XML 133 R92.htm IDEA: XBRL DOCUMENT v2.4.1.9

Long-Term Employee Benefit Liabilities - Summary of Weighted Average Significant Actuarial Assumptions Adopted in Measuring Company's Projected Termination and Long Service Benefit Obligations and Net Periodic Benefit Cost (Detail) (Termination and Long Service Arrangements [Member])	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Termination and Long Service Arrangements [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.00%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = mga_TerminationAndLongServiceArrangementsMember	3.90%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = mga_TerminationAndLongServiceArrangementsMember	4.20%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = mga_TerminationAndLongServiceArrangementsMember
Rate of compensation increase	2.70%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = mga_TerminationAndLongServiceArrangementsMember	3.90%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = mga_TerminationAndLongServiceArrangementsMember	3.90%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = mga_TerminationAndLongServiceArrangementsMember

X

- Definition

The interest rate used to adjust for the time value of money for the plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (k)(1)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

+ Details

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Balance Type:	na
Period Type:	instant

X

- Definition

Expected rate of compensation increases (for pay-related plans).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (k)(2)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

X

- Details

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