Cover - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2019	Feb. 17, 2020	Jun. 30, 2019
Cover page.
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity File Number	1-15579
Entity Registrant Name	MSA SAFETY INC
Entity Incorporation, State or Country Code	PA
Entity Tax Identification Number	46-4914539
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
City Area Code	724
Local Phone Number	776-8600
Title of 12(b) Security	Common Stock, no par value
Trading Symbol	MSA
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 3.7
Entity Common Stock, Shares Outstanding (in shares)		38,858,321
Entity Central Index Key	0000066570
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Amendment Flag	false