LOANS AND RELATED ALLOWANCE FOR CREDIT LOSSES, Impaired Financing Receivable (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021
Impaired Financing Receivable [Abstract]
Unpaid Principal Balance	$ 14,653
Impaired Financing Receivable, Recorded Investment [Abstract]
Recorded Investment With No Allowance	11,292
Recorded Investment With Allowance	677
Total Recorded Investment	11,969
Related Allowance	102
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Average Recorded Investment	13,040	$ 15,880
Interest Income Recognized	356	395
Interest Income Recognized Cash Basis	10	31
Real Estate Loans [Member] \| Mortgages [Member]
Impaired Financing Receivable [Abstract]
Unpaid Principal Balance	395
Impaired Financing Receivable, Recorded Investment [Abstract]
Recorded Investment With No Allowance	242
Recorded Investment With Allowance	39
Total Recorded Investment	281
Related Allowance	4
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Average Recorded Investment	421	682
Interest Income Recognized	12	16
Interest Income Recognized Cash Basis	0	0
Real Estate Loans [Member] \| Home Equity [Member]
Impaired Financing Receivable [Abstract]
Unpaid Principal Balance	71
Impaired Financing Receivable, Recorded Investment [Abstract]
Recorded Investment With No Allowance	39
Recorded Investment With Allowance	15
Total Recorded Investment	54
Related Allowance	0
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Average Recorded Investment	64	99
Interest Income Recognized	4	4
Interest Income Recognized Cash Basis	0	0
Real Estate Loans [Member] \| Commercial [Member]
Impaired Financing Receivable [Abstract]
Unpaid Principal Balance	6,655
Impaired Financing Receivable, Recorded Investment [Abstract]
Recorded Investment With No Allowance	5,314
Recorded Investment With Allowance	361
Total Recorded Investment	5,675
Related Allowance	57
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Average Recorded Investment	6,216	8,789
Interest Income Recognized	207	288
Interest Income Recognized Cash Basis	10	31
Real Estate Loans [Member] \| Agricultural [Member]
Impaired Financing Receivable [Abstract]
Unpaid Principal Balance	6,062
Impaired Financing Receivable, Recorded Investment [Abstract]
Recorded Investment With No Allowance	5,192
Recorded Investment With Allowance	188
Total Recorded Investment	5,380
Related Allowance	24
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Average Recorded Investment	5,540	4,562
Interest Income Recognized	126	82
Interest Income Recognized Cash Basis	0	0
Consumer [Member]
Impaired Financing Receivable [Abstract]
Unpaid Principal Balance	4
Impaired Financing Receivable, Recorded Investment [Abstract]
Recorded Investment With No Allowance	0
Recorded Investment With Allowance	4
Total Recorded Investment	4
Related Allowance	4
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Average Recorded Investment	1
Interest Income Recognized	0
Interest Income Recognized Cash Basis	0
Other Commercial Loans [Member]
Impaired Financing Receivable [Abstract]
Unpaid Principal Balance	797
Impaired Financing Receivable, Recorded Investment [Abstract]
Recorded Investment With No Allowance	32
Recorded Investment With Allowance	70
Total Recorded Investment	102
Related Allowance	13
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Average Recorded Investment	260	704
Interest Income Recognized	3	2
Interest Income Recognized Cash Basis	0	0
Other Agricultural Loans [Member]
Impaired Financing Receivable [Abstract]
Unpaid Principal Balance	669
Impaired Financing Receivable, Recorded Investment [Abstract]
Recorded Investment With No Allowance	473
Recorded Investment With Allowance	0
Total Recorded Investment	473
Related Allowance	0
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Average Recorded Investment	538	1,044
Interest Income Recognized	4	3
Interest Income Recognized Cash Basis	$ 0	$ 0

Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481962/310-10-50-15

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 17
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481962/310-10-50-17

+ Details

Name:	us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- References

No definition available.

+ Details

Name:	us-gaap_ImpairedFinancingReceivableAverageRecordedInvestmentAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of interest income recognized that the financing receivables (with related allowance for credit losses and without a related allowance for credit losses) were impaired.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481962/310-10-50-15

+ Details

Name:	us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of interest income recognized on a cash-basis method of accounting that the financing receivables (with related allowance for credit losses and without a related allowance for credit losses) were impaired.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(3)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481962/310-10-50-15

+ Details

Name:	us-gaap_ImpairedFinancingReceivableInterestIncomeCashBasisMethod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 14A
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481962/310-10-50-14A

+ Details

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

- References

No definition available.

+ Details

Name:	us-gaap_ImpairedFinancingReceivableRecordedInvestmentAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of allowance for credit losses related to recorded investment.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (a)(3)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481962/310-10-50-15

+ Details

Name:	us-gaap_ImpairedFinancingReceivableRelatedAllowance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of unpaid principal balance of impaired financing receivables with related allowance for credit losses and without related allowance for credit losses.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (a)(4)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481962/310-10-50-15

+ Details

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

- References

No definition available.

+ Details

Name:	us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalanceAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of investment in impaired financing receivables for which there is no related allowance for credit losses.

+ References

+ Details

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

- Definition

Amount of investment in impaired financing receivables for which there is a related allowance for credit losses.

+ References

+ Details

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

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=czfs_RealEstateLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ResidentialMortgageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_HomeEquityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_CommercialRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=czfs_AgriculturalMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ConsumerPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=czfs_OtherAgriculturalLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: