Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Common stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income	Accumulated Deficit	Total
Balance at Dec. 31, 2020	$ 9	$ 1,411,286	$ 4,259	$ (929,318)	$ 486,236
Balance (in shares) at Dec. 31, 2020	86,223
Issuance of common stock upon exercise of stock options		6,829			6,829
Issuance of common stock upon exercise of stock options (in shares)	782
Issuance of common stock under employee stock purchase plan		6,085			6,085
Issuance of common stock under employee stock purchase plan (in shares)	106
Vesting of restricted stock units (in shares)	1,387
Stock based compensation		58,335			58,335
Unrealized gain (loss) on available-for sale securities			(1,818)		(1,818)
Cumulative-effect adjustment upon adoption of ASU 2020-06		(82,876)		6,198	(76,678)
Net loss				(179,879)	(179,879)
Balance at Jun. 30, 2021	$ 9	1,399,659	2,441	(1,102,999)	299,110
Balance (in shares) at Jun. 30, 2021	88,498
Balance at Mar. 31, 2021	$ 9	1,356,212	3,197	(986,973)	372,445
Balance (in shares) at Mar. 31, 2021	87,430
Issuance of common stock upon exercise of stock options		2,259			2,259
Issuance of common stock upon exercise of stock options (in shares)	207
Issuance of common stock under employee stock purchase plan		6,085			6,085
Issuance of common stock under employee stock purchase plan (in shares)	106
Vesting of restricted stock units (in shares)	755
Stock based compensation		35,103			35,103
Unrealized gain (loss) on available-for sale securities			(756)		(756)
Net loss				(116,026)	(116,026)
Balance at Jun. 30, 2021	$ 9	1,399,659	2,441	(1,102,999)	299,110
Balance (in shares) at Jun. 30, 2021	88,498
Balance at Dec. 31, 2021	$ 10	2,050,417	(2,287)	(1,394,836)	$ 653,304
Balance (in shares) at Dec. 31, 2021	95,140				95,140
Issuance of common stock upon exercise of stock options		4,578			$ 4,578
Issuance of common stock upon exercise of stock options (in shares)	701
Issuance of common stock under employee stock purchase plan		8,496			8,496
Issuance of common stock under employee stock purchase plan (in shares)	285
Vesting of restricted stock units (in shares)	777
Stock based compensation		76,060			76,060
Unrealized gain (loss) on available-for sale securities			(14,110)		(14,110)
Net loss				(283,746)	(283,746)
Balance at Jun. 30, 2022	$ 10	2,139,551	(16,397)	(1,678,582)	$ 444,582
Balance (in shares) at Jun. 30, 2022	96,903				96,903
Balance at Mar. 31, 2022	$ 10	2,089,660	(13,904)	(1,533,431)	$ 542,335
Balance (in shares) at Mar. 31, 2022	96,259
Issuance of common stock upon exercise of stock options		422			422
Issuance of common stock upon exercise of stock options (in shares)	70
Issuance of common stock under employee stock purchase plan		8,496			8,496
Issuance of common stock under employee stock purchase plan (in shares)	285
Vesting of restricted stock units (in shares)	289
Stock based compensation		40,973			40,973
Unrealized gain (loss) on available-for sale securities			(2,493)		(2,493)
Net loss				(145,151)	(145,151)
Balance at Jun. 30, 2022	$ 10	$ 2,139,551	$ (16,397)	$ (1,678,582)	$ 444,582
Balance (in shares) at Jun. 30, 2022	96,903				96,903