FAIR VALUE MEASUREMENTS AND FAIR VALUES OF FINANCIAL INSTRUMENTS - Financial Instruments Not Recorded at Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Interest rate swap agreements
Fair values, and carrying amounts financial instruments not recorded at fair value
Fair value derivative asset	$ 3,933	$ 6,566
Reported value measurement \| Level 1
Fair values, and carrying amounts financial instruments not recorded at fair value
Cash and cash equivalents	199,305	96,017
Reported value measurement \| Level 2
Fair values, and carrying amounts financial instruments not recorded at fair value
Certificates of deposit	7,840	5,840
Restricted equity securities (included in Other Assets)	9,859	9,970
Accrued interest receivable	7,913	8,293
Short-term borrowings	9,763	20,022
Long-term borrowings	50,467	54,608
Subordinated debt	16,534	16,553
Accrued interest payable	547	390
Reported value measurement \| Level 2 \| Deposits with no stated maturity
Fair values, and carrying amounts financial instruments not recorded at fair value
Deposits, fair value	1,576,759	1,430,062
Reported value measurement \| Level 2 \| Time deposits
Fair values, and carrying amounts financial instruments not recorded at fair value
Deposits, fair value	347,166	390,407
Reported value measurement \| Level 2 \| Interest rate swap agreements
Fair values, and carrying amounts financial instruments not recorded at fair value
Fair value derivative asset	3,933	6,566
Interest rate swap agreements	3,933	6,566
Reported value measurement \| Level 3
Fair values, and carrying amounts financial instruments not recorded at fair value
Loans, net	1,602,926	1,632,824
Estimate of fair value measurement \| Level 1
Fair values, and carrying amounts financial instruments not recorded at fair value
Cash and cash equivalents	199,305	96,017
Estimate of fair value measurement \| Level 2
Fair values, and carrying amounts financial instruments not recorded at fair value
Certificates of deposit	8,012	6,054
Restricted equity securities (included in Other Assets)	9,859	9,970
Accrued interest receivable	7,913	8,293
Short-term borrowings	9,600	19,974
Long-term borrowings	51,318	55,723
Subordinated debt	16,534	16,680
Accrued interest payable	547	390
Estimate of fair value measurement \| Level 2 \| Deposits with no stated maturity
Fair values, and carrying amounts financial instruments not recorded at fair value
Deposits, fair value	1,576,759	1,430,062
Estimate of fair value measurement \| Level 2 \| Time deposits
Fair values, and carrying amounts financial instruments not recorded at fair value
Deposits, fair value	349,693	393,566
Estimate of fair value measurement \| Level 2 \| Interest rate swap agreements
Fair values, and carrying amounts financial instruments not recorded at fair value
Fair value derivative asset	3,933	6,566
Interest rate swap agreements	3,933	6,566
Estimate of fair value measurement \| Level 3
Fair values, and carrying amounts financial instruments not recorded at fair value
Loans, net	$ 1,617,298	$ 1,646,207

Represents the fair value portion of accrued interest payable.

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The fair value of Interest, dividends, rents, ancillary and other revenues earned but not yet received by the entity on its investments.

+ References

No definition available.

+ Details

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Namespace Prefix:	cznc_
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Period Type:	instant

- Definition

The fair value disclosure of a savings certificate entitling the Entity (that is, bearer) to receive interest at an established maturity date, based upon a fixed interest rate. A certificate of deposit may be issued in any denomination. Certificates of deposit are generally issued by commercial banks and, therefore, insured by the FDIC (up to the prescribed limit). Certificates of deposit generally restrict holders from withdrawing funds on demand without the incurrence of penalties. Generally, only certificates of deposit with original maturities of three months or less qualify as cash equivalents. Original maturity means original maturity to the entity holding the investment. As a related example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three-years ago does not become a cash equivalent when its remaining maturity is three months.

+ References

No definition available.

+ Details

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Period Type:	instant

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents the amount of subordinated debt existing as of the balance sheet date.

+ References

No definition available.

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- Definition

Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

+ References

No definition available.

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- Definition

Fair value portion of deposit liabilities held by the entity, including, but not limited to, foreign and domestic, interest and noninterest bearing, demand deposits, saving deposits, negotiable orders of withdrawal (NOW) and time deposits.

+ References

No definition available.

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- Definition

Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

+ References

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

- Definition

Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

+ References

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+ Details

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

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-URI http://asc.fasb.org/subtopic&trid=2196772

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Balance Type:	debit
Period Type:	instant

- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

No definition available.

+ Details

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

- Definition

The aggregate value of all restricted investments.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 320
-Section S99
-Paragraph 1
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-URI http://asc.fasb.org/extlink&oid=120401592&loc=d3e611197-123010

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Balance Type:	debit
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- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents the amount of short-term debt existing as of the balance sheet date.

+ References

No definition available.

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