SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Additional Information (Details)	1 Months Ended	12 Months Ended
	May 31, 2020 shares	Dec. 31, 2023 USD ($) Segment shares	Dec. 31, 2022 USD ($) shares	Dec. 31, 2021 USD ($) shares	Jan. 01, 2022 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of operating segments | Segment		2
Federal funds sales periods		1 day
Interest-earning deposits maturities period		1 year
Servicing rights		$ 0
Amount of loans serviced		$ 162,900,000	$ 152,200,000
Threshold period for loan		30 days
Threshold for determining nonaccrual status		90 days
Post-modification outstanding recorded investment			$ 11,208,000	$ 2,691,000
Issuance of shares for Employee Stock Purchase Plan, shares | shares		33,748	25,023	26,693
Antidilutive securities | shares		387,768	291,462	264,317
Net increase to retained earnings		$ 394,094,000	$ 348,798,000
Reduction to allowance for credit losses		$ (687,000)	(752,000)
ASU 2016-13 [Member]
Summary Of Significant Accounting Policies [Line Items]
Net increase to retained earnings					$ 3,900,000
Reduction to allowance for credit losses					$ 5,500,000
Employee Stock Option [Member]
Summary Of Significant Accounting Policies [Line Items]
Option term		10 years
Compensation cost		$ 0	0	$ 0
Employee Stock [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of share purchase rights authorized | shares		150,000
Additional common stock to be issued | shares	200,000
Percentage of closing market price on purchase date		85.00%
Compensation cost		$ 178,000	145,000	$ 126,000
Premises [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful life		40 years
Consumer and Other [Member]
Summary Of Significant Accounting Policies [Line Items]
Threshold for determining nonaccrual status		120 days
Small Business Administration Loans [Member]
Summary Of Significant Accounting Policies [Line Items]
Loans held for sale		$ 7,200,000	$ 17,200,000
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Cash equivalents original maturities period		90 days
Short term borrowings original maturities period		90 days
Finite-Lived Intangible Asset, Useful Life		15 years
Maximum [Member] | Employee Stock Option [Member]
Summary Of Significant Accounting Policies [Line Items]
Option term		10 years
Maximum [Member] | Employee Stock [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of compensation contributable		15.00%
Maximum [Member] | Equipment and Other Fixed Assets [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful life		10 years
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Finite-Lived Intangible Asset, Useful Life		5 years
Minimum [Member] | Employee Stock [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of compensation contributable		1.00%
Minimum [Member] | Equipment and Other Fixed Assets [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful life		3 years
Peapack-Gladstone Mortgage Group, Inc. [Member] | Peapack Ventures, LLC [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of interest owned		99.00%
Peapack-Gladstone Mortgage Group, Inc. [Member] | Peapack-Gladstone Realty, Inc [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of interest owned		79.00%
PGB Trust & Investments of Delaware [Member] | Peapack Ventures, LLC [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of interest owned		1.00%
Peapack Ventures, LLC [Member] | Peapack-Gladstone Realty, Inc [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of interest owned		21.00%