CONSOLIDATED STATEMENTS OF INCOME (LOSS) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021
Income Statement [Abstract]
Revenue	$ 324,127	$ 290,528	$ 641,173	$ 578,391
Cost of sales	195,904	166,782	387,114	331,741
Gross profit	128,223	123,746	254,059	246,650
Operating expenses:
Research, development and technical	12,337	12,925	25,665	25,353
Selling, general and administrative	47,111	58,538	103,594	114,458
Impairment charges	0	208,221	9,435	215,568
Entegris Transaction-related expenses	12,243	0	18,293	0
Total operating expenses	71,691	279,684	156,987	355,379
Operating income (loss)	56,532	(155,938)	97,072	(108,729)
Interest expense, net	9,537	9,495	19,280	19,080
Other (expense) income, net	(1,445)	(484)	(1,597)	968
Income (loss) before income taxes	45,550	(165,917)	76,195	(126,841)
Provision for (benefit from) income taxes	10,979	(16,109)	14,196	(8,563)
Net income (loss)	$ 34,571	$ (149,808)	$ 61,999	$ (118,278)
Basic earnings (loss) per share (in dollars per share)	$ 1.21	$ (5.13)	$ 2.17	$ (4.06)
Diluted earnings (loss) per share (in dollars per share)	$ 1.19	$ (5.13)	$ 2.14	$ (4.06)
Weighted average basic shares outstanding (in shares)	28,609	29,210	28,526	29,164
Weighted average diluted shares outstanding (in shares)	28,999	29,210	28,909	29,164