Segment Reporting - Capital Expenditures (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021
Segment Reporting Information [Line Items]
Capital expenditures	$ 9,938	$ 9,715	$ 20,478	$ 19,934
Operating segment \| Electronic Materials
Segment Reporting Information [Line Items]
Capital expenditures	6,229	6,258	13,365	11,692
Operating segment \| Performance Materials
Segment Reporting Information [Line Items]
Capital expenditures	419	957	2,029	2,267
Corporate
Segment Reporting Information [Line Items]
Capital expenditures	$ 3,289	$ 2,500	$ 5,083	$ 5,975

The cash outflow for purchases of and capital improvements on property, plant and equipment (capital expenditures), software, and other intangible assets.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3213-108585

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 50
-Section 30
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=123362884&loc=d3e9212-128498

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 50
-Section 30
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=123362884&loc=d3e9215-128498

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 50
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=123385561&loc=d3e9135-128495

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