Name:	cnnb_FederalHomeLoanBankAdvancesDeferredPrepaymentPenalties
Namespace Prefix:	cnnb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount of Federal Home Loan Bank (FHLBank) advances to member financial institutions.

No definition available.

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

Par amount of advances made and reported by Federal Home Loan Bank (FHLBank) maturing in the next rolling twelve months following the latest balance sheet. For interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

No definition available.

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

Par amount of advances made and reported by Federal Home Loan Bank (FHLBank) maturing in the fourth rolling twelve months following the latest balance sheet. For interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

No definition available.

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

Par amount of advances made and reported by Federal Home Loan Bank (FHLBank) maturing in the third rolling twelve months following the latest balance sheet. For interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

No definition available.

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

Par amount of advances made and reported by Federal Home Loan Bank (FHLBank) maturing in the second rolling twelve months following the latest balance sheet. For interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

No definition available.

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

Par amount of advances made and reported by Federal Home Loan Bank (FHLBank).

No definition available.

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

- References

No definition available.