STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Unaudited) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Statement [Abstract]
Revenue	$ 21,347,000	$ 16,250,000
Cost of goods sold	3,297,000	2,854,000
Gross profit	18,050,000	13,396,000
Operating expenses:
Research and development	5,438,000	2,603,000
Selling, general and administrative	29,052,000	19,570,000
Total operating expenses	34,490,000	22,173,000
Operating loss	(16,440,000)	(8,777,000)
Other (income) expense:
Interest income	(642,000)	(1,086,000)
Interest expense	525,000	537,000
Other (income) expense, net	(78,000)	38,000
Total other income	(195,000)	(511,000)
Loss before income taxes	(16,245,000)	(8,266,000)
Income taxes	0	0
Net loss	(16,245,000)	(8,266,000)
Other comprehensive loss:
Unrealized gain on investments	193,000	68,000
Total comprehensive loss	$ (16,052,000)	$ (8,198,000)
Net loss per share, basic and diluted (in dollars per share)	$ (0.67)	$ (0.35)
Weighted average common shares used to compute net loss per share, basic and diluted (in shares)	24,165,875	23,441,560