Note 4 - Fair Value - Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Jun. 30, 2023
Held-to-maturity, fair value	$ 6,123	$ 6,294
Fair Value, Inputs, Level 1 [Member] \| Reported Value Measurement [Member]
Cash and cash equivalents	19,643	11,755
Fair Value, Inputs, Level 1 [Member] \| Estimate of Fair Value Measurement [Member]
Cash and cash equivalents	19,643	11,755
Fair Value, Inputs, Level 2 [Member] \| Reported Value Measurement [Member]
Certificates of deposit in other financial institutions	2,493	2,501
Loans held for sale	0	764
Accrued interest receivable	3,293	3,024
Short-term borrowings	21,945	26,367
Federal Home Loan Bank advances	8,146	8,776
Accrued interest payable	507	344
Fair Value, Inputs, Level 2 [Member] \| Reported Value Measurement [Member] \| Demand and Savings Deposits [Member]
Demand and savings deposits	730,910	738,190
Fair Value, Inputs, Level 2 [Member] \| Reported Value Measurement [Member] \| Time Deposits [Member]
Demand and savings deposits	230,464	214,343
Fair Value, Inputs, Level 2 [Member] \| Estimate of Fair Value Measurement [Member]
Certificates of deposit in other financial institutions	2,462	2,450
Loans held for sale	0	774
Accrued interest receivable	3,293	3,024
Short-term borrowings	21,945	26,367
Federal Home Loan Bank advances	6,913	7,678
Accrued interest payable	507	344
Fair Value, Inputs, Level 2 [Member] \| Estimate of Fair Value Measurement [Member] \| Demand and Savings Deposits [Member]
Demand and savings deposits	730,910	738,190
Fair Value, Inputs, Level 2 [Member] \| Estimate of Fair Value Measurement [Member] \| Time Deposits [Member]
Demand and savings deposits	229,325	211,856
Fair Value, Inputs, Level 3 [Member] \| Reported Value Measurement [Member]
Held-to-maturity, fair value	6,866	6,970
Loans, net	710,139	702,638
Fair Value, Inputs, Level 3 [Member] \| Estimate of Fair Value Measurement [Member]
Held-to-maturity, fair value	6,123	6,294
Loans, net	$ 652,758	$ 656,737

Fair value portion of accrued interest receivable.

No definition available.

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Namespace Prefix:	cbkm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value portion of certificates of deposits in other financial institutions.

+ References

No definition available.

+ Details

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Namespace Prefix:	cbkm_
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Balance Type:	debit
Period Type:	instant

- Definition

Fair value portion of accrued expenses.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.20)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

Fair value portion of deposit liabilities held by the entity, including, but not limited to, foreign and domestic, interest and noninterest bearing, demand deposits, saving deposits, negotiable orders of withdrawal (NOW) and time deposits.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Fair value portion of borrowing from Federal Home Loan Bank (FHLBank).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.13(3)(a))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479853/942-210-S99-1

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value portion of loans held-for-sale including, but not limited to, mortgage loans and finance receivables.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Publisher FASB
-URI https://asc.fasb.org//310-10/tableOfContent

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents the amount of short-term debt existing as of the balance sheet date.

+ References

No definition available.

+ Details

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Period Type:	instant

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