020	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	1873000
CY2019	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	1308000
CY2021	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	14307000
CY2020	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	11914000
CY2019	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	10190000
CY2021	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-4384000
CY2020	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-3306000
CY2019	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-280000
CY2021	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	834000
CY2020	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	-1217000
CY2019	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	89000
CY2021	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	5218000
CY2020	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-4523000
CY2019	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	369000
CY2021	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	19525000
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	7391000
CY2020Q4	us-gaap	Defined Benefit Plan Fair Value Of Plan Assets DefinedBenefitPlanFairValueOfPlanAssets	102176000
CY2019Q4	us-gaap	Defined Benefit Plan Fair Value Of Plan Assets DefinedBenefitPlanFairValueOfPlanAssets	87827000
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	10559000
CY2021	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.210
CY2020	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.210
CY2019	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.210
CY2021	us-gaap	Effective Income Tax Rate Reconciliation Tax Exempt Income EffectiveIncomeTaxRateReconciliationTaxExemptIncome	-0.007
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Tax Exempt Income EffectiveIncomeTaxRateReconciliationTaxExemptIncome	-0.020
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Tax Exempt Income EffectiveIncomeTaxRateReconciliationTaxExemptIncome	-0.019
CY2021	fisi	Effective Income Tax Rate Reconciliation Tax Credit And Adjustments Percent EffectiveIncomeTaxRateReconciliationTaxCreditAndAdjustmentsPercent	-0.026
CY2020	fisi	Effective Income Tax Rate Reconciliation Tax Credit And Adjustments Percent EffectiveIncomeTaxRateReconciliationTaxCreditAndAdjustmentsPercent	-0.034
CY2019	fisi	Effective Income Tax Rate Reconciliation Tax Credit And Adjustments Percent EffectiveIncomeTaxRateReconciliationTaxCreditAndAdjustmentsPercent	-0.030
CY2021	fisi	Effective Income Tax Rate Reconciliation Non Taxable Earnings On Company Owned Life Insurance EffectiveIncomeTaxRateReconciliationNonTaxableEarningsOnCompanyOwnedLifeInsurance	-0.006
CY2020	fisi	Effective Income Tax Rate Reconciliation Non Taxable Earnings On Company Owned Life Insurance EffectiveIncomeTaxRateReconciliationNonTaxableEarningsOnCompanyOwnedLifeInsurance	-0.009
CY2019	fisi	Effective Income Tax Rate Reconciliation Non Taxable Earnings On Company Owned Life Insurance EffectiveIncomeTaxRateReconciliationNonTaxableEarningsOnCompanyOwnedLifeInsurance	-0.006
CY2021	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.030
CY2020	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.011
CY2019	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.019
CY2021	us-gaap	Effective Income Tax Rate Reconciliation Nondeductible Expense EffectiveIncomeTaxRateReconciliationNondeductibleExpense	0
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Nondeductible Expense EffectiveIncomeTaxRateReconciliationNondeductibleExpense	0.001
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Nondeductible Expense EffectiveIncomeTaxRateReconciliationNondeductibleExpense	0.002
CY2019	fisi	Effective Income Tax Rate Reconciliation Goodwill And Contingent Consideration Adjustments Percent EffectiveIncomeTaxRateReconciliationGoodwillAndContingentConsiderationAdjustmentsPercent	0
CY2021	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	0
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	0.003
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	0.002
CY2021	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.201
CY2020	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.162
CY2019	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.178
CY2021	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	19525000
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	7391000
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	10559000
CY2021	us-gaap	Income Tax Effects Allocated Directly To Equity IncomeTaxEffectsAllocatedDirectlyToEquity	-5282000
CY2020	us-gaap	Income Tax Effects Allocated Directly To Equity IncomeTaxEffectsAllocatedDirectlyToEquity	5732000
CY2019	us-gaap	Income Tax Effects Allocated Directly To Equity IncomeTaxEffectsAllocatedDirectlyToEquity	-3113000
CY2021Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Allowance For Doubtful Accounts DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAllowanceForDoubtfulAccounts	10627000
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Allowance For Doubtful Accounts DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAllowanceForDoubtfulAccounts	14239000
CY2021Q4	fisi	Deferred Tax Assets Leases Right Of Use Obligations DeferredTaxAssetsLeasesRightOfUseObligations	5993000
CY2020Q4	fisi	Deferred Tax Assets Leases Right Of Use Obligations DeferredTaxAssetsLeasesRightOfUseObligations	5510000
CY2021Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Employee Compensation DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeCompensation	1365000
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Employee Compensation DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeCompensation	1149000
CY2020Q4	us-gaap	Deferred Tax Assets Equity Method Investments DeferredTaxAssetsEquityMethodInvestments	1418000
CY2021Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Employee Benefits DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeBenefits	262000
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Employee Benefits DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeBenefits	323000
CY2021Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Share Based Compensation Cost DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost	759000
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Share Based Compensation Cost DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost	602000
CY2021Q4	us-gaap	Tax Credit Carryforward Amount TaxCreditCarryforwardAmount	446000
CY2020Q4	us-gaap	Tax Credit Carryforward Amount TaxCreditCarryforwardAmount	0
CY2021Q4	fisi	Net Unrealized Loss On Securities Available For Sale NetUnrealizedLossOnSecuritiesAvailableForSale	1712000
CY2020Q4	fisi	Net Unrealized Loss On Securities Available For Sale NetUnrealizedLossOnSecuritiesAvailableForSale	0
CY2021Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	579000
CY2020Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	236000
CY2021Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	21743000
CY2020Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	23477000
CY2021Q4	us-gaap	Deferred Tax Liabilities Leasing Arrangements DeferredTaxLiabilitiesLeasingArrangements	5533000
CY2020Q4	us-gaap	Deferred Tax Liabilities Leasing Arrangements DeferredTaxLiabilitiesLeasingArrangements	5113000
CY2021Q4	us-gaap	Minority Interest In Limited Partnerships MinorityInterestInLimitedPartnerships	126000
CY2020Q4	us-gaap	Minority Interest In Limited Partnerships MinorityInterestInLimitedPartnerships	0
CY2021Q4	us-gaap	Deferred Tax Liabilities Prepaid Expenses DeferredTaxLiabilitiesPrepaidExpenses	662000
CY2020Q4	us-gaap	Deferred Tax Liabilities Prepaid Expenses DeferredTaxLiabilitiesPrepaidExpenses	635000
CY2021Q4	fisi	Deferred Tax Liabilities Prepaid Pension Costs DeferredTaxLiabilitiesPrepaidPensionCosts	1677000
CY2020Q4	fisi	Deferred Tax Liabilities Prepaid Pension Costs DeferredTaxLiabilitiesPrepaidPensionCosts	1183000
CY2021Q4	us-gaap	Deferred Tax Liabilities Goodwill And Intangible Assets Intangible Assets DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsIntangibleAssets	2418000
CY2020Q4	us-gaap	Deferred Tax Liabilities Goodwill And Intangible Assets Intangible Assets DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsIntangibleAssets	2286000
CY2021Q4	fisi	Deferred Tax Liabilities Depreciation And Amortization DeferredTaxLiabilitiesDepreciationAndAmortization	3471000
CY2020Q4	fisi	Deferred Tax Liabilities Depreciation And Amortization DeferredTaxLiabilitiesDepreciationAndAmortization	2046000
CY2021Q4	fisi	Deferred Tax Liabilities Net Unrealized Gain On Securities Available For Sale DeferredTaxLiabilitiesNetUnrealizedGainOnSecuritiesAvailableForSale	0
CY2020Q4	fisi	Deferred Tax Liabilities Net Unrealized Gain On Securities Available For Sale DeferredTaxLiabilitiesNetUnrealizedGainOnSecuritiesAvailableForSale	5079000
CY2021Q4	us-gaap	Deferred Tax Liabilities Mortgage Servicing Rights DeferredTaxLiabilitiesMortgageServicingRights	389000
CY2020Q4	us-gaap	Deferred Tax Liabilities Mortgage Servicing Rights DeferredTaxLiabilitiesMortgageServicingRights	338000
CY2021Q4	fisi	Deferred Loan Origination Costs DeferredLoanOriginationCosts	830000
CY2020Q4	fisi	Deferred Loan Origination Costs DeferredLoanOriginationCosts	623000
CY2021Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	403000
CY2020Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	4000
CY2021Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	15509000
CY2020Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	17307000
CY2021Q4	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	6234000
CY2020Q4	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	6170000
CY2021Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	0
CY2020Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	0
CY2021Q4	us-gaap	Operating Loss Carryforwards OperatingLossCarryforwards	1700000
CY2019	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Expense UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense	0
CY2020	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
CY2021Q4	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Accrued UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued	0
CY2020Q4	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Accrued UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued	0
CY2021	us-gaap	Weighted Average Number Of Shares Issued Basic WeightedAverageNumberOfSharesIssuedBasic	16100000
CY2020	us-gaap	Weighted Average Number Of Shares Issued Basic WeightedAverageNumberOfSharesIssuedBasic	16100000
CY2019	us-gaap	Weighted Average Number Of Shares Issued Basic WeightedAverageNumberOfSharesIssuedBasic	16086000
CY2021	us-gaap	Weighted Average Number Of Shares Restricted Stock WeightedAverageNumberOfSharesRestrictedStock	5000
CY2020	us-gaap	Weighted Average Number Of Shares Restricted Stock WeightedAverageNumberOfSharesRestrictedStock	5000
CY2019	us-gaap	Weighted Average Number Of Shares Restricted Stock WeightedAverageNumberOfSharesRestrictedStock	4000
CY2021	us-gaap	Weighted Average Number Of Shares Treasury Stock WeightedAverageNumberOfSharesTreasuryStock	254000
CY2020	us-gaap	Weighted Average Number Of Shares Treasury Stock WeightedAverageNumberOfSharesTreasuryStock	73000
CY2021	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	76237000
CY2020	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	36871000
CY2019	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	47401000
CY2019	us-gaap	Weighted Average Number Of Shares Treasury Stock WeightedAverageNumberOfSharesTreasuryStock	110000
CY2021	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	15841000
CY2020	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	16022000
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	15972000
CY2021	fisi	Incremental Common Shares Attributable To Vesting Of Restricted Stock Awards IncrementalCommonSharesAttributableToVestingOfRestrictedStockAwards	96000
CY2020	fisi	Incremental Common Shares Attributable To Vesting Of Restricted Stock Awards IncrementalCommonSharesAttributableToVestingOfRestrictedStockAwards	41000
CY2019	fisi	Incremental Common Shares Attributable To Vesting Of Restricted Stock Awards IncrementalCommonSharesAttributableToVestingOfRestrictedStockAwards	59000
CY2021	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	15937000
CY2020	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	16063000
CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	16031000
CY2021	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	4.81
CY2020	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.30
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.97
CY2021	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	4.78
CY2020	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.30
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.96
CY2021	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	3000
CY2020	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	54000
CY2019	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	4000
CY2021	us-gaap	Incremental Common Shares Attributable To Participating Nonvested Shares With Non Forfeitable Dividend Rights IncrementalCommonSharesAttributableToParticipatingNonvestedSharesWithNonForfeitableDividendRights	0
CY2020	us-gaap	Incremental Common Shares Attributable To Participating Nonvested Shares With Non Forfeitable Dividend Rights IncrementalCommonSharesAttributableToParticipatingNonvestedSharesWithNonForfeitableDividendRights	0
CY2019	us-gaap	Incremental Common Shares Attributable To Participating Nonvested Shares With Non Forfeitable Dividend Rights IncrementalCommonSharesAttributableToParticipatingNonvestedSharesWithNonForfeitableDividendRights	0
CY2021Q4	us-gaap	Defined Benefit Plan Pension Plans With Accumulated Benefit Obligations In Excess Of Plan Assets Aggregate Projected Benefit Obligation DefinedBenefitPlanPensionPlansWithAccumulatedBenefitObligationsInExcessOfPlanAssetsAggregateProjectedBenefitObligation	0
CY2020Q4	us-gaap	Defined Benefit Plan Pension Plans With Accumulated Benefit Obligations In Excess Of Plan Assets Aggregate Projected Benefit Obligation DefinedBenefitPlanPensionPlansWithAccumulatedBenefitObligationsInExcessOfPlanAssetsAggregateProjectedBenefitObligation	0
CY2019Q4	us-gaap	Defined Benefit Plan Pension Plans With Accumulated Benefit Obligations In Excess Of Plan Assets Aggregate Projected Benefit Obligation DefinedBenefitPlanPensionPlansWithAccumulatedBenefitObligationsInExcessOfPlanAssetsAggregateProjectedBenefitObligation	0
CY2020Q4	us-gaap	Defined Benefit Plan Benefit Obligation DefinedBenefitPlanBenefitObligation	97560000
CY2019Q4	us-gaap	Defined Benefit Plan Benefit Obligation DefinedBenefitPlanBenefitObligation	84328000
CY2021	us-gaap	Defined Benefit Plan Service Cost DefinedBenefitPlanServiceCost	4196000
CY2020	us-gaap	Defined Benefit Plan Service Cost DefinedBenefitPlanServiceCost	3693000
CY2021	us-gaap	Defined Benefit Plan Interest Cost DefinedBenefitPlanInterestCost	2202000
CY2020	us-gaap	Defined Benefit Plan Interest Cost DefinedBenefitPlanInterestCost	2537000
CY2021	us-gaap	Defined Benefit Plan Actuarial Gain Loss DefinedBenefitPlanActuarialGainLoss	1945000
CY2020	us-gaap	Defined Benefit Plan Actuarial Gain Loss DefinedBenefitPlanActuarialGainLoss	-11154000
CY2021	us-gaap	Defined Benefit Plan Benefit Obligation Benefits Paid DefinedBenefitPlanBenefitObligationBenefitsPaid	4331000
CY2020	us-gaap	Defined Benefit Plan Benefit Obligation Benefits Paid DefinedBenefitPlanBenefitObligationBenefitsPaid	4152000
CY2021Q4	us-gaap	Defined Benefit Plan Benefit Obligation DefinedBenefitPlanBenefitObligation	97682000
CY2020Q4	us-gaap	Defined Benefit Plan Benefit Obligation DefinedBenefitPlanBenefitObligation	97560000
CY2021	us-gaap	Defined Benefit Plan Actual Return On Plan Assets DefinedBenefitPlanActualReturnOnPlanAssets	6382000
CY2020	us-gaap	Defined Benefit Plan Actual Return On Plan Assets DefinedBenefitPlanActualReturnOnPlanAssets	18501000
CY2021	us-gaap	Defined Benefit Plan Plan Assets Benefits Paid DefinedBenefitPlanPlanAssetsBenefitsPaid	4331000
CY2020	us-gaap	Defined Benefit Plan Plan Assets Benefits Paid DefinedBenefitPlanPlanAssetsBenefitsPaid	4152000
CY2021Q4	us-gaap	Defined Benefit Plan Fair Value Of Plan Assets DefinedBenefitPlanFairValueOfPlanAssets	104227000
CY2020Q4	us-gaap	Defined Benefit Plan Fair Value Of Plan Assets DefinedBenefitPlanFairValueOfPlanAssets	102176000
CY2021Q4	us-gaap	Defined Benefit Plan Funded Status Of Plan DefinedBenefitPlanFundedStatusOfPlan	6545000
CY2020Q4	us-gaap	Defined Benefit Plan Funded Status Of Plan DefinedBenefitPlanFundedStatusOfPlan	4616000
CY2021Q4	us-gaap	Defined Benefit Plan Accumulated Benefit Obligation DefinedBenefitPlanAccumulatedBenefitObligation	90100000
CY2020Q4	us-gaap	Defined Benefit Plan Accumulated Benefit Obligation DefinedBenefitPlanAccumulatedBenefitObligation	88900000
CY2021Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Next Twelve Months DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths	3731000
CY2021Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Year Two DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo	3935000
CY2021Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Year Three DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree	4199000
CY2021Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Year Four DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour	4425000
CY2021Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Year Five DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive	4663000
CY2021Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Five Fiscal Years Thereafter DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter	25686000
CY2021	us-gaap	Defined Benefit Plan Service Cost DefinedBenefitPlanServiceCost	4196000
CY2020	us-gaap	Defined Benefit Plan Service Cost DefinedBenefitPlanServiceCost	3693000
CY2019	us-gaap	Defined Benefit Plan Service Cost DefinedBenefitPlanServiceCost	3207000
CY2021	us-gaap	Defined Benefit Plan Interest Cost DefinedBenefitPlanInterestCost	2202000
CY2020	us-gaap	Defined Benefit Plan Interest Cost DefinedBenefitPlanInterestCost	2537000
CY2019	us-gaap	Defined Benefit Plan Interest Cost DefinedBenefitPlanInterestCost	2777000
CY2021	us-gaap	Defined Benefit Plan Expected Return On Plan Assets DefinedBenefitPlanExpectedReturnOnPlanAssets	5225000
CY2020	us-gaap	Defined Benefit Plan Expected Return On Plan Assets DefinedBenefitPlanExpectedReturnOnPlanAssets	5136000
CY2019	us-gaap	Defined Benefit Plan Expected Return On Plan Assets DefinedBenefitPlanExpectedReturnOnPlanAssets	4736000
CY2021	us-gaap	Defined Benefit Plan Amortization Of Gains Losses DefinedBenefitPlanAmortizationOfGainsLosses	-724000
CY2020	us-gaap	Defined Benefit Plan Amortization Of Gains Losses DefinedBenefitPlanAmortizationOfGainsLosses	-1270000
CY2019	us-gaap	Defined Benefit Plan Amortization Of Gains Losses DefinedBenefitPlanAmortizationOfGainsLosses	-1445000
CY2021	us-gaap	Defined Benefit Plan Net Periodic Benefit Cost DefinedBenefitPlanNetPeriodicBenefitCost	1897000
CY2020	us-gaap	Defined Benefit Plan Net Periodic Benefit Cost DefinedBenefitPlanNetPeriodicBenefitCost	2364000
CY2019	us-gaap	Defined Benefit Plan Net Periodic Benefit Cost DefinedBenefitPlanNetPeriodicBenefitCost	2693000
CY2021	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Discount Rate DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate	0.0232
CY2020	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Discount Rate DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate	0.0309
CY2019	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Discount Rate DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate	0.0413
CY2021	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Rate Of Compensation Increase DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease	0.0300
CY2020	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Rate Of Compensation Increase DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease	0.0300
CY2019	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Rate Of Compensation Increase DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease	0.0300
CY2021	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Expected Long Term Return On Assets DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets	0.0525
CY2020	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Expected Long Term Return On Assets DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets	0.0600
CY2019	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Expected Long Term Return On Assets DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets	0.0650
CY2021Q4	us-gaap	Defined Benefit Plan Assumptions Used Calculating Benefit Obligation Discount Rate DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate	0.0270
CY2020Q4	us-gaap	Defined Benefit Plan Assumptions Used Calculating Benefit Obligation Discount Rate DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate	0.0232
CY2019Q4	us-gaap	Defined Benefit Plan Assumptions Used Calculating Benefit Obligation Discount Rate DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate	0.0309
CY2021Q4	us-gaap	Defined Benefit Plan Assumptions Used Calculating Benefit Obligation Rate Of Compensation Increase DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease	0.0300
CY2020Q4	us-gaap	Defined Benefit Plan Assumptions Used Calculating Benefit Obligation Rate Of Compensation Increase DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease	0.0300
CY2019Q4	us-gaap	Defined Benefit Plan Assumptions Used Calculating Benefit Obligation Rate Of Compensation Increase DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease	0.0300
CY2021	fisi	Investment Strategy Percentage In Long Term Growth InvestmentStrategyPercentageInLongTermGrowth	0.97
CY2021	fisi	Investment Strategy Percentage In Near Term Benefit Payments InvestmentStrategyPercentageInNearTermBenefitPayments	0.03
CY2021Q4	us-gaap	Cash Equivalents At Carrying Value CashEquivalentsAtCarryingValue	0
CY2021Q4	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	37157000
CY2021Q4	fisi	Fixed Income Securities FixedIncomeSecurities	36459000
CY2021Q4	us-gaap	Investments And Cash InvestmentsAndCash	104227000
CY2021Q4	us-gaap	Defined Benefit Plan Weighted Average Asset Allocations DefinedBenefitPlanWeightedAverageAssetAllocations	1
CY2020Q4	us-gaap	Cash Equivalents At Carrying Value CashEquivalentsAtCarryingValue	1259000
CY2020Q4	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	31848000
CY2020Q4	fisi	Fixed Income Securities FixedIncomeSecurities	63176000
CY2020Q4	us-gaap	Investments And Cash InvestmentsAndCash	102176000
CY2020Q4	us-gaap	Defined Benefit Plan Weighted Average Asset Allocations DefinedBenefitPlanWeightedAverageAssetAllocations	0.99
CY2021Q4	us-gaap	Pension And Other Postretirement And Postemployment Benefit Plans Liabilities Current And Noncurrent PensionAndOtherPostretirementAndPostemploymentBenefitPlansLiabilitiesCurrentAndNoncurrent	33000
CY2020Q4	us-gaap	Pension And Other Postretirement And Postemployment Benefit Plans Liabilities Current And Noncurrent PensionAndOtherPostretirementAndPostemploymentBenefitPlansLiabilitiesCurrentAndNoncurrent	108000
CY2021Q4	us-gaap	Defined Benefit Plan Accumulated Other Comprehensive Income Before Tax DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTax	12633000
CY2020Q4	us-gaap	Defined Benefit Plan Accumulated Other Comprehensive Income Before Tax DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTax	16536000
CY2021	us-gaap	Other Comprehensive Income Defined Benefit Plans Tax Portion Attributable To Parent OtherComprehensiveIncomeDefinedBenefitPlansTaxPortionAttributableToParent	3237000
CY2020	us-gaap	Other Comprehensive Income Defined Benefit Plans Tax Portion Attributable To Parent OtherComprehensiveIncomeDefinedBenefitPlansTaxPortionAttributableToParent	4237000
CY2021Q4	us-gaap	Accumulated Other Comprehensive Income Loss Defined Benefit Pension And Other Postretirement Plans Net Of Tax AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax	9396000
CY2020Q4	us-gaap	Accumulated Other Comprehensive Income Loss Defined Benefit Pension And Other Postretirement Plans Net Of Tax AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax	12299000
CY2021	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax	-3903000
CY2020	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax	-3454000
CY2021Q4	us-gaap	Fair Value Assets Level1 To Level2 Transfers Amount FairValueAssetsLevel1ToLevel2TransfersAmount	0
CY2020Q4	us-gaap	Fair Value Assets Level1 To Level2 Transfers Amount FairValueAssetsLevel1ToLevel2TransfersAmount	0
CY2019Q4	us-gaap	Fair Value Assets Level1 To Level2 Transfers Amount FairValueAssetsLevel1ToLevel2TransfersAmount	0
CY2020Q4	us-gaap	Fair Value Assets Level1 To Level2 Transfers Amount FairValueAssetsLevel1ToLevel2TransfersAmount	0
CY2021Q4	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Value FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue	0
CY2020Q4	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Value FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue	0
CY2021	us-gaap	Number Of Reportable Segments NumberOfReportableSegments	1
CY2021Q4	us-gaap	Goodwill Goodwill	67071000
CY2021Q4	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	7329000
CY2021Q4	us-gaap	Assets Assets	5520779000
CY2020Q4	us-gaap	Goodwill Goodwill	66062000
CY2020Q4	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	7727000
CY2020Q4	us-gaap	Assets Assets	4912306000
CY2021	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	154730000
CY2021	fisi	Provision For Credit Losses ProvisionForCreditLosses	-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
CY2020	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	138985000
CY2020	fisi	Provision For Credit Losses ProvisionForCreditLosses	27184000
CY2020	us-gaap	Noninterest Income NoninterestIncome	43176000
CY2020	us-gaap	Noninterest Expense NoninterestExpense	109254000
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	45723000
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	7391000
CY2020	us-gaap	Net Income Loss NetIncomeLoss	38332000
CY2019	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	129912000
CY2019	fisi	Provision For Credit Losses ProvisionForCreditLosses	8044000
CY2019	us-gaap	Noninterest Income NoninterestIncome	40381000
CY2019	us-gaap	Noninterest Expense NoninterestExpense	102828000
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	59421000
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	10559000
CY2019	us-gaap	Net Income Loss NetIncomeLoss	48862000

Files In Submission

Name	View Source	Status
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0000950170-22-003353-index.html	Edgar Link	pending
0000950170-22-003353.txt	Edgar Link	pending
0000950170-22-003353-xbrl.zip	Edgar Link	pending
FilingSummary.xml	Edgar Link	unprocessable
Financial_Report.xlsx	Edgar Link	pending
fisi-20211231.htm	Edgar Link	pending
fisi-20211231.xsd	Edgar Link	pending
fisi-20211231_cal.xml	Edgar Link	unprocessable
fisi-20211231_def.xml	Edgar Link	unprocessable
fisi-20211231_htm.xml	Edgar Link	completed
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$FISI
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2021 Form 10-K Financial Statement

#000095017022003353 Filed on March 10, 2022

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$FISI FINANCIAL INSTITUTIONS INC Stock $fisi

2021 Form 10-K Financial Statement

#000095017022003353 Filed on March 10, 2022

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$FISI
FINANCIAL INSTITUTIONS INC Stock $fisi