Segment and Related Information, Sales By Product Category (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 29, 2013	Sep. 30, 2012	Sep. 29, 2013	Sep. 30, 2012
Revenue from External Customer [Line Items]
Net sales	$ 254,192	$ 247,803	$ 761,549	$ 753,719
Paper PCC [Member]
Revenue from External Customer [Line Items]
Net sales	119,300	118,100	357,900	353,900
Specialty PCC [Member]
Revenue from External Customer [Line Items]
Net sales	16,600	16,400	50,800	49,800
Talc [Member]
Revenue from External Customer [Line Items]
Net sales	12,800	11,900	38,200	37,100
Ground Calcium Carbonate [Member]
Revenue from External Customer [Line Items]
Net sales	18,700	16,700	55,600	52,900
Refractory Products [Member]
Revenue from External Customer [Line Items]
Net sales	66,300	66,000	195,900	200,500
Metallurgical Products [Member]
Revenue from External Customer [Line Items]
Net sales	$ 20,500	$ 18,700	$ 63,100	$ 59,500