ACQUISITIONS - Assets Acquired and Liabilities Assumed Cornell Cookson (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Sep. 30, 2018	Jun. 04, 2018
Business Acquisition [Line Items]
Goodwill	$ 438,417	$ 439,395
Cornell Cookson [Member]
Business Acquisition [Line Items]
Accounts receivable			$ 30,400
Inventories			12,336
Property, plant and equipment			49,426
Goodwill			43,183
Intangible assets			67,600
Other current and non-current assets			2,648
Total assets acquired			205,593
Accounts payable and accrued liabilities			12,507
Long-term liabilities			660
Total liabilities assumed			13,167
Total			192,426
Gross accounts receivable			30,818
Allowance for accounts receivable			418
Gross inventory			13,434
Inventory reserves			$ 1,098