Amortization period of leasehold improvements.

No definition available.

Name:	mksi_AmortizationPeriodOfLeaseholdImprovements
Namespace Prefix:	mksi_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum period of company's research and development projects.

+ References

No definition available.

+ Details

Name:	mksi_MaximumPeriodOfCompanysResearchAndDevelopmentProjects
Namespace Prefix:	mksi_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Minimum percentage of recognized tax benefits from uncertain tax position.

+ References

No definition available.

+ Details

Name:	mksi_MinimumPercentageOfRecognizedTaxBenefitsFromUncertainTaxPosition
Namespace Prefix:	mksi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Minimum period of company's research and development projects.

+ References

No definition available.

+ Details

Name:	mksi_MinimumPeriodOfCompanysResearchAndDevelopmentProjects
Namespace Prefix:	mksi_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Revenue recognition payment terms.

+ References

No definition available.

+ Details

Name:	mksi_RevenueRecognitionPaymentTerms
Namespace Prefix:	mksi_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Schedule of significant accounting policies [Line Items].

+ References

No definition available.

+ Details

Name:	mksi_ScheduleOfSignificantAccountingPoliciesLineItems
Namespace Prefix:	mksi_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Separately priced contracts term.

+ References

No definition available.

+ Details

Name:	mksi_SeparatelyPricedContractsTerm
Namespace Prefix:	mksi_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Warranty period.

+ References

No definition available.

+ Details

Name:	mksi_WarrantyPeriod
Namespace Prefix:	mksi_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6351-108592

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=118260190&loc=d3e13531-108611

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118260190&loc=d3e13537-108611

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6404-108592

+ Details

Name:	us-gaap_ConcentrationRiskPercentage1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_FiniteLivedIntangibleAssetUsefulLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount before tax of foreign currency transaction realized gain (loss) recognized in the income statement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=109240200&loc=d3e30690-110894

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6450222&loc=d3e30840-110895

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 20
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109240200&loc=d3e30700-110894

+ Details

Name:	us-gaap_ForeignCurrencyTransactionGainLossRealized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Present value of lessee's discounted obligation for lease payments from operating lease, classified as current.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=77888419&loc=SL77918627-209977

+ Details

Name:	us-gaap_OperatingLeaseLiabilityCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Present value of lessee's discounted obligation for lease payments from operating lease, classified as noncurrent.

+ References

+ Details

Name:	us-gaap_OperatingLeaseLiabilityNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of lessee's right to use underlying asset under operating lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77888419&loc=SL77918627-209977

+ Details

Name:	us-gaap_OperatingLeaseRightOfUseAsset
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

+ References

No definition available.

+ Details

Name:	us-gaap_PropertyPlantAndEquipmentUsefulLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The cumulative amount of the reporting entity's undistributed earnings or deficit.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(30)(a)(3))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(23)(a)(4))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

+ Details

Name:	us-gaap_RetainedEarningsAccumulatedDeficit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=us-gaap_AccountingStandardsUpdate201409Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=us-gaap_AccountingStandardsUpdate201602Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementLocationAxis=us-gaap_OtherExpenseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ConcentrationRiskByTypeAxis=us-gaap_CustomerConcentrationRiskMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ConcentrationRiskByBenchmarkAxis=us-gaap_SalesRevenueNetMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_MajorCustomersAxis=mksi_SemiconductorProductsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ConcentrationRiskByTypeAxis=us-gaap_CreditConcentrationRiskMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ConcentrationRiskByBenchmarkAxis=us-gaap_AccountsReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_BuildingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_MachineryAndEquipmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_FurnitureAndFixturesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_OfficeEquipmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2019	Jan. 01, 2018
Schedule Of Significant Accounting Policies [Line Items]
Minimum period of company's research and development projects	3 months
Maximum period of company's research and development projects	30 months
Vesting period	3 years
Amortization period of leasehold improvements	shorter of the lease term or the estimated useful life of the leased asset.
Minimum percentage of recognition of tax benefits from uncertain tax positions	50.00%
Retained earnings opening balance sheet adjustment for Topic 606 adoption	$ 1,181,216	$ 1,084,797
Right-of-Use Asset,Operating Lease	64,497
Short-term lease liability	20,632
Non-current lease liability	44,759
Accounting Standards Codification Topic 606 adjustment [Member]
Schedule Of Significant Accounting Policies [Line Items]
Retained earnings opening balance sheet adjustment for Topic 606 adoption					$ 1,738
Accounting Standards Update 2016-02 [Member]
Schedule Of Significant Accounting Policies [Line Items]
Right-of-Use Asset,Operating Lease				$ 71,042
Short-term lease liability				20,192
Non-current lease liability				$ 54,147
Other Expense [Member]
Schedule Of Significant Accounting Policies [Line Items]
Net foreign exchange losses from re-measurement	$ 31	$ 2,497	$ 6,132
Customer Concentration Risk [Member] \| Sales Revenue, Net [Member]
Schedule Of Significant Accounting Policies [Line Items]
Concentration risk, percentage	10.00%
Customer Concentration Risk [Member] \| Semiconductor Products [Member] \| Sales Revenue, Net [Member]
Schedule Of Significant Accounting Policies [Line Items]
Concentration risk, percentage	49.00%	55.00%	57.00%
Minimum [Member]
Schedule Of Significant Accounting Policies [Line Items]
Intangible assets amortized period	1 year
Minimum [Member] \| Accounting Standards Codification Topic 606 adjustment [Member]
Schedule Of Significant Accounting Policies [Line Items]
Company's normal payment terms	30 days
Warranty period	12 months
Term of separately priced contracts	12 months
Minimum [Member] \| Credit Concentration Risk [Member] \| Accounts Receivable [Member]
Schedule Of Significant Accounting Policies [Line Items]
Concentration risk, percentage	10.00%	10.00%
Minimum [Member] \| Building [Member]
Schedule Of Significant Accounting Policies [Line Items]
Estimated useful lives	10 years
Minimum [Member] \| Machinery and Equipment [Member]
Schedule Of Significant Accounting Policies [Line Items]
Estimated useful lives	3 years
Minimum [Member] \| Furniture and Fixtures [Member]
Schedule Of Significant Accounting Policies [Line Items]
Estimated useful lives	3 years
Minimum [Member] \| Office Equipment [Member]
Schedule Of Significant Accounting Policies [Line Items]
Estimated useful lives	3 years
Maximum [Member]
Schedule Of Significant Accounting Policies [Line Items]
Intangible assets amortized period	18 years
Maximum [Member] \| Accounting Standards Codification Topic 606 adjustment [Member]
Schedule Of Significant Accounting Policies [Line Items]
Company's normal payment terms	60 days
Warranty period	24 months
Term of separately priced contracts	60 months
Maximum [Member] \| Building [Member]
Schedule Of Significant Accounting Policies [Line Items]
Estimated useful lives	50 years
Maximum [Member] \| Machinery and Equipment [Member]
Schedule Of Significant Accounting Policies [Line Items]
Estimated useful lives	18 years
Maximum [Member] \| Furniture and Fixtures [Member]
Schedule Of Significant Accounting Policies [Line Items]
Estimated useful lives	18 years
Maximum [Member] \| Office Equipment [Member]
Schedule Of Significant Accounting Policies [Line Items]
Estimated useful lives	18 years