Goodwill and Other Intangible Assets - Changes in carrying amount of goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Changes in goodwill
Goodwill, Beginning Balance	$ 408,063	$ 390,300
Acquisition activity	97,400
Foreign currency translation and other	(600)	(200)
Goodwill, Ending Balance	504,853	408,063
Out-of-period adjustment		18,000
USG
Changes in goodwill
Goodwill, Beginning Balance	271,900	254,000
Acquisition activity	95,200
Foreign currency translation and other	(600)	(100)
Goodwill, Ending Balance	366,500	271,900
Out-of-period adjustment		18,000
Test
Changes in goodwill
Goodwill, Beginning Balance	34,100	34,100
Goodwill, Ending Balance	34,100	34,100
A&D
Changes in goodwill
Goodwill, Beginning Balance	102,100	102,200
Acquisition activity	2,200
Foreign currency translation and other		(100)
Goodwill, Ending Balance	$ 104,300	$ 102,100