Note 2 - Securities (Details Textual) - USD ($) $ in Thousands	3 Months Ended
Sep. 30, 2017	Sep. 30, 2016
Available-for-sale Securities Income Tax Provision on Gross Realized Gains	$ 13	$ 35

This item represents the tax provision applicable to gross profit realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

No definition available.

Name:	cbkm_AvailableForSaleSecuritiesIncomeTaxProvisionOnGrossRealizedGains
Namespace Prefix:	cbkm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration