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Acquisitions and Dispositions - Additional Information (Detail)
 1 Months Ended 3 Months Ended 12 Months Ended
May 31, 2017
USD ($)
a
Mar. 31, 2018
USD ($)
a
Well
Dec. 31, 2017
USD ($)
a
Dec. 31, 2016
USD ($)
Business Acquisition [Line Items]        
Purchase of non-controlling interests     $ 308,000 $ 224,000
Capital expenditures, including exploration expense     59,361,000 20,843,000
Proceeds from sale of property and equipment     46,231,000 35,226,000
West Texas and Oklahoma [Member] | Mineral Acreage [Member]        
Business Acquisition [Line Items]        
Proceeds from sale of property and equipment     46,000,000 34,400,000
Martin County [Member] | Mineral Acreage [Member]        
Business Acquisition [Line Items]        
Proceeds from sale of property and equipment     $ 37,400,000  
Number of net acres sold or farmed-out leasehold rights | a     2,096  
OKLAHOMA | Mineral Acreage [Member]        
Business Acquisition [Line Items]        
Proceeds from sale of property and equipment     $ 8,600,000  
Number of net acres sold or farmed-out leasehold rights | a     1,554  
Upton County, Texas [Member] | Mineral Acreage [Member]        
Business Acquisition [Line Items]        
Number of net acres acquired | a 118      
Capital expenditures, including exploration expense $ 596,600      
Partnership And Trust [Member]        
Business Acquisition [Line Items]        
Purchase of non-controlling interests     $ 308,000 $ 224,000
Subsequent Event [Member]        
Business Acquisition [Line Items]        
Proceeds from sale of additional non-core acreage and properties   $ 1,800,000    
Subsequent Event [Member] | Reagan County, Texas [Member] | Mineral Acreage [Member]        
Business Acquisition [Line Items]        
Number of net acres acquired | a   464    
Number of gross mineral acres acquired | a   1,640    
Capital expenditures, including exploration expense   $ 6,080,000    
Number of oil wells with working interest ownership | Well   53    
Number of commercial salt water disposal well operated | Well   1    
Subsequent Event [Member] | Reagan County, Texas [Member] | Mineral Acreage [Member] | Minimum [Member]        
Business Acquisition [Line Items]        
Percentage of working interest ownership   16.60%    
Subsequent Event [Member] | Reagan County, Texas [Member] | Mineral Acreage [Member] | Maximum [Member]        
Business Acquisition [Line Items]        
Percentage of working interest ownership   33.40%