Annual report pursuant to Section 13 and 15(d)

Subsequent Events (Details)

v3.10.0.1
Subsequent Events (Details) - Subsequent Event
$ / shares in Units, $ in Millions
 1 Months Ended
Feb. 22, 2019
USD ($)
a
Jan. 07, 2019
USD ($)
a
Feb. 28, 2019
$ / shares
Subsequent Event [Line Items]      
Sub-share declared (in dollars per share) | $ / shares     $ 1.75
Special      
Subsequent Event [Line Items]      
Sub-share declared (in dollars per share) | $ / shares     $ 4.25
Loving County      
Subsequent Event [Line Items]      
Real estate sold (in acres) | a   14,000  
Sales of real estate | $   $ 100.0  
Mineral or royalty interest in real estate sold (in acres) | a   1,280  
Reeves and Culberson Counties      
Subsequent Event [Line Items]      
Payments to acquire land | $ $ 46.9    
Real estate acquired, acres (Acre) | a 11,700    
Scenario, Forecast | Reeves and Culberson Counties      
Subsequent Event [Line Items]      
Proceeds from Sale of Real Estate Held-for-investment | $ $ 53.1