XML 74 R42.htm IDEA: XBRL DOCUMENT
v3.19.3

INVESTMENTS (Details) - USD ($) $ / shares in Units, $ in Thousands |  |  |  | 3 Months Ended | 9 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | --- | --- | --- | ---
May 23, 2019 | Mar. 29, 2019 | Dec. 20, 2018 | Sep. 30, 2019 | Sep. 30, 2018 | Sep. 30, 2019 | Sep. 30, 2018 | Dec. 31, 2018 | Oct. 01, 2019 | Dec. 19, 2017
Investments rollforward |  |  |  |  |  |  |  |  |  |
Opening balance |  |  |  |  |  | $ 3,131 | $ 7,971 | $ 7,971 |  |
Additions/transfers during the period |  |  |  |  |  | 2,314 | 2,083 |  |  |
Net gain (loss) on securities sold |  |  |  |  |  | 3,375 | (767) |  |  |
Disposals/transfers during period |  |  |  |  |  | (7,193) | (3,599) |  |  |
Unrealized gains (loss) on securities held |  |  |  | $ 200 |  | 1,597 | (2,526) |  |  |
Fair Value end of the period |  |  |  | 3,224 | 3,162 | 3,224 | 3,162 | 3,131 |  |
Marketable equity securities receivable |  |  |  | $ 939 |  | 939 |  |  |  |
Stock issued during the period (in shares) | 1,935,484 | 14,193,548 |  |  |  |  |  |  |  |
Stock issued during the period |  | $ 20,300 |  |  |  | 22,900 |  |  |  |
Proceeds from sale of investments |  |  |  |  |  | 4,714 | 3,667 |  |  |
Cost of purchase of marketable equity securities |  |  |  |  |  | 2,400 |  | 2,900 |  |
Price per unit |  | $ 1.55 |  |  |  |  |  |  |  |
Great Bear |  |  |  |  |  |  |  |  |  |
Investments rollforward |  |  |  |  |  |  |  |  |  |
Number of shares received from exercise of warrants |  |  |  | 393,093 |  |  |  |  |  |
Payment to exercise warrants |  |  |  | $ 500 |  |  |  |  |  |
Fair value that was transferred from warrants at exercise date to marketable equity securities |  |  |  | 1,500 |  |  |  |  |  |
Common Stock |  |  |  |  |  |  |  |  |  |
Investments rollforward |  |  |  |  |  |  |  |  |  |
Stock issued during the period |  |  |  |  |  | 20,300 |  |  |  |
Warrants |  |  |  |  |  |  |  |  |  |
Investments rollforward |  |  |  |  |  |  |  |  |  |
Stock issued during the period |  |  |  |  |  | 2,600 |  |  |  |
Flow Through Common Shares |  |  |  |  |  |  |  |  |  |
Investments rollforward |  |  |  |  |  |  |  |  |  |
Stock issued during the period |  |  | $ 14,100 |  |  |  |  |  |  |
Price per unit |  |  | $ 2.24 |  |  |  |  |  |  | $ 2.50
Marketable equity securities |  |  |  |  |  |  |  |  |  |
Investments rollforward |  |  |  |  |  |  |  |  |  |
Opening balance |  |  |  |  |  | 2,718 | 6,404 | 6,404 |  |
Additions/transfers during the period |  |  |  |  |  | 2,314 | 1,882 |  |  |
Net gain (loss) on securities sold |  |  |  | 3,400 |  | 3,375 | (767) |  |  |
Disposals/transfers during period |  |  |  |  |  | (5,653) | (2,895) |  |  |
Unrealized gains (loss) on securities held |  |  |  | 900 |  | 470 | (1,795) |  |  |
Fair Value end of the period |  |  |  | 3,224 | 2,829 | 3,224 | 2,829 | 2,718 |  |
Marketable equity securities receivable |  |  |  |  |  |  |  |  | $ 900 |
Proceeds from sale of investments |  |  |  | 5,700 |  | 5,700 | 3,700 |  |  |
Warrants |  |  |  |  |  |  |  |  |  |
Investments rollforward |  |  |  |  |  |  |  |  |  |
Opening balance |  |  |  |  |  | 413 | 1,567 | 1,567 |  |
Additions/transfers during the period |  |  |  |  |  |  | 201 |  |  |
Disposals/transfers during period |  |  |  |  |  | (1,540) | (704) |  |  |
Unrealized gains (loss) on securities held |  |  |  |  |  | $ 1,127 | (731) |  |  |
Unrealized gains (loss) on warrants |  |  |  | $ 700 |  |  |  |  |  |
Fair Value end of the period |  |  |  |  | $ 333 |  | $ 333 | $ 413 |  |

X
- Definition Gross realized gains (losses) on equity securities. + References No definition available. + Details
Name: | mux_AvailableForSaleAndTradingSecuritiesGrossUnrealizedGainLoss
Namespace Prefix: | mux_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The fair value that was transferred from warrants at exercise date to marketable equity securities. + References No definition available. + Details
Name: | mux_FairValueTransferredFromWarrantsToMarketableEquitySecurities
Namespace Prefix: | mux_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
Name: | mux_InvestmentsRollforward
Namespace Prefix: | mux_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of receivables classified as marketable equity securities. + References No definition available. + Details
Name: | mux_MarketableEquitySecuritiesReceivable
Namespace Prefix: | mux_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The number of shares received as a result of the exercising warrants. + References No definition available. + Details
Name: | mux_NumberOfSharesReceivedDuringPeriodValueWarrantsExercised
Namespace Prefix: | mux_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Payment to exercise warrants. + References No definition available. + Details
Name: | mux_PaymentToExerciseWarrants
Namespace Prefix: | mux_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Cash flow for purchase of available for sale and trading securities. + References No definition available. + Details
Name: | mux_PaymentsToAcquireAvailableForSaleAndTradingSecurities
Namespace Prefix: | mux_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The cash inflow associated with the sale of equity securities classified as available-for-sale or trading securities. This refers to cash disposals and includes conversions and removals. + References No definition available. + Details
Name: | mux_ProceedsFromDisposalOfAvailableForSaleAndTradingSecurities
Namespace Prefix: | mux_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Gross realized gains (losses) on warrants. + References No definition available. + Details
Name: | mux_WarrantsGrossUnrealizedGainLoss
Namespace Prefix: | mux_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 45 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=99377092&loc=SL75136599-209740 + Details
Name: | us-gaap_EquitySecuritiesFvNi
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of realized gain (loss) from sale of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 321 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=116654751&loc=SL75117546-209714 + Details
Name: | us-gaap_EquitySecuritiesFvNiRealizedGainLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Cash paid to purchase debt and equity securities, classified as operating activities, during the period; includes trading securities and any other investments classified as operating. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 25 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3536-108585 + Details
Name: | us-gaap_PaymentsForPurchaseOfSecuritiesOperatingActivities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The cash inflow associated with the aggregate amount received by the entity through sale or maturity of marketable securities (held-to-maturity or available-for-sale) during the period. + References No definition available. + Details
Name: | us-gaap_ProceedsFromSaleAndMaturityOfMarketableSecurities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Price of a single share of a number of saleable stocks of a company. + References No definition available. + Details
Name: | us-gaap_SharePrice
Namespace Prefix: | us-gaap_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of new stock issued during the period. + References Reference 1: 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(29)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770 Reference 4: 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(28)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_StockIssuedDuringPeriodSharesNewIssues
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Equity impact of the value of new stock issued during the period. Includes shares issued in an initial public offering or a secondary public offering. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644 Reference 3: 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(29)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 4: 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(28)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_StockIssuedDuringPeriodValueNewIssues
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | invest_InvestmentIssuerAxis=mux_GreatBearResourcesLtdMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=us-gaap_CommonStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=us-gaap_WarrantMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=mux_IssuanceOfFlowThroughCommonSharesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=mux_MarketableEquitySecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=mux_WarrantsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |