$CHMG
Chemung Financial Corp Stock $chmg

$chmg Overview Financials Valuation SEC Filings Company Website

2019 Q4 Form 10-K Financial Statement

#000076356321000045 Filed on March 24, 2021

Income Statement

Concept	2019 Q4	2019	2018 Q4
Revenue		$66.93M
YoY Change		3.69%
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	$870.0K	$3.100M	$980.0K
YoY Change	-11.22%	-8.82%	-10.09%
% of Gross Profit
Operating Expenses
YoY Change
Operating Profit
YoY Change
Interest Expense		$6.321M
YoY Change		55.19%
% of Operating Profit
Other Income/Expense, Net		$55.70M
YoY Change		-1.88%
Pretax Income	$5.200M	$19.04M	$6.390M
YoY Change	-18.62%	-19.43%	651.76%
Income Tax	$990.0K	$3.434M	$1.110M
% Of Pretax Income	19.04%	18.03%	17.37%
Net Earnings	$4.200M	$15.61M	$5.730M
YoY Change	-26.7%	-20.47%	-365.28%
Net Earnings / Revenue		23.32%
Basic Earnings Per Share
Diluted Earnings Per Share	$860.7K	$3.205M	$1.184M
COMMON SHARES
Basic Shares Outstanding	4.847M shares		4.807M shares
Diluted Shares Outstanding

Balance Sheet

Concept	2019 Q4	2019	2018 Q4
SHORT-TERM ASSETS
Cash & Short-Term Investments
YoY Change
Cash & Equivalents	$121.9M		$130.0M
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	$22.42M	$30.40M	$24.98M
YoY Change	-10.26%	21.6%	-6.29%
Goodwill	$21.82M		$21.82M
YoY Change	0.0%		0.0%
Intangibles	$742.0K		$1.351M
YoY Change	-45.08%		-35.2%
Long-Term Investments	$2.200M	$2.500M	$1.900M
YoY Change	15.79%	8.7%	-36.67%
Other Assets
YoY Change
Total Long-Term Assets
YoY Change
TOTAL ASSETS
Total Short-Term Assets
Total Long-Term Assets
Total Assets	$1.788B	$1.788B	$1.755B
YoY Change	1.85%	1.85%	2.79%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable	$19.60M	$19.60M	$15.50M
YoY Change	26.45%	26.45%	4.03%
Accrued Expenses	$8.100M	$8.100M
YoY Change
Deferred Revenue
YoY Change
Short-Term Debt			$0.00
YoY Change			-100.0%
Long-Term Debt Due
YoY Change
Total Short-Term Liabilities	$29.00M	$29.00M	$16.80M
YoY Change	72.62%	72.62%	4.35%
LONG-TERM LIABILITIES
Long-Term Debt	$4.100M	$4.100M	$4.300M
YoY Change	-4.65%	-4.65%	-4.44%
Other Long-Term Liabilities
YoY Change
Total Long-Term Liabilities	$4.100M	$4.100M	$4.300M
YoY Change	-4.65%	-4.65%	-4.44%
TOTAL LIABILITIES
Total Short-Term Liabilities	$29.00M	$29.00M	$16.80M
Total Long-Term Liabilities	$4.100M	$4.100M	$4.300M
Total Liabilities	$1.605B	$1.605B	$1.590B
YoY Change	0.94%	0.94%	2.09%
SHAREHOLDERS EQUITY
Retained Earnings	$153.7M		$143.1M
YoY Change	7.39%		11.43%
Common Stock	$46.44M		$45.87M
YoY Change	1.23%		-0.32%
Preferred Stock
YoY Change
Treasury Stock (at cost)	$11.71M		$12.56M
YoY Change	-6.78%		-12.28%
Treasury Stock Shares	452.6K shares		488.8K shares
Shareholders Equity	$182.6M	$182.6M	$165.0M
YoY Change
Total Liabilities & Shareholders Equity	$1.788B	$1.788B	$1.755B
YoY Change	1.85%	1.85%	2.79%

Cashflow Statement

Concept	2019 Q4	2019	2018 Q4
OPERATING ACTIVITIES
Net Income	$4.200M	$15.61M	$5.730M
YoY Change	-26.7%	-20.47%	-365.28%
Depreciation, Depletion And Amortization	$870.0K	$3.100M	$980.0K
YoY Change	-11.22%	-8.82%	-10.09%
Cash From Operating Activities	$4.600M	$26.41M	$7.660M
YoY Change	-39.95%	-4.92%	8.5%
INVESTING ACTIVITIES
Capital Expenditures	-$490.0K	$883.0K	-$280.0K
YoY Change	75.0%	-50.11%	47.37%
Acquisitions
YoY Change
Other Investing Activities	-$22.95M	-$31.83M	$16.56M
YoY Change	-238.59%	-169.67%	-232.48%
Cash From Investing Activities	-$23.44M	-$32.71M	$16.28M
YoY Change	-243.98%	-174.48%	-228.29%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net		$0.00
YoY Change
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	-5.550M	-$1.762M	-7.890M
YoY Change	-29.66%	-106.4%	-60.61%
NET CHANGE
Cash From Operating Activities	4.600M	$26.41M	7.660M
Cash From Investing Activities	-23.44M	-$32.71M	16.28M
Cash From Financing Activities	-5.550M	-$1.762M	-7.890M
Net Change In Cash	-24.39M	-$8.068M	16.05M
YoY Change	-251.96%	-108.13%	-162.55%
FREE CASH FLOW
Cash From Operating Activities	$4.600M	$26.41M	$7.660M
Capital Expenditures	-$490.0K	$883.0K	-$280.0K
Free Cash Flow	$5.090M	$25.52M	$7.940M
YoY Change	-35.89%	-1.85%	9.52%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
CY2020	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-31
CY2020	dei	Document Transition Report DocumentTransitionReport	false
CY2020	dei	Entity File Number EntityFileNumber	0-13888
CY2020	dei	Entity Central Index Key EntityCentralIndexKey	0000763563
CY2020	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2020
CY2020	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	FY
CY2020	dei	Amendment Flag AmendmentFlag	false
CY2020	dei	Document Type DocumentType	10-K
CY2020	dei	Document Annual Report DocumentAnnualReport	true
CY2020	dei	Document Period End Date DocumentPeriodEndDate	2020-12-31
CY2020	dei	Entity Registrant Name EntityRegistrantName	CHEMUNG FINANCIAL CORP
CY2020	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	NY
CY2020	dei	Entity Shell Company EntityShellCompany	false
CY2020	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	16-1237038
CY2021Q1	dei	Entity Common Stock Shares Outstanding EntityCommonStockSharesOutstanding	4661598	shares
CY2020Q4	us-gaap	Common Stock Value CommonStockValue	53000	USD
CY2020	dei	Entity Address Address Line1 EntityAddressAddressLine1	One Chemung Canal Plaza
CY2020	dei	Entity Address City Or Town EntityAddressCityOrTown	Elmira
CY2020	dei	Entity Address State Or Province EntityAddressStateOrProvince	NY
CY2020	dei	Entity Address Postal Zip Code EntityAddressPostalZipCode	14901
CY2020	dei	City Area Code CityAreaCode	607
CY2020	dei	Local Phone Number LocalPhoneNumber	737-3711
CY2020	dei	Security12b Title Security12bTitle	Common Stock, Par Value $0.01 Per Share
CY2020	dei	Trading Symbol TradingSymbol	CHMG
CY2020	dei	Security Exchange Name SecurityExchangeName	NASDAQ
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CY2020	dei	Entity Voluntary Filers EntityVoluntaryFilers	No
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CY2019	us-gaap	Foreclosed Real Estate Expense ForeclosedRealEstateExpense	115000	USD
CY2018	us-gaap	Foreclosed Real Estate Expense ForeclosedRealEstateExpense	422000	USD
CY2020	us-gaap	Federal Deposit Insurance Corporation Premium Expense FederalDepositInsuranceCorporationPremiumExpense	987000	USD
CY2019	us-gaap	Federal Deposit Insurance Corporation Premium Expense FederalDepositInsuranceCorporationPremiumExpense	537000	USD
CY2020	us-gaap	Loan Portfolio Expense LoanPortfolioExpense	1173000	USD
CY2019	us-gaap	Loan Portfolio Expense LoanPortfolioExpense	787000	USD
CY2018	us-gaap	Loan Portfolio Expense LoanPortfolioExpense	863000	USD
CY2020	us-gaap	Other Noninterest Expense OtherNoninterestExpense	6508000	USD
CY2019	us-gaap	Other Noninterest Expense OtherNoninterestExpense	6198000	USD
CY2018	us-gaap	Other Noninterest Expense OtherNoninterestExpense	6093000	USD
CY2020	us-gaap	Noninterest Expense NoninterestExpense	55935000	USD
CY2019	us-gaap	Noninterest Expense NoninterestExpense	55696000	USD
CY2018	us-gaap	Noninterest Expense NoninterestExpense	56766000	USD
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	23869000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	19043000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	23635000	USD
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	4607000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	3434000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	4009000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	19262000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	15609000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	19626000	USD
CY2020	us-gaap	Weighted Average Number Of Share Outstanding Basic And Diluted WeightedAverageNumberOfShareOutstandingBasicAndDiluted	4802000	shares
CY2019	us-gaap	Weighted Average Number Of Share Outstanding Basic And Diluted WeightedAverageNumberOfShareOutstandingBasicAndDiluted	4869000	shares
CY2018	us-gaap	Weighted Average Number Of Share Outstanding Basic And Diluted WeightedAverageNumberOfShareOutstandingBasicAndDiluted	4832000	shares
CY2020	us-gaap	Earnings Per Share Basic And Diluted EarningsPerShareBasicAndDiluted	4.01
CY2019	us-gaap	Earnings Per Share Basic And Diluted EarningsPerShareBasicAndDiluted	3.21
CY2018	us-gaap	Earnings Per Share Basic And Diluted EarningsPerShareBasicAndDiluted	4.06
CY2020	us-gaap	Net Income Loss NetIncomeLoss	19262000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	19262000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	15609000	USD
CY2020	us-gaap	Other Comprehensive Income Availableforsale Securities Tax Portion Attributable To Parent OtherComprehensiveIncomeAvailableforsaleSecuritiesTaxPortionAttributableToParent	2656000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	19626000	USD
CY2020	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	10415000	USD
CY2019	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	8053000	USD
CY2018	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	-1382000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	0	USD
CY2019	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	-19000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	0	USD
CY2020	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Before Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax	10415000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Before Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax	8072000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Before Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax	-1382000	USD
CY2019	us-gaap	Other Comprehensive Income Availableforsale Securities Tax Portion Attributable To Parent OtherComprehensiveIncomeAvailableforsaleSecuritiesTaxPortionAttributableToParent	2058000	USD
CY2018	us-gaap	Other Comprehensive Income Availableforsale Securities Tax Portion Attributable To Parent OtherComprehensiveIncomeAvailableforsaleSecuritiesTaxPortionAttributableToParent	-353000	USD
CY2020	us-gaap	Other Comprehensive Income Availableforsale Securities Adjustment Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentNetOfTaxPortionAttributableToParent	7759000	USD
CY2019	us-gaap	Other Comprehensive Income Availableforsale Securities Adjustment Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentNetOfTaxPortionAttributableToParent	6014000	USD
CY2018	us-gaap	Other Comprehensive Income Availableforsale Securities Adjustment Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentNetOfTaxPortionAttributableToParent	-1029000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Net Unamortized Gain Loss Arising During Period Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax	506000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Net Unamortized Gain Loss Arising During Period Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax	-626000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Net Unamortized Gain Loss Arising During Period Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax	-711000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Amortization Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Prior Service Cost Credit Before Tax OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax	-220000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Amortization Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Prior Service Cost Credit Before Tax OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax	-220000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Amortization Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Prior Service Cost Credit Before Tax OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax	-220000	USD
CY2020	us-gaap	Other Comprehensive Income Defined Benefit Plan Net Prior Service Cost Credit Arising During Period Before Tax OtherComprehensiveIncomeDefinedBenefitPlanNetPriorServiceCostCreditArisingDuringPeriodBeforeTax	0	USD
CY2019	us-gaap	Other Comprehensive Income Defined Benefit Plan Net Prior Service Cost Credit Arising During Period Before Tax OtherComprehensiveIncomeDefinedBenefitPlanNetPriorServiceCostCreditArisingDuringPeriodBeforeTax	0	USD
CY2018	us-gaap	Other Comprehensive Income Defined Benefit Plan Net Prior Service Cost Credit Arising During Period Before Tax OtherComprehensiveIncomeDefinedBenefitPlanNetPriorServiceCostCreditArisingDuringPeriodBeforeTax	0	USD
CY2020	us-gaap	Other Comprehensive Income Loss Finalization Of Pension And Non Pension Postretirement Plan Valuation Before Tax OtherComprehensiveIncomeLossFinalizationOfPensionAndNonPensionPostretirementPlanValuationBeforeTax	0	USD
CY2019	us-gaap	Other Comprehensive Income Loss Finalization Of Pension And Non Pension Postretirement Plan Valuation Before Tax OtherComprehensiveIncomeLossFinalizationOfPensionAndNonPensionPostretirementPlanValuationBeforeTax	0	USD
CY2018	us-gaap	Other Comprehensive Income Loss Finalization Of Pension And Non Pension Postretirement Plan Valuation Before Tax OtherComprehensiveIncomeLossFinalizationOfPensionAndNonPensionPostretirementPlanValuationBeforeTax	828000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax	-300000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax	-312000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax	-318000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax	-586000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax	534000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax	-215000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	-145000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	132000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	-55000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-441000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	402000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-160000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	8200000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	5612000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-869000	USD
CY2020	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	27462000	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	21221000	USD
CY2018	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	18757000	USD
CY2017Q4	us-gaap	Stockholders Equity StockholdersEquity	149813000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	19626000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-869000	USD
CY2018	us-gaap	Adjustments To Additional Paid In Capital Share Based Compensation Restricted Stock Units Requisite Service Period Recognition AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationRestrictedStockUnitsRequisiteServicePeriodRecognition	405000	USD
CY2018	chmg	Distribution Of Shares Of Treasury Stock For Directors Deferred Compensation Shares DistributionOfSharesOfTreasuryStockForDirectorsDeferredCompensationShares	36681	shares
CY2018	chmg	Distribution Of Shares Of Treasury Stock For Directors Deferred Compensation Value DistributionOfSharesOfTreasuryStockForDirectorsDeferredCompensationValue	218000	USD
CY2018	chmg	Distribution Of Treasury Stock For Employee Restricted Stock Awards Shares DistributionOfTreasuryStockForEmployeeRestrictedStockAwardsShares	14425	shares
CY2018	chmg	Distribution Share Of Treasury Stock For Employee Restricted Stock Warrants DistributionShareOfTreasuryStockForEmployeeRestrictedStockWarrants	0	USD
CY2018	chmg	Restricted Stock Units For Directors Deferred Compensation Plan RestrictedStockUnitsForDirectorsDeferredCompensationPlan	67000	USD
CY2018	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.04
CY2018	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	4990000	USD
CY2018	chmg	Distribution Of Shares Of Treasury Stock For Directors Compensation Shares DistributionOfSharesOfTreasuryStockForDirectorsCompensationShares	6015	shares
CY2018	chmg	Distribution Of Shares Of Treasury Stock For Directors Compensation Value DistributionOfSharesOfTreasuryStockForDirectorsCompensationValue	301000	USD
CY2018	us-gaap	Stock Issued During Period Shares Share Based Compensation StockIssuedDuringPeriodSharesShareBasedCompensation	1784	shares
CY2018	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	89000	USD
CY2018	us-gaap	Stock Issued During Period Shares Treasury Stock Reissued StockIssuedDuringPeriodSharesTreasuryStockReissued	14081	shares
CY2018	us-gaap	Stock Issued During Period Value Treasury Stock Reissued StockIssuedDuringPeriodValueTreasuryStockReissued	643000	USD
CY2018	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	2736	shares
CY2018	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	112000	USD
CY2018Q4	us-gaap	Stockholders Equity StockholdersEquity	165029000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	15609000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	5612000	USD
CY2019	us-gaap	Adjustments To Additional Paid In Capital Share Based Compensation Restricted Stock Units Requisite Service Period Recognition AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationRestrictedStockUnitsRequisiteServicePeriodRecognition	503000	USD
CY2019	chmg	Distribution Of Shares Of Treasury Stock For Directors Deferred Compensation Shares DistributionOfSharesOfTreasuryStockForDirectorsDeferredCompensationShares	2551	shares
CY2019	chmg	Distribution Of Shares Of Treasury Stock For Directors Deferred Compensation Value DistributionOfSharesOfTreasuryStockForDirectorsDeferredCompensationValue	13000	USD
CY2019	chmg	Distribution Of Treasury Stock For Employee Restricted Stock Awards Shares DistributionOfTreasuryStockForEmployeeRestrictedStockAwardsShares	13692	shares
CY2019	chmg	Distribution Share Of Treasury Stock For Employee Restricted Stock Warrants DistributionShareOfTreasuryStockForEmployeeRestrictedStockWarrants	0	USD
CY2019	chmg	Restricted Stock Units For Directors Deferred Compensation Plan RestrictedStockUnitsForDirectorsDeferredCompensationPlan	42000	USD
CY2019	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.04
CY2019	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	5037000	USD
CY2019	chmg	Distribution Of Shares Of Treasury Stock For Directors Compensation Shares DistributionOfSharesOfTreasuryStockForDirectorsCompensationShares	8465	shares
CY2019	chmg	Distribution Of Shares Of Treasury Stock For Directors Compensation Value DistributionOfSharesOfTreasuryStockForDirectorsCompensationValue	356000	USD
CY2019	us-gaap	Stock Issued During Period Shares Share Based Compensation StockIssuedDuringPeriodSharesShareBasedCompensation	2373	shares
CY2019	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	100000	USD
CY2019	us-gaap	Stock Issued During Period Shares Treasury Stock Reissued StockIssuedDuringPeriodSharesTreasuryStockReissued	13270	shares
CY2019	us-gaap	Stock Issued During Period Value Treasury Stock Reissued StockIssuedDuringPeriodValueTreasuryStockReissued	585000	USD
CY2019	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	4148	shares
CY2019	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	185000	USD
CY2019Q4	us-gaap	Stockholders Equity StockholdersEquity	182627000	USD
CY2019Q4	us-gaap	Stockholders Equity StockholdersEquity	182627000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	19262000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	8200000	USD
CY2020	us-gaap	Adjustments To Additional Paid In Capital Share Based Compensation Restricted Stock Units Requisite Service Period Recognition AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationRestrictedStockUnitsRequisiteServicePeriodRecognition	672000	USD
CY2020	chmg	Distribution Of Shares Of Treasury Stock For Directors Deferred Compensation Shares DistributionOfSharesOfTreasuryStockForDirectorsDeferredCompensationShares	6426	shares
CY2020	chmg	Distribution Of Shares Of Treasury Stock For Directors Deferred Compensation Value DistributionOfSharesOfTreasuryStockForDirectorsDeferredCompensationValue	-14000	USD
CY2020	chmg	Distribution Of Treasury Stock For Employee Restricted Stock Awards Shares DistributionOfTreasuryStockForEmployeeRestrictedStockAwardsShares	14805	shares
CY2020	chmg	Distribution Share Of Treasury Stock For Employee Restricted Stock Warrants DistributionShareOfTreasuryStockForEmployeeRestrictedStockWarrants	0	USD
CY2020	chmg	Restricted Stock Units For Directors Deferred Compensation Plan RestrictedStockUnitsForDirectorsDeferredCompensationPlan	29000	USD
CY2020	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.04
CY2020	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	4957000	USD
CY2020	chmg	Distribution Of Shares Of Treasury Stock For Directors Compensation Shares DistributionOfSharesOfTreasuryStockForDirectorsCompensationShares	7923	shares
CY2020	chmg	Distribution Of Shares Of Treasury Stock For Directors Compensation Value DistributionOfSharesOfTreasuryStockForDirectorsCompensationValue	350000	USD
CY2020	us-gaap	Stock Issued During Period Shares Share Based Compensation StockIssuedDuringPeriodSharesShareBasedCompensation	2274	shares
CY2020	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	101000	USD
CY2020	us-gaap	Stock Issued During Period Shares Treasury Stock Reissued StockIssuedDuringPeriodSharesTreasuryStockReissued	36104	shares
CY2020	us-gaap	Stock Issued During Period Value Treasury Stock Reissued StockIssuedDuringPeriodValueTreasuryStockReissued	1018000	USD
CY2020	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	257018	shares
CY2020	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	7589000	USD
CY2020	us-gaap	Stock Issued During Period Shares Restricted Stock Award Forfeited StockIssuedDuringPeriodSharesRestrictedStockAwardForfeited	112	shares
CY2020	us-gaap	Stock Issued During Period Value Restricted Stock Award Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardForfeitures	0	USD
CY2020Q4	us-gaap	Stockholders Equity StockholdersEquity	199699000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	19262000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	15609000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	19626000	USD
CY2020	chmg	Operating Lease Right Of Use Asset Amortization OperatingLeaseRightOfUseAssetAmortization	856000	USD
CY2019	chmg	Operating Lease Right Of Use Asset Amortization OperatingLeaseRightOfUseAssetAmortization	712000	USD
CY2018	chmg	Operating Lease Right Of Use Asset Amortization OperatingLeaseRightOfUseAssetAmortization	0	USD
CY2020	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	484000	USD
CY2019	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	609000	USD
CY2018	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	734000	USD
CY2020	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-86000	USD
CY2019	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-1564000	USD
CY2018	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	2153000	USD
CY2020	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	4239000	USD
CY2019	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	5945000	USD
CY2018	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	3153000	USD
CY2020	us-gaap	Gain Loss On Disposition Of Assets GainLossOnDispositionOfAssets	-247000	USD
CY2019	us-gaap	Gain Loss On Disposition Of Assets GainLossOnDispositionOfAssets	-334000	USD
CY2018	us-gaap	Gain Loss On Disposition Of Assets GainLossOnDispositionOfAssets	-10000	USD
CY2020	us-gaap	Depreciation Depreciation	2918000	USD
CY2019	us-gaap	Depreciation Depreciation	3112000	USD
CY2018	us-gaap	Depreciation Depreciation	3437000	USD
CY2020	us-gaap	Accretion Amortization Of Discounts And Premiums Investments AccretionAmortizationOfDiscountsAndPremiumsInvestments	-1842000	USD
CY2019	us-gaap	Accretion Amortization Of Discounts And Premiums Investments AccretionAmortizationOfDiscountsAndPremiumsInvestments	-1055000	USD
CY2018	us-gaap	Accretion Amortization Of Discounts And Premiums Investments AccretionAmortizationOfDiscountsAndPremiumsInvestments	-1304000	USD
CY2020	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	1730000	USD
CY2019	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	248000	USD
CY2018	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	351000	USD
CY2020	us-gaap	Proceeds From Sale Of Loans Held For Sale ProceedsFromSaleOfLoansHeldForSale	47996000	USD
CY2019	us-gaap	Proceeds From Sale Of Loans Held For Sale ProceedsFromSaleOfLoansHeldForSale	12488000	USD
CY2018	us-gaap	Proceeds From Sale Of Loans Held For Sale ProceedsFromSaleOfLoansHeldForSale	18262000	USD
CY2020	us-gaap	Payments For Origination And Purchases Of Loans Held For Sale PaymentsForOriginationAndPurchasesOfLoansHeldForSale	45251000	USD
CY2019	us-gaap	Payments For Origination And Purchases Of Loans Held For Sale PaymentsForOriginationAndPurchasesOfLoansHeldForSale	12923000	USD
CY2018	us-gaap	Payments For Origination And Purchases Of Loans Held For Sale PaymentsForOriginationAndPurchasesOfLoansHeldForSale	17871000	USD
CY2020	chmg	Gains Losses On Sales Of Other Real Estate Net GainsLossesOnSalesOfOtherRealEstateNet	-46000	USD
CY2019	chmg	Gains Losses On Sales Of Other Real Estate Net GainsLossesOnSalesOfOtherRealEstateNet	-99000	USD
CY2018	chmg	Gains Losses On Sales Of Other Real Estate Net GainsLossesOnSalesOfOtherRealEstateNet	90000	USD
CY2020	chmg	Other Real Estate Owned Writedown OtherRealEstateOwnedWritedown	38000	USD
CY2019	chmg	Other Real Estate Owned Writedown OtherRealEstateOwnedWritedown	53000	USD
CY2018	chmg	Other Real Estate Owned Writedown OtherRealEstateOwnedWritedown	14000	USD
CY2020	us-gaap	Equity Securities Fv Ni Gain Loss EquitySecuritiesFvNiGainLoss	89000	USD
CY2019	us-gaap	Equity Securities Fv Ni Gain Loss EquitySecuritiesFvNiGainLoss	81000	USD
CY2018	us-gaap	Equity Securities Fv Ni Gain Loss EquitySecuritiesFvNiGainLoss	2004000	USD
CY2020	us-gaap	Debt Securities Realized Gain Loss DebtSecuritiesRealizedGainLoss	0	USD
CY2019	us-gaap	Debt Securities Realized Gain Loss DebtSecuritiesRealizedGainLoss	19000	USD
CY2018	us-gaap	Debt Securities Realized Gain Loss DebtSecuritiesRealizedGainLoss	0	USD
CY2020	us-gaap	Proceeds From Sale Of Trading Securities Heldforinvestment ProceedsFromSaleOfTradingSecuritiesHeldforinvestment	91000	USD
CY2019	us-gaap	Proceeds From Sale Of Trading Securities Heldforinvestment ProceedsFromSaleOfTradingSecuritiesHeldforinvestment	22000	USD
CY2018	us-gaap	Proceeds From Sale Of Trading Securities Heldforinvestment ProceedsFromSaleOfTradingSecuritiesHeldforinvestment	2288000	USD
CY2020	us-gaap	Increase Decrease In Debt Securities Trading IncreaseDecreaseInDebtSecuritiesTrading	370000	USD
CY2019	us-gaap	Increase Decrease In Debt Securities Trading IncreaseDecreaseInDebtSecuritiesTrading	206000	USD
CY2018	us-gaap	Increase Decrease In Debt Securities Trading IncreaseDecreaseInDebtSecuritiesTrading	167000	USD
CY2020	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	9883000	USD
CY2019	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	1945000	USD
CY2018	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	2651000	USD
CY2020	us-gaap	Increase Decrease In Interest Payable Net IncreaseDecreaseInInterestPayableNet	-37000	USD
CY2019	us-gaap	Increase Decrease In Interest Payable Net IncreaseDecreaseInInterestPayableNet	67000	USD
CY2018	us-gaap	Increase Decrease In Interest Payable Net IncreaseDecreaseInInterestPayableNet	84000	USD
CY2018	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	66000	USD
CY2020	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	28659000	USD
CY2020	chmg	Restricted Stock Expense Directors Deferred Compensation Plan RestrictedStockExpenseDirectorsDeferredCompensationPlan	29000	USD
CY2019	chmg	Restricted Stock Expense Directors Deferred Compensation Plan RestrictedStockExpenseDirectorsDeferredCompensationPlan	42000	USD
CY2018	chmg	Restricted Stock Expense Directors Deferred Compensation Plan RestrictedStockExpenseDirectorsDeferredCompensationPlan	67000	USD
CY2020	chmg	Expense Related To Employee Stock Compensation ExpenseRelatedToEmployeeStockCompensation	101000	USD
CY2019	chmg	Expense Related To Employee Stock Compensation ExpenseRelatedToEmployeeStockCompensation	100000	USD
CY2018	chmg	Expense Related To Employee Stock Compensation ExpenseRelatedToEmployeeStockCompensation	89000	USD
CY2020	chmg	Expense Related To Employee Stock Awards ExpenseRelatedToEmployeeStockAwards	672000	USD
CY2019	chmg	Expense Related To Employee Stock Awards ExpenseRelatedToEmployeeStockAwards	503000	USD
CY2018	chmg	Expense Related To Employee Stock Awards ExpenseRelatedToEmployeeStockAwards	405000	USD
CY2020	us-gaap	Operating Lease Payments OperatingLeasePayments	820000	USD
CY2019	us-gaap	Operating Lease Payments OperatingLeasePayments	629000	USD
CY2018	us-gaap	Operating Lease Payments OperatingLeasePayments	0	USD
CY2020	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	8265000	USD
CY2019	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	3333000	USD
CY2018	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	-654000	USD
CY2020	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	161000	USD
CY2019	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	63000	USD
CY2019	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	26405000	USD
CY2018	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	27772000	USD
CY2020	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	0	USD
CY2019	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	33690000	USD
CY2018	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	0	USD
CY2020	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	67888000	USD
CY2019	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	49665000	USD
CY2018	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	64180000	USD
CY2020	us-gaap	Proceeds From Sale And Maturity Of Held To Maturity Securities ProceedsFromSaleAndMaturityOfHeldToMaturitySecurities	2007000	USD
CY2019	us-gaap	Proceeds From Sale And Maturity Of Held To Maturity Securities ProceedsFromSaleAndMaturityOfHeldToMaturitySecurities	2903000	USD
CY2018	us-gaap	Proceeds From Sale And Maturity Of Held To Maturity Securities ProceedsFromSaleAndMaturityOfHeldToMaturitySecurities	1316000	USD
CY2020	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	329836000	USD
CY2019	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	118151000	USD
CY2018	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	16033000	USD
CY2020	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	1361000	USD
CY2019	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	1143000	USD
CY2018	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	2410000	USD
CY2020	us-gaap	Payments To Acquire Federal Reserve Stock PaymentsToAcquireFederalReserveStock	51000	USD
CY2019	us-gaap	Payments To Acquire Federal Reserve Stock PaymentsToAcquireFederalReserveStock	14000	USD
CY2018	us-gaap	Payments To Acquire Federal Reserve Stock PaymentsToAcquireFederalReserveStock	22003000	USD
CY2020	us-gaap	Proceeds From Sale Of Federal Reserve Stock ProceedsFromSaleOfFederalReserveStock	0	USD
CY2019	us-gaap	Proceeds From Sale Of Federal Reserve Stock ProceedsFromSaleOfFederalReserveStock	53000	USD
CY2018	us-gaap	Proceeds From Sale Of Federal Reserve Stock ProceedsFromSaleOfFederalReserveStock	24649000	USD
CY2020	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	867000	USD
CY2019	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	883000	USD
CY2018	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	1770000	USD
CY2020	us-gaap	Proceeds From Sale Of Other Real Estate ProceedsFromSaleOfOtherRealEstate	627000	USD
CY2019	us-gaap	Proceeds From Sale Of Other Real Estate ProceedsFromSaleOfOtherRealEstate	458000	USD
CY2018	us-gaap	Proceeds From Sale Of Other Real Estate ProceedsFromSaleOfOtherRealEstate	1709000	USD
CY2020	us-gaap	Proceeds From Sale Of Finance Receivables ProceedsFromSaleOfFinanceReceivables	5227000	USD
CY2019	us-gaap	Proceeds From Sale Of Finance Receivables ProceedsFromSaleOfFinanceReceivables	0	USD
CY2018	us-gaap	Proceeds From Sale Of Finance Receivables ProceedsFromSaleOfFinanceReceivables	0	USD
CY2020	us-gaap	Proceeds From Life Insurance Policies ProceedsFromLifeInsurancePolicies	213000	USD
CY2019	us-gaap	Proceeds From Life Insurance Policies ProceedsFromLifeInsurancePolicies	0	USD
CY2018	us-gaap	Proceeds From Life Insurance Policies ProceedsFromLifeInsurancePolicies	0	USD
CY2020	us-gaap	Payments For Proceeds From Loans Receivable PaymentsForProceedsFromLoansReceivable	239695000	USD
CY2019	us-gaap	Payments For Proceeds From Loans Receivable PaymentsForProceedsFromLoansReceivable	-711000	USD
CY2018	us-gaap	Payments For Proceeds From Loans Receivable PaymentsForProceedsFromLoansReceivable	5719000	USD
CY2020	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-495848000	USD
CY2019	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-32711000	USD
CY2018	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	43919000	USD
CY2020	us-gaap	Increase Decrease In Other Deposits IncreaseDecreaseInOtherDeposits	341081000	USD
CY2019	us-gaap	Increase Decrease In Other Deposits IncreaseDecreaseInOtherDeposits	-8050000	USD
CY2018	us-gaap	Increase Decrease In Other Deposits IncreaseDecreaseInOtherDeposits	69927000	USD
CY2020	us-gaap	Increase Decrease In Time Deposits IncreaseDecreaseInTimeDeposits	124555000	USD
CY2019	us-gaap	Increase Decrease In Time Deposits IncreaseDecreaseInTimeDeposits	10951000	USD
CY2018	us-gaap	Increase Decrease In Time Deposits IncreaseDecreaseInTimeDeposits	31864000	USD
CY2020	us-gaap	Proceeds From Payments For In Securities Sold Under Agreements To Repurchase ProceedsFromPaymentsForInSecuritiesSoldUnderAgreementsToRepurchase	0	USD
CY2019	us-gaap	Proceeds From Payments For In Securities Sold Under Agreements To Repurchase ProceedsFromPaymentsForInSecuritiesSoldUnderAgreementsToRepurchase	0	USD
CY2018	us-gaap	Proceeds From Payments For In Securities Sold Under Agreements To Repurchase ProceedsFromPaymentsForInSecuritiesSoldUnderAgreementsToRepurchase	-10000000	USD
CY2018	us-gaap	Proceeds From Sale Of Treasury Stock ProceedsFromSaleOfTreasuryStock	643000	USD
CY2020	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	5006000	USD
CY2020	chmg	Repayments Of Fhlbny Overnight Advances RepaymentsOfFHLBNYOvernightAdvances	0	USD
CY2019	chmg	Repayments Of Fhlbny Overnight Advances RepaymentsOfFHLBNYOvernightAdvances	0	USD
CY2018	chmg	Repayments Of Fhlbny Overnight Advances RepaymentsOfFHLBNYOvernightAdvances	57700000	USD
CY2020	us-gaap	Repayments Of Federal Home Loan Bank Borrowings RepaymentsOfFederalHomeLoanBankBorrowings	0	USD
CY2019	us-gaap	Repayments Of Federal Home Loan Bank Borrowings RepaymentsOfFederalHomeLoanBankBorrowings	0	USD
CY2018	us-gaap	Repayments Of Federal Home Loan Bank Borrowings RepaymentsOfFederalHomeLoanBankBorrowings	2000000	USD
CY2020	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	236000	USD
CY2019	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	219000	USD
CY2018	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	213000	USD
CY2020	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	7589000	USD
CY2019	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	0	USD
CY2018	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	0	USD
CY2020	us-gaap	Proceeds From Sale Of Treasury Stock ProceedsFromSaleOfTreasuryStock	1018000	USD
CY2019	us-gaap	Proceeds From Sale Of Treasury Stock ProceedsFromSaleOfTreasuryStock	585000	USD
CY2019	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	5029000	USD
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	121904000	USD
CY2018Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	129972000	USD
CY2018	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	4969000	USD
CY2020	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	453823000	USD
CY2019	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-1762000	USD
CY2018	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	27552000	USD
CY2020	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	-13366000	USD
CY2019	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	-8068000	USD
CY2018	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	99243000	USD
CY2017Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	30729000	USD
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	108538000	USD
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	121904000	USD
CY2018Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	129972000	USD
CY2020	us-gaap	Interest Paid Net InterestPaidNet	4025000	USD
CY2019	us-gaap	Interest Paid Net InterestPaidNet	6254000	USD
CY2018	us-gaap	Interest Paid Net InterestPaidNet	3989000	USD
CY2020	us-gaap	Income Taxes Paid IncomeTaxesPaid	6005000	USD
CY2019	us-gaap	Income Taxes Paid IncomeTaxesPaid	4455000	USD
CY2018	us-gaap	Income Taxes Paid IncomeTaxesPaid	1730000	USD
CY2020	us-gaap	Transfer Of Other Real Estate TransferOfOtherRealEstate	431000	USD
CY2019	us-gaap	Transfer Of Other Real Estate TransferOfOtherRealEstate	517000	USD
CY2018	us-gaap	Transfer Of Other Real Estate TransferOfOtherRealEstate	267000	USD
CY2020Q4	us-gaap	Dividends Payable Current And Noncurrent DividendsPayableCurrentAndNoncurrent	1214000	USD
CY2019Q4	us-gaap	Dividends Payable Current And Noncurrent DividendsPayableCurrentAndNoncurrent	1263000	USD
CY2018Q4	us-gaap	Dividends Payable Current And Noncurrent DividendsPayableCurrentAndNoncurrent	1254000	USD
CY2020	chmg	Treasury Stock Repurchasedas Payroll Tax Payment TreasuryStockRepurchasedasPayrollTaxPayment	238000	USD
CY2019	chmg	Treasury Stock Repurchasedas Payroll Tax Payment TreasuryStockRepurchasedasPayrollTaxPayment	185000	USD
CY2018	chmg	Treasury Stock Repurchasedas Payroll Tax Payment TreasuryStockRepurchasedasPayrollTaxPayment	112000	USD
CY2020	chmg	Distribution Of Shares Of Treasury Stock For Directors Deferred Compensation Value DistributionOfSharesOfTreasuryStockForDirectorsDeferredCompensationValue	-14000	USD
CY2019	chmg	Distribution Of Shares Of Treasury Stock For Directors Deferred Compensation Value DistributionOfSharesOfTreasuryStockForDirectorsDeferredCompensationValue	13000	USD
CY2018	chmg	Distribution Of Shares Of Treasury Stock For Directors Deferred Compensation Value DistributionOfSharesOfTreasuryStockForDirectorsDeferredCompensationValue	218000	USD
CY2020	chmg	Distribution Of Shares Of Treasury Stock For Directors Compensation Value DistributionOfSharesOfTreasuryStockForDirectorsCompensationValue	350000	USD
CY2019	chmg	Distribution Of Shares Of Treasury Stock For Directors Compensation Value DistributionOfSharesOfTreasuryStockForDirectorsCompensationValue	356000	USD
CY2018	chmg	Distribution Of Shares Of Treasury Stock For Directors Compensation Value DistributionOfSharesOfTreasuryStockForDirectorsCompensationValue	301000	USD
CY2020	chmg	Treasury Stock Issued During Period Value Restricted Stock Award Forfeitures TreasuryStockIssuedDuringPeriodValueRestrictedStockAwardForfeitures	5000	USD
CY2019	chmg	Treasury Stock Issued During Period Value Restricted Stock Award Forfeitures TreasuryStockIssuedDuringPeriodValueRestrictedStockAwardForfeitures	0	USD
CY2018	chmg	Treasury Stock Issued During Period Value Restricted Stock Award Forfeitures TreasuryStockIssuedDuringPeriodValueRestrictedStockAwardForfeitures	0	USD
CY2020Q4	us-gaap	Assets Under Management Carrying Amount AssetsUnderManagementCarryingAmount	2091000000.000	USD
CY2020	chmg	Period Of Delinquency After Which A Loan Is Placed On Non Accrual Status PeriodOfDelinquencyAfterWhichALoanIsPlacedOnNonAccrualStatus	P90D
CY2020	chmg	Number Of Consecutive Months For Which Loans Remain Current Before Non Accrual Loans Are Returned To Accrual Status NumberOfConsecutiveMonthsForWhichLoansRemainCurrentBeforeNonAccrualLoansAreReturnedToAccrualStatus	P6M
CY2020	us-gaap	Financing Receivable Allowance For Credit Losses Policy For Uncollectible Amounts FinancingReceivableAllowanceForCreditLossesPolicyForUncollectibleAmounts	<div style="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:120%">ALLOWANCE FOR LOAN LOSSES</span></div><div><span><br/></span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">The allowance is an amount that management believes will be adequate to absorb probable incurred credit losses on existing loans. The allowance is established based on management’s evaluation of the probable incurred credit losses in our portfolio in accordance with GAAP, and is comprised of both specific valuation allowances and general valuation allowances.</span></div><div style="margin-top:5pt;text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">A loan is classified as impaired when, based on current information and events, it is probable that the Bank will be unable to collect both the principal and interest due under the contractual terms of the loan agreement. Specific valuation allowances are established based on management’s analysis of individually impaired loans. Factors considered by management in determining impairment include payment status, evaluations of the underlying collateral, expected cash flows, and the probability of collecting scheduled principal and interest payments when due. Loans that experience insignificant payment delays and payment shortfalls generally are not classified as impaired. Management determines the significance of payment delays and payment shortfalls on a case-by-case basis, taking into consideration all of the circumstances surrounding the loan and the borrower, including the length of the delay, the reasons for the delay, the borrower’s prior payment record, and the amount of the shortfall in relation to the principal and interest owed. If a loan is determined to be impaired and is placed on nonaccrual status, all future payments received are applied to principal and a portion of the allowance is allocated so that the loan is reported, net, at the present value of estimated future cash flows using the loan’s existing rate or at the fair value of collateral if repayment is expected solely from the collateral.</span></div><div style="margin-top:5pt;text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">The general component covers non-impaired loans and is based on historical loss experience adjusted for current factors. Loans not impaired but classified as substandard and special mention use a historical loss factor on a rolling five year history of net losses. For all other unclassified loans, the historical loss experience is determined by portfolio class and is based on the actual loss history experienced by the Bank over the most recent two years. This actual loss experience is supplemented with other qualitative factors based on the risks present for each portfolio class. These qualitative factors include consideration of the following: (1) lending policies and procedures, including underwriting standards and collection, charge-off and recovery policies, (2) national and local economic and business conditions and developments, including the condition of various market segments, (3) loan profiles and volume of the portfolio, (4) the experience, ability, and depth of lending management and staff, (5) the volume and severity of past due, classified and watch-list loans, non-accrual loans, troubled debt restructurings, and other modifications (6) the quality of the Bank’s loan review system and the degree of oversight by the Bank’s Board of Directors, (7) collateral related issues: secured vs. unsecured, type, declining valuation environment and trend of other related factors, (8) the existence and effect of any concentrations of credit, and changes in the level of such concentrations, (9) the effect of external factors, such as competition and legal and regulatory requirements, on the level of estimated credit losses in the Bank’s current portfolio and (10) the impact of the global economy.</span></div><div style="margin-top:5pt;text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">The allowance for loan losses is increased through a provision for loan losses charged to operations. Loans are charged against the allowance for loan losses when management believes that the collectability of all or a portion of the principal is unlikely. Management's evaluation of the adequacy of the allowance for loan losses is performed on a periodic basis and takes into consideration such factors as the credit risk grade assigned to the loan, historical loan loss experience and review of specific </span></div>impaired loans. While management uses available information to recognize losses on loans, future additions to the allowance may be necessary based on changes in economic conditions.
CY2020	chmg	Rolling Historical Period Of Net Losses Used In Evaluating General Component Of Valuation Allowance For Loans Not Impaired But Classified As Substandard And Special Mention RollingHistoricalPeriodOfNetLossesUsedInEvaluatingGeneralComponentOfValuationAllowanceForLoansNotImpairedButClassifiedAsSubstandardAndSpecialMention	P5Y
CY2020	chmg	Number Of Most Recent Years Of Actual Loss History Used In Determining Historical Loss Experience For All Other Unclassified Loans NumberOfMostRecentYearsOfActualLossHistoryUsedInDeterminingHistoricalLossExperienceForAllOtherUnclassifiedLoans	P2Y
CY2019Q4	us-gaap	Assets Under Management Carrying Amount AssetsUnderManagementCarryingAmount	1915000000	USD
CY2020	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	2	segment
CY2020	us-gaap	Prior Period Reclassification Adjustment Description PriorPeriodReclassificationAdjustmentDescription	<div style="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:120%">RECLASSIFICATION</span></div><div><span><br/></span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">Amounts in the prior years' consolidated financial statements are reclassified whenever necessary to conform to the current year's presentation. Reclassification adjustments had no impact on prior year net income or shareholders' equity.</span></div>
CY2020Q4	us-gaap	Restricted Cash And Cash Equivalents RestrictedCashAndCashEquivalents	1600000	USD
CY2019Q4	us-gaap	Restricted Cash And Cash Equivalents RestrictedCashAndCashEquivalents	1600000	USD
CY2019Q4	us-gaap	Derivative Collateral Obligation To Return Cash DerivativeCollateralObligationToReturnCash	9400000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost	27215000	USD
CY2020Q4	us-gaap	Derivative Collateral Obligation To Return Cash DerivativeCollateralObligationToReturnCash	19100000	USD
CY2020Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	542362000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	554611000	USD
CY2019Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	282256000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	284090000	USD
CY2020Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	12654000	USD
CY2020Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	405000	USD
CY2019Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	3146000	USD
CY2019Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	1312000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities Within One Year Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost		USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities Within One Year Fair Value AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue		USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	28757000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost	21688000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	22875000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost	759000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue	808000	USD
CY2020Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	542362000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	554611000	USD
CY2020	us-gaap	Debt Securities Available For Sale Gain Loss DebtSecuritiesAvailableForSaleGainLoss	0	USD
CY2019	us-gaap	Debt Securities Available For Sale Gain Loss DebtSecuritiesAvailableForSaleGainLoss	8513000	USD
CY2018	us-gaap	Debt Securities Available For Sale Gain Loss DebtSecuritiesAvailableForSaleGainLoss	0	USD
CY2020	us-gaap	Debt Securities Available For Sale Realized Gain DebtSecuritiesAvailableForSaleRealizedGain	0	USD
CY2019	us-gaap	Debt Securities Available For Sale Realized Gain DebtSecuritiesAvailableForSaleRealizedGain	159000	USD
CY2018	us-gaap	Debt Securities Available For Sale Realized Gain DebtSecuritiesAvailableForSaleRealizedGain	0	USD
CY2020	us-gaap	Debt Securities Available For Sale Realized Loss DebtSecuritiesAvailableForSaleRealizedLoss	0	USD
CY2019	us-gaap	Debt Securities Available For Sale Realized Loss DebtSecuritiesAvailableForSaleRealizedLoss	140000	USD
CY2018	us-gaap	Debt Securities Available For Sale Realized Loss DebtSecuritiesAvailableForSaleRealizedLoss	0	USD
CY2020	chmg	Tax Expense From Sale Of Available For Sale Securities Debt TaxExpenseFromSaleOfAvailableForSaleSecuritiesDebt	0	USD
CY2019	chmg	Tax Expense From Sale Of Available For Sale Securities Debt TaxExpenseFromSaleOfAvailableForSaleSecuritiesDebt	5000	USD
CY2018	chmg	Tax Expense From Sale Of Available For Sale Securities Debt TaxExpenseFromSaleOfAvailableForSaleSecuritiesDebt	0	USD
CY2020Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	2469000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	2501000	USD
CY2019Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	3115000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	3139000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Gain HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain	32000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Loss HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss	0	USD
CY2019Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Gain HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain	24000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Loss HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss	0	USD
CY2019	us-gaap	Held To Maturity Securities Sold Security Realized Gain Loss HeldToMaturitySecuritiesSoldSecurityRealizedGainLoss	0	USD
CY2020	us-gaap	Held To Maturity Securities Sold Security Realized Gain Loss HeldToMaturitySecuritiesSoldSecurityRealizedGainLoss	0	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount	856000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Fair Value HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearFairValue	863000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsNetCarryingAmount	1613000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	1638000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities After Five Through Ten Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsNetCarryingAmount	0	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities After Five Through Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	0	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsNetCarryingAmount	0	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsFairValue	0	USD
CY2020Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	2469000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	2501000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months	88270000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	368000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger	4606000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	37000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position DebtSecuritiesAvailableForSaleUnrealizedLossPosition	92876000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position Accumulated Loss DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss	405000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months	74520000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	800000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger	55748000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	512000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position DebtSecuritiesAvailableForSaleUnrealizedLossPosition	130268000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position Accumulated Loss DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss	1312000	USD
CY2020Q4	us-gaap	Financial Instruments Owned And Pledged As Collateral At Fair Value FinancialInstrumentsOwnedAndPledgedAsCollateralAtFairValue	180800000	USD
CY2019Q4	us-gaap	Financial Instruments Owned And Pledged As Collateral At Fair Value FinancialInstrumentsOwnedAndPledgedAsCollateralAtFairValue	205900000	USD
CY2020Q4	us-gaap	Notes Receivable Gross NotesReceivableGross	1536463000	USD
CY2019Q4	us-gaap	Notes Receivable Gross NotesReceivableGross	1309219000	USD
CY2020Q4	us-gaap	Interest Receivable InterestReceivable	5035000	USD
CY2019Q4	us-gaap	Interest Receivable InterestReceivable	3684000	USD
CY2020Q4	chmg	Financing Receivable After Interest Receivable On Loans Before Allowance On Credit Loss FinancingReceivableAfterInterestReceivableOnLoansBeforeAllowanceOnCreditLoss	1541498000	USD
CY2019Q4	chmg	Financing Receivable After Interest Receivable On Loans Before Allowance On Credit Loss FinancingReceivableAfterInterestReceivableOnLoansBeforeAllowanceOnCreditLoss	1312903000	USD
CY2020Q4	us-gaap	Loans Receivable Held For Sale Net Not Part Of Disposal Group LoansReceivableHeldForSaleNetNotPartOfDisposalGroup	200000	USD
CY2019Q4	us-gaap	Loans Receivable Held For Sale Net Not Part Of Disposal Group LoansReceivableHeldForSaleNetNotPartOfDisposalGroup	1200000	USD
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	23478000	USD
CY2020	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	7380000	USD
CY2020	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	587000	USD
CY2020	chmg	Financing Receivable Allowance For Credit Losses Net Charge Off FinancingReceivableAllowanceForCreditLossesNetChargeOff	-6793000	USD
CY2020	us-gaap	Provision For Loan Losses Expensed ProvisionForLoanLossesExpensed	4239000	USD
CY2020Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	20924000	USD
CY2018Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	18944000	USD
CY2019	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	1975000	USD
CY2019	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	564000	USD
CY2019	chmg	Financing Receivable Allowance For Credit Losses Net Charge Off FinancingReceivableAllowanceForCreditLossesNetChargeOff	-1411000	USD
CY2019	us-gaap	Provision For Loan Losses Expensed ProvisionForLoanLossesExpensed	5945000	USD
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	23478000	USD
CY2017Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	21161000	USD
CY2018	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	5919000	USD
CY2018	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	549000	USD
CY2018	chmg	Financing Receivable Allowance For Credit Losses Net Charge Off FinancingReceivableAllowanceForCreditLossesNetChargeOff	-5370000	USD
CY2018	us-gaap	Provision For Loan Losses Expensed ProvisionForLoanLossesExpensed	3153000	USD
CY2018Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	18944000	USD
CY2020Q4	us-gaap	Financing Receivable Allowance For Credit Losses Individually Evaluated For Impairment1 FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1	1527000	USD
CY2020Q4	us-gaap	Financing Receivable Allowance For Credit Losses Collectively Evaluated For Impairment FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment	19397000	USD
CY2020Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	20924000	USD
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses Individually Evaluated For Impairment1 FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1	8097000	USD
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses Collectively Evaluated For Impairment FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment	15381000	USD
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	23478000	USD
CY2020Q4	us-gaap	Financing Receivable Individually Evaluated For Impairment FinancingReceivableIndividuallyEvaluatedForImpairment	10589000	USD
CY2020Q4	us-gaap	Financing Receivable Collectively Evaluated For Impairment FinancingReceivableCollectivelyEvaluatedForImpairment	1530909000	USD
CY2020Q4	chmg	Financing Receivable After Interest Receivable On Loans Before Allowance On Credit Loss FinancingReceivableAfterInterestReceivableOnLoansBeforeAllowanceOnCreditLoss	1541498000	USD
CY2019Q4	us-gaap	Financing Receivable Individually Evaluated For Impairment FinancingReceivableIndividuallyEvaluatedForImpairment	15665000	USD
CY2019Q4	us-gaap	Financing Receivable Collectively Evaluated For Impairment FinancingReceivableCollectivelyEvaluatedForImpairment	1297238000	USD
CY2019Q4	chmg	Financing Receivable After Interest Receivable On Loans Before Allowance On Credit Loss FinancingReceivableAfterInterestReceivableOnLoansBeforeAllowanceOnCreditLoss	1312903000	USD
CY2020Q4	us-gaap	Impaired Financing Receivable Unpaid Principal Balance ImpairedFinancingReceivableUnpaidPrincipalBalance	16546000	USD
CY2020Q4	us-gaap	Impaired Financing Receivable Recorded Investment ImpairedFinancingReceivableRecordedInvestment	10589000	USD
CY2020Q4	us-gaap	Impaired Financing Receivable Related Allowance ImpairedFinancingReceivableRelatedAllowance	1527000	USD
CY2019Q4	us-gaap	Impaired Financing Receivable Unpaid Principal Balance ImpairedFinancingReceivableUnpaidPrincipalBalance	15712000	USD
CY2019Q4	us-gaap	Impaired Financing Receivable Recorded Investment ImpairedFinancingReceivableRecordedInvestment	15665000	USD
CY2019Q4	us-gaap	Impaired Financing Receivable Related Allowance ImpairedFinancingReceivableRelatedAllowance	8097000	USD
CY2020	us-gaap	Impaired Financing Receivable With No Related Allowance Average Recorded Investment ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment	14690000	USD
CY2020	us-gaap	Impaired Financing Receivable With No Related Allowance Interest Income Accrual Method ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod	76000	USD
CY2019	us-gaap	Impaired Financing Receivable With No Related Allowance Average Recorded Investment ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment	14423000	USD
CY2019	us-gaap	Impaired Financing Receivable With No Related Allowance Interest Income Accrual Method ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod	72000	USD
CY2018	us-gaap	Impaired Financing Receivable With No Related Allowance Average Recorded Investment ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment	10972000	USD
CY2018	us-gaap	Impaired Financing Receivable With No Related Allowance Interest Income Accrual Method ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod	61000	USD
CY2020Q4	us-gaap	Financing Receivable Recorded Investment Nonaccrual Status FinancingReceivableRecordedInvestmentNonaccrualStatus	9952000	USD
CY2019Q4	us-gaap	Financing Receivable Recorded Investment Nonaccrual Status FinancingReceivableRecordedInvestmentNonaccrualStatus	18008000	USD
CY2020Q4	us-gaap	Financing Receivable Recorded Investment90 Days Past Due And Still Accruing FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing	2000	USD
CY2019Q4	us-gaap	Financing Receivable Recorded Investment90 Days Past Due And Still Accruing FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing	7000	USD
CY2020Q4	us-gaap	Financing Receivable Recorded Investment Past Due FinancingReceivableRecordedInvestmentPastDue	10480000	USD
CY2020Q4	us-gaap	Financing Receivable Recorded Investment Current FinancingReceivableRecordedInvestmentCurrent	1531018000	USD
CY2020Q4	chmg	Financing Receivable After Interest Receivable On Loans Before Allowance On Credit Loss FinancingReceivableAfterInterestReceivableOnLoansBeforeAllowanceOnCreditLoss	1541498000	USD
CY2019Q4	us-gaap	Financing Receivable Recorded Investment Past Due FinancingReceivableRecordedInvestmentPastDue	14370000	USD
CY2019Q4	us-gaap	Financing Receivable Recorded Investment Current FinancingReceivableRecordedInvestmentCurrent	1298533000	USD
CY2019Q4	chmg	Financing Receivable After Interest Receivable On Loans Before Allowance On Credit Loss FinancingReceivableAfterInterestReceivableOnLoansBeforeAllowanceOnCreditLoss	1312903000	USD
CY2020Q4	us-gaap	Financing Receivable Modifications Recorded Investment FinancingReceivableModificationsRecordedInvestment	6700000	USD
CY2019Q4	us-gaap	Financing Receivable Modifications Recorded Investment FinancingReceivableModificationsRecordedInvestment	9000000.0	USD
CY2018Q4	us-gaap	Financing Receivable Modifications Recorded Investment FinancingReceivableModificationsRecordedInvestment	6800000	USD
CY2020Q4	chmg	Financing Receivable Modifications Recorded Investment Still Accruing FinancingReceivableModificationsRecordedInvestmentStillAccruing	2800000	USD
CY2019	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	3	loan
CY2019	us-gaap	Operating Lease Expense OperatingLeaseExpense	1000000.0	USD
CY2020Q4	chmg	Financing Receivable Troubled Debt Restructuring Purchasedwith Credit Deterioration Increase FinancingReceivableTroubledDebtRestructuringPurchasedwithCreditDeteriorationIncrease	400000	USD
CY2019Q4	chmg	Financing Receivable Troubled Debt Restructuring Purchasedwith Credit Deterioration Increase FinancingReceivableTroubledDebtRestructuringPurchasedwithCreditDeteriorationIncrease	2300000	USD
CY2018Q4	chmg	Financing Receivable Troubled Debt Restructuring Purchasedwith Credit Deterioration Increase FinancingReceivableTroubledDebtRestructuringPurchasedwithCreditDeteriorationIncrease	900000	USD
CY2020Q4	chmg	Financing Receivable Modifications Recorded Investment Nonaccrual Status FinancingReceivableModificationsRecordedInvestmentNonaccrualStatus	3900000	USD
CY2019Q4	chmg	Financing Receivable Modifications Recorded Investment Still Accruing FinancingReceivableModificationsRecordedInvestmentStillAccruing	900000	USD
CY2019Q4	chmg	Financing Receivable Modifications Recorded Investment Nonaccrual Status FinancingReceivableModificationsRecordedInvestmentNonaccrualStatus	8100000	USD
CY2018Q4	chmg	Financing Receivable Modifications Recorded Investment Still Accruing FinancingReceivableModificationsRecordedInvestmentStillAccruing	800000	USD
CY2018Q4	chmg	Financing Receivable Modifications Recorded Investment Nonaccrual Status FinancingReceivableModificationsRecordedInvestmentNonaccrualStatus	6000000.0	USD
CY2020Q4	chmg	Additional Amounts Committed To Customers With Loans Classified As Troubled Debt Restructurings AdditionalAmountsCommittedToCustomersWithLoansClassifiedAsTroubledDebtRestructurings	17000	USD
CY2019Q4	chmg	Additional Amounts Committed To Customers With Loans Classified As Troubled Debt Restructurings AdditionalAmountsCommittedToCustomersWithLoansClassifiedAsTroubledDebtRestructurings	0	USD
CY2018Q4	chmg	Additional Amounts Committed To Customers With Loans Classified As Troubled Debt Restructurings AdditionalAmountsCommittedToCustomersWithLoansClassifiedAsTroubledDebtRestructurings	0	USD
CY2020	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	15	loan
CY2020	us-gaap	Financing Receivable Modifications Pre Modification Recorded Investment2 FinancingReceivableModificationsPreModificationRecordedInvestment2	5100000	USD
CY2020	us-gaap	Financing Receivable Modifications Post Modification Recorded Investment2 FinancingReceivableModificationsPostModificationRecordedInvestment2	5100000	USD
CY2020	us-gaap	Allowance For Loan And Lease Losses Period Increase Decrease AllowanceForLoanAndLeaseLossesPeriodIncreaseDecrease	200000	USD
CY2020	us-gaap	Financing Receivables Impaired Troubled Debt Restructuring Write Down FinancingReceivablesImpairedTroubledDebtRestructuringWriteDown	0	USD
CY2019	us-gaap	Financing Receivable Modifications Pre Modification Recorded Investment2 FinancingReceivableModificationsPreModificationRecordedInvestment2	4483000	USD
CY2019	us-gaap	Financing Receivable Modifications Post Modification Recorded Investment2 FinancingReceivableModificationsPostModificationRecordedInvestment2	4483000	USD
CY2019	us-gaap	Allowance For Loan And Lease Losses Period Increase Decrease AllowanceForLoanAndLeaseLossesPeriodIncreaseDecrease	1700000	USD
CY2019	us-gaap	Financing Receivables Impaired Troubled Debt Restructuring Write Down FinancingReceivablesImpairedTroubledDebtRestructuringWriteDown	0	USD
CY2018	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	2	loan
CY2018	us-gaap	Financing Receivable Modifications Pre Modification Recorded Investment2 FinancingReceivableModificationsPreModificationRecordedInvestment2	491000	USD
CY2018	us-gaap	Financing Receivable Modifications Post Modification Recorded Investment2 FinancingReceivableModificationsPostModificationRecordedInvestment2	491000	USD
CY2018	us-gaap	Allowance For Loan And Lease Losses Period Increase Decrease AllowanceForLoanAndLeaseLossesPeriodIncreaseDecrease	400000	USD
CY2018	us-gaap	Financing Receivables Impaired Troubled Debt Restructuring Write Down FinancingReceivablesImpairedTroubledDebtRestructuringWriteDown	0	USD
CY2020	chmg	Number Of Days Past Due After Which A Loan Is Considered To Be In Payment Default NumberOfDaysPastDueAfterWhichALoanIsConsideredToBeInPaymentDefault	P90D
CY2020	us-gaap	Financing Receivable Modifications Subsequent Default Number Of Contracts1 FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1	1	instrument
CY2020	us-gaap	Financing Receivable Modifications Subsequent Default Recorded Investment1 FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1	170000	USD
CY2020	chmg	Number Of Days Past Due After Which A Loan Will Be Rated NumberOfDaysPastDueAfterWhichALoanWillBeRated	P90D
CY2020Q4	chmg	Financing Receivable After Interest Receivable On Loans Before Allowance On Credit Loss FinancingReceivableAfterInterestReceivableOnLoansBeforeAllowanceOnCreditLoss	1541498000	USD
CY2019Q4	chmg	Financing Receivable After Interest Receivable On Loans Before Allowance On Credit Loss FinancingReceivableAfterInterestReceivableOnLoansBeforeAllowanceOnCreditLoss	1312903000	USD
CY2020Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	89293000	USD
CY2019Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	89088000	USD
CY2020Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	69174000	USD
CY2019Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	66671000	USD
CY2020Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	20119000	USD
CY2019Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	22417000	USD
CY2020	us-gaap	Depreciation Depreciation	2900000	USD
CY2019	us-gaap	Depreciation Depreciation	3100000	USD
CY2018	us-gaap	Depreciation Depreciation	3400000	USD
CY2020Q4	chmg	Finance Lease Right Of Use Asset Before Accumulated Amortization FinanceLeaseRightOfUseAssetBeforeAccumulatedAmortization	5572000	USD
CY2019Q4	chmg	Finance Lease Right Of Use Asset Before Accumulated Amortization FinanceLeaseRightOfUseAssetBeforeAccumulatedAmortization	5572000	USD
CY2020Q4	chmg	Finance Lease Right Of Use Asset Accumulated Amortization FinanceLeaseRightOfUseAssetAccumulatedAmortization	1875000	USD
CY2019Q4	chmg	Finance Lease Right Of Use Asset Accumulated Amortization FinanceLeaseRightOfUseAssetAccumulatedAmortization	1541000	USD
CY2020Q4	chmg	Finance Lease Right Of Use Asset After Accumulated Amortization FinanceLeaseRightOfUseAssetAfterAccumulatedAmortization	3697000	USD
CY2019Q4	chmg	Finance Lease Right Of Use Asset After Accumulated Amortization FinanceLeaseRightOfUseAssetAfterAccumulatedAmortization	4031000	USD
CY2020Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P10Y3M18D
CY2020Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.0339
CY2020	us-gaap	Operating Lease Expense OperatingLeaseExpense	1000000.0	USD
CY2018	us-gaap	Lease And Rental Expense LeaseAndRentalExpense	1100000	USD
CY2020Q4	chmg	Operating Lease Liability Lease Termination OperatingLeaseLiabilityLeaseTermination	200000	USD
CY2020Q4	chmg	Operating Lease Right Of Use Asset Gross OperatingLeaseRightOfUseAssetGross	8001000	USD
CY2019Q4	chmg	Operating Lease Right Of Use Asset Gross OperatingLeaseRightOfUseAssetGross	8713000	USD
CY2020Q4	chmg	Operating Lease Right Of Use Asset Accumulated Amortization OperatingLeaseRightOfUseAssetAccumulatedAmortization	705000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Three LesseeOperatingLeaseLiabilityPaymentsDueYearThree	866000	USD
CY2019Q4	chmg	Operating Lease Right Of Use Asset Accumulated Amortization OperatingLeaseRightOfUseAssetAccumulatedAmortization	712000	USD
CY2020Q4	chmg	Operating Lease Right Of Use Asset Lease Termination OperatingLeaseRightOfUseAssetLeaseTermination	151000	USD
CY2019Q4	chmg	Operating Lease Right Of Use Asset Lease Termination OperatingLeaseRightOfUseAssetLeaseTermination	0	USD
CY2020Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	7145000	USD
CY2019Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	8001000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Next Twelve Months LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths	907000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Two LesseeOperatingLeaseLiabilityPaymentsDueYearTwo	846000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Four LesseeOperatingLeaseLiabilityPaymentsDueYearFour	857000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Five LesseeOperatingLeaseLiabilityPaymentsDueYearFive	841000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due After Year Five LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive	4349000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due LesseeOperatingLeaseLiabilityPaymentsDue	8666000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Undiscounted Excess Amount LesseeOperatingLeaseLiabilityUndiscountedExcessAmount	1402000	USD
CY2020Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	7264000	USD
CY2020Q4	chmg	Lessee Operating Lease Lease Not Yet Commenced Liability LesseeOperatingLeaseLeaseNotYetCommencedLiability	0	USD
CY2020Q4	us-gaap	Finance Lease Weighted Average Remaining Lease Term1 FinanceLeaseWeightedAverageRemainingLeaseTerm1	P12Y1M6D
CY2020Q4	us-gaap	Finance Lease Weighted Average Discount Rate Percent FinanceLeaseWeightedAverageDiscountRatePercent	0.0336
CY2020Q4	us-gaap	Finance Lease Liability Payments Due Next Twelve Months FinanceLeaseLiabilityPaymentsDueNextTwelveMonths	388000	USD
CY2020Q4	us-gaap	Finance Lease Liability Payments Due Year Two FinanceLeaseLiabilityPaymentsDueYearTwo	391000	USD
CY2020Q4	us-gaap	Finance Lease Liability Payments Due Year Three FinanceLeaseLiabilityPaymentsDueYearThree	391000	USD
CY2020Q4	us-gaap	Finance Lease Liability Payments Due Year Four FinanceLeaseLiabilityPaymentsDueYearFour	391000	USD
CY2020Q4	us-gaap	Finance Lease Liability Payments Due Year Five FinanceLeaseLiabilityPaymentsDueYearFive	409000	USD
CY2020Q4	us-gaap	Finance Lease Liability Payments Due After Year Five FinanceLeaseLiabilityPaymentsDueAfterYearFive	2839000	USD
CY2020Q4	us-gaap	Finance Lease Liability Payments Due FinanceLeaseLiabilityPaymentsDue	4809000	USD
CY2020Q4	us-gaap	Finance Lease Liability Undiscounted Excess Amount FinanceLeaseLiabilityUndiscountedExcessAmount	960000	USD
CY2020Q4	us-gaap	Finance Lease Liability FinanceLeaseLiability	3849000	USD
CY2020Q4	chmg	Lessee F Inance Lease Lease Not Yet Commenced Liability LesseeFInanceLeaseLeaseNotYetCommencedLiability	0	USD
CY2020	us-gaap	Goodwill Acquired During Period GoodwillAcquiredDuringPeriod	0	USD
CY2019	us-gaap	Goodwill Acquired During Period GoodwillAcquiredDuringPeriod	0	USD
CY2020Q4	us-gaap	Goodwill Goodwill	21824000	USD
CY2019Q4	us-gaap	Goodwill Goodwill	21824000	USD
CY2019Q4	us-gaap	Goodwill Goodwill	21824000	USD
CY2018Q4	us-gaap	Goodwill Goodwill	21824000	USD
CY2020	us-gaap	Finitelived Intangible Assets Acquired1 FinitelivedIntangibleAssetsAcquired1	11608000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Accumulated Amortization FiniteLivedIntangibleAssetsAccumulatedAmortization	11350000	USD
CY2019	us-gaap	Finitelived Intangible Assets Acquired1 FinitelivedIntangibleAssetsAcquired1	11608000	USD
CY2019Q4	us-gaap	Finite Lived Intangible Assets Accumulated Amortization FiniteLivedIntangibleAssetsAccumulatedAmortization	10866000	USD
CY2020Q4	us-gaap	Deposits Savings Deposits DepositsSavingsDeposits	245865000	USD
CY2019Q4	us-gaap	Deposits Savings Deposits DepositsSavingsDeposits	212393000	USD
CY2020	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	500000	USD
CY2019	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	600000	USD
CY2018	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	700000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Next Twelve Months FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths	258000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	258000	USD
CY2020Q4	us-gaap	Noninterest Bearing Deposit Liabilities NoninterestBearingDepositLiabilities	620423000	USD
CY2019Q4	us-gaap	Noninterest Bearing Deposit Liabilities NoninterestBearingDepositLiabilities	468238000	USD
CY2020Q4	us-gaap	Deposits Negotiable Order Of Withdrawal Now DepositsNegotiableOrderOfWithdrawalNOW	282172000	USD
CY2019Q4	us-gaap	Deposits Negotiable Order Of Withdrawal Now DepositsNegotiableOrderOfWithdrawalNOW	200089000	USD
CY2020Q4	us-gaap	Deposits Money Market Deposits DepositsMoneyMarketDeposits	603583000	USD
CY2019Q4	us-gaap	Deposits Money Market Deposits DepositsMoneyMarketDeposits	530242000	USD
CY2020Q4	us-gaap	Time Deposits TimeDeposits	285731000	USD
CY2019Q4	us-gaap	Time Deposits TimeDeposits	161176000	USD
CY2020Q4	us-gaap	Deposits Deposits	2037774000	USD
CY2019Q4	us-gaap	Deposits Deposits	1572138000	USD
CY2020Q4	us-gaap	Time Deposit Maturities Year One TimeDepositMaturitiesYearOne	193113000	USD
CY2020Q4	us-gaap	Time Deposit Maturities Year Two TimeDepositMaturitiesYearTwo	75890000	USD
CY2020Q4	us-gaap	Time Deposit Maturities Year Three TimeDepositMaturitiesYearThree	12784000	USD
CY2020Q4	us-gaap	Time Deposit Maturities Year Four TimeDepositMaturitiesYearFour	0	USD
CY2020Q4	us-gaap	Time Deposit Maturities Year Five TimeDepositMaturitiesYearFive	1084000	USD
CY2020Q4	us-gaap	Time Deposit Maturities After Year Five TimeDepositMaturitiesAfterYearFive	2860000	USD
CY2020Q4	us-gaap	Time Deposits TimeDeposits	285731000	USD
CY2020Q4	chmg	Time Deposits250000 Or More TimeDeposits250000OrMore	31200000	USD
CY2019Q4	chmg	Time Deposits250000 Or More TimeDeposits250000OrMore	27700000	USD
CY2020	us-gaap	Schedule Of Repurchase Agreements ScheduleOfRepurchaseAgreements	A summary of securities sold under agreements to repurchase as of and for the years ended December 31, 2020, 2019 and 2018 is as follows (in thousands):<table style="border-collapse:collapse;display:inline-table;vertical-align:top;width:99.853%"><tr><td style="width:1.0%"/><td style="width:58.490%"/><td style="width:0.1%"/><td style="width:0.1%"/><td style="width:0.532%"/><td style="width:0.1%"/><td style="width:1.0%"/><td style="width:11.637%"/><td style="width:0.1%"/><td style="width:0.1%"/><td style="width:0.532%"/><td style="width:0.1%"/><td style="width:1.0%"/><td style="width:11.637%"/><td style="width:0.1%"/><td style="width:0.1%"/><td style="width:0.532%"/><td style="width:0.1%"/><td style="width:1.0%"/><td style="width:11.640%"/><td style="width:0.1%"/></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%"> </span></td><td colspan="3" style="padding:0 1pt"/><td colspan="3" style="padding:2px 1pt;text-align:center;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:100%">2020</span></td><td colspan="3" style="padding:0 1pt"/><td colspan="3" style="padding:2px 1pt;text-align:center;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:100%">2019</span></td><td colspan="3" style="padding:0 1pt"/><td colspan="3" style="padding:2px 1pt;text-align:center;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:100%">2018</span></td></tr><tr><td colspan="3" style="background-color:#cceeff;padding:2px 1pt 2px 7.75pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">Balance at December 31</span></td><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">$</span></td><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">— </span></td><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">$</span></td><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">— </span></td><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">$</span></td><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">— </span></td><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr><tr><td colspan="3" style="background-color:#ffffff;padding:2px 1pt 2px 7.75pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">Maximum month-end balance</span></td><td colspan="3" style="background-color:#ffffff;padding:0 1pt"/><td style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">$</span></td><td style="background-color:#ffffff;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">— </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#ffffff;padding:0 1pt"/><td style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">$</span></td><td style="background-color:#ffffff;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">— </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#ffffff;padding:0 1pt"/><td style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">$</span></td><td style="background-color:#ffffff;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">10,000 </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr><tr><td colspan="3" style="background-color:#cceeff;padding:2px 1pt 2px 7.75pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">Average balance during year</span></td><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/><td style="background-color:#cceeff;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">$</span></td><td style="background-color:#cceeff;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">— </span></td><td style="background-color:#cceeff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/><td style="background-color:#cceeff;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">$</span></td><td style="background-color:#cceeff;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">— </span></td><td style="background-color:#cceeff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/><td style="background-color:#cceeff;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">$</span></td><td style="background-color:#cceeff;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">3,644 </span></td><td style="background-color:#cceeff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr><tr><td colspan="3" style="background-color:#ffffff;padding:2px 1pt 2px 7.75pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">Weighted-average interest rate at December 31</span></td><td colspan="3" style="background-color:#ffffff;padding:0 1pt"/><td colspan="2" style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">— </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">%</span></td><td colspan="3" style="background-color:#ffffff;padding:0 1pt"/><td colspan="2" style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">— </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">%</span></td><td colspan="3" style="background-color:#ffffff;padding:0 1pt"/><td colspan="2" style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">— </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">%</span></td></tr><tr><td colspan="3" style="background-color:#cceeff;padding:2px 1pt 2px 7.75pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">Average interest rate paid during year</span></td><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/><td colspan="2" style="background-color:#cceeff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">— </span></td><td style="background-color:#cceeff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">%</span></td><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/><td colspan="2" style="background-color:#cceeff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">— </span></td><td style="background-color:#cceeff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">%</span></td><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/><td colspan="2" style="background-color:#cceeff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">3.77 </span></td><td style="background-color:#cceeff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">%</span></td></tr></table>
CY2020Q4	us-gaap	Securities Sold Under Agreements To Repurchase SecuritiesSoldUnderAgreementsToRepurchase	0	USD
CY2019Q4	us-gaap	Securities Sold Under Agreements To Repurchase SecuritiesSoldUnderAgreementsToRepurchase	0	USD
CY2018Q4	us-gaap	Securities Sold Under Agreements To Repurchase SecuritiesSoldUnderAgreementsToRepurchase	0	USD
CY2020Q4	chmg	Securities Sold Under Agreements To Repurchase Maximum Month End Balance SecuritiesSoldUnderAgreementsToRepurchaseMaximumMonthEndBalance	0	USD
CY2019Q4	chmg	Securities Sold Under Agreements To Repurchase Maximum Month End Balance SecuritiesSoldUnderAgreementsToRepurchaseMaximumMonthEndBalance	0	USD
CY2018Q4	chmg	Securities Sold Under Agreements To Repurchase Maximum Month End Balance SecuritiesSoldUnderAgreementsToRepurchaseMaximumMonthEndBalance	10000000	USD
CY2020	chmg	Securities Sold Under Repurchase Agreements Average Balance During Year SecuritiesSoldUnderRepurchaseAgreementsAverageBalanceDuringYear	0	USD
CY2019	chmg	Securities Sold Under Repurchase Agreements Average Balance During Year SecuritiesSoldUnderRepurchaseAgreementsAverageBalanceDuringYear	0	USD
CY2018	chmg	Securities Sold Under Repurchase Agreements Average Balance During Year SecuritiesSoldUnderRepurchaseAgreementsAverageBalanceDuringYear	3644000	USD
CY2020Q4	us-gaap	Assets Sold Under Agreements To Repurchase Interest Rate AssetsSoldUnderAgreementsToRepurchaseInterestRate	0
CY2019Q4	us-gaap	Assets Sold Under Agreements To Repurchase Interest Rate AssetsSoldUnderAgreementsToRepurchaseInterestRate	0
CY2018Q4	us-gaap	Assets Sold Under Agreements To Repurchase Interest Rate AssetsSoldUnderAgreementsToRepurchaseInterestRate	0
CY2020	chmg	Assets Sold Under Agreements To Repurchase Average Interest Rate Paid During Year AssetsSoldUnderAgreementsToRepurchaseAverageInterestRatePaidDuringYear	0
CY2019	chmg	Assets Sold Under Agreements To Repurchase Average Interest Rate Paid During Year AssetsSoldUnderAgreementsToRepurchaseAverageInterestRatePaidDuringYear	0
CY2018	chmg	Assets Sold Under Agreements To Repurchase Average Interest Rate Paid During Year AssetsSoldUnderAgreementsToRepurchaseAverageInterestRatePaidDuringYear	0.0377
CY2019Q4	us-gaap	Securities Sold Under Agreements To Repurchase SecuritiesSoldUnderAgreementsToRepurchase	0	USD
CY2018Q4	us-gaap	Securities Sold Under Agreements To Repurchase SecuritiesSoldUnderAgreementsToRepurchase	0	USD
CY2020Q4	us-gaap	Securities Sold Under Agreements To Repurchase SecuritiesSoldUnderAgreementsToRepurchase	0	USD
CY2020Q4	us-gaap	Federal Home Loan Bank Advances Branch Of Fhlb Bank Amount Of Advances By Branch FederalHomeLoanBankAdvancesBranchOfFHLBBankAmountOfAdvancesByBranch	0	USD
CY2019Q4	us-gaap	Federal Home Loan Bank Advances Branch Of Fhlb Bank Amount Of Advances By Branch FederalHomeLoanBankAdvancesBranchOfFHLBBankAmountOfAdvancesByBranch	0	USD
CY2020Q4	us-gaap	Federal Home Loan Bank Advances General Debt Obligations Disclosures Maximum Amount Available FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresMaximumAmountAvailable	86300000	USD
CY2020	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	161000	USD
CY2020	us-gaap	Noninterest Income NoninterestIncome	21124000	USD
CY2019	us-gaap	Equity Securities Fv Ni Gain Loss EquitySecuritiesFvNiGainLoss	81000	USD
CY2019	us-gaap	Noninterest Income NoninterestIncome	20073000	USD
CY2018	us-gaap	Equity Securities Fv Ni Gain Loss EquitySecuritiesFvNiGainLoss	2004000	USD
CY2018	us-gaap	Noninterest Income NoninterestIncome	23074000	USD
CY2020	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	280000	USD
CY2020	us-gaap	Unrealized Gain Loss On Derivatives UnrealizedGainLossOnDerivatives	8000	USD
CY2019	us-gaap	Unrealized Gain Loss On Derivatives UnrealizedGainLossOnDerivatives	-224000	USD
CY2018	us-gaap	Unrealized Gain Loss On Derivatives UnrealizedGainLossOnDerivatives	-65000	USD
CY2020	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	4413000	USD
CY2019	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	4603000	USD
CY2018	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	1732000	USD
CY2019	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	395000	USD
CY2018	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	124000	USD
CY2020	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	4693000	USD
CY2019	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	4998000	USD
CY2018	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	1856000	USD
CY2020	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-136000	USD
CY2019	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-1126000	USD
CY2018	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	2253000	USD
CY2020	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	50000	USD
CY2019	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	-438000	USD
CY2018	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	345000	USD
CY2020	us-gaap	Tax Cuts And Jobs Act Of2017 Change In Tax Rate Income Tax Expense Benefit TaxCutsAndJobsActOf2017ChangeInTaxRateIncomeTaxExpenseBenefit	0	USD
CY2019	us-gaap	Tax Cuts And Jobs Act Of2017 Change In Tax Rate Income Tax Expense Benefit TaxCutsAndJobsActOf2017ChangeInTaxRateIncomeTaxExpenseBenefit	0	USD
CY2018	us-gaap	Tax Cuts And Jobs Act Of2017 Change In Tax Rate Income Tax Expense Benefit TaxCutsAndJobsActOf2017ChangeInTaxRateIncomeTaxExpenseBenefit	-445000	USD
CY2020	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-86000	USD
CY2019	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-1564000	USD
CY2018	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	2153000	USD
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	4607000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	3434000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	4009000	USD
CY2020	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.21
CY2019	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.21
CY2018	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.21
CY2020	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	5013000	USD
CY2019	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	3999000	USD
CY2018	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	4963000	USD
CY2020	us-gaap	Income Tax Reconciliation Tax Exempt Income IncomeTaxReconciliationTaxExemptIncome	395000	USD
CY2019	us-gaap	Income Tax Reconciliation Tax Exempt Income IncomeTaxReconciliationTaxExemptIncome	424000	USD
CY2018	us-gaap	Income Tax Reconciliation Tax Exempt Income IncomeTaxReconciliationTaxExemptIncome	430000	USD
CY2020	us-gaap	Income Tax Reconciliation Deductions Other IncomeTaxReconciliationDeductionsOther	296000	USD
CY2019	us-gaap	Income Tax Reconciliation Deductions Other IncomeTaxReconciliationDeductionsOther	189000	USD
CY2018	us-gaap	Income Tax Reconciliation Deductions Other IncomeTaxReconciliationDeductionsOther	167000	USD
CY2020	us-gaap	Income Tax Reconciliation Deductions Dividends IncomeTaxReconciliationDeductionsDividends	5000	USD
CY2019	us-gaap	Income Tax Reconciliation Deductions Dividends IncomeTaxReconciliationDeductionsDividends	7000	USD
CY2018	us-gaap	Income Tax Reconciliation Deductions Dividends IncomeTaxReconciliationDeductionsDividends	7000	USD
CY2020	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	118000	USD
CY2019	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	-86000	USD
CY2018	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	262000	USD
CY2020	us-gaap	Income Tax Reconciliation Nondeductible Expense Other IncomeTaxReconciliationNondeductibleExpenseOther	5000	USD
CY2019	us-gaap	Income Tax Reconciliation Nondeductible Expense Other IncomeTaxReconciliationNondeductibleExpenseOther	9000	USD
CY2018	us-gaap	Income Tax Reconciliation Nondeductible Expense Other IncomeTaxReconciliationNondeductibleExpenseOther	7000	USD
CY2020	us-gaap	Income Tax Reconciliation Change In Enacted Tax Rate IncomeTaxReconciliationChangeInEnactedTaxRate	0	USD
CY2019	us-gaap	Income Tax Reconciliation Change In Enacted Tax Rate IncomeTaxReconciliationChangeInEnactedTaxRate	0	USD
CY2018	us-gaap	Income Tax Reconciliation Change In Enacted Tax Rate IncomeTaxReconciliationChangeInEnactedTaxRate	-445000	USD
CY2020	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	167000	USD
CY2019	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	132000	USD
CY2018	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	-174000	USD
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	4607000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	3434000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	4009000	USD
CY2020	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.193
CY2019	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.180
CY2018	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.170
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Provision For Loan Losses DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsProvisionForLoanLosses	5393000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Provision For Loan Losses DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsProvisionForLoanLosses	6046000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Employee Benefits DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeBenefits	47000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Employee Benefits DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeBenefits	92000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Property Plant And Equipment DeferredTaxAssetsPropertyPlantAndEquipment	681000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Property Plant And Equipment DeferredTaxAssetsPropertyPlantAndEquipment	379000	USD
CY2020Q4	chmg	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Directors Compensation DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsDirectorsCompensation	1045000	USD
CY2019Q4	chmg	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Directors Compensation DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsDirectorsCompensation	765000	USD
CY2020Q4	chmg	Deferred Tax Assets Operating Lease Liabilities DeferredTaxAssetsOperatingLeaseLiabilities	1831000	USD
CY2019Q4	chmg	Deferred Tax Assets Operating Lease Liabilities DeferredTaxAssetsOperatingLeaseLiabilities	2050000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Deferred Expense Deferred Financing Costs DeferredTaxLiabilitiesDeferredExpenseDeferredFinancingCosts	274000	USD
CY2020Q4	chmg	Deferred Tax Assets Purchase Accounting Adjustment Loans DeferredTaxAssetsPurchaseAccountingAdjustmentLoans	1000	USD
CY2019Q4	chmg	Deferred Tax Assets Purchase Accounting Adjustment Loans DeferredTaxAssetsPurchaseAccountingAdjustmentLoans	1000	USD
CY2020Q4	chmg	Deferred Tax Assets Purchase Accounting Adjustment Fixed Assets DeferredTaxAssetsPurchaseAccountingAdjustmentFixedAssets	149000	USD
CY2019Q4	chmg	Deferred Tax Assets Purchase Accounting Adjustment Fixed Assets DeferredTaxAssetsPurchaseAccountingAdjustmentFixedAssets	149000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Investments DeferredTaxAssetsInvestments	54000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Investments DeferredTaxAssetsInvestments	71000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Other DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsOther	2302000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Other DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsOther	2448000	USD
CY2020Q4	chmg	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Nonaccrued Interest DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsNonaccruedInterest	687000	USD
CY2019Q4	chmg	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Nonaccrued Interest DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsNonaccruedInterest	695000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Accrued Liabilities DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAccruedLiabilities	158000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Accrued Liabilities DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAccruedLiabilities	179000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	48000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	38000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	12396000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	12913000	USD
CY2020Q4	chmg	Deferred Tax Liabilities Net Unrealized Gains On Securities Available For Sale DeferredTaxLiabilitiesNetUnrealizedGainsOnSecuritiesAvailableForSale	3124000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Deferred Expense Deferred Financing Costs DeferredTaxLiabilitiesDeferredExpenseDeferredFinancingCosts	592000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Prepaid Expenses DeferredTaxLiabilitiesPrepaidExpenses	3344000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Prepaid Expenses DeferredTaxLiabilitiesPrepaidExpenses	3189000	USD
CY2019Q4	chmg	Deferred Tax Liabilities Net Unrealized Gains On Securities Available For Sale DeferredTaxLiabilitiesNetUnrealizedGainsOnSecuritiesAvailableForSale	468000	USD
CY2020Q4	chmg	Deferred Tax Liabilities Deferred Expense Discount Accretion DeferredTaxLiabilitiesDeferredExpenseDiscountAccretion	50000	USD
CY2019Q4	chmg	Deferred Tax Liabilities Deferred Expense Discount Accretion DeferredTaxLiabilitiesDeferredExpenseDiscountAccretion	24000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Goodwill And Intangible Assets Intangible Assets DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsIntangibleAssets	1353000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Goodwill And Intangible Assets Intangible Assets DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsIntangibleAssets	1213000	USD
CY2020Q4	chmg	Deferred Tax Liabilities Reit Dividend DeferredTaxLiabilitiesREITDividend	616000	USD
CY2019Q4	chmg	Deferred Tax Liabilities Reit Dividend DeferredTaxLiabilitiesREITDividend	922000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Leasing Arrangements DeferredTaxLiabilitiesLeasingArrangements	1831000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Leasing Arrangements DeferredTaxLiabilitiesLeasingArrangements	2050000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	168000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	103000	USD
CY2020Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	10760000	USD
CY2019Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	8561000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	1636000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	4352000	USD
CY2019Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	0	USD
CY2020Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	0	USD
CY2018Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	0	USD
CY2018Q4	us-gaap	Unrecognized Tax Benefits Interest On Income Taxes Accrued UnrecognizedTaxBenefitsInterestOnIncomeTaxesAccrued	0	USD
CY2019Q4	us-gaap	Unrecognized Tax Benefits Interest On Income Taxes Accrued UnrecognizedTaxBenefitsInterestOnIncomeTaxesAccrued	0	USD
CY2020Q4	us-gaap	Unrecognized Tax Benefits Interest On Income Taxes Accrued UnrecognizedTaxBenefitsInterestOnIncomeTaxesAccrued	0	USD
CY2020	us-gaap	Defined Benefit Plan Service Cost DefinedBenefitPlanServiceCost	0	USD
CY2019	us-gaap	Defined Benefit Plan Service Cost DefinedBenefitPlanServiceCost	0	USD
CY2020	us-gaap	Defined Benefit Plan Curtailments DefinedBenefitPlanCurtailments	0	USD
CY2019	us-gaap	Defined Benefit Plan Curtailments DefinedBenefitPlanCurtailments	0	USD
CY2020	chmg	Total Unrecognized Net Loss Increased Percentage Of Obligation Amortization Threshold TotalUnrecognizedNetLossIncreasedPercentageOfObligationAmortizationThreshold	0.10
CY2016Q4	chmg	Defined Contribution Plan Number Of Annual Service Hours For Eligibility DefinedContributionPlanNumberOfAnnualServiceHoursForEligibility	PT1000H
CY2020	chmg	Total Unrecognized Net Loss Increased Percentage Of Obligation Amortization Threshold TotalUnrecognizedNetLossIncreasedPercentageOfObligationAmortizationThreshold	0.10
CY2019Q4	us-gaap	Related Party Deposit Liabilities RelatedPartyDepositLiabilities	18300000	USD
CY2019Q4	us-gaap	Notes Receivable Related Parties NotesReceivableRelatedParties	59973000	USD
CY2018Q4	us-gaap	Notes Receivable Related Parties NotesReceivableRelatedParties	62741000	USD
CY2020	chmg	Financing Receivable Related Parties Additions FinancingReceivableRelatedPartiesAdditions	7461000	USD
CY2019	chmg	Financing Receivable Related Parties Additions FinancingReceivableRelatedPartiesAdditions	1895000	USD
CY2020	chmg	Financing Receivable Related Parties Effect Of Changes In Composition FinancingReceivableRelatedPartiesEffectOfChangesInComposition	0	USD
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CY2019	chmg	Financing Receivable Related Parties Proceeds FinancingReceivableRelatedPartiesProceeds	9119000	USD
CY2020Q4	us-gaap	Notes Receivable Related Parties NotesReceivableRelatedParties	56052000	USD
CY2019Q4	us-gaap	Notes Receivable Related Parties NotesReceivableRelatedParties	59973000	USD
CY2020Q4	us-gaap	Related Party Deposit Liabilities RelatedPartyDepositLiabilities	39500000	USD
CY2020Q4	us-gaap	Loss Contingency Accrual At Carrying Value LossContingencyAccrualAtCarryingValue	16100000	USD
CY2020	chmg	Net Profits Period For Accessing Dividends NetProfitsPeriodForAccessingDividends	P2Y
CY2020Q4	us-gaap	Statutory Accounting Practices Statutory Amount Available For Dividend Payments Without Regulatory Approval StatutoryAccountingPracticesStatutoryAmountAvailableForDividendPaymentsWithoutRegulatoryApproval	36100000	USD
CY2020Q4	us-gaap	Capital Capital	192960000	USD
CY2020Q4	us-gaap	Capital To Risk Weighted Assets CapitalToRiskWeightedAssets	0.1362
CY2020Q4	us-gaap	Tier One Risk Based Capital TierOneRiskBasedCapital	175216000	USD
CY2020Q4	us-gaap	Tier One Risk Based Capital To Risk Weighted Assets TierOneRiskBasedCapitalToRiskWeightedAssets	0.1237
CY2020Q4	chmg	Common Equity Tier One Risk Based Capital CommonEquityTierOneRiskBasedCapital	175216000	USD
CY2020Q4	chmg	Common Equity Tier One Risk Based Capital To Risk Weighted Assets CommonEquityTierOneRiskBasedCapitalToRiskWeightedAssets	0.1237
CY2020Q4	us-gaap	Tier One Leverage Capital TierOneLeverageCapital	175216000	USD
CY2020Q4	us-gaap	Tier One Leverage Capital To Average Assets TierOneLeverageCapitalToAverageAssets	0.0790
CY2019Q4	us-gaap	Capital Capital	182239000	USD
CY2019Q4	us-gaap	Capital To Risk Weighted Assets CapitalToRiskWeightedAssets	0.1398
CY2019Q4	us-gaap	Tier One Risk Based Capital TierOneRiskBasedCapital	165859000	USD
CY2019Q4	us-gaap	Tier One Risk Based Capital To Risk Weighted Assets TierOneRiskBasedCapitalToRiskWeightedAssets	0.1273
CY2019Q4	chmg	Common Equity Tier One Risk Based Capital CommonEquityTierOneRiskBasedCapital	165859000	USD
CY2019Q4	chmg	Common Equity Tier One Risk Based Capital To Risk Weighted Assets CommonEquityTierOneRiskBasedCapitalToRiskWeightedAssets	0.1273
CY2019Q4	us-gaap	Tier One Leverage Capital TierOneLeverageCapital	165859000	USD
CY2019Q4	us-gaap	Tier One Leverage Capital To Average Assets TierOneLeverageCapitalToAverageAssets	0.0935
CY2020	us-gaap	Oci Before Reclassifications Net Of Tax Attributable To Parent OciBeforeReclassificationsNetOfTaxAttributableToParent	8136000	USD
CY2020	us-gaap	Reclassification From Aoci Current Period Net Of Tax Attributable To Parent ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent	-64000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	8200000	USD
CY2019	us-gaap	Oci Before Reclassifications Net Of Tax Attributable To Parent OciBeforeReclassificationsNetOfTaxAttributableToParent	5561000	USD
CY2019	us-gaap	Reclassification From Aoci Current Period Net Of Tax Attributable To Parent ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent	-51000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	5612000	USD
CY2018	us-gaap	Oci Before Reclassifications Net Of Tax Attributable To Parent OciBeforeReclassificationsNetOfTaxAttributableToParent	-1559000	USD
CY2018	us-gaap	Reclassification From Aoci Current Period Net Of Tax Attributable To Parent ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent	-690000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-869000	USD
CY2020	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	2	segment
CY2020	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	66907000	USD
CY2020	us-gaap	Interest Expense InterestExpense	3988000	USD
CY2020	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	62919000	USD
CY2020	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	4239000	USD
CY2020	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	58680000	USD
CY2020	us-gaap	Noninterest Income NoninterestIncome	21124000	USD
CY2020	us-gaap	Other Expenses OtherExpenses	55935000	USD
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	23869000	USD
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	4607000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	19262000	USD
CY2020Q4	us-gaap	Assets Assets	2279451000	USD
CY2019	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	66932000	USD
CY2019	us-gaap	Interest Expense InterestExpense	6321000	USD
CY2019	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	60611000	USD
CY2019	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	5945000	USD
CY2019	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	54666000	USD
CY2019	us-gaap	Noninterest Income NoninterestIncome	20073000	USD
CY2019	us-gaap	Other Expenses OtherExpenses	55696000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	19043000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	3434000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	15609000	USD
CY2019Q4	us-gaap	Assets Assets	1787827000	USD
CY2018	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	64553000	USD
CY2018	us-gaap	Interest Expense InterestExpense	4073000	USD
CY2018	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	60480000	USD
CY2018	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	3153000	USD
CY2018	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	57327000	USD
CY2018	us-gaap	Noninterest Income NoninterestIncome	23074000	USD
CY2018	us-gaap	Other Expenses OtherExpenses	56766000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	23635000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	4009000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	19626000	USD
CY2018Q4	us-gaap	Assets Assets	1755343000	USD

Files In Submission

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$CHMG
Chemung Financial Corp Stock $chmg

2019 Q4 Form 10-K Financial Statement

#000076356321000045 Filed on March 24, 2021

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$CHMG Chemung Financial Corp Stock $chmg

2019 Q4 Form 10-K Financial Statement

#000076356321000045 Filed on March 24, 2021

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$CHMG
Chemung Financial Corp Stock $chmg