Note 2 - Fair Value Measurement - Financial Assets and Liabilities on Recurring Basis (Details) - Fair Value, Recurring [Member] - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Assets	$ 73,161	$ 90,403
Liabilities	8,378	9,932
Contingent Consideration Liabilities [Member]
Liabilities	8,378
Warrant Liabilities [Member]
Liabilities		2,780
Money Market Funds [Member]
Assets	73,161	90,403
Contingent Consideration Liabilities [Member]
Liabilities		7,152
Fair Value, Inputs, Level 1 [Member]
Assets	73,161	90,403
Liabilities	0	0
Fair Value, Inputs, Level 1 [Member] | Contingent Consideration Liabilities [Member]
Liabilities	0
Fair Value, Inputs, Level 1 [Member] | Warrant Liabilities [Member]
Liabilities		0
Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member]
Assets	73,161	90,403
Fair Value, Inputs, Level 1 [Member] | Contingent Consideration Liabilities [Member]
Liabilities		0
Fair Value, Inputs, Level 2 [Member]
Assets	0	0
Liabilities	0	0
Fair Value, Inputs, Level 2 [Member] | Contingent Consideration Liabilities [Member]
Liabilities	0
Fair Value, Inputs, Level 2 [Member] | Warrant Liabilities [Member]
Liabilities		0
Fair Value, Inputs, Level 2 [Member] | Money Market Funds [Member]
Assets	0	0
Fair Value, Inputs, Level 2 [Member] | Contingent Consideration Liabilities [Member]
Liabilities		0
Fair Value, Inputs, Level 3 [Member]
Assets	0	0
Liabilities	8,378	9,932
Fair Value, Inputs, Level 3 [Member] | Contingent Consideration Liabilities [Member]
Liabilities	8,378
Fair Value, Inputs, Level 3 [Member] | Warrant Liabilities [Member]
Liabilities		2,780
Fair Value, Inputs, Level 3 [Member] | Money Market Funds [Member]
Assets	$ 0	0
Fair Value, Inputs, Level 3 [Member] | Contingent Consideration Liabilities [Member]
Liabilities		$ 7,152