Segment and Related Information (Details) (USD $)	3 Months Ended
	Apr. 01, 2012	Apr. 03, 2011	Dec. 31, 2011
Segment Reporting Information [Line Items]
Net sales	$ 257,138,000	$ 262,520,000
Income from operations	29,000,000	26,200,000
Restructuring costs (reversals)	0	230,000
Goodwill	65,788,000		64,671,000
Income from operations before provision for taxes on income [Abstract]
Income from operations for reportable segments	29,000,000	26,200,000
Unallocated corporate expenses	2,000,000	1,500,000
Income from operations	26,992,000	24,714,000
Non-operating deductions, net	(598,000)	(837,000)
Income from continuing operations before provision for taxes	26,394,000	23,877,000
Revenue from External Customer [Line Items]
Net sales	257,138,000	262,520,000
Paper PCC [Member]
Segment Reporting Information [Line Items]
Net sales	121,700,000	129,200,000
Revenue from External Customer [Line Items]
Net sales	121,700,000	129,200,000
Specialty PCC [Member]
Segment Reporting Information [Line Items]
Net sales	16,400,000	15,600,000
Revenue from External Customer [Line Items]
Net sales	16,400,000	15,600,000
Talc [Member]
Segment Reporting Information [Line Items]
Net sales	12,100,000	11,400,000
Revenue from External Customer [Line Items]
Net sales	12,100,000	11,400,000
Ground Calcium Carbonate [Member]
Segment Reporting Information [Line Items]
Net sales	17,500,000	17,100,000
Revenue from External Customer [Line Items]
Net sales	17,500,000	17,100,000
Refractory Products [Member]
Segment Reporting Information [Line Items]
Net sales	69,100,000	69,600,000
Revenue from External Customer [Line Items]
Net sales	69,100,000	69,600,000
Metallurgical Products [Member]
Segment Reporting Information [Line Items]
Net sales	20,300,000	19,600,000
Revenue from External Customer [Line Items]
Net sales	20,300,000	19,600,000
Specialty Minerals [Member]
Segment Reporting Information [Line Items]
Net sales	167,700,000	173,300,000
Income from operations	19,900,000	19,300,000
Restructuring costs (reversals)		400,000
Goodwill	14,000,000		13,800,000
Income from operations before provision for taxes on income [Abstract]
Income from operations for reportable segments	19,900,000	19,300,000
Revenue from External Customer [Line Items]
Net sales	167,700,000	173,300,000
Refractories [Member]
Segment Reporting Information [Line Items]
Net sales	89,400,000	89,200,000
Income from operations	9,100,000	6,900,000
Restructuring costs (reversals)		(200,000)
Goodwill	51,800,000		50,900,000
Income from operations before provision for taxes on income [Abstract]
Income from operations for reportable segments	9,100,000	6,900,000
Revenue from External Customer [Line Items]
Net sales	$ 89,400,000	$ 89,200,000