Summary of Significant Accounting Policies	12 Months Ended
Dec. 31, 2017
Summary of Significant Accounting Policies	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Nature of Operations Entegris, Inc. (Entegris or the Company) is a leading global developer, manufacturer and supplier of microcontamination control products, specialty chemicals and advanced materials handling solutions for manufacturing processes in the semiconductor and other high-technology industries. Principles of Consolidation The consolidated financial statements include the accounts of the Company and its majority-owned subsidiaries. Intercompany profits, transactions and balances have been eliminated in consolidation. Use of Estimates and Basis of Presentation The preparation of consolidated financial statements in conformity with accounting principles generally accepted in the United States requires management to make judgments, estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. On an ongoing basis, Entegris evaluates its estimates, including those related to receivables, inventories, property, plant and equipment, intangible assets, accrued liabilities, income taxes and share-based compensation, among others. Actual results could differ from those estimates. Cash and Cash Equivalents Cash and cash equivalents include cash on hand and highly liquid debt securities with original maturities of three months or less, which are valued at cost and approximates fair value. Allowance for Doubtful Accounts An allowance for uncollectible trade receivables is estimated based on a combination of write-off history, aging analysis and any specific, known troubled accounts. The Company maintains an allowance for doubtful accounts that management believes is adequate to cover expected losses on trade receivables. Inventories Inventories are stated at the lower of cost and net realizable value. Cost is determined by the first-in, first-out (FIFO) method. Property, Plant, and Equipment Property, plant and equipment are carried at cost and are depreciated on the straight-line method over the estimated useful lives of the assets. When assets are retired or disposed of, the cost and related accumulated depreciation are removed from the accounts, and gains or losses are recognized in the same period. Maintenance and repairs are expensed as incurred, while significant additions and improvements are capitalized. Long-lived assets, including property, plant and equipment, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset or group of assets may not be recoverable based on estimated future undiscounted cash flows. The amount of impairment, if any, is measured as the difference between the net book value and the estimated fair value of the asset(s). Investments The Company’s nonmarketable investments are accounted for under either the cost or equity method of accounting, as appropriate. All nonmarketable investments are periodically reviewed to determine whether declines, if any, in fair value below cost basis are other-than-temporary. If the decline in fair value is determined to be other-than-temporary, an impairment loss is recorded and the investment is written down to a new cost basis. Fair Value of Financial Instruments The carrying value of cash equivalents, accounts receivable, accounts payable, accrued payroll and related benefits, and other accrued liabilities approximates fair value due to the short maturity of those instruments. The fair value of long-term debt, including current maturities, based upon models utilizing market observable (Level 2) inputs and credit risk, was $686 million at December 31, 2017 compared to the carrying amount of long-term debt, including current maturities, of $674 million. Goodwill and Intangible Assets Goodwill represents the excess of acquisition costs over the fair value of the net assets of businesses acquired. Goodwill is not subject to amortization, but is tested for impairment annually at August 31, the Company's annual testing date, and whenever events or changes in circumstances indicate that impairment may have occurred. The Company compares the carrying value of its reporting units, including goodwill, to their fair value. For reporting units in which the assessment indicates that it is more likely than not that the fair value is more than its carrying value, goodwill is not considered impaired. If the carrying value of the reporting unit exceeds fair value, goodwill is considered impaired. Based on its annual analysis, the Company determined there was no indication of impairment of goodwill and the estimated fair value of each reporting unit substantially exceeded its carrying value. Amortizable intangible assets include, among other items, patented, unpatented and other developed technology and customer-based intangibles, and are amortized using the straight-line method over their respective estimated useful lives. The Company reviews intangible assets, along with other long-lived assets - primarily property, plant and equipment - for impairment if changes in circumstances or the occurrence of events suggest the remaining value may not be recoverable. Derivative Financial Instruments The Company records derivatives as assets or liabilities on the balance sheet and measures such instruments at fair value. Changes in fair value of derivatives are recorded each period in the Company’s consolidated statements of operations. The Company periodically enters into forward foreign currency contracts to reduce exposures relating to rate changes in certain foreign currencies. Certain exposures to credit losses related to counterparty nonperformance exist. However, the Company does not anticipate nonperformance by the counterparties since they are large, well-established financial institutions. None of these derivatives is accounted for as a hedge transaction. Accordingly, changes in the fair value of forward foreign currency contracts are recorded as other (income) expense, net, in the Company’s consolidated statements of operations. The fair values of the Company’s derivative financial instruments are based on prices quoted by financial institutions for these instruments. Foreign Currency Translation Assets and liabilities of certain foreign subsidiaries are translated from foreign currencies into U.S. dollars at period-end exchange rates, and the resulting gains and losses arising from translation of net assets located outside the U.S. are recorded as a cumulative translation adjustment, a component of accumulated other comprehensive loss in the consolidated balance sheets. Income statement amounts are translated at the weighted average exchange rates for the year. Translation adjustments are not adjusted for income taxes, as substantially all translation adjustments relate to permanent investments in non-U.S. subsidiaries. Gains and losses resulting from foreign currency transactions are included in other (income) expense, net, in the Company's consolidated statements of operations. Revenue Recognition Revenue and the related cost of sales are generally recognized upon shipment of the products. Revenue for product sales is recognized upon delivery, when persuasive evidence of an arrangement exists, when title and risk of loss have been transferred to the customer, collectability is reasonably assured, and pricing is fixed or determinable. Shipping and handling fees related to sales transactions are billed to customers and are recorded as revenue. The Company sells its products throughout the world primarily to companies in the microelectronics industry. The Company performs continuing credit evaluations of its customers and generally does not require collateral. Letters of credit may be required from its customers in certain circumstances. The Company provides for estimated returns based on historical and current trends in both sales and product returns. The Company collects various sales and value-added taxes on certain product and service sales that are accounted for on a net basis. Shipping and Handling Costs Shipping and handling costs incurred are recorded in cost of sales in the Company's consolidated statements of operations. Engineering, Research and Development Expenses Engineering, research and development costs are expensed as incurred. Share-based Compensation The Company measures the cost of employee services received in exchange for the award of equity instruments based on the fair value of the award at the date of grant. Compensation expense is recognized using the straight-line attribution method to recognize share-based compensation over the service period of the award, with adjustments recorded for forfeitures as they occur. Income Taxes The Company accounts for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, deferred tax assets and liabilities are determined on the basis of the differences between the financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income tax expense in the period that includes the enactment date. The Company recognizes deferred tax assets to the extent that it believes these assets are more likely than not to be realized. A valuation allowance is recorded to reduce deferred tax assets when it is more likely than not that the Company would not be able to realize all or part of its deferred tax assets. In making such a determination, the Company considers all available positive and negative evidence, including future reversals of existing temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations. If the Company determines that it would be able to realize its deferred tax assets in the future in excess of their net recorded amount, the Company would make an adjustment to the deferred tax asset valuation allowance, which would reduce the provision for income taxes. The Company’s policy for recording interest and penalties associated with audits and unrecognized tax benefits is to record such items as a component of income before taxes. Penalties and interest to be paid or received are recorded in other expense (income), net, in the statement of operations. Comprehensive Income (Loss) Comprehensive income (loss) represents the change in equity resulting from items other than shareholder investments and distributions. The Company’s foreign currency translation adjustments, unrealized gains and losses on available-for-sale investments, and minimum pension liability adjustments are included in accumulated other comprehensive loss. Comprehensive income (loss) and the components of accumulated other comprehensive loss are presented in the accompanying consolidated statements of comprehensive income (loss) and consolidated statements of equity. Recent Accounting Pronouncements Adopted in 2017 In April 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2016-09, Compensation - Stock Compensation (Topic 718), which simplifies several aspects of the accounting for employee share-based payment transactions, including the accounting for tax effects related to share-based payments, forfeitures, and statutory tax withholding requirements, as well as the classification of tax-related cash flows in the statement of cash flows. The update eliminates the accounting for excess tax benefits to be recognized in additional paid-in capital and tax deficiencies recognized either in the income tax provision or in additional paid-in capital. ASU No. 2016-09 became effective for the Company on January 1, 2017. The Company adopted ASU No. 2016-09 using the modified retrospective approach. In connection with the adoption of ASU No. 2016-09, the Company elected as an accounting policy to record forfeitures as they occur and recorded a cumulative-effect adjustment of $0.4 million to retained earnings as of January 1, 2017. The Company also recorded a cumulative-effect adjustment of $1.0 million to retained earnings as of January 1, 2017 with respect to previously unrecognized excess tax benefits. Under ASU No. 2016-09, excess tax benefits or deficiencies related to stock option exercises and restricted stock unit vesting are recognized in the consolidated statement of operations. Accordingly, for the twelve months ended December 31, 2017, the Company recorded a tax benefit of $3.6 million in the consolidated statement of operations. Also related to the adoption of ASU No. 2016-09, the Company elected to present the cash flow statement using the prospective transition method. No prior periods have been adjusted. Recent Accounting Pronouncements Yet to be Adopted In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606). ASU No. 2014-09 outlines a new, single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most current revenue recognition guidance. Under ASU No. 2014-09, revenue for the Company’s contracts will be recognized when control of the products or services transfers to the customer at an amount that reflects the consideration the Company expects to receive in exchange for those goods or services, which is generally consistent with the revenue recognition model currently used for the Company's contracts. ASU No. 2014-09 provides a five-step analysis for determining when and how revenue is recognized. The Company performed and completed a review of its revenue streams as compared to its current accounting policies for customer contracts in 2017. The Company designed and implemented specific controls over its evaluation of the impact of ASU No. 2014-09, including its calculation of the cumulative effect of adopting the standard. As a result of its evaluation, the Company also identified changes to and modified certain of its accounting policies and practices. Although there were no significant changes to its accounting systems or controls upon adoption, the Company modified certain of its existing controls to incorporate the revisions made to its accounting policies and practices. The Company adopted ASU No. 2014-09 on January 1, 2018 on a modified retrospective basis and has concluded that the adoption of this ASU did not have a material impact on the Company’s consolidated financial statements and its internal controls over financial reporting. The Company recorded a cumulative adjustment that decreased retained earnings by approximately $0.7 million reflecting the cumulative impact of changes to revenue recognition related to certain customer incentive arrangements and to product deliveries using certain shipping terms made upon adoption of ASU No. 2014-09. ASU No. 2014-09 also requires disclosures sufficient to enable users to understand the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers, including qualitative and quantitative disclosures about contracts with customers. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842). ASU No. 2016-02 requires the identification of arrangements that should be accounted for as leases by lessees. In general, for lease arrangements exceeding a twelve-month term, these arrangements must now be recognized as assets and liabilities on the balance sheet of the lessee. Under ASU No. 2016-02, a right-of-use asset and lease obligation will be recorded for all leases, whether operating or financing, while the income statement will reflect lease expense for operating leases, and amortization and interest expense for financing leases. The balance sheet amount recorded for existing leases at the date of adoption of ASU No. 2016-02 must be calculated using the applicable incremental borrowing rate at the date of adoption. ASU No. 2016-02 is effective beginning January 1, 2019. The Company is currently assessing the impact that adopting this new accounting standard will have on its consolidated financial statements and disclosures, and the timing of adoption.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Nature of Operations Entegris, Inc. (Entegris or the Company) is a leading global developer, manufacturer and supplier of microcontamination control products, specialty chemicals and advanced materials handling solutions for manufacturing processes in the semiconductor and other high-technology industries.

Principles of Consolidation The consolidated financial statements include the accounts of the Company and its majority-owned subsidiaries. Intercompany profits, transactions and balances have been eliminated in consolidation.

Use of Estimates and Basis of Presentation The preparation of consolidated financial statements in conformity with accounting principles generally accepted in the United States requires management to make judgments, estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. On an ongoing basis, Entegris evaluates its estimates, including those related to receivables, inventories, property, plant and equipment, intangible assets, accrued liabilities, income taxes and share-based compensation, among others. Actual results could differ from those estimates.

Cash and Cash Equivalents Cash and cash equivalents include cash on hand and highly liquid debt securities with original maturities of three months or less, which are valued at cost and approximates fair value.

Allowance for Doubtful Accounts An allowance for uncollectible trade receivables is estimated based on a combination of write-off history, aging analysis and any specific, known troubled accounts. The Company maintains an allowance for doubtful accounts that management believes is adequate to cover expected losses on trade receivables.

Inventories Inventories are stated at the lower of cost and net realizable value. Cost is determined by the first-in, first-out (FIFO) method.

Property, Plant, and Equipment Property, plant and equipment are carried at cost and are depreciated on the straight-line method over the estimated useful lives of the assets. When assets are retired or disposed of, the cost and related accumulated depreciation are removed from the accounts, and gains or losses are recognized in the same period. Maintenance and repairs are expensed as incurred, while significant additions and improvements are capitalized. Long-lived assets, including property, plant and equipment, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset or group of assets may not be recoverable based on estimated future undiscounted cash flows. The amount of impairment, if any, is measured as the difference between the net book value and the estimated fair value of the asset(s).

Investments The Company’s nonmarketable investments are accounted for under either the cost or equity method of accounting, as appropriate. All nonmarketable investments are periodically reviewed to determine whether declines, if any, in fair value below cost basis are other-than-temporary. If the decline in fair value is determined to be other-than-temporary, an impairment loss is recorded and the investment is written down to a new cost basis.

Fair Value of Financial Instruments The carrying value of cash equivalents, accounts receivable, accounts payable, accrued payroll and related benefits, and other accrued liabilities approximates fair value due to the short maturity of those instruments.

The fair value of long-term debt, including current maturities, based upon models utilizing market observable (Level 2) inputs and credit risk, was $686 million at December 31, 2017 compared to the carrying amount of long-term debt, including current maturities, of $674 million.

Goodwill and Intangible Assets Goodwill represents the excess of acquisition costs over the fair value of the net assets of businesses acquired. Goodwill is not subject to amortization, but is tested for impairment annually at August 31, the Company's annual testing date, and whenever events or changes in circumstances indicate that impairment may have occurred. The Company compares the carrying value of its reporting units, including goodwill, to their fair value. For reporting units in which the assessment indicates that it is more likely than not that the fair value is more than its carrying value, goodwill is not considered impaired. If the carrying value of the reporting unit exceeds fair value, goodwill is considered impaired.

Based on its annual analysis, the Company determined there was no indication of impairment of goodwill and the estimated fair value of each reporting unit substantially exceeded its carrying value.

Amortizable intangible assets include, among other items, patented, unpatented and other developed technology and customer-based intangibles, and are amortized using the straight-line method over their respective estimated useful lives. The Company reviews intangible assets, along with other long-lived assets - primarily property, plant and equipment - for impairment if changes in circumstances or the occurrence of events suggest the remaining value may not be recoverable.

Derivative Financial Instruments The Company records derivatives as assets or liabilities on the balance sheet and measures such instruments at fair value. Changes in fair value of derivatives are recorded each period in the Company’s consolidated statements of operations.

The Company periodically enters into forward foreign currency contracts to reduce exposures relating to rate changes in certain foreign currencies. Certain exposures to credit losses related to counterparty nonperformance exist. However, the Company does not anticipate nonperformance by the counterparties since they are large, well-established financial institutions. None of these derivatives is accounted for as a hedge transaction. Accordingly, changes in the fair value of forward foreign currency contracts are recorded as other (income) expense, net, in the Company’s consolidated statements of operations. The fair values of the Company’s derivative financial instruments are based on prices quoted by financial institutions for these instruments.

Foreign Currency Translation Assets and liabilities of certain foreign subsidiaries are translated from foreign currencies into U.S. dollars at period-end exchange rates, and the resulting gains and losses arising from translation of net assets located outside the U.S. are recorded as a cumulative translation adjustment, a component of accumulated other comprehensive loss in the consolidated balance sheets. Income statement amounts are translated at the weighted average exchange rates for the year. Translation adjustments are not adjusted for income taxes, as substantially all translation adjustments relate to permanent investments in non-U.S. subsidiaries. Gains and losses resulting from foreign currency transactions are included in other (income) expense, net, in the Company's consolidated statements of operations.

Revenue Recognition Revenue and the related cost of sales are generally recognized upon shipment of the products. Revenue for product sales is recognized upon delivery, when persuasive evidence of an arrangement exists, when title and risk of loss have been transferred to the customer, collectability is reasonably assured, and pricing is fixed or determinable. Shipping and handling fees related to sales transactions are billed to customers and are recorded as revenue.

The Company sells its products throughout the world primarily to companies in the microelectronics industry. The Company performs continuing credit evaluations of its customers and generally does not require collateral. Letters of credit may be required from its customers in certain circumstances. The Company provides for estimated returns based on historical and current trends in both sales and product returns.

The Company collects various sales and value-added taxes on certain product and service sales that are accounted for on a net basis.

Shipping and Handling Costs Shipping and handling costs incurred are recorded in cost of sales in the Company's consolidated statements of operations.

Engineering, Research and Development Expenses Engineering, research and development costs are expensed as incurred.

Share-based Compensation The Company measures the cost of employee services received in exchange for the award of equity instruments based on the fair value of the award at the date of grant. Compensation expense is recognized using the straight-line attribution method to recognize share-based compensation over the service period of the award, with adjustments recorded for forfeitures as they occur.

Income Taxes The Company accounts for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, deferred tax assets and liabilities are determined on the basis of the differences between the financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income tax expense in the period that includes the enactment date.

The Company recognizes deferred tax assets to the extent that it believes these assets are more likely than not to be realized. A valuation allowance is recorded to reduce deferred tax assets when it is more likely than not that the Company would not be able to realize all or part of its deferred tax assets. In making such a determination, the Company considers all available positive and negative evidence, including future reversals of existing temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations. If the Company determines that it would be able to realize its deferred tax assets in the future in excess of their net recorded amount, the Company would make an adjustment to the deferred tax asset valuation allowance, which would reduce the provision for income taxes.

The Company’s policy for recording interest and penalties associated with audits and unrecognized tax benefits is to record such items as a component of income before taxes. Penalties and interest to be paid or received are recorded in other expense (income), net, in the statement of operations.

Comprehensive Income (Loss) Comprehensive income (loss) represents the change in equity resulting from items other than shareholder investments and distributions. The Company’s foreign currency translation adjustments, unrealized gains and losses on available-for-sale investments, and minimum pension liability adjustments are included in accumulated other comprehensive loss. Comprehensive income (loss) and the components of accumulated other comprehensive loss are presented in the accompanying consolidated statements of comprehensive income (loss) and consolidated statements of equity.

Recent Accounting Pronouncements Adopted in 2017 In April 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2016-09, Compensation - Stock Compensation (Topic 718), which simplifies several aspects of the accounting for employee share-based payment transactions, including the accounting for tax effects related to share-based payments, forfeitures, and statutory tax withholding requirements, as well as the classification of tax-related cash flows in the statement of cash flows. The update eliminates the accounting for excess tax benefits to be recognized in additional paid-in capital and tax deficiencies recognized either in the income tax provision or in additional paid-in capital. ASU No. 2016-09 became effective for the Company on January 1, 2017. The Company adopted ASU No. 2016-09 using the modified retrospective approach. In connection with the adoption of ASU No. 2016-09, the Company elected as an accounting policy to record forfeitures as they occur and recorded a cumulative-effect adjustment of $0.4 million to retained earnings as of January 1, 2017. The Company also recorded a cumulative-effect adjustment of $1.0 million to retained earnings as of January 1, 2017 with respect to previously unrecognized excess tax benefits. Under ASU No. 2016-09, excess tax benefits or deficiencies related to stock option exercises and restricted stock unit vesting are recognized in the consolidated statement of operations. Accordingly, for the twelve months ended December 31, 2017, the Company recorded a tax benefit of $3.6 million in the consolidated statement of operations. Also related to the adoption of ASU No. 2016-09, the Company elected to present the cash flow statement using the prospective transition method. No prior periods have been adjusted.

Recent Accounting Pronouncements Yet to be Adopted In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606). ASU No. 2014-09 outlines a new, single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most current revenue recognition guidance. Under ASU No. 2014-09, revenue for the Company’s contracts will be recognized when control of the products or services transfers to the customer at an amount that reflects the consideration the Company expects to receive in exchange for those goods or services, which is generally consistent with the revenue recognition model currently used for the Company's contracts. ASU No. 2014-09 provides a five-step analysis for determining when and how revenue is recognized. The Company performed and completed a review of its revenue streams as compared to its current accounting policies for customer contracts in 2017. The Company designed and implemented specific controls over its evaluation of the impact of ASU No. 2014-09, including its calculation of the cumulative effect of adopting the standard. As a result of its evaluation, the Company also identified changes to and modified certain of its accounting policies and practices. Although there were no significant changes to its accounting systems or controls upon adoption, the Company modified certain of its existing controls to incorporate the revisions made to its accounting policies and practices. The Company adopted ASU No. 2014-09 on January 1, 2018 on a modified retrospective basis and has concluded that the adoption of this ASU did not have a material impact on the Company’s consolidated financial statements and its internal controls over financial reporting. The Company recorded a cumulative adjustment that decreased retained earnings by approximately $0.7 million reflecting the cumulative impact of changes to revenue recognition related to certain customer incentive arrangements and to product deliveries using certain shipping terms made upon adoption of ASU No. 2014-09. ASU No. 2014-09 also requires disclosures sufficient to enable users to understand the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers, including qualitative and quantitative disclosures about contracts with customers.

In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842). ASU No. 2016-02 requires the identification of arrangements that should be accounted for as leases by lessees. In general, for lease arrangements exceeding a twelve-month term, these arrangements must now be recognized as assets and liabilities on the balance sheet of the lessee. Under ASU No. 2016-02, a right-of-use asset and lease obligation will be recorded for all leases, whether operating or financing, while the income statement will reflect lease expense for operating leases, and amortization and interest expense for financing leases. The balance sheet amount recorded for existing leases at the date of adoption of ASU No. 2016-02 must be calculated using the applicable incremental borrowing rate at the date of adoption. ASU No. 2016-02 is effective beginning January 1, 2019. The Company is currently assessing the impact that adopting this new accounting standard will have on its consolidated financial statements and disclosures, and the timing of adoption.