GOODWILL AND OTHER INTANGIBLE ASSETS (Details) - USD ($) $ in Thousands		3 Months Ended			9 Months Ended
		Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Sep. 30, 2017
Goodwill [Roll Forward]
Balance, beginning of period					$ 101,932
Foreign exchange fluctuations					(178)
Decrease due to sale of surface finishes					(695)
Balance, end of period		$ 101,059			101,059
Sale of Productive Assets [Abstract]
(Gain) on sale of assets					(956)	$ 0
Finite-Lived Intangible Assets, Net [Abstract]
Total other intangible assets subject to amortization, gross carrying amount		85,154			85,154		$ 81,336
Accumulated amortization		49,342			49,342		43,816
Indefinite-lived Intangible Assets [Abstract]
Total other intangible assets not subject to amortization		1,170			1,170		5,190
Total other intangible assets, gross carrying amount		86,324			86,324		86,526
Other intangible assets [Abstract]
Amortization expense		1,780		$ 1,935	5,716	$ 5,860
Estimated future amortization expense [Abstract]
Remainder of 2018		1,780			1,780
2019		7,119			7,119
2020		7,115			7,115
2021		7,108			7,108
2022		7,108			7,108
Engineered Surface Finishes [Member]
Sale of Productive Assets [Abstract]
Net proceeds from sale of certain ESF			$ 3,277
Cash held in escrow			250
(Gain) on sale of assets			$ (956)
In-process Technology [Member]
Indefinite-lived Intangible Assets [Abstract]
Total other intangible assets not subject to amortization		0			0		4,000
Other Indefinite-lived Intangibles [Member]
Indefinite-lived Intangible Assets [Abstract]
Total other intangible assets not subject to amortization	[1]	1,170			1,170		1,190
Product Technology [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Total other intangible assets subject to amortization, gross carrying amount		46,273			46,273		42,287
Accumulated amortization		21,444			21,444		17,604
Acquired Patents and Licenses [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Total other intangible assets subject to amortization, gross carrying amount		8,270			8,270		8,270
Accumulated amortization		8,250			8,250		8,241
Trade Secrets and Know-how [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Total other intangible assets subject to amortization, gross carrying amount		2,550			2,550		2,550
Accumulated amortization		2,550			2,550		2,550
Customer Relationships, Distribution Rights and Other
Finite-Lived Intangible Assets, Net [Abstract]
Total other intangible assets subject to amortization, gross carrying amount		28,061			28,061		28,229
Accumulated amortization		$ 17,098			$ 17,098		$ 15,421

[1] Other indefinite-lived intangible assets not subject to amortization consist primarily of trade names.