SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, Allowance for Loan Losses (Details)	12 Months Ended
Dec. 31, 2020
Allowance for Loan Losses [Abstract]
Number of days past for loan to be considered impaired	90 days

The number of days past due before a loan is classified as impaired.

No definition available.

Name:	czfs_NumberOfDaysPastDueForLoanToBeConsideredImpaired
Namespace Prefix:	czfs_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration