Cover Page - shares	6 Months Ended
	Mar. 31, 2020	Apr. 30, 2020
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2020
Document Transition Report	false
Entity File Number	000-30205
Entity Registrant Name	CABOT MICROELECTRONICS CORPORATION
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	36-4324765
Entity Address, Address Line One	870 North Commons Drive
Entity Address, City or Town	Aurora
Entity Address, State or Province	IL
Entity Address, Postal Zip Code	60504
City Area Code	630
Local Phone Number	375-6631
Title of 12(b) Security	Common Stock, par value $0.001 per share
Trading Symbol	CCMP
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		29,063,259
Entity Central Index Key	0001102934
Current Fiscal Year End Date	--09-30
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2