Inventories - Effect of Change in Accounting Method, Retrospective Application (Detail) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021		Dec. 31, 2020		Dec. 31, 2019
Consolidated Statements of Income
Cost of products sold			$ 190,758	$ 188,289	$ 173,643		$ 170,254	$ 172,693	$ 183,697	$ 784,834	[1]	$ 752,731	[1]	$ 763,352	[1]
Income before income taxes			30,904	35,256	46,385		41,867	47,984	56,986	23,604	[1]	168,147	[1]	185,752	[1]
(Benefit) Provision for income taxes			9,724	9,808	9,749		12,286	11,468	13,116	1,816	[1]	43,009	[1]	46,545	[1]
Net income			21,180	25,448	36,636		29,581	36,516	43,870	21,788	[1],[2]	125,138	[2],[3]	139,207	[2],[3]
Net income (loss) attributable to MSA Safety Incorporated		$ (61,476)	$ 21,180	$ 25,186	$ 36,450	$ 14,778	$ 29,381	$ 36,176	$ 43,742	$ 21,340	[1]	$ 124,077	[1]	$ 137,998	[1]
Basic (in dollars per share)		$ (1.57)	$ 0.54	$ 0.64	$ 0.93	$ 0.39	$ 0.75	$ 0.93	$ 1.12	$ 0.54	[1]	$ 3.19	[1]	$ 3.56	[1]
Diluted (in dollars per share)		$ (1.57)	$ 0.54	$ 0.64	$ 0.92	$ 0.38	$ 0.74	$ 0.92	$ 1.11	$ 0.54	[1]	$ 3.15	[1]	$ 3.52	[1]
Consolidated Statements of Comprehensive Income
Net income			$ 21,180	$ 25,448	$ 36,636		$ 29,581	$ 36,516	$ 43,870	$ 21,788	[1],[2]	$ 125,138	[2],[3]	$ 139,207	[2],[3]
Total comprehensive income attributable to MSA Safety Incorporated	[3]									54,597		155,683		146,694
Consolidated Balance Sheets
Inventories	[4]	$ 280,617				$ 244,966				280,617		244,966
Deferred tax liabilities	[4]	33,337				20,760				33,337		20,760
Retained earnings	[4]	1,050,214				1,103,092				1,050,214		1,103,092
Consolidated Statements of Cash Flows
Net income			21,180	25,448	36,636		29,581	36,516	43,870	21,788	[1],[2]	125,138	[2],[3]	139,207	[2],[3]
Deferred income tax (benefit) provision	[2]									(38,850)		(2,254)		1,731
Inventories	[2]									(17,827)		(13,645)		(25,263)
As originally reported
Consolidated Statements of Income
Cost of products sold			194,199	188,374	173,688		172,160	172,853	183,786	792,410		757,775		765,369
Income before income taxes			27,463	35,171	46,340		39,961	47,824	56,897	16,028		163,103		183,735
(Benefit) Provision for income taxes			8,640	9,784	9,740		11,727	11,429	13,095	(40)		41,941		46,086
Net income			18,823	25,387	36,600		28,234	36,395	43,802	16,068		121,162		137,649
Net income (loss) attributable to MSA Safety Incorporated			$ 18,823	$ 25,125	$ 36,414		$ 28,034	$ 36,055	$ 43,674	$ 15,620		$ 120,101		$ 136,440
Basic (in dollars per share)			$ 0.48	$ 0.64	$ 0.93		$ 0.72	$ 0.93	$ 1.12	$ 0.39		$ 3.09		$ 3.52
Diluted (in dollars per share)			$ 0.48	$ 0.64	$ 0.92		$ 0.71	$ 0.92	$ 1.11	$ 0.39		$ 3.05		$ 3.48
Consolidated Statements of Comprehensive Income
Net income			$ 18,823	$ 25,387	$ 36,600		$ 28,234	$ 36,395	$ 43,802	$ 16,068		$ 121,162		$ 137,649
Total comprehensive income attributable to MSA Safety Incorporated										48,877		151,707		145,136
Consolidated Balance Sheets
Inventories		225,894				197,819				225,894		197,819
Deferred tax liabilities		21,637				10,916				21,637		10,916
Retained earnings		1,007,191				1,065,789				1,007,191		1,065,789
Consolidated Statements of Cash Flows
Net income			18,823	25,387	36,600		28,234	36,395	43,802	16,068		121,162		137,649
Deferred income tax (benefit) provision										(40,706)		(3,322)		1,272
Inventories										(10,251)		(8,601)		(23,246)
Effect of Change
Consolidated Statements of Income
Cost of products sold			(3,441)	(85)	(45)		(1,906)	(160)	(89)	(7,576)		(5,044)		(2,017)
Income before income taxes			3,441	85	45		1,906	160	89	7,576		5,044		2,017
(Benefit) Provision for income taxes			1,084	24	9		559	39	21	1,856		1,068		459
Net income			2,357	61	36		1,347	121	68	5,720		3,976		1,558
Net income (loss) attributable to MSA Safety Incorporated			$ 2,357	$ 61	$ 36		$ 1,347	$ 121	$ 68	$ 5,720		$ 3,976		$ 1,558
Basic (in dollars per share)			$ 0.06	$ 0	$ 0		$ 0.03	$ 0	$ 0	$ 0.15		$ 0.10		$ 0.04
Diluted (in dollars per share)			$ 0.06	$ 0	$ 0		$ 0.03	$ 0	$ 0	$ 0.15		$ 0.10		$ 0.04
Consolidated Statements of Comprehensive Income
Net income			$ 2,357	$ 61	$ 36		$ 1,347	$ 121	$ 68	$ 5,720		$ 3,976		$ 1,558
Total comprehensive income attributable to MSA Safety Incorporated										5,720		3,976		1,558
Consolidated Balance Sheets
Inventories		54,723				47,147				54,723		47,147
Deferred tax liabilities		11,700				9,844				11,700		9,844
Retained earnings		$ 43,023				$ 37,303				43,023		37,303
Consolidated Statements of Cash Flows
Net income			$ 2,357	$ 61	$ 36		$ 1,347	$ 121	$ 68	5,720		3,976		1,558
Deferred income tax (benefit) provision										1,856		1,068		459
Inventories										$ (7,576)		$ (5,044)		$ (2,017)

[1] *Year ended December 31, 2020 and 2019 amounts have been adjusted to reflect the change in inventory accounting method, as described in Notes 1 and 4 to the consolidated financial statements.

[2] *Year ended December 31, 2020 and 2019 have been adjusted to reflect the change in inventory accounting method, as described in Notes 1 and 4.

[3] *Year ended December 31, 2020 and 2019 amounts have been adjusted to reflect the change in inventory accounting method, as described in Notes 1 and 4 to the consolidated financial statements.

[4] *December 31, 2020 amounts have been adjusted to reflect the change in inventory accounting method, as described in Notes 1 and 4 to the consolidated financial statements.