XML 134 R93.htm IDEA: XBRL DOCUMENT v3.21.1

Leases - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($)
Lessee, Lease, Description [Line Items]
Operating lease term	5 years
Operating Lease Option To Extend	options to extend the term of the lease
Manufacturing Facility [Member]
Lessee, Lease, Description [Line Items]
Operating lease liabilitites	$ 12
Operating lease year of commencement	2021
Use Rights [Member]
Lessee, Lease, Description [Line Items]
Operating lease term	90 years
Maximum [Member]
Lessee, Lease, Description [Line Items]
Operating lease term	7 years
Maximum [Member] | Manufacturing Facility [Member]
Lessee, Lease, Description [Line Items]
Operating lease term	10 years
Minimum [Member]
Lessee, Lease, Description [Line Items]
Operating lease term	1 year
Minimum [Member] | Manufacturing Facility [Member]
Lessee, Lease, Description [Line Items]
Operating lease term	1 year

X

- Definition

Lessee, Operating Lease, Lease Not yet Commenced, Liability.

+ References

No definition available.

+ Details

Name:	mga_LesseeOperatingLeaseLeaseNotYetCommencedLiability
Namespace Prefix:	mga_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Operating Lease, Year Of Commencement

+ References

No definition available.

+ Details

Name:	mga_OperatingLeaseYearOfCommencement
Namespace Prefix:	mga_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	duration

X

- Definition

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.

+ References

No definition available.

+ Details

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

X

- Definition

Description of terms and conditions of option to extend lessee's operating lease. Includes, but is not limited to, information about option recognized as part of right-of-use asset and lease liability.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=121609121&loc=SL77918673-209980

+ Details

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

X

- Definition

Term of lessee's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=121609121&loc=SL77918673-209980

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

X

- Details

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

X

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_UseRightsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: