Segment and Related Information, Sales By Product Category (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jul. 03, 2016	Jun. 28, 2015	Jul. 03, 2016	Jun. 28, 2015
Revenue from External Customer [Line Items]
Net Sales	$ 427.0	$ 463.4	$ 837.2	$ 916.7
Paper PCC [Member]
Revenue from External Customer [Line Items]
Net Sales	97.0	104.7	200.2	209.9
Specialty PCC [Member]
Revenue from External Customer [Line Items]
Net Sales	17.1	16.2	33.8	32.7
Talc [Member]
Revenue from External Customer [Line Items]
Net Sales	13.8	14.2	28.8	28.0
Ground Calcium Carbonate [Member]
Revenue from External Customer [Line Items]
Net Sales	22.7	21.4	43.4	39.9
Refractory Products [Member]
Revenue from External Customer [Line Items]
Net Sales	58.9	59.5	112.3	117.8
Metallurgical Products [Member]
Revenue from External Customer [Line Items]
Net Sales	15.0	16.9	30.8	32.5
Metalcasting [Member]
Revenue from External Customer [Line Items]
Net Sales	68.0	71.6	128.0	136.8
Household, Personal Care and Specialty Products [Member]
Revenue from External Customer [Line Items]
Net Sales	44.0	41.7	89.3	83.5
Basic Minerals and Other Products [Member]
Revenue from External Customer [Line Items]
Net Sales	16.6	15.8	30.3	36.7
Environmental Products [Member]
Revenue from External Customer [Line Items]
Net Sales	26.5	22.1	39.9	33.5
Building Materials and Other Products [Member]
Revenue from External Customer [Line Items]
Net Sales	27.4	30.0	54.6	57.5
Energy Services [Member]
Revenue from External Customer [Line Items]
Net Sales	$ 20.0	$ 49.3	$ 45.8	$ 107.9