Segment and Related Information, Sales by Product Category (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
Revenue from External Customer [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]
Revenue from External Customer [Abstract]
Net sales									258.1	291.2	328.9
Household, Personal Care & Specialty Products [Member]
Revenue from External Customer [Abstract]
Net sales									380.2	376.6	348.5
Environmental Products [Member]
Revenue from External Customer [Abstract]
Net sales									58.6	86.6	80.3
Building Materials [Member]
Revenue from External Customer [Abstract]
Net sales									55.9	68.9	70.4
Paper PCC [Member]
Revenue from External Customer [Abstract]
Net sales									308.4	364.9	378.5
Specialty PCC [Member]
Revenue from External Customer [Abstract]
Net sales									69.3	69.1	66.9
Ground Calcium Carbonate [Member]
Revenue from External Customer [Abstract]
Net sales									89.3	91.3	91.0
Talc [Member]
Revenue from External Customer [Abstract]
Net sales									43.9	49.1	52.9
Refractory Products [Member]
Revenue from External Customer [Abstract]
Net sales									212.3	244.8	261.1
Metallurgical Products [Member]
Revenue from External Customer [Abstract]
Net sales									45.8	53.3	50.8
Energy Services [Member]
Revenue from External Customer [Abstract]
Net sales									$ 73.0	$ 95.2	$ 78.3