Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Private Placement	Common Stock	Common Stock Private Placement	Additional Paid-In Capital	Additional Paid-In Capital Private Placement	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Balance at Dec. 31, 2020	$ 236,492		$ 913		$ 1,628,070		$ 257	$ (1,392,748)
Balance (in shares) at Dec. 31, 2020			91,310
Conversion benefit included in Convertible Notes issued	230				230
Issuance of common stock under Employee Stock Purchase Plan	2,139		$ 2		2,137
Issuance of common stock under Employee Stock Purchase Plan (in shares)			175
Issuance of common stock under equity incentive plan	4,926		$ 5		4,921
Issuance of common stock under equity incentive plan (in shares)			476
Issuance of common stock on exercise of warrants			$ 2		(2)
Issuance of common stock on exercise of warrants (in shares)			195
Issuance of common stock on conversion of Convertible Notes	7,878		$ 98		7,780
Issuance of common stock on conversion of notes (in shares)			9,849
Stock-based compensation expense	46,851				46,851
Net loss	(220,683)							(220,683)
Net unrealized gain (loss) on short-term investments	(263)						(263)
Comprehensive loss	(220,946)
Balance at Dec. 31, 2021	77,570		$ 1,020		1,689,987		(6)	(1,613,431)
Balance (in shares) at Dec. 31, 2021			102,005
Issuance of common stock under Employee Stock Purchase Plan	1,444		$ 4		1,440
Issuance of common stock under Employee Stock Purchase Plan (in shares)			407
Issuance of common stock under equity incentive plan	(1,530)		$ 6		(1,536)
Issuance of common stock under equity incentive plan (in shares)			614
Issuance of common stock in a private placement		$ 75,145		$ 161		$ 74,984
Issuance of common stock in a private placement (in shares)				16,129
Stock-based compensation expense	42,980				42,980
Net loss	(182,024)							(182,024)
Net unrealized gain (loss) on short-term investments	(13)						(13)
Comprehensive loss	(182,037)
Balance at Dec. 31, 2022	$ 13,572		$ 1,191		$ 1,807,855		$ (19)	$ (1,795,455)
Balance (in shares) at Dec. 31, 2022			119,155