Note 3 - Balance Sheet Detail (Details Textual) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Capital Leased Assets, Gross, Total	$ 1,900,000	$ 1,900,000	$ 1,600,000
Capital Leases, Lessee Balance Sheet, Assets by Major Class, Accumulated Depreciation	1,100,000	1,100,000	700,000
Property, Plant and Equipment, Net, Ending Balance	2,672,000	2,672,000	2,096,000
Amortization of Intangible Assets, Total		0	2,000	$ 141,000
Loss Contingency Accrual, Product Liability, Net, Total	5,000,000	5,000,000
Product Liability Accrual, Period Expense	1,100,000
Extended Product Warranty Accrual, Current	3,159,000	3,159,000
Accrued Liabilities, Current [Member]
Loss Contingency Accrual, Product Liability, Net, Total	800,000	800,000
Construction in Progress [Member]
Property, Plant and Equipment, Net, Ending Balance	$ 0.40	$ 0.40