Condensed Statements of Changes in Convertible Preferred Stock and Stockholders' Deficit - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Series A-1 Convertible Preferred Stock	Series A-2 Convertible Preferred Stock	Series A-3 Convertible Preferred Stock	Series B Convertible Preferred Stock	Series B-1 Convertible Preferred Stock	Series C Convertible Preferred Stock	Series D Convertible Preferred Stock	Series E Convertible Preferred Stock	Series F Convertible Preferred Stock	Series G Convertible Preferred Stock	Series H Convertible Preferred Stock
Balances at Dec. 31, 2018	$ (198,030)	$ 1	$ 2,107	$ (200,138)
Temporary Equity Balance, Shares at Dec. 31, 2018					700,000	267,000	750,000	3,642,000	2,999,000	2,357,000	10,875,000	7,640,000	19,468,000	46,147,000	15,228,000
Temporary Equity Balance at Dec. 31, 2018	183,962				$ 800	$ 400	$ 1,672	$ 9,907	$ 9,551	$ 7,040	$ 41,266	$ 32,736	$ 28,585	$ 34,537	$ 17,468
Common Stock Balance, Shares at Dec. 31, 2018		215,000
Exercise of stock options	30		30
Exercise of stock options, shares		25,000
Stock‑based compensation	31		31
Issuance of Series H Preferred Stock	9,997														$ 9,997
Issuance of Series H Preferred Stock, shares															8,695,000
Net loss	(7,744)			(7,744)
Balances at Mar. 31, 2019	(205,713)	$ 1	2,168	(207,882)
Temporary Equity Balance, Shares at Mar. 31, 2019					700,000	267,000	750,000	3,642,000	2,999,000	2,357,000	10,875,000	7,640,000	19,468,000	46,147,000	23,923,000
Temporary Equity Balance at Mar. 31, 2019	193,959				$ 800	$ 400	$ 1,672	$ 9,907	$ 9,551	$ 7,040	$ 41,266	$ 32,736	$ 28,585	$ 34,537	$ 27,465
Common Stock Balance, Shares at Mar. 31, 2019		240,000
Balances at Dec. 31, 2018	(198,030)	$ 1	2,107	(200,138)
Temporary Equity Balance, Shares at Dec. 31, 2018					700,000	267,000	750,000	3,642,000	2,999,000	2,357,000	10,875,000	7,640,000	19,468,000	46,147,000	15,228,000
Temporary Equity Balance at Dec. 31, 2018	183,962				$ 800	$ 400	$ 1,672	$ 9,907	$ 9,551	$ 7,040	$ 41,266	$ 32,736	$ 28,585	$ 34,537	$ 17,468
Common Stock Balance, Shares at Dec. 31, 2018		215,000
Net loss	(24,201)
Balances at Sep. 30, 2019	(222,059)	$ 1	2,279	(224,339)
Temporary Equity Balance, Shares at Sep. 30, 2019					700,000	267,000	750,000	3,642,000	2,999,000	2,357,000	10,875,000	7,640,000	19,468,000	46,147,000	23,923,000
Temporary Equity Balance at Sep. 30, 2019	193,959				$ 800	$ 400	$ 1,672	$ 9,907	$ 9,551	$ 7,040	$ 41,266	$ 32,736	$ 28,585	$ 34,537	$ 27,465
Common Stock Balance, Shares at Sep. 30, 2019		255,000
Balances at Mar. 31, 2019	(205,713)	$ 1	2,168	(207,882)
Temporary Equity Balance, Shares at Mar. 31, 2019					700,000	267,000	750,000	3,642,000	2,999,000	2,357,000	10,875,000	7,640,000	19,468,000	46,147,000	23,923,000
Temporary Equity Balance at Mar. 31, 2019	193,959				$ 800	$ 400	$ 1,672	$ 9,907	$ 9,551	$ 7,040	$ 41,266	$ 32,736	$ 28,585	$ 34,537	$ 27,465
Common Stock Balance, Shares at Mar. 31, 2019		240,000
Exercise of stock options	1	$ 3	1
Stock‑based compensation	49		49
Net loss	(6,856)			(6,856)
Balances at Jun. 30, 2019	(212,519)	$ 1	2,218	(214,738)
Temporary Equity Balance, Shares at Jun. 30, 2019					700,000	267,000	750,000	3,642,000	2,999,000	2,357,000	10,875,000	7,640,000	19,468,000	46,147,000	23,923,000
Temporary Equity Balance at Jun. 30, 2019	193,959				$ 800	$ 400	$ 1,672	$ 9,907	$ 9,551	$ 7,040	$ 41,266	$ 32,736	$ 28,585	$ 34,537	$ 27,465
Common Stock Balance, Shares at Jun. 30, 2019		243,000
Exercise of stock options	16		16
Exercise of stock options, shares		12,000
Stock‑based compensation	45		45
Net loss	(9,601)			(9,601)
Balances at Sep. 30, 2019	(222,059)	$ 1	2,279	(224,339)
Temporary Equity Balance, Shares at Sep. 30, 2019					700,000	267,000	750,000	3,642,000	2,999,000	2,357,000	10,875,000	7,640,000	19,468,000	46,147,000	23,923,000
Temporary Equity Balance at Sep. 30, 2019	193,959				$ 800	$ 400	$ 1,672	$ 9,907	$ 9,551	$ 7,040	$ 41,266	$ 32,736	$ 28,585	$ 34,537	$ 27,465
Common Stock Balance, Shares at Sep. 30, 2019		255,000
Balances at Dec. 31, 2019	$ (228,539)	$ 1	2,324	(230,864)
Temporary Equity Balance, Shares at Dec. 31, 2019	118,766,273				700,000	267,000	750,000	3,642,000	2,999,000	2,357,000	10,875,000	7,640,000	19,468,000	46,147,000	23,923,000
Temporary Equity Balance at Dec. 31, 2019	$ 193,959				$ 800	$ 400	$ 1,672	$ 9,907	$ 9,551	$ 7,040	$ 41,266	$ 32,736	$ 28,585	$ 34,537	$ 27,465
Common Stock Balance, Shares at Dec. 31, 2019		255,000
Exercise of stock options	11	$ 1	10
Exercise of stock options, shares		20,000
Net loss	(9,706)			(9,706)
Balances at Mar. 31, 2020	(238,234)	$ 2	2,334	(240,570)
Temporary Equity Balance, Shares at Mar. 31, 2020					700,000	267,000	750,000	3,642,000	2,999,000	2,357,000	10,875,000	7,640,000	19,468,000	46,147,000	23,923,000
Temporary Equity Balance at Mar. 31, 2020	193,959				$ 800	$ 400	$ 1,672	$ 9,907	$ 9,551	$ 7,040	$ 41,266	$ 32,736	$ 28,585	$ 34,537	$ 27,465
Common Stock Balance, Shares at Mar. 31, 2020		275,000
Balances at Dec. 31, 2019	$ (228,539)	$ 1	2,324	(230,864)
Temporary Equity Balance, Shares at Dec. 31, 2019	118,766,273				700,000	267,000	750,000	3,642,000	2,999,000	2,357,000	10,875,000	7,640,000	19,468,000	46,147,000	23,923,000
Temporary Equity Balance at Dec. 31, 2019	$ 193,959				$ 800	$ 400	$ 1,672	$ 9,907	$ 9,551	$ 7,040	$ 41,266	$ 32,736	$ 28,585	$ 34,537	$ 27,465
Common Stock Balance, Shares at Dec. 31, 2019		255,000
Exercise of stock options, shares	35,000
Net loss	$ (26,817)
Balances at Sep. 30, 2020	$ (255,176)	$ 2	2,503	(257,681)
Temporary Equity Balance, Shares at Sep. 30, 2020	118,766,273				700,000	266,668	750,000	3,641,817	2,998,852	2,356,596	10,874,876	7,639,556	19,468,203	46,146,517	23,923,188
Temporary Equity Balance at Sep. 30, 2020	$ 193,959				$ 800	$ 400	$ 1,672	$ 9,907	$ 9,551	$ 7,040	$ 41,266	$ 32,736	$ 28,585	$ 34,537	$ 27,465
Common Stock Balance, Shares at Sep. 30, 2020		290,000
Balances at Mar. 31, 2020	(238,234)	$ 2	2,334	(240,570)
Temporary Equity Balance, Shares at Mar. 31, 2020					700,000	267,000	750,000	3,642,000	2,999,000	2,357,000	10,875,000	7,640,000	19,468,000	46,147,000	23,923,000
Temporary Equity Balance at Mar. 31, 2020	193,959				$ 800	$ 400	$ 1,672	$ 9,907	$ 9,551	$ 7,040	$ 41,266	$ 32,736	$ 28,585	$ 34,537	$ 27,465
Common Stock Balance, Shares at Mar. 31, 2020		275,000
Stock‑based compensation	55		55
Net loss	(8,266)			(8,266)
Balances at Jun. 30, 2020	(246,445)	$ 2	2,389	(248,836)
Temporary Equity Balance, Shares at Jun. 30, 2020					700,000	267,000	750,000	3,642,000	2,999,000	2,357,000	10,875,000	7,640,000	19,468,000	46,147,000	23,923,000
Temporary Equity Balance at Jun. 30, 2020	193,959				$ 800	$ 400	$ 1,672	$ 9,907	$ 9,551	$ 7,040	$ 41,266	$ 32,736	$ 28,585	$ 34,537	$ 27,465
Common Stock Balance, Shares at Jun. 30, 2020		275,000
Exercise of stock options	14		14
Exercise of stock options, shares		15,000
Stock‑based compensation	100		100
Net loss	(8,845)			(8,845)
Balances at Sep. 30, 2020	$ (255,176)	$ 2	$ 2,503	$ (257,681)
Temporary Equity Balance, Shares at Sep. 30, 2020	118,766,273				700,000	266,668	750,000	3,641,817	2,998,852	2,356,596	10,874,876	7,639,556	19,468,203	46,146,517	23,923,188
Temporary Equity Balance at Sep. 30, 2020	$ 193,959				$ 800	$ 400	$ 1,672	$ 9,907	$ 9,551	$ 7,040	$ 41,266	$ 32,736	$ 28,585	$ 34,537	$ 27,465
Common Stock Balance, Shares at Sep. 30, 2020		290,000