Investment in Unconsolidated Real Estate Ventures - Summary of Financial Position of Real Estate Ventures (Details) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Schedule Of Equity Method Investments [Line Items]
Net property		$ 1,083,965	$ 1,457,003
Other assets		161,932	229,917
Other liabilities		97,707	129,687
Debt, net		766,420	989,738
Equity	[1]	381,770	567,495
DRA Austin Venture [Member]
Schedule Of Equity Method Investments [Line Items]
Net property		263,557	493,960
Other assets		42,272	82,725
Other liabilities		24,131	40,280
Debt, net		248,700	403,671
Equity	[1]	32,998	132,734
Other [Member]
Schedule Of Equity Method Investments [Line Items]
Net property		661,448	733,883
Other assets		95,479	113,987
Other liabilities		69,083	82,967
Debt, net		424,803	454,906
Equity	[1]	263,041	309,997
BDN - Al Venture [Member]
Schedule Of Equity Method Investments [Line Items]
Net property		158,960	229,160
Other assets		24,181	33,205
Other liabilities		4,493	6,440
Debt, net		92,917	131,161
Equity	[1]	$ 85,731	$ 124,764

[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.