Investment in Unconsolidated Real Estate Ventures - Summary of Results of Operations of Real Estate Ventures with Interests (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Schedule Of Equity Method Investments [Line Items]
Equity in income (loss) of Real Estate Ventures		$ (1,358)	$ (825)
evo at Cira Centre South [Member]
Schedule Of Equity Method Investments [Line Items]
Revenue	[1]	0	995
Operating expenses	[1]	0	(250)
Interest expense, net	[1]	0	(388)
Depreciation and amortization	[1]	0	(376)
Loss on early extinguishment of debt	[1]		(718)
Net income (loss)	[1]	$ 0	$ (737)
Ownership interest %	[1]	50.00%	50.00%
Company's share of net income (loss)	[1]	$ 0	$ (369)
Basis adjustments and other	[1]	0	11
Equity in income (loss) of Real Estate Ventures	[1]	0	(358)
MAP Venture [Member]
Schedule Of Equity Method Investments [Line Items]
Revenue		18,288	17,080
Operating expenses		(12,155)	(10,307)
Interest expense, net		(2,536)	(3,791)
Depreciation and amortization		(6,349)	(4,701)
Loss on early extinguishment of debt			0
Net income (loss)		$ (2,752)	$ (1,719)
Ownership interest %		50.00%	50.00%
Company's share of net income (loss)		$ (1,376)	$ (860)
Basis adjustments and other		(56)	7
Equity in income (loss) of Real Estate Ventures		(1,432)	(853)
Other [Member]
Schedule Of Equity Method Investments [Line Items]
Revenue		16,771	24,746
Operating expenses		(6,563)	(10,211)
Interest expense, net		(1,384)	(3,947)
Depreciation and amortization		(7,363)	(9,307)
Loss on early extinguishment of debt			0
Net income (loss)		1,461	1,281
Company's share of net income (loss)		64	523
Basis adjustments and other		10	(137)
Equity in income (loss) of Real Estate Ventures		74	386
Unconsolidated Real Estate Ventures [Member]
Schedule Of Equity Method Investments [Line Items]
Revenue		35,059	42,821
Operating expenses		(18,718)	(20,768)
Interest expense, net		(3,920)	(8,126)
Depreciation and amortization		(13,712)	(14,384)
Loss on early extinguishment of debt			(718)
Net income (loss)		(1,291)	(1,175)
Company's share of net income (loss)		(1,312)	(706)
Basis adjustments and other		(46)	(119)
Equity in income (loss) of Real Estate Ventures		$ (1,358)	$ (825)

[1] The Company sold its 50% ownership interest in evo at Cira Centre South Venture during the first quarter of 2018.