Quarterly Financial Data (unaudited) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 28, 2014	Jun. 29, 2014	Mar. 30, 2014	Dec. 31, 2013	Sep. 29, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenue from External Customer [Line Items]
Net sales	$ 516.0	$ 543.5	$ 421.1	$ 244.4	$ 256.8	$ 254.2	$ 256.8	$ 250.4	$ 1,725.0	$ 1,018.2	$ 996.8
Gross profit	132.4	145.0	102.7	55.3	59.0	59.9	58.8	56.0	435.4	233.7	222.3
Income from operations	42.6	66.8	35.8	23.6	33.5	32.8	32.4	28.2	168.8	126.9	113.6
Income from continuing operations	21.9	37.6	17.6	16.3	23.6	22.6	22.7	20.3	90.3	86.1	76.6
Income (loss) from discontinued operations	0.1	0.2	1.8	0	0	0	(5.1)	(0.7)	2.1	(5.8)	(2.5)
Net income attributable to MTI	21.3	37.0	18.5	15.6	22.6	21.9	17.1	18.7	92.4	80.3	74.1
Basic earnings per share attributable to MTI shareholders [Abstract]
Income from continuing operations attributable to MTI (in dollars per share)	$ 0.61	$ 1.07	$ 0.48	$ 0.45	$ 0.66	$ 0.63	$ 0.63	$ 0.56	$ 2.62	$ 2.48	$ 2.17
Income (loss) from discontinued operations attributable to MTI (in dollars per share)	$ 0.01	$ 0	$ 0.05	$ 0	$ 0	$ 0	$ (0.14)	$ (0.02)	$ 0.06	$ (0.17)	$ (0.07)
Net income (in dollars per share)	$ 0.62	$ 1.07	$ 0.53	$ 0.45	$ 0.66	$ 0.63	$ 0.49	$ 0.54	$ 2.68	$ 2.31	$ 2.10
Diluted earnings per share attributable to MTI shareholders [Abstract]
Income from continuing operations attributable to MTI (in dollars per share)	$ 0.61	$ 1.06	$ 0.48	$ 0.45	$ 0.65	$ 0.63	$ 0.63	$ 0.55	$ 2.59	$ 2.46	$ 2.16
Loss from discontinued operations attributable to MTI (in dollars per share)	$ 0	$ 0	$ 0.05	$ 0	$ 0	$ 0	$ (0.14)	$ (0.02)	$ 0.06	$ (0.16)	$ (0.07)
Net Income attributable to MTI common shareholders (in dollars per share)	$ 0.61	$ 1.06	$ 0.53	$ 0.45	$ 0.65	$ 0.63	$ 0.49	$ 0.53	$ 2.65	$ 2.30	$ 2.09
Market price range per share of common stock [Abstract]
High (in dollars per share)	$ 77.40	$ 67.02	$ 66.50	$ 64.48	$ 60.40	$ 49.03	$ 43.12	$ 43.04
Low (in dollars per share)	$ 58.06	$ 57.14	$ 59.49	$ 48.81	$ 49.28	$ 42.53	$ 38.43	$ 39.54
Close (in dollars per share)	$ 69.45	$ 63.45	$ 65.01	$ 63.57	$ 60.07	$ 48.95	$ 41.34	$ 41.51	$ 69.45	$ 60.07
Dividends paid per common share (in dollars per share)	$ 0.05	$ 0.05	$ 0.05	$ 0.05	$ 0.050	$ 0.050	$ 0.050	$ 0.050	$ 0.20
Specialty Minerals [Member]
Revenue from External Customer [Line Items]
Net sales	159.6	163.0	167.8	159.7	167.3	167.4	168.3	166.8
Refractories [Member]
Revenue from External Customer [Line Items]
Net sales	92.9	90.4	91.7	84.7	89.5	86.8	88.5	83.6
Performance Materials [Member]
Revenue from External Customer [Line Items]
Net sales	141.4	135.6	75.8	0
Construction Technologies [Member]
Revenue from External Customer [Line Items]
Net sales	46.0	69.1	37.2	0
Energy Services [Member]
Revenue from External Customer [Line Items]
Net sales	$ 76.1	$ 85.4	$ 48.6	$ 0