| Document and Entity Information | Dec. 22, 2020 |
| Cover [Abstract] | |
| Entity Registrant Name | PEAPACK GLADSTONE FINANCIAL CORP |
| Amendment Flag | false |
| Entity Central Index Key | 0001050743 |
| Document Type | 8-K |
| Document Period End Date | Dec. 22, 2020 |
| Entity Incorporation State Country Code | NJ |
| Entity File Number | 001-16197 |
| Entity Tax Identification Number | 22-3537895 |
| Entity Address, Address Line One | 500 Hills Drive |
| Entity Address, Address Line Two | Suite 300 |
| Entity Address, City or Town | Bedminster |
| Entity Address, State or Province | NJ |
| Entity Address, Postal Zip Code | 07921 |
| City Area Code | (908) |
| Local Phone Number | 234-0700 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common |
| Trading Symbol | PGC |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
