CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]	Retained Earnings [Member]
Stockholders Equity, Balance at Dec. 31, 2010	$ 246,997	$ 85,766	$ 1,350	$ (1,418)	$ 161,299
Stockholders Equity, Balance, Shares at Dec. 31, 2010		16,078,420
Comprehensive income:
Net income	30,662				30,662
Other comprehensive income (loss), net of tax	3,789		3,789
Comprehensive income (loss)	34,451
Common stock cash dividends declared	(10,058)				(10,058)
Treasury shares purchased under deferred directors' plan (in shares)		(10,648)
Treasury shares purchased under deferred directors' plan	0	244		(244)
Treasury stock sold and distributed under deferred directors' plan (in shares)		30,100
Treasury stock sold and distributed under deferred directors' plan	0	(440)		440
Stock activity under equity incentive plans (in shares)		47,900
Stock activity under equity incentive plans	468	468
Stock based compensation expense	1,342	1,342
Stockholders Equity, Balance at Dec. 31, 2011	273,200	87,380	5,139	(1,222)	181,903
Stockholders Equity, Balance, Shares at Dec. 31, 2011		16,145,772
Comprehensive income:
Net income	35,394				35,394
Other comprehensive income (loss), net of tax	550		550
Comprehensive income (loss)	35,944
Common stock cash dividends declared	(13,643)				(13,643)
Treasury shares purchased under deferred directors' plan (in shares)		(15,864)
Treasury shares purchased under deferred directors' plan	0	421		(421)
Stock activity under equity incentive plans (in shares)		160,228
Stock activity under equity incentive plans	894	894
Stock based compensation expense	1,344	1,344
Stockholders Equity, Balance at Dec. 31, 2012	297,739	90,039	5,689	(1,643)	203,654
Stockholders Equity, Balance, Shares at Dec. 31, 2012		16,290,136
Comprehensive income:
Net income	38,839				38,839
Other comprehensive income (loss), net of tax	(8,183)		(8,183)
Comprehensive income (loss)	30,656
Common stock cash dividends declared	(9,385)				(9,385)
Treasury shares purchased under deferred directors' plan (in shares)		(14,174)
Treasury shares purchased under deferred directors' plan	0	399		(399)
Treasury stock sold and distributed under deferred directors' plan (in shares)		3,018
Treasury stock sold and distributed under deferred directors' plan	0	(54)		54
Stock activity under equity incentive plans (in shares)		98,469
Stock activity under equity incentive plans	903	903
Stock based compensation expense	1,962	1,962
Stockholders Equity, Balance at Dec. 31, 2013	$ 321,875	$ 93,249	$ (2,494)	$ (1,988)	$ 233,108
Stockholders Equity, Balance, Shares at Dec. 31, 2013		16,377,449