Property Plant Equipment and Mineral Rights and Reserves (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010
Property plant equipment and mineral rights and reserves
Mineral rights and reserves	$ 52,482	[1]	$ 65,018	[1]
Land	12,103	[1]	10,875	[1]
Buildings and improvements	97,503	[1]	86,410	[1]
Machinery and equipment	362,043	[1]	350,952	[1]
Construction in progress	25,207	[1]	15,285	[1]
Gross property, plant and equipment	$ 549,338	[1]	$ 528,540	[1]

[1] Restated