Consolidated Statement of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 121,162	$ 137,649	$ 125,115
Foreign currency translation adjustments (Note 5)	22,260	(1,657)	(30,103)
Pension and post-retirement plan actuarial gains (losses), net of tax (Note 5)	9,296	(5,559)	(17,569)
Unrealized (losses) gains on available-for-sale securities (Note 5)	(7)	578	(572)
Reclassifications from accumulated other comprehensive (loss) into net income (Note 5)	216	15,261	774
Total other comprehensive income (loss), net of tax	31,765	8,623	(47,470)
Comprehensive income	152,927	146,272	77,645
Comprehensive income attributable to noncontrolling interests	(1,220)	(1,136)	(660)
Comprehensive income attributable to MSA Safety Incorporated	$ 151,707	$ 145,136	$ 76,985