Inventories Net (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Inventory Disclosure [Abstract]
Finished products	$ 427,298	$ 413,766	$ 358,759
Products in process and raw materials	60,498	65,250	20,732
Supplies and expendable parts	112,587	125,092	65,287
Inventories, Gross	600,383	604,108	444,778
Less: Allowances	(120,527)	(119,189)	(96,610)
Total	$ 479,856	$ 484,919	$ 348,168