Consolidated Statements Of Changes In Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Capital Surplus	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Income (Loss)
Beginning Balance at Dec. 31, 2017	$ 502,507	$ 47,619	$ 140,960	$ 444,481	$ (124,909)	$ (5,644)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income available to common shareholders	17,616			17,616
Other comprehensive income (loss)	(8,218)					(8,218)
New Accounting Pronouncement	0
New Accounting Pronouncement | Accounting Standards Update 2016-01	(2,657)			2,657		(2,657)
Cash dividends declared	(7,104)			(7,104)
Stock-based compensation expense	793		793
Restricted awards granted	0		(1,135)		1,135
Exercise of stock options	280		(71)		351
Purchase of treasury shares	(13,997)				(13,997)
Ending balance at Mar. 31, 2018	491,877	47,619	140,547	457,650	(137,420)	(16,519)
Beginning Balance at Dec. 31, 2018	600,764	47,619	169,555	485,967	(87,895)	(14,482)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income available to common shareholders	21,619			21,619
Other comprehensive income (loss)	8,631					8,631
Cash dividends declared	(8,739)			(8,739)
Stock-based compensation expense	803		803
Restricted awards granted	0		(224)		224
Exercise of stock options	252		81		171
Purchase of treasury shares	(4,089)				(4,089)
Ending balance at Mar. 31, 2019	$ 619,241	$ 47,619	$ 170,215	$ 498,847	$ (91,589)	$ (5,851)