| Document and Entity Information | Aug. 13, 2019 |
| Cover [Abstract] | |
| Entity Registrant Name | CNB FINANCIAL CORP/PA |
| Trading Symbol | CCNE |
| Amendment Flag | false |
| Entity Central Index Key | 0000736772 |
| Document Type | 8-K |
| Document Period End Date | Aug. 13, 2019 |
| Entity Incorporation, State or Country Code | PA |
| Entity File Number | 000-13396 |
| Entity Tax Identification Number | 25-1450605 |
| Entity Address, Address Line One | 1 South Second Street |
| Entity Address, Address Line Two | PO 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 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, no par value |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
