BACKGROUND AND BASIS OF PRESENTATION	3 Months Ended
Dec. 31, 2012
BACKGROUND AND BASIS OF PRESENTATION [Abstract]
BACKGROUND AND BASIS OF PRESENTATION	1. BACKGROUND AND BASIS OF PRESENTATION Cabot Microelectronics Corporation ("Cabot Microelectronics'', "the Company'', "us'', "we'' or "our'') supplies high-performance polishing slurries and pads used in the manufacture of advanced integrated circuit (IC) devices within the semiconductor industry, in a process called chemical mechanical planarization (CMP). CMP is a polishing process used by IC device manufacturers to planarize or flatten many of the multiple layers of material that are deposited upon silicon wafers in the production of advanced ICs. Our products play a critical role in the production of advanced IC devices, thereby enabling our customers to produce smaller, faster and more complex IC devices with fewer defects. We develop, produce and sell CMP slurries for polishing many of the conducting and insulating materials used in IC devices, and also for polishing the disk substrates and magnetic heads used in hard disk drives. We also develop, manufacture and sell CMP polishing pads, which are used in conjunction with slurries in the CMP process. We also pursue other demanding surface modification applications through our Engineered Surface Finishes (ESF) business where we believe we can leverage our expertise in CMP consumables for the semiconductor industry to develop products for demanding polishing applications in other industries. For additional information, refer to Part 1, Item 1, "Business", in our annual report on Form 10-K for the fiscal year ended September 30, 2012. The unaudited consolidated financial statements have been prepared by Cabot Microelectronics Corporation pursuant to the rules of the Securities and Exchange Commission (SEC) and accounting principles generally accepted in the United States of America. In the opinion of management, these unaudited consolidated financial statements include all normal recurring adjustments necessary for the fair presentation of Cabot Microelectronics' financial position as of December 31, 2012, cash flows for the three months ended December 31, 2012, and December 31, 2011, and results of operations for the three months ended December 31, 2012, and December 31, 2011. The results of operations for the three months ended December 31, 2012 may not be indicative of results to be expected for future periods, including the fiscal year ending September 30, 2013. These unaudited consolidated financial statements should be read in conjunction with the consolidated financial statements and related notes thereto included in Cabot Microelectronics' annual report on Form 10-K for the fiscal year ended September 30, 2012. The consolidated financial statements include the accounts of Cabot Microelectronics and its subsidiaries. All intercompany transactions and balances between the companies have been eliminated as of December 31, 2012. Results of Operations The results of operations for the quarter ended December 31, 2012 include a foreign tax adjustment to correct prior period amounts, which we determined to be immaterial to the prior periods to which it relates and is expected to be immaterial to our full fiscal year 2013 results. This adjustment reduced net income for the first quarter of fiscal 2013 by $1,686 and diluted earnings per share by approximately $0.07. This adjustment relates to the reversal of a deferred tax asset for cumulative net operating losses (NOLs) associated with our facility in South Korea since its opening in fiscal year 2011, as these NOLs are expected to be consumed during periods a tax holiday is in effect.

1. BACKGROUND AND BASIS OF PRESENTATION

Cabot Microelectronics Corporation ("Cabot Microelectronics'', "the Company'', "us'', "we'' or "our'') supplies high-performance polishing slurries and pads used in the manufacture of advanced integrated circuit (IC) devices within the semiconductor industry, in a process called chemical mechanical planarization (CMP). CMP is a polishing process used by IC device manufacturers to planarize or flatten many of the multiple layers of material that are deposited upon silicon wafers in the production of advanced ICs. Our products play a critical role in the production of advanced IC devices, thereby enabling our customers to produce smaller, faster and more complex IC devices with fewer defects. We develop, produce and sell CMP slurries for polishing many of the conducting and insulating materials used in IC devices, and also for polishing the disk substrates and magnetic heads used in hard disk drives. We also develop, manufacture and sell CMP polishing pads, which are used in conjunction with slurries in the CMP process. We also pursue other demanding surface modification applications through our Engineered Surface Finishes (ESF) business where we believe we can leverage our expertise in CMP consumables for the semiconductor industry to develop products for demanding polishing applications in other industries. For additional information, refer to Part 1, Item 1, "Business", in our annual report on Form 10-K for the fiscal year ended September 30, 2012.

The unaudited consolidated financial statements have been prepared by Cabot Microelectronics Corporation pursuant to the rules of the Securities and Exchange Commission (SEC) and accounting principles generally accepted in the United States of America. In the opinion of management, these unaudited consolidated financial statements include all normal recurring adjustments necessary for the fair presentation of Cabot Microelectronics' financial position as of December 31, 2012, cash flows for the three months ended December 31, 2012, and December 31, 2011, and results of operations for the three months ended December 31, 2012, and December 31, 2011. The results of operations for the three months ended December 31, 2012 may not be indicative of results to be expected for future periods, including the fiscal year ending September 30, 2013. These unaudited consolidated financial statements should be read in conjunction with the consolidated financial statements and related notes thereto included in Cabot Microelectronics' annual report on Form 10-K for the fiscal year ended September 30, 2012.

The consolidated financial statements include the accounts of Cabot Microelectronics and its subsidiaries. All intercompany transactions and balances between the companies have been eliminated as of December 31, 2012.

Results of Operations

The results of operations for the quarter ended December 31, 2012 include a foreign tax adjustment to correct prior period amounts, which we determined to be immaterial to the prior periods to which it relates and is expected to be immaterial to our full fiscal year 2013 results. This adjustment reduced net income for the first quarter of fiscal 2013 by $1,686 and diluted earnings per share by approximately $0.07. This adjustment relates to the reversal of a deferred tax asset for cumulative net operating losses (NOLs) associated with our facility in South Korea since its opening in fiscal year 2011, as these NOLs are expected to be consumed during periods a tax holiday is in effect.