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v3.19.1

Quarterly Financial Data (Unaudited) (Details Narrative) | 1 Months Ended
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May 31, 2018 | May 31, 2017
Quarterly Financial Information Disclosure [Abstract] |  |
Stock dividend paid | 5.00% | 5.00%

X
- Definition The stock dividend paid, represented as a percentage. + References No definition available. + Details
Name: | cofs_StockDividendPaid
Namespace Prefix: | cofs_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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