Inventories - Summary of Inventories, at LIFO Value (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Inventory Net [Abstract]
Finished goods	$ 25,122	$ 23,172
Raw materials	13,560	18,068
Total FIFO inventories	38,682	41,240
Reserve to adjust inventories to LIFO value	(23,719)	(23,719)
Total LIFO inventories	$ 14,963	$ 17,521