Note 6 - Securities (Details) - Available-for-sale Securities - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost	$ 490,839	$ 508,682
Available-for-sale securities, gross unrealized holding gains	9,025	11,377
Available-for-sale securities, gross unrealized holding losses	(2,753)	(3,252)
Available-for-sale securities, fair value	497,111	516,807
US Government Agencies Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost	27,189	27,221
Available-for-sale securities, gross unrealized holding gains	39	38
Available-for-sale securities, gross unrealized holding losses	(357)	(583)
Available-for-sale securities, fair value	26,871	26,676
Obligations of States and Political Subdivisions, Tax-exempt [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost	115,908	120,086
Available-for-sale securities, gross unrealized holding gains	4,147	5,134
Available-for-sale securities, gross unrealized holding losses	(306)	(381)
Available-for-sale securities, fair value	119,749	124,839
Obligations of States and Political Subdivisions, Taxable [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost	34,872	33,637
Available-for-sale securities, gross unrealized holding gains	394	415
Available-for-sale securities, gross unrealized holding losses	(131)	(174)
Available-for-sale securities, fair value	35,135	33,878
Collateralized Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost	76,323	82,479
Available-for-sale securities, gross unrealized holding gains	754	1,493
Available-for-sale securities, gross unrealized holding losses	(287)	(69)
Available-for-sale securities, fair value	76,790	83,903
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost	231,148	239,620
Available-for-sale securities, gross unrealized holding gains	1,308	1,239
Available-for-sale securities, gross unrealized holding losses	(1,662)	(2,036)
Available-for-sale securities, fair value	230,794	238,823
Collateralized Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost	34	34
Available-for-sale securities, gross unrealized holding gains	0	0
Available-for-sale securities, gross unrealized holding losses	0	0
Available-for-sale securities, fair value	34	34
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost	485,474	503,077
Available-for-sale securities, gross unrealized holding gains	6,642	8,319
Available-for-sale securities, gross unrealized holding losses	(2,743)	(3,243)
Available-for-sale securities, fair value	489,373	508,153
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost	5,365	5,605
Available-for-sale securities, gross unrealized holding gains	2,383	3,058
Available-for-sale securities, gross unrealized holding losses	(10)	(9)
Available-for-sale securities, fair value	$ 7,738	$ 8,654

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=51813488&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 5

-Subparagraph (aa)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=49167202&loc=d3e26610-111562

+ Details

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

- Definition

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

+ Details

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

- Definition

Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

+ Details

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

- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.2)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

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

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=cznc_ObligationsOfStatesAndPoliticalSubdivisionsTaxExemptMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=cznc_ObligationsOfStatesAndPoliticalSubdivisionsTaxableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_MortgageBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_CollateralizedDebtObligationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_DebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_EquitySecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: