Subsequent Events - Narrative - Sales (Details)	Dec. 31, 2018 apartment	Feb. 28, 2018 USD ($)	Jan. 31, 2018 USD ($)	Jan. 05, 2018 USD ($)	Nov. 20, 2013 apartment	Nov. 30, 2012 apartment
Subsequent Event [Line Items]
Number of units in real estate property (in number of units or apartments)	744
The Moorings Property [Member] | Discontinued Operations, Disposed of by Sale [Member]
Subsequent Event [Line Items]
Number of units in real estate property (in number of units or apartments)						216
Consideration | $				$ 28,100,000
Arrowhead Property [Member] | Discontinued Operations, Disposed of by Sale [Member]
Subsequent Event [Line Items]
Number of units in real estate property (in number of units or apartments)						200
Consideration | $			$ 23,600,000
Willow Crossing [Member] | Discontinued Operations, Disposed of by Sale [Member]
Subsequent Event [Line Items]
Number of units in real estate property (in number of units or apartments)					579
Consideration | $		$ 79,000,000