CONSOLIDATED STATEMENTS OF (LOSS) INCOME - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
Revenue	$ 1,199,831	$ 1,116,270	$ 1,037,696
Cost of sales	701,662	627,669	595,043
Gross profit	498,169	488,601	442,653
Operating expenses:
Research, development and technical	54,195	52,311	51,707
Selling, general and administrative	228,886	217,071	213,078
Impairment charges	230,392	2,314	67,372
Total operating expenses	513,473	271,696	332,157
Operating (loss) income	(15,304)	216,905	110,496
Interest expense, net	38,360	41,840	43,335
Other expense, net	(1,130)	(1,718)	(4,055)
(Loss) income before income taxes	(54,794)	173,347	63,106
Provision for income taxes	13,783	30,519	23,891
Net (loss) income	$ (68,577)	$ 142,828	$ 39,215
Basic (loss) earnings per share (in dollars per share)	$ (2.35)	$ 4.90	$ 1.37
Diluted (loss) earnings per share (in dollars per share)	$ (2.35)	$ 4.83	$ 1.35
Weighted average basic shares outstanding (in shares)	29,126,000	29,136,000	28,571,000
Weighted average diluted shares outstanding (in shares)	29,126,000	29,580,000	29,094,000