v2.4.0.6
Derivatives - Commodity Derivatives Volumes and Prices (Detail)
Dec. 31, 2012
MMBTU
Natural Gas - 2013 Contract One [Member] | Swap [Member]
 
Derivative [Line Items]  
Volume Transacted 200,000
Contract Price 3.54
Natural Gas - 2013 Contract Two [Member] | Swap [Member]
 
Derivative [Line Items]  
Volume Transacted 190,000
Contract Price 3.80
Crude Oil - 2013 Contract One [Member] | Collar [Member]
 
Derivative [Line Items]  
Volume Transacted 650
Crude Oil - 2013 Contract One [Member] | Minimum [Member] | Collar [Member]
 
Derivative [Line Items]  
Contract Price 90.00
Crude Oil - 2013 Contract One [Member] | Maximum [Member] | Collar [Member]
 
Derivative [Line Items]  
Contract Price 105.80
Crude Oil - 2013 Contract Two [Member] | Collar [Member]
 
Derivative [Line Items]  
Volume Transacted 450
Crude Oil - 2013 Contract Two [Member] | Minimum [Member] | Collar [Member]
 
Derivative [Line Items]  
Contract Price 90.00
Crude Oil - 2013 Contract Two [Member] | Maximum [Member] | Collar [Member]
 
Derivative [Line Items]  
Contract Price 101.45
Crude Oil - 2014 [Member] | Collar [Member]
 
Derivative [Line Items]  
Volume Transacted 550
Crude Oil - 2014 [Member] | Minimum [Member] | Collar [Member]
 
Derivative [Line Items]  
Contract Price 90.00
Crude Oil - 2014 [Member] | Maximum [Member] | Collar [Member]
 
Derivative [Line Items]  
Contract Price 105.50