STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Unaudited) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
Revenue	$ 35,842,000	$ 20,862,000	$ 69,372,000	$ 55,144,000
Cost of goods sold	5,211,000	3,456,000	10,462,000	9,404,000
Gross profit	30,631,000	17,406,000	58,910,000	45,740,000
Operating expenses:
Research and development	7,307,000	3,623,000	18,807,000	9,072,000
Selling, general and administrative	33,216,000	22,434,000	89,249,000	62,272,000
Total operating expenses	40,523,000	26,057,000	108,056,000	71,344,000
Operating loss	(9,892,000)	(8,651,000)	(49,146,000)	(25,604,000)
Other expense (income):
Interest income	(125,000)	(903,000)	(1,015,000)	(3,025,000)
Interest expense	533,000	529,000	1,584,000	1,589,000
Other income, net	(2,000)	(30,000)	(83,000)	(5,000)
Total other expense (income)	406,000	(404,000)	486,000	(1,441,000)
Loss before income taxes	(10,298,000)	(8,247,000)	(49,632,000)	(24,163,000)
Income taxes	87,000	0	87,000	0
Net loss	(10,385,000)	(8,247,000)	(49,719,000)	(24,163,000)
Other comprehensive loss:
Unrealized (loss) gain on investments	(81,000)	39,000	(29,000)	142,000
Total comprehensive loss	$ (10,466,000)	$ (8,208,000)	$ (49,748,000)	$ (24,021,000)
Net loss per share, basic and diluted (in dollars per share)	$ (0.39)	$ (0.34)	$ (1.93)	$ (1.02)
Weighted average common shares used to compute net loss per share, basic and diluted (in shares)	26,835,603	23,940,430	25,767,497	23,713,705