Segment and Related Information, Sales By Product Category (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jul. 01, 2012	Jun. 30, 2013	Jul. 01, 2012
Revenue from External Customer [Line Items]
Net sales	$ 256,844	$ 251,358	$ 507,357	$ 505,916
Paper PCC [Member]
Revenue from External Customer [Line Items]
Net sales	118,300	116,700	238,800	235,800
Specialty PCC [Member]
Revenue from External Customer [Line Items]
Net sales	17,300	17,000	34,200	33,400
Talc [Member]
Revenue from External Customer [Line Items]
Net sales	13,000	13,100	25,400	25,200
Ground Calcium Carbonate [Member]
Revenue from External Customer [Line Items]
Net sales	19,700	18,700	36,900	36,200
Refractory Products [Member]
Revenue from External Customer [Line Items]
Net sales	67,200	65,400	129,600	134,500
Metallurgical Products [Member]
Revenue from External Customer [Line Items]
Net sales	$ 21,300	$ 20,500	$ 42,500	$ 40,800