Note 6 - Supplemental Balance Sheet Information (Details Textual) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Restricted Cash and Cash Equivalents, Total	$ 247		$ 270
Depreciation, Total	579	$ 447
Amortization of Intangible Assets, Total	149	92
Research and Development Expense [Member]
Amortization of Intangible Assets, Total	31	33
Selling, General and Administrative Expenses [Member]
Amortization of Intangible Assets, Total	118	$ 59
Grant [Member]
Revenues, Total	20
CHINA
Restricted Cash and Cash Equivalents, Total	166		188
NETHERLANDS
Restricted Cash and Cash Equivalents, Total	$ 81		$ 82