| Cover Page Document | Jun. 24, 2021 |
| Cover [Abstract] | |
| Entity Incorporation, State or Country Code | PA |
| Document Type | 8-K |
| City Area Code | 724 |
| Title of 12(b) Security | Common stock, no par value |
| Pre-commencement Issuer Tender Offer | false |
| Pre-commencement Tender Offer | false |
| Soliciting Material | false |
| Written Communications | false |
| Amendment Flag | false |
| Entity Central Index Key | 0000066570 |
| Entity File Number | 1-15579 |
| Entity Tax Identification Number | 46-4914539 |
| Trading Symbol | MSA |
| Security Exchange Name | NYSE |
| Local Phone Number | 776-8600 |
| Entity Emerging Growth Company | false |
| Document Period End Date | Jun. 24, 2021 |
| Entity Registrant Name | MSA SAFETY INCORPORATED |
| Entity Address, Address Line One | 1000 Cranberry Woods Drive |
| Entity Address, City or Town | Cranberry Township, |
| Entity Address, State or Province | PA |
| Entity Address, Postal Zip Code | 16066-5207 |
