XML 73 R135.htm IDEA: XBRL DOCUMENT v3.19.3.a.u2
Schedule III - Real Estate and Accumulated Depreciation (Details)
 12 Months Ended
Dec. 31, 2019
USD ($)
ApartmentUnit
Dec. 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Real Estate And Accumulated Depreciation Abstract        
Accumulated Depreciation $ (7,276,786,000) $ (6,696,281,000) $ (6,040,378,000) $ (5,360,389,000)
100 K Apartments (fka 100K Street) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Washington, D.C.      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 222      
Initial Cost to Company, Land $ 15,600,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 69,662,369      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,484      
Gross Amount Carried at close of period 12/31/2019, Land 15,600,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 69,664,853      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 85,264,853      
Accumulated Depreciation (3,157,965)      
Investment in Real Estate, Net 82,106,888      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
140 Riverside Boulevard [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location New York, NY      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 354      
Initial Cost to Company, Land $ 103,539,100      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 94,082,725      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 10,160,746      
Gross Amount Carried at close of period 12/31/2019, Land 103,539,100      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 104,243,471      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 207,782,571      
Accumulated Depreciation (52,510,393)      
Investment in Real Estate, Net 155,272,178      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
160 Riverside Boulevard [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location New York, NY      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 455      
Initial Cost to Company, Land $ 139,933,500      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 190,964,745      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 17,198,947      
Gross Amount Carried at close of period 12/31/2019, Land 139,933,500      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 208,163,692      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 348,097,192      
Accumulated Depreciation (104,423,480)      
Investment in Real Estate, Net 243,673,712      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
170 Amsterdam [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location New York, NY      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 236      
Initial Cost to Company, Land $ 0      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 112,096,955      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 439,194      
Gross Amount Carried at close of period 12/31/2019, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 112,536,149      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 112,536,149      
Accumulated Depreciation (20,556,743)      
Investment in Real Estate, Net 91,979,406      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
175 Kent [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Brooklyn, NY      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 113      
Initial Cost to Company, Land $ 22,037,831      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 53,962,169      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,003,647      
Gross Amount Carried at close of period 12/31/2019, Land 22,037,831      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 55,965,816      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 78,003,647      
Accumulated Depreciation (18,206,594)      
Investment in Real Estate, Net 59,797,053      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
180 Montague (fka Brooklyn Heights) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Brooklyn, NY      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 193      
Initial Cost to Company, Land $ 32,400,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 92,675,228      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,764,589      
Gross Amount Carried at close of period 12/31/2019, Land 32,400,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 97,439,817      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 129,839,817      
Accumulated Depreciation (27,077,371)      
Investment in Real Estate, Net 102,762,446      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
180 Riverside Boulevard [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location New York, NY      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 516      
Initial Cost to Company, Land $ 144,968,250      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 138,346,681      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 14,692,592      
Gross Amount Carried at close of period 12/31/2019, Land 144,968,250      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 153,039,273      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 298,007,523      
Accumulated Depreciation (78,364,843)      
Investment in Real Estate, Net 219,642,680      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
1111 Belle Pre (fka The Madison) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Alexandria, VA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 360      
Initial Cost to Company, Land $ 18,937,702      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 94,758,679      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 399,141      
Gross Amount Carried at close of period 12/31/2019, Land 18,937,702      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 95,157,820      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 114,095,522      
Accumulated Depreciation (25,780,466)      
Investment in Real Estate, Net 88,315,056      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
1210 Mass [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Washington, D.C.      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 144      
Initial Cost to Company, Land $ 9,213,512      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 36,559,189      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,770,003      
Gross Amount Carried at close of period 12/31/2019, Land 9,213,512      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 39,329,192      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 48,542,704      
Accumulated Depreciation (20,032,298)      
Investment in Real Estate, Net 28,510,406      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
1401 Joyce on Pentagon Row [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Arlington, VA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 326      
Initial Cost to Company, Land $ 9,780,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 89,668,165      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 5,482,703      
Gross Amount Carried at close of period 12/31/2019, Land 9,780,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 95,150,868      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 104,930,868      
Accumulated Depreciation (38,110,856)      
Investment in Real Estate, Net 66,820,012      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
1500 Mass Ave [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Washington, D.C.      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 556      
Initial Cost to Company, Land $ 54,638,298      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 40,361,702      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 15,851,496      
Gross Amount Carried at close of period 12/31/2019, Land 54,638,298      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 56,213,198      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 110,851,496      
Accumulated Depreciation (29,241,959)      
Investment in Real Estate, Net 81,609,537      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
1800 Oak (fka Rosslyn) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Arlington, VA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 314      
Initial Cost to Company, Land $ 31,400,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 109,005,734      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 7,759,305      
Gross Amount Carried at close of period 12/31/2019, Land 31,400,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 116,765,039      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 148,165,039      
Accumulated Depreciation (32,605,736)      
Investment in Real Estate, Net 115,559,303      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
2201 Pershing Drive [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Arlington, VA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 188      
Initial Cost to Company, Land $ 11,321,198      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 49,674,175      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,653,163      
Gross Amount Carried at close of period 12/31/2019, Land 11,321,198      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 52,327,338      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 63,648,536      
Accumulated Depreciation (15,332,930)      
Investment in Real Estate, Net 48,315,606      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
2201 Wilson [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Arlington, VA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 219      
Initial Cost to Company, Land $ 21,900,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 78,724,663      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,621,475      
Gross Amount Carried at close of period 12/31/2019, Land 21,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 83,346,138      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 105,246,138      
Accumulated Depreciation (23,254,386)      
Investment in Real Estate, Net 81,991,752      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
2400 M St [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Washington, D.C.      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 359      
Initial Cost to Company, Land $ 30,006,593      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 114,013,785      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,706,151      
Gross Amount Carried at close of period 12/31/2019, Land 30,006,593      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 118,719,936      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 148,726,529      
Accumulated Depreciation (57,645,397)      
Investment in Real Estate, Net 91,081,132      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
315 on A [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Boston, MA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 202      
Initial Cost to Company, Land $ 14,450,070      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 115,824,930      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,261,179      
Gross Amount Carried at close of period 12/31/2019, Land 14,450,070      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 117,086,109      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 131,536,179      
Accumulated Depreciation (22,891,380)      
Investment in Real Estate, Net 108,644,799      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
340 Fremont (fka Rincon Hill) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location San Francisco, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 348      
Initial Cost to Company, Land $ 42,000,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 248,609,655      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 179,247      
Gross Amount Carried at close of period 12/31/2019, Land 42,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 248,788,902      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 290,788,902      
Accumulated Depreciation (33,388,938)      
Investment in Real Estate, Net 257,399,964      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
341 Nevins [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Brooklyn, NY      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 0      
Initial Cost to Company, Land $ 3,621,830      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 189,222      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2019, Land 3,621,830      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 189,222      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 3,811,052      
Accumulated Depreciation 0      
Investment in Real Estate, Net 3,811,052      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
3003 Van Ness (fka Van Ness) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Washington, D.C.      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 625      
Initial Cost to Company, Land $ 56,300,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 141,191,580      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 7,157,154      
Gross Amount Carried at close of period 12/31/2019, Land 56,300,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 148,348,734      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 204,648,734      
Accumulated Depreciation (43,856,738)      
Investment in Real Estate, Net 160,791,996      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
425 Mass [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Washington, D.C.      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 559      
Initial Cost to Company, Land $ 28,150,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 138,600,000      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,759,357      
Gross Amount Carried at close of period 12/31/2019, Land 28,150,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 143,359,357      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 171,509,357      
Accumulated Depreciation (53,491,733)      
Investment in Real Estate, Net 118,017,624      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
455 Eye Street [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Washington, D.C.      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 174      
Initial Cost to Company, Land $ 11,941,407      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 61,418,274      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 40,682      
Gross Amount Carried at close of period 12/31/2019, Land 11,941,407      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 61,458,956      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 73,400,363      
Accumulated Depreciation (6,002,916)      
Investment in Real Estate, Net 67,397,447      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
4701 Willard [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Chevy Chase, MD      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 517      
Initial Cost to Company, Land $ 76,921,130      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 153,947,682      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 31,235,663      
Gross Amount Carried at close of period 12/31/2019, Land 76,921,130      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 185,183,345      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 262,104,475      
Accumulated Depreciation (67,153,478)      
Investment in Real Estate, Net 194,950,997      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
4885 Edgemoor Lane [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Bethesda, MD      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 0      
Initial Cost to Company, Land $ 0      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 10,864,626      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2019, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 10,864,626      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 10,864,626      
Accumulated Depreciation 0      
Investment in Real Estate, Net 10,864,626      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
4th and Hill [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Los Angeles, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 0      
Initial Cost to Company, Land $ 13,131,456      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 16,680,349      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2019, Land 13,131,456      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 16,680,349      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 29,811,805      
Accumulated Depreciation 0      
Investment in Real Estate, Net 29,811,805      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
600 Washington [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location New York, NY      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 135      
Initial Cost to Company, Land $ 32,852,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 43,140,551      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,548,076      
Gross Amount Carried at close of period 12/31/2019, Land 32,852,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 44,688,627      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 77,540,627      
Accumulated Depreciation (22,331,625)      
Investment in Real Estate, Net 55,209,002      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
660 Washington (fka Boston Common) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Boston, MA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 420      
Initial Cost to Company, Land $ 106,100,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 166,311,679      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,730,410      
Gross Amount Carried at close of period 12/31/2019, Land 106,100,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 171,042,089      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 277,142,089      
Accumulated Depreciation (46,949,010)      
Investment in Real Estate, Net 230,193,079      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
70 Greene [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Jersey City, NJ      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 480      
Initial Cost to Company, Land $ 28,108,899      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 236,763,553      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,932,277      
Gross Amount Carried at close of period 12/31/2019, Land 28,108,899      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 239,695,830      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 267,804,729      
Accumulated Depreciation (81,879,133)      
Investment in Real Estate, Net 185,925,596      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
71 Broadway [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location New York, NY      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 238      
Initial Cost to Company, Land $ 22,611,600      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 77,492,171      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 17,054,425      
Gross Amount Carried at close of period 12/31/2019, Land 22,611,600      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 94,546,596      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 117,158,196      
Accumulated Depreciation (51,104,697)      
Investment in Real Estate, Net 66,053,499      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
77 Bluxome [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location San Francisco, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 102      
Initial Cost to Company, Land $ 5,249,124      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 18,609,876      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 479,898      
Gross Amount Carried at close of period 12/31/2019, Land 5,249,124      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 19,089,774      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 24,338,898      
Accumulated Depreciation (6,408,288)      
Investment in Real Estate, Net 17,930,610      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
77 Park Avenue (fka Hoboken) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Hoboken, NJ      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 301      
Initial Cost to Company, Land $ 27,900,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 168,992,440      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 7,688,560      
Gross Amount Carried at close of period 12/31/2019, Land 27,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 176,681,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 204,581,000      
Accumulated Depreciation (47,768,422)      
Investment in Real Estate, Net 156,812,578      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
777 Sixth [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location New York, NY      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 294      
Initial Cost to Company, Land $ 65,352,706      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 65,747,294      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,999,856      
Gross Amount Carried at close of period 12/31/2019, Land 65,352,706      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 70,747,150      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 136,099,856      
Accumulated Depreciation (30,672,075)      
Investment in Real Estate, Net 105,427,781      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
88 Hillside [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Daly City, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 95      
Initial Cost to Company, Land $ 7,786,800      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 31,587,325      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,225,899      
Gross Amount Carried at close of period 12/31/2019, Land 7,786,800      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 34,813,224      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 42,600,024      
Accumulated Depreciation (11,434,181)      
Investment in Real Estate, Net 31,165,843      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
855 Brannan [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location San Francisco, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 449      
Initial Cost to Company, Land $ 41,363,921      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 282,107,685      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 62,476      
Gross Amount Carried at close of period 12/31/2019, Land 41,363,921      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 282,170,161      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 323,534,082      
Accumulated Depreciation (23,429,467)      
Investment in Real Estate, Net 300,104,615      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
929 Mass (fka 929 House) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Cambridge, MA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 127      
Initial Cost to Company, Land $ 3,252,993      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 21,745,595      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 7,695,575      
Gross Amount Carried at close of period 12/31/2019, Land 3,252,993      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 29,441,170      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 32,694,163      
Accumulated Depreciation (19,893,418)      
Investment in Real Estate, Net 12,800,745      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Academy Village [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location North Hollywood, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 248      
Initial Cost to Company, Land $ 25,000,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 23,593,194      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 9,821,339      
Gross Amount Carried at close of period 12/31/2019, Land 25,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 33,414,533      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 58,414,533      
Accumulated Depreciation (20,345,297)      
Investment in Real Estate, Net 38,069,236      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Acappella [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Pasadena, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 143      
Initial Cost to Company, Land $ 5,839,548      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 29,360,452      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,301,628      
Gross Amount Carried at close of period 12/31/2019, Land 5,839,548      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 31,662,080      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 37,501,628      
Accumulated Depreciation (12,293,107)      
Investment in Real Estate, Net 25,208,521      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Acton Courtyard [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Berkeley, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 71      
Initial Cost to Company, Land $ 5,550,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 15,785,509      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 396,492      
Gross Amount Carried at close of period 12/31/2019, Land 5,550,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 16,182,001      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 21,732,001      
Accumulated Depreciation (7,612,133)      
Investment in Real Estate, Net 14,119,868      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Alban Towers [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Washington, D.C.      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 229      
Initial Cost to Company, Land $ 18,900,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 89,794,201      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 6,474,195      
Gross Amount Carried at close of period 12/31/2019, Land 18,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 96,268,396      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 115,168,396      
Accumulated Depreciation (25,786,581)      
Investment in Real Estate, Net 89,381,815      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Alborada [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Fremont, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 442      
Initial Cost to Company, Land $ 24,310,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 59,214,129      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 9,528,299      
Gross Amount Carried at close of period 12/31/2019, Land 24,310,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 68,742,428      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 93,052,428      
Accumulated Depreciation (44,468,172)      
Investment in Real Estate, Net 48,584,256      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Alcott Apartments (fka West End Tower) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Boston, MA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 0      
Initial Cost to Company, Land $ 10,424,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 128,885,729      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2019, Land 10,424,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 128,885,729      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 139,309,729      
Accumulated Depreciation 0      
Investment in Real Estate, Net 139,309,729      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Altitude (fka Village at Howard Hughes, The (Lots 1 & 2)) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Los Angeles, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 545      
Initial Cost to Company, Land $ 43,783,485      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 150,235,905      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 493,024      
Gross Amount Carried at close of period 12/31/2019, Land 43,783,485      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 150,728,929      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 194,512,414      
Accumulated Depreciation (20,615,169)      
Investment in Real Estate, Net 173,897,245      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Alton, The (fka Millikan) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Irvine, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 344      
Initial Cost to Company, Land $ 11,049,027      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 96,526,323      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 150,438      
Gross Amount Carried at close of period 12/31/2019, Land 11,049,027      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 96,676,761      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 107,725,788      
Accumulated Depreciation (11,346,591)      
Investment in Real Estate, Net 96,379,197      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Arbor Terrace [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Sunnyvale, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 175      
Initial Cost to Company, Land $ 9,057,300      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 18,483,642      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 11,357,865      
Gross Amount Carried at close of period 12/31/2019, Land 9,057,300      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 29,841,507      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 38,898,807      
Accumulated Depreciation (17,937,496)      
Investment in Real Estate, Net 20,961,311      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Arches,The [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Sunnyvale, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 410      
Initial Cost to Company, Land $ 26,650,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 62,850,000      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,623,168      
Gross Amount Carried at close of period 12/31/2019, Land 26,650,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 65,473,168      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 92,123,168      
Accumulated Depreciation (24,870,049)      
Investment in Real Estate, Net 67,253,119      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Artisan on Second [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Los Angeles, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 118      
Initial Cost to Company, Land $ 8,000,400      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 36,074,600      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,173,462      
Gross Amount Carried at close of period 12/31/2019, Land 8,000,400      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 37,248,062      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 45,248,462      
Accumulated Depreciation (12,924,017)      
Investment in Real Estate, Net 32,324,445      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Artisan Square [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Northridge, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 140      
Initial Cost to Company, Land $ 7,000,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 20,537,359      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,889,100      
Gross Amount Carried at close of period 12/31/2019, Land 7,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 22,426,459      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 29,426,459      
Accumulated Depreciation (13,116,756)      
Investment in Real Estate, Net 16,309,703      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Artistry Emeryville (fka Emeryville) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Emeryville, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 267      
Initial Cost to Company, Land $ 12,300,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 61,466,267      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 7,189,056      
Gross Amount Carried at close of period 12/31/2019, Land 12,300,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 68,655,323      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 80,955,323      
Accumulated Depreciation (20,908,096)      
Investment in Real Estate, Net 60,047,227      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Atelier [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Brooklyn, NY      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 120      
Initial Cost to Company, Land $ 32,401,680      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 47,135,432      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 432,778      
Gross Amount Carried at close of period 12/31/2019, Land 32,401,680      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 47,568,210      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 79,969,890      
Accumulated Depreciation (8,426,826)      
Investment in Real Estate, Net 71,543,064      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Avenue Two [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Redwood City, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 123      
Initial Cost to Company, Land $ 7,995,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 18,005,000      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,417,128      
Gross Amount Carried at close of period 12/31/2019, Land 7,995,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 20,422,128      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 28,417,128      
Accumulated Depreciation (7,587,499)      
Investment in Real Estate, Net 20,829,629      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Axis at Shady Grove [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Rockville, MD      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 366      
Initial Cost to Company, Land $ 14,745,774      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 90,503,831      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 123,658      
Gross Amount Carried at close of period 12/31/2019, Land 14,745,774      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 90,627,489      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 105,373,263      
Accumulated Depreciation (6,627,790)      
Investment in Real Estate, Net 98,745,473      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Azure (fka Mission Bay-Block 13) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location San Francisco, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 273      
Initial Cost to Company, Land $ 32,855,115      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 153,569,655      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 385,653      
Gross Amount Carried at close of period 12/31/2019, Land 32,855,115      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 153,955,308      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 186,810,423      
Accumulated Depreciation (25,110,173)      
Investment in Real Estate, Net 161,700,250      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Bay Hill [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Long Beach, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 160      
Initial Cost to Company, Land $ 7,600,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 27,437,239      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,648,128      
Gross Amount Carried at close of period 12/31/2019, Land 7,600,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 31,085,367      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 38,685,367      
Accumulated Depreciation (16,705,166)      
Investment in Real Estate, Net 21,980,201      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Beatrice, The [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location New York, NY      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 302      
Initial Cost to Company, Land $ 114,351,405      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 165,648,595      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,852,511      
Gross Amount Carried at close of period 12/31/2019, Land 114,351,405      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 167,501,106      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 281,852,511      
Accumulated Depreciation (51,586,536)      
Investment in Real Estate, Net 230,265,975      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Bella Vista I, II, III Combined [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Woodland Hills, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 579      
Initial Cost to Company, Land $ 31,682,754      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 121,095,786      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 10,564,320      
Gross Amount Carried at close of period 12/31/2019, Land 31,682,754      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 131,660,106      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 163,342,860      
Accumulated Depreciation (63,397,900)      
Investment in Real Estate, Net 99,944,960      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Belle Arts Condominium Homes, LLC [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Bellevue, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 1      
Initial Cost to Company, Land $ 63,158      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 236,157      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,098      
Gross Amount Carried at close of period 12/31/2019, Land 63,158      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 238,255      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 301,413      
Accumulated Depreciation (91,640)      
Investment in Real Estate, Net 209,773      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Bella Fontaine [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Marina Del Rey, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 102      
Initial Cost to Company, Land $ 9,098,808      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 28,701,192      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,077,210      
Gross Amount Carried at close of period 12/31/2019, Land 9,098,808      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 30,778,402      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 39,877,210      
Accumulated Depreciation (9,929,838)      
Investment in Real Estate, Net 29,947,372      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Breakwater at Marina Del Rey [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Marina Del Rey, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 224      
Initial Cost to Company, Land $ 0      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 73,189,262      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,301,977      
Gross Amount Carried at close of period 12/31/2019, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 75,491,239      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 75,491,239      
Accumulated Depreciation (22,556,033)      
Investment in Real Estate, Net 52,935,206      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Briarwood (CA) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Sunnyvale, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 192      
Initial Cost to Company, Land $ 9,991,500      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 22,247,278      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,223,652      
Gross Amount Carried at close of period 12/31/2019, Land 9,991,500      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 26,470,930      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 36,462,430      
Accumulated Depreciation (19,003,418)      
Investment in Real Estate, Net 17,459,012      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Brodie, The [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Westminster, CO      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 312      
Initial Cost to Company, Land $ 8,639,904      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 79,254,009      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 338,241      
Gross Amount Carried at close of period 12/31/2019, Land 8,639,904      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 79,592,250      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 88,232,154      
Accumulated Depreciation (4,390,121)      
Investment in Real Estate, Net 83,842,033      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Brooklyner (fka 111 Lawrence) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Brooklyn, NY      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 490      
Initial Cost to Company, Land $ 40,099,922      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 221,438,631      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,272,230      
Gross Amount Carried at close of period 12/31/2019, Land 40,099,922      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 225,710,861      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 265,810,783      
Accumulated Depreciation (69,755,616)      
Investment in Real Estate, Net 196,055,167      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
C on Pico [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Los Angeles, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 94      
Initial Cost to Company, Land $ 17,125,766      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 28,074,234      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 468,094      
Gross Amount Carried at close of period 12/31/2019, Land 17,125,766      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 28,542,328      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 45,668,094      
Accumulated Depreciation (4,917,365)      
Investment in Real Estate, Net 40,750,729      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Carlyle Mill [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Alexandria, VA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 317      
Initial Cost to Company, Land $ 10,000,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 51,367,913      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 9,043,657      
Gross Amount Carried at close of period 12/31/2019, Land 10,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 60,411,570      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 70,411,570      
Accumulated Depreciation (34,997,308)      
Investment in Real Estate, Net 35,414,262      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Carmel Terrace [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location San Diego, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 384      
Initial Cost to Company, Land $ 2,288,300      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 20,596,281      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 12,519,325      
Gross Amount Carried at close of period 12/31/2019, Land 2,288,300      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 33,115,606      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 35,403,906      
Accumulated Depreciation (28,576,803)      
Investment in Real Estate, Net 6,827,103      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Cascade [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Seattle, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 477      
Initial Cost to Company, Land $ 23,751,564      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 149,388,658      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 10,060      
Gross Amount Carried at close of period 12/31/2019, Land 23,751,564      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 149,398,718      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 173,150,282      
Accumulated Depreciation (14,329,011)      
Investment in Real Estate, Net 158,821,271      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Centennial (fka Centennial Court & Centennial Tower) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Seattle, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 408      
Initial Cost to Company, Land $ 9,700,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 70,080,378      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 13,065,205      
Gross Amount Carried at close of period 12/31/2019, Land 9,700,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 83,145,583      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 92,845,583      
Accumulated Depreciation (43,852,523)      
Investment in Real Estate, Net 48,993,060      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Centre Club Combined [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Ontario, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 412      
Initial Cost to Company, Land $ 7,436,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 33,014,789      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 9,490,814      
Gross Amount Carried at close of period 12/31/2019, Land 7,436,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 42,505,603      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 49,941,603      
Accumulated Depreciation (26,716,928)      
Investment in Real Estate, Net 23,224,675      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Chloe on Madison (fka 1401 E. Madison) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Seattle, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 137      
Initial Cost to Company, Land $ 10,401,958      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 52,593,395      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2019, Land 10,401,958      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 52,593,395      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 62,995,353      
Accumulated Depreciation (497,660)      
Investment in Real Estate, Net 62,497,693      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Chloe on Union (fka Chloe) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Seattle, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 117      
Initial Cost to Company, Land $ 14,835,571      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 39,359,650      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,516,557      
Gross Amount Carried at close of period 12/31/2019, Land 14,835,571      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 41,876,207      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 56,711,778      
Accumulated Depreciation (4,541,342)      
Investment in Real Estate, Net 52,170,436      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Church Corner [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Cambridge, MA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 85      
Initial Cost to Company, Land $ 5,220,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 16,744,643      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,270,549      
Gross Amount Carried at close of period 12/31/2019, Land 5,220,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 20,015,192      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 25,235,192      
Accumulated Depreciation (10,988,447)      
Investment in Real Estate, Net 14,246,745      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
City Gate at Cupertino (fka Cupertino) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Cupertino, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 311      
Initial Cost to Company, Land $ 40,400,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 95,937,046      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 7,548,015      
Gross Amount Carried at close of period 12/31/2019, Land 40,400,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 103,485,061      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 143,885,061      
Accumulated Depreciation (29,361,079)      
Investment in Real Estate, Net 114,523,982      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
City Pointe [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Fullerton, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 183      
Initial Cost to Company, Land $ 6,863,792      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 36,476,208      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,588,233      
Gross Amount Carried at close of period 12/31/2019, Land 6,863,792      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 40,064,441      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 46,928,233      
Accumulated Depreciation (15,519,206)      
Investment in Real Estate, Net 31,409,027      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
City Square Bellevue (fka Bellevue) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Bellevue, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 191      
Initial Cost to Company, Land $ 15,100,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 41,876,257      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,873,050      
Gross Amount Carried at close of period 12/31/2019, Land 15,100,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 45,749,307      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 60,849,307      
Accumulated Depreciation (13,419,667)      
Investment in Real Estate, Net 47,429,640      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Clarendon, The [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Arlington, VA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 292      
Initial Cost to Company, Land $ 30,400,340      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 103,824,660      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,674,009      
Gross Amount Carried at close of period 12/31/2019, Land 30,400,340      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 106,498,669      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 136,899,009      
Accumulated Depreciation (36,985,746)      
Investment in Real Estate, Net 99,913,263      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Cleo, The [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Los Angeles, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 92      
Initial Cost to Company, Land $ 6,615,467      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 14,829,335      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,079,934      
Gross Amount Carried at close of period 12/31/2019, Land 6,615,467      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 18,909,269      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 25,524,736      
Accumulated Depreciation (9,776,697)      
Investment in Real Estate, Net 15,748,039      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Connecticut Heights [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Washington, D.C.      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 518      
Initial Cost to Company, Land $ 27,600,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 114,002,295      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 10,060,643      
Gross Amount Carried at close of period 12/31/2019, Land 27,600,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 124,062,938      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 151,662,938      
Accumulated Depreciation (33,971,504)      
Investment in Real Estate, Net 117,691,434      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Corcoran House at DuPont Circle (fka DuPont Circle) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Washington, D.C.      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 138      
Initial Cost to Company, Land $ 13,500,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 26,913,113      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,637,933      
Gross Amount Carried at close of period 12/31/2019, Land 13,500,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 29,551,046      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 43,051,046      
Accumulated Depreciation (9,012,285)      
Investment in Real Estate, Net 34,038,761      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Courthouse Plaza [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Arlington, VA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 396      
Initial Cost to Company, Land $ 0      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 87,386,024      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 6,316,702      
Gross Amount Carried at close of period 12/31/2019, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 93,702,726      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 93,702,726      
Accumulated Depreciation (28,408,921)      
Investment in Real Estate, Net 65,293,805      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Creekside (San Mateo) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location San Mateo, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 192      
Initial Cost to Company, Land $ 9,606,600      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 21,193,232      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,951,801      
Gross Amount Carried at close of period 12/31/2019, Land 9,606,600      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 26,145,033      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 35,751,633      
Accumulated Depreciation (18,907,735)      
Investment in Real Estate, Net 16,843,898      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Cronins Landing [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Waltham, MA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 281      
Initial Cost to Company, Land $ 32,300,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 85,119,324      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 11,972,290      
Gross Amount Carried at close of period 12/31/2019, Land 32,300,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 97,091,614      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 129,391,614      
Accumulated Depreciation (27,201,943)      
Investment in Real Estate, Net 102,189,671      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Crystal Place [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Arlington, VA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 181      
Initial Cost to Company, Land $ 17,200,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 47,918,975      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,946,812      
Gross Amount Carried at close of period 12/31/2019, Land 17,200,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 51,865,787      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 69,065,787      
Accumulated Depreciation (15,614,718)      
Investment in Real Estate, Net 53,451,069      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Dalton, The [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Alexandria, VA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 270      
Initial Cost to Company, Land $ 22,947,777      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 95,292,515      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures (6)      
Gross Amount Carried at close of period 12/31/2019, Land 22,947,777      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 95,292,509      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 118,240,286      
Accumulated Depreciation 0      
Investment in Real Estate, Net 118,240,286      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Deerwood (SD)        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location San Diego, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 316      
Initial Cost to Company, Land $ 2,082,095      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 18,739,815      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 15,675,022      
Gross Amount Carried at close of period 12/31/2019, Land 2,082,095      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 34,414,837      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 36,496,932      
Accumulated Depreciation (30,453,714)      
Investment in Real Estate, Net 6,043,218      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Del Mar Ridge [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location San Diego, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 181      
Initial Cost to Company, Land $ 7,801,824      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 36,948,176      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,246,225      
Gross Amount Carried at close of period 12/31/2019, Land 7,801,824      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 41,194,401      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 48,996,225      
Accumulated Depreciation (17,680,819)      
Investment in Real Estate, Net 31,315,406      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Eagle Canyon [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Chino Hills, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 252      
Initial Cost to Company, Land $ 1,808,900      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 16,274,361      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 10,865,978      
Gross Amount Carried at close of period 12/31/2019, Land 1,808,900      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 27,140,339      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 28,949,239      
Accumulated Depreciation (20,747,510)      
Investment in Real Estate, Net 8,201,729      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Edgemont at Bethesda Metro [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Bethesda, MD      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 122      
Initial Cost to Company, Land $ 13,092,552      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 43,907,448      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,674,370      
Gross Amount Carried at close of period 12/31/2019, Land 13,092,552      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 45,581,818      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 58,674,370      
Accumulated Depreciation (15,155,907)      
Investment in Real Estate, Net 43,518,463      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Emerson Place [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Boston, MA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 444      
Initial Cost to Company, Land $ 14,855,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 57,566,636      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 35,014,249      
Gross Amount Carried at close of period 12/31/2019, Land 14,855,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 92,580,885      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 107,435,885      
Accumulated Depreciation (63,325,270)      
Investment in Real Estate, Net 44,110,615      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Encore at Sherman Oaks, The [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Sherman Oaks, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 174      
Initial Cost to Company, Land $ 8,700,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 25,446,003      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,847,449      
Gross Amount Carried at close of period 12/31/2019, Land 8,700,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 29,293,452      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 37,993,452      
Accumulated Depreciation (10,801,336)      
Investment in Real Estate, Net 27,192,116      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Eviva on Cherokee [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Denver, CO      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 274      
Initial Cost to Company, Land $ 10,507,626      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 100,037,204      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 151,235      
Gross Amount Carried at close of period 12/31/2019, Land 10,507,626      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 100,188,439      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 110,696,065      
Accumulated Depreciation (6,553,585)      
Investment in Real Estate, Net 104,142,480      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Fountains at Emerald Park (fka Emerald Park) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Dublin, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 324      
Initial Cost to Company, Land $ 25,900,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 83,986,217      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,935,049      
Gross Amount Carried at close of period 12/31/2019, Land 25,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 87,921,266      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 113,821,266      
Accumulated Depreciation (25,270,333)      
Investment in Real Estate, Net 88,550,933      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Fremont Center [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Fremont, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 322      
Initial Cost to Company, Land $ 25,800,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 78,753,114      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,490,634      
Gross Amount Carried at close of period 12/31/2019, Land 25,800,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 83,243,748      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 109,043,748      
Accumulated Depreciation (24,471,382)      
Investment in Real Estate, Net 84,572,366      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Gaithersburg Station [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Gaithersburg, MD      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 400      
Initial Cost to Company, Land $ 17,500,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 74,678,917      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,537,268      
Gross Amount Carried at close of period 12/31/2019, Land 17,500,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 78,216,185      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 95,716,185      
Accumulated Depreciation (20,628,153)      
Investment in Real Estate, Net 75,088,032      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Gallery, The [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Hermosa Beach, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 169      
Initial Cost to Company, Land $ 18,144,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 46,567,941      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,995,980      
Gross Amount Carried at close of period 12/31/2019, Land 18,144,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 49,563,921      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 67,707,921      
Accumulated Depreciation (24,741,834)      
Investment in Real Estate, Net 42,966,087      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Gateway at Malden Center [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Malden, MA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 203      
Initial Cost to Company, Land $ 9,209,780      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 25,722,666      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 16,463,954      
Gross Amount Carried at close of period 12/31/2019, Land 9,209,780      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 42,186,620      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 51,396,400      
Accumulated Depreciation (26,861,288)      
Investment in Real Estate, Net 24,535,112      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Geary Court Yard [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location San Francisco, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 165      
Initial Cost to Company, Land $ 1,722,400      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 15,471,429      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 6,197,853      
Gross Amount Carried at close of period 12/31/2019, Land 1,722,400      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 21,669,282      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 23,391,682      
Accumulated Depreciation (15,406,560)      
Investment in Real Estate, Net 7,985,122      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Girard [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Boston, MA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 160      
Initial Cost to Company, Land $ 0      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 102,450,328      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 865,330      
Gross Amount Carried at close of period 12/31/2019, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 103,315,658      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 103,315,658      
Accumulated Depreciation (11,248,402)      
Investment in Real Estate, Net 92,067,256      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Hampshire Place [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Los Angeles, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 259      
Initial Cost to Company, Land $ 10,806,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 30,335,330      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 8,125,571      
Gross Amount Carried at close of period 12/31/2019, Land 10,806,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 38,460,901      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 49,266,901      
Accumulated Depreciation (19,841,849)      
Investment in Real Estate, Net 29,425,052      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Harbor Steps [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Seattle, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 761      
Initial Cost to Company, Land $ 59,403,601      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 158,829,432      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 40,880,428      
Gross Amount Carried at close of period 12/31/2019, Land 59,403,601      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 199,709,860      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 259,113,461      
Accumulated Depreciation (97,046,373)      
Investment in Real Estate, Net 162,067,088      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Hathaway [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Long Beach, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 385      
Initial Cost to Company, Land $ 2,512,500      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 22,611,912      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 13,674,471      
Gross Amount Carried at close of period 12/31/2019, Land 2,512,500      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 36,286,383      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 38,798,883      
Accumulated Depreciation (27,001,675)      
Investment in Real Estate, Net 11,797,208      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Helios (fka 2nd+Pine) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Seattle, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 398      
Initial Cost to Company, Land $ 18,061,674      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 206,628,093      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 110,524      
Gross Amount Carried at close of period 12/31/2019, Land 18,061,674      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 206,738,617      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 224,800,291      
Accumulated Depreciation (20,125,380)      
Investment in Real Estate, Net 204,674,911      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Heritage at Stone Ridge [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Burlington, MA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 180      
Initial Cost to Company, Land $ 10,800,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 31,808,335      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,849,652      
Gross Amount Carried at close of period 12/31/2019, Land 10,800,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 34,657,987      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 45,457,987      
Accumulated Depreciation (17,798,543)      
Investment in Real Estate, Net 27,659,444      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Heritage Ridge [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Lynwood, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 197      
Initial Cost to Company, Land $ 6,895,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 18,983,597      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,605,503      
Gross Amount Carried at close of period 12/31/2019, Land 6,895,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 23,589,100      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 30,484,100      
Accumulated Depreciation (11,968,336)      
Investment in Real Estate, Net 18,515,764      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Hesby [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location North Hollywood, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 308      
Initial Cost to Company, Land $ 23,299,892      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 102,700,108      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,653,931      
Gross Amount Carried at close of period 12/31/2019, Land 23,299,892      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 104,354,039      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 127,653,931      
Accumulated Depreciation (25,277,554)      
Investment in Real Estate, Net 102,376,377      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Highlands at South Plainfield [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location South Plainfield, NJ      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 252      
Initial Cost to Company, Land $ 10,080,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 37,526,912      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,592,223      
Gross Amount Carried at close of period 12/31/2019, Land 10,080,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 40,119,135      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 50,199,135      
Accumulated Depreciation (20,191,766)      
Investment in Real Estate, Net 30,007,369      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Hikari [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Los Angeles, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 128      
Initial Cost to Company, Land $ 9,435,760      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 32,564,240      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 965,477      
Gross Amount Carried at close of period 12/31/2019, Land 9,435,760      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 33,529,717      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 42,965,477      
Accumulated Depreciation (11,609,215)      
Investment in Real Estate, Net 31,356,262      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Hudson Crossing [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location New York, NY      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 259      
Initial Cost to Company, Land $ 23,420,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 69,977,699      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,000,297      
Gross Amount Carried at close of period 12/31/2019, Land 23,420,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 72,977,996      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 96,397,996      
Accumulated Depreciation (38,482,671)      
Investment in Real Estate, Net 57,915,325      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Hudson Pointe [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Jersey City, NJ      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 182      
Initial Cost to Company, Land $ 5,350,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 41,114,074      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 6,902,664      
Gross Amount Carried at close of period 12/31/2019, Land 5,350,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 48,016,738      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 53,366,738      
Accumulated Depreciation (26,064,218)      
Investment in Real Estate, Net 27,302,520      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Hunt Club II [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Charlotte, NC      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 0      
Initial Cost to Company, Land $ 100,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 0      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2019, Land 100,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 100,000      
Accumulated Depreciation 0      
Investment in Real Estate, Net 100,000      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Huxley, The [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Redwood City, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 137      
Initial Cost to Company, Land $ 18,775,028      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 89,335,476      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 5,577      
Gross Amount Carried at close of period 12/31/2019, Land 18,775,028      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 89,341,053      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 108,116,081      
Accumulated Depreciation (2,362,663)      
Investment in Real Estate, Net 105,753,418      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Ivory Wood [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Bothell, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 144      
Initial Cost to Company, Land $ 2,732,800      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 13,888,282      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,716,006      
Gross Amount Carried at close of period 12/31/2019, Land 2,732,800      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 15,604,288      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 18,337,088      
Accumulated Depreciation (8,531,839)      
Investment in Real Estate, Net 9,805,249      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Jia [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Los Angeles, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 280      
Initial Cost to Company, Land $ 14,791,831      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 77,752,457      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 816,097      
Gross Amount Carried at close of period 12/31/2019, Land 14,791,831      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 78,568,554      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 93,360,385      
Accumulated Depreciation (22,410,277)      
Investment in Real Estate, Net 70,950,108      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Junction 47 (fka West Seattle) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Seattle, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 206      
Initial Cost to Company, Land $ 11,726,305      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 56,576,329      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 139,678      
Gross Amount Carried at close of period 12/31/2019, Land 11,726,305      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 56,716,007      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 68,442,312      
Accumulated Depreciation (9,832,830)      
Investment in Real Estate, Net 58,609,482      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Kelvin, The (fka Modera) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Irvine, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 194      
Initial Cost to Company, Land $ 15,521,552      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 64,853,448      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 593,826      
Gross Amount Carried at close of period 12/31/2019, Land 15,521,552      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 65,447,274      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 80,968,826      
Accumulated Depreciation (12,644,037)      
Investment in Real Estate, Net 68,324,789      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Kenwood Mews [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Burbank, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 141      
Initial Cost to Company, Land $ 14,100,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 24,662,883      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,164,875      
Gross Amount Carried at close of period 12/31/2019, Land 14,100,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 28,827,758      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 42,927,758      
Accumulated Depreciation (14,951,144)      
Investment in Real Estate, Net 27,976,614      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Laguna Clara [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Santa Clara, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 264      
Initial Cost to Company, Land $ 13,642,420      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 29,597,400      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 5,500,048      
Gross Amount Carried at close of period 12/31/2019, Land 13,642,420      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 35,097,448      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 48,739,868      
Accumulated Depreciation (19,856,605)      
Investment in Real Estate, Net 28,883,263      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Landings at Port Imperial [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location W. New York, NJ      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 276      
Initial Cost to Company, Land $ 27,246,045      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 37,741,050      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 14,471,631      
Gross Amount Carried at close of period 12/31/2019, Land 27,246,045      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 52,212,681      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 79,458,726      
Accumulated Depreciation (33,207,884)      
Investment in Real Estate, Net 46,250,842      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Lane [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Seattle, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 217      
Initial Cost to Company, Land $ 13,142,946      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 71,853,083      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures (1)      
Gross Amount Carried at close of period 12/31/2019, Land 13,142,946      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 71,853,082      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 84,996,028      
Accumulated Depreciation 0      
Investment in Real Estate, Net 84,996,028      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Lex, The [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location San Jose, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 387      
Initial Cost to Company, Land $ 21,817,512      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 158,778,598      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 77,511      
Gross Amount Carried at close of period 12/31/2019, Land 21,817,512      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 158,856,109      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 180,673,621      
Accumulated Depreciation (8,972,354)      
Investment in Real Estate, Net 171,701,267      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Liberty Park [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Braintree, MA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 202      
Initial Cost to Company, Land $ 5,977,504      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 26,749,111      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 6,951,551      
Gross Amount Carried at close of period 12/31/2019, Land 5,977,504      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 33,700,662      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 39,678,166      
Accumulated Depreciation (19,975,624)      
Investment in Real Estate, Net 19,702,542      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Liberty Tower [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Arlington, VA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 235      
Initial Cost to Company, Land $ 16,382,822      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 83,817,078      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,551,120      
Gross Amount Carried at close of period 12/31/2019, Land 16,382,822      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 86,368,198      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 102,751,020      
Accumulated Depreciation (31,785,187)      
Investment in Real Estate, Net 70,965,833      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Lincoln Heights [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Quincy, MA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 336      
Initial Cost to Company, Land $ 5,928,400      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 33,595,262      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 15,019,958      
Gross Amount Carried at close of period 12/31/2019, Land 5,928,400      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 48,615,220      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 54,543,620      
Accumulated Depreciation (37,746,289)      
Investment in Real Estate, Net 16,797,331      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Lindley Apartments [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Encino, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 129      
Initial Cost to Company, Land $ 5,805,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 25,705,000      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,055,111      
Gross Amount Carried at close of period 12/31/2019, Land 5,805,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 27,760,111      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 33,565,111      
Accumulated Depreciation (10,259,804)      
Investment in Real Estate, Net 23,305,307      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Lofts at Kendall Square (fka Kendall Square) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Cambridge, MA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 186      
Initial Cost to Company, Land $ 18,696,674      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 78,445,657      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 6,941,386      
Gross Amount Carried at close of period 12/31/2019, Land 18,696,674      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 85,387,043      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 104,083,717      
Accumulated Depreciation (24,300,285)      
Investment in Real Estate, Net 79,783,432      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Lofts at Kendall Square ll (fka 249 Third Street) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Cambridge, MA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 84      
Initial Cost to Company, Land $ 4,603,326      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 42,655,411      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2019, Land 4,603,326      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 42,655,411      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 47,258,737      
Accumulated Depreciation (388,231)      
Investment in Real Estate, Net 46,870,506      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Longacre House [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location New York, NY      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 293      
Initial Cost to Company, Land $ 73,170,045      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 53,962,510      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,562,899      
Gross Amount Carried at close of period 12/31/2019, Land 73,170,045      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 58,525,409      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 131,695,454      
Accumulated Depreciation (26,269,075)      
Investment in Real Estate, Net 105,426,379      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Longfellow Place [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Boston, MA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 710      
Initial Cost to Company, Land $ 38,264,917      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 132,175,915      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 86,857,633      
Gross Amount Carried at close of period 12/31/2019, Land 38,264,917      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 219,033,548      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 257,298,465      
Accumulated Depreciation (153,930,179)      
Investment in Real Estate, Net 103,368,286      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Madox [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Jersey City, NJ      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 131      
Initial Cost to Company, Land $ 9,679,635      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 64,594,205      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 456,215      
Gross Amount Carried at close of period 12/31/2019, Land 9,679,635      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 65,050,420      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 74,730,055      
Accumulated Depreciation (4,991,342)      
Investment in Real Estate, Net 69,738,713      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Mantena [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location New York, NY      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 98      
Initial Cost to Company, Land $ 22,346,513      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 61,501,158      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,159,451      
Gross Amount Carried at close of period 12/31/2019, Land 22,346,513      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 62,660,609      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 85,007,122      
Accumulated Depreciation (18,028,047)      
Investment in Real Estate, Net 66,979,075      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Marina 41 (fka Marina Del Rey) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Marina Del Rey, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 623      
Initial Cost to Company, Land $ 0      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 168,842,442      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 9,214,698      
Gross Amount Carried at close of period 12/31/2019, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 178,057,140      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 178,057,140      
Accumulated Depreciation (53,401,243)      
Investment in Real Estate, Net 124,655,897      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Mariposa at Playa Del Rey (fka Playa Del Rey) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Playa Del Rey, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 354      
Initial Cost to Company, Land $ 60,900,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 89,311,482      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 6,259,009      
Gross Amount Carried at close of period 12/31/2019, Land 60,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 95,570,491      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 156,470,491      
Accumulated Depreciation (28,260,197)      
Investment in Real Estate, Net 128,210,294      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Mark on 8th [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Seattle, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 174      
Initial Cost to Company, Land $ 23,004,387      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 51,148,861      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 132,254      
Gross Amount Carried at close of period 12/31/2019, Land 23,004,387      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 51,281,115      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 74,285,502      
Accumulated Depreciation (4,399,467)      
Investment in Real Estate, Net 69,886,035      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Market Street Village [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location San Diego, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 229      
Initial Cost to Company, Land $ 13,740,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 40,757,301      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,433,811      
Gross Amount Carried at close of period 12/31/2019, Land 13,740,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 43,191,112      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 56,931,112      
Accumulated Depreciation (21,071,334)      
Investment in Real Estate, Net 35,859,778      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Milano Lofts [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Los Angeles, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 99      
Initial Cost to Company, Land $ 8,125,216      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 27,378,784      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,128,987      
Gross Amount Carried at close of period 12/31/2019, Land 8,125,216      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 31,507,771      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 39,632,987      
Accumulated Depreciation (9,253,714)      
Investment in Real Estate, Net 30,379,273      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Mill Creek [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Milpitas, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 516      
Initial Cost to Company, Land $ 12,858,693      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 57,168,503      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 17,604,121      
Gross Amount Carried at close of period 12/31/2019, Land 12,858,693      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 74,772,624      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 87,631,317      
Accumulated Depreciation (39,853,420)      
Investment in Real Estate, Net 47,777,897      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Montierra (CA) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location San Diego, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 272      
Initial Cost to Company, Land $ 8,160,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 29,360,938      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 8,510,123      
Gross Amount Carried at close of period 12/31/2019, Land 8,160,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 37,871,061      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 46,031,061      
Accumulated Depreciation (26,472,405)      
Investment in Real Estate, Net 19,558,656      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Mosaic at Metro [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Hyattsville, MD      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 260      
Initial Cost to Company, Land $ 0      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 59,580,898      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,537,111      
Gross Amount Carried at close of period 12/31/2019, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 61,118,009      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 61,118,009      
Accumulated Depreciation (23,624,406)      
Investment in Real Estate, Net 37,493,603      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Mountain View Redevelopment [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Mountain View, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 0      
Initial Cost to Company, Land $ 0      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 882,046      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2019, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 882,046      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 882,046      
Accumulated Depreciation 0      
Investment in Real Estate, Net 882,046      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Mozaic at Union Station [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Los Angeles, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 272      
Initial Cost to Company, Land $ 8,500,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 52,529,446      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,472,824      
Gross Amount Carried at close of period 12/31/2019, Land 8,500,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 55,002,270      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 63,502,270      
Accumulated Depreciation (26,004,162)      
Investment in Real Estate, Net 37,498,108      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Murray Hill Tower (fka Murray Hill) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location New York, NY      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 270      
Initial Cost to Company, Land $ 75,800,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 102,705,401      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 10,547,453      
Gross Amount Carried at close of period 12/31/2019, Land 75,800,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 113,252,854      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 189,052,854      
Accumulated Depreciation (34,480,104)      
Investment in Real Estate, Net 154,572,750      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Next on Sixth [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Los Angeles, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 398      
Initial Cost to Company, Land $ 52,509,906      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 136,635,362      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 52,028      
Gross Amount Carried at close of period 12/31/2019, Land 52,509,906      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 136,687,390      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 189,197,296      
Accumulated Depreciation (6,067,150)      
Investment in Real Estate, Net 183,130,146      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
North Pier at Harborside [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Jersey City, NJ      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 297      
Initial Cost to Company, Land $ 4,000,159      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 94,290,590      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 5,767,779      
Gross Amount Carried at close of period 12/31/2019, Land 4,000,159      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 100,058,369      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 104,058,528      
Accumulated Depreciation (53,298,183)      
Investment in Real Estate, Net 50,760,345      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Northglen [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Valencia, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 234      
Initial Cost to Company, Land $ 9,360,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 20,778,553      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 6,828,841      
Gross Amount Carried at close of period 12/31/2019, Land 9,360,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 27,607,394      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 36,967,394      
Accumulated Depreciation (16,473,980)      
Investment in Real Estate, Net 20,493,414      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Northpark [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Burlingame, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 510      
Initial Cost to Company, Land $ 38,607,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 77,472,217      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 15,236,070      
Gross Amount Carried at close of period 12/31/2019, Land 38,607,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 92,708,287      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 131,315,287      
Accumulated Depreciation (40,034,278)      
Investment in Real Estate, Net 91,281,009      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Northridge [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Pleasant Hill, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 221      
Initial Cost to Company, Land $ 5,524,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 14,691,705      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 11,618,255      
Gross Amount Carried at close of period 12/31/2019, Land 5,524,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 26,309,960      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 31,833,960      
Accumulated Depreciation (20,784,027)      
Investment in Real Estate, Net 11,049,933      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Oak Park Combined [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Agoura Hills, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 444      
Initial Cost to Company, Land $ 3,390,700      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 30,517,274      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 11,129,906      
Gross Amount Carried at close of period 12/31/2019, Land 3,390,700      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 41,647,180      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 45,037,880      
Accumulated Depreciation (33,598,181)      
Investment in Real Estate, Net 11,439,699      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Oaks [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Santa Clarita, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 520      
Initial Cost to Company, Land $ 23,400,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 61,020,438      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 7,150,916      
Gross Amount Carried at close of period 12/31/2019, Land 23,400,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 68,171,354      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 91,571,354      
Accumulated Depreciation (38,896,036)      
Investment in Real Estate, Net 52,675,318      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Oakwood Crystal City [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Arlington, VA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 162      
Initial Cost to Company, Land $ 15,400,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 35,474,336      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,164,931      
Gross Amount Carried at close of period 12/31/2019, Land 15,400,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 39,639,267      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 55,039,267      
Accumulated Depreciation (11,715,439)      
Investment in Real Estate, Net 43,323,828      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Ocean Crest [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Solana Beach, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 146      
Initial Cost to Company, Land $ 5,111,200      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 11,910,438      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,831,677      
Gross Amount Carried at close of period 12/31/2019, Land 5,111,200      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 16,742,115      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 21,853,315      
Accumulated Depreciation (11,831,439)      
Investment in Real Estate, Net 10,021,876      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Odin (fka Tallman) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Seattle, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 301      
Initial Cost to Company, Land $ 16,807,519      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 64,519,515      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 70,389      
Gross Amount Carried at close of period 12/31/2019, Land 16,807,519      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 64,589,904      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 81,397,423      
Accumulated Depreciation (11,050,157)      
Investment in Real Estate, Net 70,347,266      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Old Town Lofts [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Redmond, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 149      
Initial Cost to Company, Land $ 7,740,467      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 44,146,181      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 821,523      
Gross Amount Carried at close of period 12/31/2019, Land 7,740,467      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 44,967,704      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 52,708,171      
Accumulated Depreciation (8,666,808)      
Investment in Real Estate, Net 44,041,363      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Olympus Towers [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Seattle, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 328      
Initial Cost to Company, Land $ 14,752,034      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 73,335,425      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 10,370,617      
Gross Amount Carried at close of period 12/31/2019, Land 14,752,034      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 83,706,042      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 98,458,076      
Accumulated Depreciation (46,375,373)      
Investment in Real Estate, Net 52,082,703      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
One Henry Adams [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location San Francisco, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 241      
Initial Cost to Company, Land $ 30,224,393      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 139,558,692      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 22,022      
Gross Amount Carried at close of period 12/31/2019, Land 30,224,393      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 139,580,714      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 169,805,107      
Accumulated Depreciation (16,605,628)      
Investment in Real Estate, Net 153,199,479      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
One India Street (fka Oakwood Boston) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Boston, MA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 94      
Initial Cost to Company, Land $ 22,200,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 28,672,979      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 6,249,693      
Gross Amount Carried at close of period 12/31/2019, Land 22,200,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 34,922,672      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 57,122,672      
Accumulated Depreciation (9,689,007)      
Investment in Real Estate, Net 47,433,665      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Pacific Place [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Los Angeles, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 430      
Initial Cost to Company, Land $ 32,250,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 110,750,000      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,028,500      
Gross Amount Carried at close of period 12/31/2019, Land 32,250,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 112,778,500      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 145,028,500      
Accumulated Depreciation (31,554,841)      
Investment in Real Estate, Net 113,473,659      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Packard Building [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Seattle, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 61      
Initial Cost to Company, Land $ 5,911,041      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 19,954,959      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,112,353      
Gross Amount Carried at close of period 12/31/2019, Land 5,911,041      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 21,067,312      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 26,978,353      
Accumulated Depreciation (3,941,611)      
Investment in Real Estate, Net 23,036,742      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Parc 77 [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location New York, NY      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 137      
Initial Cost to Company, Land $ 40,504,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 18,025,679      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 6,560,029      
Gross Amount Carried at close of period 12/31/2019, Land 40,504,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 24,585,708      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 65,089,708      
Accumulated Depreciation (14,088,276)      
Investment in Real Estate, Net 51,001,432      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Parc Cameron [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location New York, NY      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 166      
Initial Cost to Company, Land $ 37,600,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 9,855,597      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 7,590,854      
Gross Amount Carried at close of period 12/31/2019, Land 37,600,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 17,446,451      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 55,046,451      
Accumulated Depreciation (11,702,099)      
Investment in Real Estate, Net 43,344,352      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Parc Coliseum [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location New York, NY      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 177      
Initial Cost to Company, Land $ 52,654,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 23,045,751      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 9,553,310      
Gross Amount Carried at close of period 12/31/2019, Land 52,654,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 32,599,061      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 85,253,061      
Accumulated Depreciation (19,280,179)      
Investment in Real Estate, Net 65,972,882      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Parc East Towers [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location New York, NY      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 324      
Initial Cost to Company, Land $ 102,163,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 108,989,402      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 12,219,604      
Gross Amount Carried at close of period 12/31/2019, Land 102,163,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 121,209,006      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 223,372,006      
Accumulated Depreciation (56,644,803)      
Investment in Real Estate, Net 166,727,203      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Parc on Powell (fka Parkside at Emeryville) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Emeryville, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 173      
Initial Cost to Company, Land $ 16,667,059      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 65,073,509      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 419,037      
Gross Amount Carried at close of period 12/31/2019, Land 16,667,059      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 65,492,546      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 82,159,605      
Accumulated Depreciation (12,009,148)      
Investment in Real Estate, Net 70,150,457      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Park Connecticut [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Washington, D.C.      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 142      
Initial Cost to Company, Land $ 13,700,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 59,087,519      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,863,350      
Gross Amount Carried at close of period 12/31/2019, Land 13,700,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 60,950,869      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 74,650,869      
Accumulated Depreciation (16,566,168)      
Investment in Real Estate, Net 58,084,701      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Park Hacienda (fka Hacienda) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Pleasanton, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 540      
Initial Cost to Company, Land $ 43,200,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 128,753,359      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 6,614,073      
Gross Amount Carried at close of period 12/31/2019, Land 43,200,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 135,367,432      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 178,567,432      
Accumulated Depreciation (39,974,119)      
Investment in Real Estate, Net 138,593,313      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Park West (CA) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Los Angeles, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 444      
Initial Cost to Company, Land $ 3,033,500      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 27,302,383      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 12,126,113      
Gross Amount Carried at close of period 12/31/2019, Land 3,033,500      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 39,428,496      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 42,461,996      
Accumulated Depreciation (30,924,343)      
Investment in Real Estate, Net 11,537,653      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Parkside [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Union City, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 208      
Initial Cost to Company, Land $ 6,246,700      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 11,827,453      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 8,185,992      
Gross Amount Carried at close of period 12/31/2019, Land 6,246,700      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 20,013,445      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 26,260,145      
Accumulated Depreciation (13,217,770)      
Investment in Real Estate, Net 13,042,375      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Pearl, The (WA) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Seattle, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 80      
Initial Cost to Company, Land $ 6,972,585      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 26,527,415      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,051,124      
Gross Amount Carried at close of period 12/31/2019, Land 6,972,585      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 27,578,539      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 34,551,124      
Accumulated Depreciation (5,151,187)      
Investment in Real Estate, Net 29,399,937      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Pearl MDR (fka Oakwood Marina Del Rey) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Marina Del Rey, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 597      
Initial Cost to Company, Land $ 0      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 120,795,359      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 5,726,479      
Gross Amount Carried at close of period 12/31/2019, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 126,521,838      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 126,521,838      
Accumulated Depreciation (38,784,120)      
Investment in Real Estate, Net 87,737,718      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Pegasus [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Los Angeles, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 322      
Initial Cost to Company, Land $ 18,094,052      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 81,905,948      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 6,904,081      
Gross Amount Carried at close of period 12/31/2019, Land 18,094,052      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 88,810,029      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 106,904,081      
Accumulated Depreciation (32,523,925)      
Investment in Real Estate, Net 74,380,156      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Playa Pacifica [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Hermosa Beach, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 285      
Initial Cost to Company, Land $ 35,100,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 33,473,822      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 23,756,377      
Gross Amount Carried at close of period 12/31/2019, Land 35,100,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 57,230,199      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 92,330,199      
Accumulated Depreciation (31,171,766)      
Investment in Real Estate, Net 61,158,433      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Portofino [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Chino Hills, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 176      
Initial Cost to Company, Land $ 3,572,400      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 14,660,994      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,874,242      
Gross Amount Carried at close of period 12/31/2019, Land 3,572,400      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 18,535,236      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 22,107,636      
Accumulated Depreciation (14,171,043)      
Investment in Real Estate, Net 7,936,593      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Portofino (Val) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Valencia, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 216      
Initial Cost to Company, Land $ 8,640,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 21,487,126      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 5,837,031      
Gross Amount Carried at close of period 12/31/2019, Land 8,640,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 27,324,157      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 35,964,157      
Accumulated Depreciation (17,518,529)      
Investment in Real Estate, Net 18,445,628      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Portside Towers [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Jersey City, NJ      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 527      
Initial Cost to Company, Land $ 22,487,006      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 96,842,913      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 24,128,821      
Gross Amount Carried at close of period 12/31/2019, Land 22,487,006      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 120,971,734      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 143,458,740      
Accumulated Depreciation (89,422,204)      
Investment in Real Estate, Net 54,036,536      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Potrero 1010 [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location San Francisco, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 453      
Initial Cost to Company, Land $ 40,830,011      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 181,812,933      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 518,975      
Gross Amount Carried at close of period 12/31/2019, Land 40,830,011      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 182,331,908      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 223,161,919      
Accumulated Depreciation (26,294,704)      
Investment in Real Estate, Net 196,867,215      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Prado (fka Glendale) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Glendale, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 264      
Initial Cost to Company, Land $ 0      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 67,977,313      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 5,928,659      
Gross Amount Carried at close of period 12/31/2019, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 73,905,972      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 73,905,972      
Accumulated Depreciation (21,102,334)      
Investment in Real Estate, Net 52,803,638      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Prime, The [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Arlington, VA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 281      
Initial Cost to Company, Land $ 34,625,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 77,879,740      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,669,467      
Gross Amount Carried at close of period 12/31/2019, Land 34,625,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 80,549,207      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 115,174,207      
Accumulated Depreciation (32,656,903)      
Investment in Real Estate, Net 82,517,304      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Prism at Park Avenue South (fka 400 Park Aveue South (EQR)) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location New York, NY      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 269      
Initial Cost to Company, Land $ 76,292,169      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 171,649,131      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 208,922      
Gross Amount Carried at close of period 12/31/2019, Land 76,292,169      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 171,858,053      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 248,150,222      
Accumulated Depreciation (32,299,311)      
Investment in Real Estate, Net 215,850,911      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Promenade at Town Center I & II [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Valencia, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 564      
Initial Cost to Company, Land $ 28,200,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 69,795,915      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 10,883,962      
Gross Amount Carried at close of period 12/31/2019, Land 28,200,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 80,679,877      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 108,879,877      
Accumulated Depreciation (44,391,535)      
Investment in Real Estate, Net 64,488,342      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Providence [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Bothell, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 200      
Initial Cost to Company, Land $ 3,573,621      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 19,055,505      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,537,035      
Gross Amount Carried at close of period 12/31/2019, Land 3,573,621      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 23,592,540      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 27,166,161      
Accumulated Depreciation (12,025,867)      
Investment in Real Estate, Net 15,140,294      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Quarry Hills [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Quincy, MA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 316      
Initial Cost to Company, Land $ 26,900,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 84,411,162      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,202,638      
Gross Amount Carried at close of period 12/31/2019, Land 26,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 88,613,800      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 115,513,800      
Accumulated Depreciation (25,515,603)      
Investment in Real Estate, Net 89,998,197      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Radius Uptown [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Denver, CO      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 372      
Initial Cost to Company, Land $ 13,644,960      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 121,899,084      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 640,652      
Gross Amount Carried at close of period 12/31/2019, Land 13,644,960      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 122,539,736      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 136,184,696      
Accumulated Depreciation (9,914,578)      
Investment in Real Estate, Net 126,270,118      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Red 160 (fka Redmond Way) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Redmond, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 250      
Initial Cost to Company, Land $ 15,546,376      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 65,320,010      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,448,098      
Gross Amount Carried at close of period 12/31/2019, Land 15,546,376      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 66,768,108      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 82,314,484      
Accumulated Depreciation (20,622,372)      
Investment in Real Estate, Net 61,692,112      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Redmond Court [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Bellevue, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 206      
Initial Cost to Company, Land $ 10,300,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 33,488,745      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,211,705      
Gross Amount Carried at close of period 12/31/2019, Land 10,300,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 34,700,450      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 45,000,450      
Accumulated Depreciation (11,274,160)      
Investment in Real Estate, Net 33,726,290      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Regency Palms [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Huntington Beach, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 310      
Initial Cost to Company, Land $ 1,857,400      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 16,713,254      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 7,272,427      
Gross Amount Carried at close of period 12/31/2019, Land 1,857,400      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 23,985,681      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 25,843,081      
Accumulated Depreciation (19,161,878)      
Investment in Real Estate, Net 6,681,203      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Reserve at Clarendon Centre, The [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Arlington, VA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 252      
Initial Cost to Company, Land $ 10,500,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 52,812,935      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,855,911      
Gross Amount Carried at close of period 12/31/2019, Land 10,500,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 57,668,846      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 68,168,846      
Accumulated Depreciation (32,743,477)      
Investment in Real Estate, Net 35,425,369      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Reserve at Eisenhower, The [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Alexandria, VA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 226      
Initial Cost to Company, Land $ 6,500,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 34,585,060      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,852,458      
Gross Amount Carried at close of period 12/31/2019, Land 6,500,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 39,437,518      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 45,937,518      
Accumulated Depreciation (22,240,250)      
Investment in Real Estate, Net 23,697,268      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Reserve at Empire Lakes [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Rancho Cucamonga, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 467      
Initial Cost to Company, Land $ 16,345,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 73,080,670      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,893,736      
Gross Amount Carried at close of period 12/31/2019, Land 16,345,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 76,974,406      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 93,319,406      
Accumulated Depreciation (39,080,433)      
Investment in Real Estate, Net 54,238,973      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Reserve at Fairfax Corner [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Fairfax, VA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 652      
Initial Cost to Company, Land $ 15,804,057      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 63,129,051      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 12,239,068      
Gross Amount Carried at close of period 12/31/2019, Land 15,804,057      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 75,368,119      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 91,172,176      
Accumulated Depreciation (44,632,394)      
Investment in Real Estate, Net 46,539,782      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Reserve at Mountain View (fka Mountain View) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Mountain View, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 180      
Initial Cost to Company, Land $ 27,000,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 33,029,605      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 7,608,914      
Gross Amount Carried at close of period 12/31/2019, Land 27,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 40,638,519      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 67,638,519      
Accumulated Depreciation (12,863,114)      
Investment in Real Estate, Net 54,775,405      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Reserve at Potomac Yard [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Alexandria, VA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 588      
Initial Cost to Company, Land $ 11,918,917      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 68,862,641      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 17,256,235      
Gross Amount Carried at close of period 12/31/2019, Land 11,918,917      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 86,118,876      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 98,037,793      
Accumulated Depreciation (45,846,659)      
Investment in Real Estate, Net 52,191,134      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Reserve at Town Center I-III (WA) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Mill Creek, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 584      
Initial Cost to Company, Land $ 16,768,705      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 77,623,664      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 8,538,253      
Gross Amount Carried at close of period 12/31/2019, Land 16,768,705      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 86,161,917      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 102,930,622      
Accumulated Depreciation (36,697,179)      
Investment in Real Estate, Net 66,233,443      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Residences at Westgate I (fka Westgate II) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Pasadena, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 252      
Initial Cost to Company, Land $ 17,859,785      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 109,259,858      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 477,844      
Gross Amount Carried at close of period 12/31/2019, Land 17,859,785      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 109,737,702      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 127,597,487      
Accumulated Depreciation (27,267,435)      
Investment in Real Estate, Net 100,330,052      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Residences at Westgate II (fka Westgate III) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Pasadena, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 88      
Initial Cost to Company, Land $ 12,118,248      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 40,486,467      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 97,831      
Gross Amount Carried at close of period 12/31/2019, Land 12,118,248      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 40,584,298      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 52,702,546      
Accumulated Depreciation (7,453,042)      
Investment in Real Estate, Net 45,249,504      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Rianna I & II [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Seattle, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 156      
Initial Cost to Company, Land $ 4,430,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 29,298,096      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,408,357      
Gross Amount Carried at close of period 12/31/2019, Land 4,430,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 30,706,453      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 35,136,453      
Accumulated Depreciation (12,521,975)      
Investment in Real Estate, Net 22,614,478      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Ridgewood Village I&II [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location San Diego, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 408      
Initial Cost to Company, Land $ 11,809,500      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 34,004,048      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 6,152,653      
Gross Amount Carried at close of period 12/31/2019, Land 11,809,500      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 40,156,701      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 51,966,201      
Accumulated Depreciation (27,801,818)      
Investment in Real Estate, Net 24,164,383      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Riva Terra I (fka Redwood Shores) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Redwood City, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 304      
Initial Cost to Company, Land $ 34,963,355      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 84,587,658      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 6,552,889      
Gross Amount Carried at close of period 12/31/2019, Land 34,963,355      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 91,140,547      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 126,103,902      
Accumulated Depreciation (27,578,186)      
Investment in Real Estate, Net 98,525,716      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Riva Terra II (fka Harborside) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Redwood City, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 149      
Initial Cost to Company, Land $ 17,136,645      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 40,536,531      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,532,047      
Gross Amount Carried at close of period 12/31/2019, Land 17,136,645      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 44,068,578      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 61,205,223      
Accumulated Depreciation (12,214,368)      
Investment in Real Estate, Net 48,990,855      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Riverpark [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Redmond, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 321      
Initial Cost to Company, Land $ 14,355,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 80,894,049      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,145,694      
Gross Amount Carried at close of period 12/31/2019, Land 14,355,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 85,039,743      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 99,394,743      
Accumulated Depreciation (27,531,587)      
Investment in Real Estate, Net 71,863,156      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Rivington, The [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Hoboken, NJ      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 240      
Initial Cost to Company, Land $ 34,340,640      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 112,522,073      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,385,966      
Gross Amount Carried at close of period 12/31/2019, Land 34,340,640      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 114,908,039      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 149,248,679      
Accumulated Depreciation (11,203,805)      
Investment in Real Estate, Net 138,044,874      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Rosecliff II [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Quincy, MA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 130      
Initial Cost to Company, Land $ 4,922,840      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 30,202,160      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,575,032      
Gross Amount Carried at close of period 12/31/2019, Land 4,922,840      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 31,777,192      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 36,700,032      
Accumulated Depreciation (11,139,316)      
Investment in Real Estate, Net 25,560,716      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Sakura Crossing [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Los Angeles, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 230      
Initial Cost to Company, Land $ 14,641,990      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 42,858,010      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,508,474      
Gross Amount Carried at close of period 12/31/2019, Land 14,641,990      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 44,366,484      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 59,008,474      
Accumulated Depreciation (16,104,349)      
Investment in Real Estate, Net 42,904,125      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Saxton [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Seattle, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 325      
Initial Cost to Company, Land $ 38,805,400      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 128,661,766      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,221      
Gross Amount Carried at close of period 12/31/2019, Land 38,805,400      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 128,662,987      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 167,468,387      
Accumulated Depreciation (1,106,731)      
Investment in Real Estate, Net 166,361,656      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Seventh & James [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Seattle, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 96      
Initial Cost to Company, Land $ 663,800      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 5,974,803      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,559,907      
Gross Amount Carried at close of period 12/31/2019, Land 663,800      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 10,534,710      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 11,198,510      
Accumulated Depreciation (8,193,189)      
Investment in Real Estate, Net 3,005,321      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Sheffield Court [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Arlington, VA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 597      
Initial Cost to Company, Land $ 3,342,381      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 31,337,332      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 16,837,180      
Gross Amount Carried at close of period 12/31/2019, Land 3,342,381      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 48,174,512      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 51,516,893      
Accumulated Depreciation (39,604,857)      
Investment in Real Estate, Net 11,912,036      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Siena Terrace [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Lake Forest, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 356      
Initial Cost to Company, Land $ 8,900,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 24,083,024      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 7,673,467      
Gross Amount Carried at close of period 12/31/2019, Land 8,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 31,756,491      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 40,656,491      
Accumulated Depreciation (22,703,857)      
Investment in Real Estate, Net 17,952,634      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Skycrest [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Valencia, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 264      
Initial Cost to Company, Land $ 10,560,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 25,574,457      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 6,439,296      
Gross Amount Carried at close of period 12/31/2019, Land 10,560,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 32,013,753      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 42,573,753      
Accumulated Depreciation (19,701,076)      
Investment in Real Estate, Net 22,872,677      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Skyhouse Denver [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Denver, CO      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 354      
Initial Cost to Company, Land $ 13,562,331      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 126,360,318      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 260,188      
Gross Amount Carried at close of period 12/31/2019, Land 13,562,331      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 126,620,506      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 140,182,837      
Accumulated Depreciation (10,544,133)      
Investment in Real Estate, Net 129,638,704      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Skylark [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Union City, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 174      
Initial Cost to Company, Land $ 1,781,600      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 16,731,916      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 5,693,705      
Gross Amount Carried at close of period 12/31/2019, Land 1,781,600      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 22,425,621      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 24,207,221      
Accumulated Depreciation (15,390,513)      
Investment in Real Estate, Net 8,816,708      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Skyline Terrace [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Burlingame, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 138      
Initial Cost to Company, Land $ 16,836,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 35,414,000      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 8,685,848      
Gross Amount Carried at close of period 12/31/2019, Land 16,836,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 44,099,848      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 60,935,848      
Accumulated Depreciation (16,883,846)      
Investment in Real Estate, Net 44,052,002      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Skyview [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Rancho Santa Margarita, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 260      
Initial Cost to Company, Land $ 3,380,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 21,952,863      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 5,952,747      
Gross Amount Carried at close of period 12/31/2019, Land 3,380,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 27,905,610      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 31,285,610      
Accumulated Depreciation (18,956,521)      
Investment in Real Estate, Net 12,329,089      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
SoMa II [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location San Francisco, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 0      
Initial Cost to Company, Land $ 29,406,606      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 5,863,582      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2019, Land 29,406,606      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 5,863,582      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 35,270,188      
Accumulated Depreciation 0      
Investment in Real Estate, Net 35,270,188      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Sonterra at Foothill Ranch [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Foothill Ranch, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 300      
Initial Cost to Company, Land $ 7,503,400      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 24,048,507      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 6,103,825      
Gross Amount Carried at close of period 12/31/2019, Land 7,503,400      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 30,152,332      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 37,655,732      
Accumulated Depreciation (21,265,834)      
Investment in Real Estate, Net 16,389,898      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
South City Station (fka South San Francisco) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location San Francisco, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 368      
Initial Cost to Company, Land $ 68,900,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 79,476,861      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 5,496,725      
Gross Amount Carried at close of period 12/31/2019, Land 68,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 84,973,586      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 153,873,586      
Accumulated Depreciation (24,542,210)      
Investment in Real Estate, Net 129,331,376      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Southwood [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Palo Alto, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 100      
Initial Cost to Company, Land $ 6,936,600      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 14,324,069      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 6,974,332      
Gross Amount Carried at close of period 12/31/2019, Land 6,936,600      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 21,298,401      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 28,235,001      
Accumulated Depreciation (13,871,734)      
Investment in Real Estate, Net 14,363,267      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Springbrook Estates [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Riverside, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 0      
Initial Cost to Company, Land $ 18,200,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 1,145,000      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2019, Land 18,200,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 1,145,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 19,345,000      
Accumulated Depreciation 0      
Investment in Real Estate, Net 19,345,000      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Springline [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Seattle, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 136      
Initial Cost to Company, Land $ 9,163,667      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 47,910,981      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 413,447      
Gross Amount Carried at close of period 12/31/2019, Land 9,163,667      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 48,324,428      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 57,488,095      
Accumulated Depreciation (6,348,664)      
Investment in Real Estate, Net 51,139,431      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
STOA [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Los Angeles, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 237      
Initial Cost to Company, Land $ 25,326,048      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 79,976,031      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 355,097      
Gross Amount Carried at close of period 12/31/2019, Land 25,326,048      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 80,331,128      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 105,657,176      
Accumulated Depreciation (4,420,377)      
Investment in Real Estate, Net 101,236,799      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Summerset Village [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Chatsworth, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 280      
Initial Cost to Company, Land $ 2,890,450      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 23,670,889      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 8,502,754      
Gross Amount Carried at close of period 12/31/2019, Land 2,890,450      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 32,173,643      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 35,064,093      
Accumulated Depreciation (25,071,401)      
Investment in Real Estate, Net 9,992,692      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Summit at Sausalito (fka Sausalito) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Sausalito, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 198      
Initial Cost to Company, Land $ 26,000,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 28,435,024      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 9,826,451      
Gross Amount Carried at close of period 12/31/2019, Land 26,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 38,261,475      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 64,261,475      
Accumulated Depreciation (13,610,363)      
Investment in Real Estate, Net 50,651,112      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Ten23 (fka 500 West 23rd Street) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location New York, NY      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 111      
Initial Cost to Company, Land $ 0      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 58,881,873      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 839,289      
Gross Amount Carried at close of period 12/31/2019, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 59,721,162      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 59,721,162      
Accumulated Depreciation (16,244,073)      
Investment in Real Estate, Net 43,477,089      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Terraces, The [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location San Francisco, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 117      
Initial Cost to Company, Land $ 14,087,610      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 16,314,151      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,303,726      
Gross Amount Carried at close of period 12/31/2019, Land 14,087,610      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 18,617,877      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 32,705,487      
Accumulated Depreciation (7,132,658)      
Investment in Real Estate, Net 25,572,829      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Third Square [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Cambridge, MA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 471      
Initial Cost to Company, Land $ 26,767,171      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 218,822,728      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 8,710,964      
Gross Amount Carried at close of period 12/31/2019, Land 26,767,171      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 227,533,692      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 254,300,863      
Accumulated Depreciation (86,467,715)      
Investment in Real Estate, Net 167,833,148      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Three20 [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Seattle, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 134      
Initial Cost to Company, Land $ 7,030,766      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 29,005,762      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 783,255      
Gross Amount Carried at close of period 12/31/2019, Land 7,030,766      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 29,789,017      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 36,819,783      
Accumulated Depreciation (8,010,054)      
Investment in Real Estate, Net 28,809,729      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Toscana [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Irvine, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 563      
Initial Cost to Company, Land $ 39,410,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 50,806,072      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 23,541,748      
Gross Amount Carried at close of period 12/31/2019, Land 39,410,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 74,347,820      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 113,757,820      
Accumulated Depreciation (44,385,604)      
Investment in Real Estate, Net 69,372,216      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Town Square at Mark Center I (fka Millbrook I) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Alexandria, VA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 406      
Initial Cost to Company, Land $ 24,360,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 86,178,714      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 9,536,594      
Gross Amount Carried at close of period 12/31/2019, Land 24,360,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 95,715,308      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 120,075,308      
Accumulated Depreciation (47,769,571)      
Investment in Real Estate, Net 72,305,737      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Town Square at Mark Center II [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Alexandria, VA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 272      
Initial Cost to Company, Land $ 15,568,464      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 55,029,607      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,431,783      
Gross Amount Carried at close of period 12/31/2019, Land 15,568,464      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 59,461,390      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 75,029,854      
Accumulated Depreciation (23,267,306)      
Investment in Real Estate, Net 51,762,548      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Troy Boston [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Boston, MA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 378      
Initial Cost to Company, Land $ 34,641,051      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 181,607,331      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 657,969      
Gross Amount Carried at close of period 12/31/2019, Land 34,641,051      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 182,265,300      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 216,906,351      
Accumulated Depreciation (16,175,931)      
Investment in Real Estate, Net 200,730,420      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Urbana (fka Market Street Landing) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Seattle, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 289      
Initial Cost to Company, Land $ 12,542,418      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 75,800,090      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,128,448      
Gross Amount Carried at close of period 12/31/2019, Land 12,542,418      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 77,928,538      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 90,470,956      
Accumulated Depreciation (20,704,557)      
Investment in Real Estate, Net 69,766,399      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Uwajimaya Village [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Seattle, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 176      
Initial Cost to Company, Land $ 8,800,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 22,188,288      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,603,487      
Gross Amount Carried at close of period 12/31/2019, Land 8,800,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 26,791,775      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 35,591,775      
Accumulated Depreciation (12,717,581)      
Investment in Real Estate, Net 22,874,194      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Vantage Pointe [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location San Diego, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 679      
Initial Cost to Company, Land $ 9,403,960      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 190,596,040      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 10,700,900      
Gross Amount Carried at close of period 12/31/2019, Land 9,403,960      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 201,296,940      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 210,700,900      
Accumulated Depreciation (73,412,146)      
Investment in Real Estate, Net 137,288,754      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Veloce [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Redmond, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 322      
Initial Cost to Company, Land $ 15,322,724      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 76,176,594      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,876,091      
Gross Amount Carried at close of period 12/31/2019, Land 15,322,724      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 78,052,685      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 93,375,409      
Accumulated Depreciation (23,071,740)      
Investment in Real Estate, Net 70,303,669      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Venue at the Promenade [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Castle Rock, CO      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 312      
Initial Cost to Company, Land $ 8,355,048      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 83,752,689      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 89,298      
Gross Amount Carried at close of period 12/31/2019, Land 8,355,048      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 83,841,987      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 92,197,035      
Accumulated Depreciation (4,260,814)      
Investment in Real Estate, Net 87,936,221      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Verde Condominium Homes (fka Mission Verde, LLC) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location San Jose, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 108      
Initial Cost to Company, Land $ 5,190,700      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 9,679,109      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,541,057      
Gross Amount Carried at close of period 12/31/2019, Land 5,190,700      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 14,220,166      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 19,410,866      
Accumulated Depreciation (10,817,710)      
Investment in Real Estate, Net 8,593,156      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Veridian (fka Silver Spring) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Silver Spring, MD      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 457      
Initial Cost to Company, Land $ 18,539,817      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 130,407,365      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,911,967      
Gross Amount Carried at close of period 12/31/2019, Land 18,539,817      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 134,319,332      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 152,859,149      
Accumulated Depreciation (48,528,051)      
Investment in Real Estate, Net 104,331,098      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Versailles [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Woodland Hills, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 253      
Initial Cost to Company, Land $ 12,650,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 33,656,292      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 8,301,520      
Gross Amount Carried at close of period 12/31/2019, Land 12,650,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 41,957,812      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 54,607,812      
Accumulated Depreciation (24,444,631)      
Investment in Real Estate, Net 30,163,181      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Versailles (K-Town) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Los Angeles, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 225      
Initial Cost to Company, Land $ 10,590,975      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 44,409,025      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,768,461      
Gross Amount Carried at close of period 12/31/2019, Land 10,590,975      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 46,177,486      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 56,768,461      
Accumulated Depreciation (18,704,272)      
Investment in Real Estate, Net 38,064,189      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Victor on Venice [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Los Angeles, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 115      
Initial Cost to Company, Land $ 10,350,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 35,433,437      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,455,531      
Gross Amount Carried at close of period 12/31/2019, Land 10,350,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 36,888,968      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 47,238,968      
Accumulated Depreciation (17,138,982)      
Investment in Real Estate, Net 30,099,986      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Villa Solana [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Laguna Hills, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 272      
Initial Cost to Company, Land $ 1,665,100      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 14,985,677      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 11,916,441      
Gross Amount Carried at close of period 12/31/2019, Land 1,665,100      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 26,902,118      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 28,567,218      
Accumulated Depreciation (21,819,381)      
Investment in Real Estate, Net 6,747,837      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Village at Del Mar Heights, The (fka Del Mar Heights) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location San Diego, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 168      
Initial Cost to Company, Land $ 15,100,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 40,859,396      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,059,227      
Gross Amount Carried at close of period 12/31/2019, Land 15,100,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 43,918,623      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 59,018,623      
Accumulated Depreciation (13,135,144)      
Investment in Real Estate, Net 45,883,479      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Virginia Square [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Arlington, VA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 231      
Initial Cost to Company, Land $ 0      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 85,940,003      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 6,071,125      
Gross Amount Carried at close of period 12/31/2019, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 92,011,128      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 92,011,128      
Accumulated Depreciation (25,981,773)      
Investment in Real Estate, Net 66,029,355      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Vista 99 (fka Tasman) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location San Jose, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 554      
Initial Cost to Company, Land $ 27,709,329      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 177,551,020      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 530,009      
Gross Amount Carried at close of period 12/31/2019, Land 27,709,329      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 178,081,029      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 205,790,358      
Accumulated Depreciation (26,777,048)      
Investment in Real Estate, Net 179,013,310      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Vista Del Lago [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Mission Viejo, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 608      
Initial Cost to Company, Land $ 4,525,800      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 40,736,293      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 18,471,821      
Gross Amount Carried at close of period 12/31/2019, Land 4,525,800      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 59,208,114      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 63,733,914      
Accumulated Depreciation (50,585,532)      
Investment in Real Estate, Net 13,148,382      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Walden Park [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Cambridge, MA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 232      
Initial Cost to Company, Land $ 12,448,888      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 52,044,448      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,534,927      
Gross Amount Carried at close of period 12/31/2019, Land 12,448,888      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 56,579,375      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 69,028,263      
Accumulated Depreciation (21,419,276)      
Investment in Real Estate, Net 47,608,987      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Water Park Towers [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Arlington, VA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 362      
Initial Cost to Company, Land $ 34,400,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 108,485,859      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 10,352,960      
Gross Amount Carried at close of period 12/31/2019, Land 34,400,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 118,838,819      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 153,238,819      
Accumulated Depreciation (34,973,941)      
Investment in Real Estate, Net 118,264,878      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Watertown Square [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Watertown, MA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 134      
Initial Cost to Company, Land $ 16,800,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 34,074,056      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,780,526      
Gross Amount Carried at close of period 12/31/2019, Land 16,800,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 35,854,582      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 52,654,582      
Accumulated Depreciation (10,288,446)      
Investment in Real Estate, Net 42,366,136      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
West 96th [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location New York, NY      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 207      
Initial Cost to Company, Land $ 84,800,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 67,055,501      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 6,032,361      
Gross Amount Carried at close of period 12/31/2019, Land 84,800,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 73,087,862      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 157,887,862      
Accumulated Depreciation (23,339,208)      
Investment in Real Estate, Net 134,548,654      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
West End Apartments (fka Emerson Place/CRP II) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Boston, MA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 310      
Initial Cost to Company, Land $ 469,546      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 163,123,022      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,644,170      
Gross Amount Carried at close of period 12/31/2019, Land 469,546      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 167,767,192      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 168,236,738      
Accumulated Depreciation (67,233,339)      
Investment in Real Estate, Net 101,003,399      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Westchester at Rockville [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Rockville, MD      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 192      
Initial Cost to Company, Land $ 10,600,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 44,135,207      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,115,325      
Gross Amount Carried at close of period 12/31/2019, Land 10,600,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 45,250,532      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 55,850,532      
Accumulated Depreciation (12,723,620)      
Investment in Real Estate, Net 43,126,912      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Westmont [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location New York, NY      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 163      
Initial Cost to Company, Land $ 64,900,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 61,143,259      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 5,556,773      
Gross Amount Carried at close of period 12/31/2019, Land 64,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 66,700,032      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 131,600,032      
Accumulated Depreciation (19,263,749)      
Investment in Real Estate, Net 112,336,283      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Westside [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Los Angeles, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 204      
Initial Cost to Company, Land $ 34,200,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 56,962,630      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,224,934      
Gross Amount Carried at close of period 12/31/2019, Land 34,200,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 60,187,564      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 94,387,564      
Accumulated Depreciation (17,012,037)      
Investment in Real Estate, Net 77,375,527      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Westside Barrington (fka Westside Villas III) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Los Angeles, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 36      
Initial Cost to Company, Land $ 3,060,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 5,538,871      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,138,171      
Gross Amount Carried at close of period 12/31/2019, Land 3,060,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 6,677,042      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 9,737,042      
Accumulated Depreciation (4,172,543)      
Investment in Real Estate, Net 5,564,499      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Westside Barry (Westside Villas VI) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Los Angeles, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 18      
Initial Cost to Company, Land $ 1,530,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 3,023,523      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 731,986      
Gross Amount Carried at close of period 12/31/2019, Land 1,530,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 3,755,509      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 5,285,509      
Accumulated Depreciation (2,345,294)      
Investment in Real Estate, Net 2,940,215      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Westside Beloit (fka Westside Villas I) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Los Angeles, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 21      
Initial Cost to Company, Land $ 1,785,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 3,233,254      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 748,943      
Gross Amount Carried at close of period 12/31/2019, Land 1,785,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 3,982,197      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 5,767,197      
Accumulated Depreciation (2,551,527)      
Investment in Real Estate, Net 3,215,670      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Westside Bundy (fka Westside Villas II) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Los Angeles, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 23      
Initial Cost to Company, Land $ 1,955,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 3,541,435      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 760,287      
Gross Amount Carried at close of period 12/31/2019, Land 1,955,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 4,301,722      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 6,256,722      
Accumulated Depreciation (2,680,002)      
Investment in Real Estate, Net 3,576,720      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Westside Butler (fka Westside Villas IV) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Los Angeles, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 36      
Initial Cost to Company, Land $ 3,060,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 5,539,390      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,169,833      
Gross Amount Carried at close of period 12/31/2019, Land 3,060,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 6,709,223      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 9,769,223      
Accumulated Depreciation (4,174,963)      
Investment in Real Estate, Net 5,594,260      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Westside Villas (fka Westside Villas V &VII) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Los Angeles, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 113      
Initial Cost to Company, Land $ 9,605,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 19,983,385      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,834,458      
Gross Amount Carried at close of period 12/31/2019, Land 9,605,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 22,817,843      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 32,422,843      
Accumulated Depreciation (14,084,170)      
Investment in Real Estate, Net 18,338,673      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Windridge (CA) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Laguna Niguel, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 344      
Initial Cost to Company, Land $ 2,662,900      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 23,985,497      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 12,894,049      
Gross Amount Carried at close of period 12/31/2019, Land 2,662,900      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 36,879,546      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 39,542,446      
Accumulated Depreciation (29,263,863)      
Investment in Real Estate, Net 10,278,583      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Wood Creek I [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Pleasant Hill, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 256      
Initial Cost to Company, Land $ 9,729,900      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 23,009,768      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 10,186,943      
Gross Amount Carried at close of period 12/31/2019, Land 9,729,900      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 33,196,711      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 42,926,611      
Accumulated Depreciation (24,464,128)      
Investment in Real Estate, Net 18,462,483      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Woodleaf [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Campbell, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 178      
Initial Cost to Company, Land $ 8,550,600      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 16,988,183      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 5,276,931      
Gross Amount Carried at close of period 12/31/2019, Land 8,550,600      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 22,265,114      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 30,815,714      
Accumulated Depreciation (16,233,694)      
Investment in Real Estate, Net 14,582,020      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Management Business [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Chicago, IL      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 0      
Initial Cost to Company, Land $ 0      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 0      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 120,063,148      
Gross Amount Carried at close of period 12/31/2019, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 120,063,148      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 120,063,148      
Accumulated Depreciation (100,043,672)      
Investment in Real Estate, Net 20,019,476      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Operating Partnership [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Chicago, IL      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 0      
Initial Cost to Company, Land $ 0      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 3,342,110      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2019, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 3,342,110      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 3,342,110      
Accumulated Depreciation 0      
Investment in Real Estate, Net 3,342,110      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Other        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location N/A      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 0      
Initial Cost to Company, Land $ 0      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 0      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 99,015      
Gross Amount Carried at close of period 12/31/2019, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 99,015      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 99,015      
Accumulated Depreciation (46,097)      
Investment in Real Estate, Net 52,918      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Wholly Owned Unencumbered [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Units | ApartmentUnit 68,002      
Initial Cost to Company, Land $ 5,112,513,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 16,729,302,793      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,566,452,557      
Gross Amount Carried at close of period 12/31/2019, Land 5,112,513,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 18,295,755,350      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 23,408,268,350      
Accumulated Depreciation (6,199,955,243)      
Investment in Real Estate, Net 17,208,313,107      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
2501 Porter [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Washington, D.C.      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 202      
Initial Cost to Company, Land $ 13,000,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 75,271,179      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 6,881,392      
Gross Amount Carried at close of period 12/31/2019, Land 13,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 82,152,571      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 95,152,571      
Accumulated Depreciation (23,752,603)      
Investment in Real Estate, Net $ 71,399,968      
Real Estate And Accumulated Depreciation, Encumbrances Reference 0      
300 East 39th (fka East 39th) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location New York, NY      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 254      
Initial Cost to Company, Land $ 48,900,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 96,174,639      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 5,454,780      
Gross Amount Carried at close of period 12/31/2019, Land 48,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 101,629,419      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 150,529,419      
Accumulated Depreciation (29,129,896)      
Investment in Real Estate, Net 121,399,523      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 61,827,655      
303 East 83rd (fka Camargue) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location New York, NY      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 261      
Initial Cost to Company, Land $ 79,400,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 79,122,624      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 9,514,116      
Gross Amount Carried at close of period 12/31/2019, Land 79,400,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 88,636,740      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 168,036,740      
Accumulated Depreciation (25,938,650)      
Investment in Real Estate, Net $ 142,098,090      
Real Estate And Accumulated Depreciation, Encumbrances Reference 0      
425 Broadway [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Santa Monica, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 101      
Initial Cost to Company, Land $ 12,600,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 34,394,772      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,743,997      
Gross Amount Carried at close of period 12/31/2019, Land 12,600,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 38,138,769      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 50,738,769      
Accumulated Depreciation (11,169,257)      
Investment in Real Estate, Net $ 39,569,512      
Real Estate And Accumulated Depreciation, Encumbrances Reference 0      
55 West Fifth I & II (fka Townhouse Plaza and Gardens) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location San Mateo, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 241      
Initial Cost to Company, Land $ 21,041,710      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 71,931,323      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 13,813,466      
Gross Amount Carried at close of period 12/31/2019, Land 21,041,710      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 85,744,789      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 106,786,499      
Accumulated Depreciation (29,022,401)      
Investment in Real Estate, Net 77,764,098      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 24,527,815      
Alcyone [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Seattle, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 162      
Initial Cost to Company, Land $ 11,379,497      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 49,360,503      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,521,001      
Gross Amount Carried at close of period 12/31/2019, Land 11,379,497      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 50,881,504      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 62,261,001      
Accumulated Depreciation (11,900,832)      
Investment in Real Estate, Net 50,360,169      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 27,246,175      
Avanti [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Anaheim, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 162      
Initial Cost to Company, Land $ 12,960,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 18,497,683      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,104,266      
Gross Amount Carried at close of period 12/31/2019, Land 12,960,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 22,601,949      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 35,561,949      
Accumulated Depreciation (11,252,625)      
Investment in Real Estate, Net 24,309,324      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 28,015,078      
Avenir Apartments [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Boston, MA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 241      
Initial Cost to Company, Land $ 0      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 114,321,619      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 5,726,350      
Gross Amount Carried at close of period 12/31/2019, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 120,047,969      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 120,047,969      
Accumulated Depreciation (32,447,760)      
Investment in Real Estate, Net 87,600,209      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 85,443,736      
Calvert Woodley [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Washington, D.C.      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 136      
Initial Cost to Company, Land $ 12,600,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 43,527,379      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,412,100      
Gross Amount Carried at close of period 12/31/2019, Land 12,600,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 45,939,479      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 58,539,479      
Accumulated Depreciation (13,266,223)      
Investment in Real Estate, Net $ 45,273,256      
Real Estate And Accumulated Depreciation, Encumbrances Reference 0      
Chelsea Square [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Redmond, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 113      
Initial Cost to Company, Land $ 3,397,100      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 9,289,074      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,960,815      
Gross Amount Carried at close of period 12/31/2019, Land 3,397,100      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 12,249,889      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 15,646,989      
Accumulated Depreciation (8,780,971)      
Investment in Real Estate, Net 6,866,018      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 9,248,429      
Citrus Suites [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Santa Monica, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 70      
Initial Cost to Company, Land $ 9,000,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 16,950,326      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,141,605      
Gross Amount Carried at close of period 12/31/2019, Land 9,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 19,091,931      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 28,091,931      
Accumulated Depreciation (5,582,509)      
Investment in Real Estate, Net 22,509,422      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Cleveland House [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Washington, D.C.      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 214      
Initial Cost to Company, Land $ 18,300,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 66,392,414      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 5,509,932      
Gross Amount Carried at close of period 12/31/2019, Land 18,300,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 71,902,346      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 90,202,346      
Accumulated Depreciation (20,430,345)      
Investment in Real Estate, Net 69,772,001      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Columbia Crossing [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Arlington, VA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 247      
Initial Cost to Company, Land $ 23,500,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 53,045,073      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,113,933      
Gross Amount Carried at close of period 12/31/2019, Land 23,500,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 56,159,006      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 79,659,006      
Accumulated Depreciation (16,792,580)      
Investment in Real Estate, Net 62,866,426      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Elevé [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Glendale, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 208      
Initial Cost to Company, Land $ 14,080,560      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 56,419,440      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,010,321      
Gross Amount Carried at close of period 12/31/2019, Land 14,080,560      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 57,429,761      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 71,510,321      
Accumulated Depreciation (14,460,258)      
Investment in Real Estate, Net 57,050,063      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 38,356,888      
Estancia at Santa Clara (fka Santa Clara) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Santa Clara, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 450      
Initial Cost to Company, Land $ 0      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 123,759,804      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,914,108      
Gross Amount Carried at close of period 12/31/2019, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 125,673,912      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 125,673,912      
Accumulated Depreciation (36,538,855)      
Investment in Real Estate, Net 89,135,057      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Fairchase [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Fairfax, VA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 392      
Initial Cost to Company, Land $ 23,500,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 87,722,321      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,576,897      
Gross Amount Carried at close of period 12/31/2019, Land 23,500,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 89,299,218      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 112,799,218      
Accumulated Depreciation (24,613,974)      
Investment in Real Estate, Net 88,185,244      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Fairfield [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Stamford, CT      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 263      
Initial Cost to Company, Land $ 6,510,200      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 39,690,120      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 9,165,718      
Gross Amount Carried at close of period 12/31/2019, Land 6,510,200      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 48,855,838      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 55,366,038      
Accumulated Depreciation (36,158,521)      
Investment in Real Estate, Net 19,207,517      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 31,381,614      
Flats at DuPont Circle [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Washington, D.C.      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 306      
Initial Cost to Company, Land $ 35,200,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 108,768,198      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,181,605      
Gross Amount Carried at close of period 12/31/2019, Land 35,200,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 112,949,803      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 148,149,803      
Accumulated Depreciation (29,876,521)      
Investment in Real Estate, Net 118,273,282      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Glo [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Los Angeles, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 201      
Initial Cost to Company, Land $ 16,047,023      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 48,650,963      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,529,222      
Gross Amount Carried at close of period 12/31/2019, Land 16,047,023      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 52,180,185      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 68,227,208      
Accumulated Depreciation (17,906,742)      
Investment in Real Estate, Net 50,320,466      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 32,367,606      
Heights on Capitol Hill [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Seattle, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 104      
Initial Cost to Company, Land $ 5,425,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 21,138,028      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,887,584      
Gross Amount Carried at close of period 12/31/2019, Land 5,425,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 23,025,612      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 28,450,612      
Accumulated Depreciation (10,762,358)      
Investment in Real Estate, Net 17,688,254      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 22,562,286      
Kelvin Court (fka Alta Pacific) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Irvine, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 132      
Initial Cost to Company, Land $ 10,752,145      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 34,628,115      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 851,673      
Gross Amount Carried at close of period 12/31/2019, Land 10,752,145      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 35,479,788      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 46,231,933      
Accumulated Depreciation (14,415,041)      
Investment in Real Estate, Net 31,816,892      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 26,242,091      
La Terrazza at Colma Station [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Colma, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 155      
Initial Cost to Company, Land $ 0      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 41,251,044      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,207,542      
Gross Amount Carried at close of period 12/31/2019, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 44,458,586      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 44,458,586      
Accumulated Depreciation (19,788,954)      
Investment in Real Estate, Net 24,669,632      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 25,008,472      
Lofts 590 [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Arlington, VA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 212      
Initial Cost to Company, Land $ 20,100,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 67,909,023      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 785,733      
Gross Amount Carried at close of period 12/31/2019, Land 20,100,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 68,694,756      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 88,794,756      
Accumulated Depreciation (18,393,776)      
Investment in Real Estate, Net 70,400,980      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 42,942,461      
Longview Place [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Waltham, MA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 348      
Initial Cost to Company, Land $ 20,880,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 90,255,509      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 10,395,783      
Gross Amount Carried at close of period 12/31/2019, Land 20,880,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 100,651,292      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 121,531,292      
Accumulated Depreciation (49,137,968)      
Investment in Real Estate, Net 72,393,324      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 84,192,433      
Metro on First [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Seattle, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 102      
Initial Cost to Company, Land $ 8,540,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 12,209,981      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,455,932      
Gross Amount Carried at close of period 12/31/2019, Land 8,540,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 14,665,913      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 23,205,913      
Accumulated Depreciation (7,193,891)      
Investment in Real Estate, Net 16,012,022      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 21,468,471      
Moda [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Seattle, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 251      
Initial Cost to Company, Land $ 12,649,228      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 36,842,012      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,903,142      
Gross Amount Carried at close of period 12/31/2019, Land 12,649,228      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 38,745,154      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 51,394,382      
Accumulated Depreciation (14,892,031)      
Investment in Real Estate, Net 36,502,351      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Park Place at San Mateo (fka San Mateo) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location San Mateo, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 575      
Initial Cost to Company, Land $ 71,900,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 211,907,141      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 13,628,927      
Gross Amount Carried at close of period 12/31/2019, Land 71,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 225,536,068      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 297,436,068      
Accumulated Depreciation (64,679,195)      
Investment in Real Estate, Net $ 232,756,873      
Real Estate And Accumulated Depreciation, Encumbrances Reference 0      
SoMa Square Apartments (fka South Market) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location San Francisco, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 410      
Initial Cost to Company, Land $ 79,900,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 177,316,977      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 15,704,742      
Gross Amount Carried at close of period 12/31/2019, Land 79,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 193,021,719      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 272,921,719      
Accumulated Depreciation (52,889,334)      
Investment in Real Estate, Net $ 220,032,385      
Real Estate And Accumulated Depreciation, Encumbrances Reference 0      
Square One [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Seattle, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 112      
Initial Cost to Company, Land $ 7,222,544      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 26,277,456      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 99,319      
Gross Amount Carried at close of period 12/31/2019, Land 7,222,544      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 26,376,775      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 33,599,319      
Accumulated Depreciation (6,486,674)      
Investment in Real Estate, Net $ 27,112,645      
Real Estate And Accumulated Depreciation, Encumbrances Reference 0      
Teresina [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Chula Vista, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 440      
Initial Cost to Company, Land $ 28,600,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 61,916,670      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 7,609,660      
Gross Amount Carried at close of period 12/31/2019, Land 28,600,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 69,526,330      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 98,126,330      
Accumulated Depreciation (34,235,450)      
Investment in Real Estate, Net 63,890,880      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 37,940,000      
Vantage Hollywood [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Los Angeles, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 298      
Initial Cost to Company, Land $ 42,580,326      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 56,014,674      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,850,265      
Gross Amount Carried at close of period 12/31/2019, Land 42,580,326      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 58,864,939      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 101,445,265      
Accumulated Depreciation (13,149,796)      
Investment in Real Estate, Net 88,295,469      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 39,550,471      
Vintage [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Ontario, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 300      
Initial Cost to Company, Land $ 7,059,230      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 47,677,762      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,742,159      
Gross Amount Carried at close of period 12/31/2019, Land 7,059,230      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 49,419,921      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 56,479,151      
Accumulated Depreciation (23,528,467)      
Investment in Real Estate, Net 32,950,684      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 49,085,671      
Vintage at 425 Broadway (fka Promenade) [Memebr]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Santa Monica, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 60      
Initial Cost to Company, Land $ 9,000,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 13,961,523      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,918,439      
Gross Amount Carried at close of period 12/31/2019, Land 9,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 15,879,962      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 24,879,962      
Accumulated Depreciation (4,816,090)      
Investment in Real Estate, Net $ 20,063,872      
Real Estate And Accumulated Depreciation, Encumbrances Reference 0      
West 54th [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location New York, NY      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 222      
Initial Cost to Company, Land $ 60,900,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 48,193,837      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,230,586      
Gross Amount Carried at close of period 12/31/2019, Land 60,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 52,424,423      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 113,324,423      
Accumulated Depreciation (16,852,716)      
Investment in Real Estate, Net 96,471,707      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 48,684,032      
Westgate (fka Westgate I) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Pasadena, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 480      
Initial Cost to Company, Land $ 22,898,848      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 133,467,158      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,178,513      
Gross Amount Carried at close of period 12/31/2019, Land 22,898,848      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 136,645,671      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 159,544,519      
Accumulated Depreciation (42,104,815)      
Investment in Real Estate, Net 117,439,704      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 96,409,896      
Portfolio/Entity Encumbrances [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Units | ApartmentUnit 0      
Initial Cost to Company, Land $ 0      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 0      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2019, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 0      
Accumulated Depreciation 0      
Investment in Real Estate, Net 0      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 798,230,171      
Investment in Real Estate - Wholly Owned Encumbered [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Units | ApartmentUnit 8,425      
Initial Cost to Company, Land $ 769,823,411      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 2,274,256,364      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 160,725,623      
Gross Amount Carried at close of period 12/31/2019, Land 769,823,411      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 2,434,981,987      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 3,204,805,398      
Accumulated Depreciation (792,348,079)      
Investment in Real Estate, Net 2,412,457,319      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 1,630,731,451      
2300 Elliott [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Seattle, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 92      
Initial Cost to Company, Land $ 796,800      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 7,173,725      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 7,612,428      
Gross Amount Carried at close of period 12/31/2019, Land 796,800      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 14,786,153      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 15,582,953      
Accumulated Depreciation (11,840,195)      
Investment in Real Estate, Net 3,742,758      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
A9th & W [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Washington, DC      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 0      
Initial Cost to Company, Land $ 0      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 3,566,064      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2019, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 3,566,064      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 3,566,064      
Accumulated Depreciation 0      
Investment in Real Estate, Net 3,566,064      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Canyon Ridge [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location San Diego, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 162      
Initial Cost to Company, Land $ 4,869,448      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 11,955,064      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,156,380      
Gross Amount Carried at close of period 12/31/2019, Land 4,869,448      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 16,111,444      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 20,980,892      
Accumulated Depreciation (11,815,991)      
Investment in Real Estate, Net 9,164,901      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Country Oaks [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Agoura Hills, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 256      
Initial Cost to Company, Land $ 6,105,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 29,561,865      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 7,265,339      
Gross Amount Carried at close of period 12/31/2019, Land 6,105,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 36,827,204      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 42,932,204      
Accumulated Depreciation (22,480,257)      
Investment in Real Estate, Net 20,451,947      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Harrison Square (fka Elliot Bay) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Seattle, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 166      
Initial Cost to Company, Land $ 7,600,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 35,844,345      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 5,653,924      
Gross Amount Carried at close of period 12/31/2019, Land 7,600,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 41,498,269      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 49,098,269      
Accumulated Depreciation (12,916,108)      
Investment in Real Estate, Net 36,182,161      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Radius Koreatown [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Los Angeles, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 301      
Initial Cost to Company, Land $ 32,494,154      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 84,645,202      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 276,918      
Gross Amount Carried at close of period 12/31/2019, Land 32,494,154      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 84,922,120      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 117,416,274      
Accumulated Depreciation (11,662,625)      
Investment in Real Estate, Net 105,753,649      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Rosecliff [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Quincy, MA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 156      
Initial Cost to Company, Land $ 5,460,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 15,721,570      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,373,677      
Gross Amount Carried at close of period 12/31/2019, Land 5,460,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 20,095,247      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 25,555,247      
Accumulated Depreciation (13,904,866)      
Investment in Real Estate, Net 11,650,381      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Strayhorse at Arrowhead Ranch [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Glendale, AZ      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 136      
Initial Cost to Company, Land $ 4,400,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 12,968,001      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,162,489      
Gross Amount Carried at close of period 12/31/2019, Land 4,400,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 14,130,490      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 18,530,490      
Accumulated Depreciation (7,106,675)      
Investment in Real Estate, Net 11,423,815      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Venn at Main [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Bellevue, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 350      
Initial Cost to Company, Land $ 26,626,497      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 151,652,048      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 226,783      
Gross Amount Carried at close of period 12/31/2019, Land 26,626,497      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 151,878,831      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 178,505,328      
Accumulated Depreciation (15,894,448)      
Investment in Real Estate, Net 162,610,880      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Wood Creek II (fka Willow Brook (CA)) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Pleasant Hill, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 228      
Initial Cost to Company, Land $ 5,055,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 38,388,672      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 9,286,416      
Gross Amount Carried at close of period 12/31/2019, Land 5,055,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 47,675,088      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 52,730,088      
Accumulated Depreciation (25,490,323)      
Investment in Real Estate, Net 27,239,765      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Partially Owned Unencumbered [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Units | ApartmentUnit 1,847      
Initial Cost to Company, Land $ 93,406,899      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 391,476,556      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 40,014,354      
Gross Amount Carried at close of period 12/31/2019, Land 93,406,899      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 431,490,910      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 524,897,809      
Accumulated Depreciation (133,111,488)      
Investment in Real Estate, Net 391,786,321      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Aero Apartments [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Alameda, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 0      
Initial Cost to Company, Land $ 13,107,242      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 18,347,948      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2019, Land 13,107,242      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 18,347,948      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 31,455,190      
Accumulated Depreciation 0      
Investment in Real Estate, Net 31,455,190      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 7,049,636      
Bellevue Meadows [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Bellevue, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 180      
Initial Cost to Company, Land $ 4,507,100      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 12,574,814      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 5,863,119      
Gross Amount Carried at close of period 12/31/2019, Land 4,507,100      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 18,437,933      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 22,945,033      
Accumulated Depreciation (13,949,169)      
Investment in Real Estate, Net 8,995,864      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 16,526,976      
Canyon Creek (CA) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location San Ramon, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 268      
Initial Cost to Company, Land $ 5,425,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 18,812,120      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 7,911,730      
Gross Amount Carried at close of period 12/31/2019, Land 5,425,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 26,723,850      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 32,148,850      
Accumulated Depreciation (18,327,786)      
Investment in Real Estate, Net 13,821,064      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 28,171,906      
Lantern Cove [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Foster City, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 232      
Initial Cost to Company, Land $ 6,945,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 23,064,976      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 7,320,624      
Gross Amount Carried at close of period 12/31/2019, Land 6,945,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 30,385,600      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 37,330,600      
Accumulated Depreciation (19,807,488)      
Investment in Real Estate, Net 17,523,112      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 36,439,783      
Schooner Bay I [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Foster City, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 168      
Initial Cost to Company, Land $ 5,345,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 20,390,618      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 5,854,156      
Gross Amount Carried at close of period 12/31/2019, Land 5,345,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 26,244,774      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 31,589,774      
Accumulated Depreciation (17,054,268)      
Investment in Real Estate, Net 14,535,506      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 28,854,243      
Schooner Bay II [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Foster City, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 144      
Initial Cost to Company, Land $ 4,550,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 18,064,764      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 5,376,714      
Gross Amount Carried at close of period 12/31/2019, Land 4,550,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 23,441,478      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 27,991,478      
Accumulated Depreciation (15,168,558)      
Investment in Real Estate, Net 12,822,920      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 26,159,132      
Surrey Downs [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Bellevue, WA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 122      
Initial Cost to Company, Land $ 3,057,100      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 7,848,618      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,532,712      
Gross Amount Carried at close of period 12/31/2019, Land 3,057,100      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 11,381,330      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 14,438,430      
Accumulated Depreciation (8,356,388)      
Investment in Real Estate, Net 6,082,042      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 9,829,000      
Virgil Square [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Los Angeles, CA      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 142      
Initial Cost to Company, Land $ 5,500,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 15,216,613      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,380,225      
Gross Amount Carried at close of period 12/31/2019, Land 5,500,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 18,596,838      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 24,096,838      
Accumulated Depreciation (10,021,205)      
Investment in Real Estate, Net 14,075,633      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 9,893,916      
Wisconsin Place [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Chevy Chase, MD      
Real Estate And Accumulated Depreciation Units | ApartmentUnit 432      
Initial Cost to Company, Land $ 0      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 172,089,355      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,550,321      
Gross Amount Carried at close of period 12/31/2019, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 173,639,676      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 173,639,676      
Accumulated Depreciation (48,686,702)      
Investment in Real Estate, Net 124,952,974      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 147,953,509      
Partially Owned Encumbered [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Units | ApartmentUnit 1,688      
Initial Cost to Company, Land $ 48,436,442      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 306,409,826      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 40,789,601      
Gross Amount Carried at close of period 12/31/2019, Land 48,436,442      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 347,199,427      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 395,635,869      
Accumulated Depreciation (151,371,564)      
Investment in Real Estate, Net 244,264,305      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 310,878,101      
Total Consolidated Investment in Real Estate [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Units | ApartmentUnit 79,962      
Initial Cost to Company, Land $ 6,024,179,752      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 19,701,445,539      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,807,982,135      
Gross Amount Carried at close of period 12/31/2019, Land 6,024,179,752      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 21,509,427,674      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 27,533,607,426      
Accumulated Depreciation (7,276,786,374)      
Investment in Real Estate, Net 20,256,821,052      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 1,941,609,552