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Stock-Based Compensation - Summary of Information with Respect to Options Outstanding and Exercisable (Detail) (USD $)	12 Months Ended
	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	30,224us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	135,733us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
Weighted Average Exercise Price	$ 19.67mksi_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsAndExercisableWeightedAverageExercisePrice
Exercisable Weighted Average Remaining Contractual Life (In Years)	10 months 6 days
Aggregate Intrinsic Value (In Thousands)	$ 511,728mksi_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	$ 15.84mksi_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	$ 24.35mksi_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRange / us-gaap_RangeAxis = us-gaap_MaximumMember

X

- Definition

Share based compensation arrangement by share based payment award options outstanding and exercisable aggregate intrinsic value.

+ References

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- Definition

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+ References

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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

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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

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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

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