Balance Sheets (Current Period Unaudited) (Parentheticals) |
Mar. 31, 2017
a
$ / shares
shares
|
Dec. 31, 2016
a
$ / shares
shares
|
|---|---|---|
| Real estate acquired, acres (Acre) | 10,065 | 10,065 |
| 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 in certificates of proprietary interest, par value (in dollars per share) | $ / shares | $ 0.0333 | $ 0.0333 |
| Sub-share certificates in certificates of proprietary interest, outstanding (in shares) | shares | 7,897,818 | 7,927,314 |
| Land Surface Rights [Member] | ||
| Land (surface rights), acres (Acre) | 877,644 | 877,488 |
| Royalty Interests in Acres 1_16 [Member] | ||
| Nonparticipating perpetual royalty interest in acres (Acre) | 373,777 | 373,777 |
| Royalty Interests in Acres 1_128 [Member] | ||
| Nonparticipating perpetual royalty interest in acres (Acre) | 85,414 | 85,414 |