Note 11 - Business Segment Information - Net Sales from External Customers by Product Category (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Net sales	$ 378,316	$ 348,967	$ 398,179
Pumps and Pump Systems [Member]
Net sales	321,263	300,906	341,304
Repairs and Other [Member]
Net sales	$ 57,053	$ 48,061	$ 56,875