CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (USD $) In Thousands, except Share data, unless otherwise specified	Common Stock	Accumulated Other Comprehensive (Loss) Income	Accumulated Deficit	Total
Balance at Dec. 31, 2011	$ 613,831	$ (1,289)	$ (393,238)	$ 219,304us-gaap_StockholdersEquity
Balance (in shares) at Dec. 31, 2011	139,753
Increase (Decrease) in Shareholders' Equity
Stock-based compensation	3,405			3,405
Issuance of exchangeable shares to acquire Minera Andes Inc.	664,671			664,671
Issuance of exchangeable shares to acquire Minera Andes Inc. (in shares)	127,331
Assumption of stock options in connection with the acquisition of Minera Andes Inc.	3,175			3,175
Sale of shares for cash, net of issuance costs	43,047			43,047
Sale of shares for cash, net of issuance costs (in shares)	19,552
Sale of exchangeable shares for cash, net of issuance costs	17,372			17,372
Sale of exchangeable shares for cash, net of issuance costs (in shares)	7,799
Exercise of stock options	819			819
Exercise of stock options (in shares)	445			445,000
Exercise of stock options assumed from Minera Andes Inc. acquisition	3,066			3,066
Exercise of stock options assumed from Minera Andes Inc. acquisition (in shares)	1,062
Shares issued for Mexico mining concessions	391			391
Shares issued for Mexico mining concessions (in shares)	83
Unrealized loss on marketable securities		(5)		(5)
Unrealized gain on available-for-sale securities, net of taxes				(5)
Reclassification of unrealized loss on marketable equity securities disposed of during the period, net of tax		(993)		(993)
Other-than-temporary impairment on marketable equity securities		1,993		1,993
Net loss			(66,654)	(66,654)
Balance at Dec. 31, 2012	1,349,777	(294)	(459,892)	889,591us-gaap_StockholdersEquity
Balance (in shares) at Dec. 31, 2012	296,025
Increase (Decrease) in Shareholders' Equity
Stock-based compensation	1,382			1,382
Exercise of stock options	95			95
Exercise of stock options (in shares)	48			48,000
Exercise of stock options assumed from Minera Andes Inc. acquisition	76			76
Exercise of stock options assumed from Minera Andes Inc. acquisition (in shares)	45
Shares issued for litigation settlement	3,270			3,270
Shares issued for litigation settlement (in shares)	1,000
Shares issued for Mexico mining concessions	96			96
Shares issued for Mexico mining concessions (in shares)	41
Unrealized gain on available-for-sale securities, net of taxes		(1)		(1)
Net loss			(147,742)	(147,742)
Balance at Dec. 31, 2013	1,354,696	(295)	(607,634)	746,767us-gaap_StockholdersEquity
Balance (in shares) at Dec. 31, 2013	297,159
Increase (Decrease) in Shareholders' Equity
Stock-based compensation	1,324			1,324
Exercise of stock options	1,932			1,932
Exercise of stock options (in shares)	1,499			1,499,000
Exercise of stock options assumed from Minera Andes Inc. acquisition	360			360
Exercise of stock options assumed from Minera Andes Inc. acquisition (in shares)	198
Shares issued for settlement of accounts payable	1,004			1,004
Shares issued for accounts paybable (in shares)	394,000
Shares issued to terminate TNR Gold Corp's back-in right	1,352			1,352
Shares issued to terminate TNR Gold Corp's back-in right (in shares)	850
Unrealized gain on available-for-sale securities, net of taxes		419		419
Net loss			(311,943)	(311,943)
Balance at Dec. 31, 2014	$ 1,360,668	$ 124	$ (919,577)	$ 441,215us-gaap_StockholdersEquity
Balance (in shares) at Dec. 31, 2014	300,100

Number of shares of exchangeable stock issued during the period pursuant to acquisitions.

No definition available.

Name:	mux_ExchangeableStockIssuedDuringPeriodSharesAcquisitions
Namespace Prefix:	mux_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the number of new exchangeable shares issued during the period.

+ References

No definition available.

+ Details

Name:	mux_ExchangeableStockIssuedDuringPeriodSharesNewIssues
Namespace Prefix:	mux_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Value of exchangeable stock issued pursuant to acquisitions during the period.

+ References

No definition available.

+ Details

Name:	mux_ExchangeableStockIssuedDuringPeriodValueAcquisitions
Namespace Prefix:	mux_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Represents the equity impact of the value of new exchangeable stock issued during the period.

+ References

No definition available.

+ Details

Name:	mux_ExchangeableStockIssuedDuringPeriodValueNewIssues
Namespace Prefix:	mux_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The number of shares issued to nonemployees as payment for services rendered or acknowledged claims.

+ References

No definition available.

+ Details

Name:	mux_IssuanceOfStockAndWarrantsForServicesOrClaimsShares
Namespace Prefix:	mux_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the number of shares of stock issued during the period pursuant to settlement of litigation.

+ References

No definition available.

+ Details

Name:	mux_StockIssuedDuringPeriodSharesIssuedForLitigationSettlement
Namespace Prefix:	mux_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the value of stock issued pursuant to settlement of litigation during the period.

+ References

No definition available.

+ Details

Name:	mux_StockIssuedDuringPeriodValueIssuedForLitigationSettlement
Namespace Prefix:	mux_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Value stock issued during the period as a result of the assumption of stock options in connection with acquisition of business.

+ References

No definition available.

+ Details

Name:	mux_StockIssuedDuringPeriodValueStockOptionsAssumedInAcquisitionOfBusiness
Namespace Prefix:	mux_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_IncreaseDecreaseInStockholdersEquityRollForward
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Fair value of share-based compensation granted to nonemployees as payment for services rendered or acknowledged claims.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

+ Details

Name:	us-gaap_IssuanceOfStockAndWarrantsForServicesOrClaims
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The aggregate net change in the difference between the fair value and the carrying value, or in the comparative fair values, of marketable securities categorized as trading held at each balance sheet date, that was included in earnings for the period, which may have arisen from (a) securities classified as trading, (b) the unrealized holding gain (loss) on held-to-maturity securities transferred to the trading security category, and (c) the cumulative unrealized gain (loss) which was included in other comprehensive income (a separate component of shareholders' equity) on available-for-sale securities transferred to trading securities during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 9

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27357-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 10

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27405-111563

+ Details

Name:	us-gaap_MarketableSecuritiesUnrealizedGainLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Net income after adjustments for dividends on preferred stock (declared in the period) and/or cumulative preferred stock (accumulated for the period).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 260

-SubTopic 10

-Section 45

-Paragraph 11

-URI http://asc.fasb.org/extlink&oid=7655603&loc=d3e1377-109256

+ Details

Name:	us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount after tax and reclassification adjustments, of appreciation (loss) in value of unsold available-for-sale securities, attributable to parent entity. Excludes amounts related to other than temporary impairment (OTTI) loss.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 45

-Paragraph 20

-URI http://asc.fasb.org/extlink&oid=7656940&loc=SL4569643-111683

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 45

-Paragraph 19

-URI http://asc.fasb.org/extlink&oid=7656940&loc=SL4569616-111683

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 50

-Paragraph 1A

-Subparagraph (c)(3)

-URI http://asc.fasb.org/extlink&oid=18733093&loc=SL4573702-111684

+ Details

Name:	us-gaap_OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentNetOfTaxPortionAttributableToParent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount after tax of reclassification adjustment from accumulated other comprehensive income for unrealized gain (loss) realized upon the sale of available-for-sale securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 9

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27357-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 11

-URI http://asc.fasb.org/extlink&oid=28358780&loc=d3e637-108580

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 15

-URI http://asc.fasb.org/extlink&oid=28358780&loc=d3e689-108580

+ Details

Name:	us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount after tax of reclassification adjustment from accumulated other comprehensive income for unrealized loss realized upon the write-down of available-for-sale securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 11

-URI http://asc.fasb.org/extlink&oid=28358780&loc=d3e637-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 15

-URI http://asc.fasb.org/extlink&oid=28358780&loc=d3e689-108580

+ Details

Name:	us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForWritedownOfSecuritiesNetOfTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Number of shares of stock issued as of the balance sheet date, including shares that had been issued and were previously outstanding but which are now held in the treasury.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

+ Details

Name:	us-gaap_SharesIssued
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SAB TOPIC 4.E)

-URI http://asc.fasb.org/extlink&oid=27010918&loc=d3e74512-122707

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 4

-Section E

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.29-31)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 29, 30, 31

-Article 5

+ Details

Name:	us-gaap_StockholdersEquity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Number of shares of stock issued during the period pursuant to acquisitions.

+ References

+ Details

Name:	us-gaap_StockIssuedDuringPeriodSharesAcquisitions
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of new stock issued during the period.

+ References

+ Details

Name:	us-gaap_StockIssuedDuringPeriodSharesNewIssues
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of shares of stock issued during the period that is attributable to transactions involving issuance of stock not separately disclosed.

+ References

No definition available.

+ Details

Name:	us-gaap_StockIssuedDuringPeriodSharesOther
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of shares of stock issued during the period as part of a transaction to acquire assets that do not qualify as a business combination.

+ References

No definition available.

+ Details

Name:	us-gaap_StockIssuedDuringPeriodSharesPurchaseOfAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of share options (or share units) exercised during the current period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-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://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.28,29)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)(iv)(2)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 29, 30

-Article 5

+ Details

Name:	us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Value of stock issued pursuant to acquisitions during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-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://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.29-31)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 29, 30, 31

-Article 5

+ Details

Name:	us-gaap_StockIssuedDuringPeriodValueAcquisitions
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- 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

+ Details

Name:	us-gaap_StockIssuedDuringPeriodValueNewIssues
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Value of shares of stock issued during the period that is attributable to transactions involving issuance of stock not separately disclosed.

+ References

No definition available.

+ Details

Name:	us-gaap_StockIssuedDuringPeriodValueOther
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Value of shares of stock issued during the period as part of a transaction to acquire assets that do not qualify as a business combination.

+ References

No definition available.

+ Details

Name:	us-gaap_StockIssuedDuringPeriodValuePurchaseOfAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Value of stock (or other type of equity) issued during the period as a result of any equity-based compensation plan other than an employee stock ownership plan (ESOP), net of stock value of such awards forfeited. Stock issued could result from the issuance of restricted stock, the exercise of stock options, stock issued under employee stock purchase plans, and/or other employee benefit plans.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-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 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (d)(1)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 29, 30, 31

-Article 5

+ Details

Name:	us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Value of stock issued as a result of the exercise of stock options.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-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://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.29-31)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 29, 30, 31

-Article 5

+ Details

Name:	us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration