Consolidated Statement of Changes in Stockholders' Equity (USD $) In Thousands, unless otherwise specified	Common stock	Additional paid-in capital	Retained earnings	Accumulated other comprehensive income (loss)	Total
Balance at Dec. 31, 2013	$ 9,581	$ 33,255	$ 188,825	$ (2,217)	$ 229,444
Balance (in shares) at Dec. 31, 2013	14,609
Increase (Decrease) in Stockholders' Equity
Net income			8,177		8,177
Other comprehensive income (loss), net of tax				2,047	2,047
Stock compensation expense		290			290
Stock issued for exercise of stock options, net of withholdings to satisfy employee tax obligations upon vesting of stock awards	75	601	(23)		653
Stock issued for exercise of stock options, net of withholdings to satisfy employee tax obligations upon vesting of stock awards (in shares)	22
Stock issued for share-based awards, net of withholdings to satisfy employee tax obligations upon award	18	(112)			(94)
Stock issued for share-based awards, net of withholdings to satisfy employee tax obligations upon award (in shares)	5
Stock issued for non-vested restricted stock	131	1,015	(1,146)
Stock issued for non-vested restricted stock (in shares)	40
Cash dividends, $0.23 and $0.21 per share for the three months ended March 31, 2015 and 2014 respectively			(3,075)		(3,075)
Shares repurchased or cancelled	(56)	(435)	25		(466)
Shares repurchased or cancelled (in shares)	(17)
Balance at Mar. 31, 2014	9,749	34,614	192,783	(170)	236,976
Balance (in shares) at Mar. 31, 2014	14,659
Balance at Dec. 31, 2014	10,035	38,191	209,584	2,085	259,895
Balance (in shares) at Dec. 31, 2014	14,745
Increase (Decrease) in Stockholders' Equity
Net income			9,255		9,255
Other comprehensive income (loss), net of tax				1,861	1,861
Stock compensation expense		501			501
Stock issued for exercise of stock options, net of withholdings to satisfy employee tax obligations upon vesting of stock awards	42	424	(17)		449
Stock issued for exercise of stock options, net of withholdings to satisfy employee tax obligations upon vesting of stock awards (in shares)	13
Stock issued for share-based awards, net of withholdings to satisfy employee tax obligations upon award	61	(397)	(128)		(464)
Stock issued for share-based awards, net of withholdings to satisfy employee tax obligations upon award (in shares)	18
Stock issued for non-vested restricted stock	116	1,085	(1,201)
Stock issued for non-vested restricted stock (in shares)	35
Cash dividends, $0.23 and $0.21 per share for the three months ended March 31, 2015 and 2014 respectively			(3,393)		(3,393)
Shares repurchased or cancelled	(51)	(452)			(503)
Shares repurchased or cancelled (in shares)	(16)
Balance at Mar. 31, 2015	$ 10,203	$ 39,352	$ 214,100	$ 3,946	$ 267,601
Balance (in shares) at Mar. 31, 2015	14,795