Revenue from Contracts with Customers (Details) - USD ($) $ in Millions	3 Months Ended					6 Months Ended		12 Months Ended
	Jul. 04, 2021	Dec. 31, 2020	Sep. 27, 2020	Jun. 28, 2020	Mar. 29, 2020	Jul. 04, 2021	Jun. 28, 2020	Dec. 31, 2020
Disaggregation of Revenue [Abstract]
Total net sales	$ 455.6			$ 357.2		$ 908.2	$ 774.7
Metalcasting [Member]
Disaggregation of Revenue [Abstract]
Total net sales	80.5			52.8		162.2	114.5
Household, Personal Care & Specialty Products [Member]
Disaggregation of Revenue [Abstract]
Total net sales	102.6			87.9		212.0	184.1
Environmental Products [Member]
Disaggregation of Revenue [Abstract]
Total net sales	39.9			37.6		65.9	74.3
Building Materials [Member]
Disaggregation of Revenue [Abstract]
Total net sales	15.4			13.2		29.2	30.0
Paper PCC [Member]
Disaggregation of Revenue [Abstract]
Total net sales	85.8			65.5		175.4	150.6
Specialty PCC [Member]
Disaggregation of Revenue [Abstract]
Total net sales	18.5			14.9		38.9	32.4
Ground Calcium Carbonate [Member]
Disaggregation of Revenue [Abstract]
Total net sales	25.5			20.6		49.5	43.2
Talc [Member]
Disaggregation of Revenue [Abstract]
Total net sales	12.9			8.8		26.7	20.7
Refractory Products [Member]
Disaggregation of Revenue [Abstract]
Total net sales	58.0			47.1		116.8	102.9
Metallurgical Products [Member]
Disaggregation of Revenue [Abstract]
Total net sales	16.5			8.8		31.6	22.0
Performance Materials [Member]
Disaggregation of Revenue [Abstract]
Total net sales	238.4	$ 219.0	$ 203.9	191.5	$ 211.4	469.3	402.9	$ 825.8
Performance Materials [Member] | Metalcasting [Member]
Disaggregation of Revenue [Abstract]
Total net sales	80.5	77.3	66.3	52.8	61.7	162.2	114.5	258.1
Performance Materials [Member] | Household, Personal Care & Specialty Products [Member]
Disaggregation of Revenue [Abstract]
Total net sales	102.6	102.2	93.9	87.9	96.2	212.0	184.1	380.2
Performance Materials [Member] | Environmental Products [Member]
Disaggregation of Revenue [Abstract]
Total net sales	39.9	27.1	30.2	37.6	36.7	65.9	74.3	131.6
Performance Materials [Member] | Building Materials [Member]
Disaggregation of Revenue [Abstract]
Total net sales	15.4	$ 12.4	$ 13.5	13.2	$ 16.8	29.2	30.0	$ 55.9
Specialty Minerals [Member]
Disaggregation of Revenue [Abstract]
Total net sales	142.7			109.8		290.5	246.9
Specialty Minerals [Member] | Paper PCC [Member]
Disaggregation of Revenue [Abstract]
Total net sales	85.8			65.5		175.4	150.6
Specialty Minerals [Member] | Specialty PCC [Member]
Disaggregation of Revenue [Abstract]
Total net sales	18.5			14.9		38.9	32.4
Specialty Minerals [Member] | Ground Calcium Carbonate [Member]
Disaggregation of Revenue [Abstract]
Total net sales	25.5			20.6		49.5	43.2
Specialty Minerals [Member] | Talc [Member]
Disaggregation of Revenue [Abstract]
Total net sales	12.9			8.8		26.7	20.7
Refractories [Member]
Disaggregation of Revenue [Abstract]
Total net sales	74.5			55.9		148.4	124.9
Refractories [Member] | Refractory Products [Member]
Disaggregation of Revenue [Abstract]
Total net sales	58.0			47.1		116.8	102.9
Refractories [Member] | Metallurgical Products [Member]
Disaggregation of Revenue [Abstract]
Total net sales	$ 16.5			$ 8.8		$ 31.6	$ 22.0