CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance at Dec. 31, 2018	$ 522,801	$ 42	$ 1,218,710	$ 3	$ (695,954)
Beginning balance (shares) at Dec. 31, 2018		42,078
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(419,503)				(419,503)
Other comprehensive income (loss)	376			376
Issuance of common stock, net of issuance costs	42,576	$ 1	42,575
Issuance of common stock, net of issuance costs (shares)		904
Issuance of common stock under employee equity plans	10,182		10,182
Issuance of common stock under employee equity plans (shares)		712
Shares repurchased for tax withholdings related to net share settlement of employee equity awards	(744)		(744)
Shares repurchased for tax withholdings related to net share settlement of employee equity awards (shares)		(17)
Issuance of common stock in connection with asset acquisition	68,124	$ 2	68,122
Issuance of common stock in connection with asset acquisition (shares)		1,595
Stock-based compensation	21,247		21,247
Ending balance at Dec. 31, 2019	245,059	$ 45	1,360,092	379	(1,115,457)
Ending balance (shares) at Dec. 31, 2019		45,272
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(209,383)				(209,383)
Other comprehensive income (loss)	(450)			(450)
Issuance of common stock, net of issuance costs	226,576	$ 10	226,566
Issuance of common stock, net of issuance costs (shares)		10,000
Equity component of convertible debt	75,333		75,333
Issuance of common stock under employee equity plans	5,515	$ 1	5,514
Issuance of common stock under employee equity plans (shares)		546
Shares repurchased for tax withholdings related to net share settlement of employee equity awards	(2,157)		(2,157)
Shares repurchased for tax withholdings related to net share settlement of employee equity awards (shares)		(82)
Stock-based compensation	29,176		29,176
Ending balance at Dec. 31, 2020	369,669	$ 56	1,694,524	(71)	(1,324,840)
Ending balance (shares) at Dec. 31, 2020		55,736
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(227,413)				(227,413)
Other comprehensive income (loss)	86			86
Issuance of common stock under employee equity plans	1,962	$ 0	1,962
Issuance of common stock under employee equity plans (shares)		466
Shares repurchased for tax withholdings related to net share settlement of employee equity awards	(1,788)		(1,788)
Shares repurchased for tax withholdings related to net share settlement of employee equity awards (shares)		(107)
Stock-based compensation	36,455		36,455
Ending balance at Dec. 31, 2021	$ 178,971	$ 56	$ 1,731,153	$ 15	$ (1,552,253)
Ending balance (shares) at Dec. 31, 2021		56,095