CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Common stock	Additional paid-in capital	Accumulated other comprehensive gain (loss)	Retained earnings	Total
Beginning balance, value at Dec. 31, 2016	$ 18	$ 265,264	$ (885)	$ (37,013)	$ 227,384
Beginning balance, shares at Dec. 31, 2016	18,400
Public offering of common	$ 1	21,571			21,572
Public offering of common stock, net, in shares	459
Stock options exercised, net of shares withheld for employee tax, value		(4,930)			(4,930)
Stock options exercised, net of shares withheld for employee tax, in shares	356
Issuance of restricted stock, net of shares withheld for employee tax, value		(2,161)			(2,161)
Issuance of restricted stock, net of shares withheld for employee tax, in shares	144
Share-based compensation		5,849			5,849
Cumulative effect of previously unrecognized tax benefits				1,207	1,207
Foreign currency translation adjustment			7,285		7,285
Other		7		(6)	1
Net income				68,235	68,235
Ending balance, value at Sep. 30, 2017	$ 19	285,600	6,400	32,423	324,442
Ending balance, shares at Sep. 30, 2017	19,359
Beginning balance, value at Jun. 30, 2017	$ 19	290,067	4,369	13,047	307,502
Beginning balance, shares at Jun. 30, 2017	19,192
Stock options exercised, net of shares withheld for employee tax, value		(4,753)			(4,753)
Stock options exercised, net of shares withheld for employee tax, in shares	93
Issuance of restricted stock, net of shares withheld for employee tax, value		(1,795)			(1,795)
Issuance of restricted stock, net of shares withheld for employee tax, in shares	74
Share-based compensation		2,081			2,081
Foreign currency translation adjustment			2,032		2,032
Other			(1)	1
Net income				19,375	19,375
Ending balance, value at Sep. 30, 2017	$ 19	285,600	6,400	32,423	324,442
Ending balance, shares at Sep. 30, 2017	19,359
Beginning balance, value at Dec. 31, 2017	$ 19	285,376	9,743	38,138	333,276
Beginning balance, shares at Dec. 31, 2017	19,451
Stock options exercised, net of shares withheld for employee tax, value		(2,073)			(2,073)
Stock options exercised, net of shares withheld for employee tax, in shares	121
Issuance of restricted stock, net of shares withheld for employee tax, value	$ 1	(1,595)			(1,594)
Issuance of restricted stock, net of shares withheld for employee tax, in shares	186
Share-based compensation		8,362			8,362
Foreign currency translation adjustment			(8,908)		(8,908)
Net income				6,422	6,422
Ending balance, value at Sep. 30, 2018	$ 20	290,070	835	44,560	335,485
Ending balance, shares at Sep. 30, 2018	19,758
Beginning balance, value at Jun. 30, 2018	$ 20	288,686	5,633	48,292	342,631
Beginning balance, shares at Jun. 30, 2018	19,634
Stock options exercised, net of shares withheld for employee tax, value		(845)			(845)
Stock options exercised, net of shares withheld for employee tax, in shares	43
Issuance of restricted stock, net of shares withheld for employee tax, value		(665)			(665)
Issuance of restricted stock, net of shares withheld for employee tax, in shares	81
Share-based compensation		2,894			2,894
Foreign currency translation adjustment			(4,798)		(4,798)
Net income				(3,732)	(3,732)
Ending balance, value at Sep. 30, 2018	$ 20	$ 290,070	$ 835	$ 44,560	$ 335,485
Ending balance, shares at Sep. 30, 2018	19,758