Property Plant Equipment and Mineral Rights and Reserves (Tables)

12 Months Ended

Dec. 31, 2011

Property Plant Equipment and Mineral Rights and Reserves [Abstract]

Property plant equipment and mineral rights and reserves

	December 31,
	2011		2010
Mineral rights and reserves	$	41,861	$	51,435
Land		13,881		11,591
Buildings and improvements		95,388		86,410
Machinery and equipment		362,043		352,768
Construction in progress		24,907		15,173
		538,080		517,377

Range of useful lives to depreciate plant and equipment

Buildings and improvements	3-50 years
Machinery and equipment	1-25 years

Depreciation and depletion were charged to income

	2011		2010		2009
Depreciation expense	$	34,969	$	30,039	$	28,872
Depletion expense		2,084		1,211		365
		37,053		31,250		29,237