INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - Summary of Results of Operations of Real Estate Ventures with Interests (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Equity in income (loss) of Real Estate Ventures	$ (9,922)	$ (15,231)	$ (8,306)
DRA Austin Venture
Schedule of Equity Method Investments [Line Items]
Revenue		53,476	85,500
Operating expenses		(22,994)	(35,997)
Provision for impairment		0
Interest expense, net		(9,083)	(13,985)
Depreciation and amortization		(19,226)	(34,026)
Loss on extinguishment of debt		(356)	(2,613)
Net income (loss)		$ 1,817	$ (1,121)
Ownership percentage		50.00%	50.00%
Company's share of net income (loss)		$ 909	$ (560)
Other-than-temporary impairment		0	0
Basis adjustments and other		778	(429)
Equity in income (loss) of Real Estate Ventures		1,687	(989)
MAP Venture
Schedule of Equity Method Investments [Line Items]
Revenue	70,366	68,622	68,573
Operating expenses	(47,362)	(41,056)	(40,035)
Provision for impairment	0	0
Interest expense, net	(9,752)	(12,690)	(13,677)
Depreciation and amortization	(25,413)	(18,891)	(21,202)
Loss on extinguishment of debt	0	(334)	0
Net income (loss)	$ (12,161)	$ (4,349)	$ (6,341)
Ownership percentage	50.00%	50.00%	50.00%
Company's share of net income (loss)	$ (6,081)	$ (2,175)	$ (3,171)
Other-than-temporary impairment		0	0
Basis adjustments and other	(21)	20	(272)
Equity in income (loss) of Real Estate Ventures	(6,102)	(2,155)	(3,443)
Brandywine - AI Venture LLC
Schedule of Equity Method Investments [Line Items]
Revenue	6,022	23,515	29,500
Operating expenses	(2,912)	(10,483)	(12,298)
Provision for impairment	(5,664)	(20,832)
Interest expense, net	(698)	(3,478)	(4,707)
Depreciation and amortization	(2,514)	(8,991)	(11,428)
Loss on extinguishment of debt	0	(695)	(811)
Net income (loss)	$ (5,766)	$ (20,964)	$ 256
Ownership percentage	50.00%	50.00%	50.00%
Company's share of net income (loss)	$ (2,883)	$ (10,482)	$ 128
Other-than-temporary impairment		(4,076)	(4,844)
Basis adjustments and other	83	(1)	251
Equity in income (loss) of Real Estate Ventures	$ (2,800)	(14,559)	(4,465)
Evo at Cira Centre South Venture
Schedule of Equity Method Investments [Line Items]
Revenue		163	12,285
Operating expenses		(256)	(3,075)
Provision for impairment		0
Interest expense, net		(123)	(4,092)
Depreciation and amortization		(409)	(4,512)
Loss on extinguishment of debt		0	0
Net income (loss)		$ (625)	$ 606
Ownership percentage	50.00%	50.00%	50.00%
Company's share of net income (loss)		$ (313)	$ 303
Other-than-temporary impairment		0	0
Basis adjustments and other		(45)	146
Equity in income (loss) of Real Estate Ventures	$ 0	(358)	449
Other
Schedule of Equity Method Investments [Line Items]
Revenue	55,970	19,550	20,413
Operating expenses	(21,510)	(7,246)	(7,935)
Provision for impairment	0	0
Interest expense, net	(11,458)	(4,400)	(3,752)
Depreciation and amortization	(25,404)	(6,309)	(7,272)
Loss on extinguishment of debt	(1,231)	0	0
Net income (loss)	(3,633)	1,595	1,454
Company's share of net income (loss)	(901)	137	1,436
Other-than-temporary impairment		0	0
Basis adjustments and other	(119)	17	(1,294)
Equity in income (loss) of Real Estate Ventures	(1,020)	154	142
Unconsolidated Real Estate Ventures
Schedule of Equity Method Investments [Line Items]
Revenue	132,358	165,326	216,271
Operating expenses	(71,784)	(82,035)	(99,340)
Provision for impairment	(5,664)	(20,832)
Interest expense, net	(21,908)	(29,774)	(40,213)
Depreciation and amortization	(53,331)	(53,826)	(78,440)
Loss on extinguishment of debt	(1,231)	(1,385)	(3,424)
Net income (loss)	(21,560)	(22,526)	(5,146)
Company's share of net income (loss)	(9,865)	(11,924)	(1,864)
Other-than-temporary impairment		(4,076)	(4,844)
Basis adjustments and other	(57)	769	(1,598)
Equity in income (loss) of Real Estate Ventures	$ (9,922)	$ (15,231)	$ (8,306)