Investments in Subsidiaries - Schedule of Ownership in Each Property (Details)	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Effective ownership percentage, wholly owned subsidiary	100.00%
Arbors on Forest Ridge | Bedford | Texas
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2014
Effective ownership percentage, wholly owned subsidiary	100.00%	100.00%
Cutter's Point | Richardson | Texas
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2014
Effective ownership percentage, wholly owned subsidiary	100.00%	100.00%
Eagle Crest | Irving | Texas
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2014
Effective ownership percentage, wholly owned subsidiary	100.00%	100.00%
Silverbrook | Grand Prairie | Texas
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2014
Effective ownership percentage, wholly owned subsidiary	100.00%	100.00%
Edgewater at Sandy Springs | Atlanta | Georgia
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2014
Effective ownership percentage, wholly owned subsidiary	100.00%	100.00%
Beechwood Terrace | Antioch | Tennessee
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2014
Effective ownership percentage, wholly owned subsidiary	100.00%	100.00%
Willow Grove | Nashville | Tennessee
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2014
Effective ownership percentage, wholly owned subsidiary	100.00%	100.00%
Woodbridge | Nashville | Tennessee
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2014
Effective ownership percentage, wholly owned subsidiary	100.00%	100.00%
Abbington Heights | Antioch | Tennessee
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2014
Effective ownership percentage, wholly owned subsidiary	100.00%	100.00%
The Summit at Sabal Park | Tampa | Florida
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2014
Effective ownership percentage, wholly owned subsidiary	100.00%	100.00%
Courtney Cove | Tampa | Florida
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2014
Effective ownership percentage, wholly owned subsidiary	100.00%	100.00%
Radbourne Lake | Charlotte | North Carolina
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2014
Effective ownership percentage, wholly owned subsidiary	100.00%	100.00%
Timber Creek | Charlotte | North Carolina
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2014
Effective ownership percentage, wholly owned subsidiary	100.00%	100.00%
Belmont at Duck Creek | Garland | Texas
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2014
Effective ownership percentage, wholly owned subsidiary	100.00%	100.00%
Sabal Palm at Lake Buena Vista | Orlando | Florida
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2014
Effective ownership percentage, wholly owned subsidiary	100.00%	100.00%
Southpoint Reserve at Stoney Creek | Fredericksburg | Virginia
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2014
Effective ownership percentage, wholly owned subsidiary	100.00%	100.00%
Cornerstone | Orlando | Florida
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2015
Effective ownership percentage, wholly owned subsidiary	100.00%	100.00%
The Preserve at Terrell Mill | Marietta | Georgia
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2015
Effective ownership percentage, wholly owned subsidiary	100.00%	100.00%
The Ashlar | Dallas | Texas
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2015
Effective ownership percentage, wholly owned subsidiary	100.00%	100.00%
Heatherstone | Dallas | Texas
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2015
Effective ownership percentage, wholly owned subsidiary	100.00%	100.00%
Versailles | Dallas | Texas
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2015
Effective ownership percentage, wholly owned subsidiary	100.00%	100.00%
Seasons 704 Apartments | West Palm Beach | Florida
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2015
Effective ownership percentage, wholly owned subsidiary	100.00%	100.00%
Madera Point | Mesa | Arizona
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2015
Effective ownership percentage, wholly owned subsidiary	100.00%	100.00%
The Pointe at the Foothills | Mesa | Arizona
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2015
Effective ownership percentage, wholly owned subsidiary	100.00%	100.00%
Venue at 8651 | Fort Worth | Texas
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2015
Effective ownership percentage, wholly owned subsidiary	100.00%	100.00%
Parc500 | West Palm Beach | Florida
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2016
Effective ownership percentage, wholly owned subsidiary	100.00%	100.00%
The Colonnade | Phoenix | Arizona
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2016
Effective ownership percentage, wholly owned subsidiary	100.00%	100.00%
Old Farm | Houston | Texas
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2016
Effective ownership percentage, wholly owned subsidiary	100.00%	100.00%
Stone Creek at Old Farm | Houston | Texas
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2016
Effective ownership percentage, wholly owned subsidiary	100.00%	100.00%
Hollister Place | Houston | Texas
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2017
Effective ownership percentage, wholly owned subsidiary	100.00%	100.00%
Rockledge Apartments | Marietta | Georgia
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2017
Effective ownership percentage, wholly owned subsidiary	100.00%	100.00%
Atera Apartments | Dallas | Texas
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2017
Effective ownership percentage, wholly owned subsidiary	100.00%	100.00%
Cedar Pointe | Antioch | Tennessee
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2018
Effective ownership percentage, wholly owned subsidiary	100.00%	100.00%
Crestmont Reserve | Dallas | Texas
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2018
Effective ownership percentage, wholly owned subsidiary	100.00%	100.00%
Brandywine I & II | Nashville | Tennessee
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2018
Effective ownership percentage, wholly owned subsidiary	100.00%	100.00%
Bella Vista | Phoenix | Arizona
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2019
Effective ownership percentage, wholly owned subsidiary	100.00%
The Enclave | Tempe | Arizona
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2019
Effective ownership percentage, wholly owned subsidiary	100.00%
The Heritage | Phoenix | Arizona
Wholly Owned Subsidiaries And Variable Interest Entities [Line Items]
Year of acquisition	2019
Effective ownership percentage, wholly owned subsidiary	100.00%