STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Gain (Loss)	Accumulated Deficit
Balance at Dec. 31, 2020	$ 654,395	$ 53	$ 997,298	$ 8	$ (342,964)
Balance, Shares at Dec. 31, 2020		53,081
Stock-based compensation expense	12,354	$ 0	12,354	0	0
Issuance of common stock upon exercise of stock options	3,788	$ 0	3,788	0	0
Issuance of common stock upon exercise of stock options, Shares		321
Issuance of common stock upon 2018 ESPP purchase	995	$ 0	995	0	0
Issuance of common stock upon 2018 ESPP purchase, Shares		17
Issuance of common stock upon vesting of restricted stock units	0	$ 0	0	0	0
Issuance of common stock upon vesting of restricted stock units, Shares		38
Unrealized gain (loss) on investments	80	$ 0	0	80	0
Net loss	(55,558)	0	0	0	(55,558)
Balance at Mar. 31, 2021	616,054	$ 53	1,014,435	88	(398,522)
Balance, Shares at Mar. 31, 2021		53,457
Balance at Dec. 31, 2020	654,395	$ 53	997,298	8	(342,964)
Balance, Shares at Dec. 31, 2020		53,081
Unrealized gain (loss) on investments	11
Net loss	(175,496)
Balance at Sep. 30, 2021	524,553	$ 54	1,042,940	19	(518,460)
Balance, Shares at Sep. 30, 2021		54,292
Balance at Mar. 31, 2021	616,054	$ 53	1,014,435	88	(398,522)
Balance, Shares at Mar. 31, 2021		53,457
Stock-based compensation expense	11,397	$ 0	11,397	0	0
Issuance of common stock upon exercise of stock options	800	$ 0	800	0	0
Issuance of common stock upon exercise of stock options, Shares		443
Issuance of common stock upon vesting of restricted stock units	0	$ 0	0	0	0
Issuance of common stock upon vesting of restricted stock units, Shares		36
Unrealized gain (loss) on investments	(56)	$ 0	0	(56)	0
Net loss	(57,209)	0	0	0	(57,209)
Balance at Jun. 30, 2021	570,986	$ 53	1,026,632	32	(455,731)
Balance, Shares at Jun. 30, 2021		53,936
Stock-based compensation expense	12,496	$ 0	12,496	0	0
Issuance of common stock upon exercise of stock options	3,040	$ 1	3,039	0	0
Issuance of common stock upon exercise of stock options, Shares		308
Issuance of common stock upon 2018 ESPP purchase	773	$ 0	773	0	0
Issuance of common stock upon 2018 ESPP purchase, Shares		12
Issuance of common stock upon vesting of restricted stock units	0	$ 0	0	0	0
Issuance of common stock upon vesting of restricted stock units, Shares		36
Unrealized gain (loss) on investments	(13)	$ 0	0	(13)	0
Net loss	(62,729)	0	0	0	(62,729)
Balance at Sep. 30, 2021	524,553	$ 54	1,042,940	19	(518,460)
Balance, Shares at Sep. 30, 2021		54,292
Balance at Dec. 31, 2021	445,476	$ 54	1,058,399	(153)	(612,824)
Balance, Shares at Dec. 31, 2021		54,622
Stock-based compensation expense	11,392	$ 0	11,392	0	0
Issuance of common stock upon exercise of stock options	104	$ 0	104	0	0
Issuance of common stock upon exercise of stock options, Shares		34
Issuance of common stock upon 2018 ESPP purchase	243	$ 0	243	0	0
Issuance of common stock upon 2018 ESPP purchase, Shares		42
Issuance of common stock upon vesting of restricted stock units	0	$ 0	0	0	0
Issuance of common stock upon vesting of restricted stock units, Shares		63
Unrealized gain (loss) on investments	(316)	$ 0	0	(316)	0
Net loss	(197,023)	0	0	0	(197,023)
Balance at Mar. 31, 2022	259,876	$ 54	1,070,138	(469)	(809,847)
Balance, Shares at Mar. 31, 2022		54,761
Balance at Dec. 31, 2021	$ 445,476	$ 54	1,058,399	(153)	(612,824)
Balance, Shares at Dec. 31, 2021		54,622
Issuance of common stock upon exercise of stock options, Shares	405
Unrealized gain (loss) on investments	$ 89
Net loss	(276,963)
Balance at Sep. 30, 2022	344,179	$ 85	1,233,945	(64)	(889,787)
Balance, Shares at Sep. 30, 2022		85,193
Balance at Mar. 31, 2022	259,876	$ 54	1,070,138	(469)	(809,847)
Balance, Shares at Mar. 31, 2022		54,761
Stock-based compensation expense	11,761	$ 0	11,761	0	0
Issuance of common stock upon exercise of stock options	66	$ 0	66	0	0
Issuance of common stock upon exercise of stock options, Shares		25
Issuance of common stock upon vesting of restricted stock units	0	$ 0	0	0	0
Issuance of common stock upon vesting of restricted stock units, Shares		58
Unrealized gain (loss) on investments	209	$ 0	0	209	0
Net loss	(49,103)	0	0	0	(49,103)
Balance at Jun. 30, 2022	222,809	$ 54	1,081,965	(260)	(858,950)
Balance, Shares at Jun. 30, 2022		54,844
Stock-based compensation expense	10,732	$ 0	10,732	0	0
Issuance of common stock upon exercise of stock options	493	$ 1	492	0	0
Issuance of common stock upon exercise of stock options, Shares		346
Issuance of common stock upon 2018 ESPP purchase	195	$ 0	195	0	0
Issuance of common stock upon 2018 ESPP purchase, Shares		62
Issuance of common stock upon vesting of restricted stock units	0	$ 0	0	0	0
Issuance of common stock upon vesting of restricted stock units, Shares		59
Issuance of common stock upon registered direct offering, net	140,591	$ 30	140,561	0	0
Issuance of common stock upon registered direct offering net, Shares		29,882
Unrealized gain (loss) on investments	196	$ 0	0	196	0
Net loss	(30,837)	0	0	0	(30,837)
Balance at Sep. 30, 2022	$ 344,179	$ 85	$ 1,233,945	$ (64)	$ (889,787)
Balance, Shares at Sep. 30, 2022		85,193