Revenue from Contracts with Customers (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jul. 01, 2018	Jul. 02, 2017	Jul. 01, 2018	Jul. 02, 2017
Disaggregation of Revenue [Abstract]
Net Sales	$ 464.7	$ 414.1	$ 896.0	$ 819.1
Metalcasting [Member]
Disaggregation of Revenue [Abstract]
Net Sales	88.8	75.7	168.0	142.3
Household, Personal Care & Specialty Products [Member]
Disaggregation of Revenue [Abstract]
Net Sales	58.6	39.7	107.3	80.8
Environmental Products [Member]
Disaggregation of Revenue [Abstract]
Net Sales	25.2	19.6	37.9	30.2
Building Materials [Member]
Disaggregation of Revenue [Abstract]
Net Sales	18.0	20.2	36.9	37.6
Basic Minerals [Member]
Disaggregation of Revenue [Abstract]
Net Sales	23.9	25.1	51.7	59.3
Paper PCC [Member]
Disaggregation of Revenue [Abstract]
Net Sales	94.5	92.3	191.5	185.7
Specialty PCC [Member]
Disaggregation of Revenue [Abstract]
Net Sales	17.3	17.4	34.3	34.4
Ground Calcium Carbonate [Member]
Disaggregation of Revenue [Abstract]
Net Sales	25.2	23.3	47.7	44.8
Talc [Member]
Disaggregation of Revenue [Abstract]
Net Sales	13.9	14.0	27.0	28.3
Refractory Products [Member]
Disaggregation of Revenue [Abstract]
Net Sales	66.7	56.1	129.0	112.8
Metallurgical Products [Member]
Disaggregation of Revenue [Abstract]
Net Sales	12.9	12.8	25.9	26.3
Performance Materials [Member]
Disaggregation of Revenue [Abstract]
Net Sales	214.5	180.3	401.8	350.2
Performance Materials [Member] | Metalcasting [Member]
Disaggregation of Revenue [Abstract]
Net Sales	88.8	75.7	168.0	142.3
Performance Materials [Member] | Household, Personal Care & Specialty Products [Member]
Disaggregation of Revenue [Abstract]
Net Sales	58.6	39.7	107.3	80.8
Performance Materials [Member] | Environmental Products [Member]
Disaggregation of Revenue [Abstract]
Net Sales	25.2	19.6	37.9	30.2
Performance Materials [Member] | Building Materials [Member]
Disaggregation of Revenue [Abstract]
Net Sales	18.0	20.2	36.9	37.6
Performance Materials [Member] | Basic Minerals [Member]
Disaggregation of Revenue [Abstract]
Net Sales	23.9	25.1	51.7	59.3
Specialty Minerals [Member]
Disaggregation of Revenue [Abstract]
Net Sales	150.9	147.0	300.5	293.2
Specialty Minerals [Member] | Paper PCC [Member]
Disaggregation of Revenue [Abstract]
Net Sales	94.5	92.3	191.5	185.7
Specialty Minerals [Member] | Specialty PCC [Member]
Disaggregation of Revenue [Abstract]
Net Sales	17.3	17.4	34.3	34.4
Specialty Minerals [Member] | Ground Calcium Carbonate [Member]
Disaggregation of Revenue [Abstract]
Net Sales	25.2	23.3	47.7	44.8
Specialty Minerals [Member] | Talc [Member]
Disaggregation of Revenue [Abstract]
Net Sales	13.9	14.0	27.0	28.3
Refractories [Member]
Disaggregation of Revenue [Abstract]
Net Sales	79.6	68.9	154.9	139.1
Refractories [Member] | Refractory Products [Member]
Disaggregation of Revenue [Abstract]
Net Sales	66.7	56.1	129.0	112.8
Refractories [Member] | Metallurgical Products [Member]
Disaggregation of Revenue [Abstract]
Net Sales	12.9	12.8	25.9	26.3
Energy Services [Member]
Disaggregation of Revenue [Abstract]
Net Sales	$ 19.7	$ 17.9	$ 38.8	$ 36.6