Commitments and Contingencies - Guarantor (Details) - USD ($)	Feb. 28, 2019	Feb. 08, 2019	Jan. 08, 2019	Dec. 31, 2018	Dec. 31, 2017	Nov. 10, 2016
Guarantor Obligations [Line Items]
Indebtedness, net				$ 694,239,000	$ 517,272,000
Financial Guarantee
Guarantor Obligations [Line Items]
Guarantor obligations				56,507,000
1405 Point | Financial Guarantee
Guarantor Obligations [Line Items]
Guarantor obligations				25,000,000		$ 25,000,000.0
The Residences at Annapolis Junction | Financial Guarantee
Guarantor Obligations [Line Items]
Guarantor obligations				8,300,000
Delray Plaza | Financial Guarantee
Guarantor Obligations [Line Items]
Guarantor obligations				4,750,000
Nexton Square | Financial Guarantee
Guarantor Obligations [Line Items]
Guarantor obligations				0
Interlock Commercial | Financial Guarantee
Guarantor Obligations [Line Items]
Guarantor obligations				0
Solis Apartments At Interlock | Financial Guarantee
Guarantor Obligations [Line Items]
Guarantor obligations				0
Durham City Center II LLC | Financial Guarantee
Guarantor Obligations [Line Items]
Guarantor obligations				$ 18,457,000
Subsequent Event | Delray Plaza | Financial Guarantee
Guarantor Obligations [Line Items]
Guarantor obligations			$ 5,200,000
Subsequent Event | Nexton Square | Financial Guarantee
Guarantor Obligations [Line Items]
Guarantor obligations		$ 12,600,000
Forecast | Interlock Commercial | Financial Guarantee
Guarantor Obligations [Line Items]
Guarantor obligations	$ 30,700,000