Investment in Unconsolidated Real Estate Ventures - Summary of Financial Position of Real Estate Ventures (Details) - USD ($) $ in Thousands		Mar. 31, 2018		Dec. 31, 2017
Schedule Of Equity Method Investments [Line Items]
Net property		$ 910,767		$ 1,083,965
Other assets		143,692		161,932
Other liabilities		94,162		97,707
Debt, net		635,319		766,420
Equity	[1]	324,978		381,770
DRA Austin Venture [Member]
Schedule Of Equity Method Investments [Line Items]
Net property		263,384		263,557
Other assets		35,080		42,272
Other liabilities		17,189		24,131
Debt, net		247,844		248,700
Equity	[1]	33,431		32,998
BDN - Al Venture [Member]
Schedule Of Equity Method Investments [Line Items]
Net property		159,159		158,960
Other assets		24,520		24,181
Other liabilities		4,844		4,493
Debt, net		92,813		92,917
Equity	[1]	86,022		85,731
HSRE-BDN I, LLC (evo at Cira Centre South) [Member]
Schedule Of Equity Method Investments [Line Items]
Net property		0	[2]	143,990
Other assets		0	[2]	8,563
Other liabilities		0	[2]	1,648
Debt, net		0	[2]	110,136
Equity	[1]	0	[2]	40,769
Other [Member]
Schedule Of Equity Method Investments [Line Items]
Net property		488,224		517,458
Other assets		84,092		86,916
Other liabilities		72,129		67,435
Debt, net		294,662		314,667
Equity	[1]	$ 205,525		$ 222,272

[1] This amount includes the effect of the basis difference between the Company's historical cost basis and the basis recorded at the Real Estate Venture level, which is typically amortized over the life of the related assets and liabilities. Basis differentials occur from the impairment of investments, purchases of third party interests in existing Real Estate Ventures and upon the transfer of assets that were previously owned by the Company into a Real Estate Venture. In addition, certain acquisition, transaction and other costs may not be reflected in the net assets at the Real Estate Venture level.

[2] On January 10, 2018, evo at Cira sold the 345-unit student housing tower, its sole operating asset. See ‘evo at Cira Disposition’ section below.