Debt - Summary of Mortgage Debt Nonrecourse to Company and Encumbers Multifamily Properties (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Mortgages payable, net	$ 903,143	$ 824,702
Mortgages Payable | Operating Properties
Debt Instrument [Line Items]
Outstanding Principal	911,129
Fair market value adjustment	608
Deferred financing costs, net of accumulated amortization	(8,594)
Mortgages payable, net	$ 903,143
Mortgages Payable | Arbors on Forest Ridge | Debt With Floating Interest Rate
Debt Instrument [Line Items]
Term (months)	84 months
Outstanding Principal	$ 13,130
Interest Rate	4.17%
Maturity Date	Jul. 01, 2024
Mortgages Payable | Cutter's Point | Debt With Floating Interest Rate
Debt Instrument [Line Items]
Term (months)	84 months
Outstanding Principal	$ 16,640
Interest Rate	4.17%
Maturity Date	Jul. 01, 2024
Mortgages Payable | Eagle Crest | Debt With Floating Interest Rate
Debt Instrument [Line Items]
Term (months)	84 months
Outstanding Principal	$ 29,510
Interest Rate	4.17%
Maturity Date	Jul. 01, 2024
Mortgages Payable | Silverbrook | Debt With Floating Interest Rate
Debt Instrument [Line Items]
Term (months)	84 months
Outstanding Principal	$ 30,590
Interest Rate	4.17%
Maturity Date	Jul. 01, 2024
Mortgages Payable | Edgewater at Sandy Springs | Debt With Floating Interest Rate
Debt Instrument [Line Items]
Term (months)	84 months
Outstanding Principal	$ 52,000
Interest Rate	4.17%
Maturity Date	Jul. 01, 2024
Mortgages Payable | Beechwood Terrace | Debt With Floating Interest Rate
Debt Instrument [Line Items]
Term (months)	84 months
Outstanding Principal	$ 23,365
Interest Rate	3.93%
Maturity Date	Sep. 01, 2025
Mortgages Payable | Willow Grove | Debt With Floating Interest Rate
Debt Instrument [Line Items]
Term (months)	84 months
Outstanding Principal	$ 14,818
Interest Rate	4.27%
Maturity Date	Jul. 01, 2024
Mortgages Payable | Woodbridge | Debt With Floating Interest Rate
Debt Instrument [Line Items]
Term (months)	84 months
Outstanding Principal	$ 13,677
Interest Rate	4.27%
Maturity Date	Jul. 01, 2024
Mortgages Payable | The Summit at Sabal Park | Debt With Floating Interest Rate
Debt Instrument [Line Items]
Term (months)	84 months
Outstanding Principal	$ 13,560
Interest Rate	4.11%
Maturity Date	Jul. 01, 2024
Mortgages Payable | Courtney Cove | Debt With Floating Interest Rate
Debt Instrument [Line Items]
Term (months)	84 months
Outstanding Principal	$ 13,680
Interest Rate	4.11%
Maturity Date	Jul. 01, 2024
Mortgages Payable | The Preserve at Terrell Mill | Debt With Floating Interest Rate
Debt Instrument [Line Items]
Term (months)	84 months
Outstanding Principal	$ 42,480
Interest Rate	4.11%
Maturity Date	Jul. 01, 2024
Mortgages Payable | The Ashlar | Debt With Floating Interest Rate
Debt Instrument [Line Items]
Term (months)	84 months
Outstanding Principal	$ 14,520
Interest Rate	4.11%
Maturity Date	Jul. 01, 2024
Mortgages Payable | Heatherstone | Debt With Floating Interest Rate
Debt Instrument [Line Items]
Term (months)	84 months
Outstanding Principal	$ 8,880
Interest Rate	4.11%
Maturity Date	Jul. 01, 2024
Mortgages Payable | Versailles | Debt With Floating Interest Rate
Debt Instrument [Line Items]
Term (months)	84 months
Outstanding Principal	$ 23,880
Interest Rate	4.11%
Maturity Date	Jul. 01, 2024
Mortgages Payable | Seasons 704 Apartments | Debt With Floating Interest Rate
Debt Instrument [Line Items]
Term (months)	84 months
Outstanding Principal	$ 17,460
Interest Rate	4.11%
Maturity Date	Jul. 01, 2024
Mortgages Payable | Madera Point | Debt With Floating Interest Rate
Debt Instrument [Line Items]
Term (months)	84 months
Outstanding Principal	$ 15,150
Interest Rate	4.11%
Maturity Date	Jul. 01, 2024
Mortgages Payable | The Pointe at the Foothills | Debt With Floating Interest Rate
Debt Instrument [Line Items]
Term (months)	84 months
Outstanding Principal	$ 34,800
Interest Rate	4.11%
Maturity Date	Jul. 01, 2024
Mortgages Payable | Venue at 8651 | Debt With Floating Interest Rate
Debt Instrument [Line Items]
Term (months)	84 months
Outstanding Principal	$ 13,734
Interest Rate	4.27%
Maturity Date	Jul. 01, 2024
Mortgages Payable | The Colonnade | Debt With Floating Interest Rate
Debt Instrument [Line Items]
Term (months)	84 months
Outstanding Principal	$ 28,093
Interest Rate	4.17%
Maturity Date	Jul. 01, 2024
Mortgages Payable | Old Farm | Debt With Floating Interest Rate
Debt Instrument [Line Items]
Term (months)	84 months
Outstanding Principal	$ 52,886
Interest Rate	4.17%
Maturity Date	Jul. 01, 2024
Mortgages Payable | Stone Creek at Old Farm | Debt With Floating Interest Rate
Debt Instrument [Line Items]
Term (months)	84 months
Outstanding Principal	$ 15,274
Interest Rate	4.17%
Maturity Date	Jul. 01, 2024
Mortgages Payable | Timber Creek | Debt With Floating Interest Rate
Debt Instrument [Line Items]
Term (months)	84 months
Outstanding Principal	$ 24,100
Interest Rate	3.75%
Maturity Date	Oct. 01, 2025
Mortgages Payable | Radbourne Lake | Debt With Floating Interest Rate
Debt Instrument [Line Items]
Term (months)	84 months
Outstanding Principal	$ 20,000
Interest Rate	3.78%
Maturity Date	Oct. 01, 2025
Mortgages Payable | Sabal Palm at Lake Buena Vista | Debt With Floating Interest Rate
Debt Instrument [Line Items]
Term (months)	84 months
Outstanding Principal	$ 42,100
Interest Rate	3.79%
Maturity Date	Sep. 01, 2025
Mortgages Payable | Abbington Heights | Debt With Floating Interest Rate
Debt Instrument [Line Items]
Term (months)	84 months
Outstanding Principal	$ 16,920
Interest Rate	3.74%
Maturity Date	Sep. 01, 2025
Mortgages Payable | Belmont at Duck Creek | Debt With Floating Interest Rate
Debt Instrument [Line Items]
Term (months)	84 months
Outstanding Principal	$ 17,760
Interest Rate	3.88%
Maturity Date	Jun. 01, 2025
Mortgages Payable | Cornerstone | Debt With Fixed Interest Rate
Debt Instrument [Line Items]
Term (months)	120 months
Outstanding Principal	$ 22,112
Interest Rate	4.24%
Maturity Date	Mar. 01, 2023
Mortgages Payable | Parc500 | Debt With Fixed Interest Rate
Debt Instrument [Line Items]
Term (months)	120 months
Outstanding Principal	$ 15,416
Interest Rate	4.49%
Maturity Date	Aug. 01, 2025
Mortgages Payable | Hollister Place | Debt With Floating Interest Rate
Debt Instrument [Line Items]
Term (months)	84 months
Outstanding Principal	$ 14,811
Interest Rate	3.83%
Maturity Date	Oct. 01, 2025
Mortgages Payable | Rockledge Apartments | Debt With Floating Interest Rate
Debt Instrument [Line Items]
Term (months)	84 months
Outstanding Principal	$ 68,100
Interest Rate	4.06%
Maturity Date	Jul. 01, 2024
Mortgages Payable | Atera Apartments | Debt With Floating Interest Rate
Debt Instrument [Line Items]
Term (months)	84 months
Outstanding Principal	$ 29,500
Interest Rate	3.97%
Maturity Date	Nov. 01, 2024
Mortgages Payable | Cedar Pointe | Debt With Floating Interest Rate
Debt Instrument [Line Items]
Term (months)	84 months
Outstanding Principal	$ 17,300
Interest Rate	3.84%
Maturity Date	Sep. 01, 2025
Mortgages Payable | Crestmont Reserve | Debt With Floating Interest Rate
Debt Instrument [Line Items]
Term (months)	84 months
Outstanding Principal	$ 12,061
Interest Rate	3.67%
Maturity Date	Oct. 01, 2025
Mortgages Payable | Brandywine I & II | Debt With Floating Interest Rate
Debt Instrument [Line Items]
Term (months)	84 months
Outstanding Principal	$ 43,835
Interest Rate	3.67%
Maturity Date	Oct. 01, 2025
Mortgages Payable | Bella Vista | Debt With Floating Interest Rate
Debt Instrument [Line Items]
Term (months)	84 months
Outstanding Principal	$ 29,040
Interest Rate	3.81%
Maturity Date	Feb. 01, 2026
Mortgages Payable | The Enclave | Debt With Floating Interest Rate
Debt Instrument [Line Items]
Term (months)	84 months
Outstanding Principal	$ 25,322
Interest Rate	3.81%
Maturity Date	Feb. 01, 2026
Mortgages Payable | The Heritage | Debt With Floating Interest Rate
Debt Instrument [Line Items]
Term (months)	84 months
Outstanding Principal	$ 24,625
Interest Rate	3.81%
Maturity Date	Feb. 01, 2026
Mortgages Payable | Held For Sale Properties
Debt Instrument [Line Items]
Deferred financing costs, net of accumulated amortization	$ (65)
Mortgages payable, net	$ 13,269
Mortgages Payable | Held For Sale Properties | Southpoint Reserve at Stoney Creek | Debt With Floating Interest Rate
Debt Instrument [Line Items]
Term (months)	84 months
Outstanding Principal	$ 13,334
Interest Rate	4.60%
Maturity Date	Jan. 01, 2022