REAL ESTATE OPERATIONS - Subsurface Interests (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021 USD ($) a county	Mar. 31, 2020 USD ($)
Subsurface interests
Area of land (in acres) | a	25,000
Revenue from contract with customer, including assessed tax	$ 1,893	$ 81
Subsurface Interests
Subsurface interests
Revenue from contract with customer, including assessed tax	$ 1,900	0
Surface land over subsurface interests
Subsurface interests
Area of land (in acres) | a	429,000
Number of counties in which Subsurface Interests are owned | county	20
Revenue recognized for cash payments for the release of surface entry rights	$ 10	70
Real Estate Operations | Subsurface Interests
Subsurface interests
Revenue recognized for cash payments for the release of surface entry rights	$ 10	$ 10