| Document and Entity Information | Feb. 08, 2021 |
| Cover [Abstract] | |
| Entity Registrant Name | MKS INSTRUMENTS INC |
| Amendment Flag | false |
| Entity Central Index Key | 0001049502 |
| Document Type | 8-K |
| Document Period End Date | Feb. 8, 2021 |
| Entity Incorporation State Country Code | MA |
| Entity File Number | 000-23621 |
| Entity Tax Identification Number | 04-2277512 |
| Entity Address, Address Line One | 2 Tech Drive |
| Entity Address, Address Line Two | Suite 201 |
| Entity Address, City or Town | Andover |
| Entity Address, State or Province | MA |
| Entity Address, Postal Zip Code | 01810 |
| City Area Code | (978) |
| Local Phone Number | 645-5500 |
| Written Communications | true |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, no par value |
| Trading Symbol | MKSI |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
