Reclassifications Out of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	$ 732,573
Total amount reclassified from accumulated other comprehensive loss, net of tax, into net income	216	$ 15,261	$ 774
Reclassification to retained earnings due to the adoption of ASU 2018-02 (Note 1)	31,765	8,623	(47,470)
Balance at end of period	809,891	732,573
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	(124,848)	(115,517)	(97,948)
Tax benefit	1,997	5,847	9,936
Total other comprehensive loss before reclassifications, net of tax	(4,325)	(13,632)	(28,041)
Tax benefit	(4,242)	(2,775)	(3,611)
Total amount reclassified from accumulated other comprehensive loss, net of tax, into net income	13,621	8,073	10,472
Total other comprehensive income (loss)	0	(3,772)	0
Reclassification to retained earnings due to the adoption of ASU 2018-02 (Note 1)	9,296	(9,331)	(17,569)
Balance at end of period	(115,552)	(124,848)	(115,517)
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)	(6,322)	(19,479)	(37,977)
Amounts reclassified from accumulated other comprehensive loss	18,079	11,028	14,507
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	(216)	(180)	(424)
MSA Safety Incorporated - Net investment gain (loss)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	6	(572)	0
Reclassification to retained earnings due to the adoption of ASU 2018-02 (Note 1)	(7)	578	(572)
Balance at end of period	(1)	6	(572)
MSA Safety Incorporated - Foreign currency translation
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(89,161)	(102,838)	(73,814)
Total amount reclassified from accumulated other comprehensive loss, net of tax, into net income	(216)	(15,261)	(774)
Reclassification to retained earnings due to the adoption of ASU 2018-02 (Note 1)	22,101	(1,584)	(29,798)
Balance at end of period	(66,844)	(89,161)	(102,838)
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	0	0	0
Total other comprehensive loss 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 income (loss)	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	423	496	801
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)	159	(73)	(305)
Balance at end of period	$ 582	$ 423	$ 496