Segment and Related Information (Sales by Product Category) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Oct. 02, 2011	Jul. 03, 2011	Apr. 03, 2011	Dec. 31, 2010	Oct. 03, 2010	Jul. 04, 2010	Apr. 04, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Revenue from External Customer [Line Items]
Net sales	$ 251,700	$ 262,200	$ 268,400	$ 262,500	$ 243,300	$ 249,800	$ 255,800	$ 253,500	$ 1,044,853	$ 1,002,354	$ 907,321
Paper PCC [Member]
Revenue from External Customer [Line Items]
Net sales									497,000	496,600	484,600
Specialty PCC [Member]
Revenue from External Customer [Line Items]
Net sales									63,600	58,000	50,100
Talc [Member]
Revenue from External Customer [Line Items]
Net sales									46,900	44,000	32,300
Ground Calcium Carbonate [Member]
Revenue from External Customer [Line Items]
Net sales									68,600	66,400	61,400
Refractory Products [Member]
Revenue from External Customer [Line Items]
Net sales									287,400	264,500	225,400
Metallurgical Products [Member]
Revenue from External Customer [Line Items]
Net sales									$ 81,400	$ 72,900	$ 53,500