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, 2011	$ 311,134	$ 46,249	$ 103,335	$ 291,050	$ (125,593)	$ (3,907)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	17,442			17,442
Other comprehensive income	1,430					1,430
Acquisition, stock issued, value	7,723		276		7,447
Cash dividends declared	(10,337)			(10,337)
Stock-based compensation expense, net	657		(49)		706
Exercise of stock options	488		(113)		601
Purchase of treasury shares	(7,915)				(7,915)
Ending balance at Jun. 30, 2012	320,622	46,249	103,449	298,155	(124,754)	(2,477)
Beginning Balance at Dec. 31, 2012	333,274	46,249	103,524	309,270	(124,347)	(1,422)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	20,993			20,993
Other comprehensive income	(4,118)					(4,118)
Acquisition, stock issued, value	28,508		4,236		24,272
Cash dividends declared	(11,866)			(11,866)
Stock-based compensation expense, net	703		(512)		1,215
Exercise of stock options	1,397		(13)		1,410
Ending balance at Jun. 30, 2013	$ 368,891	$ 46,249	$ 107,235	$ 318,397	$ (97,450)	$ (5,540)