Note 8 - Income Taxes (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Tax Expense (Benefit), Total	$ 1,692	$ 1,457
Deferred Tax Assets, Valuation Allowance, Total	1,942	1,942
Unrecognized Tax Benefits, Ending Balance	0	$ 0
General Business Tax Credit Carryforward [Member]
Tax Credit Carryforward, Amount	2,070
Domestic Tax Authority [Member] | Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards, Total	$ 47,755
Open Tax Year	2001 2002 2005 2006 2007 2011 2012 2013 2014 2015
Foreign Tax Authority [Member]
Deferred Tax Assets, Valuation Allowance, Total	$ 0
Open Tax Year	2010 2011 2012 2013 2014 2015 2016 2017 2018 2019
Foreign Tax Authority [Member] | Her Majesty's Revenue and Customs (HMRC) [Member]
Operating Loss Carryforwards, Total	$ 11,000
State and Local Jurisdiction [Member]
Open Tax Year	2001 2002 2005 2006 2007 2011 2012 2013 2014 2015 2016 2017 2018 2019