Property, Plant and Equipment, at Cost (Detail) (USD $) In Thousands, unless otherwise specified					12 Months Ended			12 Months Ended			12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2012 Land Improvements Minimum	Dec. 31, 2012 Land Improvements Maximum	Dec. 31, 2012 Building and Improvements	Dec. 31, 2012 Building and Improvements Minimum	Dec. 31, 2012 Building and Improvements Maximum	Dec. 31, 2012 Machinery and Equipment	Dec. 31, 2012 Machinery and Equipment Minimum		Dec. 31, 2012 Machinery and Equipment Maximum		Dec. 31, 2012 Machinery and Equipment (major plant components) Minimum		Dec. 31, 2012 Machinery and Equipment (major plant components) Maximum		Dec. 31, 2012 Property, Plant and Equipment under Capital Lease Minimum	Dec. 31, 2012 Property, Plant and Equipment under Capital Lease Maximum	Dec. 31, 2012 Long Term Mineral Rights and Production Equipment Costs Minimum	Dec. 31, 2012 Long Term Mineral Rights and Production Equipment Costs Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life					5 years	30 years		10 years	45 years		3 years	[1]	19 years	[1]	20 years	[2]	45 years	[2]	19 years	50 years	7 years	60 years
Land	$ 61,123		$ 59,137
Land improvements	51,218		50,302
Buildings and improvements	198,260		194,731
Machinery and equipment	1,603,533	[1]	1,552,557	[1]
Machinery and equipment (major plant components)	586,433	[2]	533,666	[2]
Property, plant and equipment under capital lease			24,652				4,300			20,300
Long-term mineral rights and production equipment costs	83,089		62,245
Construction in progress	234,948		142,138
Total	$ 2,818,604		$ 2,619,428

[1] Consists primarily of (1) short-lived production equipment components, office and building equipment and other equipment with estimated lives ranging 3 - 7 years, and (2) production process equipment (intermediate components) with estimated lives ranging 8 - 19 years.

[2] Consists primarily of (1) production process equipment (major unit components) with estimated lives ranging 20 - 29 years, and (2) production process equipment (infrastructure and other) with estimated lives ranging 30 - 45 years.