Impairment - Wood Treatment - Long-lived Asset Impairment (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of property, plant and equipment	$ 7,347	$ 0
Goodwill	4,081
Total Asset impairment charges	7,347	0
Wood Treatment
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of property, plant and equipment	91
Goodwill	4,081
Total Asset impairment charges	7,347	$ 0
Wood Treatment | Product technology
Impaired Long-Lived Assets Held and Used [Line Items]
Other intangible assets	583
Wood Treatment | Acquired patents and licenses
Impaired Long-Lived Assets Held and Used [Line Items]
Other intangible assets	173
Wood Treatment | Customer relationships, distribution rights, and other
Impaired Long-Lived Assets Held and Used [Line Items]
Other intangible assets	$ 2,419