Consolidated Statements Of Changes In Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Capital Surplus[Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Beginning Balance at Dec. 31, 2014	$ 390,853	$ 46,249	$ 107,370	$ 362,211	$ (120,818)	$ (4,159)
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)
Beginning Balance at Dec. 31, 2015	419,272	46,249	106,269	390,690	(120,104)	(3,832)
Net income	11,702			11,702
Other comprehensive income (loss)	2,743					2,743
Cash dividends declared	(6,429)			(6,429)
Stock-based compensation expense, net	755		(132)		887
Purchase of treasury shares	(9,925)				(9,925)
Ending balance at Mar. 31, 2016	$ 418,118	$ 46,249	$ 106,137	$ 395,963	$ (129,142)	$ (1,089)