CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Common stock	Contributed capital	Accumulated deficit	Treasury stock	Accumulated other comprehensive (loss) income
Beginning Balance (shares) at Dec. 31, 2018		54,232,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of options (shares)		215,000
Issuance of common stock under employee purchase plan (shares)		7,000
Ending Balance (shares) at Mar. 31, 2019		54,454,000
Beginning Balance, amount at Dec. 31, 2018		$ 54	$ 432,885	$ (330,348)	$ (45,067)	$ (149)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of options			3,677
Issuance of common stock under employee purchase plan			139
Equity-based compensation			3,453
Net loss	$ (21,721)			(21,721)
Unrealized loss on available-for-sale securities	121					121
Foreign currency translation adjustment	(76)					(76)
Ending Balance, amount at Mar. 31, 2019	$ 42,968	$ 54	440,154	(352,069)	(45,067)	(104)
Beginning Balance (shares) at Dec. 31, 2019		54,709,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of options (shares)	266,725	270,000
Issuance of common stock under employee purchase plan (shares)		15,000
Ending Balance (shares) at Mar. 31, 2020		54,994,000
Beginning Balance, amount at Dec. 31, 2019	$ (7,379)	$ 55	452,344	(414,653)	(45,067)	(58)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of options			1,318
Issuance of common stock under employee purchase plan			111
Equity-based compensation			4,214
Net loss	(21,309)			(21,309)
Unrealized loss on available-for-sale securities	223					223
Foreign currency translation adjustment	(15)					(15)
Ending Balance, amount at Mar. 31, 2020	$ (22,942)	$ 55	$ 457,987	(436,067)	$ (45,067)	$ 150
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative impact of accounting change				$ (105)