Segment and Related Information (Goodwill by Reportable Segment) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Goodwill [Line Items]
Goodwill	$ 64,671	$ 67,156
Specialty Minerals [Member]
Goodwill [Line Items]
Goodwill	13,800	13,800
Refractories [Member]
Goodwill [Line Items]
Goodwill	$ 50,900	$ 53,300

Carrying amount as of the balance sheet date, which is the cumulative amount paid and (if applicable) the fair value of any noncontrolling interest in the acquiree, adjusted for any amortization recognized prior to the adoption of any changes in generally accepted accounting principles (as applicable) and for any impairment charges, in excess of the fair value of net assets acquired in one or more business combination transactions.

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Reference 5: http://www.xbrl.org/2003/role/presentationRef

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details