Quarterly Financial Information (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 18,634	$ 17,026	$ 14,928	$ 12,766	$ 11,470	$ 9,614	$ 7,767	$ 5,706	$ 63,354	$ 34,557
Gross Profit	13,913	12,856	11,231	9,427	7,803	6,732	5,376	3,772	47,427	23,683
Net loss	$ (8,291)	$ (8,007)	$ (11,959)	$ (24,158)	$ (15,618)	$ (8,953)	$ (7,651)	$ (5,408)	$ (52,415)	$ (37,630)
Net loss per share, basic and diluted (in USD per share)	$ (0.27)	$ (0.26)	$ (0.42)	$ (20.12)	$ (14.12)	$ (8.49)	$ (8.16)	$ (7.31)	$ (2.28)	$ (39.16)