Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Narrative (Details)

v2.4.0.8
Summary of Significant Accounting Policies - Narrative (Details) (USD $)
12 Months Ended
Dec. 31, 2013
purchaser
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Summary Of Significant Accounting Policies [Line Items]        
Number of purchasers 1      
Accounts receivable, collection period 30 days      
Conversion ratio, gas to barrels of oil 6      
Capitalized costs of oil and natural gas properties excluded from amortization $ 950,590,000 $ 626,295,000    
Cumulative translation adjustment (9,781,000) 2,442,000 1,087,000 2,952,000
Gas balancing payable $ 0 $ 400,000    
Minimum [Member]
       
Summary Of Significant Accounting Policies [Line Items]        
Useful life 3 years      
Maximum [Member]
       
Summary Of Significant Accounting Policies [Line Items]        
Useful life 30 years