Segment and Related Information, Sales by Product Category (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jul. 01, 2018	Apr. 01, 2018	Dec. 31, 2017	Oct. 01, 2017	Jul. 02, 2017	Apr. 02, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue from External Customer [Abstract]
Net sales	$ 447.5	$ 464.1	$ 464.7	$ 431.3	$ 432.1	$ 424.5	$ 414.1	$ 405.0	$ 1,807.6	$ 1,675.7	$ 1,638.0
Metalcasting [Member]
Revenue from External Customer [Abstract]
Net sales									328.9	294.3	258.0
Household, Personal Care & Specialty Products [Member]
Revenue from External Customer [Abstract]
Net sales									248.8	169.6	171.2
Environmental Products [Member]
Revenue from External Customer [Abstract]
Net sales									80.3	67.7	78.9
Building Materials [Member]
Revenue from External Customer [Abstract]
Net sales									70.4	78.2	74.1
Basic Minerals [Member]
Revenue from External Customer [Abstract]
Net sales									99.7	125.0	103.9
Paper PCC [Member]
Revenue from External Customer [Abstract]
Net sales									378.5	377.7	387.9
Specialty PCC [Member]
Revenue from External Customer [Abstract]
Net sales									66.9	66.0	64.3
Ground Calcium Carbonate [Member]
Revenue from External Customer [Abstract]
Net sales									91.0	87.3	83.6
Talc [Member]
Revenue from External Customer [Abstract]
Net sales									52.9	53.8	55.7
Refractory Products [Member]
Revenue from External Customer [Abstract]
Net sales									261.1	226.9	219.0
Metallurgical Products [Member]
Revenue from External Customer [Abstract]
Net sales									50.8	52.5	55.5
Energy Services [Member]
Revenue from External Customer [Abstract]
Net sales									$ 78.3	$ 76.7	$ 85.9