INVENTORIES (Inventories) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
INVENTORIES [Abstract]
Finished products	$ 275,172	[1]	$ 270,603	[1]
Raw materials	19,741		29,996
Products in process	1,250		6,613
Operating supplies and other	25,641		37,394
Inventories	321,804		344,606
Encumbered Inventory	$ 4,792		$ 4,492

[1] Includes inventories encumbered by the purchaser's percentage of volumetric production payments (see Note 1, Deferred Revenue), as follows: December 31, 2014 — $4,792 thousand and December 31, 2013 — $4,492 thousand.