Investment in Unconsolidated Joint Ventures (Narrative) (Details) - HICO Avalon II, LLC - ft² ft² in Thousands	6 Months Ended
	Jun. 30, 2018	Sep. 30, 2018
Schedule of Equity Method Investments [Line Items]
Area of property (in sq ft)		251
Predevelopment costs, funding percentage	75.00%
Development costs, funding percentage	90.00%
Hines II
Schedule of Equity Method Investments [Line Items]
Predevelopment costs, funding percentage	25.00%
Development costs, funding percentage	10.00%