XML 16 R4.htm IDEA: XBRL DOCUMENT
v3.10.0.1

CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2018 | Jun. 30, 2017 | Jun. 30, 2018 | Jun. 30, 2017
Interest and dividend income: |  |  |  |
Loans, including fees | $ 14,300 | $ 12,817 | $ 28,350 | $ 25,316
Taxable securities | 1,264 | 1,398 | 2,553 | 2,820
Tax exempt securities | 295 | 276 | 603 | 514
Interest-earning deposits | 10 | 193 | 32 | 348
Total interest and dividend income | 15,869 | 14,684 | 31,538 | 28,998
Interest expense: |  |  |  |
Deposits | 608 | 549 | 1,109 | 1,087
Securities sold under agreements to repurchase | 44 | 95 | 137 | 288
Borrowed funds | 200 | 90 | 375 | 179
Total interest expense | 852 | 734 | 1,621 | 1,554
Net interest income | 15,017 | 13,950 | 29,917 | 27,444
Provision for loan losses | 2,362 | 421 | 3,071 | 1,461
Net interest income after provision for loan losses | 12,655 | 13,529 | 26,846 | 25,983
Non-interest income: |  |  |  |
Financial services revenue | 59 | 53 | 105 | 122
Net gains (losses) on sales of other real estate owned | (48) | (9) | (4) | 8
Income from bank-owned life insurance | 17 | 18 | 33 | 35
Other | 784 | 490 | 1,638 | 1,021
Total non-interest income | 5,325 | 5,022 | 10,800 | 9,869
Non-interest expenses: |  |  |  |
Salaries and wages | 5,564 | 5,422 | 11,278 | 10,697
Pension and other employee benefits | 1,518 | 1,540 | 3,176 | 3,091
Other components of net periodic pension and postretirement benefits | (408) | (333) | (816) | (666)
Net occupancy expenses | 1,643 | 1,702 | 3,251 | 3,308
Furniture and equipment expenses | 702 | 781 | 1,360 | 1,462
Data processing expense | 1,764 | 1,587 | 3,506 | 3,191
Professional services | 508 | 417 | 1,048 | 717
Legal accruals and settlements | 989 | 850 | 989 | 850
Amortization of intangible assets | 182 | 213 | 376 | 439
Marketing and advertising expenses | 255 | 118 | 604 | 367
Other real estate owned expenses | 100 | 11 | 238 | 31
FDIC insurance | 301 | 309 | 618 | 634
Loan expense | 184 | 166 | 353 | 282
Other | 1,665 | 1,549 | 3,152 | 2,974
Total non-interest expenses | 14,967 | 14,332 | 29,133 | 27,377
Income before income tax expense | 3,013 | 4,219 | 8,513 | 8,475
Income tax expense | 486 | 1,263 | 1,547 | 2,540
Net income | $ 2,527 | $ 2,956 | $ 6,966 | $ 5,935
Weighted average shares outstanding (in shares) | 4,828 | 4,797 | 4,825 | 4,793
Basic and diluted earnings per share (in dollars per share) | $ 0.52 | $ 0.62 | $ 1.44 | $ 1.24
WMG fee income |  |  |  |
Non-interest income: |  |  |  |
Revenue from contract with customer, including assessed tax | $ 2,373 | $ 2,269 | $ 4,689 | $ 4,378
Service charge on deposits |  |  |  |
Non-interest income: |  |  |  |
Revenue from contract with customer, including assessed tax | 1,144 | 1,225 | 2,308 | 2,409
Interchange revenue from debit card transactions |  |  |  |
Non-interest income: |  |  |  |
Revenue from contract with customer, including assessed tax | 996 | 964 | 2,031 | 1,884
Sale of securities |  |  |  |
Non-interest income: |  |  |  |
Revenue from contract with customer, including assessed tax | 0 | 12 | 0 | 12
Financial services revenue |  | 12 |  | 12
Net gains on sales of loans |  |  |  |
Non-interest income: |  |  |  |
Financial services revenue | 59 | 53 | 105 | 122
Net gains (losses) on sales of OREO |  |  |  |
Non-interest income: |  |  |  |
Net gains (losses) on sales of other real estate owned | (48) | (9) | (4) | 8
Core Banking |  |  |  |
Non-interest income: |  |  |  |
Total non-interest income | 2,822 | 2,634 | 6,005 | 5,239
Core Banking | WMG fee income |  |  |  |
Non-interest income: |  |  |  |
Revenue from contract with customer, including assessed tax | 0 | 0 | 0 | 0
Core Banking | Interchange revenue from debit card transactions |  |  |  |
Non-interest income: |  |  |  |
Revenue from contract with customer, including assessed tax | 996 | 964 | 2,031 | 1,884
Core Banking | Sale of securities |  |  |  |
Non-interest income: |  |  |  |
Financial services revenue |  | 12 |  | 12
Core Banking | Net gains on sales of loans |  |  |  |
Non-interest income: |  |  |  |
Financial services revenue | 59 | 53 | 105 | 122
Core Banking | Net gains (losses) on sales of OREO |  |  |  |
Non-interest income: |  |  |  |
Net gains (losses) on sales of other real estate owned | $ (48) | $ (9) | $ (4) | $ 8

X
- Definition Net Periodic Defined Benefits Expense (Reversal Of Expense), Excluding Service Cost Component + References No definition available. + Details
Name: | chmg_NetPeriodicDefinedBenefitsExpenseReversalOfExpenseExcludingServiceCostComponent
Namespace Prefix: | chmg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Expenditures for salaries, incentive and share based compensation. + References No definition available. + Details
Name: | chmg_SalariesAndIncentiveCompensation
Namespace Prefix: | chmg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6388964&loc=d3e16225-109274 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275 + Details
Name: | us-gaap_AmortizationOfIntangibleAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Earnings on or other increases in the value of the cash surrender value of bank owned life insurance policies. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.13) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 + Details
Name: | us-gaap_BankOwnedLifeInsuranceIncome
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The amount of net income or loss for the period per each share in instances when basic and diluted earnings per share are the same amount and reported as a single line item on the face of the financial statements. Basic earnings per share is the amount of net income or loss for the period per each share of common stock or unit outstanding during the reporting period. Diluted earnings per share includes the amount of net income or loss for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period. + References No definition available. + Details
Name: | us-gaap_EarningsPerShareBasicAndDiluted
Namespace Prefix: | us-gaap_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | duration

X
- Definition This element represents equipment expense including depreciation, repairs, rentals, and service contract costs. This item also includes equipment purchases which do not qualify for capitalization in accordance with the entity's accounting policy. This item may also include furniture expenses. + References No definition available. + Details
Name: | us-gaap_EquipmentExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of expense for Federal Deposit Insurance Corporation (FDIC) insurance. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.14) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 + Details
Name: | us-gaap_FederalDepositInsuranceCorporationPremiumExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The aggregate financial services revenue and operating interest income earned during the reporting period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.1(d)) -URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688 + Details
Name: | us-gaap_FinancialServicesRevenue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of expense recognized during the period for the foreclosure on real estate assets. + References No definition available. + Details
Name: | us-gaap_ForeclosedRealEstateExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The net gain (loss) resulting from sales and other disposals of other real estate owned, increases (decreases) in the valuation allowance for foreclosed real estate, and write-downs of other real estate owned after acquisition or physical possession. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.14(d)) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 + Details
Name: | us-gaap_GainsLossesOnSalesOfOtherRealEstate
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of income (loss) from continuing operations before deduction of income tax expense (benefit) and income (loss) attributable to noncontrolling interest, and addition of income (loss) from equity method investments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(h)(1)(i)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 + Details
Name: | us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (a),(b) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32639-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(h)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 + Details
Name: | us-gaap_IncomeTaxExpenseBenefit
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The amount of expenses incurred in the period for information technology and data processing products and services. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.6) -URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688 + Details
Name: | us-gaap_InformationTechnologyAndDataProcessing
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Represents the total of interest and dividend income, including any amortization and accretion (as applicable) of discounts and premiums, earned from (1) loans and leases whether held-for-sale or held-in-portfolio; (2) investment securities; (3) federal funds sold; (4) securities purchased under agreements to resell; (5) investments in banker's acceptances, commercial paper, or certificates of deposit; (6) dividend income; or (7) other investments not otherwise specified herein. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.1-5) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 + Details
Name: | us-gaap_InterestAndDividendIncomeOperating
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_InterestAndDividendIncomeOperatingAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The aggregate interest and fee income generated by: (1) loans the Entity has positive intent and ability to hold for the foreseeable future, or until maturity or payoff, including commercial and consumer loans, whether domestic or foreign, which may consist of: (a) industrial and agricultural; (b) real estate; and (c) real estate construction loans; (d) trade financing; (e) lease financing; (f) home equity lines-of-credit; (g) automobile and other vehicle loans; and (h) credit card and other revolving-type loans and (2) loans and leases held-for-sale which may include mortgage loans, direct financing, and sales-type leases. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.1) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 + Details
Name: | us-gaap_InterestAndFeeIncomeLoansAndLeases
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of the cost of borrowed funds accounted for as interest expense. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6450988&loc=d3e26243-108391 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28555-108399 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.9) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 + Details
Name: | us-gaap_InterestExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_InterestExpenseAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Aggregate amount of interest expense on all borrowings. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.7,8) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 + Details
Name: | us-gaap_InterestExpenseBorrowings
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Aggregate amount of interest expense on all deposits. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.6) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 + Details
Name: | us-gaap_InterestExpenseDeposits
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Gross expenses on securities sold coupled with an agreement to repurchase the same from the same counterparty at a fixed or determinable price within a fixed or variable time period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.7) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 + Details
Name: | us-gaap_InterestExpenseSecuritiesSoldUnderAgreementsToRepurchase
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Interest income derived from funds deposited with both domestic and foreign financial institutions including funds in money market and other accounts. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.4) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 + Details
Name: | us-gaap_InterestIncomeDepositsWithFinancialInstitutions
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of interest income or expense, including any amortization and accretion (as applicable) of discounts and premiums, including consideration of the provisions for loan, lease, credit, and other related losses. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.12) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 + Details
Name: | us-gaap_InterestIncomeExpenseAfterProvisionForLoanLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The net amount of operating interest income (expense). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.10) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 + Details
Name: | us-gaap_InterestIncomeExpenseNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of operating interest income, including amortization and accretion of premiums and discounts, on securities exempt from state, federal and other income tax. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.2) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 + Details
Name: | us-gaap_InterestIncomeSecuritiesTaxExempt
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of operating interest income, including amortization and accretion of premiums and discounts, on securities subject to state, federal and other income tax. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.2) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 + Details
Name: | us-gaap_InterestIncomeSecuritiesTaxable
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of litigation expense, including but not limited to legal, forensic, accounting, and investigative fees. + References No definition available. + Details
Name: | us-gaap_LitigationSettlementExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The loan servicing fees paid to third parties that relate to loan expenses for a portfolio containing the entire group of loans owned by the company. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.3) -URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688 + Details
Name: | us-gaap_LoanPortfolioExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The total expense recognized in the period for promotion, public relations, and brand or product advertising. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.4) -URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688 + Details
Name: | us-gaap_MarketingAndAdvertisingExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The portion of profit or loss for the period, net of income taxes, which is attributable to the parent. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04(22)) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(18)) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03(20)) -URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688 + Details
Name: | us-gaap_NetIncomeLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Total aggregate amount of all noninterest expense. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.14) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 + Details
Name: | us-gaap_NoninterestExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_NoninterestExpenseAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The total amount of noninterest income which may be derived from: (1) fees and commissions; (2) premiums earned; (3) insurance policy charges; (4) the sale or disposal of assets; and (5) other sources not otherwise specified. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.13) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 + Details
Name: | us-gaap_NoninterestIncome
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_NoninterestIncomeAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of revenue earned, classified as other, excluding interest income. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04(13)) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-03(1)(e)) -URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20187-122688 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(4)) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 + Details
Name: | us-gaap_NoninterestIncomeOtherOperatingIncome
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of net occupancy expense that may include items, such as depreciation of facilities and equipment, lease expenses, property taxes and property and casualty insurance expense. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.14(b)) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.6) -URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 30 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=84164817&loc=d3e45280-112737 + Details
Name: | us-gaap_OccupancyNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of noninterest expense classified as other. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.14) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 + Details
Name: | us-gaap_OtherNoninterestExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of cost (reversal of cost) for pension and other postretirement benefits. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03(b)(4)) -URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03(b)(2)) -URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942 + Details
Name: | us-gaap_PensionAndOtherPostretirementBenefitExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition A fee charged for services from professionals such as doctors, lawyers and accountants. The term is often expanded to include other professions, for example, pharmacists charging to maintain a medicinal profile of a client or customer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.6-07.2(a),(b),(c),(d)) -URI http://asc.fasb.org/extlink&oid=6488393&loc=d3e606610-122999 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 225 -Section 45 -Paragraph 3 -Subparagraph (k) -URI http://asc.fasb.org/extlink&oid=6488370&loc=d3e13550-115849 + Details
Name: | us-gaap_ProfessionalFees
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of expense related to estimated loss from loan and lease transactions. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.11) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524 + Details
Name: | us-gaap_ProvisionForLoanAndLeaseLosses
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount, including tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value-added and excise. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 32 -Paragraph 2A -URI http://asc.fasb.org/extlink&oid=82859839&loc=SL82860478-203043 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=82913847&loc=SL49130539-203045 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=82913847&loc=SL49130543-203045 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=82913847&loc=SL49130545-203045 + Details
Name: | us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Average number of shares or units issued and outstanding that are used in calculating basic and diluted earnings per share (EPS). + References No definition available. + Details
Name: | us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_ProductOrServiceAxis=chmg_WealthManagementGroupServicesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ProductOrServiceAxis=chmg_ServiceChargeOnDepositsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ProductOrServiceAxis=chmg_InterchangeRevenueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ProductOrServiceAxis=chmg_SaleOfSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ProductOrServiceAxis=chmg_SaleOfLoansMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ProductOrServiceAxis=chmg_SaleOfOREOMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=chmg_CoreBankingMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |