Note 2 - Summary of Significant Accounting Policies (Details Textual) $ / shares in Units, shares in Thousands, $ in Thousands		12 Months Ended
	Feb. 14, 2018 USD ($) $ / shares	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares
Certificates of Deposit, at Carrying Value		$ 4,600
Depreciation, Depletion and Amortization, Nonproduction		2,800	$ 2,300	$ 1,700
Public Utilities, Property, Plant and Equipment, Equipment		500	$ 1,200
Other Comprehensive Income (Loss), before Tax, Portion Attributable to Parent		$ 5,900
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount | shares		0	0	81
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, before Tax, Portion Attributable to Parent		$ (238)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax		$ (157)
Number of Operating Segments		1
Common Stock, Dividends, Per Share, Declared | $ / shares		$ 0.60	$ 0.60	$ 0.60
Subsequent Event [Member]
Common Stock, Dividends, Per Share, Declared | $ / shares	$ 0.15
Dividends Payable	$ 824
Dividends Payable, Date to be Paid	Mar. 09, 2018
Dividends Payable, Date of Record	Feb. 26, 2018
Credit Concentration Risk [Member] | Accounts Receivable [Member] | Customer One [Member]
Concentration Risk, Percentage		23.00%	34.00%	11.00%
Credit Concentration Risk [Member] | Sales Revenue, Net [Member] | Customer One [Member]
Concentration Risk, Percentage		10.00%
Customer Concentration Risk [Member] | Sales Revenue, Net [Member]
Number of Major Customers		1	1
Patents [Member]
Amortization		$ 37	$ 36	$ 32
Finite-Lived Intangible Asset, Useful Life		20 years
Legal Cost Capitalized		$ 711	715	670
Patents [Member] | Maximum [Member]
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months		50
Finite-Lived Intangible Assets, Amortization Expense, Year Two		50
Finite-Lived Intangible Assets, Amortization Expense, Year Three		50
Finite-Lived Intangible Assets, Amortization Expense, Year Four		50
Finite-Lived Intangible Assets, Amortization Expense, Year Five		$ 50
Software Development [Member]
Property, Plant and Equipment, Useful Life		5 years
Software Development Cost Capitalized		$ 511	315	364
Amortization		$ 418	$ 435	$ 422