CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Retained Earnings [Mmember]
Balance at Dec. 31, 2015	$ 270,678	$ 31	$ 394,928	$ (2,623)	$ (121,658)
Balance, Shares at Dec. 31, 2015		30,949
Issuance of shares through share-based compensation plans, net	850		850
Issuance of shares through share-based compensation plans, net, Shares		713
Repurchase of common stock	(8,044)		(8,044)
Repurchase of common stock, Shares		(615)
Net income	36,952				36,952
Share-based compensation	4,775		4,775
Tax benefit for share-based compensation plans	792		792
Share-based compensation plan withholdings	(1,587)		(1,587)
Redemption of stock warrants, shares		80
Redemption of stock warrants	(10,525)		(10,525)
Currency translation	(119)			(119)
Unrealized gain (loss) on investments	(37)			(37)
Balance at Dec. 31, 2016	293,735	$ 31	381,189	(2,779)	(84,706)
Balance, shares at Dec. 31, 2016		31,127
Redemption of stock warrants	10,525		10,525
Issuance of shares through share-based compensation plans, net	624	$ 1	623
Issuance of shares through share-based compensation plans, net, Shares		375
Net income	32,909				32,909
Share-based compensation	5,670		5,670
Cumulative effect of a change in accountingfor share-based compensation			72		(72)
Share-based compensation plan withholdings	(1,358)		(1,358)
Redemption of stock warrants, shares		102
Currency translation	1,663			1,663
Unrealized gain (loss) on investments	(89)			(89)
Balance at Dec. 31, 2017	333,154	$ 32	386,196	(1,205)	(51,869)
Balance, shares at Dec. 31, 2017		31,604
Issuance of shares through share-based compensation plans, net	624		624
Issuance of shares through share-based compensation plans, net, Shares		363
Repurchase of common stock	(21,069)	$ (1)	(21,068)
Repurchase of common stock, Shares		(1,061)
Net income	45,096				45,096
Share-based compensation	6,062		6,062
Share-based compensation plan withholdings	(1,921)		(1,921)
Currency translation	(194)			(194)
Unrealized gain (loss) on investments	136			136
Balance at Dec. 31, 2018	$ 361,888	$ 31	$ 369,893	$ (1,263)	$ (6,773)
Balance, shares at Dec. 31, 2018		30,906