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Investment in Oil and Gas Properties - Additional Information (Details)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2016
USD ($)
$ / Mcf
$ / bbl
Jun. 30, 2016
USD ($)
$ / Mcf
$ / bbl
Mar. 31, 2016
USD ($)
$ / Mcf
$ / bbl
Sep. 30, 2016
USD ($)
$ / Mcf
$ / bbl
Sep. 30, 2015
USD ($)
Sep. 30, 2016
USD ($)
$ / Mcf
$ / bbl
Sep. 30, 2015
USD ($)
Oil and Gas In Process Activities [Line Items]              
Write-down of oil and gas properties       $ 36,484 $ 295,679 $ 284,337 $ 1,011,385
Decrease in written down value of oil and gas properties   $ 18,100 $ 23,000 $ 9,600      
CANADA              
Oil and Gas In Process Activities [Line Items]              
Write-down of oil and gas properties     $ 300        
Oil              
Oil and Gas In Process Activities [Line Items]              
Average 12-month oil prices net of differentials | $ / bbl 40.51 43.49 46.72 40.51   40.51  
Natural Gas              
Oil and Gas In Process Activities [Line Items]              
Average twelve month gas prices net of differentials | $ / Mcf 1.99 1.93 2.01 1.99   1.99  
Natural Gas Liquids (MBbls)              
Oil and Gas In Process Activities [Line Items]              
Average 12-month gas prices net of differentials | $ / bbl 13.88 9.33 13.65 13.88   13.88  
Oil And Gas              
Oil and Gas In Process Activities [Line Items]              
Write-down of oil and gas properties $ 36,500 $ 118,600 $ 128,900