CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Stockholders' Equity, Beginning Balance at Dec. 31, 2010	$ 268,864	$ 1,011	$ 84,889	$ 178,939	$ 4,025
Common Stock, Shares Outstanding, Beginning Balance at Dec. 31, 2010		16,172,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	29,724			29,724
Total other comprehensive income (loss), net of tax	(5,920)				(5,920)
Cash dividends declared	(14,465)			(14,465)
Share-based compensation	1,394		1,394
Exercise of stock options, issuance of other compensation-related equity instruments and related tax benefit, shares		87,000
Exercise of stock options, issuance of other compensation-related equity instruments and related tax benefit	1,000	5	995
Shares issued - dividend reinvestment plan, shares		33,000
Shares issued - dividend reinvestment plan	754	2	752
Stockholders' Equity, Ending Balance at Dec. 31, 2011	281,351	1,018	88,030	194,198	(1,895)
Common Stock, Shares Outstanding, Ending Balance at Dec. 31, 2011		16,292,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	35,074			35,074
Other Comprehensive Income (Loss), Net of Tax					(8,604)
Total other comprehensive income (loss), net of tax	(8,604)
Cash dividends declared	(15,598)			(15,598)
Share-based compensation	1,962		1,962
Deferred compensation plan, shares		10,000
Deferred compensation plan	146	1	145
Exercise of stock options, issuance of other compensation-related equity instruments and related tax benefit, shares		78,000
Exercise of stock options, issuance of other compensation-related equity instruments and related tax benefit	1,321	5	1,316
Stockholders' Equity, Ending Balance at Dec. 31, 2012	295,652	1,024	91,453	213,674	(10,499)
Common Stock, Shares Outstanding, Ending Balance at Dec. 31, 2012	16,379,771	16,380,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	36,153			36,153
Other Comprehensive Income (Loss), Net of Tax					8,946
Total other comprehensive income (loss), net of tax	8,946
Cash dividends declared	(17,232)			(17,232)
Share-based compensation	1,876		1,876
Deferred compensation plan, shares		2,000
Deferred compensation plan	30	0	30
Exercise of stock options, issuance of other compensation-related equity instruments and related tax benefit, shares		232,000
Exercise of stock options, issuance of other compensation-related equity instruments and related tax benefit	4,221	14	4,207
Stockholders' Equity, Ending Balance at Dec. 31, 2013	$ 329,646	$ 1,038	$ 97,566	$ 232,595	$ (1,553)
Common Stock, Shares Outstanding, Ending Balance at Dec. 31, 2013	16,613,561	16,614,000