Parent-Only Financial Information - Condensed Statements of Financial Condition (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Assets
Cash and due from banks	$ 1,272,134	$ 120,544	$ 120,792	$ 109,613
Other assets	208,968	169,532
Total assets	11,448,313	8,246,145
Liabilities and Stockholders’ Equity
Borrowings	363,925	687,800
Other liabilities	155,346	62,565
Stockholders’ equity	1,484,130	1,153,119	$ 1,039,358	$ 601,941
Total liabilities and stockholders’ equity	11,448,313	8,246,145
OceanFirst Financial Corp.
Assets
Cash and due from banks	7,187	5,442
Advances to Bank	101,304	27,878
Investment securities	93,207	1,000
ESOP loan receivable	8,071	9,271
Investment in subsidiaries	1,502,867	1,206,479
Other assets	10,180	327
Total assets	1,722,816	1,250,397
Liabilities and Stockholders’ Equity
Borrowings	233,371	94,848
Other liabilities	5,315	2,430
Stockholders’ equity	1,484,130	1,153,119
Total liabilities and stockholders’ equity	$ 1,722,816	$ 1,250,397