XML 64 R54.htm IDEA: XBRL DOCUMENT
v3.19.1

Investments - Gross Unrealized Gains and (Losses) Aggregated by Investment Category (Detail) - USD ($) $ in Thousands | Mar. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | $ 44,569 | $ 73,994
Investments, Gross Unrealized Gains | 4 | 7
Investments, Gross Unrealized (Losses) | (247) | (175)
Investments, Estimated Fair Value | 44,326 | 73,826
Time Deposits and Certificates of Deposit [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | 99 | 102
Investments, Gross Unrealized Gains | 2 |
Investments, Estimated Fair Value | 101 | 102
Bankers' Acceptance Drafts [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | 1,722 | 989
Investments, Estimated Fair Value | 1,722 | 989
Asset-Backed Securities [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost |  | 9,121
Investments, Gross Unrealized Gains |  | 1
Investments, Gross Unrealized (Losses) |  | (9)
Investments, Estimated Fair Value |  | 9,113
Commercial Paper [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | 33,752 | 19,504
Investments, Gross Unrealized Gains | 1 |
Investments, Gross Unrealized (Losses) | (244) | (145)
Investments, Estimated Fair Value | 33,509 | 19,359
Corporate Obligations [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | 8,996 | 9,367
Investments, Gross Unrealized Gains | 1 |
Investments, Gross Unrealized (Losses) | (3) | (15)
Investments, Estimated Fair Value | 8,994 | 9,352
U.S. Treasury Obligations [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost |  | 13,294
Investments, Gross Unrealized Gains |  | 4
Investments, Estimated Fair Value |  | 13,298
U.S. Agency Obligations [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost |  | 21,617
Investments, Gross Unrealized Gains |  | 2
Investments, Gross Unrealized (Losses) |  | (6)
Investments, Estimated Fair Value |  | 21,613
Group Insurance Contracts [Member] | Long Term Investments [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | 5,582 | 5,546
Investments, Gross Unrealized Gains | 368 | 344
Investments, Estimated Fair Value | $ 5,950 | $ 5,890

X
- Definition Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading. + References No definition available. + Details
Name: | us-gaap_AvailableForSaleSecurities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563 + Details
Name: | us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale. + References No definition available. + Details
Name: | us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any. + References No definition available. + Details
Name: | us-gaap_AvailableForSaleSecuritiesAmortizedCost
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_InvestmentTypeAxis=mksi_TimeDepositsAndCertificatesOfDepositMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_BankersAcceptanceMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_AssetBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_CommercialPaperMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_USTreasurySecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=mksi_GroupInsuranceContractsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | invest_InvestmentAxis=mksi_LongTermInvestmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |