Quarterly Financial Information (Unaudited) - Schedule of Quarterly Financial Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021		Dec. 31, 2020		Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Net sales	$ 410,268	$ 340,197	$ 341,289	$ 308,428	$ 388,248	$ 304,392	$ 314,438	$ 341,145	$ 1,400,182		$ 1,348,223		$ 1,401,981
Gross profit	178,124	149,439	153,000	134,785	162,161	134,138	141,745	157,448	615,348	[1]	595,492	[1]	638,629	[1]
Net income (loss) attributable to MSA Safety Incorporated	$ (61,476)	$ 21,180	$ 25,186	$ 36,450	$ 14,778	$ 29,381	$ 36,176	$ 43,742	$ 21,340	[1]	$ 124,077	[1]	$ 137,998	[1]
Earnings per share
Basic (in dollars per share)	$ (1.57)	$ 0.54	$ 0.64	$ 0.93	$ 0.39	$ 0.75	$ 0.93	$ 1.12	$ 0.54	[1]	$ 3.19	[1]	$ 3.56	[1]
Diluted (in dollars per share)	$ (1.57)	$ 0.54	$ 0.64	$ 0.92	$ 0.38	$ 0.74	$ 0.92	$ 1.11	$ 0.54	[1]	$ 3.15	[1]	$ 3.52	[1]

[1] *Year ended December 31, 2020 and 2019 amounts have been adjusted to reflect the change in inventory accounting method, as described in Notes 1 and 4 to the consolidated financial statements.