Goodwill and Other Intangible Assets - Narrative (Details) - USD ($)		3 Months Ended	12 Months Ended
	Jul. 01, 2021	Mar. 31, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Goodwill [Line Items]
Goodwill impairment			$ 227,126,000
Tax benefit			(13,783,000)	$ (30,519,000)	$ (23,891,000)
Intangible assets			578,264,000	623,794,000
Goodwill			576,902,000	718,647,000	710,071,000
Other intangible assets not subject to amortization			47,170,000	47,170,000
Amortization expense			81,083,000	85,557,000	59,931,000
PIM
Goodwill [Line Items]
Goodwill impairment	$ 0
Fair value in excess of carrying value, percent	5.00%
Wood treatment
Goodwill [Line Items]
Goodwill impairment			25,576,000	0	0
Intangible assets			0
Goodwill			9,400,000
Performance Materials
Goodwill [Line Items]
Goodwill impairment			227,126,000
Goodwill			132,669,000	$ 358,222,000	$ 357,274,000
PIM | Performance Materials
Goodwill [Line Items]
Goodwill impairment		$ 201,550,000
Tax benefit			23,539,000
Intangible assets			566,300,000
Goodwill			118,235,000
Other intangible assets not subject to amortization			$ 46,000,000