Fair Value Measurements - Summary of Carrying Amounts and Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Total assets	$ 55,797	$ 38,894
Total liabilities		317
Carrying Amount [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Preferred equity investments, net	35,925	35,817
Total assets	35,925	35,817
Notes and mortgages payable	3,599,800	3,583,100
Total liabilities	3,599,800	3,583,100
Fair Value [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Preferred equity investments, net	36,212	36,112
Total assets	36,212	36,112
Notes and mortgages payable	3,591,251	3,596,953
Total liabilities	$ 3,591,251	$ 3,596,953