Goodwill and Other Intangible Assets - Changes in carrying amount of goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Changes in goodwill
Goodwill, Beginning Balance	$ 390,256	$ 361,900
Acquisition activity and other		(28,400)
Out-of-period adjustment	18,000
Foreign currency translation and other	(200)
Goodwill, Ending Balance	408,063	390,256
Aerospace & Defense
Changes in goodwill
Goodwill, Beginning Balance	102,200	73,700
Acquisition activity and other		(28,500)
Foreign currency translation and other	(100)
Goodwill, Ending Balance	102,100	102,200
USG
Changes in goodwill
Goodwill, Beginning Balance	254,000	254,100
Acquisition activity and other		(100)
Out-of-period adjustment	18,000
Foreign currency translation and other	(100)
Goodwill, Ending Balance	271,900	254,000
Test
Changes in goodwill
Goodwill, Beginning Balance	34,100	34,100
Acquisition activity and other		0
Out-of-period adjustment	0
Foreign currency translation and other	0
Goodwill, Ending Balance	$ 34,100	$ 34,100