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Net asset value of investment, excluding plan interest in master trust, held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

No definition available.

Name:	mga_EbpInvestmentExcludingPlanInterestInMasterTrustNetAssetValue
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Amount of contribution receivable from employer of participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

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Contract value of investment, excluding plan interest in master trust, held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Includes, but is not limited to, insurance contract meeting fully benefit-responsive investment criteria.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 962
-SubTopic 325
-Name Accounting Standards Codification
-Section 55
-Paragraph 17
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478873/962-325-55-17

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
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-Paragraph 1
-Subparagraph (SX 210.6A-05(a)(Schedule II))
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Fair and contract value of investment, excluding plan interest in master trust, held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Includes, but is not limited to, derivative, investment measured at net asset value per share as practical expedient, and insurance contract.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- References

No definition available.

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Amount of asset less liability available to pay benefit of participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)), including, but not limited to, aggregation of participants' individual account balances.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 962
-SubTopic 325
-Name Accounting Standards Codification
-Section 45
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Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
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-Topic 962
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Amount of unpaid principal plus accrued but unpaid interest for loan from participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

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Amount of contribution receivable from participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

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Amount of receivable of employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

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Namespace Prefix:	us-gaap-ebp_
Data Type:	xbrli:monetaryItemType
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- References

No definition available.