Wood Treatment - Narrative (Details) - USD ($)	3 Months Ended			6 Months Ended
	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021	Sep. 30, 2021
Impaired Long-Lived Assets Held and Used [Line Items]
Goodwill, impairment loss				$ 9,435,000
Goodwill	$ 564,279,000			564,279,000		$ 576,902,000
Provision for (benefit from) income taxes	10,979,000		$ (16,109,000)	$ 14,196,000	$ (8,563,000)
Wood treatment
Impaired Long-Lived Assets Held and Used [Line Items]
Goodwill, impairment loss		$ 9,435,000	6,671,000		10,752,000
Goodwill		$ 0
Goodwill and long lived asset impairment charges			6,671,000		14,018,000
Provision for (benefit from) income taxes	$ 0		$ 0		$ 0