Quarterly report pursuant to Section 13 or 15(d)

Royalty Interests (Details)

v3.19.1
Royalty Interests (Details)
$ in Thousands
 3 Months Ended 12 Months Ended
Mar. 31, 2019
USD ($)
a
$ / a
Mar. 31, 2018
USD ($)
Dec. 31, 2018
USD ($)
Net Book Value      
Royalty interests acquired $ 27,720 $ 24,303 $ 24,303
Total royalty interests 27,720 24,303  
Acquisition of royalty interests $ 3,418 0  
Royalty interest rate 12.50%    
1/16th nonparticipating perpetual royalty interests      
Real Estate Properties [Line Items]      
Nonparticipating perpetual royalty interest rate 6.25%   6.25%
Net Book Value      
1/16th nonparticipating perpetual royalty interest $ 0 0 $ 0
1/128th nonparticipating perpetual royalty interests      
Real Estate Properties [Line Items]      
Nonparticipating perpetual royalty interest rate 0.78125%   0.78125%
Net Book Value      
1/128th nonparticipating perpetual royalty interest $ 0 $ 0 $ 0
Additional real estate acquisitions      
Net Book Value      
Net royalty interests (acre) | a 301    
Acquisition of royalty interests $ 3,200    
Average price per net royalty acre acquired (in dollars per acre) | $ / a 10,500