Segment and Related Information (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Apr. 01, 2012	Dec. 31, 2012
Segment Reporting Information [Line Items]
Net sales	$ 251,289,000	$ 257,138,000
Income from operations	29,100,000	29,000,000
Goodwill	65,081,000		65,829,000
Income from operations before provision for taxes on income [Abstract]
Income from operations for reportable segments	29,100,000	29,000,000
Unallocated corporate expenses	(2,000,000)	(2,000,000)
Income from operations	27,136,000	26,992,000
Non-operating deductions, net	168,000	(598,000)
Income from continuing operations before provision for taxes	27,304,000	26,394,000
Revenue from External Customer [Line Items]
Net sales	251,289,000	257,138,000
Paper PCC [Member]
Segment Reporting Information [Line Items]
Net sales	121,300,000	121,700,000
Revenue from External Customer [Line Items]
Net sales	121,300,000	121,700,000
Specialty PCC [Member]
Segment Reporting Information [Line Items]
Net sales	16,800,000	16,400,000
Revenue from External Customer [Line Items]
Net sales	16,800,000	16,400,000
Talc [Member]
Segment Reporting Information [Line Items]
Net sales	12,400,000	12,100,000
Revenue from External Customer [Line Items]
Net sales	12,400,000	12,100,000
Ground Calcium Carbonate [Member]
Segment Reporting Information [Line Items]
Net sales	17,200,000	17,500,000
Revenue from External Customer [Line Items]
Net sales	17,200,000	17,500,000
Refractory Products [Member]
Segment Reporting Information [Line Items]
Net sales	62,400,000	69,100,000
Revenue from External Customer [Line Items]
Net sales	62,400,000	69,100,000
Metallurgical Products [Member]
Segment Reporting Information [Line Items]
Net sales	21,200,000	20,300,000
Revenue from External Customer [Line Items]
Net sales	21,200,000	20,300,000
Specialty Minerals [Member]
Segment Reporting Information [Line Items]
Net sales	167,700,000	167,700,000
Income from operations	22,200,000	19,900,000
Goodwill	13,600,000		14,100,000
Income from operations before provision for taxes on income [Abstract]
Income from operations for reportable segments	22,200,000	19,900,000
Revenue from External Customer [Line Items]
Net sales	167,700,000	167,700,000
Refractories [Member]
Segment Reporting Information [Line Items]
Net sales	83,600,000	89,400,000
Income from operations	6,900,000	9,100,000
Goodwill	51,500,000		51,700,000
Income from operations before provision for taxes on income [Abstract]
Income from operations for reportable segments	6,900,000	9,100,000
Revenue from External Customer [Line Items]
Net sales	$ 83,600,000	$ 89,400,000