Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	ASU 2020-06	Common Stock [Member]	Additional Paid-In Capital [Member]	Additional Paid-In Capital [Member] ASU 2020-06	Accumulated Other Comprehensive (Loss) Gain [Member]	Accumulated Deficit [Member]	Accumulated Deficit [Member] ASU 2020-06
BALANCE at Dec. 31, 2018	$ 1,032,276		$ 7	$ 2,611,294		$ (99)	$ (1,578,926)
BALANCE (in shares) at Dec. 31, 2018			71,072,000
Exercise of options for common stock	31,522			31,522
Exercise of options for common stock, shares			1,125,000
Grant of restricted stock awards and vest of restricted stock units, net of cancellations, shares			68,000
Shares withheld for taxes	(9,135)			(9,135)
Shares withheld for taxes, shares			(78,000)
Issuance of common stock for cash, net of offering costs	365,354		$ 1	365,353
Issuance of common stock for cash, net of offering costs, shares			2,604,000
Issuance of common stock for collaboration agreement	29,415			29,415
Issuance of common stock for collaboration agreement, shares			302,000
Issuance of common stock under employee stock purchase plan	5,079			5,079
Issuance of common stock under employee stock purchase plan, shares			92,000
Stock-based compensation	78,602			78,602
Unrealized gain (loss) from available-for-sale securities	149					149
Net loss	(715,075)						(715,075)
BALANCE at Dec. 31, 2019	818,187		$ 8	3,112,130		50	(2,294,001)
BALANCE (in shares) at Dec. 31, 2019			75,185,000
Exercise of options for common stock	76,492			76,492
Exercise of options for common stock, shares			1,443,000
Vest of restricted stock units/awards, net of forfeitures			159,000
Shares withheld for taxes	(6,333)			(6,333)
Shares withheld for taxes, shares			(37,000)
Issuance of common stock for cash, net of offering costs	312,053			312,053
Issuance of common stock for cash, net of offering costs, shares			2,522,000
Issuance of common stock under employee stock purchase plan	7,465			7,465
Issuance of common stock under employee stock purchase plan, shares			102,000
Stock-based compensation	108,070			108,070
Unrealized gain (loss) from available-for-sale securities	(47)					(47)
Net loss	(554,128)						(554,128)
BALANCE at Dec. 31, 2020	761,759	$ (96,792)	$ 8	3,609,877	$ (156,953)	3	(2,848,129)	$ 60,161
BALANCE (in shares) at Dec. 31, 2020			79,374,000
Exercise of options for common stock	$ 12,963			12,963
Exercise of options for common stock, shares	283,622		283,000
Vest of restricted stock units/awards, net of forfeitures			277,000
Shares withheld for taxes	$ (1,432)			(1,432)
Shares withheld for taxes, shares			(18,000)
Issuance of common stock for cash, net of offering costs	548,532		$ 1	548,531
Issuance of common stock for cash, net of offering costs, shares			7,099,000
Issuance of common stock under employee stock purchase plan	7,839			7,839
Issuance of common stock under employee stock purchase plan, shares			112,000
Stock-based compensation	113,943			113,943
Unrealized gain (loss) from available-for-sale securities	(23)					(23)
Net loss	(418,780)						(418,780)
BALANCE at Dec. 31, 2021	$ 928,009		$ 9	$ 4,134,768		$ 20	$ (3,206,748)
BALANCE (in shares) at Dec. 31, 2021			87,127,000