FINANCIAL INFORMATION BY INDUSTRY SEGMENT, GEOGRAPHIC AREA AND PRODUCT LINE (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2010
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 110,621	$ 115,678	$ 99,236	$ 102,122	$ 109,731	$ 111,846	$ 109,660	$ 114,205	$ 427,657	$ 445,442	$ 408,201
Property, plant and equipment, net	125,020				130,791				125,020	130,791	115,811
Revenue from External Customer [Line Items]
Revenue	110,621	115,678	99,236	102,122	109,731	111,846	109,660	114,205	427,657	445,442	408,201
Tungsten slurries [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									161,756	164,098	147,788
Revenue from External Customer [Line Items]
Revenue									161,756	164,098	147,788
Dielectric slurries [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									119,320	121,543	117,484
Revenue from External Customer [Line Items]
Revenue									119,320	121,543	117,484
Copper slurries [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									67,157	76,285	75,898
Revenue from External Customer [Line Items]
Revenue									67,157	76,285	75,898
Polishing pads [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									33,725	31,045	29,909
Revenue from External Customer [Line Items]
Revenue									33,725	31,045	29,909
Data storage slurries [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									20,821	27,786	20,806
Revenue from External Customer [Line Items]
Revenue									20,821	27,786	20,806
Engineered Surface Finishes [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									24,878	24,685	16,316
Revenue from External Customer [Line Items]
Revenue									24,878	24,685	16,316
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									56,770	61,540	55,666
Property, plant and equipment, net	49,325				50,503				49,325	50,503	55,576
Revenue from External Customer [Line Items]
Revenue									56,770	61,540	55,666
Asia [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									342,958	356,074	327,202
Property, plant and equipment, net	75,690				80,280				75,690	80,280	60,235
Revenue from External Customer [Line Items]
Revenue									342,958	356,074	327,202
Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									27,929	27,828	25,333
Property, plant and equipment, net	5				8				5	8	0
Revenue from External Customer [Line Items]
Revenue									27,929	27,828	25,333
Japan [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									56,488	57,889	60,207
Property, plant and equipment, net	43,411				50,236				43,411	50,236	42,225
Revenue from External Customer [Line Items]
Revenue									56,488	57,889	60,207
Taiwan [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									124,732	132,089	129,533
Property, plant and equipment, net	18,397				17,577				18,397	17,577	17,542
Revenue from External Customer [Line Items]
Revenue									124,732	132,089	129,533
South Korea [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									68,573	56,321	42,669
Property, plant and equipment, net	12,580								12,580
Revenue from External Customer [Line Items]
Revenue									68,573	56,321	42,669
Singapore [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue										47,441	44,316
Revenue from External Customer [Line Items]
Revenue										$ 47,441	$ 44,316