Property and Business Interruption Insurance Claims and Recoveries - Additional Information (Detail) (USD $)	12 Months Ended		1 Months Ended		12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Oct. 31, 2013	Jan. 31, 2014	Dec. 31, 2012
Property And Or Business Interruption Insurance Claims [Line Items]
Property insurance recoveries in excess of losses incurred	$ 5,147,000	$ 66,255,000
El Dorado Facility [Member]
Property And Or Business Interruption Insurance Claims [Line Items]
Aggregate amount of claim settlement			113,000,000
Cherokee Facility [Member]
Property And Or Business Interruption Insurance Claims [Line Items]
Aggregate amount of claim settlement				43,500,000
Approved insurance payments received				36,500,000
Income recognized from insurance recover	28,000,000
Property Insurance [Member] | El Dorado Facility [Member]
Property And Or Business Interruption Insurance Claims [Line Items]
Deductible property damage under insurance		1,000,000
Approved insurance payments		90,700,000	90,700,000
Insurance claim recoverable costs		24,700,000
Property insurance recoveries in excess of losses incurred		66,000,000
Property Insurance [Member] | Cherokee Facility [Member]
Property And Or Business Interruption Insurance Claims [Line Items]
Deductible property damage under insurance	2,500,000	2,500,000
Business Interruption Insurance [Member] | El Dorado Facility [Member]
Property And Or Business Interruption Insurance Claims [Line Items]
Waiting period for business interruption coverage		30 days
Approved insurance payments		22,300,000	22,300,000
Business Interruption Insurance [Member] | El Dorado Facility [Member] | Cost of Sales [Member]
Property And Or Business Interruption Insurance Claims [Line Items]
Approved insurance payments		15,000,000			7,300,000
Business Interruption Insurance [Member] | Cherokee Facility [Member]
Property And Or Business Interruption Insurance Claims [Line Items]
Waiting period for business interruption coverage		30 days
Approved insurance payments received prior to conclusion		15,000,000
Deferred gain on insurance recovery		1,400,000
Approved insurance payments received	28,500,000
Approved insurance payments received prior to conclusion		15,000,000
Business Interruption Insurance [Member] | Cherokee Facility [Member] | Cost of Sales [Member]
Property And Or Business Interruption Insurance Claims [Line Items]
Insurance claim recoverable costs		$ 13,600,000