Annual report pursuant to Section 13 and 15(d)

Supplemental Information on Oil and Natural Gas Properties (Unaudited) (Narrative) (Details)

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Supplemental Information on Oil and Natural Gas Properties (Unaudited) (Narrative) (Details)
MBoe in Thousands
 12 Months Ended
Dec. 31, 2018
item
MBoe
Dec. 31, 2017
item
MBoe
Dec. 31, 2016
item
MBoe
Dec. 31, 2015
MBoe
Reserve Quantities [Line Items]        
Proved developed and undeveloped reserve, net (energy) 238,508 136,974 91,580 54,271
Proved developed and proved undeveloped reserves, percentage change between periods 74.00% 50.00% 69.00%  
Revisions to previous estimates   1,472 (1,737)  
Proved undeveloped reserves 109,903 67,656 48,348 25,654
Disposed of by Sale        
Reserve Quantities [Line Items]        
Proved developed and undeveloped reserve period increase (decrease)     11,168  
Permian Basin        
Reserve Quantities [Line Items]        
Proved developed and undeveloped reserve period increase (decrease) 124,638 57,881 48,477  
Number of wells drilled during the period | item 70 49 29  
Number of wells drilled during the period, net | item 57.5 38.2 20.9  
Revisions to previous estimates (2,021)      
Reclassifications due to changes in development plan (9,065)      
Removal of proved undeveloped locations | item 19 13 4