Note 2 - Summary of Significant Accounting Policies - Customer Contract Liabilities (Details) - USD ($)	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Customer contract liabilities	$ 552,000	$ 686,000
Change in customer contract liabilities	(134,000)
Marketing Programs [Member]
Customer contract liabilities	552,000	639,000
Change in customer contract liabilities	(87,000)
Product and Service, Other [Member]
Customer contract liabilities		$ 47,000
Change in customer contract liabilities	$ (47,000)