SEGMENT DISCLOSURE (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	Dec. 31, 2015 USD ($) item	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Segment disclosure
Number of types of commercial real estate properties | item									3
Revenues	$ 67,874	$ 66,395	$ 66,919	$ 67,239	$ 65,252	$ 63,117	$ 65,187	$ 62,597	$ 268,427	$ 256,153	$ 235,813
Property expenses:
General and administrative									8,370	7,332	2,568
EXPENSES									267,395	249,111	221,134
Reportable segments
Property expenses:
Total segment net operating income									133,500	127,410	129,208
Reportable segments | Office
Segment disclosure
Revenues									188,270	179,338	175,144
Property expenses:
Operating									80,014	73,666	67,906
General and administrative									771	981	1,078
EXPENSES									80,785	74,647	68,984
Total segment net operating income									107,485	104,691	106,160
Reportable segments | Hotel
Segment disclosure
Revenues									61,436	56,096	40,680
Property expenses:
Operating									41,585	39,544	28,825
General and administrative									389	150	250
EXPENSES									41,974	39,694	29,075
Total segment net operating income									19,462	16,402	11,605
Reportable segments | Multi-family
Segment disclosure
Revenues									18,721	20,719	19,989
Property expenses:
Operating									11,579	13,664	8,432
General and administrative									589	738	114
EXPENSES									12,168	14,402	8,546
Total segment net operating income									$ 6,553	$ 6,317	$ 11,443