Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 18,823	$ 28,234	$ 80,810	$ 108,431
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments (Note 6)	(13,868)	15,520	(18,073)	(2,758)
Pension and post-retirement plan actuarial gains, net of tax (Note 6)	3,701	3,058	11,070	9,250
Unrealized loss on available-for-sale securities (Note 6)	(11)	(74)	(15)	(12)
Reclassification of currency translation from accumulated other comprehensive loss into net income (Note 6)	0	0	0	720
Total other comprehensive (loss) income, net of tax	(10,178)	18,504	(7,018)	7,200
Comprehensive income	8,645	46,738	73,792	115,631
Less: Comprehensive income attributable to noncontrolling interests	0	(494)	(356)	(865)
Comprehensive income attributable to MSA Safety Incorporated	$ 8,645	$ 46,244	$ 73,436	$ 114,766