Ownership Percentage by GFT.

No definition available.

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Namespace Prefix:	mga_
Data Type:	num:percentItemType
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- Definition

The cash inflow associated with the acquisition of business during the period (for example, cash that was held by the acquired business).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3179-108585

+ Details

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Period Type:	duration

- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

+ Details

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- 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

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- Details

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- Details

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Ownership Percentages and Carrying Value Principal Equity Method Investments (Parenthetical) (Detail) € in Millions, $ in Millions	Dec. 22, 2020 USD ($)	Dec. 22, 2020 EUR (€)	Dec. 31, 2020
Getrag (Jiangxi) Transmission Co., Ltd [GJT] [Member]
Schedule of Equity Method Investments [Line Items]
Cash Acquired in Business Acquisition	$ 160	€ 140
Getrag (Jiangxi) Transmission Co., Ltd [GJT] [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage			66.70%
Getrag Asia Pacific GmbH & Co. KG [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage by GFT			50.00%