XML 68 R58.htm IDEA: XBRL DOCUMENT
v3.25.0.1

Securities - Additional Information (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2024 | Dec. 31, 2023
Debt and Equity Securities, FV-NI [Line Items] |  |
Debt Securities, Held-to-Maturity, Fair Value, Total | $ 339,048 | $ 348,791
Allowance for credit loss | $ 0 | 0
US Treasury Securities [Member] | AA or Better [Member] |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Debt Securities, Percent | 100.00% |
US States and Political Subdivisions Debt Securities [Member] |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Debt Securities, Held-to-Maturity, Fair Value, Total | $ 165,038 | 165,892
US States and Political Subdivisions Debt Securities [Member] | A Rated [Member] |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Debt Securities, Percent | 10.00% |
US States and Political Subdivisions Debt Securities [Member] | AA or Better [Member] |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Debt Securities, Percent | 85.00% |
US States and Political Subdivisions Debt Securities [Member] | Unrated [Member] |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Debt Securities, Percent | 4.00% |
Collateralized Mortgage-Backed Securities [Member] |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Debt Securities, Held-to-Maturity, Fair Value, Total | $ 152,367 | $ 162,533
Collateralized Mortgage-Backed Securities [Member] | AA [Member] |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Debt Securities, Percent | 42.00% |
Collateralized Mortgage-Backed Securities [Member] | AAA [Member] |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Debt Securities, Percent | 44.00% |
Collateralized Mortgage-Backed Securities [Member] | Unrated [Member] |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Debt Securities, Percent | 14.00% |
Reclassified From Available-for-sale Securities [Member] |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
OCI, Debt Securities, Available-for-Sale, Transfer to Held-to-Maturity, Adjustment from AOCI for Amortization of Gain (Loss), after Tax | $ 2,700 |
Debt Securities, Held-to-Maturity, Fair Value, Total | 428,400 |
OCI, Debt Securities, Available-for-Sale, Transfer to Held-to-Maturity, Adjustment from AOCI Unamortized, After Tax | $ 2,000 |

X
- Definition Debt securities percent. + References No definition available. + Details
Name: | cofs_DebtSecuritiesPercent
Namespace Prefix: | cofs_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Amount, after tax, of adjustment from accumulated other comprehensive income (loss) stay unamortized on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale) from transfer to investment in debt security measured at amortized cost (held-to-maturity). + References No definition available. + Details
Name: | cofs_OciDebtSecuritiesAvailableforsaleTransferToHeldtomaturityAdjustmentFromAociUnamortizedAfterTax
Namespace Prefix: | cofs_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Provision expense on securities. + References No definition available. + Details
Name: | cofs_ProvisionExpenseOnSecurities
Namespace Prefix: | cofs_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Fair value of investment in debt security measured at amortized cost (held-to-maturity). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2E -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2E Reference 3: http://fasb.org/us-gaap/role/ref/otherTransitionRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Subparagraph (aa) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481800/320-10-50-5 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(1)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 5A -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481800/320-10-50-5A Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(6)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1 + Details
Name: | us-gaap_HeldToMaturitySecuritiesFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount, after tax, of adjustment from accumulated other comprehensive income (loss) for amortization of gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale) from transfer to investment in debt security measured at amortized cost (held-to-maturity). + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 35 -Paragraph 10B -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481889/320-10-35-10B Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 14A -Publisher FASB -URI https://asc.fasb.org/1943274/2147482790/220-10-45-14A + Details
Name: | us-gaap_OciDebtSecuritiesAvailableForSaleTransferToHeldToMaturityAdjustmentFromAociForAmortizationOfGainLossAfterTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 6B -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-6B + Details
Name: | us-gaap_ScheduleOfTradingSecuritiesAndOtherTradingAssetsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_USTreasurySecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExternalCreditRatingByGroupingAxis=cofs_AAOrBetterMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_USStatesAndPoliticalSubdivisionsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExternalCreditRatingByGroupingAxis=cofs_ARatedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExternalCreditRatingByGroupingAxis=cofs_UnratedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_MortgageBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExternalCreditRatingByGroupingAxis=cofs_AAMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExternalCreditRatingByGroupingAxis=cofs_AAAMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ReclassificationTypeAxis=cofs_ReclassifiedFromAvailableforsaleSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |