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Note 8 - Derivative and Hedging Activities (Details Textual) $ in Billions | 6 Months Ended
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Jun. 30, 2022 USD ($)
Pay Floating Swap Agreement [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] |
Derivative, Number of Instruments Held, Total | 2
Derivative, Notional Amount | $ 0.2
Derivative, Fixed Coupon Rate | 2.41%
Pay Fixed Swap Agreement [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] |
Derivative, Number of Instruments Held, Total | 1
Derivative, Notional Amount | $ 0.2
Derivative, Fixed Coupon Rate | 2.75%
Derivative, Term of Contract (Year) | 8 years
Four SOFR Cap Agreements [Member] |
Derivative, Number of Instruments Held, Total | 4
Derivative, Notional Amount | $ 0.2
Derivative, Term of Contract (Year) | 8 years
Three SOFR Cap Agreement [Member] | Designated as Hedging Instrument [Member] | Fair Value Hedging [Member] |
Derivative, Notional Amount | $ 0.1
Derivative, Floor Interest Rate | 2.68%
One SOFR Cap Agreement [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] |
Derivative, Notional Amount | $ 0.1
Derivative, Floor Interest Rate | 2.68%

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- Definition Fixed coupon rate related to the derivative. + References No definition available. + Details
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Namespace Prefix: | cofs_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

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- Definition Floor rate on an interest rate derivative such as an interest rate floor or collar. If market rates falls below the floor rate, a payment or receipt is triggered on the contract. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

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- Definition Nominal or face amount used to calculate payment on derivative. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1B -URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5580258-113959 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (d) -URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5579245-113959 + Details
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- Definition The number of derivative instruments of a particular group held by the entity. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (d) -URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5579245-113959 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1B -URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5580258-113959 + Details
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Period Type: | instant

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- Definition Period the derivative contract is outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
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Balance Type: | na
Period Type: | duration

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- Details
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Namespace Prefix: |
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- Details
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- Details
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Data Type: | na
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- Details
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- Details
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- Details
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- Details
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- Details
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