Note 2 - Revenue Recognition 1 (Details Textual) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Revenue, Performance Obligation Satisfied, Revenue Recognized, Percentage	80.00%	78.00%
Minimum [Member]
Warranty Period (Year)	1 year
Contract with Customer, Payment Term (Day)	30 days
Maximum [Member]
Warranty Period (Year)	3 years
Extended Service Warranty, Term (Year)	4 years
Contract with Customer, Payment Term (Day)	60 days
Grant [Member]
Revenues, Total		$ 0.4