REAL ESTATE HELD FOR INVESTMENT (Properties Represented More than 10% of Company’s Total Assets) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($) ft² $ / ft²	Dec. 31, 2017 USD ($)
Real Estate Properties [Line Items]
Total Real Estate, Net	$ 990,540	$ 995,247
Percentage of Total Assets	47.50%
Annualized Base Rent	$ 56,873
Occupancy	82.00%
Assets, Total | Union Bank Plaza
Real Estate Properties [Line Items]
Rentable Square Feet | ft²	627,334
Total Real Estate, Net	$ 161,361
Percentage of Total Assets	13.20%
Annualized Base Rent	$ 21,105
Average Annualized Base Rent per Sq. Ft. | $ / ft²	41.10
Occupancy	82.00%
Assets, Total | Corporate Technology Centre
Real Estate Properties [Line Items]
Rentable Square Feet | ft²	492,110
Total Real Estate, Net	$ 156,640
Percentage of Total Assets	12.80%
Annualized Base Rent	$ 14,243
Average Annualized Base Rent per Sq. Ft. | $ / ft²	36.02
Occupancy	80.00%
Assets, Total | 300-600 Campus Drive Buildings
Real Estate Properties [Line Items]
Rentable Square Feet | ft²	578,424
Total Real Estate, Net	$ 144,398
Percentage of Total Assets	11.80%
Annualized Base Rent	$ 17,865
Average Annualized Base Rent per Sq. Ft. | $ / ft²	33.63
Occupancy	92.00%
Assets, Total | 100 & 200 Campus Drive Buildings
Real Estate Properties [Line Items]
Rentable Square Feet | ft²	589,625
Total Real Estate, Net	$ 137,621
Percentage of Total Assets	11.20%
Annualized Base Rent	$ 12,062
Average Annualized Base Rent per Sq. Ft. | $ / ft²	30.31
Occupancy	67.00%