Regulatory Matters - Summary of Regulatory Capital Amounts and Ratios (Details) $ in Thousands	12 Months Ended
Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 capital (to average assets), Actual Ratio	0.040
Common equity Tier 1 (to risk-weighted assets), Actual Ratio	7.00%
Tier 1 capital (to risk-weighted assets), Actual Ratio	0.050
Tier 1 capital (to average assets), For capital adequacy purposes Ratio	0.085	0.0400
Total capital (to risk-weighted assets) For capital adequacy purposes Ratio	0.105
Tier 1 capital (to average assets), To be well capitalized under prompt corrective action Ratio		0.0500
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	0.080
Total capital (to risk-weighted assets), To be well capitalized under prompt corrective action Ratio	0.100
Capital conservation buffer (as a percent)	2.50%
OceanFirst Bank
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 capital (to average assets), Actual Amount	$ 942,122	$ 779,108
Common equity Tier 1 (to risk-weighted asset), Actual Amount	942,122	779,108
Tier 1 capital (to risk-weighted assets), Actual Amount	942,122	779,108
Total capital (to risk-weighted assets), Actual Amount	$ 1,004,480	$ 797,339
Tier 1 capital (to average assets), Actual Ratio	0.0848	0.1003
Common equity Tier 1 (to risk-weighted assets), Actual Ratio	12.11%	12.98%
Tier 1 capital (to risk-weighted assets), Actual Ratio	0.1211	0.1298
Total capital (to risk-weighted assets), Actual Ratio	0.1291	0.1329
Tier 1 capital (to average assets), For capital adequacy purposes Amount	$ 444,648	$ 310,798
Common equity Tier 1 (to risk-weighted asset), For capital adequacy purposes Amount	544,625	420,106
Tier 1 capital (to risk-weighted assets), For capital adequacy purposes Amount	661,331	510,129
Total capital (to risk-weighted assets), For capital adequacy purposes Amount	$ 816,938	$ 630,159
Tier 1 capital (to average assets), For capital adequacy purposes Ratio	0.0400
Common equity Tier 1 (to risk-weighted assets), For capital adequacy purposes Ratio	7.00%	7.00%
Tier 1 capital (to risk-weighted assets), For capital adequacy purposes Ratio	0.0850	0.0850
Total capital (to risk-weighted assets) For capital adequacy purposes Ratio	0.1050	0.1050
Tier 1 capital (to average assets), To be well capitalized under prompt corrective action Amount	$ 555,810	$ 388,498
Common equity Tier 1 (to risk-weighted asset), To be well capitalized under prompt corrective action Amount	505,724	390,099
Tier 1 capital (to risk-weighted assets), To be well capitalized under prompt corrective action Amount	622,429	480,121
Total capital (to risk-weighted assets), To be well capitalized under prompt corrective action Amount	$ 778,036	$ 600,152
Tier 1 capital (to average assets), To be well capitalized under prompt corrective action Ratio	0.0500
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	0.0800	0.0800
Total capital (to risk-weighted assets), To be well capitalized under prompt corrective action Ratio	0.1000	0.1000
OceanFirst Financial Corp.
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 capital (to average assets), Actual Amount	$ 998,273	$ 791,746
Common equity Tier 1 (to risk-weighted asset), Actual Amount	871,385	729,095
Tier 1 capital (to risk-weighted assets), Actual Amount	998,273	791,746
Total capital (to risk-weighted assets), Actual Amount	$ 1,230,370	$ 844,977
Tier 1 capital (to average assets), Actual Ratio	0.0944	0.1017
Common equity Tier 1 (to risk-weighted assets), Actual Ratio	11.05%	12.14%
Tier 1 capital (to risk-weighted assets), Actual Ratio	0.1266	0.1319
Total capital (to risk-weighted assets), Actual Ratio	0.1560	0.1407
Tier 1 capital (to average assets), For capital adequacy purposes Amount	$ 423,028	$ 311,289
Common equity Tier 1 (to risk-weighted asset), For capital adequacy purposes Amount	552,075	420,273
Tier 1 capital (to risk-weighted assets), For capital adequacy purposes Amount	670,377	510,331
Total capital (to risk-weighted assets), For capital adequacy purposes Amount	$ 828,113	$ 630,409
Tier 1 capital (to average assets), For capital adequacy purposes Ratio	0.0400	0.0400
Common equity Tier 1 (to risk-weighted assets), For capital adequacy purposes Ratio	7.00%	7.00%
Tier 1 capital (to risk-weighted assets), For capital adequacy purposes Ratio	0.0850	0.0850
Total capital (to risk-weighted assets) For capital adequacy purposes Ratio	0.1050	0.1050

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Amount of total capital as defined by regulatory framework.

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