Note 11 - Commitments and Contingencies (Details Textual) $ in Thousands		12 Months Ended
	Oct. 09, 2015 USD ($) ft²	Dec. 31, 2017 USD ($) ft²	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Operating Leases, Rent Expense		$ 1,800	$ 1,300	$ 1,300
Standard and Extended Product Warranty Accrual		0	$ 0
European Headquarters Facility [Member]
Area of Real Estate Property | ft²	33,000
Lessee Leasing Arrangements, Term of Contract	15 years
Lessee Leasing Arrangements, Number of Renewal Terms	3
Lessee Leasing Arrangements, Renewal Term	6 years
Lessee Leasing Arrangements Ability to Withdraw With Penalty	6 years
Lessee Leasing Arrangements Ability to Withdrawn Without Penalty	9 years
Lessee Leasing Arrangements Initial Yearly Rent	$ 300
Construction in Progress, Gross		3,100
European Headquarters Facility [Member] | Deposits and Other Assets, Noncurrent [Member]
Lessee Leasing Arrangements, Additional Tenant Improvements		$ 800
Abano Terme, Italy [Member]
Area of Real Estate Property | ft²		28,000