Segment and Related Information (Details) (USD $)	3 Months Ended		6 Months Ended
	Jul. 01, 2012	Jul. 03, 2011	Jul. 01, 2012	Jul. 03, 2011	Dec. 31, 2011
Segment Reporting Information [Line Items]
Net sales	$ 253,969,000	$ 268,399,000	$ 511,107,000	$ 530,919,000
Income from operations	30,800,000	26,400,000	59,800,000	52,600,000
Restructuring costs (reversals)	0	0	0	230,000
Goodwill	65,316,000		65,316,000		64,671,000
Income from operations before provision for taxes on income [Abstract]
Income from operations for reportable segments	30,800,000	26,400,000	59,800,000	52,600,000
Unallocated corporate expenses	1,300,000	1,300,000	3,300,000	2,800,000
Income from operations	29,476,000	25,067,000	56,468,000	49,781,000
Non-operating deductions, net	(768,000)	(799,000)	(1,366,000)	(1,636,000)
Income from continuing operations before provision for taxes	28,708,000	24,268,000	55,102,000	48,145,000
Revenue from External Customer [Line Items]
Net sales	253,969,000	268,399,000	511,107,000	530,919,000
Paper PCC [Member]
Segment Reporting Information [Line Items]
Net sales	119,300,000	123,600,000	241,000,000	252,800,000
Revenue from External Customer [Line Items]
Net sales	119,300,000	123,600,000	241,000,000	252,800,000
Specialty PCC [Member]
Segment Reporting Information [Line Items]
Net sales	17,000,000	16,600,000	33,400,000	32,200,000
Revenue from External Customer [Line Items]
Net sales	17,000,000	16,600,000	33,400,000	32,200,000
Talc [Member]
Segment Reporting Information [Line Items]
Net sales	13,100,000	12,700,000	25,200,000	24,100,000
Revenue from External Customer [Line Items]
Net sales	13,100,000	12,700,000	25,200,000	24,100,000
Ground Calcium Carbonate [Member]
Segment Reporting Information [Line Items]
Net sales	18,700,000	18,900,000	36,200,000	36,000,000
Revenue from External Customer [Line Items]
Net sales	18,700,000	18,900,000	36,200,000	36,000,000
Refractory Products [Member]
Segment Reporting Information [Line Items]
Net sales	65,400,000	75,300,000	134,500,000	144,900,000
Revenue from External Customer [Line Items]
Net sales	65,400,000	75,300,000	134,500,000	144,900,000
Metallurgical Products [Member]
Segment Reporting Information [Line Items]
Net sales	20,500,000	21,300,000	40,800,000	40,900,000
Revenue from External Customer [Line Items]
Net sales	20,500,000	21,300,000	40,800,000	40,900,000
Specialty Minerals [Member]
Segment Reporting Information [Line Items]
Net sales	168,100,000	171,800,000	335,800,000	345,100,000
Income from operations	22,100,000	18,600,000	42,000,000	37,900,000
Restructuring costs (reversals)				400,000
Goodwill	13,900,000		13,900,000		13,800,000
Income from operations before provision for taxes on income [Abstract]
Income from operations for reportable segments	22,100,000	18,600,000	42,000,000	37,900,000
Revenue from External Customer [Line Items]
Net sales	168,100,000	171,800,000	335,800,000	345,100,000
Refractories [Member]
Segment Reporting Information [Line Items]
Net sales	85,900,000	96,600,000	175,300,000	185,800,000
Income from operations	8,700,000	7,800,000	17,800,000	14,700,000
Restructuring costs (reversals)				(200,000)
Goodwill	51,400,000		51,400,000		50,900,000
Income from operations before provision for taxes on income [Abstract]
Income from operations for reportable segments	8,700,000	7,800,000	17,800,000	14,700,000
Revenue from External Customer [Line Items]
Net sales	$ 85,900,000	$ 96,600,000	$ 175,300,000	$ 185,800,000