Consolidated Statements of Stockholders' Equity (USD $) In Thousands, except Share data	Total	Common Stock	Value of Shares Held in Rabbi Trust at Cost	Deferred Compensation Obligation	Additional Paid in Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Beginning balance at Dec. 31, 2010	$ 436,472	$ 210	$ (2,738)	$ 2,738	$ 226,708	$ 210,320	$ (766)
Beginning balance (in shares) at Dec. 31, 2010		21,220,801
Net income	45,436					45,436
Other comprehensive loss	(3,720)						(3,720)
Common dividend declared	(16,304)					(16,304)
Proceeds from exercise of stock options, net of cash paid	4,127	2			4,125
Proceeds from exercise of stock options (in shares)		186,518
Tax benefit related to equity award activity	20				20
Stock based compensation	2,483				2,483
Restricted stock awards issued, net of awards surrendered	(361)				(361)
Restricted stock awards issued, net of awards surrendered (in shares)		60,495
Shares issued under direct stock purchase plan	824	1			823
Shares issued under direct stock purchase plan (in shares)		31,954
Deferred compensation obligation			(242)	242
Tax benefit related to deferred compensation distributions	80				80
Ending balance at Dec. 31, 2011	469,057	213	(2,980)	2,980	233,878	239,452	(4,486)
Ending balance (in shares) at Dec. 31, 2011		21,499,768
Net income	42,627					42,627
Other comprehensive loss	(40)						(40)
Common dividend declared	(18,408)					(18,408)
Common stock issued for acquisition	30,389	11			30,378
Common stock issued for acquisition (in shares)		1,068,514
Proceeds from exercise of stock options, net of cash paid	1,108	1			1,107
Proceeds from exercise of stock options (in shares)		61,326
Tax benefit related to equity award activity	426				426
Stock based compensation	2,845				2,845
Restricted stock awards issued, net of awards surrendered	(467)				(467)
Restricted stock awards issued, net of awards surrendered (in shares)		86,254
Shares issued under direct stock purchase plan	1,691				1,691
Shares issued under direct stock purchase plan (in shares)		58,147
Deferred compensation obligation			(199)	199
Tax benefit related to deferred compensation distributions	92				92
Ending balance at Dec. 31, 2012	529,320	225	(3,179)	3,179	269,950	263,671	(4,526)
Ending balance (in shares) at Dec. 31, 2012	22,774,009	22,774,009
Net income	50,254					50,254
Other comprehensive loss	(2,908)						(2,908)
Common dividend declared	(20,365)					(20,365)
Common stock issued for acquisition	29,390	8			29,382
Common stock issued for acquisition (in shares)		818,650
Proceeds from exercise of stock options, net of cash paid	2,475	1			2,474
Proceeds from exercise of stock options (in shares)	(152,793)	98,807
Tax benefit related to equity award activity	503				503
Stock based compensation	2,462				2,462
Restricted stock awards issued, net of awards surrendered	(669)				(670)
Stock Issued During Period, Shares, Restricted Stock Award, Net of Shares Surrendered		1,000
Restricted stock awards issued, net of awards surrendered (in shares)		86,331
Shares issued under direct stock purchase plan	969				969
Shares issued under direct stock purchase plan (in shares)		28,187
Deferred compensation obligation			(225)	225
Tax benefit related to deferred compensation distributions	109				109
Ending balance at Dec. 31, 2013	$ 591,540	$ 235	$ (3,404)	$ 3,404	$ 305,179	$ 293,560	$ (7,434)
Ending balance (in shares) at Dec. 31, 2013	23,805,984	23,805,984