Investment in Unconsolidated Real Estate Ventures - Summary of Results of Operations of Real Estate Ventures with Interests (Details) - USD ($) $ in Thousands		3 Months Ended				6 Months Ended
		Jun. 30, 2019		Jun. 30, 2018		Jun. 30, 2019		Jun. 30, 2018		Mar. 31, 2018
Schedule Of Equity Method Investments [Line Items]
Equity in income (loss) of Real Estate Ventures		$ (1,491)		$ (358)		$ (2,849)		$ (1,183)
evo at Cira Centre South [Member]
Schedule Of Equity Method Investments [Line Items]
Revenue	[1]	0		0		0		995
Operating expenses	[1]	0		0		0		(250)
Interest expense, net	[1]	0		0		0		(388)
Depreciation and amortization	[1]	$ 0		$ 0		$ 0		(376)
Loss on early extinguishment of debt	[1]							(718)
Net income (loss)	[1]							$ (737)
Ownership interest %		50.00%	[1]	50.00%	[1]	50.00%	[1]	50.00%	[1]	50.00%
Company's share of net income (loss)	[1]	$ 0		$ 0		$ 0		$ (369)
Basis adjustments and other	[1]	0		0		0		11
Equity in income (loss) of Real Estate Ventures	[1]	0		0		0		(358)
MAP Venture [Member]
Schedule Of Equity Method Investments [Line Items]
Revenue		17,796		16,653		36,084		33,733
Operating expenses		(11,611)		(9,821)		(23,766)		(20,128)
Interest expense, net		(2,532)		(3,741)		(5,068)		(7,532)
Depreciation and amortization		(6,550)		(4,741)		(12,899)		(9,442)
Net income (loss)		$ (2,897)		$ (1,650)		$ (5,649)		$ (3,369)
Ownership interest %		50.00%		50.00%		50.00%		50.00%
Company's share of net income (loss)		$ (1,449)		$ (825)		$ (2,825)		$ (1,685)
Basis adjustments and other		15		(31)		(41)		(24)
Equity in income (loss) of Real Estate Ventures		(1,434)		(856)		(2,866)		(1,709)
Other [Member]
Schedule Of Equity Method Investments [Line Items]
Revenue		15,567		24,448		32,338		49,194
Operating expenses		(5,757)		(10,268)		(12,320)		(20,479)
Interest expense, net		(3,788)		(14,411)		(5,172)		(8,158)
Depreciation and amortization		(6,922)		(9,051)		(14,285)		(18,358)
Net income (loss)		(900)		(9,282)		561		2,199
Company's share of net income (loss)		(59)		348		5		871
Basis adjustments and other		2		150		12		13
Equity in income (loss) of Real Estate Ventures		(57)		498		17		884
Unconsolidated Real Estate Ventures [Member]
Schedule Of Equity Method Investments [Line Items]
Revenue		33,363		41,101		68,422		83,922
Operating expenses		(17,368)		(20,089)		(36,086)		(40,857)
Interest expense, net		(6,320)		(18,152)		(10,240)		(16,078)
Depreciation and amortization		(13,472)		(13,792)		(27,184)		(28,176)
Loss on early extinguishment of debt								(718)
Net income (loss)		(3,797)		(10,932)		(5,088)		(1,907)
Company's share of net income (loss)		(1,508)		(477)		(2,820)		(1,183)
Basis adjustments and other		17		119		(29)		0
Equity in income (loss) of Real Estate Ventures		$ (1,491)		$ (358)		$ (2,849)		$ (1,183)

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