XML 35 R26.htm IDEA: XBRL DOCUMENT
v3.23.3

Securities - Additional Information (Details) | 3 Months Ended | 9 Months Ended |  |
--- | --- | --- | --- | ---
Sep. 30, 2023 USD ($) Securities | Sep. 30, 2023 USD ($) Securities | Jan. 01, 2023 USD ($) | Dec. 31, 2022 USD ($) Securities
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Debt securities held-to-maturity fair value | $ 334,625,000 | $ 334,625,000 |  | $ 353,901,000
Allowance for credit loss | 0 | 0 | $ 7,200,000 |
Other-than-temporary Impairment Loss, Debt Securities, Available-for-Sale | $ 0 | $ 0 |  |
Debt Securities, Available-for-Sale, Unrealized Loss Position, Number of Positions | Securities | 591 | 591 |  | 611
US Treasury Securities [Member] | AA or Better [Member] |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Debt Securities, Percent | 100.00% | 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 | $ 153,597,000 | $ 153,597,000 |  | $ 162,536,000
US States and Political Subdivisions Debt Securities [Member] | A Rated [Member] |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Debt Securities, Percent | 11.00% | 11.00% |  |
US States and Political Subdivisions Debt Securities [Member] | AA or Better [Member] |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Debt Securities, Percent | 86.00% | 86.00% |  |
US States and Political Subdivisions Debt Securities [Member] | Unrated [Member] |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Debt Securities, Percent | 3.00% | 3.00% |  |
Collateralized Mortgage-Backed Securities [Member] |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Debt securities held-to-maturity fair value | $ 160,946,000 | $ 160,946,000 |  | $ 170,605,000
Collateralized Mortgage-Backed Securities [Member] | AA [Member] |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Debt Securities, Percent | 38.00% | 38.00% |  |
Collateralized Mortgage-Backed Securities [Member] | AAA [Member] |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Debt Securities, Percent | 39.00% | 39.00% |  |
Collateralized Mortgage-Backed Securities [Member] | Unrated [Member] |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Debt Securities, Percent | 23.00% | 23.00% |  |

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 Number of investments in debt securities measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position, without allowance for credit loss. Includes beneficial interest in securitized financial asset. + References Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (b)(3) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481800/320-10-50-6 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Subparagraph (b)(3) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479106/326-30-50-4 + Details
Name: | us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionNumberOfPositions
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(4)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name Regulation S-K (SK) -Number 229 -Section 1405 -Paragraph (a) -Subparagraph (1) -Publisher SEC Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Name Regulation S-K (SK) -Number 229 -Section 1405 -Paragraph (a) -Subparagraph (3) -Publisher SEC Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Name Regulation S-K (SK) -Number 229 -Section 1405 -Paragraph (c) -Publisher SEC Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479344/326-20-45-1 Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 942 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(7)(2)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479853/942-210-S99-1 Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 11B -Subparagraph (c)(1) -SubTopic 10 -Topic 310 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481962/310-10-50-11B Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 13 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-13 Reference 9: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 13 -Subparagraph (f) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-13 + Details
Name: | us-gaap_FinancingReceivableAllowanceForCreditLosses
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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 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//1943274/2147479440/944-210-S99-1 Reference 2: 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 3: 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//1943274/2147479853/942-210-S99-1 Reference 4: 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 + Details
Name: | us-gaap_HeldToMaturitySecuritiesFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of other-than-temporary impairment (OTTI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), recognized in earnings and other comprehensive loss (OCI). + References Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 8A -Publisher FASB -URI https://asc.fasb.org//1943274/2147481830/320-10-45-8A + Details
Name: | us-gaap_OtherThanTemporaryImpairmentLossDebtSecuritiesAvailableForSale
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 No definition available. + 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: |