XML 145 R129.htm IDEA: XBRL DOCUMENT
v3.20.1

Segmented Information - Schedule of Aggregates External Revenues by Customer (Detail) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018
Revenue from External Customer [Line Items] |  |
Sales | $ 39,431 | $ 40,827
General Motors [Member] |  |
Revenue from External Customer [Line Items] |  |
Sales | 5,732 | 6,303
BMW [Member] |  |
Revenue from External Customer [Line Items] |  |
Sales | 5,469 | 4,826
Ford Motor Company [Member] |  |
Revenue from External Customer [Line Items] |  |
Sales | 5,270 | 5,721
Fiat Chrysler Automobiles [Member] |  |
Revenue from External Customer [Line Items] |  |
Sales | 5,173 | 5,693
Daimler AG [Member] |  |
Revenue from External Customer [Line Items] |  |
Sales | 4,887 | 4,687
Volkswagen [Member] |  |
Revenue from External Customer [Line Items] |  |
Sales | 4,001 | 4,128
Other Customers [Member] |  |
Revenue from External Customer [Line Items] |  |
Sales | $ 8,899 | $ 9,469

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_EntityWideInformationRevenueFromExternalCustomerLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130545-203045 + Details
Name: | us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | srt_MajorCustomersAxis=mga_GeneralMotorsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_MajorCustomersAxis=mga_BmwMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_MajorCustomersAxis=mga_FordMotorCompanyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_MajorCustomersAxis=mga_FiatOrChryslerGroupMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_MajorCustomersAxis=mga_DaimlerAgMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_MajorCustomersAxis=mga_VolkswagenMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_MajorCustomersAxis=mga_OtherCustomersMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |