Segment and Related Information, Reportable Segments (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($) Segment	Apr. 01, 2018 USD ($)
Segment Reporting Information [Abstract]
Number of reportable segments | Segment	4
Net sales	$ 437.7	$ 431.3
Income from operations	62.0	62.6
Performance Materials [Member]
Segment Reporting Information [Abstract]
Net sales	199.2	187.3
Specialty Minerals [Member]
Segment Reporting Information [Abstract]
Net sales	144.4	149.6
Refractories [Member]
Segment Reporting Information [Abstract]
Net sales	73.8	75.3
Energy Services [Member]
Segment Reporting Information [Abstract]
Net sales	20.3	19.1
Reportable Segments [Member]
Segment Reporting Information [Abstract]
Net sales	437.7	431.3
Income from operations	62.8	64.6
Reportable Segments [Member] | Performance Materials [Member]
Segment Reporting Information [Abstract]
Net sales	199.2	187.3
Income from operations	26.3	26.2
Reportable Segments [Member] | Specialty Minerals [Member]
Segment Reporting Information [Abstract]
Net sales	144.4	149.6
Income from operations	22.0	24.1
Reportable Segments [Member] | Refractories [Member]
Segment Reporting Information [Abstract]
Net sales	73.8	75.3
Income from operations	12.1	12.8
Reportable Segments [Member] | Energy Services [Member]
Segment Reporting Information [Abstract]
Net sales	20.3	19.1
Income from operations	$ 2.4	$ 1.5