CONDENSED FINANCIAL STATEMENTS OF PEAPACK-GLADSTONE FINANCIAL CORPORATION (PARENT COMPANY ONLY) (STATEMENTS OF CASH FLOWS) (Details) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net income	$ 10,369	$ 10,206	$ 7,940	$ 7,982	$ 7,308	$ 7,116	$ 6,564	$ 5,489	$ 4,343	$ 5,383	$ 5,238	$ 5,008	$ 36,497	$ 26,477	$ 19,972
Gain on securities available for sale														(119)	(527)
Amortization of subordinated debt costs													135	71
Increase in other assets													(9,977)	945	(476)
Increase in other liabilities													2,330	2,936	3,511
Net cash used in operating activities													55,935	42,926	30,306
Cash flows from investing activities:
Proceeds from sales and calls of securities available for sale														5,499	46,254
Net cash used in investing activities													(435,514)	(433,175)	(625,427)
Cash flows from financing activities:
Cash dividends paid on common stock													(3,548)	(3,296)	(3,100)
Exercise of stock options, net of stock swaps													690	1,069	86
Proceeds from issuance of subordinated debt													34,125	48,693
Issuance of common shares (DRIP program)													36,588	22,461	13,648
Purchase of shares of profit sharing plan													889
Net cash provided by financing activities													330,335	482,780	634,074
Net increase/(decrease) in cash and cash equivalents													(49,244)	92,531	38,953
Parent Company [Member]
Cash flows from operating activities:
Net income													36,497	26,477	19,972
Undistributed earnings of Bank													(38,942)	(28,036)	(20,316)
Amortization of subordinated debt costs													135	71
Increase in other assets													(1,248)	(889)	(194)
Increase in other liabilities													113	114	81
Net cash used in operating activities													(3,445)	(2,263)	(457)
Cash flows from investing activities:
Capital contribution to subsidiary													(60,177)	(57,823)	(18,000)
Net cash used in investing activities													(60,177)	(57,823)	(18,000)
Cash flows from financing activities:
Cash dividends paid on common stock													(3,548)	(3,296)	(3,100)
Exercise of stock options, net of stock swaps													690	1,069	86
Proceeds from issuance of subordinated debt													34,125	48,693
Issuance of common shares (DRIP program)													36,588	22,461	13,648
Net cash provided by financing activities													67,855	68,927	10,634
Net increase/(decrease) in cash and cash equivalents													4,233	8,841	(7,823)
Cash and cash equivalents at beginning of period				$ 10,845				$ 2,004				$ 9,827	10,845	2,004	9,827
Cash and cash equivalents at end of period	$ 15,078				$ 10,845				$ 2,004				$ 15,078	$ 10,845	$ 2,004