Inventories - Inventories, Net of Reserves (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Inventory Disclosure [Abstract]
Raw materials	$ 59,985	$ 61,266
In-process and finished	117,980	117,580
Supplies	70,121	69,859
Total	$ 248,086	$ 248,705