Note 5 - Income Taxes (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		34.00%	34.00%	34.00%
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability		$ (1,200)
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent		(14.20%)	0.00%	0.00%
Income Tax Reconciliation, Foreign Income Tax Witholdings		7.10%	0.00%	0.00%
Effective Income Tax Rate Reconciliation, Percent		25.10%	33.10%	(12.20%)
Income Tax Examination, Penalties and Interest Accrued		$ 0	$ 0
Internal Revenue Service (IRS) [Member] | Domestic Tax Authority [Member]
Tax Credit Carryforward, Amount		0
California Franchise Tax Board [Member] | State and Local Jurisdiction [Member]
Tax Credit Carryforward, Amount		$ 731
Maximum [Member]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		35.00%
Minimum [Member] | Scenario, Forecast [Member]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%