REAL ESTATE HELD FOR INVESTMENT - Schedule of Real Estate Investments (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Dec. 31, 2019
Real Estate Properties [Line Items]
Total Real Estate at Cost	$ 163,249	$ 173,131
Accumulated Depreciation and Amortization	(19,967)	$ (22,688)
Total Real Estate, Net	$ 143,282
Commonwealth Building \| Office Building
Real Estate Properties [Line Items]
Date Acquired	Jun. 30, 2016
Total Real Estate at Cost	$ 78,863
Accumulated Depreciation and Amortization	(11,905)
Total Real Estate, Net	$ 66,958
The Offices at Greenhouse \| Office Building
Real Estate Properties [Line Items]
Date Acquired	Nov. 14, 2016
Total Real Estate at Cost	$ 47,166
Accumulated Depreciation and Amortization	(8,062)
Total Real Estate, Net	$ 39,104
Institute Property \| Office Building
Real Estate Properties [Line Items]
Date Acquired	Nov. 09, 2017
Total Real Estate at Cost	$ 37,220
Accumulated Depreciation and Amortization	0
Total Real Estate, Net	$ 37,220

Date when the acquirer obtains control of the acquiree, in CCYY-MM-DD format.

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The cumulative amount of depreciation for real estate property held for investment purposes.

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Amount of real estate investment property which may include the following: (1) land available-for-sale; (2) land available-for-development; (3) investments in building and building improvements; (4) tenant allowances; (5) developments in-process; (6) rental properties; and (7) other real estate investments.

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Amount of real estate investment property, net of accumulated depreciation, which may include the following: (1) land available-for-sale; (2) land available-for-development; (3) investments in building and building improvements; (4) tenant allowances; (5) developments in-process; (6) rental properties; and (7) other real estate investments.

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