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Fixed Assets - Narrative (Details) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2017
Jun. 30, 2016
Jun. 30, 2017
Jun. 30, 2016
Dec. 31, 2016
Asset Retirement Obligations Details [Line Items]          
Gain on sale of assets $ 26,684 $ 0 $ 26,684 $ 0  
Asset Retirement Obligation 200,074   200,074   $ 213,726
Accrued Liabilities          
Asset Retirement Obligations Details [Line Items]          
Asset Retirement Obligation $ 20,100   $ 20,100   $ 22,400