CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Retained Earnings [Member]	Non-Controlling Interest [Member]	Total
Balances at Dec. 31, 2014	$ 2	$ 154,894	$ (5,677)	$ 291,978	$ 789	$ 441,986
Balances, Shares at Dec. 31, 2014	20,788,000
Net income				26,601	134	26,735
Foreign currency translation adjustment			(2,245)			(2,245)
Repurchase of common stock		(12,997)				(12,997)
Repurchase of common stock, Shares	(1,089,000)
Exercise of stock options		4,744				4,744
Exercise of stock options, Shares	415,000
Stock based compensation - options		1,542				1,542
Stock based compensation - restricted stock		373				373
Stock based compensation - restricted stock, Shares	21,000
Excess tax benefit from share-based compensation awards		3				3
Payment of income tax withheld on vested restricted stock		(36)				(36)
Payment of income tax withheld on vested restricted stock, Shares	(2,000)
Balances at Dec. 31, 2015	$ 2	148,523	(7,922)	318,579	923	460,105
Balances, Shares at Dec. 31, 2015	20,133,000
Net income				5,997	37	6,034
Foreign currency translation adjustment			(815)			(815)
Disposal of subsidiary			605		$ (960)	(355)
Repurchase of common stock		(9,176)				(9,176)
Repurchase of common stock, Shares	(1,104,000)
Stock based compensation - options		1,292				1,292
Stock based compensation - restricted stock		440				440
Stock based compensation - restricted stock, Shares	31,000
Payment of income tax withheld on vested restricted stock		(21)				(21)
Payment of income tax withheld on vested restricted stock, Shares	(3,000)
Balances at Dec. 31, 2016	$ 2	141,058	(8,132)	324,576		$ 457,504
Balances, Shares at Dec. 31, 2016	19,057,000					19,057,217
Net income				72,060		$ 72,060
Adoption of ASU 2016-09 (Note 2(p))				1,004		1,004
Foreign currency translation adjustment			2,010			2,010
Issuance of common stock, net of offering costs		29,148				29,148
Issuance of common stock, net of offering costs, Shares	889,000
Exercise of stock options		145				145
Exercise of stock options, Shares	414,000
Stock based compensation - options		1,593				1,593
Stock based compensation - restricted stock		494				494
Stock based compensation - restricted stock, Shares	37,000
Payment of income tax withheld on vested restricted stock		(113)				(113)
Payment of income tax withheld on vested restricted stock, Shares	(6,000)
Balances at Dec. 31, 2017	$ 2	$ 172,325	$ (6,122)	$ 397,640		$ 563,845
Balances, Shares at Dec. 31, 2017	20,391,000					20,390,622