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 were charged to income
Depreciation expense	$ 34,969	$ 30,039	$ 28,872
Depletion expense	2,084	1,211	365
Depreciation and depletion	$ 37,053	$ 31,250	$ 29,237