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		6.375%
Tier 1 capital (to risk-weighted assets), Actual Ratio		5.00%
Tier 1 capital (to average assets), For capital adequacy purposes Ratio		7.875%	4.00%
Total capital (to risk-weighted assets) For capital adequacy purposes Ratio		9.875%
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)		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		$ 712,900,000	$ 459,031,000
Common equity Tier 1 (to risk-weighted asset), Actual Amount		712,900,000	459,031,000
Tier 1 capital (to risk-weighted assets), Actual Amount		712,900,000	459,031,000
Total capital (to risk-weighted assets), Actual Amount		$ 730,484,000	$ 475,379,000
Tier 1 capital (to average assets), Actual Ratio		10.01%	8.75%
Common equity Tier 1 (to risk-weighted assets), Actual Ratio		13.39%	12.41%
Tier 1 capital (to risk-weighted assets), Actual Ratio		13.39%	12.41%
Total capital (to risk-weighted assets), Actual Ratio		13.72%	12.85%
Tier 1 capital (to average assets), For capital adequacy purposes Amount		$ 284,772,360	$ 209,759,640
Common equity Tier 1 (to risk-weighted asset), For capital adequacy purposes Amount		339,513,056.25	212,705,495
Tier 1 capital (to risk-weighted assets), For capital adequacy purposes Amount		419,398,481.25	268,193,885
Total capital (to risk-weighted assets), For capital adequacy purposes Amount		$ 525,912,381.25	$ 342,178,405
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		6.375%	5.75%
Tier 1 capital (to risk-weighted assets), For capital adequacy purposes Ratio		7.875%	7.25%
Total capital (to risk-weighted assets) For capital adequacy purposes Ratio		9.875%	9.25%
Tier 1 capital (to average assets), To be well capitalized under prompt corrective action Amount		$ 355,965,450	$ 262,199,550
Common equity Tier 1 (to risk-weighted asset), To be well capitalized under prompt corrective action Amount		346,170,175	240,449,690
Tier 1 capital (to risk-weighted assets), To be well capitalized under prompt corrective action Amount		426,055,600	295,938,080
Total capital (to risk-weighted assets), To be well capitalized under prompt corrective action Amount		$ 532,569,500	$ 369,922,600
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		$ 709,972,000	$ 465,554,000
Common equity Tier 1 (to risk-weighted asset), Actual Amount		647,773,000	449,991,000
Tier 1 capital (to risk-weighted assets), Actual Amount		709,972,000	465,554,000
Total capital (to risk-weighted assets), Actual Amount		$ 762,556,000	$ 516,902,000
Tier 1 capital (to average assets), Actual Ratio		9.96%	8.87%
Common equity Tier 1 (to risk-weighted assets), Actual Ratio		12.15%	12.15%
Tier 1 capital (to risk-weighted assets), Actual Ratio		13.32%	12.57%
Total capital (to risk-weighted assets), Actual Ratio		14.31%	13.96%
Tier 1 capital (to average assets), For capital adequacy purposes Amount		$ 285,199,080	$ 209,943,200
Common equity Tier 1 (to risk-weighted asset), For capital adequacy purposes Amount		339,790,815	212,906,687.5
Tier 1 capital (to risk-weighted assets), For capital adequacy purposes Amount		419,741,595	268,447,562.5
Total capital (to risk-weighted assets), For capital adequacy purposes Amount		$ 526,342,635	$ 342,502,062.5
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		6.375%	5.75%
Tier 1 capital (to risk-weighted assets), For capital adequacy purposes Ratio		7.875%	7.25%
Total capital (to risk-weighted assets) For capital adequacy purposes Ratio		9.875%	9.25%
Scenario, Forecast
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Capital conservation buffer (as a percent)	2.50%