Property, Plant and Equipment (Details) - USD ($) $ in Thousands		Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Land		$ 120,842	$ 120,702
Land improvements		59,387	57,833
Buildings and improvements		256,603	236,577
Machinery and equipment	[1]	2,501,481	2,216,085
Long-term mineral rights and production equipment costs		654,006	652,871
Construction in progress		318,203	416,404
Total		$ 3,910,522	$ 3,700,472	[2]

[1] Consists primarily of (1) short-lived production equipment components, office and building equipment and other equipment with estimated lives ranging 2 – 7 years, (2) production process equipment (intermediate components) with estimated lives ranging 8 – 19 years, (3) production process equipment (major unit components) with estimated lives ranging 20 – 29 years, and (4) production process equipment (infrastructure and other) with estimated lives ranging 30 – 45 years.

[2] As of December 31, 2015, $424.1 million of Property, plant and equipment, at cost, was classified as Assets held for sale in the consolidated balance sheets. See Note 3, “Divestitures,” for additional information.