LOANS AND ALLOWANCE FOR LOAN LOSSES - Loan modifications (Details) - CARES Act Section 4013 Program For Loan Modifications	Dec. 31, 2022 USD ($) loan
Beginning Balance \| loan	1
Ending Balance \| loan	0
Beginning Balance \| $	$ 9,423,000
Ending Balance \| $	$ 9,423,000

The number loans not classified as TDRs that were modified in response to COVID-19 in accordance with Section 4013 of the CAREs Act and whose modifications were still active as of the reporting period.

No definition available.

Name:	fkys_NumberOfLoanModificationsApprovedAcrossLoanSegments
Namespace Prefix:	fkys_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant