Statements of Convertible Preferred Stock and Stockholders’ Equity (Deficit) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Loans to Related Parties	Accumulated Deficit	IPO	IPO Common Stock	IPO Additional Paid-in Capital	Secondary Offering	Secondary Offering Common Stock	Secondary Offering Additional Paid-in Capital	Series F	Series G	Series H
Beginning balance (in shares) at Dec. 31, 2016	34,355,941
Beginning balance at Dec. 31, 2016	$ 93,804
Preferred Stock
Conversion of convertible notes upon issuance of Series G preferred stock(inclusive of $1,123 adjustment upon conversion (in shares)													1,026,367
Conversion of convertible notes upon issuance of Series G preferred stock (inclusive of $1,123 adjustment upon conversion)													$ 11,123
Issuance of Series G preferred stock, net of issuance costs (in shares)												16,168	3,962,735
Issuance of Series G preferred stock, net of issuance costs												$ 79	$ 43,188
Ending balance (in shares) at Dec. 31, 2017	39,361,211
Ending balance at Dec. 31, 2017	$ 148,194
Beginning balance (in shares) at Dec. 31, 2016		5,278,305
Beginning balance at Dec. 31, 2016	(66,573)	$ 1	$ 3,779	$ (951)	$ (69,402)
Common Stock
Net loss available to common stockholders	(30,384)				(30,384)
Issuance of common stock upon conversion of convertible preferred stock	0
Reclassification of warrant liability to additional paid-in capital upon closing of the initial public offering	$ 0
Exercise of common stock options (in shares)	446,201	446,201
Exercise of common stock options	$ 379		379
Share-based compensation	665		665
Ending balance (in shares) at Dec. 31, 2017		5,724,506
Ending balance at Dec. 31, 2017	$ (95,913)	$ 1	4,823	(951)	(99,786)
Preferred Stock
Issuance of Series G preferred stock, net of issuance costs (in shares)													125,684	2,075,216
Issuance of Series G preferred stock, net of issuance costs													$ 1,347	$ 49,999
Ending balance (in shares) at Dec. 31, 2018	41,562,111											4,866,758	5,114,786	2,075,216
Ending balance at Dec. 31, 2018	$ 199,540											$ 29,840	$ 55,658	$ 49,999
Common Stock
Net loss available to common stockholders	(29,886)				(29,886)
Issuance of common stock upon conversion of convertible preferred stock	0
Reclassification of warrant liability to additional paid-in capital upon closing of the initial public offering	$ 0
Exercise of common stock options (in shares)	1,139,962	1,139,962
Exercise of common stock options	$ 1,369		1,369
Share-based compensation	2,241		2,241
Re-purchase of common stock (in shares)		(48,909)
Re-purchase of common stock	(514)		(514)
Grant of restricted stock (in shares)		135,791
Grant of restricted stock	2		2
Payoff of promissory notes receivable for restricted stock purchase	951			951
Ending balance (in shares) at Dec. 31, 2018		6,951,350
Ending balance at Dec. 31, 2018	$ (121,750)	$ 1	7,921	0	(129,672)
Preferred Stock
Issuance of common stock upon conversion of convertible preferred stock (in shares)	(41,562,111)
Issuance of common stock upon conversion of convertible preferred stock	$ (199,540)
Ending balance (in shares) at Dec. 31, 2019												0	0	0
Ending balance at Dec. 31, 2019												$ 0	$ 0	$ 0
Common Stock
Net loss available to common stockholders	(12,443)				(12,443)
Issuance of common stock upon conversion of convertible preferred stock (in shares)		41,562,111					11,068,750			250,000
Issuance of common stock upon conversion of convertible preferred stock	199,540	$ 4	199,536			$ 252,453	$ 1	$ 252,452	$ 37,394		$ 37,394
Issuance of common stock upon exercise of common stock warrants (in shares)		214,875
Issuance of common stock upon exercise of common stock warrants	0
Reclassification of warrant liability to additional paid-in capital upon closing of the initial public offering	$ 14,421		14,421
Exercise of common stock options (in shares)	1,429,756	1,529,408
Exercise of common stock options	$ 2,669		2,669
Share-based compensation	11,806		11,806
Ending balance at Dec. 31, 2019	$ 384,090
Beginning balance (in shares) at Sep. 28, 2019	0
Beginning balance at Sep. 28, 2019	$ 0
Ending balance (in shares) at Dec. 31, 2019												0	0	0
Ending balance at Dec. 31, 2019												$ 0	$ 0	$ 0
Beginning balance (in shares) at Sep. 28, 2019		61,576,494
Beginning balance at Sep. 28, 2019	384,090	$ 6	$ 526,199	$ 0	$ (142,115)
Common Stock
Net loss available to common stockholders	(452)
Ending balance at Dec. 31, 2019	$ 384,090