FINANCIAL INFORMATION BY INDUSTRY SEGMENT, GEOGRAPHIC AREA AND PRODUCT LINE (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013	Mar. 31, 2012	Sep. 30, 2012
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 100,364	$ 99,236	$ 206,897	$ 201,358
Property, plant and equipment, net	112,632		112,632		125,020
Revenue from External Customer [Line Items]
Revenue	100,364	99,236	206,897	201,358
Tungsten slurry [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	36,819	38,218	77,525	78,946
Revenue from External Customer [Line Items]
Revenue	36,819	38,218	77,525	78,946
Dielectric slurry [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	29,734	27,209	60,092	55,216
Revenue from External Customer [Line Items]
Revenue	29,734	27,209	60,092	55,216
Copper slurry, including barrier and aluminum [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	17,057	16,061	35,041	32,101
Revenue from External Customer [Line Items]
Revenue	17,057	16,061	35,041	32,101
Polishing pads [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	7,402	7,939	15,866	14,869
Revenue from External Customer [Line Items]
Revenue	7,402	7,939	15,866	14,869
Data storage slurry [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	5,424	5,749	10,486	10,726
Revenue from External Customer [Line Items]
Revenue	5,424	5,749	10,486	10,726
Engineered Surface Finishes [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	3,928	4,060	7,887	9,500
Revenue from External Customer [Line Items]
Revenue	$ 3,928	$ 4,060	$ 7,887	$ 9,500