Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands		Total	Common Stock	Capital in Excess of Par Value	Accumulated Other Comprehensive (Loss) Income	Retained Earnings	Treasury Stock
Beginning Balance (in shares) at Dec. 31, 2015			55,945,245
Beginning Balance at Dec. 31, 2015		$ 580,471	$ 560	$ 256,435	$ 696	$ 570,630	$ (247,850)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income		64,080				64,080
Other comprehensive income (loss)		(8,313)			(8,313)
Cash dividend		(7,632)				(7,632)
Issuance of common stock including proceeds from exercise of common stock options (in shares)			265,853
Issuance of common stock including proceeds from exercise of common stock options		1,900	$ 2	1,898
Stock-based compensation expense		2,790		2,790
Acquisition of Penn Liberty (in shares)			1,806,748
Acquisition of Penn Liberty		68,352	$ 18	68,334
Repurchases of common stock		(14,312)					(14,312)
Treasury share adjustment (in shares)	[1]		(2,022,627)
Ending Balance (in shares) at Dec. 31, 2016			55,995,219
Ending Balance at Dec. 31, 2016		687,336	$ 580	329,457	(7,617)	627,078	(262,162)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Reclassification due to the adoption of ASU | Accounting Standards Update 2018-02		0			(1,660)	1,660
Net Income		50,244				50,244
Other comprehensive income (loss)		1,125			1,125
Cash dividend		(9,425)				(9,425)
Issuance of common stock including proceeds from exercise of common stock options (in shares)			284,308
Issuance of common stock including proceeds from exercise of common stock options		3,421	$ 3	3,418
Stock-based compensation expense		3,396		3,396
Repurchases of common stock		(11,752)	$ (20)				(11,732)
Ending Balance (in shares) at Dec. 31, 2017			56,279,527
Ending Balance at Dec. 31, 2017		724,345	$ 563	336,271	(8,152)	669,557	(273,894)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Reclassification due to the adoption of ASU | Accounting Standards Update 2016-01		0			20	(20)
Net Income		134,743				134,743
Other comprehensive income (loss)		(7,242)			(7,262)
Cash dividend		(13,249)				(13,249)
Issuance of common stock including proceeds from exercise of common stock options (in shares)			647,451
Issuance of common stock including proceeds from exercise of common stock options		11,253	$ 6	11,247
Stock-based compensation expense		2,292		2,292
Repurchases of common stock		(31,202)					(31,202)
Ending Balance (in shares) at Dec. 31, 2018			56,926,978.000
Ending Balance at Dec. 31, 2018		$ 820,920	$ 569	$ 349,810	$ (15,394)	$ 791,031	$ (305,096)

[1] The 2016 Consolidated Statement of Changes in Stockholder's Equity reflects an adjustment between shares issued and treasury stock. This reclassification had no impact on shares outstanding, earnings per share or retained earnings.