XML 101 R108.htm IDEA: XBRL DOCUMENT v2.4.1.9

Capital Stock - Maximum Number of Shares Outstanding Exercised or Converted (Detail) (Convertible Common Stock [Member], March 5, 2015 [Member])	Dec. 31, 2014
Convertible Common Stock [Member] | March 5, 2015 [Member]
Class of Stock [Line Items]
Common Shares	205,179,261us-gaap_CommonStockSharesOutstanding / us-gaap_StatementClassOfStockAxis = us-gaap_ConvertibleCommonStockMember / us-gaap_StatementScenarioAxis = mga_MarchFifthTwoThousandFifteenMember
Stock options	4,898,935mga_PotentiallyDilutiveSecuritiesOutstanding / us-gaap_StatementClassOfStockAxis = us-gaap_ConvertibleCommonStockMember / us-gaap_StatementScenarioAxis = mga_MarchFifthTwoThousandFifteenMember
Total number of shares outstanding	210,078,196mga_CommonSharesAndPotentiallyDilutiveSecuritiesOutstanding / us-gaap_StatementClassOfStockAxis = us-gaap_ConvertibleCommonStockMember / us-gaap_StatementScenarioAxis = mga_MarchFifthTwoThousandFifteenMember

X

- Definition

Common shares and potentially dilutive securities outstanding.

+ References

No definition available.

+ Details

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Namespace Prefix:	mga_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Potentially dilutive securities outstanding.

+ References

No definition available.

+ Details

Name:	mga_PotentiallyDilutiveSecuritiesOutstanding
Namespace Prefix:	mga_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

X

- Details

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

X

- Definition

Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.

+ 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)

-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 30

-Article 5

+ Details

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