Annual report pursuant to Section 13 and 15(d)

Estimated Fair Value of Derivative Contracts (Detail)

v2.4.0.8
Estimated Fair Value of Derivative Contracts (Detail) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2013
Dec. 31, 2012
Derivatives Fair Value [Line Items]    
Fair value of commodity derivative contracts $ 141  
Fair value of commodity derivative contracts 9,423  
Prepaid And Other Assets
   
Derivatives Fair Value [Line Items]    
Fair value of commodity derivative contracts 141  
Accrued Liabilities
   
Derivatives Fair Value [Line Items]    
Fair value of commodity derivative contracts 9,423 6,355
Other Liabilities (noncurrent)
   
Derivatives Fair Value [Line Items]    
Fair value of commodity derivative contracts   $ 3,046