Revenue from Contracts with Customers (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 28, 2020	Jun. 30, 2019	Jun. 28, 2020	Jun. 30, 2019
Disaggregation of Revenue [Abstract]
Total net sales	$ 357.2	$ 463.8	$ 774.7	$ 901.5
Performance Materials [Member]
Disaggregation of Revenue [Abstract]
Total net sales	173.8	215.4	360.0	414.6
Performance Materials [Member] | Metalcasting [Member]
Disaggregation of Revenue [Abstract]
Total net sales	52.8	75.8	114.5	149.0
Performance Materials [Member] | Household, Personal Care & Specialty Products [Member]
Disaggregation of Revenue [Abstract]
Total net sales	87.9	91.5	184.1	186.3
Performance Materials [Member] | Environmental Products [Member]
Disaggregation of Revenue [Abstract]
Total net sales	19.9	29.0	31.4	44.9
Performance Materials [Member] | Building Materials [Member]
Disaggregation of Revenue [Abstract]
Total net sales	13.2	19.1	30.0	34.4
Specialty Minerals [Member]
Disaggregation of Revenue [Abstract]
Total net sales	109.8	145.1	246.9	289.5
Specialty Minerals [Member] | Paper PCC [Member]
Disaggregation of Revenue [Abstract]
Total net sales	65.5	90.2	150.6	181.7
Specialty Minerals [Member] | Specialty PCC [Member]
Disaggregation of Revenue [Abstract]
Total net sales	14.9	17.3	32.4	35.4
Specialty Minerals [Member] | Ground Calcium Carbonate [Member]
Disaggregation of Revenue [Abstract]
Total net sales	20.6	24.8	43.2	47.1
Specialty Minerals [Member] | Talc [Member]
Disaggregation of Revenue [Abstract]
Total net sales	8.8	12.8	20.7	25.3
Refractories [Member]
Disaggregation of Revenue [Abstract]
Total net sales	55.9	77.5	124.9	151.3
Refractories [Member] | Refractory Products [Member]
Disaggregation of Revenue [Abstract]
Total net sales	47.1	61.0	102.9	123.0
Refractories [Member] | Metallurgical Products [Member]
Disaggregation of Revenue [Abstract]
Total net sales	8.8	16.5	22.0	28.3
Energy Services [Member]
Disaggregation of Revenue [Abstract]
Total net sales	$ 17.7	$ 25.8	$ 42.9	$ 46.1