| Document and Entity Information | Apr. 29, 2020 |
| Cover [Abstract] | |
| Entity Registrant Name | OCEANFIRST FINANCIAL CORP |
| Amendment Flag | false |
| Entity Central Index Key | 0001004702 |
| Document Type | 8-K |
| Document Period End Date | Apr. 29, 2020 |
| Entity Incorporation State 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 |
| Security 12b Title | Common Stock, $0.01 par value per share |
| Trading Symbol | OCFC |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
