Note 16 - Income Taxes (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	21.00%
Operating Loss Carryforwards, Annual Limitations	$ 62,000
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	(35,300,000)	$ 25,700,000
Unrecognized Tax Benefits, Ending Balance	851,000	1,582,000	$ 1,404,000
Domestic Tax Authority [Member]
Operating Loss Carryforwards, Total	18,000,000	92,300,000
Domestic Tax Authority [Member] | Research Tax Credit Carryforward [Member]
Tax Credit Carryforward, Amount	$ 100,000	3,000,000
Domestic Tax Authority [Member] | Internal Revenue Service (IRS) [Member]
Open Tax Year	2016
State and Local Jurisdiction [Member]
Operating Loss Carryforwards, Total	$ 1,600,000	76,900,000
Open Tax Year	2015
State and Local Jurisdiction [Member] | Research Tax Credit Carryforward [Member]
Tax Credit Carryforward, Amount	$ 2,700,000	$ 2,300,000
Foreign Tax Authority [Member]
Open Tax Year	2014 2015 2016 2017 2018 2019
Foreign Tax Authority [Member] | Australian Taxation Office [Member]
Operating Loss Carryforwards, Total	$ 10,100,000