Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements (Details)

v3.5.0.2
Fair Value Measurements (Details) - USD ($)
$ in Thousands
6 Months Ended
Jun. 30, 2016
Jun. 30, 2015
Mar. 31, 2016
Liabilities:      
Asset retirement obligation capitalized $ 3,195 $ 4,077  
Level 1      
Assets:      
Derivative Instruments 0    
Liabilities:      
Derivative Instruments 0    
Level 2      
Assets:      
Derivative Instruments 59,316    
Liabilities:      
Derivative Instruments 79,175    
Level 3      
Assets:      
Derivative Instruments 0    
Liabilities:      
Derivative Instruments 0    
Asset retirement obligation capitalized $ 3,200    
Level 3 | Investment in Grizzly Oil Sands ULC      
Liabilities:      
Equity investment     $ 39,100