Note 2 - Acquisitions - Components of Fair Value of Acquisitions and Allocation of Purchase Price For Acquisition of GS Engineering (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
	Jun. 30, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019
Payments to Acquire Businesses, Net of Cash Acquired, Total		$ (0)	$ 96,828
Goodwill, Ending Balance	$ 281,503	281,149		$ 281,149
GS Engineering [Member]
Cash payments	30,502	30,502		30,500
Less, cash acquired	(622)	(622)
Payments to Acquire Businesses, Net of Cash Acquired, Total	29,880	29,880
Other acquired assets	2,197	2,125		2,125
Other acquired assets		(72)
Inventories	228	153		153
Inventories, Adjustments		(75)
Customer Backlog	180	180		180
Property, plant, & equipment	1,391	1,391		1,391
Identifiable intangible assets	8,910	8,910		8,910
Goodwill, Ending Balance	17,976	18,123		18,123
Goodwill, Adjustments		147
Liabilities assumed	$ (1,002)	$ (1,002)		$ (1,002)