Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenue:
Product revenue	$ 19,590	$ 11,333	$ 45,073	$ 28,615
Type of Revenue [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember
Cost of revenue:
Cost of product revenue	$ 5,277	$ 4,401	$ 14,520	$ 11,606
Type of Cost, Good Or Service [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember
Gross profit	$ 14,313	$ 6,932	$ 30,553	$ 17,009
Operating expenses:
Research and development	7,891	8,368	27,882	22,778
Sales and marketing	13,619	8,192	35,236	21,023
General and administrative	5,610	3,437	17,232	9,684
Total operating expenses	27,120	19,997	80,350	53,485
Loss from operations	(12,807)	(13,065)	(49,797)	(36,476)
Interest expense	(314)	(251)	(897)	(746)
Change in fair value of warrant liability				(609)
Other income, net	218	385	942	1,518
Net loss before taxes	(12,903)	(12,931)	(49,752)	(36,313)
Income tax provision	29	26	73	51
Net loss	(12,932)	(12,957)	(49,825)	(36,364)
Other comprehensive income (loss):
Unrealized gain/(loss) on available-for-sale securities		(18)	(14)	57
Adjustment for net gain realized and included in other income, net	(21)		(21)
Total other comprehensive income (loss)	(21)	(18)	(35)	57
Total comprehensive loss	$ (12,953)	$ (12,975)	$ (49,860)	$ (36,307)
Net loss per share, basic and diluted	$ (0.38)	$ (0.46)	$ (1.53)	$ (1.66)
Shares used in computing net loss per share, basic and diluted	34,078,726	28,085,821	32,631,715	21,886,396