Impairment - Wood Treatment - Narrative (Details) - USD ($)	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Long-lived asset impairment charges:
Intangible assets	$ 578,264,000	$ 623,794,000
Goodwill impairment	227,126,000
Goodwill	576,902,000	718,647,000	$ 710,071,000
Impairment tax benefit			17,072,000
Wood treatment
Long-lived asset impairment charges:
Total wood treatment long-lived asset impairment charges	3,266,000	2,314,000	67,372,000
Intangible assets	0
Goodwill impairment	25,576,000	0	$ 0
Goodwill	9,400,000
Impairment tax benefit	$ 606,000	$ 608,000