LAND AND SUBSURFACE INTERESTS - Other Real Estate Assets (Details) - USD ($)	3 Months Ended	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Land and Subsurface Interests
Impact fees	$ 632,000	$ 632,000		$ 925,000
Mitigation credits	883,000	883,000		1,400,000
Impact fee and mitigation credits	1,515,906	1,515,906		$ 2,322,906
Mitigation credits sold	1,100,000
Gain on mitigation credits sold	$ 932,000
Gain on mitigation credits sold (in dollars per share)	$ 0.10
Cash payments received for impact fees		$ 291,000	$ 272,000
Real Estate Operations | Cost of revenues
Land and Subsurface Interests
Mitigation credits transferred	$ 298,000