XML 54 R42.htm IDEA: XBRL DOCUMENT
v3.10.0.1

LOANS AND ALLOWANCE FOR LOAN LOSSES - Allowances (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | ---
Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2018 | Sep. 30, 2017 | Dec. 31, 2017 | Sep. 30, 2018 | Dec. 31, 2017
Allowance for loan losses, by portfolio segment [Roll Forward] |  |  |  |  |  |  |
Beginning balance | $ 19,645 | $ 15,104 | $ 21,161 | $ 14,253 | $ 14,253 |  |
Charge-offs | (440) | (816) | (5,315) | (1,708) |  |  |
Recoveries | 130 | 117 | 418 | 399 |  |  |
Net recoveries (charge-offs) | (310) | (699) | (4,897) | (1,309) |  |  |
Provision | 300 | 1,289 | 3,371 | 2,750 |  |  |
Ending balance | 19,635 | 15,694 | 19,635 | 15,694 | 21,161 |  |
Ending allowance balance attributable to loans [Abstract] |  |  |  |  |  |  |
Individually evaluated for impairment |  |  |  |  |  | $ 2,209 | $ 5,937
Collectively evaluated for impairment |  |  |  |  |  | 17,426 | 15,195
Total ending allowance balance | 19,645 | 15,104 | 21,161 | 14,253 | 14,253 | 19,635 | 21,161
Loans [Abstract] |  |  |  |  |  |  |
Loans individually evaluated for impairment |  |  |  |  |  | 9,221 | 13,926
Loans collectively evaluated for impairment |  |  |  |  |  | 1,315,301 | 1,300,864
Total recorded investment in loans |  |  |  |  |  | 1,324,522 | 1,315,582
Loans acquired with deteriorated credit quality |  |  |  |  |  |  |
Allowance for loan losses, by portfolio segment [Roll Forward] |  |  |  |  |  |  |
Beginning balance |  |  | 29 |  |  |  |
Ending balance |  |  |  |  | 29 |  |
Ending allowance balance attributable to loans [Abstract] |  |  |  |  |  |  |
Total ending allowance balance |  |  | 29 |  | 29 |  | 29
Loans [Abstract] |  |  |  |  |  |  |
Total recorded investment in loans |  |  |  |  |  | 0 | 792
Commercial and Agricultural |  |  |  |  |  |  |
Allowance for loan losses, by portfolio segment [Roll Forward] |  |  |  |  |  |  |
Beginning balance | 4,969 | 1,883 | 6,976 | 1,589 | 1,589 |  |
Charge-offs | 0 | (89) | (3,644) | (96) |  |  |
Recoveries | 13 | 34 | 34 | 95 |  |  |
Net recoveries (charge-offs) | 13 | (55) | (3,610) | (1) |  |  |
Provision | 285 | 99 | 1,901 | 339 |  |  |
Ending balance | 5,267 | 1,927 | 5,267 | 1,927 | 6,976 |  |
Ending allowance balance attributable to loans [Abstract] |  |  |  |  |  |  |
Individually evaluated for impairment |  |  |  |  |  | 1,713 | 5,135
Collectively evaluated for impairment |  |  |  |  |  | 3,554 | 1,841
Total ending allowance balance | 4,969 | 1,883 | 6,976 | 1,589 | 1,589 | 5,267 | 6,976
Loans [Abstract] |  |  |  |  |  |  |
Loans individually evaluated for impairment |  |  |  |  |  | 2,181 | 6,133
Loans collectively evaluated for impairment |  |  |  |  |  | 190,777 | 193,443
Total recorded investment in loans |  |  |  |  |  | 192,958 | 199,576
Commercial and Agricultural | Loans acquired with deteriorated credit quality |  |  |  |  |  |  |
Allowance for loan losses, by portfolio segment [Roll Forward] |  |  |  |  |  |  |
Beginning balance |  |  | 0 |  |  |  |
Ending balance |  |  |  |  | 0 |  |
Ending allowance balance attributable to loans [Abstract] |  |  |  |  |  |  |
Total ending allowance balance |  |  | 0 |  | 0 |  | 0
Loans [Abstract] |  |  |  |  |  |  |
Total recorded investment in loans |  |  |  |  |  |  | 0
Commercial Mortgages |  |  |  |  |  |  |
Allowance for loan losses, by portfolio segment [Roll Forward] |  |  |  |  |  |  |
Beginning balance | 8,740 | 7,778 | 8,514 | 7,270 | 7,270 |  |
Charge-offs | 0 | (154) | (145) | (154) |  |  |
Recoveries | 0 | 1 | 2 | 4 |  |  |
Net recoveries (charge-offs) | 0 | (153) | (143) | (150) |  |  |
Provision | (91) | 758 | 278 | 1,263 |  |  |
Ending balance | 8,649 | 8,383 | 8,649 | 8,383 | 8,514 |  |
Ending allowance balance attributable to loans [Abstract] |  |  |  |  |  |  |
Individually evaluated for impairment |  |  |  |  |  | 496 | 802
Collectively evaluated for impairment |  |  |  |  |  | 8,153 | 7,683
Total ending allowance balance | 8,740 | 7,778 | 8,514 | 7,270 | 7,270 | 8,649 | 8,514
Loans [Abstract] |  |  |  |  |  |  |
Loans individually evaluated for impairment |  |  |  |  |  | 6,572 | 7,302
Loans collectively evaluated for impairment |  |  |  |  |  | 661,003 | 638,080
Total recorded investment in loans |  |  |  |  |  | 667,575 | 646,174
Commercial Mortgages | Loans acquired with deteriorated credit quality |  |  |  |  |  |  |
Allowance for loan losses, by portfolio segment [Roll Forward] |  |  |  |  |  |  |
Beginning balance |  |  | 29 |  |  |  |
Ending balance |  |  |  |  | 29 |  |
Ending allowance balance attributable to loans [Abstract] |  |  |  |  |  |  |
Total ending allowance balance |  |  | 29 |  | 29 |  | 29
Loans [Abstract] |  |  |  |  |  |  |
Total recorded investment in loans |  |  |  |  |  |  | 792
Residential mortgages |  |  |  |  |  |  |
Allowance for loan losses, by portfolio segment [Roll Forward] |  |  |  |  |  |  |
Beginning balance | 1,445 | 1,517 | 1,316 | 1,523 | 1,523 |  |
Charge-offs | (60) | (133) | (225) | (193) |  |  |
Recoveries | 0 | 0 | 5 | 30 |  |  |
Net recoveries (charge-offs) | (60) | (133) | (220) | (163) |  |  |
Provision | 11 | 12 | 300 | 36 |  |  |
Ending balance | 1,396 | 1,396 | 1,396 | 1,396 | 1,316 |  |
Ending allowance balance attributable to loans [Abstract] |  |  |  |  |  |  |
Individually evaluated for impairment |  |  |  |  |  | 0 | 0
Collectively evaluated for impairment |  |  |  |  |  | 1,396 | 1,316
Total ending allowance balance | 1,445 | 1,517 | 1,316 | 1,523 | 1,523 | 1,396 | 1,316
Loans [Abstract] |  |  |  |  |  |  |
Loans individually evaluated for impairment |  |  |  |  |  | 410 | 427
Loans collectively evaluated for impairment |  |  |  |  |  | 188,751 | 194,510
Total recorded investment in loans |  |  |  |  |  | 189,161 | 194,937
Residential mortgages | Loans acquired with deteriorated credit quality |  |  |  |  |  |  |
Allowance for loan losses, by portfolio segment [Roll Forward] |  |  |  |  |  |  |
Beginning balance |  |  | 0 |  |  |  |
Ending balance |  |  |  |  | 0 |  |
Ending allowance balance attributable to loans [Abstract] |  |  |  |  |  |  |
Total ending allowance balance |  |  | 0 |  | 0 |  | 0
Loans [Abstract] |  |  |  |  |  |  |
Total recorded investment in loans |  |  |  |  |  | 0 | 0
Consumer Loans |  |  |  |  |  |  |
Allowance for loan losses, by portfolio segment [Roll Forward] |  |  |  |  |  |  |
Beginning balance | 4,491 | 3,926 | 4,355 | 3,871 | 3,871 |  |
Charge-offs | (380) | (440) | (1,301) | (1,265) |  |  |
Recoveries | 117 | 82 | 377 | 270 |  |  |
Net recoveries (charge-offs) | (263) | (358) | (924) | (995) |  |  |
Provision | 95 | 420 | 892 | 1,112 |  |  |
Ending balance | 4,323 | 3,988 | 4,323 | 3,988 | 4,355 |  |
Ending allowance balance attributable to loans [Abstract] |  |  |  |  |  |  |
Individually evaluated for impairment |  |  |  |  |  | 0 | 0
Collectively evaluated for impairment |  |  |  |  |  | 4,323 | 4,355
Total ending allowance balance | $ 4,491 | $ 3,926 | 4,355 | $ 3,871 | 3,871 | 4,323 | 4,355
Loans [Abstract] |  |  |  |  |  |  |
Loans individually evaluated for impairment |  |  |  |  |  | 58 | 64
Loans collectively evaluated for impairment |  |  |  |  |  | 274,770 | 274,831
Total recorded investment in loans |  |  |  |  |  | $ 274,828 | 274,895
Consumer Loans | Loans acquired with deteriorated credit quality |  |  |  |  |  |  |
Allowance for loan losses, by portfolio segment [Roll Forward] |  |  |  |  |  |  |
Beginning balance |  |  | 0 |  |  |  |
Ending balance |  |  |  |  | 0 |  |
Ending allowance balance attributable to loans [Abstract] |  |  |  |  |  |  |
Total ending allowance balance |  |  | $ 0 |  | $ 0 |  | 0
Loans [Abstract] |  |  |  |  |  |  |
Total recorded investment in loans |  |  |  |  |  |  | $ 0

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

X
- Definition Amount of recovery of (write-downs of) financing receivables doubtful of collection. + References No definition available. + Details
Name: | chmg_FinancingReceivableAllowanceForCreditLossesNetChargeOff
Namespace Prefix: | chmg_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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

X
- Definition A valuation allowance for financing receivables that are expected to be uncollectible. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524 + Details
Name: | us-gaap_FinancingReceivableAllowanceForCreditLosses
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524 + Details
Name: | us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524 + Details
Name: | us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of recovery of financing receivables doubtful of collection that were previously charged off. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (c)(4) -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524 + Details
Name: | us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
Name: | us-gaap_FinancingReceivableAllowanceForCreditLossesRollForward
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of direct write-downs of financing receivables charged against the allowance. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524 + Details
Name: | us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The balance of financing receivables that were collectively evaluated for impairment. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524 + Details
Name: | us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The balance of financing receivables that were individually evaluated for impairment. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524 + Details
Name: | us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Net amount of the investment in a contractual right to receive money on demand or on fixed or determinable dates that is recognized as an asset in the creditor's statement of financial position. Examples include, but are not limited to, credit card receivables, notes receivable and receivables relating to lessor's rights to payments from leases other than operating leases that have been recorded as assets. Excludes trade accounts receivable with contractual maturity of one year or less and arose from the sale of goods or services. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.3) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_NotesReceivableNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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
- Details
Name: | us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityAxis=us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=chmg_CommercialAndAgriculturalPortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ResidentialPortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ConsumerPortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |