Segment and Related Information, Reportable Segments (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 29, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 29, 2019 USD ($) Segment	Sep. 30, 2018 USD ($)
Segment Reporting Information [Abstract]
Number of reportable segments | Segment			4
Net sales	$ 449.3	$ 464.1	$ 1,350.8	$ 1,360.1
Income from operations	53.5	68.2	161.0	193.6
Performance Materials [Member]
Segment Reporting Information [Abstract]
Net sales	207.3	219.5	621.9	621.3
Specialty Minerals [Member]
Segment Reporting Information [Abstract]
Net sales	143.1	146.3	432.6	446.8
Refractories [Member]
Segment Reporting Information [Abstract]
Net sales	73.4	79.1	224.7	234.0
Energy Services [Member]
Segment Reporting Information [Abstract]
Net sales	25.5	19.2	71.6	58.0
Reportable Segments [Member]
Segment Reporting Information [Abstract]
Net sales	449.3	464.1	1,350.8	1,360.1
Income from operations	60.8	69.4	172.3	199.7
Reportable Segments [Member] | Performance Materials [Member]
Segment Reporting Information [Abstract]
Net sales	207.3	219.5	621.9	621.3
Income from operations	26.9	31.8	73.9	87.6
Reportable Segments [Member] | Specialty Minerals [Member]
Segment Reporting Information [Abstract]
Net sales	143.1	146.3	432.6	446.8
Income from operations	21.7	25.0	63.7	74.2
Reportable Segments [Member] | Refractories [Member]
Segment Reporting Information [Abstract]
Net sales	73.4	79.1	224.7	234.0
Income from operations	10.2	11.5	29.4	34.6
Reportable Segments [Member] | Energy Services [Member]
Segment Reporting Information [Abstract]
Net sales	25.5	19.2	71.6	58.0
Income from operations	$ 2.0	$ 1.1	$ 5.3	$ 3.3