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Stock-Based Compensation - Summary of Information with Respect to Options Outstanding and Exercisable (Detail) (USD $) | 12 Months Ended |
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Dec. 31, 2014 | Dec. 31, 2013
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] |  |
Number of Shares Options Outstanding | 30,224 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber | 135,733 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
Weighted Average Exercise Price | $ 19.67 mksi_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsAndExercisableWeightedAverageExercisePrice |
Exercisable Weighted Average Remaining Contractual Life (In Years) | 10 months 6 days |
Aggregate Intrinsic Value (In Thousands) | $ 511,728 mksi_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingAndExercisableAggregateIntrinsicValue |
Minimum [Member] |  |
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] |  |
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range | $ 15.84 mksi_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRange / us-gaap_RangeAxis = us-gaap_MinimumMember |
Maximum [Member] |  |
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] |  |
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range | $ 24.35 mksi_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRange / us-gaap_RangeAxis = us-gaap_MaximumMember |

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- Definition Share based compensation arrangement by share based payment award options outstanding and exercisable aggregate intrinsic value. + References No definition available. + Details
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- Definition Share based compensation shares authorized under stock option plans exercise price range. + References No definition available. + Details
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- Definition Share based compensation shares authorized under stock option plans exercise price range number of outstanding and exercisable options weighted average remaining contractual term. + References No definition available. + Details
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- Definition Share based compensation shares authorized under stock option plans exercise price range outstanding options and exercisable weighted average exercise price. + References No definition available. + Details
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- Definition Number of options outstanding, including both vested and non-vested options. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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