Cover - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Feb. 22, 2021	Jun. 30, 2020
Entity Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-11713
Entity Registrant Name	OceanFirst Financial Corp.
Entity Incorporation, State or Country Code	DE
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
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 1,037,577
Entity Common Stock, Shares Outstanding		59,915,803
Documents Incorporated by Reference	Portions of the Proxy Statement for the 2021 Annual Meeting of Stockholders, which will be filed with the Securities and Exchange Commission within 120 days from December 31, 2020, are incorporated by reference into Part III of this Form 10-K.
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Entity Central Index Key	0001004702
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
Depositary Shares
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