Note 2 - Fair Value Measurement - Financial Assets and Liabilities on Recurring Basis (Details) - Fair Value, Recurring [Member] - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Assets	$ 30,879	$ 7,448
Liabilities	1,350	41,516
Contingent Consideration Liabilities [Member]
Liabilities	387
Warrant Liabilities [Member]
Liabilities	963	39,602
Money Market Funds [Member]
Assets	29,879	6,448
Convertible Debt Securities [Member]
Assets	1,000	1,000
Contingent Consideration Liabilities [Member]
Liabilities		1,914
Fair Value, Inputs, Level 1 [Member]
Assets	29,879	6,448
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	0
Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member]
Assets	29,879	6,448
Fair Value, Inputs, Level 1 [Member] | Convertible Debt Securities [Member]
Assets	0	0
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	0
Fair Value, Inputs, Level 2 [Member] | Money Market Funds [Member]
Assets	0	0
Fair Value, Inputs, Level 2 [Member] | Convertible Debt Securities [Member]
Assets	0	0
Fair Value, Inputs, Level 2 [Member] | Contingent Consideration Liabilities [Member]
Liabilities		0
Fair Value, Inputs, Level 3 [Member]
Assets	1,000	1,000
Liabilities	1,350	41,516
Fair Value, Inputs, Level 3 [Member] | Contingent Consideration Liabilities [Member]
Liabilities	387
Fair Value, Inputs, Level 3 [Member] | Warrant Liabilities [Member]
Liabilities	963	39,602
Fair Value, Inputs, Level 3 [Member] | Money Market Funds [Member]
Assets	0	0
Fair Value, Inputs, Level 3 [Member] | Convertible Debt Securities [Member]
Assets	$ 1,000	1,000
Fair Value, Inputs, Level 3 [Member] | Contingent Consideration Liabilities [Member]
Liabilities		$ 1,914