Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock Outstanding	Common Stock	Value of Shares Held in Rabbi Trust at Cost	Deferred Compensation Obligation	Additional Paid in Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Common Stock, Dividends, Per Share, Declared							$ 0.96
Beginning balance at Dec. 31, 2013	$ 591,540		$ 235	$ (3,404)	$ 3,404	$ 305,179	$ 293,560	$ (7,434)
Beginning balance (in shares) at Dec. 31, 2013		23,805,984
Net income	59,845						59,845
Other comprehensive income	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 (in shares) at Dec. 31, 2014		23,998,738
Ending balance at Dec. 31, 2014	640,527		237	(3,666)	3,666	311,978	$ 330,444	(2,132)
Common Stock, Dividends, Per Share, Declared							$ 1.04
Net income	64,960						$ 64,960
Other comprehensive income	(320)							(320)
Common dividend declared	(27,235)						(27,235)
Common stock issued for acquisition	86,415		21			86,394
Common stock issued for acquisition (in shares)		2,052,137
Proceeds from exercise of stock options, net of cash paid	1,367		1			1,366
Proceeds from exercise of stock options (in shares)		100,794
Tax benefit related to equity award activity	1,042					1,042
Stock based compensation	2,490					2,490
Restricted stock awards issued, net of awards surrendered (in shares)		23,851
Restricted stock awards issued, net of awards surrendered	(657)		1			(658)
Stock Issued During Period, Shares, Other		60,832
Stock Issued During Period, Value, Other	2,695					2,695
Increase (Decrease) in Deferred Compensation	0			(292)	292
Tax benefit related to deferred compensation distributions	179					179
Ending balance (in shares) at Dec. 31, 2015		26,236,352
Ending balance at Dec. 31, 2015	771,463		260	(3,958)	3,958	405,486	$ 368,169	(2,452)
Common Stock, Dividends, Per Share, Declared							$ 1.16
Net income	76,648						$ 76,648
Other comprehensive income	1,115							1,115
Common dividend declared	(30,722)						(30,722)
Common stock issued for acquisition	40,730		7			40,723
Common stock issued for acquisition (in shares)		672,665
Proceeds from exercise of stock options, net of cash paid	201					201
Proceeds from exercise of stock options (in shares)		13,449
Tax benefit related to equity award activity	476					476
Stock based compensation	2,965					2,965
Restricted stock awards issued, net of awards surrendered (in shares)		33,432
Restricted stock awards issued, net of awards surrendered	(696)		1			(697)
Stock Issued During Period, Shares, Other		49,915
Stock Issued During Period, Value, Other	2,323					2,323
Increase (Decrease) in Deferred Compensation and Other Retirement Benefits				(319)	319
Tax benefit related to deferred compensation distributions	187					187
Ending balance (in shares) at Dec. 31, 2016		27,005,813
Ending balance at Dec. 31, 2016	$ 864,690		$ 268	$ (4,277)	$ 4,277	$ 451,664	$ 414,095	$ (1,337)