Cover - shares	3 Months Ended
	Mar. 31, 2021	May 03, 2021
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2021
Document Transition Report	false
Entity File Number	000-13396
Entity Incorporation, State or Country Code	PA
Entity Tax Identification Number	25-1450605
Entity Address, Address Line One	1 South Second Street
Entity Address, Address Line Two	P.O. Box 42
Entity Address, City or Town	Clearfield
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	16830
City Area Code	814
Local Phone Number	765-9621
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)		16,884,584
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Entity Registrant Name	CNB FINANCIAL CORP/PA
Entity Central Index Key	0000736772
Current Fiscal Year End Date	--12-31
Common Stock
Document Information [Line Items]
Title of 12(b) Security	Common Stock, no par value
Trading Symbol	CCNE
Security Exchange Name	NASDAQ
Series A Preferred Stock
Document Information [Line Items]
Title of 12(b) Security	Depositary Shares (each representing a 1/40th interest in a share of 7.125% Series A Non-Cumulative, perpetual preferred stock)
Trading Symbol	CCNEP
Security Exchange Name	NASDAQ