Parent-Only Financial Information - Condensed Statements of Cash Flows (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net income	$ 26,732	$ 24,071	$ 15,702	$ 5,427	$ 9,956	$ 12,817	$ 7,679	$ 12,018	$ 71,932	$ 42,470	$ 23,046
Net accretion of purchase accounting adjustments									(16,733)	(8,216)	(4,505)
Cash flows from financing activities:
Dividends paid									(29,564)	(19,286)	(12,616)
Purchase of treasury stock									(10,837)	0	(1,878)
Exercise of stock options									5,324	3,354	3,989
OceanFirst Financial Corp.
Cash flows from operating activities:
Net income									71,932	42,470	23,046
Decrease (increase) in advances to subsidiary Bank									15,262	(23,371)	3,838
Undistributed earnings of subsidiary Bank									(45,556)	(13,213)	(20,510)
Amortization of deferred costs on borrowings									262	121	0
Net accretion of purchase accounting adjustments									395	0	0
Change in other assets and other liabilities									4,076	607	(1,619)
Net cash provided by operating activities									46,371	6,614	4,755
Cash flows from investing activities:
Increase in ESOP loan receivable									(8,400)	0	0
Repayments on ESOP loan receivable									1,020	234	218
Cash consideration for acquisition, net of cash received									0	0	(19,274)
Net cash (used in) provided by investing activities									(7,380)	234	(19,056)
Cash flows from financing activities:
Net proceeds from issuance of subordinated notes									0	0	33,899
Dividends paid									(29,564)	(19,286)	(12,616)
Purchase of treasury stock									(10,837)	0	(1,878)
Exercise of stock options									5,324	3,354	3,989
Net cash (used in) provided by financing activities									(35,077)	(15,932)	23,394
Net (decrease) increase in cash and due from banks									3,914	(9,084)	9,093
Cash and due from banks at beginning of year				$ 16				$ 9,100	16	9,100	7
Cash and due from banks at end of year	$ 3,930				$ 16				$ 3,930	$ 16	$ 9,100