Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2018
Summary of Significant Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements include the accounts of Minerals Technologies Inc. (the "Company"), its wholly and majority-owned subsidiaries, as well as variable interest entities for which the Company is the primary beneficiary. All intercompany balances and transactions have been eliminated in consolidation.
Use of Estimates	Use of Estimates The Company employs accounting policies that are in accordance with U.S. generally accepted accounting principles and require management to make estimates and assumptions relating to the reporting of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenue and expenses during the reported period. Significant estimates include those related to revenue recognition, valuation of long-lived assets, goodwill and other intangible assets, pension plan assumptions, income tax, and litigation and environmental liabilities. Actual results could differ from those estimates.
Cash Equivalents and Short-term Investments	Cash Equivalents and Short-term Investments The Company considers all highly liquid investments with original maturities of three months or less to be cash equivalents. Short-term investments consist of financial instruments, mainly bank deposits, with original maturities beyond three months, but less than twelve months. Short-term investments amounted to $3.8 million and $2.7 million at December 31, 2018 and 2017, respectively. There were no unrealized holding gains and losses on the short-term bank investments held at December 31, 2018.
Trade Accounts Receivable	Trade Accounts Receivable Trade accounts receivables are recorded at the invoiced amount and do not bear interest. The allowance for doubtful accounts is the Company's best estimate of the amount of probable credit losses in the Company's existing accounts receivable. The Company determines the allowance based on historical write-off experience and specific allowances for bankrupt customers. The Company also analyzes the collection history and financial condition of its other customers, considering current industry conditions and determines whether an allowance needs to be established. The Company reviews its allowance for doubtful accounts monthly. Past due balances over 90 days based on payment terms are reviewed individually for collectability. Account balances are charged off against the allowance after all means of collection have been exhausted and the potential for recovery is considered remote. The Company does not have any off-balance-sheet credit exposure related to its customers.
Inventories	Inventories Inventories are valued at the lower of cost or market. Cost is determined by the first-in, first-out (FIFO) method. Additionally, items such as idle facility expense, excessive spoilage, freight handling costs, and re-handling costs are recognized as current period charges. The allocation of fixed production overheads to the costs of conversion are based upon the normal capacity of the production facility. Fixed overhead costs associated with idle capacity are expensed as incurred.
Property, Plant and Equipment	Property, Plant and Equipment Property, plant and equipment are recorded at cost. Significant improvements are capitalized, while maintenance and repair expenditures are charged to operations as incurred. The Company capitalizes interest cost as a component of construction in progress. The straight-line method of depreciation is used for substantially all of the assets for financial reporting purposes, except for mining related equipment which uses units-of-production method. The annual rates of depreciation are 3% - 6.67% for buildings, 6.67% - 12.5% for machinery and equipment, 8% - 12.5% for furniture and fixtures and 12.5% - 25% for computer equipment and software-related assets. The estimated useful lives of our PCC production facilities and machinery and equipment pertaining to our natural stone mining and processing plants and our chemical plants are 15 years. Property, plant and equipment are depreciated over their useful lives. Useful lives are based on management's estimates of the period that the assets can generate revenue, which does not necessarily coincide with the remaining term of a customer's contractual obligation to purchase products made using those assets. The Company's sales of PCC are predominantly pursuant to long-term evergreen contracts, initially ten years in length, with paper mills at which the Company operates satellite PCC plants. The terms of many of these agreements have been extended, often in connection with an expansion of the satellite PCC plant. Failure of a PCC customer to renew an agreement or continue to purchase PCC from a Company facility could result in an impairment of assets charge or accelerated depreciation at such facility. Depletion of mineral reserves is determined on a unit-of-extraction basis for financial reporting purposes, based upon proven and probable reserves, and generally on a percentage depletion basis for tax purposes.
Stripping Costs Incurred During Production	Stripping Costs Incurred During Production Stripping costs are those costs incurred for the removal of waste materials for the purpose of accessing ore body that will be produced commercially. Stripping costs incurred during the production phase of a mine are variable costs that are included in the costs of inventory produced during the period that the stripping costs are incurred.
Accounting for the Impairment of Long-Lived Assets	Accounting for the Impairment of Long-Lived Assets Long-lived assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. If events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable, the Company estimates the undiscounted future cash flows (excluding interest), resulting from the use of the asset and its ultimate disposition. If the sum of the undiscounted cash flows (excluding interest) is less than the carrying value, the Company recognizes an impairment loss, measured as the amount by which the carrying value exceeds the fair value of the asset, determined principally using discounted cash flows.
Goodwill and Other Intangible Assets	Goodwill and Other Intangible Assets Goodwill represents the excess of purchase price and related costs over the value assigned to the net tangible and identifiable intangible assets of businesses acquired. Goodwill is not amortized, but instead assessed for impairment. Intangible assets with estimable useful lives are amortized on a straight-line basis over their respective estimated lives to the estimated residual values, and reviewed for impairment. The Company performs a qualitative assessment for each of its reporting units to determine if the two step process for impairment testing is required. If the Company determines that it is more likely than not that the fair value of a reporting unit is less than its carrying amount, the Company would then evaluate the recoverability of goodwill using a two-step impairment test approach at the reporting unit level. In the first step, the fair value for the reporting unit is compared to its book value including goodwill. In the case that the fair value of the reporting unit is less than book value, a second step is performed which compares the fair value of the reporting unit's goodwill to the book value of the goodwill. The fair value for the goodwill is determined based on the difference between the fair values of the reporting unit and the net fair values of the identifiable assets and liabilities of such reporting unit. If the fair value of the goodwill is less than the book value, the difference is recognized as impairment.
Investment in Joint Ventures	Investment in Joint Ventures The Company uses the equity method of accounting to incorporate the results of its investments in companies in which it has significant influence but does not control; and cost method of accounting in companies in which it cannot exercise significant control. The Company records the equity in earnings of its investments in joint ventures on a one-month lag. At December 31, 2018, the book value of the Company’s equity method investments was $17.8 million.
Accounting for Asset Retirement Obligations	Accounting for Asset Retirement Obligations The Company provides for obligations associated with the retirement of long-lived assets and the associated asset retirement costs. The fair value of a liability for an asset retirement obligation is recognized in the period in which it is incurred if a reasonable estimate of fair value can be made. The associated asset retirement costs are capitalized as part of the carrying amount of the long-lived asset. The Company also provides for legal obligations to perform asset retirement activities where timing or methods of settlement are conditional on future events. The Company also records liabilities related to land reclamation as a part of the asset retirement obligations. The Company mines land for various minerals using a surface-mining process that requires the removal of overburden. In many instances, the Company is obligated to restore the land upon completion of the mining activity. As the overburden is removed, the Company recognizes this liability for land reclamation based on the estimated fair value of the obligation. The obligation is adjusted to reflect the passage of time and changes in estimated future cash outflows.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The recorded amounts of cash and cash equivalents, receivables, short-term borrowings, accounts payable, accrued interest, and variable-rate long-term debt approximate fair value because of the short maturity of those instruments or the variable nature of underlying interest rates. Short-term investments are recorded at cost, which approximates fair market value.
Derivative Financial Instruments	Derivative Financial Instruments The Company records derivative financial instruments which are used to hedge certain foreign exchange risk at fair value on the balance sheet. See Note 11 for a full description of the Company's hedging activities and related accounting policies.
Revenue Recognition	Revenue Recognition Revenue is recognized at the point in time when the customer obtains control of the promised goods or services in an amount that reflects the consideration we expect to receive in exchange for those goods or services. The Company's revenues are primarily derived from the sale of products. Our primary performance obligation is satisfied upon shipment or delivery to our customer based on written sales terms, which is also when control is transferred. Revenues from sales of equipment are recorded upon completion of installation and transfer of control to the customer. Revenues from services are recorded when the services are performed. In most of our PCC contracts, the price per ton is based upon the total number of tons sold to the customer during the year. Under those contracts, the price billed to the customer for shipments during the year is based on periodic estimates of the total annual volume that will be sold to the customer. Revenues are adjusted at the end of each year to reflect the actual volume sold. There were no significant revenue adjustments in the fourth quarter of 2018 and 2017, respectively. We have consignment arrangements with certain customers in our Refractories segment. Revenues for these transactions are recorded when the consigned products are consumed by the customer. Revenues within our Energy Services segment is service based. Certain contracts within this segment are long-term contracts. Revenue where our performance obligations are satisfied in phases is recognized over time using certain input measures based on the measurement of the value transferred to the customer, including milestones achieved.
Foreign Currency	Foreign Currency The assets and liabilities of the Company's international subsidiaries are translated into U.S. dollars using exchange rates at the respective balance sheet date. The resulting translation adjustments are recorded in accumulated other comprehensive income (loss) in shareholders' equity. Income statement items are generally translated at monthly average exchange rates prevailing during the period. International subsidiaries operating in highly inflationary economies translate non-monetary assets at historical rates, while net monetary assets are translated at current rates, with the resulting translation adjustments included in net income. At December 31, 2018, the Company had no international subsidiaries operating in highly inflationary economies.
Income Taxes	Income Taxes Deferred tax assets and liabilities are recognized for the estimated future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates in effect for the year in which those temporary differences are expected to be recovered or settled. 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. The Company operates in multiple taxing jurisdictions, both within the U.S. and outside the U.S. In certain situations, a taxing authority may challenge positions that the Company has adopted in its income tax filings. The Company regularly assesses its tax position for such transactions and includes reserves for those differences in position. The reserves are utilized or reversed once the statute of limitations has expired or the matter is otherwise resolved. The application of income tax law is inherently complex. Laws and regulations in this area are voluminous and are often ambiguous. As such, we are required to make many subjective assumptions and judgments regarding our income tax exposures. Interpretations of and guidance surrounding income tax laws and regulations change over time. As such, changes in our subjective assumptions and judgments can materially affect amounts recognized in the consolidated balance sheets and statements of operations. The Company's accounting policy is to recognize interest and penalties as part of its provision for income taxes. See Note 7 for additional detail on our uncertain tax positions. The accompanying financial statements do not include a provision for foreign withholding taxes on international subsidiaries' unremitted earnings, which are expected to be permanently reinvested overseas.
Research and Development	Research and Development Research and development costs are expensed as incurred.
Accounting for Stock-Based Compensation	Accounting for Stock-Based Compensation The Company recognizes compensation expense for share-based awards based upon the grant date fair value over the vesting period.
Pension and Post-retirement Benefits	Pension and Post-retirement Benefits The Company has defined benefit pension plans covering the majority of its employees. The benefits are generally based on years of service and an employee's modified career earnings. The Company also provides post-retirement healthcare benefits for the majority of its retirees and employees in the United States. The Company measures the costs of its obligation based on its best estimate. The net periodic costs are recognized as employees render the services necessary to earn the post-retirement benefits.
Environmental	Environmental Expenditures that relate to current operations are expensed or capitalized as appropriate. Expenditures that relate to an existing condition caused by past operations and which do not contribute to current or future revenue generation are expensed. Liabilities are recorded when it is probable the Company will be obligated to pay amounts for environmental site evaluation, remediation or related costs, and such amounts can be reasonably estimated.
Earnings Per Share	Earnings Per Share Basic earnings per share have been computed based upon the weighted average number of common shares outstanding during the period. Diluted earnings per share have been computed based upon the weighted average number of common shares outstanding during the period assuming the issuance of common shares for all potentially dilutive common shares outstanding.
Subsequent Events	Subsequent Events The Company has evaluated for subsequent events through the date of issuance of its financial statements.
Recently Issued Accounting Standards	Recently Issued Accounting Standards Changes to accounting principles generally accepted in the United States of America (U.S. GAAP) are established by the Financial Accounting Standards Board (FASB) in the form of accounting standards updates (ASUs) to the FASB’s Accounting Standards Codification. The Company considers the applicability and impact of all ASUs. ASUs not listed below were assessed and determined to be either not applicable or are expected to have minimal impact on our consolidated financial position and results of operations. Leases In February 2016, the FASB issued ASU 2016-02, “Leases”, which requires lessees to recognize most leases on their balance sheets as lease liabilities with corresponding right-of-use ("ROU") assets. Lessor accounting remains substantially similar to current U.S. GAAP. ASU 2016-02 is effective for public business entities for annual and interim periods in fiscal years beginning after December 15, 2018 with early adoption permitted. ASU 2016-02 mandates a modified retrospective transition method for all entities, applying the new lease standard to all leases existing at the date of initial application. The Company has adopted this new standard effective January 1, 2019 using the effective date as our date of initial application. As such, financial information and required disclosures will not be provided for dates prior to January 1, 2019. The new standard provides a number of optional practical expedients in transition. We have elected the ‘package of practical expedients’, which permits us not to reassess under the new standard our prior conclusions about lease identification, lease classification and initial direct costs. The new standard also provides practical expedients for an entity’s ongoing accounting. We have elected the short-term lease recognition exemption for all leases that qualify. On adoption, we currently expect to recognize additional operating liabilities between $60 million to $65 million with corresponding ROU assets ranging from $50 million to $55 million based on the present value of the remaining lease payments under existing operating leases. The adoption of this standard will not have a material impact on the Company's financial statements. Intangibles – Goodwill and Other In January 2017, the FASB issued ASU 2017-04, "Intangibles-Goodwill and Other: Simplifying the Test for Goodwill Impairment", which no longer requires an entity to perform a hypothetical purchase price allocation to measure goodwill impairment. Instead, goodwill will be measured using the difference between the carrying amount and the fair value of the reporting unit. The standard is effective for the interim and annual periods beginning on or after December 15, 2019, with early adoption permitted. The Company will adopt this standard on January 1, 2020. The adoption of this standard is not expected to have a material impact on the Company's financial statements. Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income In February 2018, the FASB issued ASU 2018-02, "Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income", which allows a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the U.S. Tax Cuts and Jobs Act. The standard is effective for the interim and annual periods beginning after December 15, 2018, with early adoption permitted. We have adopted this standard effective January 1, 2019. The adoption of this standard is not expected to have a material impact on the Company's financial statements. Retirement Benefits In August 2018, the FASB issued ASU 2018-14, "Compensation – Retirement Benefits – Defined Benefit Plans – General: Disclosure Framework – Changes to the Disclosure Requirements for Defined Benefit Plans," which removes disclosures that no longer are considered cost beneficial, clarifies the specific requirements of certain disclosures and adds disclosure requirements identified as relevant. The standard is effective for annual periods beginning after December 15, 2020, with early adoption permitted. The Company will adopt this standard on January 1, 2021. The adoption of this standard is not expected to have a material impact on the Company's financial statements. Fair Value Measurement In August 2018, the FASB issued ASU 2018-13, "Fair Value Measurement: Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement," which eliminates, amends and adds disclosure requirements for fair value measurement. The standard is effective for the interim and annual periods beginning after December 15, 2019, with early adoption permitted. The Company will adopt this standard on January 1, 2020. The adoption of this standard is not expected to have a material impact on the Company's financial statements. Adoption of ASU 2014-09 Revenue from Contracts with Customers On January 1, 2018, the Company adopted the provisions of ASU No. 2014-09, “Revenue from Contracts with Customers”. The underlying principle is that an entity will recognize revenue to depict the transfer of goods or services to customers at an amount that the entity expects to be entitled to in exchange for those goods or services. The standard provides a five-step analysis of transactions to determine when and how revenue is recognized. The standard also requires enhanced disclosures regarding the nature, amount, timing and uncertainty of revenue and cash flows arising from an entity’s contracts with customers. The Company has elected to use the cumulative effect transition method and there has not been a change to our previously reported financial results. Under accounting standards codification (ASC 606), revenue is recognized when a customer obtains control of promised goods or services in an amount that reflects the consideration we expect to receive in exchange for those goods or services. We measure revenue based on the consideration specified in the customer arrangement and revenue is recognized when the performance obligations in the customer arrangement are satisfied. A performance obligation is a promise in a contract to transfer a distinct good or service to the customer. The transaction price of a contract is allocated to each distinct performance obligation and recognized as revenue when or as, the customer receives the benefit of the performance obligation. Customers typically receive the benefit as goods are delivered and services are performed. We utilized a comprehensive approach to assess the impact of the standard on our contract portfolio by reviewing our current accounting policies and practices to identify potential differences that would result from applying the new requirements to our revenue contracts, including evaluation of our performance obligations, principal versus agent considerations and variable consideration. We recognize revenue when our performance obligation is satisfied. See Note 2 to the Consolidated Financial Statements. Adoption of ASU 2017-07 Compensation - Retirement Benefits: Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost On January 1, 2018, the Company adopted the provisions of ASU 2017-07, “Compensation – Retirement Benefits: Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost”, which requires companies to present the service cost component of the net benefit cost in the same line items in which they report compensation cost. All other components of net periodic benefit cost will be presented outside operating income. The provisions have been applied retrospectively for the income statement presentation requirements. Prior to the adoption of the standard, the Company classified all net periodic benefit costs within operating costs, primarily within “Marketing and administrative expenses” on the Consolidated Statements of Income. The line item classification changes required by the standard did not impact the Company’s pre-tax earnings or net income; however, “Income from operations” and “Other non-operating income (deductions), net” changed by immaterial offsetting amounts. As a result of the accounting change, the Company reclassified approximately $1.7 million and $3.0 million from marketing and administrative expenses to other non-operating deductions for the years ended December 31, 2017 and 2016, respectively, to conform to the current year presentation. Adoption of ASU 2017-12 Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities On January 1, 2018, the Company early adopted the provisions of ASU 2017-12, “Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities,” which improves and simplifies existing standard to allow companies to better reflect their risk management activities in the financial statements. The standard expands the ability to hedge nonfinancial and financial risk components, eliminates the requirement to separately measure and recognize hedge ineffectiveness and eases requirements of an entity’s assessment of hedge effectiveness. The adoption of this standard did not have an impact on the Company’s financial statements. Adoption of ASU 2017-01 Business Combinations On January 1, 2018, the Company adopted the provisions of ASU 2017-01, “Business Combinations,” which clarifies the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The definition of a business affects many areas of accounting including acquisitions, disposals, goodwill, and consolidation. The adoption of this new standard did not have an impact on the Company’s financial statements.