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v2.4.0.8

Investments - Additional Information (Detail) (Maximum [Member]) | 9 Months Ended
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Sep. 30, 2014
Maximum [Member] |
Schedule of Trading Securities and Other Trading Assets [Line Items] |
Investment securities maturity period or average life | 3 years
Average duration of portfolio | 1 year

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- Definition Investment Securities Maturity Period + References No definition available. + Details
Name: | mksi_InvestmentSecuritiesMaturityPeriod
Namespace Prefix: | mksi_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Definition Weighted Average Duration Investment Securities Portfolio + References No definition available. + Details
Name: | mksi_WeightedAverageDurationInvestmentSecuritiesPortfolio
Namespace Prefix: | mksi_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | us-gaap_ScheduleOfTradingSecuritiesAndOtherTradingAssetsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration