Fair Value Measurements, Quantitative Information (Details) - Appraised Collateral Values [Member] $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Impaired Loans [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Impaired Loans	$ 3,264	$ 3,243
Impaired Loans [Member] \| Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Holding period	0 months	6 months
Impaired Loans [Member] \| Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Holding period	12 months	12 months
Impaired Loans [Member] \| Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Holding period	11 months 14 days	11 months 19 days
Impaired Loans [Member] \| Discount for Time Since Appraisal [Member] \| Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Impaired loans, Measurement input	0	0
Impaired Loans [Member] \| Discount for Time Since Appraisal [Member] \| Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Impaired loans, Measurement input	1	1
Impaired Loans [Member] \| Discount for Time Since Appraisal [Member] \| Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Impaired loans, Measurement input	0.2183	0.2061
Impaired Loans [Member] \| Selling Costs [Member] \| Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Impaired loans, Measurement input	0.05	0.05
Impaired Loans [Member] \| Selling Costs [Member] \| Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Impaired loans, Measurement input	0.11	0.10
Impaired Loans [Member] \| Selling Costs [Member] \| Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Impaired loans, Measurement input	0.0940	0.0951
Other Real Estate Owned [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Impaired Loans	$ 1,527	$ 1,700
Other Real Estate Owned [Member] \| Discount for Time Since Appraisal [Member] \| Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Other real estate owned, Measurement input	0.20	0.20
Other Real Estate Owned [Member] \| Discount for Time Since Appraisal [Member] \| Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Other real estate owned, Measurement input	0.33	0.31
Other Real Estate Owned [Member] \| Discount for Time Since Appraisal [Member] \| Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Other real estate owned, Measurement input	0.3058	0.2867

Holding period, used as an input to measure fair value.

No definition available.

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Period Type:	duration

- Definition

Value of input used to measure investment in impaired loans at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

No definition available.

+ Details

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Namespace Prefix:	czfs_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Definition

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

+ Details

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Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

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Period Type:	duration

- Definition

Value of input used to measure real estate owned by financial institution by financial institution which is not directly related to its business.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

+ Details

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Balance Type:	na
Period Type:	instant

- Details

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- Details

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- Details

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- Details

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- Details

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