Reclassifications Out of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	$ 639,519
Total amount reclassified from accumulated other comprehensive loss, net of tax, into net income	15,261	$ 774	$ 0
Reclassification to retained earnings due to the adoption of ASU 2018-02 (Note 1)	8,623	(47,470)	61,249
Balance at end of period	732,573	639,519
MSA Safety Incorporated - Pension and other post-retirement benefits
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(115,517)	(97,948)	(118,068)
Tax benefit (expense)	5,847	9,936	(6,124)
Total other comprehensive (loss) income before reclassifications, net of tax	(13,632)	(28,041)	11,535
Tax benefit	(2,775)	(3,611)	(4,293)
Total amount reclassified from accumulated other comprehensive loss, net of tax, into net income	8,073	10,472	8,585
Total other comprehensive (loss) income	(3,772)	0	0
Reclassification to retained earnings due to the adoption of ASU 2018-02 (Note 1)	(9,331)	(17,569)	20,120
Balance at end of period	(124,848)	(115,517)	(97,948)
MSA Safety Incorporated - Net actuarial (losses) gains
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Unrecognized net actuarial losses/prior service credit (cost)	(19,479)	(37,977)	17,659
Amounts reclassified from accumulated other comprehensive loss	11,028	14,507	13,054
MSA Safety Incorporated - Prior service (cost) credit
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Amounts reclassified from accumulated other comprehensive loss	(180)	(424)	(176)
MSA Safety Incorporated - Net investment gain (loss)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(572)	0	0
Reclassification to retained earnings due to the adoption of ASU 2018-02 (Note 1)	578	(572)	0
Balance at end of period	6	(572)	0
MSA Safety Incorporated - Foreign currency translation
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(102,838)	(73,814)	(112,178)
Total amount reclassified from accumulated other comprehensive loss, net of tax, into net income	(15,261)	(774)	0
Reclassification to retained earnings due to the adoption of ASU 2018-02 (Note 1)	(1,584)	(29,798)	38,364
Balance at end of period	(89,161)	(102,838)	(73,814)
Noncontrolling Interests - Pension and other post-retirement benefits
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	0	0	0
Tax benefit (expense)	0	0	0
Total other comprehensive (loss) income before reclassifications, net of tax	0	0	0
Tax benefit	0	0	0
Total amount reclassified from accumulated other comprehensive loss, net of tax, into net income	0	0	0
Total other comprehensive (loss) income	0	0	0
Reclassification to retained earnings due to the adoption of ASU 2018-02 (Note 1)	0	0	0
Balance at end of period	0	0	0
Noncontrolling Interests - Net actuarial (losses) gains
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Unrecognized net actuarial losses/prior service credit (cost)	0	0	0
Amounts reclassified from accumulated other comprehensive loss	0	0	0
Noncontrolling Interests - Prior service credit (cost)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Amounts reclassified from accumulated other comprehensive loss	0	0	0
Noncontrolling Interests - Net investment gain (loss)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	0	0	0
Reclassification to retained earnings due to the adoption of ASU 2018-02 (Note 1)	0	0	0
Balance at end of period	0	0	0
Noncontrolling Interests - Foreign currency translation
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	496	801	(1,964)
Total amount reclassified from accumulated other comprehensive loss, net of tax, into net income	0	0	0
Reclassification to retained earnings due to the adoption of ASU 2018-02 (Note 1)	(73)	(305)	2,765
Balance at end of period	$ 423	$ 496	$ 801