Use of Special Purpose Entities (SPE) and Variable Interest Entities (VIE) - Fair Value of Assets and Liabilities Transferred (Details) $ in Thousands	Dec. 31, 2018 securitization	Mar. 31, 2017 USD ($)	May 16, 2016 USD ($)
Variable Interest Entity [Line Items]
Total liabilities assumed			$ 11,363
Riverchase Landing and The Clusters
Variable Interest Entity [Line Items]
Cash		$ 112
Operating real estate		62,322
Lease intangibles		5,340
Receivables and other assets		2,260
Total assets		70,034
Mortgages payable		51,570
Accrued expenses and other liabilities		1,519
Total liabilities assumed		53,089
Non-controlling interest		4,462
Net assets consolidated		$ 12,483
K-Series | Multi-family CMBS Re-securitization
Variable Interest Entity [Line Items]
Number Of Securities Not Held In Financing VIE | securitization	8