Parent-Only Financial Information - Condensed Statements of Operations (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
Condensed Financial Statements, Captions [Line Items]
Other income	$ 8,748	$ 8,285	$ 8,883	$ 8,910	$ 6,745	$ 7,359	$ 6,973	$ 5,995
Interest expense - borrowings									$ 13,574	$ 7,275	$ 5,646
Operating expenses	37,794	37,503	42,470	38,508	26,434	27,580	28,527	29,481	186,337	126,520	102,852
Benefit for income taxes	(4,269)	(5,278)	(3,018)	(1,005)	(10,186)	(5,700)	(3,170)	(3,799)	(13,570)	(22,855)	(12,153)
Net income	$ 26,732	$ 24,071	$ 15,702	$ 5,427	$ 9,956	$ 12,817	$ 7,679	$ 12,018	71,932	42,470	23,046
OceanFirst Financial Corp.
Condensed Financial Statements, Captions [Line Items]
Dividend income - subsidiary Bank									32,000	32,000	4,000
Interest and dividend income - investment securities									63	63	62
Interest income - advances to subsidiary Bank									525	280	118
Interest income - ESOP loan receivable									321	321	322
Other income									15	0	0
Total income									32,924	32,664	4,502
Interest expense - borrowings									4,997	2,592	1,049
Operating expenses									2,397	1,788	1,697
Income before income taxes and undistributed earnings of subsidiary Bank									25,530	28,284	1,756
Benefit for income taxes									846	973	780
Income before undistributed earnings of subsidiary Bank									26,376	29,257	2,536
Undistributed earnings of subsidiary Bank									45,556	13,213	20,510
Net income									$ 71,932	$ 42,470	$ 23,046