Variable Interest Entities ("VIEs") - Summary of Investments in Unconsolidated Real Estate Funds and Maximum Risk of Loss from Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Variable Interest Entity [Line Items]
Investments in unconsolidated real estate funds	$ 10,352	$ 7,253
Investment [Member]
Variable Interest Entity [Line Items]
Investments in unconsolidated real estate funds	10,352	7,253
Asset Management Fees and Other Receivables [Member]
Variable Interest Entity [Line Items]
Investments in unconsolidated real estate funds	722	597
Maximum Risk of Loss [Member]
Variable Interest Entity [Line Items]
Investments in unconsolidated real estate funds	$ 11,074	$ 7,850