CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Balances at Dec. 31, 2017	$ 50,156	$ 81	$ 128,798	$ 194	$ (78,917)
Balances, shares at Dec. 31, 2017		81,043
Exercise of stock options and common stock issued upon vesting of equity awards, net of shares withheld for employee taxes	10,147	$ 5	10,142
Exercise of stock options and common stock issued upon vesting of equity awards, net of shares withheld for employee taxes, shares		5,180
Foreign currency translation adjustment, net of tax	(503)			(503)
Follow-on offering selling shareholders profit disgorgement, net of offering costs	3,770		3,770
Stock-based compensation	4,501		4,501
Net (loss) income	39,193				39,193
Balances at Jun. 30, 2018	107,264	$ 86	147,211	(309)	(39,724)
Balances, shares at Jun. 30, 2018		86,223
Balances at Mar. 31, 2018	71,833	$ 82	131,536	1,356	(61,141)
Balances, shares at Mar. 31, 2018		81,801
Exercise of stock options and common stock issued upon vesting of equity awards, net of shares withheld for employee taxes	9,472	$ 4	9,468
Exercise of stock options and common stock issued upon vesting of equity awards, net of shares withheld for employee taxes, shares		4,422
Foreign currency translation adjustment, net of tax	(1,665)			(1,665)
Follow-on offering selling shareholders profit disgorgement, net of offering costs	3,770		3,770
Stock-based compensation	2,437		2,437
Net (loss) income	21,417				21,417
Balances at Jun. 30, 2018	107,264	$ 86	147,211	(309)	(39,724)
Balances, shares at Jun. 30, 2018		86,223
Balances at Dec. 31, 2018	74,856	$ 83	156,939	(1,158)	(81,008)
Balances, shares at Dec. 31, 2018		82,961
Exercise of stock options and common stock issued upon vesting of equity awards, net of shares withheld for employee taxes	1,164	$ 1	1,163
Exercise of stock options and common stock issued upon vesting of equity awards, net of shares withheld for employee taxes, shares		1,067
Foreign currency translation adjustment, net of tax	67			67
Effect of adopted accounting standards (Note 2)	2,150				2,150
Stock-based compensation	5,424		5,424
Net (loss) income	(14,048)				(14,048)
Balances at Jun. 30, 2019	69,613	$ 84	163,526	(1,091)	(92,906)
Balances, shares at Jun. 30, 2019		84,028
Balances at Mar. 31, 2019	65,434	$ 84	159,992	(445)	(94,197)
Balances, shares at Mar. 31, 2019		83,734
Exercise of stock options and common stock issued upon vesting of equity awards, net of shares withheld for employee taxes	670		670
Exercise of stock options and common stock issued upon vesting of equity awards, net of shares withheld for employee taxes, shares		294
Foreign currency translation adjustment, net of tax	(646)			(646)
Stock-based compensation	2,864		2,864
Net (loss) income	1,291				1,291
Balances at Jun. 30, 2019	$ 69,613	$ 84	$ 163,526	$ (1,091)	$ (92,906)
Balances, shares at Jun. 30, 2019		84,028