Consolidated Statements of Stockholders Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance, Shares at Dec. 31, 2013		15,102,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of restricted stock and exercise of stock options, shares issued		544,000
Treasury Stock, Shares		(98,000)
Employee stock purchase plan, shares issued		47,000
Balance, Shares at Dec. 31, 2014		15,595,000
Balance at Dec. 31, 2013	$ 464,725	$ 1,510	$ 78,495	$ (49)	$ 382,576	$ 2,193
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of restricted stock and exercise of stock options, including excess income tax benefits	22,698	48	18,528	4,122
Purchase of treasury stock,treasury stock acquired in lieu of cash payment on stock option exercises and income tax withholding obligations	(5,836)		(285)	(6,121)
Proceeds from employee stock purchase plan	2,485	1	436	2,048
Stock compensation	9,592		9,592
Foreign Currency Translation Adjustment	(11,747)					(11,747)
Net Income	26,335				26,335
Balance at Dec. 31, 2014	$ 508,252	$ 1,559	107,336	0	408,911	(9,554)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of restricted stock and exercise of stock options, shares issued		475,000
Treasury Stock, Shares		(18,000)
Employee stock purchase plan, shares issued		34,000
Balance, Shares at Dec. 31, 2015	16,086,000	16,086,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of restricted stock and exercise of stock options, including excess income tax benefits	$ 24,372	$ 46	22,715	1,611
Purchase of treasury stock,treasury stock acquired in lieu of cash payment on stock option exercises and income tax withholding obligations	(1,523)		(88)	(1,611)
Proceeds from employee stock purchase plan	2,162	3	2,159	0
Stock compensation	12,827		12,827
Foreign Currency Translation Adjustment	(11,204)					(11,204)
Net Income	44,985				44,985
Balance at Dec. 31, 2015	$ 579,871	$ 1,608	145,125	0	453,896	(20,758)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of restricted stock and exercise of stock options, shares issued		416,000
Treasury Stock, Shares		(195,000)
Employee stock purchase plan, shares issued		31,000
Balance, Shares at Dec. 31, 2016	16,337,670	16,338,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of restricted stock and exercise of stock options, including excess income tax benefits	$ 17,346	$ 22	103	17,221
Purchase of treasury stock,treasury stock acquired in lieu of cash payment on stock option exercises and income tax withholding obligations	(17,235)		0	(17,235)
Proceeds from employee stock purchase plan	2,361	3	2,358	0
Stock compensation	15,242		15,242
Foreign Currency Translation Adjustment	(514)					(514)
Net Income	63,084				63,084
Balance at Dec. 31, 2016	$ 660,155	$ 1,633	$ 162,828	$ (14)	$ 516,980	$ (21,272)