Annual report pursuant to Section 13 and 15(d)

Real Estate Activity (Details)

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Real Estate Activity (Details)
 3 Months Ended 12 Months Ended
Dec. 31, 2019
USD ($)
a
Dec. 31, 2019
USD ($)
a
$ / a
numberOfCounties
Dec. 31, 2018
USD ($)
a
$ / a
Dec. 31, 2017
USD ($)
a
$ / a
Number of Acres        
Land (surface rights) (acre) 849,856 849,856 877,462  
Real estate acquired (acre) 51,931 51,931 24,715  
Total real estate situated in 19 counties in Texas (acres) 901,787 901,787 902,177  
Net Book Value        
Land (surface rights) | $ $ 0 $ 0 $ 0  
Real estate acquired | $ 107,075,000 107,075,000 10,492,000  
Total real estate situated in 19 counties in Texas | $ $ 107,075,000 $ 107,075,000 $ 10,492,000  
Number of countries with real estate and land surface rights | numberOfCounties   19    
Area of real estate property, sold (in acres)   21,986 171 11
Acres of land exchanged from trust (in acres) 5,620      
Acres of land received from exchange (in acres) 5,545      
Proceeds from sale of real estate | $ $ 22,000,000.0 $ 113,000,000.0 $ 4,400,000 $ 200,000
Average sales price (in USD per acre) | $ / a   5,141 25,464 20,000
Additions (acres)   21,671 14,650  
Additions | $   $ 74,400,000 $ 9,400,000  
Average purchase price (in USD per acre) | $ / a   3,434 640  
Payments to acquire land | $       $ 0