Note 6 - Deferred Service Contract Revenue (Details Textual) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Deferred Revenue Costs Incurred	$ 1.2	$ 1.7	$ 4.2	$ 4.9