Revenue from Contracts with Customers (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 27, 2020	Jun. 28, 2020	Mar. 29, 2020	Dec. 31, 2019	Sep. 29, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Abstract]
Net Sales	$ 431.8	$ 388.3	$ 357.2	$ 417.5	$ 440.2	$ 449.3	$ 463.8	$ 437.7	$ 1,594.8	$ 1,791.0	$ 1,807.6
Metalcasting [Member]
Disaggregation of Revenue [Abstract]
Net Sales									258.1	291.2	328.9
Household, Personal Care and Specialty Products [Member]
Disaggregation of Revenue [Abstract]
Net Sales									380.2	376.6	348.5
Environmental Products [Member]
Disaggregation of Revenue [Abstract]
Net Sales									58.6	86.6	80.3
Building Materials [Member]
Disaggregation of Revenue [Abstract]
Net Sales									55.9	68.9	70.4
Paper PCC [Member]
Disaggregation of Revenue [Abstract]
Net Sales									308.4	364.9	378.5
Specialty PCC [Member]
Disaggregation of Revenue [Abstract]
Net Sales									69.3	69.1	66.9
Ground Calcium Carbonate [Member]
Disaggregation of Revenue [Abstract]
Net Sales									89.3	91.3	91.0
Talc [Member]
Disaggregation of Revenue [Abstract]
Net Sales									43.9	49.1	52.9
Refractory Products [Member]
Disaggregation of Revenue [Abstract]
Net Sales									212.3	244.8	261.1
Metallurgical Products [Member]
Disaggregation of Revenue [Abstract]
Net Sales									45.8	53.3	50.8
Performance Materials [Member]
Disaggregation of Revenue [Abstract]
Net Sales	202.2	190.6	173.8	186.2	201.4	207.3	215.4	199.2	752.8	823.3	828.1
Performance Materials [Member] | Metalcasting [Member]
Disaggregation of Revenue [Abstract]
Net Sales									258.1	291.2	328.9
Performance Materials [Member] | Household, Personal Care and Specialty Products [Member]
Disaggregation of Revenue [Abstract]
Net Sales									380.2	376.6	348.5
Performance Materials [Member] | Environmental Products [Member]
Disaggregation of Revenue [Abstract]
Net Sales									58.6	86.6	80.3
Performance Materials [Member] | Building Materials [Member]
Disaggregation of Revenue [Abstract]
Net Sales									55.9	68.9	70.4
Specialty Minerals [Member]
Disaggregation of Revenue [Abstract]
Net Sales	138.9	125.1	109.8	137.1	141.8	143.1	145.1	144.4	510.9	574.4	589.3
Specialty Minerals [Member] | Paper PCC [Member]
Disaggregation of Revenue [Abstract]
Net Sales									308.4	364.9	378.5
Specialty Minerals [Member] | Specialty PCC [Member]
Disaggregation of Revenue [Abstract]
Net Sales									69.3	69.1	66.9
Specialty Minerals [Member] | Ground Calcium Carbonate [Member]
Disaggregation of Revenue [Abstract]
Net Sales									89.3	91.3	91.0
Specialty Minerals [Member] | Talc [Member]
Disaggregation of Revenue [Abstract]
Net Sales									43.9	49.1	52.9
Refractories [Member]
Disaggregation of Revenue [Abstract]
Net Sales	73.9	59.3	55.9	69.0	73.4	73.4	77.5	73.8	258.1	298.1	311.9
Refractories [Member] | Refractory Products [Member]
Disaggregation of Revenue [Abstract]
Net Sales									212.3	244.8	261.1
Refractories [Member] | Metallurgical Products [Member]
Disaggregation of Revenue [Abstract]
Net Sales									45.8	53.3	50.8
Energy Services [Member]
Disaggregation of Revenue [Abstract]
Net Sales	$ 16.8	$ 13.3	$ 17.7	$ 25.2	$ 23.6	$ 25.5	$ 25.8	$ 20.3	$ 73.0	$ 95.2	$ 78.3