Segment and Related Information (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Oct. 02, 2011	Sep. 30, 2012	Oct. 02, 2011	Dec. 31, 2011
Segment Reporting Information [Line Items]
Net sales	$ 250,346,000	$ 262,192,000	$ 761,453,000	$ 793,111,000
Income from operations	29,800,000	26,800,000	89,600,000	79,400,000
Restructuring costs (reversals)	0	240,000	0	470,000
Goodwill	65,738,000		65,738,000		64,671,000
Income from operations before provision for taxes on income [Abstract]
Income from operations for reportable segments	29,800,000	26,800,000	89,600,000	79,400,000
Unallocated corporate expenses	(2,000,000)	(1,400,000)	(5,300,000)	(4,200,000)
Income from operations	27,848,000	25,394,000	84,316,000	75,175,000
Non-operating deductions, net	(650,000)	(1,663,000)	(2,016,000)	(3,299,000)
Income from continuing operations before provision for taxes	27,198,000	23,731,000	82,300,000	71,876,000
Revenue from External Customer [Line Items]
Net sales	250,346,000	262,192,000	761,453,000	793,111,000
Paper PCC [Member]
Segment Reporting Information [Line Items]
Net sales	120,600,000	126,500,000	361,600,000	379,300,000
Revenue from External Customer [Line Items]
Net sales	120,600,000	126,500,000	361,600,000	379,300,000
Specialty PCC [Member]
Segment Reporting Information [Line Items]
Net sales	16,400,000	16,000,000	49,800,000	48,200,000
Revenue from External Customer [Line Items]
Net sales	16,400,000	16,000,000	49,800,000	48,200,000
Talc [Member]
Segment Reporting Information [Line Items]
Net sales	11,900,000	11,300,000	37,100,000	35,400,000
Revenue from External Customer [Line Items]
Net sales	11,900,000	11,300,000	37,100,000	35,400,000
Ground Calcium Carbonate [Member]
Segment Reporting Information [Line Items]
Net sales	16,700,000	17,300,000	52,900,000	53,200,000
Revenue from External Customer [Line Items]
Net sales	16,700,000	17,300,000	52,900,000	53,200,000
Refractory Products [Member]
Segment Reporting Information [Line Items]
Net sales	66,000,000	71,100,000	200,500,000	216,100,000
Revenue from External Customer [Line Items]
Net sales	66,000,000	71,100,000	200,500,000	216,100,000
Metallurgical Products [Member]
Segment Reporting Information [Line Items]
Net sales	18,700,000	20,000,000	59,500,000	60,900,000
Revenue from External Customer [Line Items]
Net sales	18,700,000	20,000,000	59,500,000	60,900,000
Specialty Minerals [Member]
Segment Reporting Information [Line Items]
Net sales	165,600,000	171,100,000	501,400,000	516,100,000
Income from operations	22,600,000	19,300,000	64,600,000	57,200,000
Restructuring costs (reversals)				400,000
Goodwill	14,100,000		14,100,000		13,800,000
Income from operations before provision for taxes on income [Abstract]
Income from operations for reportable segments	22,600,000	19,300,000	64,600,000	57,200,000
Revenue from External Customer [Line Items]
Net sales	165,600,000	171,100,000	501,400,000	516,100,000
Refractories [Member]
Segment Reporting Information [Line Items]
Net sales	84,700,000	91,100,000	260,000,000	277,000,000
Income from operations	7,200,000	7,500,000	25,000,000	22,200,000
Restructuring costs (reversals)		200,000		0
Goodwill	51,600,000		51,600,000		50,900,000
Income from operations before provision for taxes on income [Abstract]
Income from operations for reportable segments	7,200,000	7,500,000	25,000,000	22,200,000
Revenue from External Customer [Line Items]
Net sales	$ 84,700,000	$ 91,100,000	$ 260,000,000	$ 277,000,000