XML 153 R117.htm IDEA: XBRL DOCUMENT v2.4.1.9

Contingencies - Additional Information (Detail) (CAD) In Billions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014
Loss Contingencies [Line Items]
Amount related to damages	3.5us-gaap_LossContingencyDamagesSoughtValue
KS Centoco Ltd [Member]
Loss Contingencies [Line Items]
Number of subsidiaries sued by KS Centoco Ltd	2mga_NumberOfSubsidiariesSuedByKSCentocoLtdAndCentocoHoldingsLimited / dei_LegalEntityAxis = mga_KsCentocoLimitedMember
Percentage of equity interest owned by Company	23.00%mga_PercentageOfEquityInterestOwnedByCompany / dei_LegalEntityAxis = mga_KsCentocoLimitedMember
Percentage of equity interest owned by third party	77.00%mga_PercentageOfEquityInterestOwnedByThirdParty / dei_LegalEntityAxis = mga_KsCentocoLimitedMember
MST Automotive Inc [Member]
Loss Contingencies [Line Items]
Percentage of equity interest owned by Company	77.00%mga_PercentageOfEquityInterestOwnedByCompany / dei_LegalEntityAxis = mga_MstAutomotiveIncMember
Percentage of equity interest owned by third party	23.00%mga_PercentageOfEquityInterestOwnedByThirdParty / dei_LegalEntityAxis = mga_MstAutomotiveIncMember

X

- Definition

Number of subsidiaries sued by K S Centoco Ltd and Centoco Holdings Limited.

+ References

No definition available.

+ Details

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X

- Definition

Percentage of equity interest owned by company.

+ References

No definition available.

+ Details

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Namespace Prefix:	mga_
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X

- Definition

Percentage of equity interest owned by third party.

+ References

No definition available.

+ Details

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Namespace Prefix:	mga_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Details

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

X

- Definition

The value (monetary amount) of the award the plaintiff seeks in the legal matter.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14326-108349



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 4

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14435-108349



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 9

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14557-108349

+ Details

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- Details

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Namespace Prefix:
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Period Type:

X

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: