Revenue from Contracts with Customers (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jul. 01, 2018	Jun. 30, 2019	Jul. 01, 2018
Disaggregation of Revenue [Abstract]
Total net sales	$ 463.8	$ 464.7	$ 901.5	$ 896.0
Performance Materials [Member]
Disaggregation of Revenue [Abstract]
Total net sales	215.4	214.5	414.6	401.8
Performance Materials [Member] | Metalcasting [Member]
Disaggregation of Revenue [Abstract]
Total net sales	75.8	88.8	149.0	168.0
Performance Materials [Member] | Household, Personal Care & Specialty Products [Member]
Disaggregation of Revenue [Abstract]
Total net sales	69.0	58.6	143.9	107.3
Performance Materials [Member] | Environmental Products [Member]
Disaggregation of Revenue [Abstract]
Total net sales	29.0	25.2	44.9	37.9
Performance Materials [Member] | Building Materials [Member]
Disaggregation of Revenue [Abstract]
Total net sales	19.1	18.0	34.4	36.9
Performance Materials [Member] | Basic Minerals [Member]
Disaggregation of Revenue [Abstract]
Total net sales	22.5	23.9	42.4	51.7
Specialty Minerals [Member]
Disaggregation of Revenue [Abstract]
Total net sales	145.1	150.9	289.5	300.5
Specialty Minerals [Member] | Paper PCC [Member]
Disaggregation of Revenue [Abstract]
Total net sales	90.2	94.5	181.7	191.5
Specialty Minerals [Member] | Specialty PCC [Member]
Disaggregation of Revenue [Abstract]
Total net sales	17.3	17.3	35.4	34.3
Specialty Minerals [Member] | Ground Calcium Carbonate [Member]
Disaggregation of Revenue [Abstract]
Total net sales	24.8	25.2	47.1	47.7
Specialty Minerals [Member] | Talc [Member]
Disaggregation of Revenue [Abstract]
Total net sales	12.8	13.9	25.3	27.0
Refractories [Member]
Disaggregation of Revenue [Abstract]
Total net sales	77.5	79.6	151.3	154.9
Refractories [Member] | Refractory Products [Member]
Disaggregation of Revenue [Abstract]
Total net sales	61.0	66.7	123.0	129.0
Refractories [Member] | Metallurgical Products [Member]
Disaggregation of Revenue [Abstract]
Total net sales	16.5	12.9	28.3	25.9
Energy Services [Member]
Disaggregation of Revenue [Abstract]
Total net sales	$ 25.8	$ 19.7	$ 46.1	$ 38.8