LONG-LIVED ASSET IMPAIRMENT -WOOD TREATMENT - Long-lived Asset Impairment (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Impaired Long-Lived Assets Held and Used [Line Items]
Property, plant and equipment, net	$ 362,067	$ 276,818	$ 111,403
Other intangible assets	623,794	706,874
Acquired patents and licenses
Impaired Long-Lived Assets Held and Used [Line Items]
Other intangible assets	208	626
Wood Treatment
Impaired Long-Lived Assets Held and Used [Line Items]
Property, plant and equipment, net	450
Other intangible assets	3,800
Total long-lived assets	2,314	67,372
Wood Treatment | Product technology
Impaired Long-Lived Assets Held and Used [Line Items]
Other intangible assets	343	9,651
Wood Treatment | Acquired patents and licenses
Impaired Long-Lived Assets Held and Used [Line Items]
Other intangible assets	102	1,689
Wood Treatment | Customer relationships, distribution rights, and other
Impaired Long-Lived Assets Held and Used [Line Items]
Other intangible assets	$ 1,419	$ 51,969