Parent-Only Financial Information - Condensed Statements of Cash Flows (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Cash flows from operating activities:
Net income	$ 147,357,000	$ 110,076,000	$ 63,309,000
Net gain on equity investments	(358,000)	(3,186,000)	(8,278,000)
Net premium amortization in excess of discount accretion on securities	7,164,000	8,466,000	2,997,000
Amortization of deferred costs on borrowings	108,000	0
Net amortization of purchase accounting adjustments	(9,752,000)	(14,484,000)	(21,557,000)
Net cash provided by operating activities	250,450,000	159,972,000	132,656,000
Cash flows from investing activities:
Proceeds from sales of equity investments	19,234,000	98,777,000	16,978,000
Purchase of equity investments	(9,366,000)	(86,462,000)	(96,519,000)
Net cash used in investing activities	(1,321,008,000)	(1,477,842,000)	(22,169,000)
Cash flows from financing activities:
Net proceeds from issuance of subordinated notes	0	0	122,180,000
Repayments of other borrowings	(35,104,000)	(7,612,000)	(8,109,000)
Dividends paid	(47,511,000)	(44,510,000)	(42,917,000)
Purchase of treasury stock	(7,396,000)	(36,059,000)	(14,814,000)
Net proceeds from the issuance of preferred stock	0	0	55,529,000
Exercise of stock options	424,000	1,946,000	1,241,000
Distributions to non-controlling interest	(782,000)	0	0
Net cash provided by financing activities	1,013,760,000	223,993,000	1,074,948,000
Net (decrease) increase in cash and due from banks and restricted cash	(56,798,000)	(1,093,877,000)	1,185,435,000
Cash and due from banks at beginning of year	204,949,000	1,272,134,000	120,544,000
Cash and due from banks at end of year	167,946,000	204,949,000	1,272,134,000
OceanFirst Financial Corp.
Cash flows from operating activities:
Net income	147,357,000	110,076,000	63,309,000
Decrease (increase) in advances to subsidiary Bank	30,640,000	37,824,000	(73,426,000)
Undistributed earnings of subsidiary Bank	(77,357,000)	(73,311,000)	(4,071,000)
Net gain on equity investments	(7,973,000)	(7,499,000)	(20,460,000)
Net premium amortization in excess of discount accretion on securities	1,185,000	755,000	0
Amortization of deferred costs on borrowings	548,000	824,000	576,000
Net amortization of purchase accounting adjustments	684,000	542,000	638,000
Change in other assets and other liabilities	2,336,000	7,359,000	648,000
Net cash provided by operating activities	97,420,000	76,570,000	(32,786,000)
Cash flows from investing activities:
Proceeds from sales of equity investments	6,482,000	98,791,000	15,339,000
Purchase of equity investments	(7,207,000)	(86,462,000)	(95,228,000)
Increase in ESOP loan receivable	0	(3,200,000)	0
Repayments on ESOP loan receivable	2,480,000	2,040,000	1,200,000
Cash consideration for acquisition, net of cash received	(7,084,000)	0	0
Net cash used in investing activities	(5,329,000)	11,169,000	(78,689,000)
Cash flows from financing activities:
Net proceeds from issuance of subordinated notes	0	0	122,180,000
Repayments of other borrowings	(35,000,000)	(7,500,000)	(7,999,000)
Dividends paid	(47,511,000)	(44,510,000)	(42,917,000)
Purchase of treasury stock	(7,396,000)	(36,059,000)	(14,814,000)
Net proceeds from the issuance of preferred stock	0	0	55,529,000
Exercise of stock options	424,000	1,946,000	1,241,000
Distributions to non-controlling interest	(788,000)	0	0
Net cash provided by financing activities	(90,271,000)	(86,123,000)	113,220,000
Net (decrease) increase in cash and due from banks and restricted cash	1,820,000	1,616,000	1,745,000
Cash and due from banks at beginning of year	8,803,000	7,187,000	5,442,000
Cash and due from banks at end of year	$ 10,623,000	$ 8,803,000	$ 7,187,000