Loans - Restructured in Troubled Debt (Detail) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018 USD ($) loan	Sep. 30, 2017 USD ($) loan	Sep. 30, 2018 USD ($) loan	Sep. 30, 2017 USD ($) loan	Dec. 31, 2017 USD ($) loan
Financing Receivable, Modifications [Line Items]
Number of loans at a point in time \| loan	24		24		20
Number of loans, period of time \| loan	4	4	4	4
Loan Balance	$ 17,744		$ 17,744		$ 17,303
Specific Reserve	6,471		6,471		$ 5,689
Pre-Modification Outstanding Recorded Investment	1,091	$ 6,551	1,091	$ 6,551
Post-Modification Outstanding Recorded Investment	$ 1,091	$ 6,655	$ 1,091	$ 6,655
Commercial, Industrial, and Agricultural
Financing Receivable, Modifications [Line Items]
Number of loans at a point in time \| loan	11		11		11
Number of loans, period of time \| loan	0	2	0	2
Loan Balance	$ 4,798		$ 4,798		$ 5,213
Specific Reserve	237		237		$ 245
Pre-Modification Outstanding Recorded Investment	0	$ 324	0	$ 324
Post-Modification Outstanding Recorded Investment	$ 0	$ 379	$ 0	$ 379
Commercial mortgages
Financing Receivable, Modifications [Line Items]
Number of loans at a point in time \| loan	13		13		9
Number of loans, period of time \| loan	4	2	4	2
Loan Balance	$ 12,946		$ 12,946		$ 12,090
Specific Reserve	6,234		6,234		$ 5,444
Pre-Modification Outstanding Recorded Investment	1,091	$ 6,227	1,091	$ 6,227
Post-Modification Outstanding Recorded Investment	$ 1,091	$ 6,276	$ 1,091	$ 6,276
Residential Real Estate
Financing Receivable, Modifications [Line Items]
Number of loans at a point in time \| loan	0		0		0
Number of loans, period of time \| loan	0	0	0	0
Loan Balance	$ 0		$ 0		$ 0
Specific Reserve	0		0		$ 0
Pre-Modification Outstanding Recorded Investment	0	$ 0	0	$ 0
Post-Modification Outstanding Recorded Investment	$ 0	$ 0	$ 0	$ 0
Consumer
Financing Receivable, Modifications [Line Items]
Number of loans at a point in time \| loan	0		0		0
Number of loans, period of time \| loan	0	0	0	0
Loan Balance	$ 0		$ 0		$ 0
Specific Reserve	0		0		$ 0
Pre-Modification Outstanding Recorded Investment	0	$ 0	0	$ 0
Post-Modification Outstanding Recorded Investment	$ 0	$ 0	$ 0	$ 0
Credit Cards
Financing Receivable, Modifications [Line Items]
Number of loans at a point in time \| loan	0		0		0
Number of loans, period of time \| loan	0	0	0	0
Loan Balance	$ 0		$ 0		$ 0
Specific Reserve	0		0		$ 0
Pre-Modification Outstanding Recorded Investment	0	$ 0	0	$ 0
Post-Modification Outstanding Recorded Investment	$ 0	$ 0	$ 0	$ 0

Financing Receivable, Modifications, Number of Loans

No definition available.

Name:	ccne_FinancingReceivableModificationsNumberofLoans
Namespace Prefix:	ccne_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Financing receivable modifications specific reserve.

+ References

No definition available.

+ Details

Name:	ccne_FinancingReceivableModificationsSpecificReserve
Namespace Prefix:	ccne_
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

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

- Definition

Number of financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953676-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsNumberOfContracts2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Post-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Pre-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount of the outstanding recorded investment related to financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=82895541&loc=d3e18845-111554

+ Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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