Note 3 - Revenue - Disaggregation of Revenue by Major Categories and Geographic Location (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Net sales	$ 99,298	$ 102,893	$ 304,487	$ 311,324
UNITED STATES
Net sales	69,491	65,285	211,976	201,237
Non-US [Member]
Net sales	29,807	37,608	92,511	110,087
Pumps and Pump Systems [Member]
Net sales	86,114	89,835	260,913	268,485
Repair Parts for Pumps and Pump Systems and Other [Member]
Net sales	$ 13,184	$ 13,058	$ 43,574	$ 42,839

Amount, including tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value-added and excise.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130545-203045

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration