Revenue from Contracts with Customers (Details) - USD ($) $ in Millions	3 Months Ended					12 Months Ended
	Apr. 04, 2021	Dec. 31, 2020	Sep. 27, 2020	Jun. 28, 2020	Mar. 29, 2020	Dec. 31, 2020
Disaggregation of Revenue [Abstract]
Total net sales	$ 452.6				$ 417.5
Metalcasting [Member]
Disaggregation of Revenue [Abstract]
Total net sales	81.7				61.7
Household, Personal Care & Specialty Products [Member]
Disaggregation of Revenue [Abstract]
Total net sales	109.4				96.2
Environmental Products [Member]
Disaggregation of Revenue [Abstract]
Total net sales	26.0				36.7
Building Materials [Member]
Disaggregation of Revenue [Abstract]
Total net sales	13.8				16.8
Paper PCC [Member]
Disaggregation of Revenue [Abstract]
Total net sales	89.6				85.1
Specialty PCC [Member]
Disaggregation of Revenue [Abstract]
Total net sales	20.4				17.5
Ground Calcium Carbonate [Member]
Disaggregation of Revenue [Abstract]
Total net sales	24.0				22.6
Talc [Member]
Disaggregation of Revenue [Abstract]
Total net sales	13.8				11.9
Refractory Products [Member]
Disaggregation of Revenue [Abstract]
Total net sales	58.8				55.8
Metallurgical Products [Member]
Disaggregation of Revenue [Abstract]
Total net sales	15.1				13.2
Performance Materials [Member]
Disaggregation of Revenue [Abstract]
Total net sales	230.9	$ 219.0	$ 203.9	$ 191.5	211.4	$ 825.8
Performance Materials [Member] | Metalcasting [Member]
Disaggregation of Revenue [Abstract]
Total net sales	81.7	77.3	66.3	52.8	61.7	258.1
Performance Materials [Member] | Household, Personal Care & Specialty Products [Member]
Disaggregation of Revenue [Abstract]
Total net sales	109.4	102.2	93.9	87.9	96.2	380.2
Performance Materials [Member] | Environmental Products [Member]
Disaggregation of Revenue [Abstract]
Total net sales	26.0	27.1	30.2	37.6	36.7	131.6
Performance Materials [Member] | Building Materials [Member]
Disaggregation of Revenue [Abstract]
Total net sales	13.8	$ 12.4	$ 13.5	$ 13.2	16.8	$ 55.9
Specialty Minerals [Member]
Disaggregation of Revenue [Abstract]
Total net sales	147.8				137.1
Specialty Minerals [Member] | Paper PCC [Member]
Disaggregation of Revenue [Abstract]
Total net sales	89.6				85.1
Specialty Minerals [Member] | Specialty PCC [Member]
Disaggregation of Revenue [Abstract]
Total net sales	20.4				17.5
Specialty Minerals [Member] | Ground Calcium Carbonate [Member]
Disaggregation of Revenue [Abstract]
Total net sales	24.0				22.6
Specialty Minerals [Member] | Talc [Member]
Disaggregation of Revenue [Abstract]
Total net sales	13.8				11.9
Refractories [Member]
Disaggregation of Revenue [Abstract]
Total net sales	73.9				69.0
Refractories [Member] | Refractory Products [Member]
Disaggregation of Revenue [Abstract]
Total net sales	58.8				55.8
Refractories [Member] | Metallurgical Products [Member]
Disaggregation of Revenue [Abstract]
Total net sales	$ 15.1				$ 13.2