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
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	7.00%
Tier 1 capital (to risk-weighted assets), Actual Ratio	5.00%
Tier 1 capital (to average assets), For capital adequacy purposes Ratio	8.50%	4.00%
Total capital (to risk-weighted assets) For capital adequacy purposes Ratio	10.50%
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)	2.50%	1.875%	1.25%	0.625%
OceanFirst Bank
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 capital (to average assets), Actual Amount	$ 779,108,000	$ 712,900,000
Common equity Tier 1 (to risk-weighted asset), Actual Amount	779,108,000	712,900,000
Tier 1 capital (to risk-weighted assets), Actual Amount	779,108,000	712,900,000
Total capital (to risk-weighted assets), Actual Amount	$ 797,339,000	$ 730,484,000
Tier 1 capital (to average assets), Actual Ratio	10.03%	10.01%
Common equity Tier 1 (to risk-weighted assets), Actual Ratio	12.98%	13.39%
Tier 1 capital (to risk-weighted assets), Actual Ratio	12.98%	13.39%
Total capital (to risk-weighted assets), Actual Ratio	13.29%	13.72%
Tier 1 capital (to average assets), For capital adequacy purposes Amount	$ 310,798,000	$ 284,772,000
Common equity Tier 1 (to risk-weighted asset), For capital adequacy purposes Amount	420,106,000	339,513,000
Tier 1 capital (to risk-weighted assets), For capital adequacy purposes Amount	510,129,000	419,398,000
Total capital (to risk-weighted assets), For capital adequacy purposes Amount	$ 630,159,000	$ 525,912,000
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	7.00%	6.375%
Tier 1 capital (to risk-weighted assets), For capital adequacy purposes Ratio	8.50%	7.875%
Total capital (to risk-weighted assets) For capital adequacy purposes Ratio	10.50%	9.875%
Tier 1 capital (to average assets), To be well capitalized under prompt corrective action Amount	$ 388,498,000	$ 355,965,000
Common equity Tier 1 (to risk-weighted asset), To be well capitalized under prompt corrective action Amount	390,099,000	346,170,000
Tier 1 capital (to risk-weighted assets), To be well capitalized under prompt corrective action Amount	480,121,000	426,056,000
Total capital (to risk-weighted assets), To be well capitalized under prompt corrective action Amount	$ 600,152,000	$ 532,570,000
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	$ 791,746,000	$ 709,972,000
Common equity Tier 1 (to risk-weighted asset), Actual Amount	729,095,000	647,773,000
Tier 1 capital (to risk-weighted assets), Actual Amount	791,746,000	709,972,000
Total capital (to risk-weighted assets), Actual Amount	$ 844,977,000	$ 762,556,000
Tier 1 capital (to average assets), Actual Ratio	10.17%	9.96%
Common equity Tier 1 (to risk-weighted assets), Actual Ratio	12.14%	12.15%
Tier 1 capital (to risk-weighted assets), Actual Ratio	13.19%	13.32%
Total capital (to risk-weighted assets), Actual Ratio	14.07%	14.31%
Tier 1 capital (to average assets), For capital adequacy purposes Amount	$ 311,289,000	$ 285,199,000
Common equity Tier 1 (to risk-weighted asset), For capital adequacy purposes Amount	420,273,000	339,791,000
Tier 1 capital (to risk-weighted assets), For capital adequacy purposes Amount	510,331,000	419,742,000
Total capital (to risk-weighted assets), For capital adequacy purposes Amount	$ 630,409,000	$ 526,343,000
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	7.00%	6.375%
Tier 1 capital (to risk-weighted assets), For capital adequacy purposes Ratio	8.50%	7.875%
Total capital (to risk-weighted assets) For capital adequacy purposes Ratio	10.50%	9.875%