XML 43 R36.htm IDEA: XBRL DOCUMENT
v2.4.0.8

ACCOUNTING POLICIES (Details) (USD $) In Millions, unless otherwise specified | 9 Months Ended
--- | ---
Sep. 30, 2014
Allowance for Loan Losses [Abstract] |
Threshold amount for specific loan losses of individual commercial loans | $ 0.5
Core Deposits and Customer Relationships [Member] | Minimum [Member] |
Finite-Lived Intangible Assets [Line Items] |
Intangible asset useful life (amortization period) | 7 years
Core Deposits and Customer Relationships [Member] | Maximum [Member] |
Finite-Lived Intangible Assets [Line Items] |
Intangible asset useful life (amortization period) | 20 years

X
- Definition The threshold amount of commercial loans which are individually evaluated for impairment. + References No definition available. + Details
Name: | cbu_ThresholdAmountOfIndividualCommercialLoansEvaluatedForImpairment
Namespace Prefix: | cbu_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_FiniteLivedIntangibleAssetsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
Name: | us-gaap_FiniteLivedIntangibleAssetUsefulLife
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_LoansAndLeasesReceivableNetReportedAmountAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration