Variable Interest Entities ("VIEs") - Summary of Investments in Unconsolidated Real Estate Funds and Maximum Risk of Loss from Investments (Details) - Unconsolidated Real Estate Funds [Member] - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Carrying Value of Investments [Member]
Variable Interest Entity [Line Items]
Investments in unconsolidated real estate funds	$ 11,582	$ 10,352
Asset Management Fees and Other Receivables [Member]
Variable Interest Entity [Line Items]
Investments in unconsolidated real estate funds	549	722
Maximum Risk of Loss [Member]
Variable Interest Entity [Line Items]
Investments in unconsolidated real estate funds	$ 12,131	$ 11,074