COMMITMENTS AND CONTINGENCIES (Details)	1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Jan. 31, 2016 shares	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) officer	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Commitments and contingencies
Outstanding loan commitments and approvals to fund loans		$ 141,748,000		$ 141,748,000
Future obligations under leases to fund tenant improvements and in other future construction obligation		33,205,000		33,205,000
Restricted cash		40,039,000		40,039,000		$ 8,086,000
Future noncancelable minimum lease payments
2016 (Three months ending December 31, 2016)		187,000		187,000
2017		749,000		749,000
2018		607,000		607,000
2019		503,000		503,000
2020		541,000		541,000
Thereafter		127,679,000		127,679,000
Total		130,266,000		130,266,000
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%
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 July 1, 2040 and 2065				10.00%
Rent expense		438,000	$ 438,000	$ 1,314,000	$ 1,314,000
Straight line rent liability		13,012,000		13,012,000		$ 12,180,000
Office space in Dallas, Texas
Commitments and contingencies
Rent expense		$ 57,000	50,000	$ 171,000	180,000
Employment agreements | Executive officers
Commitments and contingencies
Number of employees covered under employment agreement | officer				2
Multiplier used for the calculation of payments in the event of disability to employee		1		1
Multiplier used for the calculation of payments in the event of death of employee		2		2
Employment agreements | Executive officers | 2015 Equity Incentive Plan
Commitments and contingencies
Stock-based compensation expense (in shares) | shares	76,423
Accrued payroll taxes						$ 444,000
Stock-based compensation expense		$ 0	$ 316,000	$ 0	$ 948,000
Unrecognized compensation expense		0		0
Restricted cash for tenant improvement allowance
Commitments and contingencies
Restricted cash		22,129,000		22,129,000
Commercial real estate loans, subject to secured borrowings
Commitments and contingencies
Outstanding loan commitments and approvals to fund loans		122,958,000		122,958,000
Loan commitments expected to be funded by a participant through participation agreement		$ 60,250,000		$ 60,250,000