Note 6 - Note Payable - Summary of Note Payable (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	[1]
2019 (remaining three months)	$ 710
2020	2,901
2021	16,673
2022	19,306
2023	6,220
Total payments	45,810
Less: Amount representing interest	(13,087)
Present value of obligations	32,723
Less: Unamortized debt discount	(1,029)
Note payable, noncurrent portion	$ 31,694	$ 30,528

[1] The condensed consolidated balance sheet as of December 31, 2018 has been derived from the audited consolidated financial statements as of that date.