Note 3 - Revenue (Details Textual) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Contract with Customer, Liability, Current	$ 7.7	$ 5.9
Other Current Liabilities [Member] | Maintenance [Member]
Contract with Customer, Liability, Current	7.7	5.9
Other Liabilities [Member] | Maintenance [Member]
Contract with Customer, Liability, Noncurrent	$ 3.5	$ 3.4
Short-term Contract with Customer [Member]
Standard Prepaid Maintenance Contract Time Period (Month)	12 months
Long-term Contract with Customer [Member]
Standard Prepaid Maintenance Contract Time Period (Month)	60 months