CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Cumulative effect, period of adoption, adjustment	Common stock	Additional paid-in capital	Accumulated deficit	Accumulated deficit Cumulative effect, period of adoption, adjustment	Accumulated other comprehensive gain (loss)
Balance (in shares) at Dec. 31, 2017			109,764,000
Balance at Dec. 31, 2017	$ 571,584		$ 110	$ 1,212,798	$ (636,227)		$ (5,097)
Increase (Decrease) in Stockholders' Equity
Net income (loss)	(157,957)				(157,957)
Foreign currency translation adjustment	(4,447)						(4,447)
Unrealized gain (loss) on marketable securities, net of tax	(747)						(747)
Issuance of common stock upon exercise of options, equity stock and stock units, and employee stock purchase plan (in shares)			2,616,000
Issuance of common stock upon exercise of options, equity stock and employee stock purchase plan	4,630		$ 3	4,627
Repurchase and retirement of common stock under repurchase plan, shares			(3,786,000)
Repurchase and retirement of common stock under repurchase plan, value	(50,033)		$ (4)	(12,573)	(37,456)
Stock-based compensation	21,736			21,736
Issuance of common stock in connection with the maturity of the 2018 Notes related to the settlement of the in-the-money conversion feature of the 2018 Notes			424,000
Balance (in shares) at Dec. 31, 2018			109,018,000
Balance at Dec. 31, 2018	1,012,112		$ 109	1,226,588	(204,294)		(10,291)
Balance (Accounting Standards Update 2016-01) at Dec. 31, 2018		$ 1,058				$ 1,058
Balance (Accounting Standards Update 2014-09) at Dec. 31, 2018		626,288				626,288
Increase (Decrease) in Stockholders' Equity
Net income (loss)	(90,419)				(90,419)
Foreign currency translation adjustment	10,145						10,145
Unrealized gain (loss) on marketable securities, net of tax	54						54
Issuance of common stock upon exercise of options, equity stock and stock units, and employee stock purchase plan (in shares)			3,113,000
Issuance of common stock upon exercise of options, equity stock and employee stock purchase plan	8,081		$ 3	8,078
Stock-based compensation	26,476			26,476
Balance (in shares) at Dec. 31, 2019			112,131,000
Balance at Dec. 31, 2019	970,918		$ 112	1,261,142	(290,244)		(92)
Balance (Accounting Standards Update 2016-02) at Dec. 31, 2019		$ 4,469				$ 4,469
Increase (Decrease) in Stockholders' Equity
Net income (loss)	(43,609)				(43,609)
Foreign currency translation adjustment	24						24
Unrealized gain (loss) on marketable securities, net of tax	(13)						(13)
Issuance of common stock upon exercise of options, equity stock and stock units, and employee stock purchase plan (in shares)			2,183,000
Issuance of common stock upon exercise of options, equity stock and employee stock purchase plan	2,084		$ 3	2,081
Repurchase and retirement of common stock under repurchase plan, shares			(2,616,000)
Repurchase and retirement of common stock under repurchase plan, value	(50,069)		$ (3)	(18,575)	(31,491)
Stock-based compensation	25,778			25,778
Balance (in shares) at Dec. 31, 2020			111,698,000
Balance at Dec. 31, 2020	$ 905,113		$ 112	$ 1,270,426	$ (365,344)		$ (81)