Note 11 - Income Taxes (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income (Loss) from Continuing Operations before Income Taxes, Domestic	$ 8,700,000	$ 11,100,000
Income (Loss) from Continuing Operations before Income Taxes, Foreign	$ 1,300,000	$ 1,600,000
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	21.00%
Deferred Tax Assets, Valuation Allowance, Total	$ 10,486,000	$ 9,808,000
Deferred Tax Assets, Net, Total	22,866,000	18,334,000
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued, Total	800,000	800,000
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense (Reversal)	(1,000)	84,000
Unrecognized Tax Benefits, Ending Balance	13,615,000	13,292,000	$ 12,889,000
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	7,900,000
Unrecognized Tax Benefits In Long Term Liabilities	2,900,000
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued in Long Term Liabilities	800,000
Unrecognized Tax Benefits In Deferred Tax Assets	11,500,000
Unrecognized Tax Benefits In Deferred Tax Asset Subject To Full Valuation Allowance	5,800,000
California R&D Tax Credits [Member]
Deferred Tax Assets, Valuation Allowance, Total	10,400,000	$ 9,700,000
Domestic Tax Authority [Member]
Tax Credit Carryforward, Amount	14,300,000
Domestic Tax Authority [Member] | Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards, Total	18,000,000
State and Local Jurisdiction [Member]
Tax Credit Carryforward, Amount	18,900,000
State and Local Jurisdiction [Member] | California Franchise Tax Board [Member]
Operating Loss Carryforwards, Total	6,300,000
State and Local Jurisdiction [Member] | California Franchise Tax Board [Member] | Syntricity [Member]
Operating Loss Carryforwards, Total	$ 100,000