Debt - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Dec. 31, 2012
Alter Power Systems [Member]
Debt [Line Items]
Number of financial institutions for available lines of credit and borrowing arrangements	4
Maturity dates of financial institutions	2013 through 2015
Japan line of credit [Member]
Debt [Line Items]
Number of financial institutions for available lines of credit and borrowing arrangements	2
Aggregate borrowings expire and renewed	3 month intervals
Aggregate borrowings	$ 24,424
Debt instrument maximum interest rate	0.63%
Debt instrument minimum interest rate	1.475%
Total borrowings outstanding	0	0
Plasmart line of credit [Member]
Debt [Line Items]
Aggregate borrowings	1,349
Total borrowings outstanding	0	0
Average interest rate on borrowings	5.19%
Line of credit facility expiration year	2014
Lines of credit [Member] \| Alter Power Systems [Member]
Debt [Line Items]
Aggregate borrowings	872
Lines of credit [Member] \| Alter Power Systems [Member] \| Minimum [Member]
Debt [Line Items]
Average interest rate on borrowings	6.66%
Lines of credit [Member] \| Alter Power Systems [Member] \| Maximum [Member]
Debt [Line Items]
Average interest rate on borrowings	7.75%
Term loan [Member] \| Alter Power Systems [Member]
Debt [Line Items]
Aggregate borrowings	564
Total borrowings outstanding	$ 791
Term loan [Member] \| Alter Power Systems [Member] \| Minimum [Member]
Debt [Line Items]
Average interest rate on borrowings	1.34%
Term loan [Member] \| Alter Power Systems [Member] \| Maximum [Member]
Debt [Line Items]
Average interest rate on borrowings	4.23%

Debt Instrument Date Of Maturity

No definition available.

Name:	mksi_DebtInstrumentDateOfMaturity
Namespace Prefix:	mksi_
Data Type:	xbrli:normalizedStringItemType
Balance Type:	na
Period Type:	duration

- Details

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

- Definition

Line Of Credit Facility Expiration Year

+ References

No definition available.

+ Details

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

- Definition

General renewal period for line of credit facility.

+ References

No definition available.

+ Details

Name:	mksi_LineOfCreditFacilityRenewalPeriod
Namespace Prefix:	mksi_
Data Type:	us-types:durationStringItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of financial institutions for lines of credit and borrowing arrangements.

+ References

No definition available.

+ Details

Name:	mksi_NumberOfFinancialInstitutionsThatProvideForAggregateBorrowings
Namespace Prefix:	mksi_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

When presenting a range of interest rates, the highest effective rate for funds borrowed under the debt agreement as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(1))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

When presenting a range of interest rates, the lowest effective rate for funds borrowed under the debt agreement as of the balance sheet date.

+ References

+ Details

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

- Definition

Reflects the calculation as of the balance sheet date of the average interest rate weighted by the amount of debt outstanding by type or by instrument at that time.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtWeightedAverageInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount borrowed under the credit facility as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

+ Details

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

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 129

-Paragraph 2, 4

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(b),22(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

+ Details

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