Condensed Statements of Stockholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Accumulated Deficit Cumulative Effect, Period of Adoption, Adjustment
Adoption of accounting standard (See Note 2)		$ 21					$ 21
Balances at January 1, 2019	$ 66,726		$ 1	$ 126,925		$ (60,200)
Balances at Dec. 31, 2018	$ 66,705		$ 1	126,925		$ (60,221)
Balance (in shares) at Dec. 31, 2018			12,689
AccountingStandardsUpdateExtensibleList	us-gaap:AccountingStandardsUpdate201807Member					us-gaap:AccountingStandardsUpdate201807Member
Common stock issued (in shares)			148
Stock-based compensation	$ 7,745			7,745
Net loss	(14,674)					$ (14,674)
Balances at Mar. 31, 2019	59,797		$ 1	134,670		(74,874)
Balance (in shares) at Mar. 31, 2019			12,837
Balances at Dec. 31, 2018	66,705		$ 1	126,925		(60,221)
Balance (in shares) at Dec. 31, 2018			12,689
Other comprehensive Income (loss)	38
Net loss	(47,214)
Balances at Sep. 30, 2019	41,741		$ 1	149,116	$ 38	(107,414)
Balance (in shares) at Sep. 30, 2019			13,408
Balances at Mar. 31, 2019	59,797		$ 1	134,670		(74,874)
Balance (in shares) at Mar. 31, 2019			12,837
Common stock issued	37			37
Common stock issued (in shares)			384
Stock-based compensation	7,132			7,132
Other comprehensive Income (loss)	51				51
Net loss	(15,122)					(15,122)
Balances at Jun. 30, 2019	51,895		$ 1	141,839	51	(89,996)
Balance (in shares) at Jun. 30, 2019			13,221
Common stock issued (in shares)			187
Stock-based compensation	7,277			7,277
Other comprehensive Income (loss)	(13)				(13)
Net loss	(17,418)					(17,418)
Balances at Sep. 30, 2019	41,741		$ 1	149,116	38	(107,414)
Balance (in shares) at Sep. 30, 2019			13,408
Balances at Dec. 31, 2019	33,150		$ 1	150,280	26	(117,157)
Balance (in shares) at Dec. 31, 2019			13,770
Common stock issued (in shares)			125
Stock-based compensation	1,047			1,047
Other comprehensive Income (loss)	(22)				(22)
Net loss	(7,701)					(7,701)
Balances at Mar. 31, 2020	26,474		$ 1	151,327	4	(124,858)
Balance (in shares) at Mar. 31, 2020			13,895
Balances at Dec. 31, 2019	33,150		$ 1	150,280	26	(117,157)
Balance (in shares) at Dec. 31, 2019			13,770
Other comprehensive Income (loss)	(26)
Net loss	(25,601)
Balances at Sep. 30, 2020	30,538		$ 7	173,289		(142,758)
Balance (in shares) at Sep. 30, 2020			72,468
Balances at Mar. 31, 2020	26,474		$ 1	151,327	4	(124,858)
Balance (in shares) at Mar. 31, 2020			13,895
Exercise of warrants	827		$ 1	826
Exercise of warrants (in shares)			1,838
Common stock issued pursuant to the vesting of restricted stock units and ESPP	27			27
Common stock issued pursuant to the vesting of restricted stock units and ESPP (in shares)			228
Common stock issued	5,284		$ 2	5,282
Common stock issued (in shares)			22,222
Warrants issued, net	3,464			3,464
Stock-based compensation	1,033			1,033
Other comprehensive Income (loss)	(4)				$ (4)
Net loss	(10,121)					(10,121)
Balances at Jun. 30, 2020	26,984		$ 4	161,959		(134,979)
Balance (in shares) at Jun. 30, 2020			38,183
Common stock issued	6,341		$ 3	6,338
Common stock issued (in shares)			34,285
Warrants issued, net	4,028			4,028
Stock-based compensation	964			964
Net loss	(7,779)					(7,779)
Balances at Sep. 30, 2020	$ 30,538		$ 7	$ 173,289		$ (142,758)
Balance (in shares) at Sep. 30, 2020			72,468