Unaudited Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common stock	Additional paid-in capital	Accumulated other comprehensive income (loss)	Accumulated deficit
Beginning balance (in shares) at Dec. 31, 2019		91,749,933
Beginning balance at Dec. 31, 2019	$ 93,532	$ 92	$ 310,621	$ (449)	$ (216,732)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	12,883		12,883
Common stock issued under employee stock plans, net (in shares)		2,648,877
Common stock issued under employee stock plans, net	4,316	$ 2	4,314
Realized and unrealized income (loss) on derivative instruments	545			545
Unrealized income (loss) on available for sale securities	195			195
Net loss	(31,430)				(31,430)
Ending balance (in shares) at Mar. 31, 2020		94,398,810
Ending balance at Mar. 31, 2020	80,041	$ 94	327,818	291	(248,162)
Beginning balance (in shares) at Dec. 31, 2019		91,749,933
Beginning balance at Dec. 31, 2019	93,532	$ 92	310,621	(449)	(216,732)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Realized and unrealized income (loss) on derivative instruments	4,112
Unrealized income (loss) on available for sale securities	2
Net loss	(74,978)
Ending balance (in shares) at Sep. 30, 2020		95,175,942
Ending balance at Sep. 30, 2020	82,920	$ 95	370,870	3,665	(291,710)
Beginning balance (in shares) at Mar. 31, 2020		94,398,810
Beginning balance at Mar. 31, 2020	80,041	$ 94	327,818	291	(248,162)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	17,623		17,623
Common stock issued under employee stock plans, net (in shares)		231,747
Common stock issued under employee stock plans, net	498	$ 1	497
Realized and unrealized income (loss) on derivative instruments	3,367			3,367
Unrealized income (loss) on available for sale securities	(122)			(122)
Purchase of capped calls related to Convertible senior notes	(29,348)		(29,348)
Equity component of Convertible senior notes, net	30,794		30,794
Net loss	(24,323)				(24,323)
Ending balance (in shares) at Jun. 30, 2020		94,630,557
Ending balance at Jun. 30, 2020	78,530	$ 95	347,384	3,536	(272,485)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	18,678		18,678
Common stock issued under employee stock plans, net (in shares)		545,385
Common stock issued under employee stock plans, net	4,808	$ 0	4,808
Realized and unrealized income (loss) on derivative instruments	200			200
Unrealized income (loss) on available for sale securities	(71)			(71)
Net loss	(19,225)				(19,225)
Ending balance (in shares) at Sep. 30, 2020		95,175,942
Ending balance at Sep. 30, 2020	82,920	$ 95	370,870	3,665	(291,710)
Beginning balance (in shares) at Dec. 31, 2020		95,456,862
Beginning balance at Dec. 31, 2020	94,071	$ 95	395,347	9,371	(310,742)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Common stock in connection with follow-on offering, net of issuance costs of $17,466 (in shares)		7,961,538
Issuance of Common stock in connection with follow-on offering, net of issuance costs of $17,466	500,034	$ 8	500,026
Stock-based compensation expense	21,379		21,379
Common stock issued under employee stock plans, net (in shares)		2,728,995
Common stock issued under employee stock plans, net	3,942	$ 3	3,939
Realized and unrealized income (loss) on derivative instruments	(5,185)			(5,185)
Unrealized income (loss) on available for sale securities	5			5
Net loss	(35,656)				(35,656)
Ending balance (in shares) at Mar. 31, 2021		106,147,395
Ending balance at Mar. 31, 2021	578,590	$ 106	920,691	4,191	(346,398)
Beginning balance (in shares) at Dec. 31, 2020		95,456,862
Beginning balance at Dec. 31, 2020	94,071	$ 95	395,347	9,371	(310,742)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Realized and unrealized income (loss) on derivative instruments	(6,840)
Unrealized income (loss) on available for sale securities	(3)
Net loss	(91,918)
Ending balance (in shares) at Sep. 30, 2021		107,321,063
Ending balance at Sep. 30, 2021	576,970	$ 107	976,995	2,528	(402,660)
Beginning balance (in shares) at Mar. 31, 2021		106,147,395
Beginning balance at Mar. 31, 2021	578,590	$ 106	920,691	4,191	(346,398)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	25,868		25,868
Common stock issued under employee stock plans, net (in shares)		766,636
Common stock issued under employee stock plans, net	(26)	$ 1	(27)
Realized and unrealized income (loss) on derivative instruments	(1,092)			(1,092)
Unrealized income (loss) on available for sale securities	(6)			(6)
Net loss	(32,948)				(32,948)
Ending balance (in shares) at Jun. 30, 2021		106,914,031
Ending balance at Jun. 30, 2021	570,386	$ 107	946,532	3,093	(379,346)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	24,422		24,422
Common stock issued under employee stock plans, net (in shares)		407,032
Common stock issued under employee stock plans, net	6,041	$ 0	6,041
Realized and unrealized income (loss) on derivative instruments	(563)			(563)
Unrealized income (loss) on available for sale securities	(2)			(2)
Net loss	(23,314)				(23,314)
Ending balance (in shares) at Sep. 30, 2021		107,321,063
Ending balance at Sep. 30, 2021	$ 576,970	$ 107	$ 976,995	$ 2,528	$ (402,660)