Segment and Related Information, Segment Information (Details) $ in Millions	3 Months Ended					9 Months Ended		12 Months Ended
	Oct. 03, 2021 USD ($)	Dec. 31, 2020 USD ($)	Sep. 27, 2020 USD ($)	Jun. 28, 2020 USD ($)	Mar. 29, 2020 USD ($)	Oct. 03, 2021 USD ($) Segment	Sep. 27, 2020 USD ($)	Dec. 31, 2020 USD ($)
Segment and Related Information [Abstract]
Number of reportable segments | Segment						3
Net sales	$ 473.2		$ 388.3			$ 1,381.4	$ 1,163.0
Income from operations	60.6		48.5			183.1	133.4
Performance Materials [Member]
Segment and Related Information [Abstract]
Net sales	250.4	$ 219.0	203.9	$ 191.5	$ 211.4	719.7	606.8	$ 825.8
Income from operations		$ 30.9	28.2	$ 22.4	$ 27.3			$ 108.8
Specialty Minerals [Member]
Segment and Related Information [Abstract]
Net sales	146.9		125.1			437.4	372.0
Refractories [Member]
Segment and Related Information [Abstract]
Net sales	75.9		59.3			224.3	184.2
Reportable Segments [Member]
Segment and Related Information [Abstract]
Net sales	473.2		388.3			1,381.4	1,163.0
Income from operations	62.5		52.1			191.8	148.2
Reportable Segments [Member] | Performance Materials [Member]
Segment and Related Information [Abstract]
Net sales	250.4		203.9			719.7	606.8
Income from operations	32.0		28.2			96.5	77.9
Reportable Segments [Member] | Specialty Minerals [Member]
Segment and Related Information [Abstract]
Net sales	146.9		125.1			437.4	372.0
Income from operations	17.3		16.6			58.4	45.9
Reportable Segments [Member] | Refractories [Member]
Segment and Related Information [Abstract]
Net sales	75.9		59.3			224.3	184.2
Income from operations	$ 13.2		$ 7.3			$ 36.9	$ 24.4