XML 65 R29.htm IDEA: XBRL DOCUMENT
v3.20.1

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies) | 12 Months Ended
--- | ---
Dec. 31, 2019
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES. |
Basis of Presentation and Use of Estimates | Basis of Presentation and Use of Estimates: The Company’s consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”). The preparation of the Company’s consolidated financial statements requires the Company to make estimates and assumptions that affect the reported amounts of assets and liabilities and the related disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of expenses during the reporting period. The more significant areas requiring the use of management estimates and assumptions relate to environmental reclamation and closure obligations; asset useful lives utilized for depletion, depreciation, amortization and accretion calculations; fair value of equity investment and asset groups used in impairment testing; recoverable gold in leach pad inventory; current and long-term inventory; mine development capitalization costs; the collectability of value added taxes receivable; fair values of assets and liabilities acquired in business combinations; reserves; valuation allowances for deferred tax assets; income and mining tax provisions and reserves for contingencies and litigation. The Company bases its estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances. Actual results may differ significantly from these estimates. References to “C$” refer to Canadian currency.
Basis of Consolidation | Basis of Consolidation: The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. Intercompany accounts and transactions have been eliminated. Investments over which the Company exerts significant influence but does not control through majority ownership are accounted for using the equity method, as described in Investments, below.
Cash and Cash Equivalents and Restricted Cash | Cash and Cash Equivalents and Restricted Cash: The Company considers cash in banks, deposits in transit, and highly liquid term deposits with original maturities of three months or less to be cash and cash equivalents. Because of the short maturity of these instruments, the carrying amounts approximate their fair value. Restricted cash is excluded from cash and cash equivalents and is included in long-term assets, except for flow-through share proceeds which appear as a separate line under current assets. Proceeds from flow-through shares issued are recorded as restricted cash and remain restricted until utilized to fund exploration activities.
Investments | Investments: The Company accounts for investments over which the Company exerts significant influence but does not control through majority ownership using the equity method of accounting pursuant to ASC Topic 323, Investments – Equity Method and Joint Ventures. Under the equity method, the Company’s investment is initially recognized at cost in the Consolidated Balance Sheet and subsequently increased or decreased to recognize the Company's share of income and losses of the investee, dividends received from the investee and for impairment losses after the initial recognition date. The Company's share of income and losses of the investee and impairment losses are recognized in the Consolidated Statements of Operations and Comprehensive (Loss) Income (“Statement of Operations”) during the period. Refer to Impairment of Long-lived Assets for the Company’s policy on impairment. The Company’s investments in marketable equity securities and warrants are measured at fair value at each period end with changes in fair value recognized in net (loss) income in the Statement of Operations in accordance with ASU 2016-01. The Company adopted ASU 2016-01 prospectively effective January 1, 2018. Previously, the Company had classified the marketable equity securities as available-for-sale securities and recorded them at fair value at each period end based upon quoted market prices with changes in fair value recorded in the Accumulated Other Comprehensive (Loss) Income (“OCI”). Upon the sale of the securities or if there was an other-than-temporary decline in fair value below cost, the gain and losses were transferred from OCI to the Statements of Operations. Upon adoption, unrealized accumulated gains on marketable securities of $3.0 million were transferred from OCI to Accumulated Deficit (see Consolidated Statements of Changes in Shareholders’ Equity).
Value Added Taxes Receivable | Value Added Taxes Receivable: In Mexico and Canada, value added taxes (“VAT” and “HST”, respectively) are assessed on purchases of materials and services and sales of products. Businesses are generally entitled to recover the taxes they have paid related to purchases of materials and services, either as a refund or as a credit against future taxes payable. With the exception of MSC, in Argentina the Company expenses all VAT as their recoverability is uncertain.
Stockpiles, Material on Leach Pads, In-process Inventory, Precious Metals Inventory and Materials and Supplies | Stockpiles, Material on Leach Pads, In-process Inventory, Precious Metals Inventory and Materials and Supplies: Stockpiles, material on leach pads, in-process inventory, precious metals inventory and materials and supplies (collectively, “Inventories”) are accounted for using the weighted average cost method and are carried at the lower of average cost or net realizable value. Net realizable value represents the estimated future sales price of the product based on current and long-term metals prices, less the estimated costs to complete production and bring the product to a saleable form. Write-downs of Inventories resulting from net realizable value impairments are reported as a component of production costs applicable to sales. The current portion of Inventories is determined based on the expected amounts to be processed and/or recovered within the next twelve months, with the remaining portion, if any, classified as long-term. Stockpiles represent mineralized material extracted from the mine and available for processing. Stockpiles are measured by estimating the number of tonnes added and removed from the stockpile, an estimate of the contained metals (based on assay data) and the estimated metallurgical recovery rates. Costs are allocated to stockpiles based on current mining costs incurred including applicable overhead relating to mining operations. Material is removed from the stockpile at an average cost per tonne. Mineralized material on leach pads is the material that is placed on pads where it is treated with a chemical solution that dissolves the gold contained in the mineralized material over a period of time. Costs are attributed to the mineralized material on leach pads based on current mining costs incurred up to the point of placing the ore on the pad. Costs are removed from the leach pad inventory based on the average cost per estimated recoverable ounce of gold on the leach pad as the gold is recovered. The estimates of recoverable gold on the leach pads are calculated from the quantities of mineralized material placed on the leach pads (measured tonnes added to the leach pads), the grade of mineralized material placed on the leach pads (based on assay data) and a recovery percentage. The quantities of recoverable gold placed on the leach pads are reconciled by comparing the grades of ore placed on the pads to the quantities of gold actually recovered (metallurgical balancing), the nature of the leaching process inherently limits the ability to precisely monitor inventory levels. As a result, the metallurgical balancing process is constantly monitored, and the engineering estimates are refined based on actual results over time. In-process inventories represent materials that are currently in the process of being converted to a saleable product. In-process material is measured based on assays of the material from the various stages of processing. Costs are allocated to in-process inventories based on the costs of the material fed into the process attributable to the source material coming from the mines, stockpiles and/or leach pads plus the in-process conversion costs incurred to that point in the process. Precious metal inventories include gold and silver doré and bullion that is unsold and held at the Company’s or the refinery’s facilities. Costs are allocated to precious metal inventories based on costs of the respective in-process inventories incurred prior to the refining process plus applicable refining costs. Materials and supplies inventories are comprised of chemicals, reagents, spare parts and consumable parts used in operating and other activities. Cost includes applicable taxes and freight.
Proven and Probable Reserves | Proven and Probable Reserves: The definition of proven and probable reserves is set forth in Guide 7. Proven reserves are reserves for which (a) quantity is computed from dimensions revealed in outcrops, trenches, workings or drill holes, grade and/or quality are computed from the results of detailed sampling and (b) the sites for inspection, sampling and measurement are spaced so closely and the geological character is so well defined that size, shape, depth and mineral content of the reserves are well-established. Probable reserves are reserves for which quantity and grade and/or quality are computed from information similar to that used for proven (measured) reserves, but the sites for inspection, sampling, and measurement are farther apart or are otherwise less adequately spaced. The degree of assurance, although lower than that for proven (measured) reserves, is high enough to assume continuity between points of observations.
Mineral Property Interests, Plant and Equipment and Mine Development Costs | Mineral Property Interests, Plant and Equipment and Mine Development Costs: Mineral property interests: Mineral property interest represent capitalized expenditures related to the exploration and development of mineral properties and expenditures arising from property acquisitions. The amount capitalized for an acquired mineral property represents its fair value at the time of acquisition, either as an individual asset purchase or as a part of a business combination. Development costs include engineering and metallurgical studies, drilling and other related costs to delineate an ore body, and the removal of overburden to initially expose an ore body at open pit surface mines (“pre-stripping”) and building of access paths and other infrastructure to gain access to the ore body at underground mines. Development costs are charged to net income (loss) in the year incurred as Exploration or Advanced Projects until proven and probable reserves as defined by Guide 7 have been defined, after which they are capitalized. Where multiple open pits exist at a mine, pre-stripping costs are capitalized separately to each pit. Production commences when saleable minerals, beyond a de minimis amount, are produced. During the production phase of a mine, costs incurred that provide access to reserves and resources that will be produced in future periods that would not have otherwise been accessible are capitalized and included in the carrying amount of the related mineral property interest. Drilling and related costs are capitalized for an ore body where proven and probable reserves exist and the activities are directed at obtaining additional information, providing greater definition of the ore body or converting non-reserve mineralization to proven and probable reserves and the benefit is expected to be realized over a period beyond one year. All other drilling and related costs are expensed as incurred as Exploration or Advanced Projects. Exploration costs include costs incurred to identify new mineral resources, evaluate potential resources, and convert mineral resources into proven and probable reserves. However, drilling costs specifically incurred for the purpose of operational ore control during the production stage rather than obtaining additional information on the ore body are expensed and allocated to inventory costs and then included as a component of production costs applicable to sales as the revenue from the sale of inventory occurs. Mineral property interests are amortized upon commencement of production on a unit-of-production basis over proven and probable reserves, as defined by Guide 7. When a property does not contain mineralized material that satisfies the definition of proven and probable reserves, the amortization of the capitalized costs are charged to expense based on the most appropriate method, which includes straight-line method and units-of-production method over the estimated useful life of the mine, as determined by internal mine plans. Plant and Equipment: For properties where the Company established proven and probable reserves as defined by Guide 7, expenditures for plant and equipment and expenditures that extend the useful lives of existing plant and equipment are capitalized and recorded at cost. The cost capitalized for plant and equipment includes borrowing costs incurred that are attributable to qualifying plant and equipment. Plant and equipment are depreciated using the straight-line method over the estimated productive life of the asset. For properties where the Company did not establish proven and probable reserves as defined by Guide 7, substantially all costs, including design, engineering, construction, and installation of equipment are expensed as incurred, unless the equipment have alternative uses or significant salvage value in which case the equipment is capitalized at cost. Construction-in-progress (“CIP”) costs: Assets under construction are capitalized as construction-in-progress until the asset is available for its intended use, at which point costs are transferred to the appropriate category of plant and equipment or mineral property interest and amortized. The cost of construction-in-progress comprises the purchase price of the asset and any costs directly attributable to bringing it into working condition for its intended use.
Impairment of Long-lived Assets | Impairment of Long-Lived Assets: The Company reviews and evaluates its long-lived assets for impairment at a quarterly basis or when events or changes in circumstances indicate that the related carrying amounts may not be recoverable. Once it is determined that impairment exists, an impairment loss is measured as the amount by which the asset carrying value exceeds its fair value. For the purpose of recognition and measurement of impairment, the Company groups its long-lived assets by specific mine or project, as this represents the lowest level for which identifiable cash flows exist. For asset groups where an impairment loss is determined using the undiscounted future net cash flows method or discounted future net cash flows method, future cash flows are estimated based on quantities of recoverable mineralized material, expected gold and silver prices (considering current and historical prices, trends and related factors), production levels, operating costs, capital requirements and reclamation costs, all based on life-of-mine plans. The term “recoverable mineralized material” refers to the estimated amount of gold or other commodities that will be obtained after taking into account losses during processing and treatment. The Company’s estimates of future cash flows are based on numerous assumptions and uncertainties. It is possible that actual future cash flows will be significantly different than the estimates, as actual future quantities of recoverable minerals, gold, silver and other commodity prices, production levels and costs of capital are each subject to significant risks and uncertainties. Currently the resource and reserve estimate at the Gold Bar mine is being evaluated in light of significant differences recently observed between modeled and mined ore tonnage and gold grade from the Gold Pick West Pit. Preliminary iterations suggest that a significant reduction in tonnage, an increase in gold grade, and a resulting significant reduction in contained ounces from the existing reserve estimate is likely. The results of this evaluation will directly impact our estimates of future cash flows, which may affect the value of our long-lived assets. For asset groups where the Company is unable to determine a reliable estimate of future net cash flows, the Company adopts a market approach to estimate fair value by using a combination of observed market value per square mile and observed market value per ounce or pound of mineral material based on comparable transactions.
Asset Retirement Obligation, reclamation and remediation costs | Asset Retirement Obligation (“ARO”), Reclamation and Remediation Costs: Provisions for environmental rehabilitation are made in respect of the estimated future costs of closure and restoration and rehabilitation costs (which include the dismantling and demolition of infrastructure, removal of residual materials and remediation of disturbed areas) in the accounting period when the related environmental disturbance occurs. The associated asset retirement costs, including periodic adjustments, if any, are capitalized as part of the carrying amount of the long- lived asset when proven or probable reserves exist or if they relate to an acquired mineral property interest; otherwise the costs are charged to the Statement of Operations. Periodic accretion is recorded to ARO and charged to operations. The fair value of an ARO is measured by discounting the expected cash flows adjusted for inflation, using a credit-adjusted risk free rate of interest. The Company prepares estimates of the timing and amounts of expected cash flows when an ARO is incurred, which are updated to reflect changes in facts and circumstances. Estimation of the fair value of AROs requires significant judgment, including amount of cash flows, timing of reclamation, inflation rate and credit risk.
Lease Accounting | Lease Accounting: Contracts entered into are analyzed to identify whether the contract contains an operating or financing lease according to ASC 842, adopted by the Company effective January 1, 2019 (see “Recently Adopted Accounting Pronouncements”). If a contract is determined to contain a lease, the Company will include lease payments (the lease liability) and the right-of-use asset (“ROU”) representing the right to the underlying asset for the lease term within the Consolidated Balance Sheets. Lease liabilities are disclosed as a distinct line item within the Consolidated Balance Sheets, whereas, the ROU asset is included in mineral property interests and plant and equipment. Related depreciation and amortization expense and interest expense for finance leases, and rent expense for operating leases is recorded within the Statement of Operations. For leases with a term of twelve months or less, an accounting policy election is made to not recognize lease assets and lease liabilities. The Company has elected to account for non-lease components as part of the lease component to which they relate. Operating and ROU asset balances and lease liabilities are recognized at the commencement date based on the present value of the future lease payments over the lease term. The Company utilizes the incremental borrowing rate (“IBR”) in determining the present value of the future lease payments. IBR represents the rate of interest that a lessee would have to pay to borrow an amount equal to the lease payments on a collateralized basis over a similar term in a similar economic environment. Each lease’s IBR is determined by using the average bond yield ratings for comparable companies.
Revenue Recognition | Revenue Recognition: Revenue consists of proceeds received and expected to be received for the Company’s principal products, gold and silver. Revenue is recognized when title to gold and silver passes to the buyer and when collectability is reasonably assured. Title passes to the buyer based on terms of the sales contract, usually upon delivery of the product. Product pricing is determined under the sales agreements which are referenced against active and freely traded commodity markets, for example, the London Bullion Market for both gold and silver, in an identical form to the product sold. Gold and silver doré produced from the San José mine is sold at the prevailing spot market price based on the London A.M. fix, while concentrates are sold at the prevailing spot market price based on either the London P.M. fix or average of the London A.M. and London P.M. fix depending on the sales contract. Concentrates are provisionally priced, whereby the selling price is subject to final adjustments at the end of a period ranging from 30 to 90 days after delivery to the customer. The final price is based on the market price of the precious metal content at the relevant quotation point stipulated in the contract. Due to the time elapsed between shipment and the final settlement with the buyer, MSC must estimate the prices at which sales of metals will be settled. At the end of each financial reporting period, previously recorded provisional sales are adjusted to estimated settlement metals prices based on relevant forward market prices until final settlement with the buyer. In addition to selling refined bullion at spot, the Company has doré purchase agreements in place with financial institutions and refineries. Under the agreements, the Company has the option to sell approximately 90% of the gold and silver contained in doré bars prior to the completion of refining by the third party refiner. Revenue is recognized when the Company has provided irrevocable instructions to the refiner to transfer to the purchaser the refined ounces sold upon final processing outturn, and when payment of the purchase price for the purchased doré or bullion has been made in full by the purchaser. There is no judgement involved in revenue recognition as revenue is recognized when payment has been made by the purchaser and the product has been delivered.
Foreign Currency | ​ ​ Foreign Currency: The functional currency for the Company’s operations is the U.S. dollar. All monetary assets and liabilities denominated in a currency which is not the U.S. dollar are translated at current exchange rates at each balance sheet date and the resulting adjustments are included in a separate line item under other income (expense). Revenue and expense in foreign currencies are translated at the average exchange rates for the period. ​ Stock-Based Compensation: The Company accounts for stock options at fair value as prescribed in ASC 718. The Company estimates the fair value of each stock option at the grant date by using the Black-Scholes option-pricing model and provides for expense recognition over the service period, if any, of the stock option. The company’s estimates may be impacted by certain variables including, but not limited to, stock price volatility, employee stock option exercise behavior and estimates of forfeitures.
Stock-Based Compensation | ​
Flow-through Shares | Flow-Through Shares: Current Canadian tax legislation permits mining entities to issue flow-through shares to investors by which the deductions for tax purposes related to resource exploration and evaluation expenditures may be claimed by investors instead of the entity, subject to a renouncement process. Under ASC 740, proceeds from the issuance of flow-through shares are allocated first to the common stock based on the underlying quoted price of shares and the residual amount is allocated to the sale of tax benefits, classified as a liability. As the Company incurs qualifying exploration and evaluation expenditures to fulfill its obligation, the liability is drawn down and the sale of tax benefits is recognized in the Statement of Operations as a reduction of deferred tax expense.
Income and Mining Taxes | Income and Mining Taxes: The Company accounts for income and mining taxes under ASC 740 using the liability method, recognizing certain temporary differences between the financial reporting basis of liabilities and assets and the related tax basis for such liabilities and assets. This method generates either a net deferred income and mining tax liability or asset for the Company, as measured by the statutory tax rates in effect. The Company derives the deferred income and mining tax charge or benefit by recording the change in either the net deferred income and mining tax liability or asset balance for the year. The Company records a valuation allowance against any portion of those deferred income and mining tax assets when it believes, based on the weight of available evidence, it is more likely than not that some portion or all of the deferred income and mining tax asset will not be realized.
Comprehensive (Loss) Income | Comprehensive (Loss) Income: In addition to net income or loss, comprehensive income or loss includes all changes in equity during a period.
Per Share Amounts | Per Share Amounts: Basic income or loss per share is computed by dividing income or loss available to common shareholders by the weighted average number of common shares outstanding during the period. Diluted income or loss per share reflects the potential dilution of securities that could share in the earnings of the Company and are computed in accordance with the treasury stock method based on the average number of common shares and dilutive common share equivalents outstanding. Only those instruments that result in a reduction in income per share are included in the calculation of diluted (loss) income per share.
Loans and borrowings | Loans and Borrowings: Borrowings are recognized initially at fair value, net of financing costs incurred, and subsequently measured at amortized cost. Any difference between the amounts originally received and the redemption value of the debt is recognized in the Statements of Operations over the period to maturity using the effective interest method. Borrowing costs directly attributable to the acquisition, construction or production of a qualifying asset (i.e. an asset that necessarily takes a substantial period of time to get ready for its intended use or sale) are capitalized as part of the cost of the asset. All other borrowing costs are expensed in the period they occur.
Fair Value of Financial Instruments | Fair Value of Financial Instruments: Fair value accounting, establishes a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets and liabilities (Level 1 measurements) and the lowest priority to unobservable inputs (Level 3 measurements). The three levels of the fair value hierarchy are described below:
Loans and borrowings: Borrowings are recognized initially at fair value, net of financing costs incurred, and subsequently measured at amortized cost. Any difference between the amounts originally received and the redemption value of the debt is recognized in the Consolidated Statement of Operations and Comprehensive (Loss) Income over the period to maturity using the effective interest method. Fair Value of Financial Instruments: Fair value accounting, as prescribed in ASC Section 820, utilizes a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets and liabilities (Level 1 measurements) and the lowest priority to unobservable inputs (Level 3 measurements). The three levels of the fair value hierarchy are described below: | ​
Level 1 | Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities;
Level 2 | Quoted prices in markets that are not active, or inputs that are observable, either directly or indirectly, for substantially the full term of the asset or liability; and
Level 3 | Prices or valuation techniques that require inputs that are both significant to the fair value measurement and unobservable (supported by little or no market activity).
Recently Adopted And Issued Accounting Pronouncements | Recently Adopted Accounting Pronouncements Leases – ASC 842: From 2016 to 2019, the FASB issued multiple ASUs regarding the new ASC 842. The ASUs outline amendments and updates to ASC 842, which provides that a lessee should recognize the assets and the liabilities that arise from leases, including operating leases. Under the new requirements, a lessee is required to recognize in the statement of financial position a liability to make lease payments (the lease liability) and the right-of-use asset representing the right to the underlying asset for the lease term. Adoption of this ASC was completed by the Company on January 1, 2019 under a modified retrospective transition method with certain practical expedients. The adoption of ASC 842 did not result in significant changes to the financial statements. Practical expedients and elections under ASUs and ASC 842 made by the Company are as follows: ASU 2018-11: This update permitted an entity to elect an optional transitional practical expedient to continue to apply ASC 840, including its disclosure requirements, in the comparative periods presented in the year of adoption of ASC 842. Under this optional practical expedient, the Company applied the transition provisions on January 1, 2019 (the date of adoption) rather than January 1, 2017 (the beginning of the earliest comparative period presented); first reporting under the new standard was for the first quarter of 2019. Upon adoption of ASC 842, the Company recognized a nominal cumulative-effect adjustment to the opening accumulated deficit balance. Package of practical expedients – which permits an entity to (a) not reassess whether expired or existing contracts contain leases, (b) not reassess lease classification for existing or expired leases and (c) not consider whether previously capitalized initial direct costs would be appropriate under the new standard. The Company opted to elect the package of practical expedients. Hindsight practical expedient – which permits an entity to use hindsight in determining the lease term. The Company opted to elect this provision. Easements practical expedient – which permits an entity to elect an optional transitional practical expedient to not evaluate land easements that existed or expired before the entity’s adoption of ASC 842 that were not previously accounted for as leases under ASC 840. The Company opted to elect this transitional provision and as a result did not evaluate any of its land agreements. Short term election – which permits an entity to elect not to apply lease accounting to leases that are not greater than twelve months. The Company elected this short term election. Non-lease component election – which permits lessees to elect to account for non-lease components as part of the lease component to which they relate; an election made by class of underlying asset. The Company opted to make this election. The adoption of ASC 842 resulted in an increase in the Company’s recorded assets and liabilities and a nominal cumulative-effect adjustment to the opening accumulated deficit balance (see N ote 10 Lease Liabilities). Recently Issued Accounting Pronouncements Changes to the Disclosure Requirements for Fair Value Measurement: In August 2018, the FASB issued ASU 2018- 13, “Fair Value Measurement (Topic 820): Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement.” This update modifies the disclosure requirements for fair value measurements by removing, modifying or adding disclosures. ASU 2018-13 is effective for fiscal years beginning after December 15, 2019 and early adoption is permitted. Certain disclosures in the update are applied retrospectively, while others are applied prospectively. The Company is currently evaluating the potential impact of adopting this guidance on its financial statements, however it does not believe that the adoption will have a material impact on the Company’s financial statements or disclosures. Income Taxes: In December 2019, FASB issued ASU 2019-12 “Income Taxes (Topic 740).” ASU 2019-12 simplifies the accounting for income taxes by reducing complexity in accounting standards. The update to the accounting standard is effective for the Company for fiscal years beginning after December 15, 2020, with early adoption permitted. The Company is currently evaluating the effect of this amendment and the impact it may have on the Company’s consolidated financial statements.

X
- Definition Disclosure of accounting policy for issuance of flow-through shares to investors whereby the deductions for tax purposes related to resource exploration and evaluation expenditures may be claimed by investors instead of the entity, subject to a renouncement process. + References No definition available. + Details
Name: | mux_FlowThroughSharesPolicyTextBlock
Namespace Prefix: | mux_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition The entire disclosure represent the information relating to income and Mining . + References No definition available. + Details
Name: | mux_IncomeAndMiningTaxesPolicyTextBlock
Namespace Prefix: | mux_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Disclosure of accounting policy for mineral property interests, plant and equipment and mine development costs. + References No definition available. + Details
Name: | mux_MineralPropertyInterestsPlantAndEquipmentAndMineDevelopmentCostsPolicyTextBlock
Namespace Prefix: | mux_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Disclosure of accounting policy for proven and probable reserves. + References No definition available. + Details
Name: | mux_ProvenAndProbableReservesPolicyTextBlock
Namespace Prefix: | mux_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Disclosure of accounting policy for the ore stockpile inventory, basis of stating ore stockpile inventories (for example, lower of cost or market). If inventory is carried at cost, this disclosure includes the nature of the cost elements included in inventory. Also discloses the current position of the inventory and its classification as short- term or long-term on basis based on expected amounts to be processed within next 12 months. + References No definition available. + Details
Name: | mux_StockpilesMaterialOnLeachPadsInProcessInventoryPreciousMetalsInventoryAndMaterialsAndSuppliesPolicyTextBlock
Namespace Prefix: | mux_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Disclosure of accounting policy for value added taxes. + References No definition available. + Details
Name: | mux_ValueAddedTaxesPolicyTextBlock
Namespace Prefix: | mux_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_AccountingPoliciesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Disclosure of accounting policy for legal obligation associated with retirement of long-lived asset that results from acquisition, construction, or development or from normal operation of long-lived asset, and environmental remediation liability from improper or other-than-normal operation of long-lived asset. Includes, but is not limited to, timing of recognition and whether obligation is measured on discounted basis. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 30 -Section 55 -Paragraph 14 -URI http://asc.fasb.org/extlink&oid=6571209&loc=d3e13669-110860 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=84158767&loc=d3e18780-107790 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 Reference 4: http://www.xbrl.org/2003/role/recommendedDisclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 30 -Section 50 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13231-110859 + Details
Name: | us-gaap_AssetRetirementObligationsAndEnvironmentalCostPolicyTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Disclosure of accounting policy for cash and cash equivalents, including the policy for determining which items are treated as cash equivalents. Other information that may be disclosed includes (1) the nature of any restrictions on the entity's use of its cash and cash equivalents, (2) whether the entity's cash and cash equivalents are insured or expose the entity to credit risk, (3) the classification of any negative balance accounts (overdrafts), and (4) the carrying basis of cash equivalents (for example, at cost) and whether the carrying amount of cash equivalents approximates fair value. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4273-108586 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=84158767&loc=d3e18780-107790 + Details
Name: | us-gaap_CashAndCashEquivalentsPolicyTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Disclosure of accounting policy for comprehensive income. + References No definition available. + Details
Name: | us-gaap_ComprehensiveIncomePolicyPolicyTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Disclosure of accounting policy regarding (1) the principles it follows in consolidating or combining the separate financial statements, including the principles followed in determining the inclusion or exclusion of subsidiaries or other entities in the consolidated or combined financial statements and (2) its treatment of interests (for example, common stock, a partnership interest or other means of exerting influence) in other entities, for example consolidation or use of the equity or cost methods of accounting. The accounting policy may also address the accounting treatment for intercompany accounts and transactions, noncontrolling interest, and the income statement treatment in consolidation for issuances of stock by a subsidiary. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.3A-02) -URI http://asc.fasb.org/extlink&oid=116822174&loc=d3e355033-122828 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section S99 -Paragraph 3 -Subparagraph (SX 210.3A-03) -URI http://asc.fasb.org/extlink&oid=116822174&loc=d3e355100-122828 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=84158767&loc=d3e18780-107790 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=109239629&loc=d3e5614-111684 + Details
Name: | us-gaap_ConsolidationPolicyTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Disclosure of accounting policy related to debt. Includes, but is not limited to, debt issuance costs, the effects of refinancings, method of amortizing debt issuance costs and original issue discount, and classifications of debt. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=84158767&loc=d3e18780-107790 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601 + Details
Name: | us-gaap_DebtPolicyTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Disclosure of accounting policy for computing basic and diluted earnings or loss per share for each class of common stock and participating security. Addresses all significant policy factors, including any antidilutive items that have been excluded from the computation and takes into account stock dividends, splits and reverse splits that occur after the balance sheet date of the latest reporting period but before the issuance of the financial statements. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=84158767&loc=d3e18780-107790 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3630-109257 + Details
Name: | us-gaap_EarningsPerSharePolicyTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Disclosure of accounting policy for determining the fair value of financial instruments. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 60 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=7493716&loc=d3e21868-110260 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=118260190&loc=d3e13279-108611 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=84158767&loc=d3e18780-107790 + Details
Name: | us-gaap_FairValueOfFinancialInstrumentsPolicy
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Disclosure of accounting policy for (1) transactions denominated in a currency other than the reporting enterprise's functional currency, (2) translating foreign currency financial statements that are incorporated into the financial statements of the reporting enterprise by consolidation, combination, or the equity method of accounting, and (3) remeasurement of the financial statements of a foreign reporting enterprise in a hyperinflationary economy. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=84158767&loc=d3e18780-107790 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 30 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6450520&loc=d3e32583-110901 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6450222&loc=d3e30840-110895 + Details
Name: | us-gaap_ForeignCurrencyTransactionsAndTranslationsPolicyTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Disclosure of accounting policy for recognizing and measuring the impairment of long-lived assets. An entity also may disclose its accounting policy for long-lived assets to be sold. This policy excludes goodwill and intangible assets. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 05 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=109226317&loc=d3e202-110218 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=84158767&loc=d3e18780-107790 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SAB Topic 5.CC) -URI http://asc.fasb.org/extlink&oid=27011434&loc=d3e125687-122742 + Details
Name: | us-gaap_ImpairmentOrDisposalOfLongLivedAssetsPolicyTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Disclosure of accounting policy for investment in financial asset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571 + Details
Name: | us-gaap_InvestmentPolicyTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Disclosure of accounting policy for leasing arrangement entered into by lessee. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918666-209980 + Details
Name: | us-gaap_LesseeLeasesPolicyTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Disclosure of accounting policy pertaining to new accounting pronouncements that may impact the entity's financial reporting. Includes, but is not limited to, quantification of the expected or actual impact. + References No definition available. + Details
Name: | us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Disclosure of accounting policy for revenue from contract with customer. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=84158767&loc=d3e18823-107790 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -URI http://asc.fasb.org/topic&trid=49130388 + Details
Name: | us-gaap_RevenueFromContractWithCustomerPolicyTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Disclosure of accounting policy for award under share-based payment arrangement. Includes, but is not limited to, methodology and assumption used in measuring cost. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=84158767&loc=d3e18780-107790 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b),(f) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5047-113901 + Details
Name: | us-gaap_ShareBasedCompensationOptionAndIncentivePlansPolicy
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Disclosure of accounting policy for the use of estimates in the preparation of financial statements in conformity with generally accepted accounting principles. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6191-108592 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6161-108592 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6143-108592 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e5967-108592 Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6061-108592 Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6132-108592 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e5967-108592 + Details
Name: | us-gaap_UseOfEstimates
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration