CMC Materials (CCMP) 10-K 15 Nov 17 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Sep. 30, 2017	Oct. 31, 2017	Mar. 31, 2017
Document and Entity Information [Abstract]
Entity Registrant Name	CABOT MICROELECTRONICS CORP
Entity Central Index Key	1,102,934
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			$ 1,894,517,878
Entity Common Stock, Shares Outstanding		25,356,916
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Document Type	10-K
Amendment Flag	false
Document Period End Date	Sep. 30, 2017

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
CONSOLIDATED STATEMENTS OF INCOME [Abstract]
Revenue	$ 136,784	$ 127,957	$ 119,184	$ 123,254	$ 122,684	$ 108,152	$ 99,244	$ 100,369	$ 507,179	$ 430,449	$ 414,097
Cost of goods sold	66,734	65,414	59,153	61,749	61,598	56,127	52,348	50,174	253,050	220,247	201,866
Gross profit	70,050	62,543	60,031	61,505	61,086	52,025	46,896	50,195	254,129	210,202	212,231
Operating expenses:
Research, development and technical	13,839	14,333	14,090	13,396	15,842	12,928	14,934	14,828	55,658	58,532	59,778
Selling and marketing	8,680	7,346	7,268	7,552	8,057	6,243	6,668	6,749	30,846	27,717	24,983
General and administrative	14,489	13,953	14,699	12,496	11,454	10,738	12,990	14,263	55,637	49,445	52,430
Total operating expenses	37,008	35,632	36,057	33,444	35,353	29,909	34,592	35,840	142,141	135,694	137,191
Operating income	33,042	26,911	23,974	28,061	25,733	22,116	12,304	14,355	111,988	74,508	75,040
Interest expense	1,127	1,117	1,135	1,150	1,187	1,178	1,191	1,167	4,529	4,723	4,524
Other income (expense), net	798	(115)	234	996	257	(246)	452	190	1,913	653	681
Income before income taxes	32,713	25,679	23,073	27,907	24,803	20,692	11,565	13,378	109,372	70,438	71,197
Provision for income taxes	6,211	5,740	4,793	5,676	4,096	1,990	2,434	2,069	22,420	10,589	15,051
Net income	$ 26,502	$ 19,939	$ 18,280	$ 22,231	$ 20,707	$ 18,702	$ 9,131	$ 11,309	$ 86,952	$ 59,849	$ 56,146
Basic earnings per share (in dollars per share)	$ 1.05	$ 0.79	$ 0.73	$ 0.90	$ 0.85	$ 0.78	$ 0.38	$ 0.46	$ 3.47	$ 2.47	$ 2.32
Weighted-average basic shares outstanding (in shares)	25,236,000	25,228,000	25,031,000	24,583,000	24,234,000	23,929,000	24,061,000	24,142,000	25,015,458	24,076,549	24,039,692
Diluted earnings per share (in dollars per share)	$ 1.03	$ 0.77	$ 0.71	$ 0.88	$ 0.83	$ 0.76	$ 0.37	$ 0.46	$ 3.40	$ 2.43	$ 2.26
Weighted-average diluted shares outstanding (in shares)	25,710,000	25,721,000	25,526,000	25,072,000	24,678,000	24,325,000	24,408,000	24,549,000	25,512,487	24,476,993	24,631,815
Dividends per share (in dollars per share)	$ 0.20	$ 0.20	$ 0.20	$ 0.18	$ 0.18	$ 0.18	$ 0.18	$ 0	$ 0.78	$ 0.54	$ 0

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME [Abstract]
Net income	$ 86,952	$ 59,849	$ 56,146
Other comprehensive income (loss), net of tax
Foreign currency translation adjustments	(6,746)	15,996	(14,126)
Minimum pension liability adjustment	276	(434)	(318)
Net unrealized gain (loss) on cash flow hedges	863	84	(901)
Other comprehensive income (loss), net of tax	(5,607)	15,646	(15,345)
Comprehensive income	$ 81,345	$ 75,495	$ 40,801

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016
Current assets:
Cash and cash equivalents	$ 397,890	$ 287,479
Accounts receivable, less allowance for doubtful accounts of $1,747 at September 30, 2017, and $1,828 at September 30, 2016	64,793	62,830
Inventories	71,873	72,123
Prepaid expenses and other current assets	16,426	14,398
Total current assets	550,982	436,830
Property, plant and equipment, net	106,361	106,496
Goodwill	101,932	100,639
Other intangible assets, net	42,710	50,476
Deferred income taxes	21,598	20,747
Other long-term assets	10,517	12,042
Total assets	834,100	727,230
Current liabilities:
Accounts payable	17,624	16,834
Current portion of long-term debt	10,938	7,656
Accrued expenses, income taxes payable and other current liabilities	62,651	41,395
Total current liabilities	91,213	65,885
Long-term debt, net of current portion, less prepaid debt issuance cost of $441 at September 30, 2017 and $696 at September 30, 2016	132,997	146,961
Deferred income taxes	63	75
Other long-term liabilities	14,790	16,661
Total liabilities	239,063	229,582
Commitments and contingencies (Note 18)
Stockholders' equity:
Common Stock: Authorized: 200,000,000 shares, $0.001 par value; Issued: 35,230,742 shares at September 30, 2017, and 34,261,304 shares at September 30, 2016	35	34
Capital in excess of par value of common stock	580,938	530,840
Retained earnings	397,881	330,776
Accumulated other comprehensive income	3,949	9,556
Treasury stock at cost, 9,948,190 shares at September 30, 2017, and 9,744,642 shares at September 30, 2016	(387,766)	(373,558)
Total stockholders' equity	595,037	497,648
Total liabilities and stockholders' equity	$ 834,100	$ 727,230

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016
Current assets:
Allowance for doubtful accounts	$ 1,747	$ 1,828
LIABILITIES AND STOCKHOLDERS' EQUITY
Long-term debt, prepaid debt issuance cost	$ 441	$ 696
Stockholders' equity:
Common stock: Authorized (in shares)	200,000,000	200,000,000
Common stock: par value (in dollars per share)	$ 0.001	$ 0.001
Common stock: Issued (in shares)	35,230,742	34,261,304
Treasury stock at cost (in shares)	9,948,190	9,744,642

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Cash flows from operating activities:
Net income	$ 86,952	$ 59,849	$ 56,146
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	25,930	26,031	18,719
Provision for doubtful accounts	26	588	(84)
Share-based compensation expense	13,004	13,787	16,445
Deferred income tax expense (benefit)	392	(1,757)	869
Non-cash foreign exchange (gain)/loss	435	(1,144)	1,391
(Gain)/Loss on disposal of property, plant and equipment	(1,820)	103	(28)
Impairment of assets	860	1,079	0
Other	188	815	(524)
Changes in operating assets and liabilities, excluding amounts related to acquisition:
Accounts receivable	(3,986)	(8,017)	9,013
Inventories	(1,220)	3,351	(8,290)
Prepaid expenses and other assets	(1,576)	3,935	(3,662)
Accounts payable	892	(478)	801
Accrued expenses, income taxes payable and other liabilities	21,292	(2,931)	7,390
Net cash provided by operating activities	141,369	95,211	98,186
Cash flows from investing activities:
Additions to property, plant and equipment	(21,174)	(17,670)	(13,812)
Proceeds from the sale of property, plant and equipment	1,216	17	201
Acquisition of business, net of cash acquired	0	(126,976)	0
Proceeds from the sale of investments	175	200	202
Net cash used in investing activities	(19,783)	(144,429)	(13,409)
Cash flows from financing activities:
Repayment of long-term debt	(10,938)	(8,750)	(8,750)
Dividends paid	(19,041)	(8,658)	0
Repurchases of common stock	(14,208)	(28,818)	(42,247)
Net proceeds from issuance of stock	30,615	19,512	35,782
Tax benefits associated with share-based compensation expense	6,557	2,305	6,207
Net cash provided by (used in) financing activities	(7,015)	(24,409)	(9,008)
Effect of exchange rate changes on cash	(4,160)	6,916	(5,734)
Increase (decrease) in cash and cash equivalents	110,411	(66,711)	70,035
Cash and cash equivalents at beginning of year	287,479	354,190	284,155
Cash and cash equivalents at end of year	397,890	287,479	354,190
Supplemental disclosure of cash flow information:
Cash paid for income taxes	13,321	7,246	8,543
Cash paid for interest	4,128	4,307	4,107
Supplemental disclosure of non-cash investing and financing activities:
Purchases of property, plant and equipment in accrued liabilities and accounts payable at the end of period	$ 1,488	$ 1,005	$ 1,503

CONSOLIDATED STATEMENT OF CHANG

CONSOLIDATED STATEMENT OF CHANGES IN STOCKHOLDER'S EQUITY - USD ($) $ in Thousands	Total	Common Stock [Member]	Capital in Excess Of Par [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]
Balance, beginning of period at Sep. 30, 2014	$ 372,002	$ 32	$ 437,266	$ 227,942	$ 9,255	$ (302,493)
Share-based compensation expense	16,445		16,445
Repurchases of common stock under share repurchase plans, at cost	(40,026)					(40,026)
Repurchases of common stock - other, at cost	(2,221)					(2,221)
Exercise of stock options	33,176	1	33,175
Issuance of Cabot Microelectronics restricted stock under Deposit Share Plan	23		23
Issuance of Cabot Microelectronics stock under Employee Stock Purchase Plan	2,583		2,583
Tax benefits from share-based compensation plans	6,181		6,181
Net income	56,146			56,146
Foreign currency translation adjustments	(14,126)				(14,126)
Interest rate swaps	(901)				(901)
Minimum pension liability adjustment	(318)				(318)
Balance, end of period at Sep. 30, 2015	428,964	33	495,673	284,088	(6,090)	(344,740)
Share-based compensation expense	13,787		13,787
Repurchases of common stock under share repurchase plans, at cost	(25,980)					(25,980)
Repurchases of common stock - other, at cost	(2,838)					(2,838)
Exercise of stock options	16,624	1	16,623
Issuance of Cabot Microelectronics restricted stock under Deposit Share Plan	52		52
Issuance of Cabot Microelectronics stock under Employee Stock Purchase Plan	2,837		2,837
Tax benefits from share-based compensation plans	1,868		1,868
Net income	59,849			59,849
Dividends paid	(13,161)			(13,161)
Foreign currency translation adjustments	15,996				15,996
Interest rate swaps	84				84
Minimum pension liability adjustment	(434)				(434)
Balance, end of period at Sep. 30, 2016	497,648	34	530,840	330,776	9,556	(373,558)
Share-based compensation expense	13,004		13,004
Repurchases of common stock under share repurchase plans, at cost	(12,035)					(12,035)
Repurchases of common stock - other, at cost	(2,173)					(2,173)
Exercise of stock options	27,666	1	27,665
Issuance of Cabot Microelectronics stock under Employee Stock Purchase Plan	2,986		2,986
Tax benefits from share-based compensation plans	6,443		6,443
Net income	86,952			86,952
Dividends paid	(19,847)			(19,847)
Foreign currency translation adjustments	(6,746)				(6,746)
Interest rate swaps	863				863
Minimum pension liability adjustment	276				276
Balance, end of period at Sep. 30, 2017	$ 595,037	$ 35	$ 580,938	$ 397,881	$ 3,949	$ (387,766)

BACKGROUND AND BASIS OF PRESENT

BACKGROUND AND BASIS OF PRESENTATION	12 Months Ended
	Sep. 30, 2017
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 polishes surfaces at an atomic level, thereby helping to enable IC device manufacturers 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. We develop, manufacture and sell CMP polishing pads, which are used in conjunction with slurries in the CMP process. We also develop and provide products for demanding surface modification applications in other industries through our Engineered Surface Finishes (ESF) business. The audited consolidated financial statements have been prepared by us 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). We operate predominantly in one reportable segment - the development, manufacture, and sale of CMP consumables.

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	12 Months Ended
	Sep. 30, 2017
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES PRINCIPLES OF CONSOLIDATION The consolidated financial statements include the accounts of Cabot Microelectronics and its subsidiaries. All intercompany transactions and balances between the companies have been eliminated in the consolidated financial statements as of September 30, 2017. 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 challenging and subjective judgments include, but are not limited to, those estimates related to bad debt expense, inventory valuation, valuation and classification of auction rate securities, impairment of long-lived assets and investments, business combinations, goodwill, other intangible assets, interest rate swaps, net investment hedge, 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. CASH, CASH EQUIVALENTS AND SHORT-TERM INVESTMENTS We consider investments in all highly liquid financial instruments with original maturities of three months or less to be cash equivalents. Short-term investments include securities generally having maturities of 90 days to one year. We did not own any securities that were considered short-term as of September 30, 2017 or 2016. See Note 4 for a more detailed discussion of other financial instruments. ACCOUNTS RECEIVABLE AND ALLOWANCE FOR DOUBTFUL ACCOUNTS Trade accounts receivable are recorded at the invoiced amount and do not bear interest. We maintain an allowance for doubtful accounts for estimated losses resulting from the potential inability of our customers to make required payments. Our allowance for doubtful accounts is based on historical collection experience, adjusted for any specific known conditions or circumstances such as customer bankruptcies and increased risk due to economic conditions. Uncollectible account balances are charged against the allowance when we believe that it is probable that the receivable will not be recovered. Amounts charged to bad debt expense are recorded in general and administrative expenses. A portion of our receivables and the related allowance for doubtful accounts is denominated in foreign currencies, so they are subject to foreign exchange fluctuations which are included in the table below under deductions and adjustments. Our allowance for doubtful accounts changed during the fiscal year ended September 30, 2017 as follows: Balance as of September 30, 2016 $ 1,828 Amounts charged to expense 26 Deductions and adjustments (107 ) Balance as of September 30, 2017 $ 1,747 CONCENTRATION OF CREDIT RISK Financial instruments that subject us to concentrations of credit risk consist principally of accounts receivable. We perform ongoing credit evaluations of our customers' financial conditions and generally do not require collateral to secure accounts receivable. Our exposure to credit risk associated with nonpayment is affected principally by conditions or occurrences within the semiconductor industry and global economy. With the exception of one customer bankruptcy in fiscal 2012 and a customer placed into receivership in fiscal 2016, we have not experienced significant losses relating to accounts receivable from individual customers or groups of customers. Customers who represented more than 10% of revenue are as follows: Year Ended September 30, 2017 2016 2015 Samsung Group (Samsung) 16% 15% 15% Taiwan Semiconductor Manufacturing Co. (TSMC) 13% 15% 18% Micron Technology Inc. 10% * * * Not a customer with more than 10% revenue in fiscal 2016 and 2015. TSMC accounted for 12.2% and 12.9% of net accounts receivable at September 30, 2017 and 2016, respectively. Samsung accounted for 11.9% and 8.3% of net accounts receivable at September 30, 2017 and 2016, respectively. Micron accounted for 10.7% and 7.2% of net accounts receivable at September 30, 2017 and 2016, respectively. Due to recent financial challenges experienced by Toshiba, we continue to monitor their financial condition and ability to make the required payments due on our receivables. At September 30, 2017 our accounts receivable balance with Toshiba represented a U.S. dollar equivalent of $2,323, which equates to 3.6% of our total accounts receivable balance of $64,793, net of allowance for doubtful accounts, and of which no amounts are past due. At present, we do not believe it is probable that the receivables from Toshiba are impaired, and accordingly, we have not recorded a related allowance for doubtful accounts. FAIR VALUES OF FINANCIAL INSTRUMENTS The recorded amounts of cash, accounts receivable, and accounts payable approximate their fair values due to their short-term, highly liquid characteristics. See Note 4 for a more detailed discussion of the fair value of financial instruments. INVENTORIES Inventories are stated at the lower of cost, determined on the first-in, first-out (FIFO) basis, or market. Finished goods and work in process inventories include material, labor and manufacturing overhead costs. We regularly review and write down the value of inventory as required for estimated obsolescence or lack of marketability. An inventory reserve is maintained based upon a historical percentage of actual inventories written off and applied against inventory value at the end of the period, adjusted for known conditions and circumstances. PROPERTY, PLANT AND EQUIPMENT Property, plant and equipment are recorded at cost. Depreciation is based on the following estimated useful lives of the assets using the straight-line method: Buildings 15-25 years Machinery and equipment 3-10 years Furniture and fixtures 5-10 years Information systems 3-5 years Expenditures for repairs and maintenance are charged to expense as incurred. Expenditures for major renewals and betterments are capitalized and depreciated over the remaining useful lives. As assets are retired or sold, the related cost and accumulated depreciation are removed from the accounts and any resulting gain or loss is included in the results of operations. We capitalize the costs related to the design and development of software used for internal purposes; however, these costs are not material. IMPAIRMENT OF LONG-LIVED ASSETS Reviews are regularly performed to determine whether facts and circumstances exist that indicate the carrying amount of assets may not be recoverable or the useful life is shorter than originally estimated. Asset recoverability assessment begins by comparing the projected undiscounted cash flows associated with the related asset or group of assets over their remaining lives against their respective carrying amounts. Impairment, if any, is based on the excess of the carrying amount over the fair value of those assets. If assets are determined to be recoverable, but their useful lives are shorter than originally estimated, the net book value of the asset is depreciated over the newly determined remaining useful life. We recorded impairment expense on a certain long-lived asset of $860 in fiscal year 2017, which was subsequently sold for a gain. We did not record any impairment expense on property, plant and equipment in fiscal 2016 and 2015. See Note 6 for more information regarding impairment. WARRANTY RESERVE We maintain a warranty reserve that reflects management's best estimate of the cost to replace product that does not meet our specifications and customers' performance requirements. The warranty reserve is based upon a historical product return rate, adjusted for any specific known conditions or circumstances. Adjustments to the warranty reserve are recorded in cost of goods sold. GOODWILL AND INTANGIBLE ASSETS We amortize intangible assets with finite lives over their estimated useful lives, which range from one to eleven years. Intangible assets with finite lives are reviewed for impairment using a process similar to that used to evaluate other long-lived assets. Goodwill and indefinite-lived intangible assets are not amortized and are tested annually in the fourth fiscal quarter, or more frequently if indicators of potential impairment exist, using a fair-value-based approach. The recoverability of goodwill is measured at the reporting unit level, which is defined as either an operating segment or one level below an operating segment, referred to as a component. A component is a reporting unit when the component constitutes a business for which discrete financial information is available and segment management regularly reviews the operating results of the component. Components may be combined into one reporting unit when they have similar economic characteristics. We have four reporting units, all of which have goodwill as of September 30, 2017. Goodwill impairment testing requires a comparison of the fair value of each reporting unit to the carrying value. If the carrying value exceeds fair value, then the fair value of the assets and liabilities for the reporting unit is used to determine the "implied" fair value of goodwill. The amount of the impairment is the difference between the carrying value and the implied fair value of goodwill. Accounting guidance provides an entity the option to assess the fair value of a reporting unit either using a qualitative analysis ("step zero") or a quantitative analysis ("step one"). In fiscal 2015, 2016 and 2017, we chose to use a step one analysis for goodwill impairment. Similarly, an entity has the option to use a step zero or step one approach to determine the recoverability of indefinite-lived intangible assets. In fiscal 2015, 2016 and 2017, we used a step one analysis to determine the recoverability of indefinite-lived intangible assets. As discussed in more detail in Note 3, we recorded $1,000 in impairment expense on an in-process technology asset during the fourth quarter of fiscal 2016. We determined that goodwill and the other intangible assets were not impaired as of September 30, 2017. FOREIGN CURRENCY TRANSLATION Certain operating activities in Asia and Europe are denominated in local currency, considered to be the functional currency. Assets and liabilities of these operations are translated using exchange rates in effect at the end of the year, and revenue and costs are translated using average exchange rates for the year. The related translation adjustments are reported in comprehensive income in stockholders' equity. FOREIGN EXCHANGE MANAGEMENT We transact business in various foreign currencies, primarily the Japanese yen, New Taiwan dollar and Korean won. Our exposure to foreign currency exchange risks has not been significant because a large portion of our business is denominated in U.S. dollars. However, there was a weakening of the Japanese yen against the U.S. dollar during fiscal years 2015, 2016 and part of 2017, which had some net positive impact on our gross margin percentage and our net income. Periodically, we enter into certain forward foreign exchange contracts in an effort to mitigate the risks associated with currency fluctuations on certain foreign currency balance sheet exposures. These foreign exchange contracts do not qualify for hedge accounting; therefore, the gains and losses resulting from the impact of currency exchange rate movements on our forward foreign exchange contracts are recognized as other income or expense in the accompanying consolidated income statements in the period in which the exchange rates change. See Note 11 for a discussion of derivative financial instruments. INTEREST RATE SWAPS In fiscal 2015, we entered into floating-to-fixed interest rate swap agreements to hedge the variability in LIBOR-based interest payments on a portion of our outstanding variable rate debt. The fair value of our interest rate swaps is estimated using standard valuation models using market-based observable inputs over the contractual term, including one-month LIBOR-based yield curves, among others. We consider the risk of nonperformance, including counterparty credit risk, in the calculation of the fair value. We have designated these swap agreements as cash flow hedges pursuant to ASC 815, "Derivatives and Hedging". As cash flow hedges, unrealized gains are recognized as assets and unrealized losses are recognized as liabilities. Unrealized gains and losses are designated as effective or ineffective based on a comparison of the changes in fair value of the interest rate swaps and changes in fair value of the underlying exposures being hedged. The effective portion is recorded as a component of accumulated other comprehensive income or loss, while the ineffective portion is recorded as a component of interest expense. Changes in the method by which we pay interest from one-month LIBOR to another rate of interest could create ineffectiveness in the swaps, and result in amounts being reclassified from other comprehensive income into net income. Hedge effectiveness is tested quarterly to determine if hedge treatment is appropriate. NET INVESTMENT HEDGE In the fourth quarter of fiscal 2017, we entered into forward foreign exchange contracts in an effort to protect our net investment in a foreign operation against potential adverse changes resulting from foreign currency fluctuation. This transaction is designated as a net The fair value of our forward foreign exchange contracts is estimated using a standard valuation model and market-based observable inputs over the contractual term, including forward rates and/or the Overnight Index Swap (OIS) curve as of the valuation date. Unrealized gains are recognized as assets and unrealized losses are recognized as liabilities. Hedge effectiveness is assessed using the Forward Method, consistent with guidance in ASC 815. Consistent with this guidance, the entire change in fair value of the forward contracts is recorded in the same manner as the related currency translation adjustments, within other comprehensive income, as the hedging instruments are expected to be fully effective unless the amount hedged exceeds the net investment in the foreign operation, or the foreign operation is liquidated. See Note 11 for a discussion of derivative financial instruments. INTERCOMPANY LOAN ACCOUNTING We maintain an intercompany loan agreement with our wholly-owned subsidiary, Nihon Cabot Microelectronics K.K. ("Nihon"), under which we provided funds to Nihon to finance the purchase of certain assets from our former Japanese branch at the time of the establishment of this subsidiary, for the purchase of land adjacent to our facility in Geino, Japan, for the construction of our Asia Pacific technology center, and for the purchase of a 300 millimeter polishing tool and related metrology equipment, all of which are assets of Nihon, as well as for general business purposes. Since settlement of the note is expected in the foreseeable future, and our subsidiary has made timely payments on the loan, the loan is considered a foreign-currency transaction. Therefore, the associated foreign exchange gains and losses are recognized as other income or expense rather than being deferred in the cumulative translation account in other comprehensive income. We also maintain an intercompany loan between two of our wholly-owned foreign subsidiaries, from Cabot Microelectronics Singapore Pte. Ltd. to Hanguk Cabot Microelectronics, LLC in South Korea. This loan provided funds for the construction and operation of our research, development and manufacturing facility in South Korea. This loan is also considered a foreign currency transaction and is accounted for in the same manner as our intercompany loan to Nihon. These intercompany loans are eliminated from our Consolidated Balance Sheet in consolidation. PURCHASE COMMITMENTS We have entered into unconditional purchase obligations, which include noncancelable purchase commitments and take-or-pay arrangements with suppliers. On an ongoing basis, we review our agreements and assess the likelihood of a shortfall in purchases and determine if it is necessary to record a liability. See Note 18 for additional discussion of purchase commitments. To date, we have not recorded such a liability. REVENUE RECOGNITION Revenue from CMP consumables products is recognized when title is transferred to the customer, assuming all revenue recognition criteria are met. Title transfer generally occurs upon shipment to the customer or when inventory held on consignment is consumed by the customer, subject to the terms and conditions of the particular customer arrangement. We have consignment agreements with a number of our customers that require, at a minimum, monthly consumption reports that enable us to record revenue and inventory usage in the appropriate period. Although the majority of our products are sold directly, we market some of our products through distributors in certain areas of the world. We recognize revenue upon shipment and when title is transferred to the distributor. We do not have any arrangements with distributors that include payment terms, rights of return, or rights of exchange outside the ordinary course of business, or any other significant matters that we believe would impact the timing of revenue recognition. Within our Engineered Surface Finishes (ESF) business, sales of equipment are recorded as revenue upon delivery and customer acceptance. Amounts allocated to installation and training are deferred until those services are provided and are not material. Revenues are reported net of any value-added tax or other such tax assessed by a governmental authority on our revenue-producing activities. SHIPPING AND HANDLING Costs related to shipping and handling are included in cost of goods sold. RESEARCH, DEVELOPMENT AND TECHNICAL Research, development and technical costs are expensed as incurred and consist primarily of staffing costs, materials and supplies, depreciation, utilities and other facilities costs. INCOME TAXES Current income taxes are determined based on estimated taxes payable or refundable on tax returns for the current year. Deferred income taxes are determined based on differences between the book and tax bases of recorded assets and liabilities, using enacted tax rates. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. Provisions are made for both U.S. and any foreign deferred income tax liability or benefit. We assess whether our deferred tax assets will ultimately be realized and record an estimated valuation allowance on those deferred tax assets that may not be realized. We recognize the tax benefit of an uncertain tax position only if it is more likely than not that the tax position will be sustained by the taxing authorities, based on the technical merits of the position. In fiscal years 2015, 2016 and 2017 we elected to permanently reinvest the earnings of all of our foreign subsidiaries rather than repatriate the earnings to the U.S. See Note 17 for additional information on income taxes. SHARE-BASED COMPENSATION We record share-based compensation expense for all share-based awards, including stock option grants, restricted stock and restricted stock unit awards and employee stock purchase plan purchases. We calculate share-based compensation expense using the straight-line approach based on awards expected to vest, which requires the use of an estimated forfeiture rate. Our estimated forfeiture rate is primarily based on historical experience, but may be revised in future periods if actual forfeitures differ from the estimate. We use the Black-Scholes option-pricing model to estimate the grant date fair value of our stock options and employee stock purchase plan purchases. This model requires the input of highly subjective assumptions, including the price volatility of the underlying stock, the expected term of our stock options, expected dividend yield, and the risk-free interest rate. We estimate the expected volatility of our stock options based on a combination of our stock's historical volatility and the implied volatilities from actively-traded options on our stock. We calculate the expected term of our stock options using historical stock option exercise data, and we add a slight premium to this expected term for employees who meet the definition of retirement eligible pursuant to their grants during the contractual term of the grant. The expected dividend yield represents our annualized dividend in dollars divided by the stock price on the date of grant. The risk-free rate is derived from the U.S. Treasury yield curve in effect at the time of grant. The fair value of our restricted stock and restricted stock unit awards represents the closing price of our common stock on the date of award. For additional information regarding our share-based compensation plans, refer to Note 13. EARNINGS PER SHARE Basic earnings per share (EPS) is calculated by dividing net income available to common stockholders by the weighted-average number of common shares outstanding during the period, excluding the effects of unvested restricted stock awards with a right to receive non-forfeitable dividends, which are considered participating securities as prescribed by the two class method under ASC Topic 260, Earnings Per Share (ASC 260). Diluted EPS is calculated in a similar manner, but the weighted-average number of common shares outstanding during the period is increased to include the weighted-average dilutive effect of "in-the-money" stock options and unvested restricted stock shares using the treasury stock method. COMPREHENSIVE INCOME Comprehensive income primarily differs from net income due to foreign currency translation adjustments. EFFECTS OF RECENT ACCOUNTING PRONOUNCEMENTS In May 2014, the FASB issued ASU No. 2014-09, "Revenue from Contracts with Customers" (Topic 606), an updated standard on revenue recognition . In July 2015, the FASB issued ASU No, 2015-11, "Simplifying the Measurement of Inventory" (Topic 330). The provisions of ASU 2015-11 require an entity to measure inventory at the lower of cost and net realizable value. Net realizable value is the estimated selling price in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. ASU 2015-11 will be effective for us beginning October 1, 2017, but early adoption is permitted. We do not believe the adoption of this standard will have a material effect on our financial statements. In February 2016, the FASB issued ASU No. 2016-02, "Leases" (Topic 842). The provisions of ASU 2016-02 require a dual approach for lessee accounting under which a lessee would recognize a right-of-use asset and a corresponding lease liability. Leases will be classified as either finance or operating leases. For finance leases, a lessee will recognize interest expense and amortization of the right-of-use asset, and for operating leases, the lessee will recognize a straight-line total lease expense. The guidance also requires qualitative and specific quantitative disclosures to supplement the amounts recorded in the financial statements, to afford better understanding of an entity's leasing activities, including any significant judgments and estimates. ASU 2016-02 will be effective for us beginning October 1, 2019, but early adoption is permitted. We are currently evaluating the impact of implementation of this standard on our financial statements. In March 2016, the FASB issued ASU No. 2016-05, "Effect of Derivative Contract Novations on Existing Hedge Accounting Relationships" (Topic 815). The provisions of ASU 2016-05 provide clarification that a change in a counterparty of a derivative instrument that has been designated as a hedging instrument does not require dedesignation of that hedging relationship, provided that all other hedge accounting criteria is met. ASU 2016-05 will be effective for us beginning October 1, 2018, but early adoption is permitted. We do not believe the adoption of this standard will have a material effect on our financial statements. In March 2016, the FASB issued ASU No. 2016-07, "Simplifying the Transition to the Equity Method of Accounting" (Topic 323). The provisions of ASU 2016-07 require equity method investors to add the cost of acquiring additional interest in the investee to the current basis of the investor's previously held interest and adopt the equity method prospectively as of the date the investment qualifies for the equity method of accounting. ASU 2016-07 will be effective for us beginning October 1, 2018, but early adoption is permitted. We do not believe the adoption of this standard will have a material effect on our financial statements as we currently have no equity method investments. In March 2016, the FASB issued ASU No. 2016-09, "Improvements to Employee Share Based Payment Accounting" (Topic 718). The provisions of this standard involve several aspects of the accounting for share-based payments transactions, including income tax consequences, classification of awards as either equity or liabilities, and classification on the statement of cash flows. ASU 2016-09 will be effective for us beginning October 1, 2017, but early adoption is permitted. We currently expect that the adoption of this standard will introduce additional variability in our effective tax rate; however, the impact will not be known until the related share-based award activity occurs. The adoption will also impact the classification of excess tax benefits on the Consolidated Statements of Cash Flows. In June 2016, the FASB issued ASU No. 2016-13, "Measurement of Credit Losses on Financial Instruments" (Topic 326). The provisions of this standard require financial assets measured at amortized cost to be presented at the net amount expected to be collected. An allowance account would be established to present the net carrying value at the amount expected to be collected. ASU 2016-13 also provides that credit losses relating to available-for-sale debt securities should be recorded through an allowance for credit losses. ASU 2016-13 will be effective for us beginning October 1, 2020, but early adoption is permitted as of October 1, 2019. We are currently evaluating the impact of implementation of this standard on our financial statements. In August 2016, the FASB issued ASU No. 2016-15 "Classification of Certain Cash Receipts and Cash Payments" (Topic 230). The provisions of this standard provide guidance on the classification within the statement of cash flows of certain types of cash receipts and cash payments in an effort to eliminate diversity in practice. ASU 2016-15 will be effective for us beginning October 1, 2018, but early adoption is permitted. We do not believe the adoption of this standard will have a material effect on our financial statements as we currently do not have any of the cash receipts or payments discussed in this standard. In October 2016, the FASB issued ASU No. 2016-16 "Intra-Entity Transfers of Assets Other Than Inventory" (Topic 740). The provisions of this standard provide guidance on recognition of taxes related to intra-entity transfer of assets other than inventory when the transfer occurs. ASU 2016-16 will be effective for us beginning October 1, 2018, but early adoption is permitted. We are currently evaluating the impact of implementation of this standard on our financial statements. In October 2016, the FASB issued ASU No. 2016-17 "Interest Held through Related Parties That Are under Common Control" (Topic 810). The provisions of this standard provide further guidance related to ASU 2015-02, and also provide guidance on consolidation in relation to VIEs and related parties. ASU 2016-17 will be effective for us beginning October 1, 2017, but early adoption is permitted. We do not believe the adoption of this standard will have a material effect on our financial statements as we currently have no interest in any entities that may be considered VIE. In January 2017, the FASB issued ASU No. 2017-01 "Clarifying the Definition of a Business" (Topic 805). The provisions of this standard provide guidance to determine whether the acquisition or sale of a set of assets or activities constitutes a business. The standard requires that an integrated set of assets and activities include an input and a substantive process that together contribute to the ability to create output. ASU 2017-01 will be effective for us beginning October 1, 2017, and early adoption is permitted under specified conditions. We do not believe the adoption of this standard will have a material effect on our financial statements. In January 2017, the FASB issued ASU No. 2017-04 "Simplifying the Test for Goodwill Impairment" (Topic 350). The provisions of this standard eliminate Step 2 from the goodwill impairment test, which required an entity to determine the fair value of its assets and liabilities at the impairment testing date of its goodwill and compare it to its carrying amount to determine a possible impairment loss. Goodwill impairment testing will now be done by comparing the fair value of a reporting unit and its carrying amount. ASU 2017-04 will be effective for us beginning October 1, 2020, but early adoption is permitted as of October 1, 2017. We are currently evaluating the impact of implementation of this standard on our financial statements. In March 2017, the FASB issued ASU No. 2017-07 "Improving the Presentation of Net Period Pension Cost and Net Period Postretirement Benefit Cost" (Topic 715). The provisions of ASU 2017-07 provided specific guidance on the presentation of the components of net benefit cost. ASU 2017-07 will be effective for us beginning October 1, 2018. We are currently evaluating the impact of implementation of this standard on our financial statements. In May 2017, the FASB issued ASU No. 2017-09 "Scope of Modification Accounting" (Topic 718). The provisions of ASU 2017-09 provide specific guidance about which changes to the term or conditions of a share-based payment require an entity to apply modification accounting. ASU 2017-09 will be effective for us beginning October 1, 2018. We are currently evaluating the impact of implementation of this standard on our financial statements. In August 2017, the FASB issued ASU No. 2017-12 "Derivatives and Hedging" (Topic 815). The provisions of this standard amend the hedge accounting model in ASC 815 to expand an entity's ability to hedge nonfinancial and financial risk components, reduce complexity in fair value hedges of interest rate risk, eliminate the requirement to separately measure and report hedge ineffectiveness, and generally require the entire change in the fair value of a hedging instrument to be presented in the same income statement line as the hedged item. The guidance also eases certain documentation and assessment requirements and modifies the accounting for components excluded from the assessment of hedge effectiveness. ASU 2017-09 will be effective for us beginning October 1, 2019, but early adoption is permitted. We are currently evaluating the impact of implementation of this standard on our financial statements.

BUSINESS COMBINATION

BUSINESS COMBINATION	12 Months Ended
	Sep. 30, 2017
BUSINESS COMBINATION [Abstract]
BUSINESS COMBINATION	3. BUSINESS COMBINATION On October 22, 2015, the Company completed the acquisition of 100% of the outstanding stock of NexPlanar Corporation (NexPlanar), which was a privately held, U.S. based company that specialized in the development, manufacture and sale of advanced CMP pad solutions for the semiconductor industry. We acquired NexPlanar to expand our polishing pad portfolio by adding a complementary pad technology for which we believe we can leverage our global infrastructure to better serve customers on a global basis, including offering performance-advantaged slurry and pad consumable sets. We paid a total of $ 126,976 , less cash acquired of $15,261 142,167 In addition, we paid $154 The following table summarizes the fair values of assets acquired and liabilities assumed as of the date of acquisition: Total purchase consideration $ 142,237 Cash $ 15,261 Accounts receivable 3,052 Inventories 2,768 Prepaid expenses and other current assets 1,712 Property, plant and equipment 6,901 Intangible assets 55,000 Deferred tax assets 20,509 Other long-term assets 1,458 Accounts payable (1,057 ) Accrued expenses and other current liabilities (1,472 ) Deferred tax liabilities (20,313 ) Total identifiable net assets 83,819 Goodwill 58,418 $ 142,237 The acquisition was accounted for using the acquisition method of accounting. Tangible and identifiable intangible assets acquired and liabilities assumed are recorded at fair value as of the acquisition date. We finalized the purchase price allocation during the fourth quarter of fiscal 2016. We believe that the information we used provides a reasonable basis for estimating the fair values of assets acquired and liabilities assumed. The following table sets forth the components of identifiable intangible assets acquired and their estimated useful lives as of the date of acquisition: Fair Useful Value Life Trade name $ 8,000 7 years Customer relationships 8,000 11 years Developed technology - product family A 32,000 7 years Developed technology - product family B 2,000 9 years In-process technology 5,000 Total intangible assets $ 55,000 The trade name represents the estimated fair value of the brand and name recognition associated with the marketing of NexPlanar's product offerings. Customer relationships represent the estimated fair value of the underlying relationships and agreements with NexPlanar customers. Developed technology represents the estimated fair value of NexPlanar's technology, processes and knowledge regarding its product offerings. In-process technology represents the fair value assigned to technology projects under development as of the acquisition date. The in-process technology assets are capitalized and accounted for as indefinite-lived intangible assets and will be subject to impairment testing until completion or abandonment of the projects. Upon successful completion of each project, we will make a determination of the appropriate useful life and the related amortization will be recorded as an expense over the estimated useful life based on the future expected cash flow stream. In the fourth quarter of fiscal 2016, we recorded impairment expense of $1,000 representing the entire fair value of one of the in-process technology assets as management determined that expected future cash flows were insufficient to support the value of the asset. The intangible assets subject to amortization have a weighted average useful life of 7.7 years and are being amortized on a straight-line basis. The following supplemental pro forma information summarizes the combined results of operations for Cabot Microelectronics and NexPlanar as if the acquisition had occurred on October 1, 2014. Year Ended September 30, 2016 2015 Revenues $ 431,856 $ 437,326 Net income 60,620 46,928 Earnings per share - basic 2.50 1.93 Earnings per share - diluted $ 2.46 $ 1.89 The historical financial information has been adjusted to give effect to the pro forma adjustments, which consist of amortization expense associated with intangible assets, and the elimination of interest expense on NexPlanar debt repaid prior to the acquisition. The pro forma amounts for the years ended September 30, 2016 and 2015 exclude the impact of compensation expense related to unvested NexPlanar stock options settled in cash, and the step-up of inventory as these items are assumed to have occurred during the quarter ended December 31, 2014 had the acquisition been completed on October 1, 2014. The pro forma consolidated results are not necessarily indicative of what the consolidated results actually would have been had the acquisition been completed on October 1, 2014. The pro forma consolidated results do not purport to project future results of combined operations, nor do they reflect the expected realization of any revenue or cost synergies associated with the acquisition.

FAIR VALUE OF FINANCIAL INSTRUM

FAIR VALUE OF FINANCIAL INSTRUMENTS	12 Months Ended
	Sep. 30, 2017
FAIR VALUE OF FINANCIAL INSTRUMENTS [Abstract]
FAIR VALUE OF FINANCIAL INSTRUMENTS	4. FAIR VALUE OF FINANCIAL INSTRUMENTS Fair value is defined as the price that would be received from the sale of an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The FASB established a three-level hierarchy for disclosure based on the extent and level of judgment used to estimate fair value. Level 1 inputs consist of valuations based on quoted market prices in active markets for identical assets or liabilities. Level 2 inputs consist of valuations based on quoted prices for similar assets or liabilities, quoted prices for identical assets or liabilities in an inactive market, or other observable inputs. Level 3 inputs consist of valuations based on unobservable inputs that are supported by little or no market activity. The following table presents financial instruments, other than long-term debt, that we measured at fair value on a recurring basis at 2017 and 2016 September 30, 2017 Level 1 Level 2 Level 3 Total Fair Value Assets: Cash and cash equivalents $ 397,890 $ - $ - $ 397,890 Other long-term investments 929 - - 929 Derivative financial instruments - 263 - 263 Total assets $ 398,819 $ 263 $ - $ 399,082 Liabilities: Derivative financial instruments - 1,881 - 1,881 Total liabilities $ - $ 1,881 $ - $ 1,881 September 30, 2016 Level 1 Level 2 Level 3 Total Fair Value Assets: Cash and cash equivalents $ 287,479 $ - $ - $ 287,479 Other long-term investments 1,028 - - 1,028 Derivative financial instruments - 28 - 28 Total assets $ 288,507 $ 28 $ - $ 288,535 Liabilities: Derivative financial instruments - 1,469 - 1,469 Total liabilities $ - $ 1,469 $ - $ 1,469 Our cash and cash equivalents consist of various bank accounts used to support our operations and investments in institutional money-market funds that are traded in active markets. We invest only in AAA-rated, prime institutional money market funds, comprised of high quality, short-term fixed income securities. Our other long-term investments represent the fair value of investments under the Cabot Microelectronics Supplemental Employee Retirement Plan (SERP), which is a nonqualified supplemental savings plan. The fair value of the investments is determined through quoted market prices within actively traded markets. Although the investments are allocated to individual participants and investment decisions are made solely by those participants, the SERP is a nonqualified plan. Consequently, the Company owns the assets and the related offsetting liability for disbursement until such time as a participant makes a qualifying withdrawal. The long-term asset was adjusted to $929 in the fourth quarter of fiscal 2017 to reflect its fair value as of September 30, 2017. Our derivative financial instruments include forward foreign exchange contracts and interest rate swaps. In fiscal 2015, we entered into floating-to-fixed interest rate swap agreements to hedge the variability in LIBOR-based interest payments on a portion of our outstanding variable rate debt. In the fourth quarter of fiscal 2017, we entered into forward foreign exchange contracts in an effort to protect our net investment in a foreign operation against potential adverse changes resulting from foreign currency fluctuation. The fair value of our derivative instruments is estimated using standard valuation models and market-based observable inputs over the contractual term, including one-month LIBOR-based yield curves for interest rate swaps, and forward rates and/or the Overnight Index Swap (OIS) curve for forward foreign exchange contracts, among others. We consider the risk of nonperformance, including counterparty credit risk, in the calculation of the fair value of derivative financial instruments. See Note 11 for more information on our use of derivative financial instruments.

INVENTORIES

INVENTORIES	12 Months Ended
	Sep. 30, 2017
INVENTORIES [Abstract]
INVENTORIES	5. INVENTORIES Inventories consisted of the following: September 30, 2017 2016 Raw materials $ 36,415 $ 45,109 Work in process 7,365 4,668 Finished goods 28,093 22,346 Total $ 71,873 $ 72,123

PROPERTY, PLANT AND EQUIPMENT

PROPERTY, PLANT AND EQUIPMENT	12 Months Ended
	Sep. 30, 2017
PROPERTY, PLANT AND EQUIPMENT [Abstract]
PROPERTY, PLANT AND EQUIPMENT	6. PROPERTY, PLANT AND EQUIPMENT Property, plant and equipment consisted of the following: September 30, 2017 2016 Land $ 17,823 $ 18,636 Buildings 104,057 100,084 Machinery and equipment 187,649 198,870 Furniture and fixtures 6,770 6,642 Information systems 32,748 29,573 Construction in progress 10,439 6,358 Total property, plant and equipment 359,486 360,163 Less: accumulated depreciation (253,125 ) (253,667 ) Net property, plant and equipment $ 106,361 $ 106,496 Depreciation expense was $17,195, $16,915 and $16,060 for the years ended September 30, 2017, 2016 and 2015, respectively. In fiscal 2017, we recorded $860 in impairment expense related to a surplus research and development asset, and we recorded a $1,820 gain on the sale of surplus research and development equipment. We did not record any impairment expense on property, plant and equipment in fiscal 2016 and 2015.

GOODWILL AND OTHER INTANGIBLE A

GOODWILL AND OTHER INTANGIBLE ASSETS	12 Months Ended
	Sep. 30, 2017
GOODWILL AND OTHER INTANGIBLE ASSETS [Abstract]
GOODWILL AND OTHER INTANGIBLE ASSETS	7. GOODWILL AND OTHER INTANGIBLE ASSETS Goodwill was $101,932 and $100,639 as of September 30, 2017 and 2016, respectively. The increase in goodwill was due to $1,147 in foreign exchange fluctuations of the New Taiwan dollar and an adjustment of $146 to a deferred tax liability. The components of other intangible assets are as follows: September 30, 2017 September 30, 2016 Gross Carrying Amount Accumulated Amortization Gross Carrying Amount Accumulated Amortization Other intangible assets subject to amortization: Product technology $ 42,287 $ 17,604 $ 42,194 $ 12,718 Acquired patents and licenses 8,270 8,241 8,270 8,155 Trade secrets and know-how 2,550 2,550 2,550 2,550 Customer relationships, distribution rights and other 28,229 15,421 27,900 12,205 Total other intangible assets subject to amortization 81,336 43,816 80,914 35,628 Other intangible assets not subject to amortization: In-process technology 4,000 4,000 Other indefinite-lived intangibles* 1,190 1,190 Total other intangible assets not subject to amortization 5,190 5,190 Total other intangible assets $ 86,526 $ 43,816 $ 86,104 $ 35,628 * Other indefinite-lived intangibles not subject to amortization primarily consist of trade names. Amortization expense was $7,795, $8,176 and $2,346 for fiscal 2017, 2016 and 2015, respectively. Estimated future amortization expense of intangible assets as of September 30, 2017 for the five succeeding fiscal years is as follows: Fiscal Year Estimated Amortization Expense 2018 $ 7,118 2019 6,675 2020 6,670 2021 6,664 2022 6,664 Goodwill and indefinite-lived intangible assets are tested for impairment annually in the fourth quarter of our fiscal year or more frequently if indicators of potential impairment exist, using a fair-value-based approach. The recoverability of goodwill is measured at the reporting unit level, which is defined as either an operating segment or one level below an operating segment. An entity has the option to assess the fair value of a reporting unit either using a qualitative analysis ("step zero") or a quantitative analysis ("step one"). Similarly, an entity has the option to use a step zero or a step one approach to determine the recoverability of indefinite-lived intangible assets. In fiscal 2016 and 2017, we chose to use a step one analysis for both goodwill impairment and for indefinite-lived intangible asset impairment. We completed our annual impairment test during our fourth quarter of fiscal 2017 and concluded that no impairment existed. During the fourth quarter of fiscal 2016, as discussed in Note 3, we recorded $1,000 of impairment expense on one of the in-process technology assets acquired in the NexPlanar acquisition based on management's revised expected future cash flows for this asset. The impairment charge was included in research, development and technical expenses on our Consolidated Statements of Income. We concluded that no other impairment of goodwill or intangible assets was necessary. No impairment existed as a result of our impairment test during the fourth quarter of fiscal 2015. There have been no cumulative impairment charges recorded on the goodwill for any of our reporting units.

OTHER LONG-TERM ASSETS

OTHER LONG-TERM ASSETS	12 Months Ended
	Sep. 30, 2017
OTHER LONG-TERM ASSETS [Abstract]
OTHER LONG-TERM ASSETS	8. OTHER LONG-TERM ASSETS Other long-term assets consisted of the following: September 30, 2017 2016 Auction rate securities (ARS) $ 5,319 $ 5,494 Long-term contract asset 2,115 3,055 Other long-term assets 2,154 2,465 Other long-term investments 929 1,028 Total $ 10,517 $ 12,042 We classify our ARS investments as held-to-maturity and have recorded them at cost. Our ARS investments at September 30, 2017 consisted of two tax exempt municipal debt securities with a total par value of $5,319, both of which have maturities greater than ten years. The ARS market began to experience illiquidity in early 2008, and this illiquidity continues. Despite this lack of liquidity, there have been no defaults in payment of the underlying securities and interest income on these holdings continues to be received on scheduled interest payment dates. Our ARS, when purchased, were issued by A-rated municipalities. Although the credit ratings of both municipalities have been downgraded since our original investment, one of the ARS is credit enhanced with bond insurance, and the other has become an obligation of the bond insurer. Both ARS currently carry a credit rating of AA- by Standard & Poor's. The fair value of our ARS, determined using level 2 fair value inputs, was $4,884 as of September 30, 2017. We have classified our ARS as held-to-maturity based on our intention and ability to hold the securities until maturity. We believe the gross unrecognized loss of $435 is due to the illiquidity in the ARS market, rather than to credit loss. Although we believe these securities will ultimately be collected in full, we believe that it is not likely that we will be able to monetize the securities in our next business cycle (which for us is generally one year). We will continue to monitor our ARS for impairment indicators, which may require us to record an impairment charge that is deemed other-than-temporary. In the third quarter of fiscal 2015, we amended a supply contract with an existing supplier. The amended agreement includes a fee of $4,500, which provides us the option to purchase certain raw materials beyond calendar 2016. This fee was recorded as a long-term asset at its present value and is being amortized into cost of goods sold on a straight-line basis through December 31, 2019, the expiration date of the agreement. See Note 18 for more information regarding this contract. Other long-term assets are comprised of the long-term portion of prepaid unamortized debt costs, related to our Revolving Credit Facility, as well as miscellaneous deposits and prepayments on contracts extending beyond the next 12 months. As discussed in Note 10, we reclassified $435 of prepaid debt costs related to our Term Loan out of other long-term assets as of September 30, 2016, in accordance with the adoption of a new accounting pronouncement. As discussed in Note 4, we recorded a long-term asset and a corresponding long-term liability of $929 representing the fair value of our SERP investments as of September 30, 2017.

ACCRUED EXPENSES, INCOME TAXES

ACCRUED EXPENSES, INCOME TAXES PAYABLE AND OTHER CURRENT LIABILITIES	12 Months Ended
	Sep. 30, 2017
ACCRUED EXPENSES, INCOME TAXES PAYABLE AND OTHER CURRENT LIABILITIES [Abstract]
ACCRUED EXPENSES, INCOME TAXES PAYABLE AND OTHER CURRENT LIABILITIES	9. ACCRUED EXPENSES, INCOME TAXES PAYABLE AND OTHER CURRENT LIABILITIES Accrued expenses, income taxes payable and other current liabilities consisted of the following: September 30, 2017 2016 Accrued compensation $ 35,332 $ 17,856 Dividends payable 5,314 4,502 Goods and services received, not yet invoiced 2,172 2,648 Deferred revenue and customer advances 1,559 782 Warranty accrual 247 243 Income taxes payable 9,717 7,878 Taxes, other than income taxes 1,688 775 Current portion of long-term contract liability 1,500 1,500 Other 5,122 5,211 Total $ 62,651 $ 41,395

DEBT

DEBT	12 Months Ended
	Sep. 30, 2017
DEBT [Abstract]
DEBT	10. DEBT On February 13, 2012, we entered into a credit agreement (the "Credit Agreement") among the Company, as Borrower, Bank of America, N.A., as administrative agent, swing line lender and an L/C issuer, Bank of America Merrill Lynch and J.P. Morgan Securities LLC, as joint lead arrangers and joint book managers, JPMorgan Chase Bank, N.A., as syndication agent, and Wells Fargo Bank, N.A. as documentation agent. The Credit Agreement provided us with a $175,000 term loan (the "Term Loan"), which we drew on February 27, 2012 to fund approximately half of the special cash dividend we paid to our stockholders on March 1, 2012, and a $100,000 revolving credit facility (the "Revolving Credit Facility"), which has never been drawn, with sub-limits for multicurrency borrowings, letters of credit and swing-line loans. The Term Loan and the Revolving Credit Facility are referred to as the "Credit Facilities." On June 27, 2014, we entered into an amendment (the "Amendment") to the Credit Agreement, which (i) increased term loan commitments by $17,500, from $157,500 to $175,000, the same level as the original amount under the Credit Agreement at its inception in 2012; (ii) increased the uncommitted accordion feature on the Revolving Credit Facility from $75,000 to $100,000; (iii) extended the expiration date of the Credit Facilities from February 13, 2017 to June 27, 2019; (iv) relaxed the consolidated leverage ratio financial covenant; and (v) revised certain pricing terms and other terms within the Credit Agreement. On June 27, 2014, we drew the $17,500 of increased term loan commitments, bringing the total outstanding commitments under the Term Loan to $175,000. Borrowings under the amended Credit Facilities (other than in respect of swing-line loans) bear interest at a rate per annum equal to the "Applicable Rate" (as defined below) plus, at our option, either (1) a LIBOR rate determined by reference to the cost of funds for deposits in the relevant currency for the interest period relevant to such borrowing or (2) the "Base Rate", which is the highest of (x) the prime rate of Bank of America, N.A., (y) the federal funds rate plus 1/2 of 1.00% and (z) the one-month LIBOR rate plus 1.00%. The current Applicable Rate for borrowings under the Credit Facilities is 1.50%, as amended, with respect to LIBOR borrowings and 0.25% with respect to Base Rate borrowings, with such Applicable Rate subject to adjustment based on our consolidated leverage ratio. Swing-line loans bear interest at the Base Rate plus the Applicable Rate for Base Rate loans under the Revolving Credit Facility. In addition to paying interest on outstanding principal under the Credit Agreement, we pay a commitment fee to the lenders under the Revolving Credit Facility in respect of the unutilized commitments thereunder. As amended, the fee ranges from 0.20% to 0.30%, based on our consolidated leverage ratio. Interest expense and commitment fees are paid according to the relevant interest period and no less frequently than at the end of each calendar quarter. We also pay letter of credit fees as necessary. The Term Loan has periodic scheduled repayments; however, we may voluntarily prepay the Credit Facilities without premium or penalty, subject to customary "breakage" fees and reemployment costs in the case of LIBOR borrowings. All obligations under the Credit Agreement are guaranteed by certain of our existing and future direct and indirect domestic subsidiaries. The obligations under the Credit Agreement and guarantees of those obligations are secured, subject to certain exceptions, by first priority liens and security interests in the assets of the Company and certain of its domestic subsidiaries. The Credit Agreement contains covenants that restrict the ability of the Company and its subsidiaries to take certain actions, including, among other things and subject to certain significant exceptions: creating liens, incurring indebtedness, making investments, engaging in mergers, selling property, paying dividends or amending organizational documents. The Credit Agreement requires us to comply with certain financial ratio maintenance covenants. These include a maximum consolidated leverage ratio of 2.75 to 1.00 and a minimum consolidated fixed charge coverage ratio of 1.25 to 1.00 for the period January 1, 2016 through the expiration of the Credit Agreement. As of September 30, 2017, our consolidated leverage ratio was 0.91 to 1.00 and our consolidated fixed charge coverage ratio was 3.41 to 1.00. The Credit Agreement also contains customary affirmative covenants and events of default. We believe we are in compliance with these covenants. At September 30, 2017, the fair value of the Term Loan, using level 2 inputs, approximates its carrying value of $144,376 as the loan bears a floating market rate of interest. As of September 30, 2017, $10,938 of the debt outstanding is classified as short-term. In the first quarter of fiscal 2017, we adopted the provisions of Accounting Standards Update No. 2015-03, "Simplifying the Presentation of Debt Issuance Costs" (ASU 2015-03) and ASU 2015-15, "Presentation and Subsequent Measurement of Debt Issuance Costs Associated with Line-of-Credit Arrangements". The provisions of ASU 2015-03 require an entity to present the debt issuance costs related to a recognized debt liability in the balance sheet as a direct deduction to the carrying amount of that debt liability. ASU 2015-03 requires adoption on a retrospective basis, wherein the balance sheet of each individual period should be adjusted to reflect the period-specific effects of the guidance. ASU 2015-15 provides guidance on the treatment of debt issuance costs related to line-of-credit arrangements based on comments provided by the SEC staff. The SEC staff stated that it would not object to an entity deferring and presenting debt issuance costs as an asset and subsequently amortizing the deferred debt issuance cost ratably over the term of the line-of-credit arrangement, regardless of whether there are any outstanding borrowings on the line-of-credit arrangement. In accordance with this guidance, we have separated our debt issuance costs between those attributable to our Term Loan and those attributable to our Revolving Credit Facility. The debt issuance costs attributable to our Term Loan are presented as a reduction of the long-term debt balance on our Consolidated Balance Sheet, while the debt issuance costs attributable to our Revolving Credit Facility remain in prepaid expenses and other current assets, and other long-term assets. As of September 30, 2017, $441 of debt issuance costs related to our Term Loan are presented as a reduction of long-term debt. Debt issuance costs related to our Revolving Credit Facility are not material. As of September 30, 2016, we reclassified $261 and $435 of debt issuance costs related to our Term Loan from prepaid expenses and other current assets, and other long-term assets, respectively, and presented them as a reduction of our long-term debt on our Consolidated Balance Sheet. Principal repayments of the Term Loan are generally made on the last calendar day of each quarter if that day is considered to be a business day. As of September 30, 2017, scheduled principal repayments of the Term Loan were as follows: Fiscal Year Principal Repayments 2018 $ 10,938 2019 133,438 Total $ 144,376

DERIVATIVE FINANCIAL INSTRUMENT

DERIVATIVE FINANCIAL INSTRUMENTS	12 Months Ended
	Sep. 30, 2017
DERIVATIVE FINANCIAL INSTRUMENTS [Abstract]
DERIVATIVE FINANCIAL INSTRUMENTS	11. DERIVATIVE FINANCIAL INSTRUMENTS We are exposed to various market risks, including risks associated with interest rates and foreign currency exchange rates. We enter into certain derivative transactions to mitigate the volatility associated with these exposures. We have policies in place that define acceptable instrument types we may enter into and we have established controls to limit our market risk exposure. We do not use derivative financial instruments for trading or speculative purposes. In addition, all derivatives, whether designated in hedging relationships or not, are required to be recorded on the balance sheet at fair value on a gross basis. Cash Flow Hedges – Interest Rate Swap Agreements In fiscal 2015, we entered into floating-to-fixed interest rate swap agreements to hedge the variability in LIBOR-based interest payments on $86,406 of our outstanding variable rate debt. The notional amount of the swaps decreases each quarter by an amount in proportion to our scheduled quarterly principal payment of debt. The notional value of the swaps was $72,188 as of September 30, 2017, and the swaps are scheduled to expire on June 27, 2019. We have designated these swap agreements as cash flow hedges pursuant to ASC 815, "Derivatives and Hedging". As cash flow hedges, unrealized gains are recognized as assets and unrealized losses are recognized as liabilities. Unrealized gains and losses are designated as effective or ineffective based on a comparison of the changes in fair value of the interest rate swaps and changes in fair value of the underlying exposures being hedged. The effective portion is recorded as a component of accumulated other comprehensive income or loss, while the ineffective portion is recorded as a component of interest expense. Changes in the method by which we pay interest from one-month LIBOR to another rate of interest could create ineffectiveness in the swaps, and result in amounts being reclassified from other comprehensive income into net income. Hedge effectiveness is tested quarterly to determine if hedge treatment continues to be appropriate. Foreign Currency Contracts Not Designated as Hedges Periodically we enter into forward foreign exchange contracts in an effort to mitigate the risks associated with currency fluctuations on certain foreign currency balance sheet exposures. These foreign exchange contracts do not qualify for hedge accounting; therefore, the gains and losses resulting from the impact of currency exchange rate movements on our forward foreign exchange contracts are recognized as other income or expense in the accompanying consolidated income statements in the period in which the exchange rates change. As of September 30, 2017 and September 30, 2016, respectively, the notional amounts of the forward contracts we held to purchase U.S. dollars in exchange for foreign currencies were $8,176 and $8,858, respectively, and the notional amounts of forward contracts we held to sell U.S. dollars in exchange for foreign currencies were $ and $15,635, respectively. Net Investment Hedge – Foreign Exchange Contracts In September 2017, we entered into two forward foreign exchange contracts in an effort to protect the net investment of our Korean subsidiary against potential adverse changes resulting from currency fluctuations in the Korean won. We entered into forward contracts to sell Korean won and buy U.S. dollars, and these contracts will settle on September 26, 2022. We have designated these forward contracts as an effective net investment hedge. The total notional amount under the contracts is 100 billion Korean won. As of September 30, 2017, the change in the fair value of the forward contracts in the net investment hedge relationship was $1,442, which was recorded in foreign currency translation adjustments within other comprehensive income. The fair value of our derivative instruments included in the Consolidated Balance Sheet, which was determined using level 2 inputs, was as follows: Asset Derivatives Liability Derivatives September 30, September 30, Consolidated Balance Sheet Location 2017 2016 2017 2016 Derivatives designated as hedging instruments Interest rate swap contracts Other long-term assets $ 117 $ - $ - $ - Accrued expenses, income taxes payable and other current liabilities $ - $ - $ 31 $ 612 Other long-term liabilities $ - $ - $ - $ 655 Foreign exchange contracts designated as net investment hedge Other long-term liabilities - - 1,442 - Derivatives not designated as hedging instruments Foreign exchange contracts Prepaid expenses and other current assets $ 146 $ 28 $ - $ - Accrued expenses, income taxes payable and other current liabilities $ - $ - $ 408 $ 202 The following table summarizes the effect of our derivative instrument on our Consolidated Statements of Income for the fiscal years ended September 30, 2017, 2016 and 2015: Gain (Loss) Recognized in Consolidated Statements of Income Fiscal Year Ended September 30, Derivatives not designated as hedging instruments Consolidated Statements of Income Location 2017 2016 2015 Foreign exchange contracts Other income (expense), net $ (1,462 ) $ 676 $ (1,674 ) The interest rate swap agreements have been deemed to be effective since inception, so there has been no impact on our Consolidated Statement of Income. We recorded a $46 unrealized gain, net of tax, in accumulated comprehensive income during the year ended September 30, 2017 for these interest rate swaps. During the next 12 months, we expect approximately $31 to be reclassified from accumulated other comprehensive income into interest expense related to our interest rate swaps based on projected rates of the LIBOR forward curve as of September 30, 2017. Amounts recognized in Other comprehensive income (loss) for our net investment hedge during the fiscal year ended September 30, were as follows: 2017 Loss on net investment hedge $ 1,442 Tax benefit (522 ) Loss on net investment hedge, net of tax $ 920

ACCUMULATED OTHER COMPREHENSIVE

ACCUMULATED OTHER COMPREHENSIVE INCOME	12 Months Ended
	Sep. 30, 2017
ACCUMULATED OTHER COMPREHENSIVE INCOME [Abstract]
ACCUMULATED OTHER COMPREHENSIVE INCOME	12. ACCUMULATED OTHER COMPREHENSIVE INCOME The table below summarizes the components of accumulated other comprehensive income (loss) (AOCI), net of tax provision/(benefit), for the years ended September 30, 2017, 2016, and 2015. Foreign Currency Translation Cash Flow Hedges Pension and Other Postretirement Liabilities Total Balance at September 30, 2014 $ 10,115 $ - $ (860 ) $ 9,255 Foreign currency translation adjustment, net of tax of $(1,731) (14,126 ) - - (14,126 ) Unrealized gain (loss) on cash flow hedges: Change in fair value, net of tax of $(833) - (1,511 ) - (1,511 ) Reclassification adjustment into earnings, net of tax of $336 - 610 - 610 Change in pension and other postretirement, net of tax of $0 - - (318 ) (318 ) Balance at September 30, 2015 (4,011 ) (901 ) (1,178 ) (6,090 ) Foreign currency translation adjustment, net of tax of $1,854 15,996 - - 15,996 Unrealized gain (loss) on cash flow hedges: Change in fair value, net of tax of $(274) - (499 ) - (499 ) Reclassification adjustment into earnings, net of tax of $321 - 583 - 583 Change in pension and other postretirement, net of tax of $(584) - - (434 ) (434 ) Balance at September 30, 2016 11,985 (817 ) (1,612 ) 9,556 Foreign currency translation adjustment, net of tax of $(2,321) (6,746 ) 0 - (6,746 ) Unrealized gain (loss) on cash flow hedges: Change in fair value, net of tax of $(660) - 1,161 - 1,161 Reclassification adjustment into earnings, net of tax of $170 - (298 ) - (298 ) Change in pension and other postretirement, net of tax of $79 - - 276 276 Balance at September 30, 2017 $ 5,239 $ 46 $ (1,336 ) $ 3,949 The before tax amount reclassified from OCI to net income in fiscal 2017, related to our cash flow hedges, was recorded as interest expense on our Consolidated Statement of Income. Amounts reclassified from OCI to net income, related to pension liabilities, were not material in fiscal years 2017, 2016 and 2015.

SHARE-BASED COMPENSATION PLANS

SHARE-BASED COMPENSATION PLANS	12 Months Ended
	Sep. 30, 2017
SHARE-BASED COMPENSATION PLANS [Abstract]
SHARE-BASED COMPENSATION PLANS	13. SHARE-BASED COMPENSATION PLANS EQUITY INCENTIVE PLAN AND OMNIBUS INCENTIVE PLAN In March 2004, our stockholders approved our Second Amended and Restated Cabot Microelectronics Corporation 2000 Equity Incentive Plan (the "EIP"), as amended and restated September 23, 2008. In March 2012, our stockholders approved the Cabot Microelectronics Corporation 2012 Omnibus Incentive Plan (the "OIP"), which is the successor plan to the EIP, and which was amended as of March 2017. All share-based awards have been made from the OIP as of its approval date, and the EIP is no longer available for any awards. The OIP is administered by the Compensation Committee of the Board of Directors and is intended to provide management with the flexibility to attract, retain and reward our employees, directors, consultants and advisors. The OIP allows for the granting of six Non-qualified stock options issued under the OIP, as they were under the EIP, are generally time-based and provide for a ten-year term, with options generally vesting equally over a four-year period, with first vesting on the first anniversary of the award date. Non-qualified stock options granted to non-employee directors on an annual basis vest 100% on the first anniversary of the award date. Under the OIP, as under the EIP, employees may also be granted ISOs to purchase common stock at not less than the fair value on the date of the grant. Prior to fiscal 2016, no ISOs had been granted under either plan. In the first quarter of fiscal 2016, we substituted certain NexPlanar ISOs with Cabot Microelectronics Corporation ISOs, preserving the intrinsic value, including the original vesting periods, of the original awards. Compensation expense related to our stock option awards was $5,500, $6,767 and $7,173 in fiscal 2017, 2016 and 2015, respectively. For additional information on our accounting for share-based compensation, see Note 2. Under the OIP, as under the EIP, employees and non-employees may be awarded shares of restricted stock or restricted stock units, which generally vest over a four-year period, with first vesting on the anniversary of the grant date. Restricted stock units granted to non-employee directors on an annual basis vest 100% on the first anniversary of the award date. In general, shares of restricted stock and restricted stock units may not be sold, assigned, transferred, pledged, disposed of or otherwise encumbered. Holders of restricted stock, and restricted stock units, if specified in the award agreements, have all the rights of stockholders, including voting and dividend rights, subject to the above restrictions, although the holders of restricted stock units awarded prior to fiscal 2016 do not have such rights. Holders of restricted stock units awarded as of fiscal 2016 have dividend equivalent rights pursuant to the terms of the OIP and respective award agreements. Restricted shares under the OIP, as under the EIP, also may be purchased and placed "on deposit" by executive officers pursuant to the 2001 Deposit Share Program. Shares purchased under this Deposit Share Program receive a 50% match in restricted shares ("Award Shares"). These Award Shares vest at the end of a three-year period, and are subject to forfeiture upon early withdrawal of the deposit shares. Compensation expense related to our restricted stock and restricted stock unit awards and restricted shares matched at 50% pursuant to the Deposit Share Program was $6,730, $6,369 and $8,491 for fiscal 2017, 2016 and 2015, respectively. EMPLOYEE STOCK PURCHASE PLAN In March 2008, our stockholders approved our 2007 Cabot Microelectronics Employee Stock Purchase Plan (the "ESPP"), which amended the ESPP for the primary purpose of increasing the authorized shares of common stock to be purchased under the ESPP from 475,000 designated shares to 975,000 shares. As of September 30, 2017, a total of 435,400 shares are available for purchase under the ESPP. The ESPP allows all full-time, and certain part-time, employees of our Company and its subsidiaries to purchase shares of our common stock through payroll deductions. Employees can elect to have up to 10% of their annual earnings withheld to purchase our stock, subject to a maximum number of shares that a participant may purchase and a maximum dollar expenditure in any six-month offering period, and certain other criteria. The provisions of the ESPP allow shares to be purchased at a price no less than the lower of 85% of the closing price at the beginning or end of each semi-annual stock purchase period. A total of 69,751, 77,437, and 65,735 shares were issued under the ESPP during fiscal 2017, 2016 and 2015, respectively. Compensation expense related to the ESPP was $774, $763 and $686 in fiscal 2017, 2016 and 2015, respectively. DIRECTORS' DEFERRED COMPENSATION PLAN The Directors' Deferred Compensation Plan (DDCP), as amended and restated September 23, 2008, became effective in March 2001 and applies only to our non-employee directors. The cumulative number of shares deferred under the plan was 0 and 16,641 as of September 30, 2017 and 2016, respectively. Compensation expense related to the DDCP was $0, $42, and $95 for each of fiscal 2017, 2016 and 2015, respectively. ACCOUNTING FOR SHARE-BASED COMPENSATION We record share-based compensation expense for all share-based awards, including stock option grants, restricted stock and restricted stock unit awards and employee stock purchase plan purchases. We calculate share-based compensation expense using the straight-line approach based on awards ultimately expected to vest, which requires the use of an estimated forfeiture rate. Our estimated forfeiture rate is primarily based on historical experience, but may be revised in future periods if actual forfeitures differ from the estimate. We use the Black-Scholes option-pricing model to estimate the grant date fair value of our stock options and employee stock purchase plan purchases. This model requires the input of highly subjective assumptions, including the price volatility of the underlying stock, the expected term of our stock options, expected dividend yield and the risk-free interest rate. We estimate the expected volatility of our stock options based on a combination of our stock's historical volatility and the implied volatilities from actively-traded options on our stock. We calculate the expected term of our stock options using historical stock option exercise data, and we add a slight premium to this expected term for employees who meet the definition of retirement-eligible pursuant to their grants during the contractual term of the grant. The expected dividend yield represents our annualized dividend in dollars divided by the stock price on the date of grant. The risk-free interest rate is derived from the U.S. Treasury yield curve in effect at the time of grant. The fair value of our share-based awards, as shown below, was estimated using the Black-Scholes model with the following weighted-average assumptions, excluding the effect of our leveraged recapitalization: Year Ended September 30, 2017 2016 2015 Stock Options Weighted-average grant date fair value $ 16.50 $ 14.47 $ 16.99 Expected term (in years) 6.57 6.56 6.30 Expected volatility 27 % 26 % 33 % Risk-free rate of return 2.1 % 1.9 % 1.9 % Dividend yield 1.2 % 0.3 % - Year Ended September 30, 2017 2016 2015 ESPP Weighted-average grant date fair value $ 12.49 $ 9.57 $ 10.17 Expected term (in years) 0.50 0.50 0.50 Expected volatility 24 % 24 % 24 % Risk-free rate of return 0.6 % 0.4 % 0.1 % Dividend yield 1.3 % 0.5 % - The Black-Scholes model is primarily used in estimating the fair value of short-lived exchange traded options that have no vesting restrictions and are fully transferable. Because employee stock options and ESPP purchases have certain characteristics that are significantly different from traded options, and because changes in the subjective assumptions can materially affect the estimated value, our use of the Black-Scholes model for estimating the fair value of stock options and ESPP purchases may not provide an accurate measure. Although the value of our stock options and ESPP purchases are determined in accordance with applicable accounting standards using an option-pricing model, those values may not be indicative of the fair values observed in a willing buyer/willing seller market transaction. The fair value of our restricted stock and restricted stock unit awards represents the closing price of our common stock on the date of award. Share-based compensation expense related to restricted stock and restricted stock unit awards is recorded net of expected forfeitures. SHARE-BASED COMPENSATION EXPENSE Total share-based compensation expense for the years ended September 30, 2017, 2016 and 2015, is as follows: Year Ended September 30, Income statement classifications: 2017 2016 2015 Cost of goods sold $ 2,229 $ 2,105 $ 1,912 Research, development and technical 1,792 1,633 1,596 Selling and marketing 1,380 1,618 1,075 General and administrative 7,603 8,585 11,862 Tax benefit (4,339 ) (4,341 ) (5,511 ) Total share-based compensation expense, net of tax $ 8,665 $ 9,600 $ 10,934 As discussed in Note 3, in fiscal 2016, we recorded $154 in share-based compensation expense related to certain unvested NexPlanar ISOs settled in cash at the acquisition date. The $154 represents the portion of the fair value of the original awards related to the post-acquisition period had these awards not been settled in cash at the acquisition date. U.S. GAAP prescribes that the portion of fair value of equity awards related to pre-acquisition service periods represents purchase consideration, including equity awards vesting immediately upon a change-in-control, and the portion of fair value related to post-acquisition service periods represents compensation expense. Since the post-acquisition service requirement was eliminated through the cash settlement, the $154 in compensation expense was recorded immediately following the acquisition date. We accelerated the vesting on the substitute ISO awards made to certain individuals based on the terms of their employment agreements and recorded $492 of share-based compensation expense related to this acceleration. The total $646 of acquisition-related compensation is included in the table above as general and administrative expense. Our non-employee directors received annual equity awards in March 2017, pursuant to the OIP. The award agreements provide for immediate vesting of the award at the time of termination of service for any reason other than by reason of Cause, Death, Disability or a Change in Control, as defined in the OIP, if at such time the non-employee director has completed an equivalent of at least two full terms as a director of the Company, as defined in the Company's bylaws. Two of the Company's non-employee directors had completed at least two full terms of service as of the date of the March 2017 award. Consequently, the requisite service period for the award has already been satisfied and we recorded the fair value of $377 of the awards to these two directors to share-based compensation expense in the fiscal quarter ended March 31, 2017 rather than recording that expense over the one-year vesting period stated in the award agreement, as is done for the other non-employee directors who received an annual equity award in March 2017. As discussed in our Annual Report on Form 10-K for the fiscal year ended September 30, 2015, in conjunction with an executive officer transition, all unvested stock options and restricted stock held by our former President and Chief Executive Officer, who remains the Chairman of our Board of Directors in a non-executive capacity, vested in full on December 31, 2015, in accordance with the terms of his employment letter with the Company dated December 12, 2014. We applied the accounting guidance under Accounting Standards Codification (ASC) Topic 718 "Stock Compensation" to determine the additional share-based compensation expense to be recorded as part of the modification of the outstanding equity. The original fair value of his unvested equity totaling $5,033 was recorded ratably between the date of modification and December 31, 2015, rather than recording the expense over the original vesting period. STOCK OPTION ACTIVITY A summary of stock option activity under the EIP and OIP as of September 30, 2017, and changes during fiscal 2017 are presented below: Stock Options Weighted Average Exercise Price Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Outstanding at September 30, 2016 2,052,552 $ 36.97 Granted 369,230 60.99 Exercised (818,640 ) 33.79 Forfeited or canceled (86,081 ) 43.38 Outstanding at September 30, 2017 1,517,061 $ 44.17 7.0 $ 54,251 Exercisable at September 30, 2017 726,897 $ 36.34 5.5 $ 31,687 Expected to vest after September 30, 2017 788,676 $ 51.36 8.3 $ 22,535 The aggregate intrinsic value in the table above represents the total pretax intrinsic value (i.e., for all in-the-money stock options, the difference between our closing stock price of $79.93 per share on the last trading day of fiscal 2017 and the exercise price, multiplied by the number of shares) that would have been received by the option holders had all option holders exercised their options on the last trading day of fiscal 2017. The total intrinsic value of options exercised was $25,213, $12,317 and 31,546 for fiscal 2017, 2016 and 2015, respectively. The total cash received from options exercised was $27,666, $16,623 and $33,177 for fiscal 2017, 2016 and 2015, respectively. The actual tax benefit realized for the tax deductions from options exercised was $8,743, $4,076 and $10,569 for fiscal 2017, 2016 and 2015, respectively. The total fair value of stock options vested during fiscal years 2017, 2016 and 2015 was $5,300, $7,880 and $7,005, respectively. As of September 30, 2017, there was $8,727 of total unrecognized share-based compensation expense related to unvested stock options granted under the EIP and OIP. That cost is expected to be recognized over a weighted-average period of 2.3 years. RESTRICTED STOCK AND RESTRICTED STOCK UNITS A summary of the status of the restricted stock awards and restricted stock unit awards outstanding that were granted under the EIP and OIP as of September 30, 2017, and changes during fiscal 2017, are presented below: Restricted Stock Awards and Units Weighted Average Grant Date Fair Value Nonvested at September 30, 2016 340,460 $ 43.13 Granted 193,761 61.75 Vested (154,526 ) 44.64 Forfeited (33,182 ) 47.76 Nonvested at September 30, 2017 346,513 $ 52.43 The total fair value of restricted stock awards and restricted stock units vested during fiscal years 2017, 2016 and 2015 was $6,898, $10,740 and $7,222, respectively. As of September 30, 2017, there was $13,058 of total unrecognized share-based compensation expense related to unvested restricted stock awards and restricted stock units under the EIP and OIP. That cost is expected to be recognized over a weighted-average period of 2.6 years.

SAVINGS PLAN

SAVINGS PLAN	12 Months Ended
	Sep. 30, 2017
SAVINGS PLAN [Abstract]
SAVINGS PLAN	14. SAVINGS PLAN Effective in May 2000, we adopted the Cabot Microelectronics Corporation 401(k) Plan (the "401(k) Plan"), which is a qualified defined contribution plan, covering all eligible U.S. employees meeting certain minimum age and eligibility requirements, as defined by the 401(k) Plan. Participants may make elective contributions of up to 60% of their eligible compensation. All amounts contributed by participants and earnings on these contributions are fully vested at all times. The 401(k) Plan provides for matching and fixed non-elective contributions by the Company. Under the 401(k) Plan, the Company will match 100% of the first four percent of the participant's eligible compensation and 50% of the next two percent of the participant's eligible compensation that is contributed, subject to limitations required by government regulations. Under the 401(k) Plan, all U.S. employees, even those who do not contribute to the 401(k) Plan, receive a contribution by the Company in an amount equal to four percent of eligible compensation, and thus are participants in the 401(k) Plan. Participants are 100% vested in all Company contributions at all times. The Company's expense for the 401(k) Plan totaled $5,256, $4,624 and $4,111 for the fiscal years ended September 30, 2017, 2016 and 2015, respectively.

OTHER INCOME, NET

OTHER INCOME, NET	12 Months Ended
	Sep. 30, 2017
OTHER INCOME, NET [Abstract]
OTHER INCOME, NET	15. OTHER INCOME, NET Other income, net, consisted of the following: Year Ended September 30, 2017 2016 2015 Interest income $ 2,351 $ 949 $ 365 Other income (expense) (438 ) (296 ) 316 Total other income, net $ 1,913 $ 653 $ 681

STOCKHOLDERS' EQUITY

STOCKHOLDERS' EQUITY	12 Months Ended
	Sep. 30, 2017
STOCKHOLDERS EQUITY [Abstract]
STOCKHOLDERS EQUITY	16. STOCKHOLDERS' EQUITY The following is a summary of our capital stock activity over the past three years: Number of Shares Common Stock Treasury Stock September 30, 2014 31,927,601 8,142,687 Exercise of stock options 1,324,646 Restricted stock under EIP and OIP, net of forfeitures 172,010 Restricted stock under Deposit Share Program, net of forfeitures (811) Common stock under ESPP 65,735 Repurchases of common stock under share repurchase plans 851,245 Repurchases of common stock – other 47,746 September 30, 2015 33,489,181 9,041,678 Exercise of stock options 606,562 Restricted stock under EIP and OIP, net of forfeitures 86,277 Restricted stock under Deposit Share Program, net of forfeitures 1,847 Common stock under ESPP 77,437 Repurchases of common stock under share repurchase plans 636,839 Repurchases of common stock – other 66,125 September 30, 2016 34,261,304 9,744,642 Exercise of stock options 818,640 Restricted stock under EIP and OIP, net of forfeitures 81,047 Restricted stock under Deposit Share Program, net of forfeitures - Common stock under ESPP 69,751 Repurchases of common stock under share repurchase plans 167,809 Repurchases of common stock – other 35,739 September 30, 2017 35,230,742 9,948,190 COMMON STOCK Each share of common stock, including those awarded as restricted stock, but not restricted stock units, entitles the holder to one vote on all matters submitted to a vote of Cabot Microelectronics' stockholders. Common stockholders are entitled to receive ratably the dividends, if any, as may be declared by the Board of Directors. Holders of restricted stock units awarded in fiscal 2017 are entitled to dividend equivalents, which are paid to the holder upon the vesting of the restricted stock units. The number of authorized shares of common stock is 200,000,000 shares. SHARE REPURCHASES In January 2016, our Board of Directors authorized an increase in the amount available under our share repurchase program from $75,000 to $150,000. Under this program, we repurchased 167,809 shares for $12,035 during fiscal 2017, 636,839 shares for $25,980 during fiscal 2016, and 851,245 shares for $40,026 during fiscal 2015. As of September 30, 2017, $121,993 remains available under our share repurchase program. To date, we have funded share repurchases under our share repurchase program from our existing cash balance, and anticipate we will continue to do so. The program, which became effective on the authorization date, may be suspended or terminated at any time, at the Company's discretion. For additional information on share repurchases, see Part II, Item 5, "Market for Registrant's Common Equity, Related Stockholder Matters and Issuer Purchases of Equity Securities" and the section titled "Liquidity and Capital Resources" in Part II, Item 7, "Management's Discussion and Analysis of Financial Condition and Results of Operations" of this Form 10-K. Separate from this share repurchase program, a total of 35,739, 66,125 and 47,746 shares were purchased during fiscal 2017, 2016 and 2015, respectively, pursuant to the terms of our EIP and OIP as shares withheld from award recipients to cover payroll taxes on the vesting of shares of restricted stock granted under the EIP and OIP.

INCOME TAXES

INCOME TAXES	12 Months Ended
	Sep. 30, 2017
INCOME TAXES [Abstract]
INCOME TAXES	17. INCOME TAXES Income before income taxes was as follows: Year Ended September 30, 2017 2016 2015 Domestic $ 33,272 $ 7,130 $ 15,305 Foreign 76,100 63,308 55,892 Total $ 109,372 $ 70,438 $ 71,197 Taxes on income consisted of the following: Year Ended September 30, 2017 2016 2015 U.S. federal and state: Current $ 8,606 $ 609 $ 6,496 Deferred 1,550 (1,465 ) 1,791 Total $ 10,156 $ (856 ) $ 8,287 Foreign: Current $ 13,422 $ 11,737 $ 7,686 Deferred (1,158 ) (292 ) (922 ) Total 12,264 11,445 6,764 Total U.S. and foreign $ 22,420 $ 10,589 $ 15,051 The provision for income taxes at our effective tax rate differed from the statutory rate as follows: Year Ended September 30, 2017 2016 2015 Federal statutory rate 35.0% 35.0% 35.0% U.S. benefits from research and experimentation activities (1.0) (3.5) (2.2) State taxes, net of federal effect 0.4 (0.1) 0.6 Foreign income at other than U.S. rates (14.7) (16.9) (21.4) Executive compensation 0.3 0.0 0.6 Share-based compensation 0.1 0.7 0.1 Adjustment of prior amounts 0.0 0.0 1.4 Taiwan Restructuring 0.0 0.0 7.2 Domestic production deduction 0.0 (1.3) (1.3) Other, net 0.4 1.1 1.1 Provision for income taxes 20.5% 15.0% 21.1% In fiscal years 2015, 2016, and 2017, we elected to permanently reinvest the historical earnings of all of our foreign subsidiaries. We have not provided for deferred taxes on approximately $254,800 of undistributed earnings of such subsidiaries. These earnings could become subject to additional income tax if they are remitted as dividends to the U.S. parent company, loaned to the U.S. parent company, or upon sale of subsidiary stock. Should we decide to repatriate these undistributed foreign earnings, we would need to record a deferred tax liability of approximately $49,000 related to earnings. The increase in the effective tax rate during fiscal 2017 was primarily due to the absence of the retroactive reinstatement of the research and experimentation tax credit recorded in fiscal 2016, and changes in the jurisdictional mix of income. The decrease in the effective tax rate during fiscal 2016 was primarily due to the absence of income taxes incurred in fiscal 2015 related to the restructuring of our operations in Taiwan, the reinstatement of the research and experimentation tax credit in December 2015, and the benefit of $928 related to domestic production deductions. This was partially offset by a change in the mix of earnings among various jurisdictions in which we operate, including a scheduled reduction in the benefit available under our tax holiday in South Korea from 100% to 50% of the statutory tax rate. The results of operations for the fiscal year ended September 30, 2015 included tax adjustments to correct prior period amounts, which we determined to be immaterial to the prior periods to which they related. These adjustments, relating to the tax treatment of intercompany activities between certain of our foreign and U.S. operations, were recorded in fiscal 2015 and reduced full year net income by $868 and diluted earnings per share by approximately $0.04. The Company had operated under a tax holiday in South Korea in conjunction with our investment in research, development and manufacturing facilities there, which expired at the end of fiscal 2017. This arrangement allowed for a tax at 50% of the statutory rate in effect in South Korea for fiscal years 2016 and 2017, following a 0% tax rate in fiscal years 2013, 2014, and 2015. This tax holiday reduced our fiscal 2017, 2016, and 2015 income tax provision by approximately $5,018, $3,771 and $5,446, respectively. This tax holiday increased our fiscal 2017, 2016, and 2015 diluted earnings per share by approximately $0.20, $0.15, and $0.22, respectively. The accounting guidance regarding uncertainty in income taxes prescribes a threshold for the financial statement recognition and measurement of tax positions taken or expected to be taken on a tax return. Under these standards, we may recognize the tax benefit of an uncertain tax position only if it is more likely than not that the tax position will be sustained by the taxing authorities, based on the technical merits of the position. The following table presents the changes in the balance of gross unrecognized tax benefits during the last three fiscal years: Balance September 30, 2014 $ 701 Additions for tax positions relating to the current fiscal year 194 Additions for tax positions relating to prior fiscal years 1,400 Settlements with taxing authorities (522 ) Balance September 30, 2015 1,773 Additions for tax positions relating to the current fiscal year 364 Additions for tax positions relating to prior fiscal years 200 Settlements with taxing authorities (248 ) Balance September 30, 2016 2,089 Additions for tax positions relating to the current fiscal year 381 Additions for tax positions relating to prior fiscal years 44 Lapse of statute of limitations (244 ) Balance September 30, 2017 $ 2,270 The entire balance of unrecognized tax benefits shown above as of September 30, 2017 and 2016, would affect our effective tax rate if recognized. We recognize interest and penalties related to uncertain tax positions as income tax expense in our financial statements. Interest accrued on our Consolidated Balance Sheet was $100 and $65 at September 30, 2017 and 2016, respectively, and any interest and penalties charged to expense in fiscal years 2017, 2016 and 2015 was not material. At September 30, 2017, the tax periods open to examination by the U.S. federal government included fiscal years 2014 through 2017. We believe the tax periods open to examination by U.S. state and local governments include fiscal years 2013 through 2017 and the tax periods open to examination by foreign jurisdictions include fiscal years 2012 through 2017. We do not anticipate a significant change to the total amount of unrecognized tax benefits within the next 12 months. Significant components of net deferred tax assets and liabilities were as follows: September 30, 2017 2016 Deferred tax assets: Employee benefits $ 5,307 $ 4,612 Inventory 2,863 3,117 Bad debt reserve 585 615 Share-based compensation expense 6,611 8,262 Credit and other carryforwards 22,663 25,596 Other 1,488 1,487 Valuation allowance (2,271 ) (3,022 ) Total deferred tax assets $ 37,246 $ 40,667 Deferred tax liabilities: Depreciation and amortization $ 14,671 $ 17,374 Translation adjustment 300 2,079 Other 739 542 Total deferred tax liabilities $ 15,710 $ 19,995 As of September 30, 2017, the Company had foreign, federal and state net operating loss carryforwards (NOLs) of $5,642, $26,075 and $35,999, respectively, which will expire over the period between fiscal year 2018 and fiscal year 2037, for which we have recorded a $1,039 gross valuation allowance, all of which was attributable to foreign NOLs. The majority of the federal and state NOLs are attributable to the NexPlanar acquisition. As of September 30, 2017, the Company had $1,577 in state tax credit carryforwards, for which we have recorded a $1,409 gross valuation allowance. As of September 30, 2017, the Company had a capital loss carryforward of $2,772, for which we have recorded a full valuation allowance. As of September 30, 2017, the Company had foreign and federal tax credit carryforwards of $4,811 and $3,765, respectively, which will expire beginning in fiscal years 2028 through 2038.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	12 Months Ended
	Sep. 30, 2017
COMMITMENTS AND CONTINGENCIES [Abstract]
COMMITMENTS AND CONTINGENCIES	18. COMMITMENTS AND CONTINGENCIES LEGAL PROCEEDINGS While we are not involved in any legal proceedings that we believe will have a material impact on our consolidated financial position, results of operations or cash flows, we periodically become a party to legal proceedings in the ordinary course of business. PRODUCT WARRANTIES We maintain a warranty reserve that reflects management's best estimate of the cost to replace product that does not meet our specifications and customers' performance requirements, and costs related to such replacement. The warranty reserve is based upon a historical product replacement rate, adjusted for any specific known conditions or circumstances. Additions and deductions to the warranty reserve are recorded in cost of goods sold. Our warranty reserve requirements changed during fiscal 2017 as follows: Balance as of September 30, 2016 $ 243 Reserve for product warranty during the reporting period 530 Settlement of warranty (526 ) Balance as of September 30, 2017 $ 247 INDEMNIFICATION In the normal course of business, we are a party to a variety of agreements pursuant to which we may be obligated to indemnify the other party with respect to certain matters. Generally, these obligations arise in the context of agreements entered into by us, under which we customarily agree to hold the other party harmless against losses arising from items such as a breach of certain representations and covenants including title to assets sold, certain intellectual property rights and certain environmental matters. These terms are common in the industries in which we conduct business. In each of these circumstances, payment by us is subject to certain monetary and other limitations and is conditioned on the other party making an adverse claim pursuant to the procedures specified in the particular agreement, which typically allow us to challenge the other party's claims. We evaluate estimated losses for such indemnifications under the accounting standards related to contingencies and guarantees. We consider such factors as the degree of probability of an unfavorable outcome and the ability to make a reasonable estimate of the amount of loss. To date, we have not experienced material costs as a result of such obligations and, as of September 30, 2017, have not recorded any liabilities related to such indemnifications in our financial statements as we do not believe the likelihood of such obligations is probable. LEASE COMMITMENTS We lease certain vehicles, warehouse facilities, office space, machinery and equipment under cancelable and noncancelable leases, all of which expire within five years from September 30, 2017, and may be renewed by us. Rent expense under such arrangements during fiscal 2017, 2016 and 2015 totaled $3,120, $2,765 and $2,195, respectively. Fiscal Year Operating 2018 $ 3,052 2019 2,587 2020 1,956 2021 1,392 2022 1,084 Thereafter 4,148 $ 14,219 PURCHASE OBLIGATIONS Purchase obligations include our take-or-pay arrangements with suppliers, and purchase orders and other obligations entered into in the normal course of business regarding the purchase of goods and services. We have been operating under a fumed silica supply agreement with Cabot Corporation, our former parent company which is not a related party, the current term of which runs through December 31, 2019. As of calendar year 2017, this agreement has provided us the option to purchase fumed silica, with minimum purchase requirements through 2018, for the term of the agreement, for which As of September 30, 2017, purchase obligations include $9,749 of contractual commitments related to our Cabot Corporation supply agreement for fumed silica. POSTRETIREMENT OBLIGATIONS IN FOREIGN JURISDICTIONS We have unfunded defined benefit plans covering employees in certain foreign jurisdictions as required by local law. Our plans in Japan, which represent the majority of our pension liability for such plans, had projected benefit obligations of $ and $7,091 as of September 30, 2017 and 2016, respectively, and an accumulated benefit obligation of $ and $5,827 as of September 30, 2017 and 2016, respectively. Key assumptions used in the actuarial measurement of the Japan pension liability include weighted average discount rates of and 0.25% at September 30, 2017 and 2016, respectively, and an expected rate of compensation increase of 2.50% and 2.00% at September 30, 2017 and 2016, respectively. Total future Japan pension costs included in accumulated other comprehensive income are $ and $1,667 at September 30, 2017 and 2016, respectively. Our plans in Korea had defined benefit obligations of $ and $1,822 as of September 30, 2017 and 2016. Key assumptions used in the actuarial measurement of the Korea pension liability include weighted average discount rates of and 3.00% at September 30, 2017 and 2016, respectively, and an expected rate of compensation increase of and 5.00% at September 30, 2017 and 2016. Total future Korea pension costs included in accumulated other comprehensive income are $ and $530 at September 30, 2017 and 2016, respectively. Benefit costs for the combined plans were $1,176 $1,024 and $962 in fiscal years 2017, 2016 and 2015, respectively, consisting primarily of service costs, and were recorded as fringe benefit expense under cost of goods sold and operating expenses in our Consolidated Statement of Income. Estimated future benefit payments are as follows: Fiscal Year Amount 2018 $ 304 2019 336 2020 565 2021 412 2022 717 2023 to 2027 $ 3,451

EARNINGS PER SHARE

EARNINGS PER SHARE	12 Months Ended
	Sep. 30, 2017
EARNINGS PER SHARE [Abstract]
EARNINGS PER SHARE	19. EARNINGS PER SHARE Basic earnings per share (EPS) is calculated by dividing net income available to common stockholders by the weighted-average number of common shares outstanding during the period, excluding the effects of unvested restricted stock awards with a right to receive non-forfeitable dividends, which are considered participating securities as prescribed by the two-class method under ASC 260. Diluted EPS is calculated in a similar manner, but the weighted-average number of common shares outstanding during the period is increased to include the weighted-average dilutive effect of "in-the-money" stock options and unvested restricted stock shares using the treasury stock method. The standards of accounting for earnings per share require companies to provide a reconciliation of the numerator and denominator of the basic and diluted earnings per share computations. Basic and diluted earnings per share were calculated as follows: Year Ended September 30, 2017 2016 2015 Numerator: Net income $ 86,952 $ 59,849 $ 56,146 Less: income attributable to participating securities (256 ) (361 ) (483 ) Net income available to common shareholders $ 86,696 $ 59,488 $ 55,663 Denominator: Weighted-average common shares 25,015,458 24,076,549 24,039,692 (Denominator for basic calculation) Weighted-average effect of dilutive securities: Share-based compensation 497,029 400,444 592,123 Diluted weighted-average common shares 25,512,487 24,476,993 24,631,815 (Denominator for diluted calculation) Earnings per share: Basic $ 3.47 $ 2.47 $ 2.32 Diluted $ 3.40 $ 2.43 $ 2.26 For the twelve months ended September 30, 2017, 2016, and 2015, approximately 0.4 million, 1.1 million and 0.7 million shares, respectively, attributable to outstanding stock options were excluded from the calculation of diluted earnings per share.

FINANCIAL INFORMATION BY INDUST

FINANCIAL INFORMATION BY INDUSTRY SEGMENT, GEOGRAPHIC AREA AND PRODUCT LINE	12 Months Ended
	Sep. 30, 2017
FINANCIAL INFORMATION BY INDUSTRY SEGMENT, GEOGRAPHIC AREA AND PRODUCT LINE [Abstract]
FINANCIAL INFORMATION BY INDUSTRY SEGMENT, GEOGRAPHIC AREA AND PRODUCT LINE	20. FINANCIAL INFORMATION BY INDUSTRY SEGMENT, GEOGRAPHIC AREA AND PRODUCT LINE We operate predominantly in one industry segment – the development, manufacture, and sale of CMP consumables. Revenues are attributed to the United States and foreign regions based upon the customer location and not the geographic location from which our products were shipped. Financial information by geographic area was as follows: Year Ended September 30, 2017 2016 2015 Revenue: United States $ 72,670 $ 62,400 $ 55,989 Asia 394,874 336,312 328,669 Europe 39,635 31,737 29,439 Total $ 507,179 $ 430,449 $ 414,097 Property, plant and equipment, net: United States $ 52,155 $ 50,595 $ 43,239 Asia 54,201 55,893 50,504 Europe 5 8 - Total $ 106,361 $ 106,496 $ 93,743 The following table shows revenue from sales to customers in foreign countries that accounted for more than ten percent of our total revenue in fiscal 2017, 2016 and 2015: Year Ended September 30, 2017 2016 2015 Revenue: Taiwan $ 130,849 $ 122,671 $ 124,460 South Korea 95,414 76,082 70,608 China 74,781 59,239 49,350 The following table shows net property, plant and equipment in foreign countries that accounted for more than ten percent of our total net property, plant and equipment in fiscal 2017, 2016 and 2015: Year Ended September 30, 2017 2016 2015 Property, plant and equipment, net: Japan $ 21,408 $ 26,268 $ 22,572 South Korea 16,915 11,135 9,658 Taiwan 15,119 17,949 17,419 The following table shows revenue generated by product area in fiscal 2017, 2016 and 2015: Year Ended September 30, 2017 2016 2015 Revenue: Tungsten slurries $ 221,493 $ 185,365 $ 178,770 Dielectric slurries 120,240 99,141 96,386 Polishing Pads 68,673 52,067 32,048 Other Metals slurries 62,829 63,960 71,640 Engineered Surface Finishes 27,900 22,369 21,534 Data storage slurries 6,044 7,547 13,719 Total $ 507,179 $ 430,449 $ 414,097

SELECTED QUARTERLY OPERATING RE

SELECTED QUARTERLY OPERATING RESULTS	12 Months Ended
	Sep. 30, 2017
SELECTED QUARTERLY OPERATING RESULTS [Abstract]
SELECTED QUARTERLY OPERATING RESULTS	The following table presents our unaudited financial information for the eight quarterly periods ended September 30, 2017. This unaudited financial information has been prepared in accordance with accounting principles generally accepted in the United States of America, applied on a basis consistent with the annual audited financial statements and in the opinion of management, include all necessary adjustments, which consist only of normal recurring adjustments necessary to present fairly the financial results for the periods. The results for any quarter are not necessarily indicative of results for any future period. CABOT MICROELECTRONICS CORPORATION SELECTED QUARTERLY OPERATING RESULTS (Unaudited and in thousands, except per share amounts) Sept. 30, 2017 June 30, 2017 March 31, 2017 Dec. 31, 2016 Sept. 30, 2016 June 30, 2016 March 31, 2016 Dec. 31, 2015 Revenue $ 136,784 $ 127,957 $ 119,184 $ 123,254 $ 122,684 $ 108,152 $ 99,244 $ 100,369 Cost of goods sold 66,734 65,414 59,153 61,749 61,598 56,127 52,348 50,174 Gross profit 70,050 62,543 60,031 61,505 61,086 52,025 46,896 50,195 Operating expenses: Research, development and technical 13,839 14,333 14,090 13,396 15,842 12,928 14,934 14,828 Selling and marketing 8,680 7,346 7,268 7,552 8,057 6,243 6,668 6,749 General and administrative 14,489 13,953 14,699 12,496 11,454 10,738 12,990 14,263 Total operating expenses 37,008 35,632 36,057 33,444 35,353 29,909 34,592 35,840 Operating income 33,042 26,911 23,974 28,061 25,733 22,116 12,304 14,355 Interest expense 1,127 1,117 1,135 1,150 1,187 1,178 1,191 1,167 Other income (expense), net 798 (115 ) 234 996 257 (246 ) 452 190 Income before income taxes 32,713 25,679 23,073 27,907 24,803 20,692 11,565 13,378 Provision for income taxes 6,211 5,740 4,793 5,676 4,096 1,990 2,434 2,069 Net income $ 26,502 $ 19,939 $ 18,280 $ 22,231 $ 20,707 $ 18,702 $ 9,131 $ 11,309 Basic earnings per share $ 1.05 $ 0.79 $ 0.73 $ 0.90 $ 0.85 $ 0.78 $ 0.38 $ 0.46 Weighted average basic shares outstanding 25,236 25,228 25,031 24,583 24,234 23,929 24,061 24,142 Diluted earnings per share $ 1.03 $ 0.77 $ 0.71 $ 0.88 $ 0.83 $ 0.76 $ 0.37 $ 0.46 Weighted average diluted shares outstanding 25,710 25,721 25,526 25,072 24,678 24,325 24,408 24,549 Dividends per share $ 0.20 $ 0.20 $ 0.20 $ 0.18 $ 0.18 $ 0.18 $ 0.18 $ -

SCHEDULE II - VALUATION AND QUA

SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS	12 Months Ended
	Sep. 30, 2017
SCHEDULE II-VALUATION AND QUALIFYING ACCOUNTS [Abstract]
SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS	The following table sets forth activities in our allowance for doubtful accounts: Allowance For Doubtful Accounts Balance At Beginning of Year Amounts Charged To Expenses Deductions and Adjustments Balance At End Of Year Year ended: September 30, 2017 $ 1,828 $ 26 $ (107 ) $ 1,747 September 30, 2016 1,224 588 16 1,828 September 30, 2015 1,392 (84 ) (84 ) 1,224 We maintain a warranty reserve that reflects management's best estimate of the cost to replace product that does not meet our specifications and customers' performance requirements, and costs related to such replacement. The warranty reserve is based upon a historical product replacement rate, adjusted for any specific known conditions or circumstances. Additions and deductions to the warranty reserve are recorded in cost of goods sold. Charges to expenses and deductions, shown below, represent the net change required to maintain an appropriate reserve. Warranty Reserves Balance At Beginning of Year Reserve For Product Warranty During the Reporting Period AdjustmentsTo Pre-existing Warranty Reserve Settlement of Warranty Balance At End Of Year Year ended: September 30, 2017 $ 243 $ 530 $ - $ (526 ) $ 247 September 30, 2016 209 595 - (561 ) 243 September 30, 2015 246 608 - (645 ) 209 We have provided a valuation allowance on certain deferred tax assets. The following table sets forth activities in our valuation allowance: Valuation Allowance Balance At Beginning of Year Amounts Charged To Expenses Deductions and Adjustments Balance At End Of Year Year ended: September 30, 2017 $ 3,022 $ - $ (751 ) $ 2,271 September 30, 2016 3,079 - (57 ) 3,022 September 30, 2015 2,912 167 - 3,079

SUMMARY OF SIGNIFICANT ACCOUN30

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
	Sep. 30, 2017
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES [Abstract]
PRINCIPLES OF CONSOLIDATION	PRINCIPLES OF CONSOLIDATION The consolidated financial statements include the accounts of Cabot Microelectronics and its subsidiaries. All intercompany transactions and balances between the companies have been eliminated in the consolidated financial statements as of September 30, 2017.
USE OF ESTIMATES	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 challenging and subjective judgments include, but are not limited to, those estimates related to bad debt expense, inventory valuation, valuation and classification of auction rate securities, impairment of long-lived assets and investments, business combinations, goodwill, other intangible assets, interest rate swaps, net investment hedge, 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.
CASH, CASH EQUIVALENTS AND SHORT-TERM INVESTMENTS	CASH, CASH EQUIVALENTS AND SHORT-TERM INVESTMENTS We consider investments in all highly liquid financial instruments with original maturities of three months or less to be cash equivalents. Short-term investments include securities generally having maturities of 90 days to one year. We did not own any securities that were considered short-term as of September 30, 2017 or 2016. See Note 4 for a more detailed discussion of other financial instruments.
ACCOUNTS RECEIVABLE AND ALLOWANCE FOR DOUBTFUL ACCOUNTS	ACCOUNTS RECEIVABLE AND ALLOWANCE FOR DOUBTFUL ACCOUNTS Trade accounts receivable are recorded at the invoiced amount and do not bear interest. We maintain an allowance for doubtful accounts for estimated losses resulting from the potential inability of our customers to make required payments. Our allowance for doubtful accounts is based on historical collection experience, adjusted for any specific known conditions or circumstances such as customer bankruptcies and increased risk due to economic conditions. Uncollectible account balances are charged against the allowance when we believe that it is probable that the receivable will not be recovered. Amounts charged to bad debt expense are recorded in general and administrative expenses. A portion of our receivables and the related allowance for doubtful accounts is denominated in foreign currencies, so they are subject to foreign exchange fluctuations which are included in the table below under deductions and adjustments. Our allowance for doubtful accounts changed during the fiscal year ended September 30, 2017 as follows: Balance as of September 30, 2016 $ 1,828 Amounts charged to expense 26 Deductions and adjustments (107 ) Balance as of September 30, 2017 $ 1,747
CONCENTRATION OF CREDIT RISK	CONCENTRATION OF CREDIT RISK Financial instruments that subject us to concentrations of credit risk consist principally of accounts receivable. We perform ongoing credit evaluations of our customers' financial conditions and generally do not require collateral to secure accounts receivable. Our exposure to credit risk associated with nonpayment is affected principally by conditions or occurrences within the semiconductor industry and global economy. With the exception of one customer bankruptcy in fiscal 2012 and a customer placed into receivership in fiscal 2016, we have not experienced significant losses relating to accounts receivable from individual customers or groups of customers. Customers who represented more than 10% of revenue are as follows: Year Ended September 30, 2017 2016 2015 Samsung Group (Samsung) 16% 15% 15% Taiwan Semiconductor Manufacturing Co. (TSMC) 13% 15% 18% Micron Technology Inc. 10% * * * Not a customer with more than 10% revenue in fiscal 2016 and 2015. TSMC accounted for 12.2% and 12.9% of net accounts receivable at September 30, 2017 and 2016, respectively. Samsung accounted for 11.9% and 8.3% of net accounts receivable at September 30, 2017 and 2016, respectively. Micron accounted for 10.7% and 7.2% of net accounts receivable at September 30, 2017 and 2016, respectively. Due to recent financial challenges experienced by Toshiba, we continue to monitor their financial condition and ability to make the required payments due on our receivables. At September 30, 2017 our accounts receivable balance with Toshiba represented a U.S. dollar equivalent of $2,323, which equates to 3.6% of our total accounts receivable balance of $64,793, net of allowance for doubtful accounts, and of which no amounts are past due. At present, we do not believe it is probable that the receivables from Toshiba are impaired, and accordingly, we have not recorded a related allowance for doubtful accounts.
FAIR VALUES OF FINANCIAL INSTRUMENTS	FAIR VALUES OF FINANCIAL INSTRUMENTS The recorded amounts of cash, accounts receivable, and accounts payable approximate their fair values due to their short-term, highly liquid characteristics. See Note 4 for a more detailed discussion of the fair value of financial instruments.
INVENTORIES	INVENTORIES Inventories are stated at the lower of cost, determined on the first-in, first-out (FIFO) basis, or market. Finished goods and work in process inventories include material, labor and manufacturing overhead costs. We regularly review and write down the value of inventory as required for estimated obsolescence or lack of marketability. An inventory reserve is maintained based upon a historical percentage of actual inventories written off and applied against inventory value at the end of the period, adjusted for known conditions and circumstances.
PROPERTY, PLANT AND EQUIPMENT	PROPERTY, PLANT AND EQUIPMENT Property, plant and equipment are recorded at cost. Depreciation is based on the following estimated useful lives of the assets using the straight-line method: Buildings 15-25 years Machinery and equipment 3-10 years Furniture and fixtures 5-10 years Information systems 3-5 years Expenditures for repairs and maintenance are charged to expense as incurred. Expenditures for major renewals and betterments are capitalized and depreciated over the remaining useful lives. As assets are retired or sold, the related cost and accumulated depreciation are removed from the accounts and any resulting gain or loss is included in the results of operations. We capitalize the costs related to the design and development of software used for internal purposes; however, these costs are not material.
IMPAIRMENT OF LONG-LIVED ASSETS	IMPAIRMENT OF LONG-LIVED ASSETS Reviews are regularly performed to determine whether facts and circumstances exist that indicate the carrying amount of assets may not be recoverable or the useful life is shorter than originally estimated. Asset recoverability assessment begins by comparing the projected undiscounted cash flows associated with the related asset or group of assets over their remaining lives against their respective carrying amounts. Impairment, if any, is based on the excess of the carrying amount over the fair value of those assets. If assets are determined to be recoverable, but their useful lives are shorter than originally estimated, the net book value of the asset is depreciated over the newly determined remaining useful life. We recorded impairment expense on a certain long-lived asset of $860 in fiscal year 2017, which was subsequently sold for a gain. We did not record any impairment expense on property, plant and equipment in fiscal 2016 and 2015. See Note 6 for more information regarding impairment.
WARRANTY RESERVE	WARRANTY RESERVE We maintain a warranty reserve that reflects management's best estimate of the cost to replace product that does not meet our specifications and customers' performance requirements. The warranty reserve is based upon a historical product return rate, adjusted for any specific known conditions or circumstances. Adjustments to the warranty reserve are recorded in cost of goods sold.
GOODWILL AND INTANGIBLE ASSETS	GOODWILL AND INTANGIBLE ASSETS We amortize intangible assets with finite lives over their estimated useful lives, which range from one to eleven years. Intangible assets with finite lives are reviewed for impairment using a process similar to that used to evaluate other long-lived assets. Goodwill and indefinite-lived intangible assets are not amortized and are tested annually in the fourth fiscal quarter, or more frequently if indicators of potential impairment exist, using a fair-value-based approach. The recoverability of goodwill is measured at the reporting unit level, which is defined as either an operating segment or one level below an operating segment, referred to as a component. A component is a reporting unit when the component constitutes a business for which discrete financial information is available and segment management regularly reviews the operating results of the component. Components may be combined into one reporting unit when they have similar economic characteristics. We have four reporting units, all of which have goodwill as of September 30, 2017. Goodwill impairment testing requires a comparison of the fair value of each reporting unit to the carrying value. If the carrying value exceeds fair value, then the fair value of the assets and liabilities for the reporting unit is used to determine the "implied" fair value of goodwill. The amount of the impairment is the difference between the carrying value and the implied fair value of goodwill. Accounting guidance provides an entity the option to assess the fair value of a reporting unit either using a qualitative analysis ("step zero") or a quantitative analysis ("step one"). In fiscal 2015, 2016 and 2017, we chose to use a step one analysis for goodwill impairment. Similarly, an entity has the option to use a step zero or step one approach to determine the recoverability of indefinite-lived intangible assets. In fiscal 2015, 2016 and 2017, we used a step one analysis to determine the recoverability of indefinite-lived intangible assets. As discussed in more detail in Note 3, we recorded $1,000 in impairment expense on an in-process technology asset during the fourth quarter of fiscal 2016. We determined that goodwill and the other intangible assets were not impaired as of September 30, 2017.
FOREIGN CURRENCY TRANSLATION	FOREIGN CURRENCY TRANSLATION Certain operating activities in Asia and Europe are denominated in local currency, considered to be the functional currency. Assets and liabilities of these operations are translated using exchange rates in effect at the end of the year, and revenue and costs are translated using average exchange rates for the year. The related translation adjustments are reported in comprehensive income in stockholders' equity.
FOREIGN EXCHANGE MANAGEMENT	FOREIGN EXCHANGE MANAGEMENT We transact business in various foreign currencies, primarily the Japanese yen, New Taiwan dollar and Korean won. Our exposure to foreign currency exchange risks has not been significant because a large portion of our business is denominated in U.S. dollars. However, there was a weakening of the Japanese yen against the U.S. dollar during fiscal years 2015, 2016 and part of 2017, which had some net positive impact on our gross margin percentage and our net income. Periodically, we enter into certain forward foreign exchange contracts in an effort to mitigate the risks associated with currency fluctuations on certain foreign currency balance sheet exposures. These foreign exchange contracts do not qualify for hedge accounting; therefore, the gains and losses resulting from the impact of currency exchange rate movements on our forward foreign exchange contracts are recognized as other income or expense in the accompanying consolidated income statements in the period in which the exchange rates change. See Note 11 for a discussion of derivative financial instruments.
INTERCOMPANY LOAN ACCOUNTING	INTERCOMPANY LOAN ACCOUNTING We maintain an intercompany loan agreement with our wholly-owned subsidiary, Nihon Cabot Microelectronics K.K. ("Nihon"), under which we provided funds to Nihon to finance the purchase of certain assets from our former Japanese branch at the time of the establishment of this subsidiary, for the purchase of land adjacent to our facility in Geino, Japan, for the construction of our Asia Pacific technology center, and for the purchase of a 300 millimeter polishing tool and related metrology equipment, all of which are assets of Nihon, as well as for general business purposes. Since settlement of the note is expected in the foreseeable future, and our subsidiary has made timely payments on the loan, the loan is considered a foreign-currency transaction. Therefore, the associated foreign exchange gains and losses are recognized as other income or expense rather than being deferred in the cumulative translation account in other comprehensive income. We also maintain an intercompany loan between two of our wholly-owned foreign subsidiaries, from Cabot Microelectronics Singapore Pte. Ltd. to Hanguk Cabot Microelectronics, LLC in South Korea. This loan provided funds for the construction and operation of our research, development and manufacturing facility in South Korea. This loan is also considered a foreign currency transaction and is accounted for in the same manner as our intercompany loan to Nihon. These intercompany loans are eliminated from our Consolidated Balance Sheet in consolidation.
PURCHASE COMMITMENTS	PURCHASE COMMITMENTS We have entered into unconditional purchase obligations, which include noncancelable purchase commitments and take-or-pay arrangements with suppliers. On an ongoing basis, we review our agreements and assess the likelihood of a shortfall in purchases and determine if it is necessary to record a liability. See Note 18 for additional discussion of purchase commitments. To date, we have not recorded such a liability.
REVENUE RECOGNITION	REVENUE RECOGNITION Revenue from CMP consumables products is recognized when title is transferred to the customer, assuming all revenue recognition criteria are met. Title transfer generally occurs upon shipment to the customer or when inventory held on consignment is consumed by the customer, subject to the terms and conditions of the particular customer arrangement. We have consignment agreements with a number of our customers that require, at a minimum, monthly consumption reports that enable us to record revenue and inventory usage in the appropriate period. Although the majority of our products are sold directly, we market some of our products through distributors in certain areas of the world. We recognize revenue upon shipment and when title is transferred to the distributor. We do not have any arrangements with distributors that include payment terms, rights of return, or rights of exchange outside the ordinary course of business, or any other significant matters that we believe would impact the timing of revenue recognition. Within our Engineered Surface Finishes (ESF) business, sales of equipment are recorded as revenue upon delivery and customer acceptance. Amounts allocated to installation and training are deferred until those services are provided and are not material. Revenues are reported net of any value-added tax or other such tax assessed by a governmental authority on our revenue-producing activities.
SHIPPING AND HANDLING	SHIPPING AND HANDLING Costs related to shipping and handling are included in cost of goods sold.
RESEARCH, DEVELOPMENT AND TECHNICAL	RESEARCH, DEVELOPMENT AND TECHNICAL Research, development and technical costs are expensed as incurred and consist primarily of staffing costs, materials and supplies, depreciation, utilities and other facilities costs.
INCOME TAXES	INCOME TAXES Current income taxes are determined based on estimated taxes payable or refundable on tax returns for the current year. Deferred income taxes are determined based on differences between the book and tax bases of recorded assets and liabilities, using enacted tax rates. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. Provisions are made for both U.S. and any foreign deferred income tax liability or benefit. We assess whether our deferred tax assets will ultimately be realized and record an estimated valuation allowance on those deferred tax assets that may not be realized. We recognize the tax benefit of an uncertain tax position only if it is more likely than not that the tax position will be sustained by the taxing authorities, based on the technical merits of the position. In fiscal years 2015, 2016 and 2017 we elected to permanently reinvest the earnings of all of our foreign subsidiaries rather than repatriate the earnings to the U.S. See Note 17 for additional information on income taxes.
DERIVATIVE HEDGING INSTRUMENTS	INTEREST RATE SWAPS In fiscal 2015, we entered into floating-to-fixed interest rate swap agreements to hedge the variability in LIBOR-based interest payments on a portion of our outstanding variable rate debt. The fair value of our interest rate swaps is estimated using standard valuation models using market-based observable inputs over the contractual term, including one-month LIBOR-based yield curves, among others. We consider the risk of nonperformance, including counterparty credit risk, in the calculation of the fair value. We have designated these swap agreements as cash flow hedges pursuant to ASC 815, "Derivatives and Hedging". As cash flow hedges, unrealized gains are recognized as assets and unrealized losses are recognized as liabilities. Unrealized gains and losses are designated as effective or ineffective based on a comparison of the changes in fair value of the interest rate swaps and changes in fair value of the underlying exposures being hedged. The effective portion is recorded as a component of accumulated other comprehensive income or loss, while the ineffective portion is recorded as a component of interest expense. Changes in the method by which we pay interest from one-month LIBOR to another rate of interest could create ineffectiveness in the swaps, and result in amounts being reclassified from other comprehensive income into net income. Hedge effectiveness is tested quarterly to determine if hedge treatment is appropriate. NET INVESTMENT HEDGE In the fourth quarter of fiscal 2017, we entered into forward foreign exchange contracts in an effort to protect our net investment in a foreign operation against potential adverse changes resulting from foreign currency fluctuation. This transaction is designated as a net The fair value of our forward foreign exchange contracts is estimated using a standard valuation model and market-based observable inputs over the contractual term, including forward rates and/or the Overnight Index Swap (OIS) curve as of the valuation date. Unrealized gains are recognized as assets and unrealized losses are recognized as liabilities. Hedge effectiveness is assessed using the Forward Method, consistent with guidance in ASC 815. Consistent with this guidance, the entire change in fair value of the forward contracts is recorded in the same manner as the related currency translation adjustments, within other comprehensive income, as the hedging instruments are expected to be fully effective unless the amount hedged exceeds the net investment in the foreign operation, or the foreign operation is liquidated. See Note 11 for a discussion of derivative financial instruments.
SHARE-BASED COMPENSATION	SHARE-BASED COMPENSATION We record share-based compensation expense for all share-based awards, including stock option grants, restricted stock and restricted stock unit awards and employee stock purchase plan purchases. We calculate share-based compensation expense using the straight-line approach based on awards expected to vest, which requires the use of an estimated forfeiture rate. Our estimated forfeiture rate is primarily based on historical experience, but may be revised in future periods if actual forfeitures differ from the estimate. We use the Black-Scholes option-pricing model to estimate the grant date fair value of our stock options and employee stock purchase plan purchases. This model requires the input of highly subjective assumptions, including the price volatility of the underlying stock, the expected term of our stock options, expected dividend yield, and the risk-free interest rate. We estimate the expected volatility of our stock options based on a combination of our stock's historical volatility and the implied volatilities from actively-traded options on our stock. We calculate the expected term of our stock options using historical stock option exercise data, and we add a slight premium to this expected term for employees who meet the definition of retirement eligible pursuant to their grants during the contractual term of the grant. The expected dividend yield represents our annualized dividend in dollars divided by the stock price on the date of grant. The risk-free rate is derived from the U.S. Treasury yield curve in effect at the time of grant. The fair value of our restricted stock and restricted stock unit awards represents the closing price of our common stock on the date of award. For additional information regarding our share-based compensation plans, refer to Note 13.
EARNINGS PER SHARE	EARNINGS PER SHARE Basic earnings per share (EPS) is calculated by dividing net income available to common stockholders by the weighted-average number of common shares outstanding during the period, excluding the effects of unvested restricted stock awards with a right to receive non-forfeitable dividends, which are considered participating securities as prescribed by the two class method under ASC Topic 260, Earnings Per Share (ASC 260). Diluted EPS is calculated in a similar manner, but the weighted-average number of common shares outstanding during the period is increased to include the weighted-average dilutive effect of "in-the-money" stock options and unvested restricted stock shares using the treasury stock method.
COMPREHENSIVE INCOME	COMPREHENSIVE INCOME Comprehensive income primarily differs from net income due to foreign currency translation adjustments. EFFECTS OF RECENT ACCOUNTING PRONOUNCEMENTS
EFFECTS OF RECENT ACCOUNTING PRONOUNCEMENTS	In May 2014, the FASB issued ASU No. 2014-09, "Revenue from Contracts with Customers" (Topic 606), an updated standard on revenue recognition . In July 2015, the FASB issued ASU No, 2015-11, "Simplifying the Measurement of Inventory" (Topic 330). The provisions of ASU 2015-11 require an entity to measure inventory at the lower of cost and net realizable value. Net realizable value is the estimated selling price in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. ASU 2015-11 will be effective for us beginning October 1, 2017, but early adoption is permitted. We do not believe the adoption of this standard will have a material effect on our financial statements. In February 2016, the FASB issued ASU No. 2016-02, "Leases" (Topic 842). The provisions of ASU 2016-02 require a dual approach for lessee accounting under which a lessee would recognize a right-of-use asset and a corresponding lease liability. Leases will be classified as either finance or operating leases. For finance leases, a lessee will recognize interest expense and amortization of the right-of-use asset, and for operating leases, the lessee will recognize a straight-line total lease expense. The guidance also requires qualitative and specific quantitative disclosures to supplement the amounts recorded in the financial statements, to afford better understanding of an entity's leasing activities, including any significant judgments and estimates. ASU 2016-02 will be effective for us beginning October 1, 2019, but early adoption is permitted. We are currently evaluating the impact of implementation of this standard on our financial statements. In March 2016, the FASB issued ASU No. 2016-05, "Effect of Derivative Contract Novations on Existing Hedge Accounting Relationships" (Topic 815). The provisions of ASU 2016-05 provide clarification that a change in a counterparty of a derivative instrument that has been designated as a hedging instrument does not require dedesignation of that hedging relationship, provided that all other hedge accounting criteria is met. ASU 2016-05 will be effective for us beginning October 1, 2018, but early adoption is permitted. We do not believe the adoption of this standard will have a material effect on our financial statements. In March 2016, the FASB issued ASU No. 2016-07, "Simplifying the Transition to the Equity Method of Accounting" (Topic 323). The provisions of ASU 2016-07 require equity method investors to add the cost of acquiring additional interest in the investee to the current basis of the investor's previously held interest and adopt the equity method prospectively as of the date the investment qualifies for the equity method of accounting. ASU 2016-07 will be effective for us beginning October 1, 2018, but early adoption is permitted. We do not believe the adoption of this standard will have a material effect on our financial statements as we currently have no equity method investments. In March 2016, the FASB issued ASU No. 2016-09, "Improvements to Employee Share Based Payment Accounting" (Topic 718). The provisions of this standard involve several aspects of the accounting for share-based payments transactions, including income tax consequences, classification of awards as either equity or liabilities, and classification on the statement of cash flows. ASU 2016-09 will be effective for us beginning October 1, 2017, but early adoption is permitted. We currently expect that the adoption of this standard will introduce additional variability in our effective tax rate; however, the impact will not be known until the related share-based award activity occurs. The adoption will also impact the classification of excess tax benefits on the Consolidated Statements of Cash Flows. In June 2016, the FASB issued ASU No. 2016-13, "Measurement of Credit Losses on Financial Instruments" (Topic 326). The provisions of this standard require financial assets measured at amortized cost to be presented at the net amount expected to be collected. An allowance account would be established to present the net carrying value at the amount expected to be collected. ASU 2016-13 also provides that credit losses relating to available-for-sale debt securities should be recorded through an allowance for credit losses. ASU 2016-13 will be effective for us beginning October 1, 2020, but early adoption is permitted as of October 1, 2019. We are currently evaluating the impact of implementation of this standard on our financial statements. In August 2016, the FASB issued ASU No. 2016-15 "Classification of Certain Cash Receipts and Cash Payments" (Topic 230). The provisions of this standard provide guidance on the classification within the statement of cash flows of certain types of cash receipts and cash payments in an effort to eliminate diversity in practice. ASU 2016-15 will be effective for us beginning October 1, 2018, but early adoption is permitted. We do not believe the adoption of this standard will have a material effect on our financial statements as we currently do not have any of the cash receipts or payments discussed in this standard. In October 2016, the FASB issued ASU No. 2016-16 "Intra-Entity Transfers of Assets Other Than Inventory" (Topic 740). The provisions of this standard provide guidance on recognition of taxes related to intra-entity transfer of assets other than inventory when the transfer occurs. ASU 2016-16 will be effective for us beginning October 1, 2018, but early adoption is permitted. We are currently evaluating the impact of implementation of this standard on our financial statements. In October 2016, the FASB issued ASU No. 2016-17 "Interest Held through Related Parties That Are under Common Control" (Topic 810). The provisions of this standard provide further guidance related to ASU 2015-02, and also provide guidance on consolidation in relation to VIEs and related parties. ASU 2016-17 will be effective for us beginning October 1, 2017, but early adoption is permitted. We do not believe the adoption of this standard will have a material effect on our financial statements as we currently have no interest in any entities that may be considered VIE. In January 2017, the FASB issued ASU No. 2017-01 "Clarifying the Definition of a Business" (Topic 805). The provisions of this standard provide guidance to determine whether the acquisition or sale of a set of assets or activities constitutes a business. The standard requires that an integrated set of assets and activities include an input and a substantive process that together contribute to the ability to create output. ASU 2017-01 will be effective for us beginning October 1, 2017, and early adoption is permitted under specified conditions. We do not believe the adoption of this standard will have a material effect on our financial statements. In January 2017, the FASB issued ASU No. 2017-04 "Simplifying the Test for Goodwill Impairment" (Topic 350). The provisions of this standard eliminate Step 2 from the goodwill impairment test, which required an entity to determine the fair value of its assets and liabilities at the impairment testing date of its goodwill and compare it to its carrying amount to determine a possible impairment loss. Goodwill impairment testing will now be done by comparing the fair value of a reporting unit and its carrying amount. ASU 2017-04 will be effective for us beginning October 1, 2020, but early adoption is permitted as of October 1, 2017. We are currently evaluating the impact of implementation of this standard on our financial statements. In March 2017, the FASB issued ASU No. 2017-07 "Improving the Presentation of Net Period Pension Cost and Net Period Postretirement Benefit Cost" (Topic 715). The provisions of ASU 2017-07 provided specific guidance on the presentation of the components of net benefit cost. ASU 2017-07 will be effective for us beginning October 1, 2018. We are currently evaluating the impact of implementation of this standard on our financial statements. In May 2017, the FASB issued ASU No. 2017-09 "Scope of Modification Accounting" (Topic 718). The provisions of ASU 2017-09 provide specific guidance about which changes to the term or conditions of a share-based payment require an entity to apply modification accounting. ASU 2017-09 will be effective for us beginning October 1, 2018. We are currently evaluating the impact of implementation of this standard on our financial statements. In August 2017, the FASB issued ASU No. 2017-12 "Derivatives and Hedging" (Topic 815). The provisions of this standard amend the hedge accounting model in ASC 815 to expand an entity's ability to hedge nonfinancial and financial risk components, reduce complexity in fair value hedges of interest rate risk, eliminate the requirement to separately measure and report hedge ineffectiveness, and generally require the entire change in the fair value of a hedging instrument to be presented in the same income statement line as the hedged item. The guidance also eases certain documentation and assessment requirements and modifies the accounting for components excluded from the assessment of hedge effectiveness. ASU 2017-09 will be effective for us beginning October 1, 2019, but early adoption is permitted. We are currently evaluating the impact of implementation of this standard on our financial statements.

SUMMARY OF SIGNIFICANT ACCOUN31

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	12 Months Ended
	Sep. 30, 2017
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES [Abstract]
Schedule of Allowance for Doubtful Accounts	Our allowance for doubtful accounts changed during the fiscal year ended September 30, 2017 as follows: Balance as of September 30, 2016 $ 1,828 Amounts charged to expense 26 Deductions and adjustments (107 ) Balance as of September 30, 2017 $ 1,747
Schedule of Customers Representing More than Ten Percent of Total Revenue	Customers who represented more than 10% of revenue are as follows: Year Ended September 30, 2017 2016 2015 Samsung Group (Samsung) 16% 15% 15% Taiwan Semiconductor Manufacturing Co. (TSMC) 13% 15% 18% Micron Technology Inc. 10% * * * Not a customer with more than 10% revenue in fiscal 2016 and 2015.
Schedule of Property, Plant and Equipment Useful Lives	Property, plant and equipment are recorded at cost. Depreciation is based on the following estimated useful lives of the assets using the straight-line method: Buildings 15-25 years Machinery and equipment 3-10 years Furniture and fixtures 5-10 years Information systems 3-5 years

BUSINESS COMBINATION (Tables)

BUSINESS COMBINATION (Tables)	12 Months Ended
	Sep. 30, 2017
BUSINESS COMBINATION [Abstract]
Assets Acquired and Liabilities Assumed	The following table summarizes the fair values of assets acquired and liabilities assumed as of the date of acquisition: Total purchase consideration $ 142,237 Cash $ 15,261 Accounts receivable 3,052 Inventories 2,768 Prepaid expenses and other current assets 1,712 Property, plant and equipment 6,901 Intangible assets 55,000 Deferred tax assets 20,509 Other long-term assets 1,458 Accounts payable (1,057 ) Accrued expenses and other current liabilities (1,472 ) Deferred tax liabilities (20,313 ) Total identifiable net assets 83,819 Goodwill 58,418 $ 142,237
Components of Identifiable Intangible Assets	The following table sets forth the components of identifiable intangible assets acquired and their estimated useful lives as of the date of acquisition: Fair Useful Value Life Trade name $ 8,000 7 years Customer relationships 8,000 11 years Developed technology - product family A 32,000 7 years Developed technology - product family B 2,000 9 years In-process technology 5,000 Total intangible assets $ 55,000
Pro Forma Combined Results of Operations	The following supplemental pro forma information summarizes the combined results of operations for Cabot Microelectronics and NexPlanar as if the acquisition had occurred on October 1, 2014. Year Ended September 30, 2016 2015 Revenues $ 431,856 $ 437,326 Net income 60,620 46,928 Earnings per share - basic 2.50 1.93 Earnings per share - diluted $ 2.46 $ 1.89

FAIR VALUE OF FINANCIAL INSTR33

FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)	12 Months Ended
	Sep. 30, 2017
FAIR VALUE OF FINANCIAL INSTRUMENTS [Abstract]
Schedule of Fair Value of Financial Instruments	The following table presents financial instruments, other than long-term debt, that we measured at fair value on a recurring basis at 2017 and 2016 September 30, 2017 Level 1 Level 2 Level 3 Total Fair Value Assets: Cash and cash equivalents $ 397,890 $ - $ - $ 397,890 Other long-term investments 929 - - 929 Derivative financial instruments - 263 - 263 Total assets $ 398,819 $ 263 $ - $ 399,082 Liabilities: Derivative financial instruments - 1,881 - 1,881 Total liabilities $ - $ 1,881 $ - $ 1,881 September 30, 2016 Level 1 Level 2 Level 3 Total Fair Value Assets: Cash and cash equivalents $ 287,479 $ - $ - $ 287,479 Other long-term investments 1,028 - - 1,028 Derivative financial instruments - 28 - 28 Total assets $ 288,507 $ 28 $ - $ 288,535 Liabilities: Derivative financial instruments - 1,469 - 1,469 Total liabilities $ - $ 1,469 $ - $ 1,469

INVENTORIES (Tables)

INVENTORIES (Tables)	12 Months Ended
	Sep. 30, 2017
INVENTORIES [Abstract]
Schedule of Inventories	Inventories consisted of the following: September 30, 2017 2016 Raw materials $ 36,415 $ 45,109 Work in process 7,365 4,668 Finished goods 28,093 22,346 Total $ 71,873 $ 72,123

PROPERTY, PLANT AND EQUIPMENT (

PROPERTY, PLANT AND EQUIPMENT (Tables)	12 Months Ended
	Sep. 30, 2017
PROPERTY, PLANT AND EQUIPMENT [Abstract]
Schedule of Property, Plant and Equipment	Property, plant and equipment consisted of the following: September 30, 2017 2016 Land $ 17,823 $ 18,636 Buildings 104,057 100,084 Machinery and equipment 187,649 198,870 Furniture and fixtures 6,770 6,642 Information systems 32,748 29,573 Construction in progress 10,439 6,358 Total property, plant and equipment 359,486 360,163 Less: accumulated depreciation (253,125 ) (253,667 ) Net property, plant and equipment $ 106,361 $ 106,496

GOODWILL AND OTHER INTANGIBLE36

GOODWILL AND OTHER INTANGIBLE ASSETS (Tables)	12 Months Ended
	Sep. 30, 2017
GOODWILL AND OTHER INTANGIBLE ASSETS [Abstract]
Components of Other Intangible Assets	The components of other intangible assets are as follows: September 30, 2017 September 30, 2016 Gross Carrying Amount Accumulated Amortization Gross Carrying Amount Accumulated Amortization Other intangible assets subject to amortization: Product technology $ 42,287 $ 17,604 $ 42,194 $ 12,718 Acquired patents and licenses 8,270 8,241 8,270 8,155 Trade secrets and know-how 2,550 2,550 2,550 2,550 Customer relationships, distribution rights and other 28,229 15,421 27,900 12,205 Total other intangible assets subject to amortization 81,336 43,816 80,914 35,628 Other intangible assets not subject to amortization: In-process technology 4,000 4,000 Other indefinite-lived intangibles* 1,190 1,190 Total other intangible assets not subject to amortization 5,190 5,190 Total other intangible assets $ 86,526 $ 43,816 $ 86,104 $ 35,628 * Other indefinite-lived intangibles not subject to amortization primarily consist of trade names.
Estimated Future Amortization Expense for the Succeeding Five Fiscal Years	Amortization expense was $7,795, $8,176 and $2,346 for fiscal 2017, 2016 and 2015, respectively. Estimated future amortization expense of intangible assets as of September 30, 2017 for the five succeeding fiscal years is as follows: Fiscal Year Estimated Amortization Expense 2018 $ 7,118 2019 6,675 2020 6,670 2021 6,664 2022 6,664

OTHER LONG-TERM ASSETS (Tables)

OTHER LONG-TERM ASSETS (Tables)	12 Months Ended
	Sep. 30, 2017
OTHER LONG-TERM ASSETS [Abstract]
Schedule of Other Long-Term Assets	Other long-term assets consisted of the following: September 30, 2017 2016 Auction rate securities (ARS) $ 5,319 $ 5,494 Long-term contract asset 2,115 3,055 Other long-term assets 2,154 2,465 Other long-term investments 929 1,028 Total $ 10,517 $ 12,042

ACCRUED EXPENSES, INCOME TAXE38

ACCRUED EXPENSES, INCOME TAXES PAYABLE AND OTHER CURRENT LIABILITIES (Tables)	12 Months Ended
	Sep. 30, 2017
ACCRUED EXPENSES, INCOME TAXES PAYABLE AND OTHER CURRENT LIABILITIES [Abstract]
Schedule of Accrued Expenses, Income Taxes Payable and Other Current Liabilities	Accrued expenses, income taxes payable and other current liabilities consisted of the following: September 30, 2017 2016 Accrued compensation $ 35,332 $ 17,856 Dividends payable 5,314 4,502 Goods and services received, not yet invoiced 2,172 2,648 Deferred revenue and customer advances 1,559 782 Warranty accrual 247 243 Income taxes payable 9,717 7,878 Taxes, other than income taxes 1,688 775 Current portion of long-term contract liability 1,500 1,500 Other 5,122 5,211 Total $ 62,651 $ 41,395

DEBT (Tables)

DEBT (Tables)	12 Months Ended
	Sep. 30, 2017
DEBT [Abstract]
Schedule of Maturities of Long-Term Debt	Principal repayments of the Term Loan are generally made on the last calendar day of each quarter if that day is considered to be a business day. As of September 30, 2017, scheduled principal repayments of the Term Loan were as follows: Fiscal Year Principal Repayments 2018 $ 10,938 2019 133,438 Total $ 144,376

DERIVATIVE FINANCIAL INSTRUME40

DERIVATIVE FINANCIAL INSTRUMENTS (Tables)	12 Months Ended
	Sep. 30, 2017
DERIVATIVE FINANCIAL INSTRUMENTS [Abstract]
Schedule of Fair Value of Derivative Instruments in the Consolidated Balance Sheet	The fair value of our derivative instruments included in the Consolidated Balance Sheet, which was determined using level 2 inputs, was as follows: Asset Derivatives Liability Derivatives September 30, September 30, Consolidated Balance Sheet Location 2017 2016 2017 2016 Derivatives designated as hedging instruments Interest rate swap contracts Other long-term assets $ 117 $ - $ - $ - Accrued expenses, income taxes payable and other current liabilities $ - $ - $ 31 $ 612 Other long-term liabilities $ - $ - $ - $ 655 Foreign exchange contracts designated as net investment hedge Other long-term liabilities - - 1,442 - Derivatives not designated as hedging instruments Foreign exchange contracts Prepaid expenses and other current assets $ 146 $ 28 $ - $ - Accrued expenses, income taxes payable and other current liabilities $ - $ - $ 408 $ 202
Schedule of the Effect of Derivative Instruments on the Consolidated Statement of Income	The following table summarizes the effect of our derivative instrument on our Consolidated Statements of Income for the fiscal years ended September 30, 2017, 2016 and 2015: Gain (Loss) Recognized in Consolidated Statements of Income Fiscal Year Ended September 30, Derivatives not designated as hedging instruments Consolidated Statements of Income Location 2017 2016 2015 Foreign exchange contracts Other income (expense), net $ (1,462 ) $ 676 $ (1,674 )
Schedule of Net Investment Hedges in Accumulated Other Comprehensive Income	Amounts recognized in Other comprehensive income (loss) for our net investment hedge during the fiscal year ended September 30, were as follows: 2017 Loss on net investment hedge $ 1,442 Tax benefit (522 ) Loss on net investment hedge, net of tax $ 920

ACCUMULATED OTHER COMPREHENSI41

ACCUMULATED OTHER COMPREHENSIVE INCOME (Tables)	12 Months Ended
	Sep. 30, 2017
ACCUMULATED OTHER COMPREHENSIVE INCOME [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	The table below summarizes the components of accumulated other comprehensive income (loss) (AOCI), net of tax provision/(benefit), for the years ended September 30, 2017, 2016, and 2015. Foreign Currency Translation Cash Flow Hedges Pension and Other Postretirement Liabilities Total Balance at September 30, 2014 $ 10,115 $ - $ (860 ) $ 9,255 Foreign currency translation adjustment, net of tax of $(1,731) (14,126 ) - - (14,126 ) Unrealized gain (loss) on cash flow hedges: Change in fair value, net of tax of $(833) - (1,511 ) - (1,511 ) Reclassification adjustment into earnings, net of tax of $336 - 610 - 610 Change in pension and other postretirement, net of tax of $0 - - (318 ) (318 ) Balance at September 30, 2015 (4,011 ) (901 ) (1,178 ) (6,090 ) Foreign currency translation adjustment, net of tax of $1,854 15,996 - - 15,996 Unrealized gain (loss) on cash flow hedges: Change in fair value, net of tax of $(274) - (499 ) - (499 ) Reclassification adjustment into earnings, net of tax of $321 - 583 - 583 Change in pension and other postretirement, net of tax of $(584) - - (434 ) (434 ) Balance at September 30, 2016 11,985 (817 ) (1,612 ) 9,556 Foreign currency translation adjustment, net of tax of $(2,321) (6,746 ) 0 - (6,746 ) Unrealized gain (loss) on cash flow hedges: Change in fair value, net of tax of $(660) - 1,161 - 1,161 Reclassification adjustment into earnings, net of tax of $170 - (298 ) - (298 ) Change in pension and other postretirement, net of tax of $79 - - 276 276 Balance at September 30, 2017 $ 5,239 $ 46 $ (1,336 ) $ 3,949

SHARE-BASED COMPENSATION PLANS

SHARE-BASED COMPENSATION PLANS (Tables)	12 Months Ended
	Sep. 30, 2017
SHARE-BASED COMPENSATION PLANS [Abstract]
Schedule of Fair Value Assumptions and Methodology	The fair value of our share-based awards, as shown below, was estimated using the Black-Scholes model with the following weighted-average assumptions, excluding the effect of our leveraged recapitalization: Year Ended September 30, 2017 2016 2015 Stock Options Weighted-average grant date fair value $ 16.50 $ 14.47 $ 16.99 Expected term (in years) 6.57 6.56 6.30 Expected volatility 27 % 26 % 33 % Risk-free rate of return 2.1 % 1.9 % 1.9 % Dividend yield 1.2 % 0.3 % - Year Ended September 30, 2017 2016 2015 ESPP Weighted-average grant date fair value $ 12.49 $ 9.57 $ 10.17 Expected term (in years) 0.50 0.50 0.50 Expected volatility 24 % 24 % 24 % Risk-free rate of return 0.6 % 0.4 % 0.1 % Dividend yield 1.3 % 0.5 % -
Share Based Compensation Expense	Total share-based compensation expense for the years ended September 30, 2017, 2016 and 2015, is as follows: Year Ended September 30, Income statement classifications: 2017 2016 2015 Cost of goods sold $ 2,229 $ 2,105 $ 1,912 Research, development and technical 1,792 1,633 1,596 Selling and marketing 1,380 1,618 1,075 General and administrative 7,603 8,585 11,862 Tax benefit (4,339 ) (4,341 ) (5,511 ) Total share-based compensation expense, net of tax $ 8,665 $ 9,600 $ 10,934
Summary of Stock Option Activity	STOCK OPTION ACTIVITY A summary of stock option activity under the EIP and OIP as of September 30, 2017, and changes during fiscal 2017 are presented below: Stock Options Weighted Average Exercise Price Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Outstanding at September 30, 2016 2,052,552 $ 36.97 Granted 369,230 60.99 Exercised (818,640 ) 33.79 Forfeited or canceled (86,081 ) 43.38 Outstanding at September 30, 2017 1,517,061 $ 44.17 7.0 $ 54,251 Exercisable at September 30, 2017 726,897 $ 36.34 5.5 $ 31,687 Expected to vest after September 30, 2017 788,676 $ 51.36 8.3 $ 22,535
Summary of Restricted Stock Awards and Restricted Stock Unit Awards	A summary of the status of the restricted stock awards and restricted stock unit awards outstanding that were granted under the EIP and OIP as of September 30, 2017, and changes during fiscal 2017, are presented below: Restricted Stock Awards and Units Weighted Average Grant Date Fair Value Nonvested at September 30, 2016 340,460 $ 43.13 Granted 193,761 61.75 Vested (154,526 ) 44.64 Forfeited (33,182 ) 47.76 Nonvested at September 30, 2017 346,513 $ 52.43

OTHER INCOME, NET (Tables)

OTHER INCOME, NET (Tables)	12 Months Ended
	Sep. 30, 2017
OTHER INCOME, NET [Abstract]
Other Income, Net	Other income, net, consisted of the following: Year Ended September 30, 2017 2016 2015 Interest income $ 2,351 $ 949 $ 365 Other income (expense) (438 ) (296 ) 316 Total other income, net $ 1,913 $ 653 $ 681

STOCKHOLDERS EQUITY (Tables)

STOCKHOLDERS EQUITY (Tables)	12 Months Ended
	Sep. 30, 2017
STOCKHOLDERS EQUITY [Abstract]
Summary of Capital Stock Activity	The following is a summary of our capital stock activity over the past three years: Number of Shares Common Stock Treasury Stock September 30, 2014 31,927,601 8,142,687 Exercise of stock options 1,324,646 Restricted stock under EIP and OIP, net of forfeitures 172,010 Restricted stock under Deposit Share Program, net of forfeitures (811) Common stock under ESPP 65,735 Repurchases of common stock under share repurchase plans 851,245 Repurchases of common stock – other 47,746 September 30, 2015 33,489,181 9,041,678 Exercise of stock options 606,562 Restricted stock under EIP and OIP, net of forfeitures 86,277 Restricted stock under Deposit Share Program, net of forfeitures 1,847 Common stock under ESPP 77,437 Repurchases of common stock under share repurchase plans 636,839 Repurchases of common stock – other 66,125 September 30, 2016 34,261,304 9,744,642 Exercise of stock options 818,640 Restricted stock under EIP and OIP, net of forfeitures 81,047 Restricted stock under Deposit Share Program, net of forfeitures - Common stock under ESPP 69,751 Repurchases of common stock under share repurchase plans 167,809 Repurchases of common stock – other 35,739 September 30, 2017 35,230,742 9,948,190

INCOME TAXES (Tables)

INCOME TAXES (Tables)	12 Months Ended
	Sep. 30, 2017
INCOME TAXES [Abstract]
Schedule of Income Before Income Taxes	Income before income taxes was as follows: Year Ended September 30, 2017 2016 2015 Domestic $ 33,272 $ 7,130 $ 15,305 Foreign 76,100 63,308 55,892 Total $ 109,372 $ 70,438 $ 71,197
Schedule of Taxes on Income by Jurisdiction	Taxes on income consisted of the following: Year Ended September 30, 2017 2016 2015 U.S. federal and state: Current $ 8,606 $ 609 $ 6,496 Deferred 1,550 (1,465 ) 1,791 Total $ 10,156 $ (856 ) $ 8,287 Foreign: Current $ 13,422 $ 11,737 $ 7,686 Deferred (1,158 ) (292 ) (922 ) Total 12,264 11,445 6,764 Total U.S. and foreign $ 22,420 $ 10,589 $ 15,051
Income Tax Rate Reconciliation	The provision for income taxes at our effective tax rate differed from the statutory rate as follows: Year Ended September 30, 2017 2016 2015 Federal statutory rate 35.0% 35.0% 35.0% U.S. benefits from research and experimentation activities (1.0) (3.5) (2.2) State taxes, net of federal effect 0.4 (0.1) 0.6 Foreign income at other than U.S. rates (14.7) (16.9) (21.4) Executive compensation 0.3 0.0 0.6 Share-based compensation 0.1 0.7 0.1 Adjustment of prior amounts 0.0 0.0 1.4 Taiwan Restructuring 0.0 0.0 7.2 Domestic production deduction 0.0 (1.3) (1.3) Other, net 0.4 1.1 1.1 Provision for income taxes 20.5% 15.0% 21.1%
Reconciliation of Gross Unrecognized Tax Benefits	The following table presents the changes in the balance of gross unrecognized tax benefits during the last three fiscal years: Balance September 30, 2014 $ 701 Additions for tax positions relating to the current fiscal year 194 Additions for tax positions relating to prior fiscal years 1,400 Settlements with taxing authorities (522 ) Balance September 30, 2015 1,773 Additions for tax positions relating to the current fiscal year 364 Additions for tax positions relating to prior fiscal years 200 Settlements with taxing authorities (248 ) Balance September 30, 2016 2,089 Additions for tax positions relating to the current fiscal year 381 Additions for tax positions relating to prior fiscal years 44 Lapse of statute of limitations (244 ) Balance September 30, 2017 $ 2,270
Schedule of Significant Components of Deferred Income Tax	Significant components of net deferred tax assets and liabilities were as follows: September 30, 2017 2016 Deferred tax assets: Employee benefits $ 5,307 $ 4,612 Inventory 2,863 3,117 Bad debt reserve 585 615 Share-based compensation expense 6,611 8,262 Credit and other carryforwards 22,663 25,596 Other 1,488 1,487 Valuation allowance (2,271 ) (3,022 ) Total deferred tax assets $ 37,246 $ 40,667 Deferred tax liabilities: Depreciation and amortization $ 14,671 $ 17,374 Translation adjustment 300 2,079 Other 739 542 Total deferred tax liabilities $ 15,710 $ 19,995

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Tables)	12 Months Ended
	Sep. 30, 2017
COMMITMENTS AND CONTINGENCIES [Abstract]
Schedule of Product Warranty Reserve Activity	We maintain a warranty reserve that reflects management's best estimate of the cost to replace product that does not meet our specifications and customers' performance requirements, and costs related to such replacement. The warranty reserve is based upon a historical product replacement rate, adjusted for any specific known conditions or circumstances. Additions and deductions to the warranty reserve are recorded in cost of goods sold. Our warranty reserve requirements changed during fiscal 2017 as follows: Balance as of September 30, 2016 $ 243 Reserve for product warranty during the reporting period 530 Settlement of warranty (526 ) Balance as of September 30, 2017 $ 247
Future Minimum Rental Commitments Under Noncancelable Leases	Fiscal Year Operating 2018 $ 3,052 2019 2,587 2020 1,956 2021 1,392 2022 1,084 Thereafter 4,148 $ 14,219
Estimated Future Benefit Payments	Benefit costs for the combined plans were $1,176 $1,024 and $962 in fiscal years 2017, 2016 and 2015, respectively, consisting primarily of service costs, and were recorded as fringe benefit expense under cost of goods sold and operating expenses in our Consolidated Statement of Income. Estimated future benefit payments are as follows: Fiscal Year Amount 2018 $ 304 2019 336 2020 565 2021 412 2022 717 2023 to 2027 $ 3,451

EARNINGS PER SHARE (Tables)

EARNINGS PER SHARE (Tables)	12 Months Ended
	Sep. 30, 2017
EARNINGS PER SHARE [Abstract]
Earnings Per Share	The standards of accounting for earnings per share require companies to provide a reconciliation of the numerator and denominator of the basic and diluted earnings per share computations. Basic and diluted earnings per share were calculated as follows: Year Ended September 30, 2017 2016 2015 Numerator: Net income $ 86,952 $ 59,849 $ 56,146 Less: income attributable to participating securities (256 ) (361 ) (483 ) Net income available to common shareholders $ 86,696 $ 59,488 $ 55,663 Denominator: Weighted-average common shares 25,015,458 24,076,549 24,039,692 (Denominator for basic calculation) Weighted-average effect of dilutive securities: Share-based compensation 497,029 400,444 592,123 Diluted weighted-average common shares 25,512,487 24,476,993 24,631,815 (Denominator for diluted calculation) Earnings per share: Basic $ 3.47 $ 2.47 $ 2.32 Diluted $ 3.40 $ 2.43 $ 2.26

FINANCIAL INFORMATION BY INDU48

FINANCIAL INFORMATION BY INDUSTRY SEGMENT, GEOGRAPHIC AREA AND PRODUCT LINE (Tables)	12 Months Ended
	Sep. 30, 2017
FINANCIAL INFORMATION BY INDUSTRY SEGMENT, GEOGRAPHIC AREA AND PRODUCT LINE [Abstract]
Revenue and Net Property, Plant and Equipment by Customer Location	We operate predominantly in one industry segment – the development, manufacture, and sale of CMP consumables. Revenues are attributed to the United States and foreign regions based upon the customer location and not the geographic location from which our products were shipped. Financial information by geographic area was as follows: Year Ended September 30, 2017 2016 2015 Revenue: United States $ 72,670 $ 62,400 $ 55,989 Asia 394,874 336,312 328,669 Europe 39,635 31,737 29,439 Total $ 507,179 $ 430,449 $ 414,097 Property, plant and equipment, net: United States $ 52,155 $ 50,595 $ 43,239 Asia 54,201 55,893 50,504 Europe 5 8 - Total $ 106,361 $ 106,496 $ 93,743
Revenue by Country Greater than Ten Percent of Total Revenue	The following table shows revenue from sales to customers in foreign countries that accounted for more than ten percent of our total revenue in fiscal 2017, 2016 and 2015: Year Ended September 30, 2017 2016 2015 Revenue: Taiwan $ 130,849 $ 122,671 $ 124,460 South Korea 95,414 76,082 70,608 China 74,781 59,239 49,350
Net Property, Plant and Equipment in Foreign Countries Greater than Ten Percent of Total Net Property, Plant and Equipment	The following table shows net property, plant and equipment in foreign countries that accounted for more than ten percent of our total net property, plant and equipment in fiscal 2017, 2016 and 2015: Year Ended September 30, 2017 2016 2015 Property, plant and equipment, net: Japan $ 21,408 $ 26,268 $ 22,572 South Korea 16,915 11,135 9,658 Taiwan 15,119 17,949 17,419
Schedule of Revenue by Product Line	The following table shows revenue generated by product area in fiscal 2017, 2016 and 2015: Year Ended September 30, 2017 2016 2015 Revenue: Tungsten slurries $ 221,493 $ 185,365 $ 178,770 Dielectric slurries 120,240 99,141 96,386 Polishing Pads 68,673 52,067 32,048 Other Metals slurries 62,829 63,960 71,640 Engineered Surface Finishes 27,900 22,369 21,534 Data storage slurries 6,044 7,547 13,719 Total $ 507,179 $ 430,449 $ 414,097

SELECTED QUARTERLY OPERATING 49

SELECTED QUARTERLY OPERATING RESULTS (Tables)	12 Months Ended
	Sep. 30, 2017
SELECTED QUARTERLY OPERATING RESULTS [Abstract]
Selected Quarterly Operating Results	The following table presents our unaudited financial information for the eight quarterly periods ended September 30, 2017. This unaudited financial information has been prepared in accordance with accounting principles generally accepted in the United States of America, applied on a basis consistent with the annual audited financial statements and in the opinion of management, include all necessary adjustments, which consist only of normal recurring adjustments necessary to present fairly the financial results for the periods. The results for any quarter are not necessarily indicative of results for any future period. CABOT MICROELECTRONICS CORPORATION SELECTED QUARTERLY OPERATING RESULTS (Unaudited and in thousands, except per share amounts) Sept. 30, 2017 June 30, 2017 March 31, 2017 Dec. 31, 2016 Sept. 30, 2016 June 30, 2016 March 31, 2016 Dec. 31, 2015 Revenue $ 136,784 $ 127,957 $ 119,184 $ 123,254 $ 122,684 $ 108,152 $ 99,244 $ 100,369 Cost of goods sold 66,734 65,414 59,153 61,749 61,598 56,127 52,348 50,174 Gross profit 70,050 62,543 60,031 61,505 61,086 52,025 46,896 50,195 Operating expenses: Research, development and technical 13,839 14,333 14,090 13,396 15,842 12,928 14,934 14,828 Selling and marketing 8,680 7,346 7,268 7,552 8,057 6,243 6,668 6,749 General and administrative 14,489 13,953 14,699 12,496 11,454 10,738 12,990 14,263 Total operating expenses 37,008 35,632 36,057 33,444 35,353 29,909 34,592 35,840 Operating income 33,042 26,911 23,974 28,061 25,733 22,116 12,304 14,355 Interest expense 1,127 1,117 1,135 1,150 1,187 1,178 1,191 1,167 Other income (expense), net 798 (115 ) 234 996 257 (246 ) 452 190 Income before income taxes 32,713 25,679 23,073 27,907 24,803 20,692 11,565 13,378 Provision for income taxes 6,211 5,740 4,793 5,676 4,096 1,990 2,434 2,069 Net income $ 26,502 $ 19,939 $ 18,280 $ 22,231 $ 20,707 $ 18,702 $ 9,131 $ 11,309 Basic earnings per share $ 1.05 $ 0.79 $ 0.73 $ 0.90 $ 0.85 $ 0.78 $ 0.38 $ 0.46 Weighted average basic shares outstanding 25,236 25,228 25,031 24,583 24,234 23,929 24,061 24,142 Diluted earnings per share $ 1.03 $ 0.77 $ 0.71 $ 0.88 $ 0.83 $ 0.76 $ 0.37 $ 0.46 Weighted average diluted shares outstanding 25,710 25,721 25,526 25,072 24,678 24,325 24,408 24,549 Dividends per share $ 0.20 $ 0.20 $ 0.20 $ 0.18 $ 0.18 $ 0.18 $ 0.18 $ -

BACKGROUND AND BASIS OF PRESE50

BACKGROUND AND BASIS OF PRESENTATION (Details)	12 Months Ended
	Sep. 30, 2017Segment
BACKGROUND AND BASIS OF PRESENTATION [Abstract]
Number of reportable segments	1

SUMMARY OF SIGNIFICANT ACCOUN51

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) $ in Thousands	12 Months Ended
	Sep. 30, 2017USD ($)Segmentmm	Sep. 30, 2016USD ($)	Sep. 30, 2015USD ($)
ACCOUNTS RECEIVABLE [Abstract]
Accounts receivable, less allowance for doubtful accounts	$ 64,793	$ 62,830
Allowance for doubtful accounts [Roll Forward]
Balance, beginning of period	1,828
Amounts charged to expense	26	588	$ (84)
Deductions and adjustments	(107)
Balance, end of period	$ 1,747	1,828
Goodwill and Intangible Assets [Abstract]
Total number of reporting units | Segment	4
Asset Impairment Charges [Abstract]
Impairment of Long-Lived Assets to be Disposed of	$ 860
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Intangibles impairment Expense		$ 1,000
Intercompany Loan Accounting [Abstract]
Size of polishing tool | mm	300
Minimum [Member]
Goodwill and Intangible Assets [Abstract]
Finite-Lived Intangible Asset, Useful Life	1 year
Maximum [Member]
Goodwill and Intangible Assets [Abstract]
Finite-Lived Intangible Asset, Useful Life	11 years
Buildings [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	15 years
Buildings [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	25 years
Machinery and Equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Machinery and Equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	10 years
Furniture and fixtures [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Furniture and fixtures [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	10 years
Information Systems [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Information Systems [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Accounts Receivable [Member] | Credit Concentration Risk [Member] | Samsung Group (Samsung) [Member]
Concentration Risk [Line Items]
Concentration risk percentage	11.90%	8.30%
Accounts Receivable [Member] | Credit Concentration Risk [Member] | Taiwan Semiconductor Manufacturing Co. (TSMC) [Member]
Concentration Risk [Line Items]
Concentration risk percentage	12.20%	12.90%
Accounts Receivable [Member] | Credit Concentration Risk [Member] | Toshiba Corporation [Member]
Concentration Risk [Line Items]
Concentration risk percentage	3.60%
Accounts Receivable, Net	$ 2,323
Accounts Receivable [Member] | Credit Concentration Risk [Member] | Micron Technology [Member]
Concentration Risk [Line Items]
Concentration risk percentage	10.70%	7.20%
Revenue [Member] | Credit Concentration Risk [Member] | Samsung Group (Samsung) [Member]
Concentration Risk [Line Items]
Concentration risk percentage	16.00%	15.00%	15.00%
Revenue [Member] | Credit Concentration Risk [Member] | Taiwan Semiconductor Manufacturing Co. (TSMC) [Member]
Concentration Risk [Line Items]
Concentration risk percentage	13.00%	15.00%	18.00%
Revenue [Member] | Credit Concentration Risk [Member] | Micron Technology [Member]
Concentration Risk [Line Items]
Concentration risk percentage	10.00%

BUSINESS COMBINATION (Details)

BUSINESS COMBINATION (Details) - USD ($) $ / shares in Units, $ in Thousands	Oct. 22, 2015	Sep. 30, 2016	Mar. 31, 2016	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Business Acquisition [Line Items]
Acquisition of business, net of cash acquired				$ 0	$ 126,976	$ 0
Share-based compensation expense				13,004	13,787	16,445
Fair values of assets acquired and liabilities assumed [Abstract]
Goodwill		$ 100,639		$ 101,932	100,639
Impairment expense					1,000
NexPlanar [Member]
Business Acquisition [Line Items]
Percentage of voting interests acquired	100.00%
Acquisition of business, net of cash acquired	$ 126,976
Cash Acquired from Acquisition	15,261
Purchase price	142,167
Share-based compensation expense					154
Purchase price adjustment			$ 70
Fair values of assets acquired and liabilities assumed [Abstract]
Total purchase consideration	142,237
Cash	15,261
Accounts receivable	3,052
Inventories	2,768
Prepaid expenses and other current assets	1,712
Property, plant and equipment	6,901
Intangible assets	55,000
Deferred tax assets	20,509
Other long-term assets	1,458
Accounts payable	(1,057)
Accrued expenses and other current liabilities	(1,472)
Deferred tax liabilities	(20,313)
Total identifiable net assets	83,819
Goodwill	$ 58,418
Impairment expense		$ 1,000
Weighted average useful life	7 years 8 months 12 days
Business acquisition, pro forma information [Abstract]
Revenues					431,856	437,326
Net income					$ 60,620	$ 46,928
Earnings per share - basic (in dollars per share)					$ 2.50	$ 1.93
Earnings per share - diluted (in dollars per share)					$ 2.46	$ 1.89
Acquired Finite-Lived Intangible Assets [Line Items]
Fair value	$ 55,000
NexPlanar [Member] | Trade Name [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Fair value	$ 8,000
Useful life	7 years
NexPlanar [Member] | Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Fair value	$ 8,000
Useful life	11 years
NexPlanar [Member] | Developed Technology - Product Family A [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Fair value	$ 32,000
Useful life	7 years
NexPlanar [Member] | Developed Technology - Product Family B [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Fair value	$ 2,000
Useful life	9 years
NexPlanar [Member] | In-process Technology [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Fair value	$ 5,000

FAIR VALUE OF FINANCIAL INSTR53

FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) - Recurring [Member] - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016
Assets [Abstract]
Cash and cash equivalents	$ 397,890	$ 287,479
Other long-term investments	929	1,028
Derivative financial instruments	263	28
Total Assets	399,082	288,535
Liabilities [Abstract]
Derivative financial instruments	1,881	1,469
Total liabilities	1,881	1,469
Level 1 [Member]
Assets [Abstract]
Cash and cash equivalents	397,890	287,479
Other long-term investments	929	1,028
Derivative financial instruments	0	0
Total Assets	398,819	288,507
Liabilities [Abstract]
Derivative financial instruments	0	0
Total liabilities	0	0
Level 2 [Member]
Assets [Abstract]
Cash and cash equivalents	0	0
Other long-term investments	0	0
Derivative financial instruments	263	28
Total Assets	263	28
Liabilities [Abstract]
Derivative financial instruments	1,881	1,469
Total liabilities	1,881	1,469
Level 3 [Member]
Assets [Abstract]
Cash and cash equivalents	0	0
Other long-term investments	0	0
Derivative financial instruments	0	0
Total Assets	0	0
Liabilities [Abstract]
Derivative financial instruments	0	0
Total liabilities	$ 0	$ 0

INVENTORIES (Details)

INVENTORIES (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016
INVENTORIES [Abstract]
Raw materials	$ 36,415	$ 45,109
Work in process	7,365	4,668
Finished goods	28,093	22,346
Total	$ 71,873	$ 72,123

PROPERTY, PLANT AND EQUIPMENT55

PROPERTY, PLANT AND EQUIPMENT (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 359,486	$ 360,163
Less: accumulated depreciation and amortization of assets under capital leases	(253,125)	(253,667)
Net property, plant and equipment	106,361	106,496	$ 93,743
Depreciation expense, including amortization of assets recorded under capital leases	17,195	16,915	16,060
Impairment expense	860
Gain (Loss) on Disposition of Property Plant Equipment	1,820	(103)	$ 28
Land [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	17,823	18,636
Buildings [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	104,057	100,084
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	187,649	198,870
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	6,770	6,642
Information Systems [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	32,748	29,573
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 10,439	$ 6,358

GOODWILL AND OTHER INTANGIBLE56

GOODWILL AND OTHER INTANGIBLE ASSETS (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Goodwill [Roll Forward]
Goodwill	$ 101,932	$ 100,639
Goodwill, Other Increase (Decrease)	146
Foreign exchange fluctuation	1,147
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount subject to amortization	81,336	80,914
Accumulated Amortization	43,816	35,628
Indefinite-lived Intangible Assets [Line Items]
Total other intangible assets not subject to amortization	5,190	5,190
Total other intangible assets	86,526	86,104
Other intangible assets [Abstract]
Amortization expense	7,795	8,176	$ 2,346
Estimated future amortization expense [Abstract]
2,018	7,118
2,019	6,675
2,020	6,670
2,021	6,664
2,022	6,664
Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill)		1,000
In-process Technology [Member]
Indefinite-lived Intangible Assets [Line Items]
Total other intangible assets not subject to amortization	4,000	4,000
Other Indefinite-lived Intangibles [Member]
Indefinite-lived Intangible Assets [Line Items]
Total other intangible assets not subject to amortization	1,190	1,190
Product Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount subject to amortization	42,287	42,194
Accumulated Amortization	17,604	12,718
Acquired Patents and Licenses [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount subject to amortization	8,270	8,270
Accumulated Amortization	8,241	8,155
Trade Secrets and Know How [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount subject to amortization	2,550	2,550
Accumulated Amortization	2,550	2,550
Customer relationships, distribution rights and Other [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount subject to amortization	28,229	27,900
Accumulated Amortization	$ 15,421	$ 12,205

OTHER LONG-TERM ASSETS (Details

OTHER LONG-TERM ASSETS (Details) $ in Thousands	12 Months Ended
	Sep. 30, 2017USD ($)Security	Sep. 30, 2016USD ($)	Jun. 30, 2015USD ($)
Other long-term assets [Abstract]
Auction rate securities (ARS)	$ 5,319	$ 5,494
Long-term contract asset	2,115	3,055
Other long-term assets	2,154	2,465
Other long-term investments	929	1,028
Total	$ 10,517	12,042
Number of tax exempt municipal debt securities | Security	2
Minimum maturity period of municipal debt securities	10 years
Fair value of auction rate securities	$ 4,884
Gross unrecognized loss of ARS	435
Long-term liability, SERP investments	$ 929
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Long-term contract asset face amount			$ 4,500
Accounting Standards Update 2015-03 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Debt Issuance Costs, Noncurrent, Net		$ (435)

ACCRUED EXPENSES, INCOME TAXE58

ACCRUED EXPENSES, INCOME TAXES PAYABLE AND OTHER CURRENT LIABILITIES (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016
ACCRUED EXPENSES, INCOME TAXES PAYABLE AND OTHER CURRENT LIABILITIES [Abstract]
Accrued compensation	$ 35,332	$ 17,856
Dividends Payable	5,314	4,502
Raw materials received, not yet invoiced	2,172	2,648
Deferred revenue and customer advances	1,559	782
Warranty accrual	247	243
Income taxes payable	9,717	7,878
Taxes, other than income taxes	1,688	775
Current portion of long-term contract liability	1,500	1,500
Other	5,122	5,211
Total	$ 62,651	$ 41,395

DEBT (Details)

DEBT (Details) - USD ($) $ in Thousands	Jun. 27, 2014	Jun. 26, 2014	Sep. 30, 2017	Sep. 30, 2016	Feb. 13, 2012
Debt Instrument [Line Items]
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net			$ 441	$ 696
Current portion of long-term debt			10,938	7,656
Credit Agreement [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, borrowing capacity			$ 100,000
Maturity date of credit facility			Jun. 27, 2019
Credit Agreement [Member] | Term Loan [Member]
Debt Instrument [Line Items]
Face amount of debt		$ 157,500			$ 175,000
Fair value of debt			$ 144,376
Amended Credit Agreement [Member]
Debt Instrument [Line Items]
Interest rate description			Borrowings under the amended Credit Facilities (other than in respect of swing-line loans) bear interest at a rate per annum equal to the “Applicable Rate” (as defined below) plus, at our option, either (1) a LIBOR rate determined by reference to the cost of funds for deposits in the relevant currency for the interest period relevant to such borrowing or (2) the “Base Rate”, which is the highest of (x) the prime rate of Bank of America, N.A., (y) the federal funds rate plus 1/2 of 1.00% and (z) the one-month LIBOR rate plus 1.00%. The current Applicable Rate for borrowings under the Credit Facilities is 1.50%, as amended, with respect to LIBOR borrowings and 0.25% with respect to Base Rate borrowings, with such Applicable Rate subject to adjustment based on our consolidated leverage ratio. Swing-line loans bear interest at the Base Rate plus the Applicable Rate for Base Rate loans under the Revolving Credit Facility.
Covenant terms			The Credit Agreement contains covenants that restrict the ability of the Company and its subsidiaries to take certain actions, including, among other things and subject to certain significant exceptions: creating liens, incurring indebtedness, making investments, engaging in mergers, selling property, paying dividends or amending organizational documents. The Credit Agreement requires us to comply with certain financial ratio maintenance covenants. These include a maximum consolidated leverage ratio of 2.75 to 1.00 and a minimum consolidated fixed charge coverage ratio of 1.25 to 1.00 for the period January 1, 2016 through the expiration of the Credit Agreement. As of September 30, 2017, our consolidated leverage ratio was 0.91 to 1.00 and our consolidated fixed charge coverage ratio was 3.41 to 1.00. The Credit Agreement also contains customary affirmative covenants and events of default. We believe we are in compliance with these covenants.
Consolidated leverage ratio			0.91
Consolidated fixed charge coverage ratio			3.41
Amended Credit Agreement [Member] | Minimum [Member]
Debt Instrument [Line Items]
Consolidated fixed charge coverage ratio			1.25
Amended Credit Agreement [Member] | Maximum [Member]
Debt Instrument [Line Items]
Consolidated leverage ratio			2.75
Amended Credit Agreement [Member] | Federal Funds Rate [Member]
Debt Instrument [Line Items]
Basis spread on variable rate			0.50%
Amended Credit Agreement [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Basis spread on variable rate			1.00%
Current applicable rate			1.50%
Amended Credit Agreement [Member] | Base Rate [Member]
Debt Instrument [Line Items]
Current applicable rate			0.25%
Amended Credit Agreement [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, borrowing capacity		$ 75,000
Maturity date of credit facility		Feb. 13, 2017
Interest rate description			In addition to paying interest on outstanding principal under the Credit Agreement, we pay a commitment fee to the lenders under the Revolving Credit Facility in respect of the unutilized commitments thereunder. As amended, the fee ranges from 0.20% to 0.30%, based on our consolidated leverage ratio.
Amended Credit Agreement [Member] | Revolving Credit Facility [Member] | Minimum [Member]
Debt Instrument [Line Items]
Commitment fee percentage			0.20%
Amended Credit Agreement [Member] | Revolving Credit Facility [Member] | Maximum [Member]
Debt Instrument [Line Items]
Commitment fee percentage			0.30%
Amended Credit Agreement [Member] | Term Loan [Member]
Debt Instrument [Line Items]
Face amount of debt	$ 175,000
Increase in loan commitments	17,500
Amount drawn from increase in loan commitments	$ 17,500
Long-term Debt, by Maturity [Abstract]
2,018			$ 10,938
2,019			133,438
Long Term Debt			$ 144,376
Accounting Standards Update 2015-03 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Debt Issuance Costs, Current, Net				(261)
Debt Issuance Costs, Noncurrent, Net				$ (435)

DERIVATIVE FINANCIAL INSTRUME60

DERIVATIVE FINANCIAL INSTRUMENTS (Details) ₩ in Thousands, $ in Thousands	12 Months Ended
	Sep. 30, 2017USD ($)	Sep. 30, 2017KRW (₩)	Sep. 30, 2016USD ($)	Dec. 31, 2014USD ($)
Derivative [Line Items]
Derivative Instruments in Hedges, at Fair Value, Net	$ 1,442
Unrealized gain	46
Reclassified from accumulated other comprehensive income into interest expense	$ 31
Reclassification period	12 months
Foreign Exchange Contract [Member] | Buy [Member]
Derivative [Line Items]
Derivative, Notional Amount	$ 8,176		$ 8,858
Foreign Exchange Contract [Member] | Sell [Member]
Derivative [Line Items]
Derivative, Notional Amount	24,295		$ 15,635
Interest Rate Swap [Member]
Derivative [Line Items]
Outstanding variable rate debt				$ 86,406
Interest Rate Swap [Member] | Buy [Member]
Derivative [Line Items]
Derivative, Notional Amount	$ 72,188
Net Investment Hedging [Member]
Derivative [Line Items]
Derivative, Notional Amount | ₩		₩ 100,000,000

DERIVATIVE FINANCIAL INSTRUME61

DERIVATIVE FINANCIAL INSTRUMENTS, Schedule of Fair Value of Derivative Instruments in the Consolidated Balance Sheet (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016
Not Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member] | Prepaid Expenses and Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Fair value of foreign exchange contract asset derivatives	$ 146	$ 28
Fair value of foreign exchange contract liability derivatives	0	0
Not Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member] | Accrued Expenses and Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Fair value of foreign exchange contract asset derivatives	0	0
Fair value of foreign exchange contract liability derivatives	408	202
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Accrued Expenses and Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Fair value of foreign exchange contract asset derivatives	0	0
Fair value of foreign exchange contract liability derivatives	31	612
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Other Noncurrent Assets [Member]
Derivatives, Fair Value [Line Items]
Fair value of foreign exchange contract asset derivatives	117	0
Fair value of foreign exchange contract liability derivatives	0	0
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Other Long-term Liabilities [Member]
Derivatives, Fair Value [Line Items]
Fair value of foreign exchange contract asset derivatives	0	0
Fair value of foreign exchange contract liability derivatives	0	655
Designated as Hedging Instrument [Member] | Net Investment Hedge [Member] | Other Long-term Liabilities [Member]
Derivatives, Fair Value [Line Items]
Fair value of foreign exchange contract asset derivatives	0	0
Fair value of foreign exchange contract liability derivatives	$ 1,442	$ 0

DERIVATIVE FINANCIAL INSTRUME62

DERIVATIVE FINANCIAL INSTRUMENTS, Schedule of the Effect of Derivative Instruments on the Consolidated Statement of Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Not Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member] | Other Income (Expense), Net [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Other income (expense), net	$ (1,462)	$ 676	$ (1,674)

DERIVATIVE FINANCIAL INSTRUME63

DERIVATIVE FINANCIAL INSTRUMENTS, Schedule of Net Investment Hedges in Accumulated Other Comprehensive Income (Details) $ in Thousands	12 Months Ended
	Sep. 30, 2017USD ($)
DERIVATIVE FINANCIAL INSTRUMENTS [Abstract]
Loss on net investment hedge	$ 1,442
Derivatives used in Net Investment Hedge, Tax Expense (Benefit)	(522)
Loss on net investment hedge, net of tax	$ 920

ACCUMULATED OTHER COMPREHENSI64

ACCUMULATED OTHER COMPREHENSIVE INCOME (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Components of Accumulated Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period	$ 497,648	$ 428,964	$ 372,002
Foreign currency translation adjustments	(6,746)	15,996	(14,126)	$ (14,126)
Change in fair value, net of tax	1,161	(499)	(1,511)
Reclassifications adjustment into earnings, net of tax	(298)	583	610
Change in pension and other postretirement liabilities, net of tax of $0	276	(434)	(318)	(318)
Balance, end of period	595,037	497,648	428,964	372,002
Other Comprehensive Income (Loss), Tax [Abstract]
Foreign currency translation adjustment, tax	2,321	1,854	(1,731)
Change in pension and other postretirement, tax	79	(584)	0
Change in fair value, tax	(660)	(274)	(833)
Reclassification adjustment into earnings, tax	170	321	336
Accumulated Other Comprehensive Income [Member]
Components of Accumulated Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period	9,556	(6,090)	9,255
Foreign currency translation adjustments	(6,746)	15,996	(14,126)
Change in pension and other postretirement liabilities, net of tax of $0	276	(434)	(318)
Balance, end of period	3,949	9,556	(6,090)	9,255
Foreign Currency Translation Adjustment [Member]
Components of Accumulated Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period	11,985	(4,011)	10,115
Foreign currency translation adjustments	(6,746)	15,996	(14,126)
Change in fair value, net of tax	0	0	0
Reclassifications adjustment into earnings, net of tax	0	0	0
Change in pension and other postretirement liabilities, net of tax of $0	0	0	0
Balance, end of period	5,239	11,985	(4,011)	10,115
Cash Flow Hedges [Member]
Components of Accumulated Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period	(817)	(901)	0
Foreign currency translation adjustments	0	0	0
Change in fair value, net of tax	1,161	(499)	(1,511)
Reclassifications adjustment into earnings, net of tax	(298)	583	610
Change in pension and other postretirement liabilities, net of tax of $0	0	0	0
Balance, end of period	46	(817)	(901)	0
Pension and Other Postretirement Liabilities [Member]
Components of Accumulated Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period	(1,612)	(1,178)	(860)
Foreign currency translation adjustments	0		0
Change in fair value, net of tax	0	0	0
Reclassifications adjustment into earnings, net of tax	0	0	0
Change in pension and other postretirement liabilities, net of tax of $0	276	(434)	(318)
Balance, end of period	$ (1,336)	$ (1,612)	$ (1,178)	$ (860)

SHARE-BASED COMPENSATION PLAN65

SHARE-BASED COMPENSATION PLANS (Details) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017USD ($)	Sep. 30, 2017USD ($)Awards$ / sharesshares	Sep. 30, 2016USD ($)$ / sharesshares	Sep. 30, 2015USD ($)$ / sharesshares	Sep. 29, 2017$ / shares	Mar. 31, 2016Employee	Dec. 31, 2014USD ($)	Mar. 31, 2008shares	Feb. 29, 2008shares
Omnibus Incentive Plan [Abstract]
Number of equity incentive awards | Awards		6
Number of shares authorized for issuance (in shares) | shares		4,934,444
Number of shares authorized under newly issued plan (in shares) | shares		2,901,360
Number of shares available under previously existing plan (in shares) | shares		2,033,084
Share based compensation expense		$ 13,004	$ 13,787	$ 16,445
Employee stock purchase plan [Abstract]
Number of shares issued, employee stock ownership plan (in shares) | shares		69,751	77,437	65,735
Stock Options Activity [Roll Forward]
Exercised (in shares) | shares		(818,640)	(606,562)	(1,324,646)
Weighted Average Grant Date Fair Value [Roll Forward]
Share-based compensation expense		$ 13,004	$ 13,787	$ 16,445
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Tax benefit		(4,339)	(4,341)	(5,511)
Total share-based compensation expense, net of tax		8,665	9,600	10,934
Fair value of unvested equity							$ 5,033
Cost of Goods Sold [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense		2,229	2,105	1,912
Research, Development and technical [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense		1,792	1,633	1,596
Selling and Marketing [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense		1,380	1,618	1,075
General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense		$ 7,603	8,585	11,862
NexPlanar [Member]
Omnibus Incentive Plan [Abstract]
Share based compensation expense			154
Weighted Average Grant Date Fair Value [Roll Forward]
Share-based compensation expense			154
Accelerated share-based compensation expense			492
NexPlanar [Member] | General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense			$ 646
Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Number of non-employee directors who have completed two full terms of service | Employee						2
Fair value of awards for completing minimum full terms of service	$ 377
Vesting period	1 year
Director [Member] | Directors' Deferred Compensation Plan [Member]
Directors' deferred compensation plan [Abstract]
Cumulative number of shares deferred (in shares) | shares		0	16,641
Share based compensation expense		$ 0	$ 42	95
Stock Options [Member]
Omnibus Incentive Plan [Abstract]
Stock based compensation, contractual term		10 years
Stock based compensation, vesting period		4 years
Amount vested in first year for non employee directors		100.00%
Share based compensation expense		$ 5,500	$ 6,767	$ 7,173
Share based compensation arrangements, Fair value assumptions and methodology [Abstract]
Weighted-average grant date fair value (in dollars per share) | $ / shares		$ 16.50	$ 14.47	$ 16.99
Expected term		6 years 6 months 25 days	6 years 6 months 22 days	6 years 3 months 18 days
Expected volatility		27.00%	26.00%	33.00%
Risk-free rate of return		2.10%	1.90%	1.90%
Dividend yield		1.20%	0.30%	0.00%
Stock Options Activity [Roll Forward]
Outstanding, beginning of period (in shares) | shares		2,052,552
Granted (in shares) | shares		369,230
Exercised (in shares) | shares		(818,640)
Forfeited or canceled (in shares) | shares		(86,081)
Outstanding, end of period (in shares) | shares		1,517,061	2,052,552
Exercisable, end of period ( in shares) | shares		726,897
Expected to vest, end of period (in shares) | shares		788,676
Weighted Average Exercise Price [Roll Forward]
Weighted average exercise price, outstanding, beginning of period (in dollars per share) | $ / shares		$ 36.97
Weighted average exercise price, granted (in dollars per share) | $ / shares		60.99
Weighted average exercise price, exercised (in dollars per share) | $ / shares		33.79
Weighted average exercise price, forfeited or canceled (in dollars per share) | $ / shares		43.38
Weighted average exercise price, outstanding, end of period (in dollars per share) | $ / shares		44.17	$ 36.97
Weighted average exercise price, exercisable, end of period (in dollars per share) | $ / shares		36.34
Weighted average exercise price, expected to vest, end of period (in dollars per share) | $ / shares		$ 51.36
Additional Disclosures [Abstract]
Weighted average remaining contractual term, outstanding, end of period (in years)		7 years
Weighted average remaining contractual term, exercisable, end of period (in years)		5 years 6 months
Weighted average remaining contractual term, expected to vest, end of period (in years)		8 years 3 months 18 days
Aggregate intrinsic value, outstanding, end of period		$ 54,251
Aggregate intrinsic value, exercisable, end of period		31,687
Aggregate intrinsic value, expected to vest, end of period		22,535
Closing stock price (in dollars per share) | $ / shares					$ 79.93
Total intrinsic value of options exercised		25,213	$ 12,317	$ 31,546
Cash received from options exercised		27,666	16,623	33,177
Actual tax benefit realized for the tax deductions from options exercised		8,743	4,076	10,569
Total fair value of stock options vested		5,300	7,880	7,005
Total unrecognized share-based compensation expense		$ 8,727
Compensation cost, weighted-average period for recognition (in years)		2 years 3 months 18 days
Weighted Average Grant Date Fair Value [Roll Forward]
Share-based compensation expense		$ 5,500	6,767	7,173
Restricted Stock [Member]
Omnibus Incentive Plan [Abstract]
Stock based compensation, vesting period		4 years
Amount vested in first year for non employee directors		100.00%
Share based compensation expense		$ 6,730	$ 6,369	8,491
Additional Disclosures [Abstract]
Total unrecognized share-based compensation expense		$ 13,058
Compensation cost, weighted-average period for recognition (in years)		2 years 7 months 6 days
Restricted stock and restricted stock awards units [Roll Forward]
Restricted stocks awards and units, nonvested, beginning of period (in shares) | shares		340,460
Restricted stocks awards and units, granted (in shares) | shares		193,761
Restricted stocks awards and units, vested (in shares) | shares		(154,526)
Restricted stocks awards and units, forfeited (in shares) | shares		(33,182)
Restricted stocks awards and units, nonvested, end of period (in shares) | shares		346,513	340,460
Weighted Average Grant Date Fair Value [Roll Forward]
Weighted average grant date fair value, nonvested, beginning of period (in dollars per share) | $ / shares		$ 43.13
Weighted average grant date fair value, granted (in dollars per share) | $ / shares		61.75
Weighted average grant date fair value, vested (in dollars per share) | $ / shares		44.64
Weighted average grant date fair value, forfeited (in dollars per share) | $ / shares		47.76
Weighted average grant date fair value, nonvested, end of period (in dollars per share) | $ / shares		$ 52.43	$ 43.13
Total fair values of restricted stock awards and restricted stock units vested		$ 6,898	$ 10,740	7,222
Share-based compensation expense		$ 6,730	6,369	8,491
Other than Options or SARs [Member]
Omnibus Incentive Plan [Abstract]
Number of shares authorized other than options or SARS (in shares) | shares		2,030,952
Incentive Stock Options [Member]
Omnibus Incentive Plan [Abstract]
Number of shares authorized for incentive stock options (in shares) | shares		2,538,690
Deposit Share Plan [Member]
Omnibus Incentive Plan [Abstract]
Stock based compensation, vesting period		3 years
Deposit share plan match in restricted shares		50.00%
Employee Stock Purchase Plan [Member]
Omnibus Incentive Plan [Abstract]
Number of shares authorized for issuance (in shares) | shares		435,400						975,000	475,000
Share based compensation expense		$ 774	$ 763	$ 686
Employee stock purchase plan [Abstract]
Percentage annual earnings withheld to purchase stock, maximum		10.00%
Maximum discounted stock purchase price		85.00%
Number of shares issued, employee stock ownership plan (in shares) | shares		69,751	77,437	65,735
Share based compensation arrangements, Fair value assumptions and methodology [Abstract]
Weighted-average grant date fair value - ESPP (in dollars per share) | $ / shares		$ 12.49	$ 9.57	$ 10.17
Expected term		6 months	6 months	6 months
Expected volatility		24.00%	24.00%	24.00%
Risk-free rate of return		0.60%	0.40%	0.10%
Dividend yield		1.30%	0.50%	0.00%
Weighted Average Grant Date Fair Value [Roll Forward]
Share-based compensation expense		$ 774	$ 763	$ 686

SAVINGS PLAN (Details)

SAVINGS PLAN (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
SAVINGS PLAN [Abstract]
Maximum participants' contributions as a percentage of their eligible compensation	60.00%
Company's matching contribution on participants' first four percent contribution	100.00%
Company's matching contribution on participants' contributions over four percent	50.00%
Percentage of participant's contribution subject to company's one hundred percent matching contribution	4.00%
Percentage of participant's contribution subject to company's fifty percent matching contribution	2.00%
401(k) Plan expense	$ 5,256	$ 4,624	$ 4,111
Percentage of company's contribution vested at the time of contribution	100.00%

OTHER INCOME, NET (Details)

OTHER INCOME, NET (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
OTHER INCOME, NET [Abstract]
Interest income									$ 2,351	$ 949	$ 365
Other income (expense)									(438)	(296)	316
Total other income, net	$ 798	$ (115)	$ 234	$ 996	$ 257	$ (246)	$ 452	$ 190	$ 1,913	$ 653	$ 681

STOCKHOLDERS EQUITY (Details)

STOCKHOLDERS EQUITY (Details) $ in Thousands	12 Months Ended
	Sep. 30, 2017USD ($)Voteshares	Sep. 30, 2016USD ($)shares	Sep. 30, 2015USD ($)shares	Jan. 07, 2016USD ($)
Capital Stock Activity [Rollforward]
Beginning Balance (in shares)	34,261,304	33,489,181	31,927,601
Exercise of stock options (in shares)	818,640	606,562	1,324,646
Restricted stock under EIP, net of forfeitures (in shares)	81,047	86,277	172,010
Restricted stock under Deposit Share Plan, net of forfeitures (in shares)	0	1,847	(811)
Common stock under ESPP (in shares)	69,751	77,437	65,735
Ending Balance (in shares)	35,230,742	34,261,304	33,489,181
Treasury Stock [Abstract]
Beginning Balance (in shares)	9,744,642	9,041,678	8,142,687
Repurchases of common stock under share repurchase plans (in shares)	167,809	636,839	851,245
Repurchases of common stock - other (in shares)	35,739	66,125	47,746
Ending Balance (in shares)	9,948,190	9,744,642	9,041,678
Number of votes each common stockholder is entitled to on matter submitted to a vote of stockholders | Vote	1
Number of authorized shares of common stock (in shares)	200,000,000	200,000,000
Share repurchase program, value of shares remaining to be repurchased | $	$ 121,993
Cost of shares repurchased | $	12,035	$ 25,980	$ 40,026
Share Repurchase Program [Member]
Treasury Stock [Abstract]
Share repurchase program, value of shares authorized to be repurchased | $	$ 150,000
Prior Repurchase Program [Member]
Treasury Stock [Abstract]
Share repurchase program, value of shares authorized to be repurchased | $				$ 75,000

INCOME TAXES (Details)

INCOME TAXES (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Income Before Income Taxes [Abstract]
Domestic									$ 33,272	$ 7,130	$ 15,305
Foreign									76,100	63,308	55,892
Income before income taxes	$ 32,713	$ 25,679	$ 23,073	$ 27,907	$ 24,803	$ 20,692	$ 11,565	$ 13,378	109,372	70,438	71,197
U.S. federal and state [Abstract]
Current									8,606	609	6,496
Deferred									1,550	(1,465)	1,791
Total									10,156	(856)	8,287
Foreign [Abstract]
Current									13,422	11,737	7,686
Deferred									(1,158)	(292)	(922)
Total									12,264	11,445	6,764
Total U.S. and foreign	6,211	$ 5,740	$ 4,793	5,676	4,096	$ 1,990	$ 2,434	2,069	$ 22,420	$ 10,589	$ 15,051
Effective income tax rate reconciliation [Abstract]
Federal statutory rate									35.00%	35.00%	35.00%
U.S. benefits from research and experimentation activities									(1.00%)	(3.50%)	(2.20%)
State taxes, net of federal effect									0.40%	(0.10%)	0.60%
Foreign income at other than U.S. rates									(14.70%)	(16.90%)	(21.40%)
Executive compensation									0.30%	0.00%	0.60%
Share-based compensation									0.10%	0.70%	0.10%
Adjustment of prior amounts									0.00%	0.00%	1.40%
Taiwan Restructuring									0.00%	0.00%	7.20%
Domestic production deduction									(0.00%)	(1.30%)	(1.30%)
Other, net									0.40%	1.10%	1.10%
Provision for income taxes									20.50%	15.00%	21.10%
Undistributed earnings of foreign subsidiaries	254,800								$ 254,800
Undistributed earnings of foreign subsidiaries	49,000								49,000
Tax benefit for additional domestic production deductions										$ 928
Reconciliation of gross unrecognized tax benefits [Roll Forward]
Beginning balance				$ 2,089				$ 1,773	2,089	1,773	$ 701
Additions for tax positions relating to the current fiscal year									381	364	194
Additions for tax positions relating to prior fiscal years									44	200	1,400
Settlements with taxing authorities										(248)	(522)
Lapse of statute of limitations									(244)
Ending balance	2,270				2,089				2,270	2,089	1,773
Accrued interest and penalties on uncertain tax positions	100				65				100	65
Deferred tax assets [Abstract]
Employee benefits	5,307				4,612				5,307	4,612
Inventory	2,863				3,117				2,863	3,117
Bad debt reserve	585				615				585	615
Deferred Tax share-based compensation expense	6,611				8,262				6,611	8,262
Credit and other carryforwards	22,663				25,596				22,663	25,596
Other	1,488				1,487				1,488	1,487
Valuation allowance	(2,271)				(3,022)				(2,271)	(3,022)
Total deferred tax assets	37,246				40,667				37,246	40,667
Deferred tax liabilities [Abstract]
Depreciation and amortization	14,671				17,374				14,671	17,374
Translation adjustment	300				2,079				300	2,079
Other	739				542				739	542
Total deferred tax liabilities	$ 15,710				$ 19,995				$ 15,710	$ 19,995
Carryforwards [Line Items]
Operating loss carryforwards expiration dates									fiscal year 2018 and fiscal year 2037
Tax credit carryforward expiration dates									fiscal years 2028 through 2038
Foreign income tax adjustment											$ 868
Diluted earnings per share effect of foreign income tax adjustment (in dollars per share)											$ 0.04
Income Tax Holiday [Line Items]
Former tax holiday percentage	0.00%				0.00%				0.00%	0.00%	0.00%
Tax Holiday approximate diluted earning per share benefit (in dollars per share)									$ 0.20	$ 0.15	$ 0.22
Capital Loss Carryforward [Member]
Carryforwards [Line Items]
Tax credit carryforward, amount	$ 2,772								$ 2,772
Tax credit carryforward, valuation allowance	2,772								$ 2,772
Internal Revenue Service (IRS) [Member]
Income Tax Examination [Line Items]
Tax periods open to examination by taxing authorities									fiscal years 2014 through 2017
Carryforwards [Line Items]
Net operating loss carryforwards	26,075								$ 26,075
Tax credit carryforward, amount					$ 3,765					$ 3,765
State and Local Jurisdiction [Member]
Income Tax Examination [Line Items]
Tax periods open to examination by taxing authorities									fiscal years 2013 through 2017
Carryforwards [Line Items]
Net operating loss carryforwards	35,999								$ 35,999
Tax credit carryforward, amount	1,577								1,577
Tax credit carryforward, valuation allowance	1,409								$ 1,409
Foreign Country [Member]
Income Tax Examination [Line Items]
Tax periods open to examination by taxing authorities									fiscal years 2012 through 2017
Carryforwards [Line Items]
Net operating loss carryforwards	5,642								$ 5,642
Operating loss carryforwards, valuation allowance	$ 1,039								$ 1,039
Tax credit carryforward, amount					$ 4,811					4,811
Foreign Country [Member] | South Korea [Member]
Income Tax Holiday [Line Items]
Percentage of local statutory rate in effect for 2016	50.00%								50.00%
Percentage of local statutory rate in effect for 2017	50.00%								50.00%
Approximate tax provision reduction as a result in the tax holiday									$ 5,018	$ 3,771	$ 5,446

COMMITMENTS AND CONTINGENCIES70

COMMITMENTS AND CONTINGENCIES (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Movement in standard product warranty accrual [Roll Forward]
Balance as of beginning of period	$ 243
Reserve for product warranty during the reporting period	530
Settlement of warranty	(526)
Balance as of end of period	$ 247	$ 243
Lease commitments [Abstract]
Expiration of cancelable and noncancelable leases, maximum	5 years
Rent expense under operating leases	$ 3,120	2,765	$ 2,195
Operating leases, future minimum payments due:
2,018	3,052
2,019	2,587
2,020	1,956
2,021	1,392
2,022	1,084
Thereafter	4,148
Operating leases, total	14,219
Purchase obligations [Abstract]
Purchase obligation, due in 2018	1,500
Purchase obligation, due in 2019	1,500
Purchase obligation	2,933
Current Portion Long Term Contract Liability	1,500	1,500
Long-term contract liability	1,433
Contractual obligation	9,749
Defined Benefit Plan Disclosure [Line Items]
Total period pension cost	1,176	1,024	$ 962
Defined Benefit Plan, Expected Future Benefit Payments, Fiscal Year Maturity [Abstract]
2,018	304
2,019	336
2,020	565
2,021	412
2,022	717
2023 to 2027	3,451
Postretirement Benefits Plan [Member] | Japan [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	6,673	7,091
Accumulated benefit obligation	$ 5,253	$ 5,827
Weighted average discount rate	0.50%	0.25%
Expected rate of compensation increase	2.50%	2.00%
Pension costs in accumulated other comprehensive income	$ 1,837	$ 1,667
Postretirement Benefits Plan [Member] | South Korea [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit obligation	$ 1,663	$ 1,822
Weighted average discount rate	4.00%	3.00%
Expected rate of compensation increase	4.50%	5.00%
Pension costs in accumulated other comprehensive income	$ 6	$ 530

EARNINGS PER SHARE (Details)

EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Numerator [Abstract]
Net income	$ 26,502	$ 19,939	$ 18,280	$ 22,231	$ 20,707	$ 18,702	$ 9,131	$ 11,309	$ 86,952	$ 59,849	$ 56,146
Less: income attributable to participating securities									(256)	(361)	(483)
Net income available to common shareholders									$ 86,696	$ 59,488	$ 55,663
Denominator[Abstract]
Weighted-average common shares (Denominator for basic calculation, in shares)	25,236,000	25,228,000	25,031,000	24,583,000	24,234,000	23,929,000	24,061,000	24,142,000	25,015,458	24,076,549	24,039,692
Weighted-average effect of dilutive securities [Abstract]
Share-based compensation (in shares)									497,029	400,444	592,123
Diluted-weighted average common shares (Denominator for diluted calculation, in shares)	25,710,000	25,721,000	25,526,000	25,072,000	24,678,000	24,325,000	24,408,000	24,549,000	25,512,487	24,476,993	24,631,815
Earnings per share [Abstract]
Basic (in dollars per share)	$ 1.05	$ 0.79	$ 0.73	$ 0.90	$ 0.85	$ 0.78	$ 0.38	$ 0.46	$ 3.47	$ 2.47	$ 2.32
Diluted (in dollars per share)	$ 1.03	$ 0.77	$ 0.71	$ 0.88	$ 0.83	$ 0.76	$ 0.37	$ 0.46	$ 3.40	$ 2.43	$ 2.26
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding stock options excluded from diluted earnings (in shares)									400,000	1,100,000	700,000

FINANCIAL INFORMATION BY INDU72

FINANCIAL INFORMATION BY INDUSTRY SEGMENT, GEOGRAPHIC AREA AND PRODUCT LINE (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2017USD ($)	Jun. 30, 2017USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Sep. 30, 2016USD ($)	Jun. 30, 2016USD ($)	Mar. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Sep. 30, 2017USD ($)Segment	Sep. 30, 2016USD ($)	Sep. 30, 2015USD ($)
FINANCIAL INFORMATION BY INDUSTRY SEGMENT, GEOGRAPHIC AREA AND PRODUCT LINE [Abstract]
Number of segment | Segment									1
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 136,784	$ 127,957	$ 119,184	$ 123,254	$ 122,684	$ 108,152	$ 99,244	$ 100,369	$ 507,179	$ 430,449	$ 414,097
Property, plant and equipment, net	106,361				106,496				106,361	106,496	93,743
United States [Member] | Reportable Geographical Components [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									72,670	62,400	55,989
Property, plant and equipment, net	52,155				50,595				52,155	50,595	43,239
Asia [Member] | Reportable Geographical Components [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									394,874	336,312	328,669
Property, plant and equipment, net	54,201				55,893				54,201	55,893	50,504
Europe [Member] | Reportable Geographical Components [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									39,635	31,737	29,439
Property, plant and equipment, net	$ 5				$ 8				$ 5	$ 8	$ 0

FINANCIAL INFORMATION BY INDU73

FINANCIAL INFORMATION BY INDUSTRY SEGMENT, GEOGRAPHIC AREA AND PRODUCT LINE, REVENUE BY MAJOR CUSTOMERS (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Taiwan [Member]
Revenue, Major Customer [Line Items]
Revenue	$ 130,849	$ 122,671	$ 124,460
South Korea [Member]
Revenue, Major Customer [Line Items]
Revenue	95,414	76,082	70,608
China [Member]
Revenue, Major Customer [Line Items]
Revenue	$ 74,781	$ 59,239	$ 49,350

FINANCIAL INFORMATION BY INDU74

FINANCIAL INFORMATION BY INDUSTRY SEGMENT, GEOGRAPHIC AREA AND PRODUCT LINE, LONG-LIVED ASSETS BY MAJOR CUSTOMERS (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Japan [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net	$ 21,408	$ 26,268	$ 22,572
South Korea [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net	16,915	11,135	9,658
Taiwan [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net	$ 15,119	$ 17,949	$ 17,419

FINANCIAL INFORMATION BY INDU75

FINANCIAL INFORMATION BY INDUSTRY SEGMENT, GEOGRAPHIC AREA AND PRODUCT LINE, SEGMENT REPORTING INFORMATION BY PRODUCT TYPE (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Revenue from External Customer [Line Items]
Revenue	$ 136,784	$ 127,957	$ 119,184	$ 123,254	$ 122,684	$ 108,152	$ 99,244	$ 100,369	$ 507,179	$ 430,449	$ 414,097
Tungsten Slurries [Member]
Revenue from External Customer [Line Items]
Revenue									221,493	185,365	178,770
Dielectric Slurries [Member]
Revenue from External Customer [Line Items]
Revenue									120,240	99,141	96,386
Polishing Pads [Member]
Revenue from External Customer [Line Items]
Revenue									68,673	52,067	32,048
Other Metals Slurries [Member]
Revenue from External Customer [Line Items]
Revenue									62,829	63,960	71,640
Engineered Surface Finishes [Member]
Revenue from External Customer [Line Items]
Revenue									27,900	22,369	21,534
Data Storage Slurries [Member]
Revenue from External Customer [Line Items]
Revenue									$ 6,044	$ 7,547	$ 13,719

SELECTED QUARTERLY OPERATING 76

SELECTED QUARTERLY OPERATING RESULTS (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
SELECTED QUARTERLY OPERATING RESULTS [Abstract]
Revenue	$ 136,784	$ 127,957	$ 119,184	$ 123,254	$ 122,684	$ 108,152	$ 99,244	$ 100,369	$ 507,179	$ 430,449	$ 414,097
Cost of goods sold	66,734	65,414	59,153	61,749	61,598	56,127	52,348	50,174	253,050	220,247	201,866
Gross profit	70,050	62,543	60,031	61,505	61,086	52,025	46,896	50,195	254,129	210,202	212,231
Operating expenses:
Research, development and technical	13,839	14,333	14,090	13,396	15,842	12,928	14,934	14,828	55,658	58,532	59,778
Selling and marketing	8,680	7,346	7,268	7,552	8,057	6,243	6,668	6,749	30,846	27,717	24,983
General and administrative	14,489	13,953	14,699	12,496	11,454	10,738	12,990	14,263	55,637	49,445	52,430
Total operating expenses	37,008	35,632	36,057	33,444	35,353	29,909	34,592	35,840	142,141	135,694	137,191
Operating income	33,042	26,911	23,974	28,061	25,733	22,116	12,304	14,355	111,988	74,508	75,040
Interest expense	1,127	1,117	1,135	1,150	1,187	1,178	1,191	1,167	4,529	4,723	4,524
Other income (expense), net	798	(115)	234	996	257	(246)	452	190	1,913	653	681
Income before income taxes	32,713	25,679	23,073	27,907	24,803	20,692	11,565	13,378	109,372	70,438	71,197
Provision for income taxes	6,211	5,740	4,793	5,676	4,096	1,990	2,434	2,069	22,420	10,589	15,051
Net income	$ 26,502	$ 19,939	$ 18,280	$ 22,231	$ 20,707	$ 18,702	$ 9,131	$ 11,309	$ 86,952	$ 59,849	$ 56,146
Basic earnings per share (in dollars per share)	$ 1.05	$ 0.79	$ 0.73	$ 0.90	$ 0.85	$ 0.78	$ 0.38	$ 0.46	$ 3.47	$ 2.47	$ 2.32
Weighted average basic shares outstanding (in shares)	25,236,000	25,228,000	25,031,000	24,583,000	24,234,000	23,929,000	24,061,000	24,142,000	25,015,458	24,076,549	24,039,692
Diluted earnings per share (in dollars per share)	$ 1.03	$ 0.77	$ 0.71	$ 0.88	$ 0.83	$ 0.76	$ 0.37	$ 0.46	$ 3.40	$ 2.43	$ 2.26
Weighted average diluted shares outstanding (in shares)	25,710,000	25,721,000	25,526,000	25,072,000	24,678,000	24,325,000	24,408,000	24,549,000	25,512,487	24,476,993	24,631,815
Dividends per share	$ 0.20	$ 0.20	$ 0.20	$ 0.18	$ 0.18	$ 0.18	$ 0.18	$ 0	$ 0.78	$ 0.54	$ 0

SCHEDULE II-VALUATION AND QUALI

SCHEDULE II-VALUATION AND QUALIFYING ACCOUNTS (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Allowance for Doubtful Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of year	$ 1,828	$ 1,224	$ 1,392
Amounts charged to expenses	26	588	(84)
Deductions and adjustments	(107)	16	(84)
Balance at end of year	1,747	1,828	1,224
Warranty Reserves [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of year	243	209	246
Amounts charged to expenses	530	595	608
Adjustments to pre-existing warranty reserve	0	0	0
Settlement of warranty	(526)	(561)	(645)
Balance at end of year	247	243	209
Valuation Allowance [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of year	3,022	3,079	2,912
Amounts charged to expenses	0	0	167
Deductions and adjustments	(751)	(57)	0
Balance at end of year	$ 2,271	$ 3,022	$ 3,079