COMMITMENTS AND CONTINGENCIES (Details)		12 Months Ended
	Jan. 01, 2016 shares	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($) officer	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Commitments and contingencies
Outstanding loan commitments and approvals to fund loans			$ 13,902,000
Future obligations under leases to fund tenant improvements and in other future construction obligation			50,178,000
Restricted cash			32,160,000	$ 8,086,000
Future noncancelable minimum lease payments
2017			749,000
2018			607,000
2019			503,000
2020			541,000
2021			578,000
Thereafter			127,101,000
Total			130,079,000
Ground lease for one of the project
Commitments and contingencies
Current annual rent			$ 503,000
Period after which the annual rental payment will be increased by greater of 15% or 50% of the increase in the Consumer Price Index			5 years
Increase in annual rental payment after every 5 years, option one (as a percent)			15.00%
Increase in annual rental payment after every 5 years, option two (as a percent)			50.00%
Adjustment period used to calculate increase in the Consumer Price Index			5 years
Increase in rent payable during the balance of the lease term expressed as a percentage of rent payable during the immediately preceding lease year commencing on June 1, 2040 and 2065			10.00%
Rent expense			$ 1,752,000	1,752,000	$ 1,752,000
Straight line rent liability			13,289,000	12,180,000
Office space in Dallas, Texas
Commitments and contingencies
Office space rent expense			$ 226,000	235,000	175,000
Executive officers | 2015 Equity Incentive Plan
Commitments and contingencies
Number of employees covered under employment agreement | officer			2
Employment agreements | Executive officers | 2015 Equity Incentive Plan
Commitments and contingencies
Common stock issued (in shares) | shares	76,423
Accrued payroll taxes				444,000
Stock-based compensation expense			$ 0	$ 1,263,000	$ 947,000
Unrecognized compensation expense			0
Restricted cash for tenant improvement allowance
Commitments and contingencies
Restricted cash			$ 15,399,000
Scenario, Forecast [Member]
Commitments and contingencies
Income Tax Examination, Penalties and Interest Expense		$ 11,400,000