Segment and Related Information, Segment Information (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 27, 2020 USD ($)	Sep. 29, 2019 USD ($)	Sep. 27, 2020 USD ($) Segment	Sep. 29, 2019 USD ($)
Segment Reporting Information [Abstract]
Number of reportable segments | Segment			4
Net sales	$ 388.3	$ 449.3	$ 1,163.0	$ 1,350.8
Income from operations	48.5	53.5	133.4	161.0
Performance Materials [Member]
Segment Reporting Information [Abstract]
Net sales	190.6	207.3	550.6	621.9
Specialty Minerals [Member]
Segment Reporting Information [Abstract]
Net sales	125.1	143.1	372.0	432.6
Refractories [Member]
Segment Reporting Information [Abstract]
Net sales	59.3	73.4	184.2	224.7
Energy Services [Member]
Segment Reporting Information [Abstract]
Net sales	13.3	25.5	56.2	71.6
Reportable Segments [Member]
Segment Reporting Information [Abstract]
Net sales	388.3	449.3	1,163.0	1,350.8
Income from operations	52.1	60.8	148.2	172.3
Reportable Segments [Member] | Performance Materials [Member]
Segment Reporting Information [Abstract]
Net sales	190.6	207.3	550.6	621.9
Income from operations	28.2	26.9	73.3	73.9
Reportable Segments [Member] | Specialty Minerals [Member]
Segment Reporting Information [Abstract]
Net sales	125.1	143.1	372.0	432.6
Income from operations	16.6	21.7	45.9	63.7
Reportable Segments [Member] | Refractories [Member]
Segment Reporting Information [Abstract]
Net sales	59.3	73.4	184.2	224.7
Income from operations	7.3	10.2	24.4	29.4
Reportable Segments [Member] | Energy Services [Member]
Segment Reporting Information [Abstract]
Net sales	13.3	25.5	56.2	71.6
Income from operations	$ 0.0	$ 2.0	$ 4.6	$ 5.3