XML 144 R107.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Capital Stock - Summary of Normal Course Issuer Bids (Detail) (USD $) In Millions, except Share data, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2013 | Dec. 31, 2012 | Dec. 31, 2011
Schedule Of Share Repurchase Programs [Line Items] |  |  |
Shares purchased | 14,082,321 | 895,032 | 10,747,300
Cash amount | $ 1,013 | $ 40 | $ 407
2010 Bid [Member] |  |  |
Schedule Of Share Repurchase Programs [Line Items] |  |  |
Maximum number of shares | 8,000,000 |  |
Shares purchased | 0 | 0 | 7,546,500
Cash amount | 0 | 0 | 296
2011 Bid [Member] |  |  |
Schedule Of Share Repurchase Programs [Line Items] |  |  |
Maximum number of shares | 12,000,000 |  |
Shares purchased | 0 | 467,630 | 3,200,800
Cash amount | 0 | 21 | 111
2012 Bid [Member] |  |  |
Schedule Of Share Repurchase Programs [Line Items] |  |  |
Maximum number of shares | 12,000,000 |  |
Shares purchased | 11,572,598 | 427,402 | 0
Cash amount | 814 | 19 | 0
2013 Bid [Member] |  |  |
Schedule Of Share Repurchase Programs [Line Items] |  |  |
Maximum number of shares | 12,000,000 |  |
Shares purchased | 2,509,723 | 0 | 0
Cash amount | $ 199 | $ 0 | $ 0

X
- Definition Cash Amount For Common Stock Repurchased Under Ncib + References No definition available. + Details
Name: | mga_CashAmountForCommonStockRepurchasedUnderNcib
Namespace Prefix: | mga_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Common stock repurchased during period shares. + References No definition available. + Details
Name: | mga_CommonStockRepurchasedDuringPeriodShares
Namespace Prefix: | mga_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Maximum Number of Common Stock Shares To Be Repurchased + References No definition available. + Details
Name: | mga_MaximumNumberOfCommonStockSharesToBeRepurchased
Namespace Prefix: | mga_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | mga_ScheduleOfShareRepurchaseProgramsLineItems
Namespace Prefix: | mga_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration