Acquisitions (Details) - USD ($) $ in Thousands			12 Months Ended
	Jul. 02, 2019	Mar. 14, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2020
Business Acquisition [Line Items]
Purchase price, net of cash acquired			$ 95,840	$ 9,813
Deferred Tax Liabilities, Goodwill			1,450		$ 7,878
Goodwill			$ 390,256	$ 361,900	$ 408,063
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	$ 28,500
Manta Test Systems Inc [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross		$ 9,500
Goodwill		3,500
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Buildings		3,500
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment		200
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables		400
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Inventory		$ 1,100
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life		13 years
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accounts Payable		$ 400
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Indefinite-Lived Intangible Assets		$ 1,200
Globe Composite Solutions, LLC [Member]
Business Acquisition [Line Items]
Purchase price, net of cash acquired	95,000
Revenues	37,000
Deferred Tax Liabilities, Goodwill	25,000
Customer contract assets	2,800
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Buildings	56,700
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	59,700
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment	6,300
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables	3,500
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Inventory	$ 3,500
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	20 years
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accounts Payable	$ 10,500
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Indefinite-Lived Intangible Assets	$ 3,700