Note 16 - Employee Benefit Plans (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Unites States Plan [Member]
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 250,000	$ 314,000
United Kingdom Plan [Member]
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 864,000	$ 685,000
Defined Contribution Plan Minimum Annual Contributions per Employee, Percent	5.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	5.00%