XML 131 R90.htm IDEA: XBRL DOCUMENT
v3.21.1

Debt - Schedule of Company's Long-Term Debt (Parenthetical) (Detail) | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2020 USD ($) | Dec. 31, 2020 CAD ($) | Dec. 31, 2020 EUR (€) | Dec. 31, 2019
Three Point Six Two Five Senior Notes [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Senior Notes, face amount | $ 750,000,000 |  |  |
Senior Notes, due year | 2024 |  |  |
Interest rate | 3.625% | 3.625% | 3.625% |
Four Point One Five Zero Senior Notes [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Senior Notes, face amount | $ 650,000,000 |  |  |
Senior Notes, due year | 2025 |  |  |
Interest rate | 4.15% | 4.15% | 4.15% |
One Point Nine Zero Zero Senior Notes [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Senior Notes, face amount | € |  |  | € 550,000,000 |
Senior Notes, due year | 2023 |  |  |
Interest rate | 1.90% | 1.90% | 1.90% |
One Point Five Zero Zero Senior Notes [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Senior Notes, face amount | € |  |  | € 600,000,000 |
Senior Notes, due year | 2027 |  |  |
Interest rate | 1.50% | 1.50% | 1.50% |
Three Point One Zero Zero Senior Notes [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Senior Notes, face amount |  | $ 425,000,000 |  |
Senior Notes, due year | 2022 |  |  |
Interest rate | 3.10% | 3.10% | 3.10% |
Two Point Four Five Zero Senior Notes [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Senior Notes, face amount | $ 750,000,000 |  |  |
Senior Notes, due year | 2030 |  |  |
Interest rate | 2.45% | 2.45% | 2.45% |
Bank Term Debt [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Weighted average interest rate of bank term debt | 4.23% | 4.23% | 4.23% | 4.97%
Government Loans [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Weighted average interest rate of bank term debt | 1.54% | 1.54% | 1.54% | 1.63%

X
- Definition Debt Instrument Due Year + References No definition available. + Details
Name: | mga_DebtInstrumentDueYear
Namespace Prefix: | mga_
Data Type: | xbrli:gYearItemType
Balance Type: | na
Period Type: | duration

X
- Definition Face (par) amount of debt instrument at time of issuance. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28551-108399 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400 + Details
Name: | us-gaap_DebtInstrumentFaceAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Contractual interest rate for funds borrowed, under the debt agreement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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

X
- Definition Weighted average interest rate of long-term debt outstanding calculated at point in time. + References No definition available. + Details
Name: | us-gaap_LongtermDebtWeightedAverageInterestRate
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_LongtermDebtTypeAxis=mga_ThreePointSixTwoFiveSeniorNotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongtermDebtTypeAxis=mga_FourPointOneFiveZeroSeniorNotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongtermDebtTypeAxis=mga_OnePointNineZeroZeroSeniorNotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongtermDebtTypeAxis=mga_OnePointFiveZeroZeroSeniorNotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongtermDebtTypeAxis=mga_ThreePointOneZeroZeroSeniorNotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongtermDebtTypeAxis=mga_TwoPointFourFiveZeroSeniorNotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongtermDebtTypeAxis=mga_BankTermDebtMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongtermDebtTypeAxis=mga_GovernmentLoansMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |