STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	ATM Offering [Member]	Common Stock	Common Stock ATM Offering [Member]	Additional Paid-In Capital	Additional Paid-In Capital ATM Offering [Member]	Accumulated Other Comprehensive Gain (Loss)	Accumulated Other Comprehensive Gain (Loss) ATM Offering [Member]	Accumulated Deficit	Accumulated Deficit ATM Offering [Member]
Balance at Dec. 31, 2022	$ 310,433		$ 85		$ 1,243,408		$ (284)		$ (932,776)
Balance, Shares at Dec. 31, 2022			85,387
Stock-based compensation expense	10,665		$ 0		10,665		0		0
Issuance of common stock upon exercise of stock options	26		$ 0		26		0		0
Issuance of common stock upon exercise of stock options, Shares			6
Issuance of common stock upon 2018 ESPP purchase	442		$ 0		442		0		0
Issuance of common stock upon 2018 ESPP purchase, Shares			144
Issuance of common stock upon vesting of restricted stock units	0		$ 1		(1)		0		0
Issuance of common stock upon vesting of restricted stock units, Shares			881
Issuance of common stock under the ATM / registered direct Offering net of issuance costs		$ 990		$ 0		$ 990		$ 0		$ 0
Issuance of common stock under the ATM /registered direct Offering net of issuance costs, Shares				142
Unrealized gain (loss) on investments	296		$ 0		0		296		0
Net Income (Loss)	(42,404)		0		0		0		(42,404)
Balance at Mar. 31, 2023	280,448		$ 86		1,255,530		12		(975,180)
Balance, Shares at Mar. 31, 2023			86,560
Balance at Dec. 31, 2023	168,817		$ 88		1,287,156		50		(1,118,477)
Balance, Shares at Dec. 31, 2023			87,750
Stock-based compensation expense	6,210		$ 0		6,210		0		0
Issuance of common stock upon exercise of stock options	$ 26		$ 0		26		0		0
Issuance of common stock upon exercise of stock options, Shares	26		26
Issuance of common stock upon 2018 ESPP purchase	$ 106		$ 0		106		0		0
Issuance of common stock upon 2018 ESPP purchase, Shares			98
Issuance of common stock upon vesting of restricted stock units	0		$ 1		(1)		0		0
Issuance of common stock upon vesting of restricted stock units, Shares			670
Unrealized gain (loss) on investments	(30)		$ 0		0		(30)		0
Net Income (Loss)	(71,146)		0		0		0		(71,146)
Balance at Mar. 31, 2024	$ 103,983		$ 89		$ 1,293,497		$ 20		$ (1,189,623)
Balance, Shares at Mar. 31, 2024			88,544