CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common stock	Additional paid-in capital	Accumulated deficit	Accumulated other comprehensive gain (loss)
Balance (in shares) at Dec. 31, 2018		109,018
Balance at Dec. 31, 2018	$ 1,012,112	$ 109	$ 1,226,588	$ (204,294)	$ (10,291)
Increase (Decrease) in Stockholders' Equity
Net income (loss)	(26,576)			(26,576)
Foreign currency translation adjustment	1,575				1,575
Unrealized gain (loss) on marketable securities, net of tax	48				48
Issuance of common stock upon exercise of options, equity stock and stock units, and employee stock purchase plan (in shares)		1,378
Issuance of common stock upon exercise of options, equity stock and employee stock purchase plan	1,070	$ 1	1,069
Stock-based compensation	7,189		7,189
Cumulative effect adjustment from adoption of new accounting pronouncement | Cumulative effect adjustment from adoption of ASC 842	4,469			4,469
Balance (in shares) at Mar. 31, 2019		110,396
Balance at Mar. 31, 2019	999,887	$ 110	1,234,846	(226,401)	(8,668)
Balance (in shares) at Dec. 31, 2019		112,131
Balance at Dec. 31, 2019	970,918	$ 112	1,261,142	(290,244)	(92)
Increase (Decrease) in Stockholders' Equity
Net income (loss)	(7,983)			(7,983)
Foreign currency translation adjustment	0
Unrealized gain (loss) on marketable securities, net of tax	(96)				(96)
Issuance of common stock upon exercise of options, equity stock and stock units, and employee stock purchase plan (in shares)		1,144
Issuance of common stock upon exercise of options, equity stock and employee stock purchase plan	(3,213)	$ 1	(3,214)
Stock-based compensation	6,072		6,072
Balance (in shares) at Mar. 31, 2020		113,275
Balance at Mar. 31, 2020	$ 965,698	$ 113	$ 1,264,000	$ (298,227)	$ (188)