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Represents the Funded Debt Leverage Ratio on which the entity will bear an additional interest on debt.

No definition available.

Name:	mg_DebtInstrumentCovenantFundedDebtLeverageRatioForAdditionalInterestPayment
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Represents the Funded Debt Leverage Ratio at which the entity will have the benefit of lower interest rate margin.

No definition available.

Name:	mg_DebtInstrumentCovenantFundedLeverageRatioConsideredForLowerInterestRateMargin
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Represents the Funded Debt Leverage Ratio at which the entity will have the maximum interest rate margin.

No definition available.

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Represents the Interest Coverage Ratio required under the terms of the covenants.

No definition available.

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Debt Instrument, Covenant Temporarily Increase in Funded Debt Leverage Ratio due to Business Acquisitions

No definition available.

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Debt Instrument, Debt Covenant, Maximum Aggregate Consideration For Acquisitions

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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Debt Instrument, Debt Covenant, Minimum Credit Exposure Percentage

No definition available.

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Debt Instrument, Non-recurring Charges Threshold Used For Calculation of Funded Debt Leverage Ratio

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Represents the number of consecutive fiscal quarters immediately preceding the date of determination of the Funded Debt Leverage Ratio.

No definition available.

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Debt Instrument, Number of Fiscal Quarters To Temporarily Increase Funded Debt Leverage Ratio due to Business Acquisitions

No definition available.

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Represents the preceding period used for determination of the Interest Coverage Ratio.

No definition available.

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Data Type:	xbrli:durationItemType
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Represents the maximum amount of borrowing capacity under the revolving credit facility that is available for the issuance of letters of credit.

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Represents the maximum borrowing capacity in non-U.S. dollar currencies under the revolving credit facility.

No definition available.

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Data Type:	xbrli:monetaryItemType
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Percentage points added to the reference rate to compute the variable rate on the debt instrument.

No definition available.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Data Type:	num:percentItemType
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Period Type:	instant

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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Period Type:	duration

Amount of the required periodic payments including both interest and principal payments.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Name:	us-gaap_LongTermDebt
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

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