Earnings Per Share (EPS) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 29, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jul. 01, 2018	Apr. 01, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share (EPS) [Abstract]
Net income attributable to MTI	$ 29.0	$ 38.0	$ 26.6	$ 39.1	$ 43.1	$ 41.9	$ 44.1	$ 39.9	$ 132.7	$ 169.0	$ 195.1
Weighted average shares outstanding (in shares)									35,000,000.0	35,300,000	35,200,000
Dilutive effect of stock options and stock units (in shares)									100,000	300,000	400,000
Weighted average shares outstanding, adjusted (in shares)									35,100,000	35,600,000	35,600,000
Basic earnings per share attributable to MTI (in dollars per share)	$ 0.83	$ 1.09	$ 0.76	$ 1.11	$ 1.22	$ 1.19	$ 1.25	$ 1.13	$ 3.79	$ 4.79	$ 5.54
Diluted earnings per share attributable to MTI (in dollars per share)	$ 0.83	$ 1.08	$ 0.75	$ 1.11	$ 1.22	$ 1.18	$ 1.24	$ 1.12	$ 3.78	$ 4.75	$ 5.48
Stock Options [Member]
Antidilutive Securities Excluded from Earnings Per Share Calculation [Abstract]
Anti-dilutive securities not included in the weighted average commons shares outstanding calculation (in shares)									825,331	568,284	181,003