Note 2 - Acquisitions (Details Textual) - USD ($) $ in Thousands			1 Months Ended	3 Months Ended			6 Months Ended	8 Months Ended	9 Months Ended		12 Months Ended	18 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Aug. 31, 2018	Mar. 31, 2019	Sep. 30, 2018	Sep. 30, 2017	Mar. 31, 2019	Mar. 31, 2019	Mar. 31, 2019	Mar. 31, 2018	Sep. 30, 2018	Mar. 31, 2019	Jun. 30, 2018
Payments to Acquire Businesses, Net of Cash Acquired, Total									$ 96,768	$ 10,397
Goodwill, Ending Balance				$ 260,443			$ 260,443	$ 260,443	260,443			$ 260,443	$ 211,751
Agile Magnetics [Member]
Payments to Acquire Businesses, Net of Cash Acquired, Total	$ 39,193						39,193
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill, Total	13,718			18,150	$ 13,718		18,150	18,150	18,150		$ 13,718	18,150
Goodwill, Ending Balance	20,142			15,614	20,142		15,614	15,614	15,614		20,142	15,614
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Intangibles							4,432
Agile Magnetics [Member] | Customer Relationships [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill, Total				14,300			14,300	14,300	14,300			14,300
Agile Magnetics [Member] | Trademarks [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill, Total				3,800			3,800	3,800	3,800			3,800
Agile Magnetics [Member] | Noncompete Agreements [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill, Total				100			100	100	100			100
Tenibac-Graphion, Inc. [Member]
Payments to Acquire Businesses, Net of Cash Acquired, Total	56,726		$ 57,300				56,726
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill, Total	15,960			16,904	15,960		16,904	16,904	16,904		15,960	16,904
Goodwill, Ending Balance	32,949			33,779	32,949		33,779	33,779	33,779		32,949	33,779
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Intangibles							944
Tenibac-Graphion, Inc. [Member] | Customer Relationships [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill, Total				11,300			11,300	$ 11,300	11,300			11,300
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life								9 years
Tenibac-Graphion, Inc. [Member] | Trademarks [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill, Total				4,200			4,200	$ 4,200	4,200			4,200
Tenibac-Graphion, Inc. [Member] | Other Intangible Assets [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill, Total				1,400			1,400	1,400	1,400			1,400
Piazza Rosa Group [Member]
Payments to Acquire Businesses, Net of Cash Acquired, Total		$ 10,056			900	$ 10,100						12,673
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill, Total		4,087		3,472		4,087	3,472	3,472	3,472			3,472
Goodwill, Ending Balance	$ 7,100	6,218		7,076	$ 7,100	6,218	$ 7,076	$ 7,076	7,076		7,100	7,076
Other Payments to Acquire Businesses						2,800					$ 2,600	2,617
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Intangibles						(600)						$ (615)
Piazza Rosa Group [Member] | Trademarks (Indefinite-Lived) [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill, Total		1,600				1,600
Piazza Rosa Group [Member] | Customer Relationships [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill, Total		2,300				$ 2,300
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life						8 years
Piazza Rosa Group [Member] | Other Intangible Assets [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill, Total		200				$ 200
Horizon Scientific Inc. [Member]
Business Combination, Deferred Compensation Due on Second Anniversary		3,000				3,000
Business Combination, Deferred Compensation Due on Third Anniversary		$ 5,600				$ 5,600
Business Combination, Deferred Compensation Arrangements				$ 700					$ 2,100