Annual report pursuant to Section 13 and 15(d)

Open Commodity Derivatives (Detail)

v2.4.0.8
Open Commodity Derivatives (Detail) (Swaps - Oil)
 12 Months Ended
Dec. 31, 2013
Ice Brent Crude Oil Futures
  
Derivatives Fair Value [Line Items]  
Notional Quantity (Bbls) 674,900
Weighted Average Contract Price 97.38
Nymex Crude Oil Futures
  
Derivatives Fair Value [Line Items]  
Notional Quantity (Bbls) 1,372,000
Weighted Average Contract Price 97.27
Argus Crude Oil Futures
  
Derivatives Fair Value [Line Items]  
Notional Quantity (Bbls) 1,464,000
Weighted Average Contract Price 97.83
2014: 1st Quarter
  
Derivatives Fair Value [Line Items]  
Termination Period 1st quarter
2014: 1st Quarter | Ice Brent Crude Oil Futures
  
Derivatives Fair Value [Line Items]  
Notional Quantity (Bbls) 180,000
Weighted Average Contract Price 97.38
2014: 1st Quarter | Nymex Crude Oil Futures
  
Derivatives Fair Value [Line Items]  
Notional Quantity (Bbls) 762,000
Weighted Average Contract Price 97.39
2014: 1st Quarter | Argus Crude Oil Futures
  
Derivatives Fair Value [Line Items]  
Notional Quantity (Bbls) 180,000
Weighted Average Contract Price 98.20
2014: 2nd Quarter
  
Derivatives Fair Value [Line Items]  
Termination Period 2nd quarter
2014: 2nd Quarter | Ice Brent Crude Oil Futures
  
Derivatives Fair Value [Line Items]  
Notional Quantity (Bbls) 172,900
Weighted Average Contract Price 97.38
2014: 2nd Quarter | Nymex Crude Oil Futures
  
Derivatives Fair Value [Line Items]  
Notional Quantity (Bbls) 455,000
Weighted Average Contract Price 97.17
2014: 2nd Quarter | Argus Crude Oil Futures
  
Derivatives Fair Value [Line Items]  
Notional Quantity (Bbls) 364,000
Weighted Average Contract Price 97.88
2014: 3rd Quarter
  
Derivatives Fair Value [Line Items]  
Termination Period 3rd quarter
2014: 3rd Quarter | Ice Brent Crude Oil Futures
  
Derivatives Fair Value [Line Items]  
Notional Quantity (Bbls) 165,600
Weighted Average Contract Price 97.38
2014: 3rd Quarter | Nymex Crude Oil Futures
  
Derivatives Fair Value [Line Items]  
Notional Quantity (Bbls) 155,000
Weighted Average Contract Price 97.00
2014: 3rd Quarter | Argus Crude Oil Futures
  
Derivatives Fair Value [Line Items]  
Notional Quantity (Bbls) 552,000
Weighted Average Contract Price 97.65
2014: 4th Quarter
  
Derivatives Fair Value [Line Items]  
Termination Period 4th quarter
2014: 4th Quarter | Ice Brent Crude Oil Futures
  
Derivatives Fair Value [Line Items]  
Notional Quantity (Bbls) 156,400
Weighted Average Contract Price 97.37
2014: 4th Quarter | Nymex Crude Oil Futures
  
Derivatives Fair Value [Line Items]  
Notional Quantity (Bbls)   
Weighted Average Contract Price   
2014: 4th Quarter | Argus Crude Oil Futures
  
Derivatives Fair Value [Line Items]  
Notional Quantity (Bbls) 368,000
Weighted Average Contract Price 97.88