Annual report pursuant to Section 13 and 15(d)

Supplemental Information on Oil and Natural Gas Properties (unaudited) (Proved Undeveloped Reserves) (Narrative) (Details)

v3.3.1.900
Supplemental Information on Oil and Natural Gas Properties (unaudited) (Proved Undeveloped Reserves) (Narrative) (Details)
$ in Thousands
 2 Months Ended 3 Months Ended 12 Months Ended
Feb. 26, 2016
item
Dec. 31, 2015
USD ($)
MBoe
Sep. 30, 2015
USD ($)
Dec. 31, 2015
USD ($)
item
MBoe
Dec. 31, 2014
USD ($)
item
MBoe
Dec. 31, 2013
MBoe
Dec. 31, 2012
MBoe
Reserve Quantities [Line Items]              
Write-down of oil and natural gas properties | $   $ 121,134 $ 87,301 $ 208,435      
Proved Developed and Undeveloped Reserve, Net (Energy)   54,271   54,271 32,824 14,857 14,072
Proved Developed and Proved Undeveloped Reserves, Percentage Change Between Periods       65.00% 121.00% 6.00%  
Proved undeveloped reserves, percentage change between periods       75.00% 98.00% 1.00%  
Proved undeveloped reserves   25,654   25,654 14,623 7,387 7,337
Proved undeveloped reserves extensions discoveries and additions       13,774 10,125 5,168  
Proved undeveloped reserves reclassification to proved developed production       (2,742)      
Proved undeveloped reserves conversion to proved developed reserves, percentage transferred       19.00% 24.00% 51.00%  
Proved undeveloped reserves conversion to proved developed reserves total cost | $       $ 55,933 $ 34,619    
Reclassification of proved undeveloped production reserves to horizontal probable         1,757 3,724  
Proved undeveloped reserves sales of minerals in place         1,132 1,297  
Proved Undeveloped Reserves Sales Of Minerals In Place, Percentage           18.00%  
Permian Basin [Member]              
Reserve Quantities [Line Items]              
Number of wells drilled during the period | item       36 34    
Number of wells drilled during the period, net | item       27.1 28.7    
Subsequent Event [Member]              
Reserve Quantities [Line Items]              
Number of horizontal wells drilled | item 5            
Number of completed horizontal wells | item 2            
Number of horizontal wells in progress | item 5