Note 13 - Income Taxes (Details Textual) - USD ($)			12 Months Ended
	Apr. 01, 2020	Apr. 01, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Discontinued Operation, Tax Effect of Discontinued Operation, Total			$ 39,435,000
Effective UK Corporate Tax Rate		19.00%	19.00%	19.30%	20.00%
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent			21.00%	34.00%	34.00%
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
Deferred Tax Assets, Net of Valuation Allowance, Total			$ 1,121,000	2,486,000
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense, Total			37,000	0	$ 0
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued, Total			37,000	0
Unrecognized Tax Benefits, Including Penalties and Interest			409,000	0
Research Tax Credit Carryforward [Member]
Income Tax Credits and Adjustments			0
State and Local Jurisdiction [Member]
Operating Loss Carryforwards, Total			$ 50,300,000	$ 154,900,000
Her Majesty's Revenue and Customs (HMRC) [Member]
Effective UK Corporate Tax Rate			19.00%	19.30%	20.00%
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Percent			121.50%	(5.00%)	(21.60%)
Operating Loss Carryforwards, Total			$ 2,900,000	$ 11,100,000
Deferred Tax Assets, Net of Valuation Allowance, Total			1,100,000
Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards, Total			$ 54,700,000	$ 160,500,000
Scenario, Forecast [Member]
Effective UK Corporate Tax Rate	17.00%
Earliest Tax Year [Member]
Open Tax Year					2014