Property Plant Equipment and Mineral Rights and Reserves (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Depreciation and depletion charged to income
Depreciation expense	$ 35,036	[1]	$ 30,106	[1]	$ 28,932	[1]
Depletion expense	2,574	[1]	1,180	[1]	883	[1]
Depreciation and depletion	$ 37,610	[1]	$ 31,286	[1]	$ 29,815	[1]

[1] Restated