LAND AND SUBSURFACE INTERESTS - Other Real Estate Assets (Details) - USD ($)	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Land and Subsurface Interests
Impact fees	$ 416,000		$ 925,000
Mitigation credits	849,000		1,400,000
Impact fee and mitigation credits	1,265,437		$ 2,322,906
Mitigation credits sold	1,500,000
Gain on mitigation credits sold	$ 1,200,000
Gain on mitigation credits sold (in dollars per share)	$ 0.14
Cash payments received for impact fees	$ 506,000	$ 481,000
Real Estate Operations | Cost of revenues
Land and Subsurface Interests
Mitigation credits transferred	$ 298,000