Represents the average cost per unit of physical commodities held by the entity as of the balance sheet date.

No definition available.

Name:	mux_InvestmentInPhysicalCommoditiesAverageCostPerUnit
Namespace Prefix:	mux_
Data Type:	us-types:perUnitItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the fair value per unit of physical commodities held by the entity as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	mux_InvestmentInPhysicalCommoditiesFairValuePerUnit
Namespace Prefix:	mux_
Data Type:	us-types:perUnitItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the market price per unit of physical commodities disposed of during the period.

+ References

No definition available.

+ Details

Name:	mux_InvestmentInPhysicalCommoditiesMarketPricePerUnit
Namespace Prefix:	mux_
Data Type:	us-types:perUnitItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	mux_InvestmentInPhysicalCommoditiesRollForward
Namespace Prefix:	mux_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The net realized gain (loss) on investments sold during the period, not including gains (losses) on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity, which, for cash flow reporting, is a component of proceeds from investing activities.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 28

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: 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=6943989&loc=d3e3602-108585

+ Details

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

- Details

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

- Definition

Investments held in physical commodities, such as gold, silver, platinum, crude oil, coal, sugar, rice, wheat.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.12)

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

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 12

-Article 5

+ Details

Name:	us-gaap_InvestmentInPhysicalCommodities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Investments held in physical commodities, such as gold, silver, platinum, crude oil, coal, sugar, rice, wheat.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 157

-Paragraph 33

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Name:	us-gaap_InvestmentInPhysicalCommoditiesFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Quantity of the investment. Indicate the measure in the unit of measure. This is commonly used for investments other than securities. For example, if the investment is gold, the balance would be the number of ounces and the unit of measure would indicate "ounces".

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 946

-SubTopic 320

-Section S99

-Paragraph 5

-Subparagraph (SX 210.12-13.2, Column B)

-URI http://asc.fasb.org/extlink&oid=6955306&loc=d3e611282-123010

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 13

-Paragraph Column B

-Article 12

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 13

-Paragraph 2

-Article 12

+ Details

Name:	us-gaap_InvestmentOwnedBalanceOtherMeasure
Namespace Prefix:	us-gaap_
Data Type:	num:massItemType
Balance Type:	na
Period Type:	instant

- Definition

The cash inflow associated with the sale of other investments not otherwise defined in the taxonomy.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 24

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3521-108585

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 26

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3574-108585

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 12

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3179-108585

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 16

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 18

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 15

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 31

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

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

- Definition

The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of investments, not including unrealized gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity, held at each balance sheet date and included in earnings for the period.

+ References

+ Details

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

GOLD AND SILVER BULLION (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
GOLD AND SILVER BULLION
Total cost	$ 1,416		$ 1,416		$ 1,690
Changes in the Company's holdings of gold and silver
Opening Balance			1,690	22,810	22,810
Proceeds from sale				(11,330)	(23,836)
Gain on sale		434		1,842	3,075
Unrealized loss	(274)	(359)	(274)	(359)	(359)
Ending Balance	1,416		1,416		1,690
Gold and silver \| Subsequent event
Changes in the Company's holdings of gold and silver
Proceeds from sale	1,500
Gold
GOLD AND SILVER BULLION
Number of ounces	793		793		793
Average cost per ounce (in dollars per ounce)	1,192.00		1,192.00		1,278.63
Total cost	945		945		1,014
Fair value per ounce (in dollars per ounce)	1,192.00		1,192.00		1,657.50
Total fair value	945		945		1,314
Changes in the Company's holdings of gold and silver
Opening Balance			1,014	7,232	7,232
Proceeds from sale					(7,982)
Gain on sale					1,764
Unrealized loss			(69)
Ending Balance	945		945		1,014
Gold \| Subsequent event
Changes in the Company's holdings of gold and silver
Market price per ounce (in dollars per ounce)	1,245.70
Silver
GOLD AND SILVER BULLION
Number of ounces	24,969		24,969		24,969
Average cost per ounce (in dollars per ounce)	18.86		18.86		27.08
Total cost	471		471		676
Fair value per ounce (in dollars per ounce)	18.86		18.86		29.95
Total fair value	471		471		748
Changes in the Company's holdings of gold and silver
Opening Balance			676	15,578	15,578
Proceeds from sale					(15,854)
Gain on sale					1,311
Unrealized loss			(205)		(359)
Ending Balance	$ 471		$ 471		$ 676
Silver \| Subsequent event
Changes in the Company's holdings of gold and silver
Market price per ounce (in dollars per ounce)	19.18