Note 8 - Credit Quality of Financing Receivables (Details Textual)	12 Months Ended
Jun. 30, 2017
Number of Days Past Due on Lease or Loan Payments Minimum	90 days

Minimum number of days customer is past due on its lease or loan payments, causing the accrual of interest income to be discontinued.

No definition available.

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Namespace Prefix:	cfnb_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration