Note 14 - Fair Value - Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Jun. 30, 2023
Held-to-maturity, fair value	$ 5,530	$ 6,294
Reported Value Measurement [Member] \| Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents	17,723	11,755
Reported Value Measurement [Member] \| Fair Value, Inputs, Level 2 [Member]
Certificates of deposit in other financial institutions	0	2,501
Loans held for sale	908	764
Accrued interest receivable	3,560	3,024
Short-term borrowings	30,007	26,367
Federal Home Loan Bank advances	13,709	8,776
Accrued interest payable	915	344
Reported Value Measurement [Member] \| Fair Value, Inputs, Level 2 [Member] \| Demand and Savings Deposits [Member]
Deposits	718,653	738,190
Reported Value Measurement [Member] \| Fair Value, Inputs, Level 2 [Member] \| Time Deposits [Member]
Deposits	254,327	214,343
Reported Value Measurement [Member] \| Fair Value, Inputs, Level 3 [Member]
Held-to-maturity, fair value	6,054	6,970
Loans, net	751,184	702,638
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents	17,723	11,755
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 2 [Member]
Certificates of deposit in other financial institutions	0	2,450
Loans held for sale	920	774
Accrued interest receivable	3,560	3,024
Short-term borrowings	30,007	26,367
Federal Home Loan Bank advances	12,672	7,678
Accrued interest payable	915	344
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 2 [Member] \| Demand and Savings Deposits [Member]
Deposits	718,653	738,190
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 2 [Member] \| Time Deposits [Member]
Deposits	253,458	211,856
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 3 [Member]
Held-to-maturity, fair value	5,530	6,294
Loans, net	$ 714,205	$ 656,737

Fair value portion of accrued interest receivable.

No definition available.

Name:	cbkm_AccruedInterestReceivableFairValueDisclosure
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.

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

- Definition

Fair value portion of accrued expenses.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(20))
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Balance Type:	credit
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- 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

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

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Balance Type:	credit
Period Type:	instant

- Definition

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

+ References

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- 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
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-Name Accounting Standards Codification
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+ 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

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
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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://www.xbrl.org/2009/role/commonPracticeRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-10

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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

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

+ Details

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- Details

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