Earnings per Share - Schedule of Earnings Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Earnings per share attributable to MSA Safety Incorporated common shareholders:
Net income attributable to continuing operations	$ 9,316	$ 13,522
Preferred stock dividends	(10)	(10)
Income from continuing operations available to common equity	9,306	13,512
Dividends and undistributed earnings allocated to participating securities	(28)	(90)
Income from continuing operations available to common shareholders	9,278	13,422
Net income attributable to discontinued operations	366	504
Preferred stock dividends	0	0
Income from discontinued operations available to common equity	366	504
Dividends and undistributed earnings allocated to participating securities	(1)	(4)
Income from discontinued operations available to common shareholders	$ 365	$ 500
Basic weighted-average shares outstanding	37,356	37,015
Stock options and other stock compensation	493	602
Diluted weighted-average shares outstanding	37,849	37,617
Antidilutive stock options	495	0
Earnings per share attributable to continuing operations:
Income from continuing operations, basic (dollars per share)	$ 0.25	$ 0.37
Income from continuing operations, diluted (dollars per share)	$ 0.25	$ 0.36
Earnings per share attributable to discontinued operations:
Income from discontinued operations, basic (dollars per share)	$ 0.01	$ 0.01
Income from discontinued operations, diluted (dollars per share)	$ 0.01	$ 0.01

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