Consolidated Statements of Stockholders' Equity (USD $) In Thousands, except Share data	Total USD ($)	Common Stock Outstanding	Common Stock USD ($)	Value of Shares Held in Rabbi Trust at Cost USD ($)	Deferred Compensation Obligation USD ($)	Additional Paid in Capital USD ($)	Retained Earnings USD ($)	Accumulated Other Comprehensive Loss USD ($)
Beginning balance at Dec. 31, 2011	$ 469,057		$ 213	$ (2,980)	$ 2,980	$ 233,878	$ 239,452	$ (4,486)
Beginning 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 (in shares)		86,254
Restricted stock awards issued, net of awards surrendered	(467)					(467)
Stock Issued During Period, Shares, Other		58,147
Stock Issued During Period, Value, Other	1,691					1,691
Increase (Decrease) in Deferred Compensation				(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
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)		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 (in shares)		86,331
Restricted stock awards issued, net of awards surrendered	(669)		1			(670)
Stock Issued During Period, Shares, Other		28,187
Stock Issued During Period, Value, Other	969					969
Increase (Decrease) in Deferred Compensation				(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
Net income	59,845						59,845
Other comprehensive loss	5,302							5,302
Common dividend declared	(22,961)						(22,961)
Common stock issued for acquisition	0
Proceeds from exercise of stock options, net of cash paid	2,333		1			2,332
Proceeds from exercise of stock options (in shares)		91,171
Tax benefit related to equity award activity	704					704
Stock based compensation	2,712					2,712
Restricted stock awards issued, net of awards surrendered (in shares)		59,675
Restricted stock awards issued, net of awards surrendered	(641)		1			(642)
Stock Issued During Period, Shares, Other		41,908
Stock Issued During Period, Value, Other	1,555					1,555
Increase (Decrease) in Deferred Compensation				(262)	262
Tax benefit related to deferred compensation distributions	138					138
Ending balance at Dec. 31, 2014	$ 640,527		$ 237	$ (3,666)	$ 3,666	$ 311,978	$ 330,444	$ (2,132)
Ending balance (in shares) at Dec. 31, 2014	23,998,738	23,998,738