Segment and Related Information (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jul. 01, 2018 USD ($)	Jul. 02, 2017 USD ($)	Jul. 01, 2018 USD ($) Segment	Jul. 02, 2017 USD ($)
Segment Reporting Information [Abstract]
Number of reportable segments | Segment			4
Net Sales	$ 464.7	$ 414.1	$ 896.0	$ 819.1
Income from Operations	62.8	69.0	125.4	131.1
Performance Materials [Member]
Segment Reporting Information [Abstract]
Net Sales	214.5	180.3	401.8	350.2
Specialty Minerals [Member]
Segment Reporting Information [Abstract]
Net Sales	150.9	147.0	300.5	293.2
Refractories [Member]
Segment Reporting Information [Abstract]
Net Sales	79.6	68.9	154.9	139.1
Energy Services [Member]
Segment Reporting Information [Abstract]
Net Sales	19.7	17.9	38.8	36.6
Reportable Segments [Member]
Segment Reporting Information [Abstract]
Net Sales	464.7	414.1	896.0	819.1
Income from Operations	65.7	70.4	130.3	134.5
Reportable Segments [Member] | Performance Materials [Member]
Segment Reporting Information [Abstract]
Net Sales	214.5	180.3	401.8	350.2
Income from Operations	29.6	32.2	55.8	61.0
Reportable Segments [Member] | Specialty Minerals [Member]
Segment Reporting Information [Abstract]
Net Sales	150.9	147.0	300.5	293.2
Income from Operations	25.1	26.9	49.2	51.3
Reportable Segments [Member] | Refractories [Member]
Segment Reporting Information [Abstract]
Net Sales	79.6	68.9	154.9	139.1
Income from Operations	10.3	10.5	23.1	19.7
Reportable Segments [Member] | Energy Services [Member]
Segment Reporting Information [Abstract]
Net Sales	19.7	17.9	38.8	36.6
Income from Operations	$ 0.7	$ 0.8	$ 2.2	$ 2.5