Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 27, 2020	Jun. 28, 2020	Mar. 29, 2020	Dec. 31, 2019	Sep. 29, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Net income attributable to MTI	$ 31.1	$ 28.3	$ 14.4	$ 38.6	$ 29.0	$ 38.0	$ 26.6	$ 39.1	$ 112.4	$ 132.7	$ 169.0
Weighted average shares outstanding (in shares)									34,200,000	35,000,000.0	35,300,000
Dilutive effect of stock options and stock units (in shares)									0	100,000	300,000
Weighted average shares outstanding, adjusted (in shares)									34,200,000	35,100,000	35,600,000
Basic earnings per share attributable to MTI (in dollars per share)	$ 0.91	$ 0.83	$ 0.42	$ 1.12	$ 0.83	$ 1.09	$ 0.76	$ 1.11	$ 3.29	$ 3.79	$ 4.79
Diluted earnings per share attributable to MTI (in dollars per share)	$ 0.91	$ 0.83	$ 0.42	$ 1.12	$ 0.83	$ 1.08	$ 0.75	$ 1.11	$ 3.29	$ 3.78	$ 4.75
Stock Options [Member]
Earnings per Share [Abstract]
Options outstanding (in shares)	1,363,366				1,227,620				1,363,366	1,227,620	1,054,259
Anti-dilutive securities not included in the weighted average commons shares outstanding calculation (in shares)									591,322	825,331	568,284