Consolidated Statements Of Changes In Shareholders' Equity (USD $) In Thousands, unless otherwise specified	Total	Common Stock [Member]	Capital Surplus[Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Beginning Balance at Dec. 31, 2013	$ 387,623	$ 46,249	$ 107,596	$ 333,970	$ (95,202)	$ (4,990)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	13,803			13,803
Other comprehensive income (loss)	776					776
Cash dividends declared	(6,287)			(6,287)
Stock-based compensation expense, net	572		(746)		1,318
Exercise of stock options	199		(107)		306
Purchase of treasury shares	(2,936)				(2,936)
Ending balance at Mar. 31, 2014	393,750	46,249	106,743	341,486	(96,514)	(4,214)
Beginning Balance at Dec. 31, 2014	390,853	46,249	107,370	362,211	(120,818)	(4,159)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	17,992			17,992
Other comprehensive income (loss)	906					906
Cash dividends declared	(6,391)			(6,391)
Stock-based compensation expense, net	740		(679)		1,419
Exercise of stock options	975		(294)		1,269
Ending balance at Mar. 31, 2015	$ 405,075	$ 46,249	$ 106,397	$ 373,812	$ (118,130)	$ (3,253)