Annual report pursuant to Section 13 and 15(d)

Acquisitions and Dispositions (Narrative) (Details)

v3.3.1.900
Acquisitions and Dispositions (Narrative) (Details)
$ in Thousands
 1 Months Ended 3 Months Ended
Nov. 09, 2015
USD ($)
a
Oct. 08, 2014
USD ($)
Jan. 31, 2016
USD ($)
Mar. 31, 2014
USD ($)
a
Dec. 31, 2013
USD ($)
Jun. 30, 2013
USD ($)
a
item
bbl
Central Midland Basin Texas [Member]            
Business Acquisition [Line Items]            
Gas and oil area, developed and undeveloped, net | a 628          
Aggregate cash purchase price $ 29,800 $ 210,205        
Working interest   62.00%        
Net revenue interest   46.50%        
Net proceeds from an equity offering   $ 122,514        
Southern Midland Basin Texas [Member]            
Business Acquisition [Line Items]            
Gas and oil area, developed and undeveloped, net | a       1,527   2,186
Gas and oil area, developed and undeveloped, gross | a           2,468
Aggregate cash purchase price       $ 8,200   $ 11,000
Working interest       100.00%    
Net revenue interest       78.00%    
Productive oil wells, number of wells, gross | item           7
Proved developed reserves | bbl           1,301
Medusa Fields, Medusa Spar LLC, And Gulf Of Mexico Shelf Properties [Member]            
Business Acquisition [Line Items]            
Divestiture of business, sales price         $ 88,000  
Swan Lake Field [Member]            
Business Acquisition [Line Items]            
Divestiture of business, percentage of business sold         69.00%  
Divestiture of business, sales price         $ 2,000  
Medusa Spar, LLC [Member]            
Business Acquisition [Line Items]            
Divestiture of business, percentage of business sold         10.00%  
Medusa Field [Member]            
Business Acquisition [Line Items]            
Divestiture of business, percentage of business sold         15.00%  
Carpe Diem Field [Member] | Central Midland Basin Texas [Member]            
Business Acquisition [Line Items]            
Working interest 100.00%          
Net revenue interest 79.00%          
CaBo Fields [Member] | Subsequent Event [Member]            
Business Acquisition [Line Items]            
Working interest     71.30%      
Net revenue interest     53.50%      
CaBo Fields [Member] | Central Midland Basin Texas [Member]            
Business Acquisition [Line Items]            
Working interest 67.00%          
Net revenue interest 50.00%          
CaBo Fields [Member] | Central Midland Basin Texas [Member] | Subsequent Event [Member]            
Business Acquisition [Line Items]            
Consideration transferred     $ 9,300      
Working interest     4.90%      
Net revenue interest     3.70%