FINANCIAL INFORMATION BY INDUSTRY SEGMENT, GEOGRAPHIC AREA AND PRODUCT LINE, SEGMENT REPORTING INFORMATION BY PRODUCT TYPE (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2015 Segment	Mar. 31, 2014	Mar. 31, 2015	Mar. 31, 2014
FINANCIAL INFORMATION BY INDUSTRY SEGMENT, GEOGRAPHIC AREA AND PRODUCT LINE [Abstract]
Number of segments	1
Revenue from External Customer [Line Items]
Revenue	$ 104,858	$ 99,456	$ 216,792	$ 199,971
Tungsten slurries [Member]
Revenue from External Customer [Line Items]
Revenue	43,658	37,559	88,802	74,928
Dielectric slurries [Member]
Revenue from External Customer [Line Items]
Revenue	23,882	29,121	52,065	59,067
Other Metals slurries [Member]
Revenue from External Customer [Line Items]
Revenue	18,331	17,336	38,228	35,141
Polishing pads [Member]
Revenue from External Customer [Line Items]
Revenue	8,841	7,760	17,603	15,170
Data storage slurries [Member]
Revenue from External Customer [Line Items]
Revenue	3,934	4,486	8,300	9,468
Engineered Surface Finishes [Member]
Revenue from External Customer [Line Items]
Revenue	$ 6,212	$ 3,194	$ 11,794	$ 6,197