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Basis of Presentation and Significant Accounting Policies - Narrative (Details)
2 Months Ended 10 Months Ended 12 Months Ended
Feb. 28, 2017
USD ($)
Dec. 31, 2017
USD ($)
Dec. 31, 2019
USD ($)
facility
Dec. 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
Public Utilities, General Disclosures [Line Items]          
Capitalized interest     $ 2,000,000    
Capitalized exploratory well costs   $ 0 0 $ 0 $ 0
Net capitalized costs attributable to unproved properties $ 531,200,000   313,903,000 388,034,000  
Net capitalized costs attributable to unproved properties       388,000,000  
Impairment of oil and gas properties $ 0 $ 0 51,081,000 0  
Asset retirement obligation, noncurrent, increase in timing and cost estimates     57,000,000    
Asset retirement obligation, noncurrent, increase due to new wells     11,534,000 4,901,000  
Asset retirement obligation, noncurrent, increase due to accretion expense     7,570,000 6,258,000  
Asset retirement obligation, liabilities settled     (22,036,000) $ (3,555,000)  
Asset retirement obligation, current, increase in timing and cost estimates     $ 19,000,000    
Number of cogeneration facilities | facility     5    
Largest customers | Sales | Customer one          
Public Utilities, General Disclosures [Line Items]          
Concentration risk 34.00%   36.00% 35.00% 36.00%
Largest customers | Sales | Customer two          
Public Utilities, General Disclosures [Line Items]          
Concentration risk 29.00%   24.00% 28.00% 29.00%
Largest customers | Sales | Customer three          
Public Utilities, General Disclosures [Line Items]          
Concentration risk     13.00% 13.00% 13.00%
Largest customers | Trade accounts receivable | Customer one          
Public Utilities, General Disclosures [Line Items]          
Concentration risk     40.00% 26.00%  
Largest customers | Trade accounts receivable | Customer two          
Public Utilities, General Disclosures [Line Items]          
Concentration risk     17.00% 22.00%  
Largest customers | Trade accounts receivable | Customer three          
Public Utilities, General Disclosures [Line Items]          
Concentration risk     11.00% 10.00%  
Buildings and leasehold improvements | Minimum          
Public Utilities, General Disclosures [Line Items]          
Expected useful life     5 years    
Buildings and leasehold improvements | Maximum          
Public Utilities, General Disclosures [Line Items]          
Expected useful life     30 years    
Plant and pipeline, drilling and other equipment | Minimum          
Public Utilities, General Disclosures [Line Items]          
Expected useful life     2 years    
Plant and pipeline, drilling and other equipment | Maximum          
Public Utilities, General Disclosures [Line Items]          
Expected useful life     30 years    
Restricted Stock Units (RSUs) and Performance-based Restricted Stock Units (PSUs) | Minimum          
Public Utilities, General Disclosures [Line Items]          
Vesting period     1 year    
Restricted Stock Units (RSUs) and Performance-based Restricted Stock Units (PSUs) | Maximum          
Public Utilities, General Disclosures [Line Items]          
Vesting period     3 years    
Restricted Stock Units (RSUs)          
Public Utilities, General Disclosures [Line Items]          
Vesting period     3 years    
Performance-based Restricted Stock Units (PSUs) | Minimum          
Public Utilities, General Disclosures [Line Items]          
Vesting period     2 years    
Performance-based Restricted Stock Units (PSUs) | Maximum          
Public Utilities, General Disclosures [Line Items]          
Vesting period     3 years    
Proved Oil and Gas Properties          
Public Utilities, General Disclosures [Line Items]          
Impairment of oil and gas properties     $ 23,000,000    
Unproved Oil and Gas Properties          
Public Utilities, General Disclosures [Line Items]          
Impairment of oil and gas properties     $ 28,000,000