Loans, Impaired Financing Receivable (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Impaired Financing Receivable [Abstract]
Unpaid Principal Balance	$ 27,293		$ 27,293		$ 20,127
Recorded Investment With No Allowance	20,628		20,628		15,031
Recorded Investment With Allowance	3,609		3,609		2,662
Total Recorded Investment	24,237		24,237		17,693
Related Allowance	442		442		487
Average Recorded Investment	24,057	$ 11,943	21,875	$ 12,556
Interest Income Recognized	217	92	568	297
Interest Income Recognized Cash Basis	27	2	57	5
Real Estate Loans [Member] \| Mortgages [Member]
Impaired Financing Receivable [Abstract]
Unpaid Principal Balance	865		865		953
Recorded Investment With No Allowance	280		280		570
Recorded Investment With Allowance	515		515		330
Total Recorded Investment	795		795		900
Related Allowance	17		17		22
Average Recorded Investment	741	607	874	486
Interest Income Recognized	3	1	9	10
Interest Income Recognized Cash Basis	0	0	0	0
Real Estate Loans [Member] \| Home Equity [Member]
Impaired Financing Receivable [Abstract]
Unpaid Principal Balance	69		69		57
Recorded Investment With No Allowance	16		16		0
Recorded Investment With Allowance	53		53		57
Total Recorded Investment	69		69		57
Related Allowance	9		9		10
Average Recorded Investment	70	58	62	59
Interest Income Recognized	1	1	3	3
Interest Income Recognized Cash Basis	0	0	0	0
Real Estate Loans [Member] \| Commercial [Member]
Impaired Financing Receivable [Abstract]
Unpaid Principal Balance	16,240		16,240		7,958
Recorded Investment With No Allowance	13,329		13,329		5,697
Recorded Investment With Allowance	430		430		45
Total Recorded Investment	13,759		13,759		5,742
Related Allowance	67		67		45
Average Recorded Investment	13,663	5,980	10,812	6,088
Interest Income Recognized	122	35	280	87
Interest Income Recognized Cash Basis	2	0	5	0
Real Estate Loans [Member] \| Agricultural [Member]
Impaired Financing Receivable [Abstract]
Unpaid Principal Balance	3,983		3,983		3,347
Recorded Investment With No Allowance	1,933		1,933		2,000
Recorded Investment With Allowance	2,031		2,031		1,347
Total Recorded Investment	3,964		3,964		3,347
Related Allowance	99		99		54
Average Recorded Investment	3,799	0	3,609	110
Interest Income Recognized	27	2	90	7
Interest Income Recognized Cash Basis	0	0	0	0
Real Estate Loans [Member] \| Construction [Member]
Impaired Financing Receivable [Abstract]
Unpaid Principal Balance	0		0		0
Recorded Investment With No Allowance	0		0		0
Recorded Investment With Allowance	0		0		0
Total Recorded Investment	0		0		0
Related Allowance	0		0		0
Average Recorded Investment	0	0	0	0
Interest Income Recognized	0	0	0	0
Interest Income Recognized Cash Basis	0	0	0	0
Consumer [Member]
Impaired Financing Receivable [Abstract]
Unpaid Principal Balance	4		4		0
Recorded Investment With No Allowance	2		2		0
Recorded Investment With Allowance	2		2		0
Total Recorded Investment	4		4		0
Related Allowance	2		2		0
Average Recorded Investment	4	0	2	0
Interest Income Recognized	0	0	0	0
Interest Income Recognized Cash Basis	0	0	0	0
Other Commercial Loans [Member]
Impaired Financing Receivable [Abstract]
Unpaid Principal Balance	4,690		4,690		6,159
Recorded Investment With No Allowance	3,759		3,759		5,135
Recorded Investment With Allowance	469		469		859
Total Recorded Investment	4,228		4,228		5,994
Related Allowance	208		208		326
Average Recorded Investment	4,337	5,298	4,988	5,743
Interest Income Recognized	54	53	131	187
Interest Income Recognized Cash Basis	25	2	52	5
Other Agricultural Loans [Member]
Impaired Financing Receivable [Abstract]
Unpaid Principal Balance	1,442		1,442		1,653
Recorded Investment With No Allowance	1,309		1,309		1,629
Recorded Investment With Allowance	109		109		24
Total Recorded Investment	1,418		1,418		1,653
Related Allowance	40		40		30
Average Recorded Investment	1,443	0	1,528	70
Interest Income Recognized	10	0	55	3
Interest Income Recognized Cash Basis	0	0	0	0
State and Political Subdivision Loans [Member]
Impaired Financing Receivable [Abstract]
Unpaid Principal Balance	0		0		0
Recorded Investment With No Allowance	0		0		0
Recorded Investment With Allowance	0		0		0
Total Recorded Investment	0		0		0
Related Allowance	0		0		$ 0
Average Recorded Investment	0	0	0	0
Interest Income Recognized	0	0	0	0
Interest Income Recognized Cash Basis	$ 0	$ 0	$ 0	$ 0

No definition available.

Name:	czfs_ImpairedFinancingReceivableAbstract
Namespace Prefix:	czfs_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Average 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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5212-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5258-111524

+ Details

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

+ 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

+ 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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 14A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953550-111524

+ Details

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

- Definition

Amount of allowance for credit losses related to recorded investment.

+ References

+ 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

+ Details

Name:	us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
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 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_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=czfs_ConstructionRealEstateLoansMember
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:

- Details

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