Earnings Per Share (Schedule Of Earnings Per Share) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Earnings Per Share [Abstract]
Net income attributable to Mine Safety Appliances Company	$ 16,979	$ 19,972	$ 19,592	$ 13,309	$ 11,768	$ 9,603	$ 11,827	$ 4,906	$ 69,852	$ 38,104	$ 43,295
Preferred stock dividends									(42)	(42)	(42)
Income available to common equity									69,810	38,062	43,253
Dividends and undistributed earnings allocated to participating securities									(755)	(365)	(327)
Income available to common shareholders									$ 69,055	$ 37,697	$ 42,926
Basic earnings per common share	$ 0.46	$ 0.54	$ 0.53	$ 0.36	$ 0.33	$ 0.27	$ 0.33	$ 0.14	$ 1.91	$ 1.06	$ 1.21
Diluted earnings per common share	$ 0.46	$ 0.54	$ 0.53	$ 0.36	$ 0.32	$ 0.26	$ 0.32	$ 0.14	$ 1.87	$ 1.05	$ 1.21
Basic shares outstanding									36,221	35,880	35,668
Stock options and other stock compensation									610	542	211
Diluted shares outstanding									36,831	36,422	35,879
Antidilutive stock options									894	760	749