| Document and Entity Information | Jun. 25, 2021 |
| Entity Information [Line Items] | |
| Document Type | 8-K |
| Document Period End Date | Jun. 25, 2021 |
| Entity Registrant Name | OCEANFIRST FINANCIAL CORP. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-11713 |
| Entity Tax Identification Number | 22-3412577 |
| Entity Address, Address Line One | 110 West Front Street |
| Entity Address, City or Town | Red Bank |
| Entity Address, State or Province | NJ |
| Entity Address, Postal Zip Code | 07701 |
| City Area Code | 732 |
| Local Phone Number | 240-4500 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001004702 |
| Amendment Flag | false |
| Common Stock | |
| Entity Information [Line Items] | |
| Title of 12(b) Security | Common stock, $0.01 par value per share |
| Trading Symbol | OCFC |
| Security Exchange Name | NASDAQ |
| Series A Preferred Stock | |
| Entity Information [Line Items] | |
| Title of 12(b) Security | Depositary Shares (each representing a 1/40th interest in a share of 7.0% Series A Non-Cumulative, perpetual preferred stock) |
| Trading Symbol | OCFCP |
| Security Exchange Name | NASDAQ |
