Property and Business Interruption Insurance Claims and Recovery - Additional Information (Detail) (USD $)	12 Months Ended		12 Months Ended
	Dec. 31, 2010	Dec. 31, 2012	Dec. 31, 2012 Pryor Facility [Member]	Dec. 31, 2011 Pryor Facility [Member]	Dec. 31, 2012 El Dorado Facility [Member]	Dec. 31, 2012 El Dorado Facility [Member] Property Insurance [Member]	Dec. 31, 2012 El Dorado Facility [Member] Business Interruption Insurance [Member]	Dec. 31, 2012 Cherokee Facility [Member]
Property And Or Business Interruption Insurance Claims [Line Items]
Waiting period for business interruption coverage			30 days				30 days	30 days
Gain on business interruption insurance recovery				$ 8,600,000
Deductible property damage under insurance			1,000,000			1,000,000		2,500,000
Approved insurance payments received					20,000,000
Approved insurance payments					40,000,000	28,600,000	11,400,000
Approved insurance payments with reservation of rights					20,000,000
Insurance claim recoverable costs						21,700,000	7,300,000
Property insurance recoveries in excess of losses incurred	7,518,000					6,900,000
Insurance recoveries in excess of recoverable costs, not recognized							4,100,000
Insurance claim receivable		$ 10,059,000			$ 9,000,000			$ 1,100,000