Quarterly report pursuant to Section 13 or 15(d)

Condensed Consolidated Balance Sheets (Parenthetical)

v3.10.0.1
Condensed Consolidated Balance Sheets (Parenthetical)
$ in Thousands
 6 Months Ended 12 Months Ended
Jun. 30, 2018
USD ($)
a
county
$ / shares
shares
Dec. 31, 2017
USD ($)
a
county
$ / shares
shares
Property, plant and equipment, net of accumulated depreciation of $1,270 and $463 as of June 30, 2018 and December 31, 2017, respectively | $ $ 1,270 $ 463
Number of counties with land surface rights | county 18 18
Certificates of proprietary interest, par value (in dollars per share) | $ / shares $ 100 $ 100
Certificates of proprietary interest, outstanding (in shares) | shares 0 0
Sub-share certificates of proprietary interest, par value (in dollars per share) | $ / shares $ 0.0333 $ 0.0333
Sub-share certificates of proprietary interest, outstanding (in shares) | shares 7,792,537 7,821,599
Land Surface Rights    
Land (surface rights), acres (acre) 877,514 877,633
1/16th Nonparticipating Perpetual Royalty Interest    
Nonparticipating perpetual royalty interest rate 6.25% 6.25%
Nonparticipating perpetual royalty interest in acres (acre) 373,777 373,777
1/128th Nonparticipating Perpetual Royalty Interest    
Nonparticipating perpetual royalty interest rate 0.78125% 0.78125%
Nonparticipating perpetual royalty interest in acres (acre) 85,414 85,414