Statements of Convertible Preferred Stock and Stockholders’ Deficit - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Loans to Related Parties	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2017	39,361,211
Beginning balance at Dec. 31, 2017	$ 148,194
Preferred Stock
Issuance of Series G preferred stock, net of issuance costs of $7 (in shares)	112,945
Issuance of Series G preferred stock, net of issuance costs of $7	$ 1,228
Ending balance (in shares) at Mar. 31, 2018	39,474,156
Ending balance at Mar. 31, 2018	$ 149,422
Beginning balance (in shares) at Dec. 31, 2017		5,724,506
Beginning balance at Dec. 31, 2017	(95,913)	$ 1	$ 4,823	$ (951)	$ (99,786)
Common Stock
Net loss	(5,696)				(5,696)
Exercise of common stock options (in shares)		92,310
Exercise of common stock options	88		88
Share-based compensation	260		260
Ending balance (in shares) at Mar. 31, 2018		5,816,816
Ending balance at Mar. 31, 2018	$ (101,261)	$ 1	5,171	(951)	(105,482)
Beginning balance (in shares) at Dec. 31, 2018	41,562,111
Beginning balance at Dec. 31, 2018	$ 199,540
Ending balance (in shares) at Mar. 30, 2019	41,562,111
Ending balance at Mar. 30, 2019	$ 199,540
Beginning balance (in shares) at Dec. 31, 2018		6,951,350
Beginning balance at Dec. 31, 2018	(121,750)	$ 1	7,921	0	(129,672)
Common Stock
Net loss	$ (6,649)				(6,649)
Exercise of common stock options (in shares)	169,583	169,583
Exercise of common stock options	$ 366		366
Share-based compensation	855		855
Ending balance (in shares) at Mar. 30, 2019		7,120,933
Ending balance at Mar. 30, 2019	$ (127,178)	$ 1	$ 9,142	$ 0	$ (136,321)