Note 2 - Revenue Recognition 1 (Details Textual) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenue, Performance Obligation Satisfied, Revenue Recognized, Percentage	78.00%	77.00%	79.00%	77.00%
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	$ 0.7	$ 0.8	$ 1.1