Consolidated Statement of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 26,956	$ 93,862	$ 67,944
Foreign currency translation adjustments (Note 5)	41,129	(24,986)	(49,067)
Pension and post-retirement plan actuarial gains, net of tax (Note 5)	20,120	1,321	6,181
Reclassification from accumulated other comprehensive (loss) into net income (Note 5)	0	3,270	0
Total other comprehensive income (loss), net of tax	61,249	(20,395)	(42,886)
Comprehensive income	88,205	73,467	25,058
Comprehensive (income) loss attributable to noncontrolling interests	(3,694)	(3,578)	4,280
Comprehensive income attributable to MSA Safety Incorporated	$ 84,511	$ 69,889	$ 29,338