Inventories Net (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Inventory Disclosure [Abstract]
Finished products	$ 420,027	$ 413,766	$ 397,684
Products in process and raw materials	59,005	65,250	58,678
Supplies and expendable parts	108,759	125,092	127,319
Inventories, Gross	587,791	604,108	583,681
Less: Allowances	(123,266)	(119,189)	(108,388)
Total	$ 464,525	$ 484,919	$ 475,293