Quarterly Financial Data (unaudited) (Details) (USD $) In Thousands, except Per Share data, 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
Gross profit	52,700	52,900	53,700	52,900	50,600	52,200	55,000	51,400	212,196	209,193	155,818
Income from operations	25,200	25,400	25,100	24,700	22,800	25,000	27,500	23,100	100,338	98,277	(17,053)
Income from continuing operations, net of tax	20,100	16,300	17,200	16,700	16,700	17,500	19,600	16,100	70,254	69,886	(17,753)
Income from discontinued operations, net of tax									0	0	(3,151)
Noncontrolling interests	(400)	(700)	(700)	(900)	(800)	(800)	(700)	(700)	2,733	3,017	2,892
Net income (loss) attributable to MTI	19,600	15,700	16,400	15,800	15,800	16,700	19,000	15,400	67,521	66,869	(23,796)
Basic [Abstract]
Basic earnings (loss) per share from continuing operations attributable to MTI (in dollars per share)	$ 1.11	$ 0.88	$ 0.90	$ 0.86	$ 0.86	$ 0.90	$ 1.01	$ 0.82	$ 3.75	$ 3.59	$ (1.10)
Basic earnings (loss) per share from discontinued operations attributable to MTI (in dollars per share)									$ 0.00	$ 0.00	$ (0.17)
Basic earnings (loss) per share attributable to MTI (in dollars per share)	$ 1.11	$ 0.88	$ 0.90	$ 0.86	$ 0.86	$ 0.90	$ 1.01	$ 0.82	$ 3.75	$ 3.59	$ (1.27)
Diluted [Abstract]
Diluted earnings (loss) per share from continuing operations attributable to MTI (in dollars per share)	$ 1.11	$ 0.87	$ 0.90	$ 0.86	$ 0.86	$ 0.90	$ 1.01	$ 0.82	$ 3.73	$ 3.58	$ (1.10)
Diluted earnings (loss) per share from discontinued operations attributable to MTI (in dollars per share)									$ 0.00	$ 0.00	$ (0.17)
Diluted earnings (loss) per share attributable to MTI (in dollars per share)	$ 1.11	$ 0.87	$ 0.90	$ 0.86	$ 0.86	$ 0.90	$ 1.01	$ 0.82	$ 3.73	$ 3.58	$ (1.27)
Market price range per share of common stock [Abstract]
High (in dollars per share)	$ 58.00	$ 68.63	$ 70.09	$ 68.73	$ 66.81	$ 59.68	$ 59.53	$ 56.05
Low (in dollars per share)	$ 46.75	$ 49.27	$ 63.01	$ 62.46	$ 56.43	$ 45.73	$ 46.90	$ 46.36
Close (in dollars per share)	$ 56.53	$ 49.27	$ 67.66	$ 68.73	$ 65.41	$ 58.65	$ 46.90	$ 52.30	$ 56.53	$ 65.41
Dividends paid per common share (in dollars per share)	$ 0.05	$ 0.05	$ 0.05	$ 0.05	$ 0.05	$ 0.05	$ 0.05	$ 0.05	$ 0.20
Specialty Minerals [Member]
Revenue from External Customer [Line Items]
Net sales	159,900	171,100	171,800	173,300	158,600	166,100	168,200	172,100	676,100	665,000	628,400
Specialty Minerals [Member] | PCC [Member]
Revenue from External Customer [Line Items]
Net sales	133,100	142,500	140,200	144,800	134,300	136,800	138,400	145,100
Specialty Minerals [Member] | Processed Minerals [Member]
Revenue from External Customer [Line Items]
Net sales	26,800	28,600	31,600	28,500	24,300	29,300	29,800	27,000
Refractories [Member]
Revenue from External Customer [Line Items]
Net sales	$ 91,800	$ 91,100	$ 96,600	$ 89,200	$ 84,700	$ 83,700	$ 87,600	$ 81,400	$ 368,800	$ 337,400	$ 278,900