Document And Entity Information (USD $)	9 Months Ended
	Jun. 30, 2012	Jul. 31, 2012	Mar. 31, 2011
Entity Registrant Name	CABOT MICROELECTRONICS CORP
Entity Central Index Key	0001102934
Current Fiscal Year End Date	--09-30
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 1,203,000
Entity Common Stock, Shares Outstanding		23,318,215
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	Q3
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2012