Mortgage Notes Payable, Net - Summary of Mortgage Notes Payable (Details) - USD ($) $ in Thousands		9 Months Ended
		Sep. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Outstanding borrowings		$ 546,016
Deferred Finance Costs, net		(3,608)
Carrying Value		542,525	$ 547,875
Mortgage notes payable
Debt Instrument [Line Items]
Outstanding borrowings		546,016	552,074
Premium, net		117	200
Deferred Finance Costs, net		(3,608)	(4,399)
Carrying Value		542,525	547,875
Mortgage notes payable | Uptown Buckhead
Debt Instrument [Line Items]
Outstanding borrowings		18,973	19,264
Deferred Finance Costs, net		(153)	(178)
Carrying Value		$ 18,820	19,086
Maturity Date	[1],[2],[3]	Jul. 01, 2025
Annual Interest Rate	[1],[2],[3]	2.37%
Average Monthly Debt Service	[1],[2],[3]	$ 70
Average Monthly Escrow	[1],[2],[3]	$ 52
Mortgage notes payable | Uptown Buckhead | LIBOR
Debt Instrument [Line Items]
Margin over LIBOR	[1],[2],[3]	2.22%
Mortgage notes payable | Crosstown at Chapel Hill
Debt Instrument [Line Items]
Outstanding borrowings		$ 42,650	42,650
Deferred Finance Costs, net		(279)	(325)
Carrying Value		$ 42,371	42,325
Maturity Date	[2],[3],[4]	Jul. 01, 2025
Annual Interest Rate	[2],[3],[4]	1.92%
Average Monthly Debt Service	[2],[3],[4]	$ 84
Average Monthly Escrow	[2],[3],[4]	$ 75
Mortgage notes payable | Crosstown at Chapel Hill | LIBOR
Debt Instrument [Line Items]
Margin over LIBOR	[2],[3],[4]	1.77%
Mortgage notes payable | The Brookwood - Key Bank
Debt Instrument [Line Items]
Outstanding borrowings		$ 16,743	17,063
Premium, net		109	186
Deferred Finance Costs, net		(51)	(88)
Carrying Value		$ 16,801	17,161
Maturity Date	[5],[6]	Nov. 01, 2021
Annual Interest Rate	[5],[6]	4.73%
Average Monthly Debt Service	[5],[6]	$ 104
Average Monthly Escrow	[5],[6]	65
Mortgage notes payable | The Brookwood - Capital One
Debt Instrument [Line Items]
Outstanding borrowings		2,530	2,566
Premium, net		8	14
Deferred Finance Costs, net		(9)	(15)
Carrying Value		$ 2,529	2,565
Maturity Date	[5],[6]	Nov. 01, 2021
Annual Interest Rate	[5],[6]	5.40%
Average Monthly Debt Service	[5],[6]	$ 16
Mortgage notes payable | Adair off Addison and Adair off Addison Apartment Homes
Debt Instrument [Line Items]
Outstanding borrowings		33,210	33,210
Deferred Finance Costs, net		(333)	(380)
Carrying Value		$ 32,877	32,830
Maturity Date	[2],[3],[4]	May 01, 2026
Annual Interest Rate	[2],[3],[4]	1.79%
Average Monthly Debt Service	[2],[3],[4]	$ 73
Average Monthly Escrow	[2],[3],[4]	$ 74
Mortgage notes payable | Adair off Addison and Adair off Addison Apartment Homes | LIBOR
Debt Instrument [Line Items]
Margin over LIBOR	[2],[3],[4]	1.64%
Mortgage notes payable | 1000 Spalding Crossing
Debt Instrument [Line Items]
Outstanding borrowings		$ 23,381	23,737
Deferred Finance Costs, net		(70)	(113)
Carrying Value		$ 23,311	23,624
Maturity Date	[5],[6]	Jan. 01, 2022
Annual Interest Rate	[5],[6]	3.88%
Average Monthly Debt Service	[5],[6]	$ 116
Average Monthly Escrow	[5],[6]	51
Mortgage notes payable | Ravina Apartment Homes
Debt Instrument [Line Items]
Outstanding borrowings		25,694	26,241
Deferred Finance Costs, net		(111)	(165)
Carrying Value		$ 25,583	26,076
Maturity Date	[5],[6]	May 01, 2022
Annual Interest Rate	[5],[6]	3.76%
Average Monthly Debt Service	[5],[6]	$ 144
Average Monthly Escrow	[5],[6]	151
Mortgage notes payable | Verdant Apartment Homes
Debt Instrument [Line Items]
Outstanding borrowings		36,402	36,913
Deferred Finance Costs, net		(137)	(178)
Carrying Value		$ 36,265	36,735
Maturity Date	[5],[6]	May 01, 2023
Annual Interest Rate	[5],[6]	3.89%
Average Monthly Debt Service	[5],[6]	$ 176
Average Monthly Escrow	[5],[6]	35
Mortgage notes payable | Arcadia Apartment Homes
Debt Instrument [Line Items]
Outstanding borrowings		39,232	39,782
Deferred Finance Costs, net		(150)	(195)
Carrying Value		$ 39,082	39,587
Maturity Date	[5],[6]	May 01, 2023
Annual Interest Rate	[5],[6]	3.89%
Average Monthly Debt Service	[5],[6]	$ 189
Average Monthly Escrow	[5],[6]	38
Mortgage notes payable | Grand Reserve
Debt Instrument [Line Items]
Outstanding borrowings		47,845	47,845
Deferred Finance Costs, net		(489)	(539)
Carrying Value		$ 47,356	47,306
Maturity Date	[2],[3],[4]	May 01, 2028
Annual Interest Rate	[2],[3],[4]	1.87%
Average Monthly Debt Service	[2],[3],[4]	$ 76
Average Monthly Escrow	[2],[3],[4]	$ 90
Mortgage notes payable | Grand Reserve | LIBOR
Debt Instrument [Line Items]
Margin over LIBOR	[2],[3],[4]	1.72%
Mortgage notes payable | Montclair Terrace
Debt Instrument [Line Items]
Outstanding borrowings		$ 19,612	19,958
Deferred Finance Costs, net		(141)	(182)
Carrying Value		$ 19,471	19,776
Maturity Date	[2],[3],[5]	Jun. 01, 2023
Annual Interest Rate	[2],[3],[5]	2.60%
Average Monthly Debt Service	[2],[3],[5]	$ 80
Average Monthly Escrow	[2],[3],[5]	$ 27
Mortgage notes payable | Montclair Terrace | LIBOR
Debt Instrument [Line Items]
Margin over LIBOR	[2],[3],[5]	2.45%
Mortgage notes payable | 81 Fifty at West Hills Apartment Homes
Debt Instrument [Line Items]
Outstanding borrowings		$ 51,022	51,833
Deferred Finance Costs, net		(287)	(368)
Carrying Value		$ 50,735	51,465
Maturity Date	[2],[3],[5]	Jul. 01, 2023
Annual Interest Rate	[2],[3],[5]	2.51%
Average Monthly Debt Service	[2],[3],[5]	$ 205
Average Monthly Escrow	[2],[3],[5]	$ 58
Mortgage notes payable | 81 Fifty at West Hills Apartment Homes | LIBOR
Debt Instrument [Line Items]
Margin over LIBOR	[2],[3],[5]	2.36%
Mortgage notes payable | The Palmer at Las Colinas
Debt Instrument [Line Items]
Outstanding borrowings		$ 45,700	45,700
Deferred Finance Costs, net		(387)	(437)
Carrying Value		$ 45,313	45,263
Maturity Date	[2],[3],[4]	Sep. 01, 2026
Annual Interest Rate	[2],[3],[4]	2.26%
Average Monthly Debt Service	[2],[3],[4]	$ 85
Average Monthly Escrow	[2],[3],[4]	$ 156
Mortgage notes payable | The Palmer at Las Colinas | LIBOR
Debt Instrument [Line Items]
Margin over LIBOR	[2],[3],[4]	2.11%
Mortgage notes payable | Windbrooke Crossing
Debt Instrument [Line Items]
Outstanding borrowings		$ 36,657	37,222
Deferred Finance Costs, net		(220)	(272)
Carrying Value		$ 36,437	36,950
Maturity Date	[2],[3],[5]	Jan. 01, 2024
Annual Interest Rate	[2],[3],[5]	2.84%
Average Monthly Debt Service	[2],[3],[5]	$ 154
Average Monthly Escrow	[2],[3],[5]	$ 65
Mortgage notes payable | Windbrooke Crossing | LIBOR
Debt Instrument [Line Items]
Margin over LIBOR	[2],[3],[5]	2.69%
Mortgage notes payable | Woods of Burnsville
Debt Instrument [Line Items]
Outstanding borrowings		$ 37,148	37,744
Deferred Finance Costs, net		(287)	(355)
Carrying Value		$ 36,861	37,389
Maturity Date	[2],[3],[5]	Feb. 01, 2024
Annual Interest Rate	[2],[3],[5]	2.28%
Average Monthly Debt Service	[2],[3],[5]	$ 145
Average Monthly Escrow	[2],[3],[5]	$ 173
Mortgage notes payable | Woods of Burnsville | LIBOR
Debt Instrument [Line Items]
Margin over LIBOR	[2],[3],[5]	2.13%
Mortgage notes payable | Indigo Creek
Debt Instrument [Line Items]
Outstanding borrowings		$ 39,750	40,402
Deferred Finance Costs, net		(262)	(320)
Carrying Value		$ 39,488	40,082
Maturity Date	[2],[3],[5]	May 01, 2024
Annual Interest Rate	[2],[3],[5]	2.08%
Average Monthly Debt Service	[2],[3],[5]	$ 127
Average Monthly Escrow	[2],[3],[5]	$ 74
Mortgage notes payable | Indigo Creek | LIBOR
Debt Instrument [Line Items]
Margin over LIBOR	[2],[3],[5]	1.93%
Mortgage notes payable | Martin's Point
Debt Instrument [Line Items]
Outstanding borrowings		$ 29,467	29,944
Deferred Finance Costs, net		(242)	(289)
Carrying Value		$ 29,225	$ 29,655
Maturity Date	[2],[3],[4]	Nov. 01, 2024
Annual Interest Rate	[2],[3],[4]	2.01%
Average Monthly Debt Service	[2],[3],[4]	$ 111
Average Monthly Escrow	[2],[3],[4]	$ 76
Mortgage notes payable | Martin's Point | LIBOR
Debt Instrument [Line Items]
Margin over LIBOR	[2],[3],[4]	1.86%

[1] Monthly fixed principal plus interest payment required

[2] Variable rate based on one-month LIBOR of 0.1483% (as of September 30, 2020) plus a fixed margin

[3] Variable rate hedged with interest rate cap cash flow hedge

[4] Monthly interest-only payment currently required

[5] Fixed monthly payment of principal and interest payment required

[6] Fixed rate