XML 199 R111.htm IDEA: XBRL DOCUMENT
v3.22.1

Accumulated Other Comprehensive Loss - Additional Information (Detail) $ in Millions | Dec. 31, 2021 USD ($)
--- | ---
Equity [Abstract] |
Amount of comprehensive loss that is expected to be reclassified to net income | $ 26

X
- Definition Other comprehensive income that is expected to be reclassified to net income over the next fiscal year, net of tax. + References No definition available. + Details
Name: | mga_OtherComprehensiveIncomeToBeReclassifiedToNetIncome
Namespace Prefix: | mga_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_EquityAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration