Note 2 - Summary of Significant Accounting Policies - Customer Contract Liabilities (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Customer contract liabilities	$ 679,000	$ 686,000
Change in customer contract liabilities	(7,000)
Marketing Programs [Member]
Customer contract liabilities	627,000	639,000
Change in customer contract liabilities	(12,000)
Product and Service, Other [Member]
Customer contract liabilities	52,000	$ 47,000
Change in customer contract liabilities	$ 5,000