Earnings per Share (EPS) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 28, 2020	Jun. 30, 2019	Jun. 28, 2020	Jun. 30, 2019
Earnings per Share [Abstract]
Net income attributable to Minerals Technologies Inc.	$ 14.4	$ 26.6	$ 53.0	$ 65.7
Weighted average shares outstanding (in shares)	34,100,000	35,200,000	34,200,000	35,200,000
Dilutive effect of stock options and stock units (in shares)	0	100,000	100,000	100,000
Weighted average shares outstanding, adjusted (in shares)	34,100,000	35,300,000	34,300,000	35,300,000
Basic earnings per share attributable to Minerals Technologies Inc. (in dollars per share)	$ 0.42	$ 0.76	$ 1.55	$ 1.87
Diluted earnings per share attributable to Minerals Technologies Inc. (in dollars per share)	$ 0.42	$ 0.75	$ 1.55	$ 1.86
Stock Options [Member]
Earnings per Share [Abstract]
Anti-dilutive securities not included in the weighted average commons shares outstanding calculation (in shares)	1,448,699	470,304	1,448,699	470,304