Real Estate Investments Statistics - Summary of Investment in Multifamily Properties (Details) ft² in Thousands		3 Months Ended
		Mar. 31, 2019 ft² Property $ / Property	Dec. 31, 2018 $ / Property
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		11,664
Number of Units | Property		13,211
Arbors on Forest Ridge
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		155
Number of Units | Property		210
Date Acquired		Jan. 31, 2014
Average Effective Monthly Rent Per Unit | $ / Property	[1]	868	870
% Occupied	[2]	94.80%	95.20%
Cutter's Point
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		198
Number of Units | Property		196
Date Acquired		Jan. 31, 2014
Average Effective Monthly Rent Per Unit | $ / Property	[1]	1,117	1,109
% Occupied	[2]	93.90%	95.40%
Eagle Crest
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		396
Number of Units | Property		447
Date Acquired		Jan. 31, 2014
Average Effective Monthly Rent Per Unit | $ / Property	[1]	932	922
% Occupied	[2]	94.00%	94.90%
Silverbrook
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		526
Number of Units | Property		642
Date Acquired		Jan. 31, 2014
Average Effective Monthly Rent Per Unit | $ / Property	[1]	848	835
% Occupied	[2]	94.90%	94.90%
Edgewater at Sandy Springs
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		727
Number of Units | Property		760
Date Acquired		Jul. 18, 2014
Average Effective Monthly Rent Per Unit | $ / Property	[1]	964	950
% Occupied	[2]	93.20%	94.10%
Beechwood Terrace
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		272
Number of Units | Property		300
Date Acquired		Jul. 21, 2014
Average Effective Monthly Rent Per Unit | $ / Property	[1]	935	933
% Occupied	[2]	93.00%	93.70%
Willow Grove
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		229
Number of Units | Property		244
Date Acquired		Jul. 21, 2014
Average Effective Monthly Rent Per Unit | $ / Property	[1]	981	960
% Occupied	[2]	94.70%	95.10%
Woodbridge
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		247
Number of Units | Property		220
Date Acquired		Jul. 21, 2014
Average Effective Monthly Rent Per Unit | $ / Property	[1]	1,039	1,028
% Occupied	[2]	90.90%	94.10%
Abbington Heights
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		239
Number of Units | Property		274
Date Acquired		Aug. 01, 2014
Average Effective Monthly Rent Per Unit | $ / Property	[1]	878	889
% Occupied	[2]	90.90%	92.00%
The Summit at Sabal Park
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		205
Number of Units | Property		252
Date Acquired		Aug. 20, 2014
Average Effective Monthly Rent Per Unit | $ / Property	[1]	959	955
% Occupied	[2]	93.70%	94.40%
Courtney Cove
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		225
Number of Units | Property		324
Date Acquired		Aug. 20, 2014
Average Effective Monthly Rent Per Unit | $ / Property	[1]	907	895
% Occupied	[2]	93.50%	95.70%
Radbourne Lake
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		247
Number of Units | Property		225
Date Acquired		Sep. 30, 2014
Average Effective Monthly Rent Per Unit | $ / Property	[1]	1,094	1,082
% Occupied	[2]	96.00%	96.00%
Timber Creek
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		248
Number of Units | Property		352
Date Acquired		Sep. 30, 2014
Average Effective Monthly Rent Per Unit | $ / Property	[1]	857	847
% Occupied	[2]	94.60%	92.60%
Belmont at Duck Creek
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		198
Number of Units | Property		240
Date Acquired		Sep. 30, 2014
Average Effective Monthly Rent Per Unit | $ / Property	[1]	1,040	1,030
% Occupied	[2]	95.40%	92.10%
Sabal Palm at Lake Buena Vista
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		371
Number of Units | Property		400
Date Acquired		Nov. 05, 2014
Average Effective Monthly Rent Per Unit | $ / Property	[1]	1,262	1,255
% Occupied	[2]	96.00%	96.50%
Southpoint Reserve at Stoney Creek
Real Estate Properties [Line Items]
Rentable Square Footage | ft²	[3]	116
Number of Units | Property	[3]	156
Date Acquired	[3]	Dec. 18, 2014
Average Effective Monthly Rent Per Unit | $ / Property	[1],[3]	1,107	1,093
% Occupied	[2],[3]	95.50%	98.10%
Cornerstone
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		318
Number of Units | Property		430
Date Acquired		Jan. 15, 2015
Average Effective Monthly Rent Per Unit | $ / Property	[1]	1,029	1,007
% Occupied	[2]	93.00%	94.20%
The Preserve at Terrell Mill
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		692
Number of Units | Property		752
Date Acquired		Feb. 06, 2015
Average Effective Monthly Rent Per Unit | $ / Property	[1]	936	921
% Occupied	[2]	92.20%	94.80%
The Ashlar
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		206
Number of Units | Property		264
Date Acquired		Feb. 26, 2015
Average Effective Monthly Rent Per Unit | $ / Property	[1]	864	859
% Occupied	[2]	89.80%	94.30%
Heatherstone
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		116
Number of Units | Property		152
Date Acquired		Feb. 26, 2015
Average Effective Monthly Rent Per Unit | $ / Property	[1]	862	874
% Occupied	[2]	90.10%	94.70%
Versailles
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		301
Number of Units | Property		388
Date Acquired		Feb. 26, 2015
Average Effective Monthly Rent Per Unit | $ / Property	[1]	892	884
% Occupied	[2]	91.00%	96.40%
Seasons 704 Apartments
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		217
Number of Units | Property		222
Date Acquired		Apr. 15, 2015
Average Effective Monthly Rent Per Unit | $ / Property	[1]	1,130	1,130
% Occupied	[2]	95.50%	96.80%
Madera Point
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		193
Number of Units | Property		256
Date Acquired		Aug. 05, 2015
Average Effective Monthly Rent Per Unit | $ / Property	[1]	880	866
% Occupied	[2]	97.30%	94.50%
The Pointe at the Foothills
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		473
Number of Units | Property		528
Date Acquired		Aug. 05, 2015
Average Effective Monthly Rent Per Unit | $ / Property	[1]	882	859
% Occupied	[2]	95.50%	95.10%
Venue at 8651
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		289
Number of Units | Property		333
Date Acquired		Oct. 30, 2015
Average Effective Monthly Rent Per Unit | $ / Property	[1]	882	875
% Occupied	[2]	93.70%	92.80%
Parc500
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		266
Number of Units | Property		217
Date Acquired		Jul. 27, 2016
Average Effective Monthly Rent Per Unit | $ / Property	[1]	1,265	1,254
% Occupied	[2]	96.30%	94.90%
The Colonnade
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		256
Number of Units | Property		415
Date Acquired		Oct. 11, 2016
Average Effective Monthly Rent Per Unit | $ / Property	[1]	728	719
% Occupied	[2]	91.60%	93.30%
Old Farm
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		697
Number of Units | Property		734
Date Acquired		Dec. 29, 2016
Average Effective Monthly Rent Per Unit | $ / Property	[1]	1,172	1,176
% Occupied	[2]	91.80%	92.90%
Stone Creek at Old Farm
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		186
Number of Units | Property		190
Date Acquired		Dec. 29, 2016
Average Effective Monthly Rent Per Unit | $ / Property	[1]	1,181	1,173
% Occupied	[2]	96.80%	96.80%
Hollister Place
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		246
Number of Units | Property		260
Date Acquired		Feb. 01, 2017
Average Effective Monthly Rent Per Unit | $ / Property	[1]	990	984
% Occupied	[2]	91.20%	93.50%
Rockledge Apartments
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		802
Number of Units | Property		708
Date Acquired		Jun. 30, 2017
Average Effective Monthly Rent Per Unit | $ / Property	[1]	1,205	1,186
% Occupied	[2]	94.60%	94.60%
Atera Apartments
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		334
Number of Units | Property		380
Date Acquired		Oct. 25, 2017
Average Effective Monthly Rent Per Unit | $ / Property	[1]	1,233	1,232
% Occupied	[2]	93.40%	97.40%
Cedar Pointe
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		224
Number of Units | Property		210
Date Acquired		Aug. 24, 2018
Average Effective Monthly Rent Per Unit | $ / Property	[1]	1,050	1,051
% Occupied	[2]	92.90%	95.70%
Crestmont Reserve
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		199
Number of Units | Property		242
Date Acquired		Sep. 26, 2018
Average Effective Monthly Rent Per Unit | $ / Property	[1]	911	914
% Occupied	[2]	90.10%	94.60%
Brandywine I & II
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		414
Number of Units | Property		632
Date Acquired		Sep. 26, 2018
Average Effective Monthly Rent Per Unit | $ / Property	[1]	965	957
% Occupied	[2]	93.00%	93.80%
Bella Vista
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		243
Number of Units | Property		248
Date Acquired		Jan. 28, 2019
Average Effective Monthly Rent Per Unit | $ / Property	[1]	1,218
% Occupied	[2]	94.80%
The Enclave
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		194
Number of Units | Property		204
Date Acquired		Jan. 28, 2019
Average Effective Monthly Rent Per Unit | $ / Property	[1]	1,261
% Occupied	[2]	97.10%
The Heritage
Real Estate Properties [Line Items]
Rentable Square Footage | ft²		199
Number of Units | Property		204
Date Acquired		Jan. 28, 2019
Average Effective Monthly Rent Per Unit | $ / Property	[1]	1,233
% Occupied	[2]	96.60%

[1] Average effective monthly rent per unit is equal to the average of the contractual rent for commenced leases as of March 31, 2019 and December 31, 2018, respectively, minus any tenant concessions over the term of the lease, divided by the number of units under commenced leases as of March 31, 2019 and December 31, 2018, respectively.

[2] Percent occupied is calculated as the number of units occupied as of March 31, 2019 and December 31, 2018, divided by the total number of units, expressed as a percentage.

[3] Property was classified as held for sale as of March 31, 2019.