Note 14 - Income Taxes (Details Textual) - USD ($)			12 Months Ended
	Apr. 01, 2020	Apr. 01, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Translation Adjustment Functional to Reporting Currency, Tax Expense (Benefit)			$ (200,000)
Discontinued Operation, Tax Effect of Discontinued Operation, Total				$ 39,435,000
Effective UK Corporate Tax Rate		19.00%	19.00%	19.00%
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent			21.00%	21.00%
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Percent					17.00%
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability					$ 21,400,000
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount			$ (1,864,000)	$ (30,107,000)
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense, Total			0	37,000
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued, Total			37,000	37,000
Unrecognized Tax Benefits, Including Penalties and Interest			37,000	409,000
Research Tax Credit Carryforward [Member]
Income Tax Credits and Adjustments			0
State and Local Jurisdiction [Member]
Operating Loss Carryforwards, Total			$ 40,500,000	$ 50,300,000
Her Majesty's Revenue and Customs (HMRC) [Member]
Effective UK Corporate Tax Rate			19.00%	19.00%
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Percent			49.60%	121.50%
Operating Loss Carryforwards, Total			$ 6,700,000	$ 2,900,000
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount			1,600,000
Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards, Total			54,300,000	$ 54,700,000
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount			$ (3,500,000)
Forecast [Member]
Effective UK Corporate Tax Rate	17.00%