LONG-TERM DEBT - Schedule of Long-Term Debt - Outstanding Indebtedness (Details)	9 Months Ended
	Sep. 30, 2017 USD ($) property building	Mar. 11, 2015 USD ($)
Long-term debt
Face Value of Debt	$ 178,300,000
Credit Facility
Long-term debt
Face Value of Debt	$ 41,000,000
Credit Facility | LIBOR | Minimum
Long-term debt
Margin added to variable rate basis (as a percent)	1.50%
Credit Facility | LIBOR | Maximum
Long-term debt
Margin added to variable rate basis (as a percent)	2.20%
UBS Mortgage Note Payable
Long-term debt
Face Value of Debt	$ 7,300,000
Stated interest rate (as a percent)	3.655%
Number of buildings securing debt | building	2
Wells Fargo Mortgage Note Payable Originated September 30, 2014
Long-term debt
Face Value of Debt	$ 30,000,000
Stated interest rate (as a percent)	4.33%
Number of income properties securing debt | property	6
Period of fixed interest rate	10 years
Period of interest only payments	10 years
Period after which cash flows generated by underlying income properties must be used to pay down principal balance	10 years
Period to when loan is pre-payable	10 years
Wells Fargo Mortgage Note Payable Originated April 15, 2016
Long-term debt
Face Value of Debt	$ 25,000,000
Term of mortgage loan	5 years
Period of interest only payments	2 years
Period of amortization for principal payments	25 years
Fixed interest rate through use of interest rate swap (as a percent)	3.17%
Wells Fargo Mortgage Note Payable Originated April 15, 2016 | LIBOR
Long-term debt
Margin added to variable rate basis (as a percent)	1.90%
4.50% Convertible Senior Notes due 2020
Long-term debt
Face Value of Debt	$ 75,000,000	$ 75,000,000
Stated interest rate (as a percent)	4.50%