Note 3 - Fair Value Measurement - Financial Assets and Liabilities on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Liabilities	$ 0
Liabilities	0
Fair Value, Recurring [Member]
Assets	7,448
Assets	7,448
Liabilities	41,516
Liabilities	41,516
Fair Value, Recurring [Member] | Warrant Liabilities [Member]
Liabilities	39,602	$ 28,516
Liabilities	39,602	28,516
Fair Value, Recurring [Member] | Contingent Consideration Liabilities [Member]
Liabilities	1,914
Liabilities	1,914
Fair Value, Recurring [Member] | Money Market Funds [Member]
Assets	6,448	30,657
Assets	6,448	30,657
Fair Value, Recurring [Member] | Convertible Debt Securities [Member]
Assets	1,000
Assets	1,000
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Assets	6,448
Assets	6,448
Liabilities
Liabilities
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Warrant Liabilities [Member]
Liabilities
Liabilities
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Contingent Consideration Liabilities [Member]
Liabilities
Liabilities
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member]
Assets	6,448	30,657
Assets	6,448	30,657
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Convertible Debt Securities [Member]
Assets
Assets
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Assets
Assets
Liabilities
Liabilities
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Warrant Liabilities [Member]
Liabilities
Liabilities
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Contingent Consideration Liabilities [Member]
Liabilities
Liabilities
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Money Market Funds [Member]
Assets
Assets
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Convertible Debt Securities [Member]
Assets
Assets
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Assets	1,000
Assets	1,000
Liabilities	41,516
Liabilities	41,516
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Warrant Liabilities [Member]
Liabilities	39,602	28,516
Liabilities	39,602	28,516
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Contingent Consideration Liabilities [Member]
Liabilities	1,914
Liabilities	1,914
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Money Market Funds [Member]
Assets
Assets
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Convertible Debt Securities [Member]
Assets	1,000
Assets	$ 1,000