XML 50 R38.htm IDEA: XBRL DOCUMENT
v3.8.0.1

ACQUISITIONS, Summary of Loans Acquired (Details) - Merchants Bancshares, Inc. [Member] $ in Thousands | May 12, 2017 USD ($)
--- | ---
Summary of loans acquired [Abstract] |
Contractually required principal and interest at acquisition | $ 1,888,028
Contractual cash flows not expected to be collected | (20,138)
Expected cash flows at acquisition | 1,867,890
Interest component of expected cash flows | (379,733)
Fair value of acquired loans | 1,488,157
Acquired Impaired Loans [Member] |
Summary of loans acquired [Abstract] |
Contractually required principal and interest at acquisition | 15,454
Contractual cash flows not expected to be collected | (5,385)
Expected cash flows at acquisition | 10,069
Interest component of expected cash flows | (793)
Fair value of acquired loans | 9,276
Acquired Non-impaired Loans [Member] |
Summary of loans acquired [Abstract] |
Contractually required principal and interest at acquisition | 1,872,574
Contractual cash flows not expected to be collected | (14,753)
Expected cash flows at acquisition | 1,857,821
Interest component of expected cash flows | (378,940)
Fair value of acquired loans | $ 1,478,881

X
- Definition The acquirer's estimate, at acquisition, of the amount and timing of undiscounted principal, interest, and other cash flows not expected to be collected. + References No definition available. + Details
Name: | cbu_CertainLoansAcquiredInTransferAccountedForAsDebtSecuritiesAcquiredDuringPeriodContractualCashFlowsNotExpectedToBeCollected
Namespace Prefix: | cbu_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The investor's estimate, at acquisition, of the amount and timing of the interest component of expected cash flows for loans acquired in transfer not accounted for as debt securities. + References No definition available. + Details
Name: | cbu_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAcquiredDuringPeriodInterestComponentOfCashFlows
Namespace Prefix: | cbu_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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

X
- Definition Fair value at acquisition of acquired loans not accounted for as debt securities with evidence of deterioration of credit quality. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 30 -Section 15 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=82894507&loc=d3e13503-111538 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=82894903&loc=d3e15032-111544 + Details
Name: | us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAcquiredDuringPeriodAtAcquisitionAtFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of cash flows expected to be collected at acquisition of acquired loans not accounted for as debt securities with evidence of deterioration of credit quality. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=82894903&loc=d3e15032-111544 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 30 -Section 15 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=82894507&loc=d3e13503-111538 + Details
Name: | us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAcquiredDuringPeriodCashFlowsExpectedToBeCollectedAtAcquisition
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of contractually required payments receivable at acquisition of acquired loans not accounted for as debt securities with evidence of deterioration of credit quality. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=82894903&loc=d3e15032-111544 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 30 -Section 15 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=82894507&loc=d3e13503-111538 + Details
Name: | us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAcquiredDuringPeriodContractuallyRequiredPaymentsReceivableAtAcquisition
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_BusinessAcquisitionAxis=cbu_MerchantsBancsharesIncMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtSecurityAxis=cbu_AcquiredImpairedLoansMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtSecurityAxis=cbu_AcquiredNonImpairedLoansMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |