Fair Value Measurements - Schedule of Positions Measured at Fair Value (Details) - USD ($)
Jun. 30, 2018
Dec. 31, 2017
Financial assets    
Commodity derivative asset - current $ 22,727,000 $ 433,000
Commodity derivative asset - noncurrent 0 662,000
Financial liabilities    
Commodity derivative liability - current 0 240,000
Commodity derivative liability - noncurrent 2,857,000 0
Fair Value, Measurements, Recurring    
Financial assets    
Netting Adjustments (2,886,000) (287,000)
Total financial assets 22,727,000 1,095,000
Financial liabilities    
Netting Adjustments (2,886,000)  
Total financial liabilities 2,857,000  
Fair Value, Measurements, Recurring | Level 1    
Financial assets    
Derivative asset, gross 0 0
Financial liabilities    
Derivative liability, gross 0  
Fair Value, Measurements, Recurring | Level 2    
Financial assets    
Derivative asset, gross 25,613,000 1,382,000
Financial liabilities    
Derivative liability, gross 5,743,000  
Fair Value, Measurements, Recurring | Level 3    
Financial assets    
Derivative asset, gross 0 0
Financial liabilities    
Derivative liability, gross 0  
Current assets | Fair Value, Measurements, Recurring    
Financial assets    
Netting Adjustments (1,264,000) (287,000)
Commodity derivative asset - current 22,727,000 433,000
Current assets | Fair Value, Measurements, Recurring | Level 1    
Financial assets    
Derivative asset, gross 0 0
Current assets | Fair Value, Measurements, Recurring | Level 2    
Financial assets    
Derivative asset, gross 23,991,000 720,000
Current assets | Fair Value, Measurements, Recurring | Level 3    
Financial assets    
Derivative asset, gross 0 0
Noncurrent assets | Fair Value, Measurements, Recurring    
Financial assets    
Netting Adjustments (1,622,000) 0
Commodity derivative asset - noncurrent 0 662,000
Noncurrent assets | Fair Value, Measurements, Recurring | Level 1    
Financial assets    
Derivative asset, gross 0 0
Noncurrent assets | Fair Value, Measurements, Recurring | Level 2    
Financial assets    
Derivative asset, gross 1,622,000 662,000
Noncurrent assets | Fair Value, Measurements, Recurring | Level 3    
Financial assets    
Derivative asset, gross 0 0
Current liabilities | Fair Value, Measurements, Recurring    
Financial liabilities    
Netting Adjustments (1,264,000) (287,000)
Commodity derivative liability - current 0 240,000
Current liabilities | Fair Value, Measurements, Recurring | Level 1    
Financial liabilities    
Derivative liability, gross 0 0
Current liabilities | Fair Value, Measurements, Recurring | Level 2    
Financial liabilities    
Derivative liability, gross 1,264,000 527,000
Current liabilities | Fair Value, Measurements, Recurring | Level 3    
Financial liabilities    
Derivative liability, gross 0 $ 0
Noncurrent liabilities | Fair Value, Measurements, Recurring    
Financial liabilities    
Netting Adjustments (1,622,000)  
Commodity derivative liability - noncurrent 2,857,000  
Noncurrent liabilities | Fair Value, Measurements, Recurring | Level 1    
Financial liabilities    
Derivative liability, gross 0  
Noncurrent liabilities | Fair Value, Measurements, Recurring | Level 2    
Financial liabilities    
Derivative liability, gross 4,479,000  
Noncurrent liabilities | Fair Value, Measurements, Recurring | Level 3    
Financial liabilities    
Derivative liability, gross $ 0