Note 2 - Acquisitions - Estimated Fair Values of Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Sep. 30, 2021	May 06, 2021	Mar. 31, 2021	Oct. 01, 2020
Goodwill	$ 43,471		$ 34,634
Neeltran Inc. [Member]
Cash and short-term investments		$ 500
Net working capital (excluding inventory and deferred revenue)		(900)
Inventory		9,000
Property, plant and equipment		6,500
Deferred revenue		(10,000)
Deferred tax liability		2,300
Net tangible assets/(liabilities)		2,800
Net identifiable intangible assets/(liabilities)		4,800
Goodwill		8,800
Total purchase consideration		16,400
Net working capital (excluding inventory and deferred revenue)		(900)
Neeltran Inc. [Member] | Trademarks and Trade Names [Member]
Trade names and trademarks		1,200
Neeltran Inc. [Member] | Backlog [Member]
Finite-lived Intangibles Assets		100
Neeltran Inc. [Member] | Customer Relationships [Member]
Finite-lived Intangibles Assets		$ 3,500
Northeast Power Systems, Inc (NEPSI) [Member]
Net working capital (excluding inventory and deferred revenue)				$ 100
Inventory				4,200
Property, plant and equipment				2,300
Deferred revenue				(2,700)
Deferred tax liability				1,700
Net tangible assets/(liabilities)				2,200
Net identifiable intangible assets/(liabilities)				7,300
Goodwill				32,900
Total purchase consideration				42,400
Net working capital (excluding inventory and deferred revenue)				100
Northeast Power Systems, Inc (NEPSI) [Member] | Trademarks and Trade Names [Member]
Trade names and trademarks				600
Northeast Power Systems, Inc (NEPSI) [Member] | Backlog [Member]
Finite-lived Intangibles Assets				600
Northeast Power Systems, Inc (NEPSI) [Member] | Trade Names [Member]
Trade names and trademarks				600
Northeast Power Systems, Inc (NEPSI) [Member] | Customer Relationships [Member]
Finite-lived Intangibles Assets				$ 6,100