| Document and Entity Information | Oct. 15, 2021 |
| Document And Entity Information [Line Items] | |
| Entity Registrant Name | CNB FINANCIAL CORP/PA |
| Amendment Flag | false |
| Entity Central Index Key | 0000736772 |
| Document Type | 8-K |
| Document Period End Date | Oct. 15, 2021 |
| Entity Incorporation State Country Code | PA |
| Entity File Number | 001-39472 |
| 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 |
| Entity Emerging Growth Company | false |
| Common Stock [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | Common Stock, no par value |
| Trading Symbol | CCNE |
| Security Exchange Name | NASDAQ |
| Series A Preferred Stock [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | 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 |
