Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Common Stock Follow-on Public Offering and At-the-market Offering	Common Stock Private Placement	Common Stock	Additional Paid-In Capital Follow-on Public Offering and At-the-market Offering	Additional Paid-In Capital Private Placement	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit	Follow-on Public Offering and At-the-market Offering	Private Placement	Total
Beginning Balance at Dec. 31, 2018			$ 44			$ 1,016,689	$ (180)	$ (597,544)			$ 419,009
Beginning Balance (in shares) at Dec. 31, 2018			44,037,026
Increase (Decrease) in Stockholders' Equity
Issuance of common stock under stock plan			$ 1			12,130					12,131
Issuance of common stock under stock plan (in shares)			552,311
Purchase of common stock under ESPP						1,148					$ 1,148
Purchase of common stock under ESPP (in shares)			20,724								20,724
Stock-based compensation expense						54,653					$ 54,653
Issuance of common stock	$ 4			$ 327,462					$ 327,466
Issuance of common stock (in shares)	4,662,162
Other comprehensive income (loss)							(2,354)				(2,354)
Net income (loss)								(347,694)			(347,694)
Ending Balance at Dec. 31, 2019			$ 49			1,412,082	(2,534)	(945,238)			464,359
Ending Balance (in shares) at Dec. 31, 2019			49,272,223
Increase (Decrease) in Stockholders' Equity
Issuance of common stock under stock plan			$ 1			33,282					33,283
Issuance of common stock under stock plan (in shares)			952,205
Purchase of common stock under ESPP			$ 1			2,153					$ 2,154
Purchase of common stock under ESPP (in shares)			38,516								38,516
Stock-based compensation expense						76,602					$ 76,602
Issuance of common stock	$ 6	$ 1		$ 503,176	$ 79,305				$ 503,182	$ 79,306
Issuance of common stock (in shares)	6,495,070	1,035,519
Other comprehensive income (loss)							(2,680)				(2,680)
Net income (loss)								313,882			313,882
Ending Balance at Dec. 31, 2020			$ 58			2,106,600	(5,214)	(631,356)			$ 1,470,088
Ending Balance (in shares) at Dec. 31, 2020			57,793,533								57,793,533
Increase (Decrease) in Stockholders' Equity
Issuance of common stock under stock plan			$ 1			47,302					$ 47,303
Issuance of common stock under stock plan (in shares)			1,304,386
Purchase of common stock under ESPP						3,313					$ 3,313
Purchase of common stock under ESPP (in shares)			43,167								43,167
Stock-based compensation expense						93,035					$ 93,035
Other comprehensive income (loss)							1,081				1,081
Net income (loss)								(644,085)			(644,085)
Ending Balance at Dec. 31, 2021			$ 59			$ 2,250,250	$ (4,133)	$ (1,275,441)			$ 970,735
Ending Balance (in shares) at Dec. 31, 2021			59,141,086								59,141,086