Consolidated Statements of Changes in Shareholders' Equity (USD $) In Thousands, unless otherwise specified	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]
Balance at Dec. 31, 2012	$ 537,422	$ 77,993	$ 77,458	$ 436,039	$ (13,582)	$ (40,486)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	12,330			12,330
Other comprehensive income (loss), net of tax	(761)				(761)
Cash dividends declared	(4,460)			(4,460)
Treasury stock issued for restricted awards	0			206		(206)
Recognition of restricted stock compensation expense	118		118
Tax expense from stock-based compensation	(35)		(35)
Balance at Mar. 31, 2013	544,614	77,993	77,541	444,115	(14,343)	(40,692)
Balance at Dec. 31, 2013	571,306	77,993	78,140	468,158	(12,694)	(40,291)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	14,033			14,033
Other comprehensive income (loss), net of tax	3,046				3,046
Cash dividends declared	(4,758)			(4,758)
Treasury stock issued for restricted awards	(161)			357		(518)
Recognition of restricted stock compensation expense	185		185
Tax expense from stock-based compensation	0		0
Balance at Mar. 31, 2014	$ 583,651	$ 77,993	$ 78,325	$ 477,790	$ (9,648)	$ (40,809)