BACKGROUND AND BASIS OF PRESENTATION	3 Months Ended
Dec. 31, 2018
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”') is a leading global supplier of consumable materials to semiconductor manufacturers and pipeline operators. On November 15, 2018 (“Acquisition Date”), we completed our acquisition of KMG Chemicals, Inc. (“KMG”) which produces and distributes specialty chemicals and performance materials for the semiconductor, industrial wood preservation, pipeline and energy industries (“Acquisition”). The Acquisition extends and strengthens our position as one of the leading suppliers of consumable materials to the semiconductor industry and expands our portfolio with the addition of KMG’s businesses, which we believe will enable us to be a leading global provider of performance products and services to the pipeline operations and energy industries. The Consolidated Financial Statements included in this Report on Form 10-Q include the financial results of KMG from the Acquisition Date. Subsequent to the Acquisition, we now operate our business within two reportable segments: Electronic Materials and Performance Materials. The Electronic Materials segment consists of our legacy CMP slurries and polishing pads businesses, as well as the recently-acquired KMG electronic chemicals business. The Performance Materials segment includes KMG’s legacy pipeline performance and wood treatment businesses, and our legacy QED business. For additional information, refer to Part 1, Item 1, “Business”, in our and KMG’s Annual Reports on Form 10-K for the fiscal year ended September 30, 2018 and July 31, 2018, respectively. The unaudited Consolidated Financial Statements have been prepared by Cabot Microelectronics pursuant to the rules of the Securities and Exchange Commission (SEC) and accounting principles generally accepted in the United States of America (U.S. GAAP). In the opinion of management, these unaudited Consolidated Financial Statements include all adjustments, consisting of normal recurring adjustments, necessary for the fair statement of Cabot Microelectronics’ financial position as of December 31, 2018, cash flows for the three months ended December 31, 2018 and December 31, 2017, and results of operations for the three months ended December 31, 2018 and December 31, 2017. The Consolidated Balance Sheets as of September 30, 2018 were derived from audited financial statements. The results of operations for the three months ended December 31, 2018 may not be indicative of results to be expected for future periods, including the fiscal year ending September 30, 2019. Certain prior period amounts have been reclassified to conform to the current period presentation. This Report on Form 10-Q does not contain all of the footnote disclosures from the annual financial statements and 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, 2018. 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, 2018. USE OF ESTIMATES The preparation of financial statements and related disclosures in conformity with U.S. GAAP requires management to make judgments, assumptions and estimates that affect the amounts reported in the Consolidated Financial Statements and accompanying notes. The accounting estimates that require management's most difficult and subjective judgments include, but are not limited to, those estimates related to bad debt expense, inventory valuation, impairment of long-lived assets and investments, business combinations, goodwill, other intangible assets, share-based compensation, income taxes and contingencies. We base our estimates on historical experience, current conditions and on various other assumptions that we believe are reasonable under the circumstances. However, future events are subject to change and estimates and judgments routinely require adjustment. Actual results may differ from these estimates under different assumptions or conditions.

1. BACKGROUND AND BASIS OF PRESENTATION

Cabot Microelectronics Corporation (“Cabot Microelectronics”, “the Company”, “us”, “we”, or “our”') is a leading global supplier of consumable materials to semiconductor manufacturers and pipeline operators. On November 15, 2018 (“Acquisition Date”), we completed our acquisition of KMG Chemicals, Inc. (“KMG”) which produces and distributes specialty chemicals and performance materials for the semiconductor, industrial wood preservation, pipeline and energy industries (“Acquisition”). The Acquisition extends and strengthens our position as one of the leading suppliers of consumable materials to the semiconductor industry and expands our portfolio with the addition of KMG’s businesses, which we believe will enable us to be a leading global provider of performance products and services to the pipeline operations and energy industries. The Consolidated Financial Statements included in this Report on Form 10-Q include the financial results of KMG from the Acquisition Date. Subsequent to the Acquisition, we now operate our business within two reportable segments: Electronic Materials and Performance Materials. The Electronic Materials segment consists of our legacy CMP slurries and polishing pads businesses, as well as the recently-acquired KMG electronic chemicals business. The Performance Materials segment includes KMG’s legacy pipeline performance and wood treatment businesses, and our legacy QED business. For additional information, refer to Part 1, Item 1, “Business”, in our and KMG’s Annual Reports on Form 10-K for the fiscal year ended September 30, 2018 and July 31, 2018, respectively.

The unaudited Consolidated Financial Statements have been prepared by Cabot Microelectronics pursuant to the rules of the Securities and Exchange Commission (SEC) and accounting principles generally accepted in the United States of America (U.S. GAAP). In the opinion of management, these unaudited Consolidated Financial Statements include all adjustments, consisting of normal recurring adjustments, necessary for the fair statement of Cabot Microelectronics’ financial position as of December 31, 2018, cash flows for the three months ended December 31, 2018 and December 31, 2017, and results of operations for the three months ended December 31, 2018 and December 31, 2017. The Consolidated Balance Sheets as of September 30, 2018 were derived from audited financial statements. The results of operations for the three months ended December 31, 2018 may not be indicative of results to be expected for future periods, including the fiscal year ending September 30, 2019. Certain prior period amounts have been reclassified to conform to the current period presentation. This Report on Form 10-Q does not contain all of the footnote disclosures from the annual financial statements and 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, 2018.

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, 2018.

USE OF ESTIMATES

The preparation of financial statements and related disclosures in conformity with U.S. GAAP requires management to make judgments, assumptions and estimates that affect the amounts reported in the Consolidated Financial Statements and accompanying notes. The accounting estimates that require management's most difficult and subjective judgments include, but are not limited to, those estimates related to bad debt expense, inventory valuation, impairment of long-lived assets and investments, business combinations, goodwill, other intangible assets, share-based compensation, income taxes and contingencies. We base our estimates on historical experience, current conditions and on various other assumptions that we believe are reasonable under the circumstances. However, future events are subject to change and estimates and judgments routinely require adjustment. Actual results may differ from these estimates under different assumptions or conditions.