CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (unaudited) - USD ($) $ in Thousands	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Total
Balance at Dec. 31, 2018		$ 412,546	$ 15,542	$ 211,345	$ (16,717)	$ (8,789)	$ 613,927
Net income				52,612			52,612
Other comprehensive income net of tax						7,661	7,661
Cash dividends declared on common stock				(9,798)			(9,798)
Exercise of stock options			265				265
Restricted stock grants, net of forfeitures
Net shares issued in satisfaction of restricted stock units earned
Repurchase of treasury stock					(5,175)		(5,175)
Stock issued in acquisition of Greater Hudson Bank		56,025					56,025
Net shares issued in satisfaction of performance units earned			196				196
Restricted stock issued shares in acquisition of BoeFly, LLC			2,500				2,500
Stock-based compensation			1,947				1,947
Balance at Sep. 30, 2019		468,571	20,450	254,159	(21,892)	(1,128)	720,160
Balance at Jun. 30, 2019		468,571	19,777	235,649	(21,892)	(2,881)	699,224
Net income				21,696			21,696
Other comprehensive income net of tax						1,753	1,753
Cash dividends declared on common stock				(3,186)			(3,186)
Restricted stock grants, net of forfeitures
Stock-based compensation			673				673
Balance at Sep. 30, 2019		468,571	20,450	254,159	(21,892)	(1,128)	720,160
Balance at Dec. 31, 2019		468,571	21,344	271,782	(29,360)	(1,147)	731,190
Net income				45,648			45,648
Other comprehensive income net of tax						2,448	2,448
Cash dividends declared on common stock				(7,537)			(7,537)
Exercise of stock options			163				163
Restricted stock grants, net of forfeitures
Stock grants issued
Net shares issued in satisfaction of restricted stock units earned
Share redemption for tax withholdings on performance units and restricted stock units earned			(639)				(639)
Repurchase of treasury stock					(911)		(911)
Stock issued in acquisition of Bancorp of New Jersey		118,375					118,375
Net shares issued in satisfaction of performance units earned
Stock-based compensation			1,999				1,999
Balance at Sep. 30, 2020		586,946	22,867	309,893	(30,271)	1,301	890,736
Balance at Jun. 30, 2020		586,946	22,069	288,688	(30,271)	309	867,741
Net income				24,786			24,786
Other comprehensive income net of tax						992	992
Cash dividends declared on common stock				(3,581)			(3,581)
Restricted stock grants, net of forfeitures
Stock-based compensation			798				798
Balance at Sep. 30, 2020		$ 586,946	$ 22,867	$ 309,893	$ (30,271)	$ 1,301	$ 890,736