Segment and Related Information, Sales By Product Category (Details) - USD ($) $ in Millions	3 Months Ended					9 Months Ended		12 Months Ended
	Oct. 01, 2017	Dec. 31, 2016	Oct. 02, 2016	Jul. 03, 2016	Apr. 03, 2016	Oct. 01, 2017	Oct. 02, 2016	Dec. 31, 2016
Revenue from External Customer [Line Items]
Net Sales	$ 424.4		$ 399.5			$ 1,243.5	$ 1,236.7
Paper PCC [Member]
Revenue from External Customer [Line Items]
Net Sales	96.3		95.3			282.0	295.5
Specialty PCC [Member]
Revenue from External Customer [Line Items]
Net Sales	16.4		16.4			50.8	50.2
Talc [Member]
Revenue from External Customer [Line Items]
Net Sales	12.7		13.9			41.0	42.7
Ground Calcium Carbonate [Member]
Revenue from External Customer [Line Items]
Net Sales	22.3		21.7			67.1	65.1
Refractory Products [Member]
Revenue from External Customer [Line Items]
Net Sales	56.6		51.0			169.4	163.3
Metallurgical Products [Member]
Revenue from External Customer [Line Items]
Net Sales	12.3		12.4			38.6	43.2
Metalcasting [Member]
Revenue from External Customer [Line Items]
Net Sales	73.6	$ 66.9	63.1	$ 68.0	$ 60.0	215.9	191.1	$ 258.0
Household, Personal Care and Specialty Products [Member]
Revenue from External Customer [Line Items]
Net Sales	42.5	39.8	42.1	44.0	45.3	123.3	131.4	171.2
Basic Minerals [Member]
Revenue from External Customer [Line Items]
Net Sales	31.2	36.8	22.3	24.3	20.5	90.5	67.1	103.9
Environmental Products [Member]
Revenue from External Customer [Line Items]
Net Sales	21.6	14.4	24.6	26.5	13.4	51.8	64.5	78.9
Building Materials [Member]
Revenue from External Customer [Line Items]
Net Sales	19.9	$ 17.1	16.9	$ 19.7	$ 20.4	57.5	57.0	$ 74.1
Energy Services [Member]
Revenue from External Customer [Line Items]
Net Sales	$ 19.0		$ 19.8			$ 55.6	$ 65.6