Regulatory Matters - Summary of Regulatory Capital Amounts and Ratios (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 capital (to average assets), Actual Ratio				4.00%
Common equity Tier 1 (to risk-weighted assets), Actual Ratio				4.50%
Tier 1 capital (to risk-weighted assets), Actual Ratio				5.00%
Tier 1 capital (to average assets), For capital adequacy purposes Ratio				6.00%	4.00%
Total capital (to risk-weighted assets) For capital adequacy purposes Ratio				8.00%
Tier 1 capital (to average assets), To be well capitalized under prompt corrective action Ratio					5.00%
Common equity Tier 1 (to risk-weighted asset), To be well capitalized under prompt corrective action Ratio				6.50%
Tier 1 capital (to risk-weighted assets), To be well capitalized under prompt corrective action Ratio				8.00%
Total capital (to risk-weighted assets), To be well capitalized under prompt corrective action Ratio				10.00%
Capital conservation buffer (as a percent)				0.625%
Tier 1 capital ratio based on total assets (as a percent)				8.75%	8.85%
OceanFirst Bank
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 capital (to average assets), Actual Amount				$ 445,576,000	$ 229,306,000
Common equity Tier 1 (to risk-weighted asset), Actual Amount				445,576,000	229,306,000
Tier 1 capital (to risk-weighted assets), Actual Amount				445,576,000	229,306,000
Total capital (to risk-weighted assets), Actual Amount				$ 461,386,000	$ 246,106,000
Tier 1 capital (to average assets), Actual Ratio				10.08%	8.91%
Common equity Tier 1 (to risk-weighted assets), Actual Ratio				12.67%	12.72%
Tier 1 capital (to risk-weighted assets), Actual Ratio				12.67%	12.72%
Total capital (to risk-weighted assets), Actual Ratio				13.12%	13.65%
Tier 1 capital (to average assets), For capital adequacy purposes Amount				$ 176,856,400.0	$ 102,935,000
Common equity Tier 1 (to risk-weighted asset), For capital adequacy purposes Amount				180,178,087.5000	81,114,000
Tier 1 capital (to risk-weighted assets), For capital adequacy purposes Amount				232,913,137.5000	108,152,000
Total capital (to risk-weighted assets), For capital adequacy purposes Amount				$ 303,226,537.5000	$ 144,203,000
Tier 1 capital (to average assets), For capital adequacy purposes Ratio				4.00%
Common equity Tier 1 (to risk-weighted assets), For capital adequacy purposes Ratio				5.125%	4.50%
Tier 1 capital (to risk-weighted assets), For capital adequacy purposes Ratio				6.625%	6.00%
Total capital (to risk-weighted assets) For capital adequacy purposes Ratio				8.625%	8.00%
Tier 1 capital (to average assets), To be well capitalized under prompt corrective action Amount				$ 221,070,500.0	$ 128,669,000
Common equity Tier 1 (to risk-weighted asset), To be well capitalized under prompt corrective action Amount				228,518,550.00	117,165,000
Tier 1 capital (to risk-weighted assets), To be well capitalized under prompt corrective action Amount				281,253,600.0	144,203,000
Total capital (to risk-weighted assets), To be well capitalized under prompt corrective action Amount				$ 351,567,000	$ 180,253,000
Tier 1 capital (to average assets), To be well capitalized under prompt corrective action Ratio				5.00%
Common equity Tier 1 (to risk-weighted asset), To be well capitalized under prompt corrective action Ratio				6.50%	6.50%
Tier 1 capital (to risk-weighted assets), To be well capitalized under prompt corrective action Ratio				8.00%	8.00%
Total capital (to risk-weighted assets), To be well capitalized under prompt corrective action Ratio				10.00%	10.00%
OceanFirst Financial Corp.
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 capital (to average assets), Actual Amount				$ 440,552,000	$ 250,324,000
Common equity Tier 1 (to risk-weighted asset), Actual Amount				426,855,000	241,856,000
Tier 1 capital (to risk-weighted assets), Actual Amount				440,552,000	250,324,000
Total capital (to risk-weighted assets), Actual Amount				$ 491,362,000	$ 267,124,000
Tier 1 capital (to average assets), Actual Ratio				9.96%	9.72%
Common equity Tier 1 (to risk-weighted assets), Actual Ratio				12.12%	13.40%
Tier 1 capital (to risk-weighted assets), Actual Ratio				12.51%	13.87%
Total capital (to risk-weighted assets), Actual Ratio				13.95%	14.80%
Tier 1 capital (to average assets), For capital adequacy purposes Amount				$ 176,896.6	$ 102,984,000
Common equity Tier 1 (to risk-weighted asset), For capital adequacy purposes Amount				180,511.87875	81,234,000
Tier 1 capital (to risk-weighted assets), For capital adequacy purposes Amount				233,344.62375	108,312,000
Total capital (to risk-weighted assets), For capital adequacy purposes Amount				$ 303,788.28375	$ 144,416,000
Tier 1 capital (to average assets), For capital adequacy purposes Ratio				4.00%	4.00%
Common equity Tier 1 (to risk-weighted assets), For capital adequacy purposes Ratio				5.125%	4.50%
Tier 1 capital (to risk-weighted assets), For capital adequacy purposes Ratio				6.625%	6.00%
Total capital (to risk-weighted assets) For capital adequacy purposes Ratio				8.625%	8.00%
Scenario, Forecast
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Capital conservation buffer (as a percent)	2.50%	1.875%	1.25%