Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Employee Stock Ownership Plan	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive (Loss) Gain	Treasury Stock	Common Stock Acquired by Deferred Compensation Plan	Deferred Compensation Plan Liability
Beginning Balance at Dec. 31, 2015	$ 238,446	$ (3,045)	$ 336	$ 269,757	$ 229,140	$ (6,241)	$ (251,501)	$ (314)	$ 314
Net income	23,046				23,046
Other comprehensive income, net of tax	492					492
Stock awards	1,505			1,505
Tax benefit of stock plans	62			62
Treasury stock allocated to restricted stock plan	0			1,046	(101)		(945)
Purchase 90,000 shares of common stock in 2016 and 2018	(1,878)						(1,878)
Allocation of ESOP stock	657	284		373
Cash dividend $0.54, $0.60 and $0.62 per share for 2016, 2017 and 2018 respectively	$ (12,616)				(12,616)
Exercise of stock options, shares	375,576
Exercise of stock options	$ 3,989				(1,277)		5,266
Sale/Purchase of stock for the deferred compensation plan, net								1	(1)
Issued 459,251 and 14,547,452 treasury shares to finance acquisition in 2016 and 2018	318,200			91,690			226,510
Ending Balance at Dec. 31, 2016	571,903	(2,761)	336	364,433	238,192	(5,749)	(22,548)	(313)	313
Net income	42,470				42,470
Other comprehensive income, net of tax	400					400
Stock awards	2,181			2,181
Effect of adopting Accounting Standards Update (“ASU”) | Accounting Standards Update 2016-09	0			(11,129)	11,129
Treasury stock allocated to restricted stock plan	0			(1,745)	822		923
Allocation of ESOP stock	919	282		637
Cash dividend $0.54, $0.60 and $0.62 per share for 2016, 2017 and 2018 respectively	$ (19,286)				(19,286)
Exercise of stock options, shares	567,153
Exercise of stock options	$ 3,354				(2,304)		5,658
Sale/Purchase of stock for the deferred compensation plan, net								229	(229)
Ending Balance at Dec. 31, 2017	601,941	(2,479)	$ 336	354,377	271,023	(5,349)	(15,967)	(84)	84
Net income	71,932				71,932
Other comprehensive income, net of tax	1,752					1,752
Stock awards (shares)			2,000
Stock awards	3,038			3,036
Effect of adopting Accounting Standards Update (“ASU”) | Accounting Standards Update 2016-09	0				(147)	147
Acquisition of common stock by ESOP	(8,400)	(8,400)
Purchase 90,000 shares of common stock in 2016 and 2018	(10,837)						(10,837)
Allocation of ESOP stock	1,618	1,022		596
Cash dividend $0.54, $0.60 and $0.62 per share for 2016, 2017 and 2018 respectively	$ (29,564)				(29,564)
Exercise of stock options, shares	765,624		4,000
Exercise of stock options	$ 5,324			13,306	(8,188)		202
Acquisition of Sun Bancorp Inc., shares			141,000
Acquisition of Sun Bancorp Inc., value	402,554			386,648			15,765
Sale/Purchase of stock for the deferred compensation plan, net								(3)	3
Ending Balance at Dec. 31, 2018	$ 1,039,358	$ (9,857)	$ 483	$ 757,963	$ 305,056	$ (3,450)	$ (10,837)	$ (87)	$ 87