Property, Plant and Equipment (Tables)

12 Months Ended

Dec. 31, 2011

Property, Plant and Equipment [Abstract]

Major categories of property, plant and equipment and accumulated depreciation and depletion

     The major categories of property, plant and equipment and accumulated depreciation and depletion are presented below:

Thousands of Dollars		2011			2010
Land	$	27,370		$	27,334
Quarries/mining properties		39,596			39,596
Buildings		147,115			144,348
Machinery and equipment		911,753			918,450
Construction in progress		31,060			13,438
Furniture and fixtures and other		91,755			95,256
		1,248,649			1,238,422
Less: Accumulated depreciation and depletion		(930,515	)		(905,625	)
Property, plant and equipment, net	$	318,134		$	332,797