Segment and Related Information, Sales By Product Category (Details) - USD ($) $ in Millions	3 Months Ended
	Apr. 01, 2018	Apr. 02, 2017
Revenue from External Customer [Line Items]
Net Sales	$ 431.3	$ 405.0
Paper PCC [Member]
Revenue from External Customer [Line Items]
Net Sales	97.0	93.4
Specialty PCC [Member]
Revenue from External Customer [Line Items]
Net Sales	17.0	17.0
Talc [Member]
Revenue from External Customer [Line Items]
Net Sales	13.1	14.3
Ground Calcium Carbonate [Member]
Revenue from External Customer [Line Items]
Net Sales	22.5	21.5
Metalcasting [Member]
Revenue from External Customer [Line Items]
Net Sales	79.2	66.6
Household, Personal Care and Specialty Products [Member]
Revenue from External Customer [Line Items]
Net Sales	48.7	41.1
Environmental Products [Member]
Revenue from External Customer [Line Items]
Net Sales	12.7	10.6
Building Materials [Member]
Revenue from External Customer [Line Items]
Net Sales	18.9	17.4
Basic Minerals [Member]
Revenue from External Customer [Line Items]
Net Sales	27.8	34.2
Refractory Products [Member]
Revenue from External Customer [Line Items]
Net Sales	62.3	56.7
Metallurgical Products [Member]
Revenue from External Customer [Line Items]
Net Sales	13.0	13.5
Energy Services [Member]
Revenue from External Customer [Line Items]
Net Sales	$ 19.1	$ 18.7