Inventories (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
Inventories
Finished products	$ 262,886	[1]	$ 260,732	[1]
Raw materials	27,758		23,819
Products in process	5,963		4,198
Operating supplies and other	38,415		38,908
Total	$ 335,022		$ 327,657

[1] Includes inventories encumbered by the purchaser's percentage of a volumetric production payment (see Note 19), as follows: December 31, 2012 - $8,726 thousand.