Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Unaudited) - USD ($) $ in Thousands	Total	Private Placement	Series A Convertible Preferred Stock	Series B Convertible Preferred Stock	Common Stock	Common Stock Private Placement	Treasury Stock	Additional Paid-In Capital	Additional Paid-In Capital Private Placement	AOCI Attributable to Parent	Accumulated Deficit
Convertible preferred stock, Beginning balance, Shares at Dec. 31, 2018			60,000,000	40,000,000
Convertible preferred stock, Beginning balance at Dec. 31, 2018			$ 59,909	$ 79,761
Beginning balance at Dec. 31, 2018	$ (63,670)				$ 2			$ 4,452			$ (68,124)
Beginning balance, Shares at Dec. 31, 2018					1,587,953		67,024
Issuance of convertible preferred stock				$ 25,466
Issuance of convertible preferred stock, Shares				12,500,000
Issuance of common stock	5							5
Issuance of common stock, Shares					134,013
Repurchase of unvested restricted stock awards							43,922
Retirement of treasury shares							(110,946)
Stock-based compensation expense	821							821
Net loss	(36,843)										(36,843)
Convertible preferred stock, Ending balance, Shares at Mar. 31, 2019			60,000,000	52,500,000
Convertible preferred stock, Ending balance at Mar. 31, 2019			$ 59,909	$ 105,227
Ending balance at Mar. 31, 2019	(99,687)				$ 2			5,278			(104,967)
Ending balance, Shares at Mar. 31, 2019					1,721,966
Convertible preferred stock, Beginning balance, Shares at Dec. 31, 2018			60,000,000	40,000,000
Convertible preferred stock, Beginning balance at Dec. 31, 2018			$ 59,909	$ 79,761
Beginning balance at Dec. 31, 2018	(63,670)				$ 2			4,452			(68,124)
Beginning balance, Shares at Dec. 31, 2018					1,587,953		67,024
Net loss	(66,554)
Ending balance at Sep. 30, 2019	102,128				$ 23			236,783			(134,678)
Ending balance, Shares at Sep. 30, 2019					22,557,871
Convertible preferred stock, Beginning balance, Shares at Mar. 31, 2019			60,000,000	52,500,000
Convertible preferred stock, Beginning balance at Mar. 31, 2019			$ 59,909	$ 105,227
Beginning balance at Mar. 31, 2019	(99,687)				$ 2			5,278			(104,967)
Beginning balance, Shares at Mar. 31, 2019					1,721,966
Issuance of common stock	225							225
Issuance of common stock, Shares					148,320
Repurchase of unvested restricted stock awards							7,451
Retirement of treasury shares							(6,019)
Stock-based compensation expense	950							950
Net loss	(13,169)										(13,169)
Convertible preferred stock, Ending balance, Shares at Jun. 30, 2019			60,000,000	52,500,000
Convertible preferred stock, Ending balance at Jun. 30, 2019			$ 59,909	$ 105,227
Ending balance at Jun. 30, 2019	(111,681)				$ 2			6,453			(118,136)
Ending balance, Shares at Jun. 30, 2019					1,870,286		1,432
Issuance of common stock	35							35
Issuance of common stock, Shares					116,167
Conversion of convertible preferred stock into common stock	165,136		$ (59,909)	$ (105,227)	$ 16			165,120
Conversion of convertible preferred stock into common stock, Shares			(60,000,000)	(52,500,000)
Initial public offering, net of underwriting discounts, commissions and offering costs	64,001				$ 5			63,996
Initial public offering net of underwriting discounts, commissions and offering costs, Shares					4,500,000
Repurchase of unvested restricted stock awards							4,951
Retirement of treasury shares							(6,383)
Stock-based compensation expense	1,179							1,179
Net loss	(16,542)										(16,542)
Ending balance at Sep. 30, 2019	102,128				$ 23			236,783			(134,678)
Ending balance, Shares at Sep. 30, 2019					22,557,871
Conversion of convertible preferred stock into common stock, Shares					16,071,418
Beginning balance at Dec. 31, 2019	87,153				$ 23			237,931			(150,801)
Beginning balance, Shares at Dec. 31, 2019					22,654,444
Issuance of common stock	290							290
Issuance of common stock, Shares					138,693
Repurchase of unvested restricted stock awards							8,787
Retirement of treasury shares							(8,787)
Stock-based compensation expense	1,693							1,693
Unrealized gain (loss) on marketable securities	(53)									$ (53)
Net loss	(18,452)										(18,452)
Ending balance at Mar. 31, 2020	70,631				$ 23			239,914		(53)	(169,253)
Ending balance, Shares at Mar. 31, 2020					22,793,137
Beginning balance at Dec. 31, 2019	87,153				$ 23			237,931			(150,801)
Beginning balance, Shares at Dec. 31, 2019					22,654,444
Unrealized gain (loss) on marketable securities	31
Net loss	(53,099)
Ending balance at Sep. 30, 2020	104,985				$ 27			308,827		31	(203,900)
Ending balance, Shares at Sep. 30, 2020					27,277,983
Beginning balance at Mar. 31, 2020	70,631				$ 23			239,914		(53)	(169,253)
Beginning balance, Shares at Mar. 31, 2020					22,793,137
Issuance of common stock	530	$ 64,317				$ 4		530	$ 64,313
Issuance of common stock, Shares					401,248	4,029,411
Repurchase of unvested restricted stock awards							10,642
Retirement of treasury shares							(10,642)
Stock-based compensation expense	2,204							2,204
Unrealized gain (loss) on marketable securities	134									134
Net loss	(15,685)										(15,685)
Ending balance at Jun. 30, 2020	122,131				$ 27			306,961		81	(184,938)
Ending balance, Shares at Jun. 30, 2020					27,223,796
Issuance of common stock	90							90
Issuance of common stock, Shares					54,187
Repurchase of unvested restricted stock awards							4,581
Retirement of treasury shares							(4,581)
Stock-based compensation expense	1,776							1,776
Unrealized gain (loss) on marketable securities	(50)									(50)
Net loss	(18,962)										(18,962)
Ending balance at Sep. 30, 2020	$ 104,985				$ 27			$ 308,827		$ 31	$ (203,900)
Ending balance, Shares at Sep. 30, 2020					27,277,983