Summary of Significant Accounting Policies - Variable Interest Entities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Variable Interest Entity [Line Items]
Real estate, net	$ 2,555,659	$ 3,309,900
Total assets	2,953,840	3,553,020
Mortgages and notes payable, net	570,420	689,810
Total liabilities	1,607,162	2,212,185
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Real estate, net	509,916	682,587
Total assets	607,963	766,025
Mortgages and notes payable, net	192,791	212,792
Total liabilities	$ 203,322	$ 226,331