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Real Estate and Accumulated Depreciation (Details)
 12 Months Ended
Dec. 31, 2016
USD ($)
Dec. 31, 2015
USD ($)
Dec. 31, 2014
USD ($)
Dec. 31, 2013
USD ($)
Real Estate and Accumulated Depreciation [Line Items]        
Furniture, fixtures and equipment $ 1,346,300,000 $ 1,207,098,000    
Land And Depreciable Property Net 15,800,000,000 17,000,000,000    
Real Estate And Accumulated Depreciation Abstract        
Accumulated Depreciation $ (5,360,389,000) $ (6,084,616,000) $ (5,432,805,000) $ (4,807,709,000)
Partially Owned Properties 302      
Apartment Units 77,458      
100 K 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 0      
Initial Cost to Company, Land $ 15,600,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 10,782,320      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2016, Land 15,600,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 10,782,320      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 26,382,320      
Accumulated Depreciation 0      
Investment in Real Estate Net 26,382,320      
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 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 6,750,405      
Gross Amount Carried at close of period 12/31/2016, Land 103,539,100      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 100,833,130      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 204,372,230      
Accumulated Depreciation (41,010,422)      
Investment in Real Estate Net 163,361,808      
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 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 12,780,175      
Gross Amount Carried at close of period 12/31/2016, Land 139,933,500      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 203,744,920      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 343,678,420      
Accumulated Depreciation (81,836,307)      
Investment in Real Estate Net 261,842,113      
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 236      
Initial Cost to Company, Land $ 0      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 111,872,438      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 60,750      
Gross Amount Carried at close of period 12/31/2016, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 111,933,188      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 111,933,188      
Accumulated Depreciation (7,014,736)      
Investment in Real Estate Net 104,918,452      
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 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 1,396,338      
Gross Amount Carried at close of period 12/31/2016, Land 22,037,831      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 55,358,507      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 77,396,338      
Accumulated Depreciation (12,584,288)      
Investment in Real Estate Net 64,812,050      
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 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 2,910,862      
Gross Amount Carried at close of period 12/31/2016, Land 32,400,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 95,586,090      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 127,986,090      
Accumulated Depreciation (16,638,099)      
Investment in Real Estate Net 111,347,991      
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 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 11,344,206      
Gross Amount Carried at close of period 12/31/2016, Land 144,968,250      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 149,690,887      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 294,659,137      
Accumulated Depreciation (61,661,842)      
Investment in Real Estate Net 232,997,295      
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 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 101,850      
Gross Amount Carried at close of period 12/31/2016, Land 18,937,702      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 94,860,529      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 113,798,231      
Accumulated Depreciation (12,803,962)      
Investment in Real Estate Net 100,994,269      
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 144      
Initial Cost to Company, Land $ 9,213,513      
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 2,112,056      
Gross Amount Carried at close of period 12/31/2016, Land 9,213,513      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 38,671,245      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 47,884,758      
Accumulated Depreciation (15,416,324)      
Investment in Real Estate Net 32,468,434      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
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 0      
Initial Cost to Company, Land $ 10,401,958      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 4,932,954      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2016, Land 10,401,958      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 4,932,954      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 15,334,912      
Accumulated Depreciation 0      
Investment in Real Estate Net 15,334,912      
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 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 14,505,801      
Gross Amount Carried at close of period 12/31/2016, Land 54,638,298      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 54,867,503      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 109,505,801      
Accumulated Depreciation (21,697,139)      
Investment in Real Estate Net 87,808,662      
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 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 2,999,587      
Gross Amount Carried at close of period 12/31/2016, Land 31,400,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 112,005,321      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 143,405,321      
Accumulated Depreciation (19,795,492)      
Investment in Real Estate Net 123,609,829      
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 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 2,103,036      
Gross Amount Carried at close of period 12/31/2016, Land 11,321,198      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 51,777,211      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 63,098,409      
Accumulated Depreciation (9,394,581)      
Investment in Real Estate Net 53,703,828      
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 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 2,390,730      
Gross Amount Carried at close of period 12/31/2016, Land 21,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 81,115,393      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 103,015,393      
Accumulated Depreciation (13,936,506)      
Investment in Real Estate Net 89,078,887      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
M St 2400 [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Washington, D.C.      
Real Estate And Accumulated Depreciation Units 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 4,082,076      
Gross Amount Carried at close of period 12/31/2016, Land 30,006,593      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 118,095,861      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 148,102,454      
Accumulated Depreciation (45,418,266)      
Investment in Real Estate Net 102,684,188      
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 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 517,562      
Gross Amount Carried at close of period 12/31/2016, Land 14,450,070      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 116,342,492      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 130,792,562      
Accumulated Depreciation (10,319,919)      
Investment in Real Estate Net 120,472,643      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
340 Fremont [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location San Francisco, CA      
Real Estate And Accumulated Depreciation Units 348      
Initial Cost to Company, Land $ 42,000,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 244,995,446      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 88      
Gross Amount Carried at close of period 12/31/2016, Land 42,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 244,995,534      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 286,995,534      
Accumulated Depreciation (4,611,169)      
Investment in Real Estate Net 282,384,365      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
3003 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 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 4,018,369      
Gross Amount Carried at close of period 12/31/2016, Land 56,300,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 145,209,949      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 201,509,949      
Accumulated Depreciation (27,557,126)      
Investment in Real Estate Net 173,952,823      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
45 Worthington [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Boston, MA      
Real Estate And Accumulated Depreciation Units 0      
Initial Cost to Company, Land $ 0      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 2,058,673      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2016, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 2,058,673      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 2,058,673      
Accumulated Depreciation 0      
Investment in Real Estate Net 2,058,673      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
420 East 80th 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 155      
Initial Cost to Company, Land $ 39,277,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 23,026,984      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,252,598      
Gross Amount Carried at close of period 12/31/2016, Land 39,277,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 27,279,582      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 66,556,582      
Accumulated Depreciation (12,559,376)      
Investment in Real Estate Net 53,997,206      
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 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 3,740,413      
Gross Amount Carried at close of period 12/31/2016, Land 28,150,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 142,340,413      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 170,490,413      
Accumulated Depreciation (39,542,039)      
Investment in Real Estate Net 130,948,374      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
455 I 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 0      
Initial Cost to Company, Land $ 12,762,857      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 45,794,997      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2016, Land 12,762,857      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 45,794,997      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 58,557,854      
Accumulated Depreciation 0      
Investment in Real Estate Net 58,557,854      
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 0      
Initial Cost to Company, Land $ 0      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 1,237,673      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2016, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 1,237,673      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 1,237,673      
Accumulated Depreciation 0      
Investment in Real Estate Net 1,237,673      
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 0      
Initial Cost to Company, Land $ 13,131,456      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 11,144,682      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2016, Land 13,131,456      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 11,144,682      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 24,276,138      
Accumulated Depreciation 0      
Investment in Real Estate Net 24,276,138      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
660 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 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 734,411      
Gross Amount Carried at close of period 12/31/2016, Land 32,852,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 43,874,962      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 76,726,962      
Accumulated Depreciation (17,905,409)      
Investment in Real Estate Net 58,821,553      
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 Boston, MA      
Real Estate And Accumulated Depreciation Units 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 2,325,428      
Gross Amount Carried at close of period 12/31/2016, Land 106,100,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 168,637,107      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 274,737,107      
Accumulated Depreciation (29,635,573)      
Investment in Real Estate Net 245,101,534      
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 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 1,103,051      
Gross Amount Carried at close of period 12/31/2016, Land 28,108,899      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 237,866,604      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 265,975,503      
Accumulated Depreciation (57,907,087)      
Investment in Real Estate Net 208,068,416      
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 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 12,799,538      
Gross Amount Carried at close of period 12/31/2016, Land 22,611,600      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 90,291,709      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 112,903,309      
Accumulated Depreciation (39,723,414)      
Investment in Real Estate Net 73,179,895      
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 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 264,502      
Gross Amount Carried at close of period 12/31/2016, Land 5,249,124      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 18,874,378      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 24,123,502      
Accumulated Depreciation (4,400,965)      
Investment in Real Estate Net 19,722,537      
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 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 5,319,200      
Gross Amount Carried at close of period 12/31/2016, Land 27,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 174,311,640      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 202,211,640      
Accumulated Depreciation (28,587,488)      
Investment in Real Estate Net 173,624,152      
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 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 1,975,718      
Gross Amount Carried at close of period 12/31/2016, Land 65,352,706      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 67,723,012      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 133,075,718      
Accumulated Depreciation (24,056,905)      
Investment in Real Estate Net 109,018,813      
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 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 1,965,143      
Gross Amount Carried at close of period 12/31/2016, Land 7,786,800      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 33,552,468      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 41,339,268      
Accumulated Depreciation (7,400,305)      
Investment in Real Estate Net 33,938,963      
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 0      
Initial Cost to Company, Land $ 41,363,921      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 166,903,627      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2016, Land 41,363,921      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 166,903,627      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 208,267,548      
Accumulated Depreciation 0      
Investment in Real Estate Net 208,267,548      
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 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 199,531      
Gross Amount Carried at close of period 12/31/2016, Land 5,550,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 15,985,040      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 21,535,040      
Accumulated Depreciation (6,078,896)      
Investment in Real Estate Net 15,456,144      
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 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 1,712,897      
Gross Amount Carried at close of period 12/31/2016, Land 18,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 91,507,098      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 110,407,098      
Accumulated Depreciation (15,639,767)      
Investment in Real Estate Net 94,767,331      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Altitude [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Los Angeles, CA      
Real Estate And Accumulated Depreciation Units 545      
Initial Cost to Company, Land $ 43,783,485      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 147,918,661      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 25,744      
Gross Amount Carried at close of period 12/31/2016, Land 43,783,485      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 147,944,405      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 191,727,890      
Accumulated Depreciation (2,490,933)      
Investment in Real Estate Net 189,236,957      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Alton, The [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Irvine, CA      
Real Estate And Accumulated Depreciation Units 0      
Initial Cost to Company, Land $ 11,049,027      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 90,857,975      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2016, Land 11,049,027      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 90,857,975      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 101,907,002      
Accumulated Depreciation 0      
Investment in Real Estate Net 101,907,002      
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 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 4,162,140      
Gross Amount Carried at close of period 12/31/2016, Land 9,057,300      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 22,645,782      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 31,703,082      
Accumulated Depreciation (13,943,284)      
Investment in Real Estate Net 17,759,798      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Artech Building [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Berkeley, CA      
Real Estate And Accumulated Depreciation Units 27      
Initial Cost to Company, Land $ 1,642,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 9,152,518      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 329,292      
Gross Amount Carried at close of period 12/31/2016, Land 1,642,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 9,481,810      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 11,123,810      
Accumulated Depreciation (3,371,389)      
Investment in Real Estate Net 7,752,421      
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 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 670,299      
Gross Amount Carried at close of period 12/31/2016, Land 8,000,400      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 36,744,899      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 44,745,299      
Accumulated Depreciation (9,258,909)      
Investment in Real Estate Net 35,486,390      
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 261      
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 2,277,634      
Gross Amount Carried at close of period 12/31/2016, Land 12,300,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 63,743,901      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 76,043,901      
Accumulated Depreciation (12,191,117)      
Investment in Real Estate Net 63,852,784      
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 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 90,854      
Gross Amount Carried at close of period 12/31/2016, Land 32,401,680      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 47,226,286      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 79,627,966      
Accumulated Depreciation (3,149,449)      
Investment in Real Estate Net 76,478,517      
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 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 1,749,322      
Gross Amount Carried at close of period 12/31/2016, Land 7,995,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 19,754,322      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 27,749,322      
Accumulated Depreciation (5,134,751)      
Investment in Real Estate Net 22,614,571      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Azure [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location San Francisco, CA      
Real Estate And Accumulated Depreciation Units 273      
Initial Cost to Company, Land $ 32,855,115      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 152,254,155      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 26,494      
Gross Amount Carried at close of period 12/31/2016, Land 32,855,115      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 152,280,649      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 185,135,764      
Accumulated Depreciation (7,791,579)      
Investment in Real Estate Net 177,344,185      
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 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 2,909,175      
Gross Amount Carried at close of period 12/31/2016, Land 7,600,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 30,346,414      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 37,946,414      
Accumulated Depreciation (13,103,323)      
Investment in Real Estate Net 24,843,091      
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 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 1,000,140      
Gross Amount Carried at close of period 12/31/2016, Land 114,351,405      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 166,648,735      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 281,000,140      
Accumulated Depreciation (35,148,328)      
Investment in Real Estate Net 245,851,812      
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 1      
Initial Cost to Company, Land $ 63,158      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 248,928      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures (5,320)      
Gross Amount Carried at close of period 12/31/2016, Land 63,158      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 243,608      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 306,766      
Accumulated Depreciation 0      
Investment in Real Estate Net 306,766      
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 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 683,777      
Gross Amount Carried at close of period 12/31/2016, Land 9,098,808      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 29,384,969      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 38,483,777      
Accumulated Depreciation (6,820,566)      
Investment in Real Estate Net 31,663,211      
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 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 1,050,136      
Gross Amount Carried at close of period 12/31/2016, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 74,239,398      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 74,239,398      
Accumulated Depreciation (14,067,543)      
Investment in Real Estate Net 60,171,855      
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 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 3,599,062      
Gross Amount Carried at close of period 12/31/2016, Land 9,991,500      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 25,846,340      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 35,837,840      
Accumulated Depreciation (15,933,244)      
Investment in Real Estate Net 19,904,596      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Bridford Lakes Two [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Greensboro, NC      
Real Estate And Accumulated Depreciation Units 0      
Initial Cost to Company, Land $ 1,100,564      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 792,508      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2016, Land 1,100,564      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 792,508      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 1,893,072      
Accumulated Depreciation 0      
Investment in Real Estate Net 1,893,072      
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 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 1,827,017      
Gross Amount Carried at close of period 12/31/2016, Land 40,099,922      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 223,265,648      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 263,365,570      
Accumulated Depreciation (46,337,376)      
Investment in Real Estate Net 217,028,194      
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 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 7,841      
Gross Amount Carried at close of period 12/31/2016, Land 17,125,766      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 28,082,075      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 45,207,841      
Accumulated Depreciation (978,707)      
Investment in Real Estate Net 44,229,134      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Cambridge Park [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Cambridge, MA      
Real Estate And Accumulated Depreciation Units 312      
Initial Cost to Company, Land $ 31,200,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 106,048,587      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,107,045      
Gross Amount Carried at close of period 12/31/2016, Land 31,200,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 110,155,632      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 141,355,632      
Accumulated Depreciation (19,695,291)      
Investment in Real Estate Net 121,660,341      
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 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 7,872,672      
Gross Amount Carried at close of period 12/31/2016, Land 10,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 59,240,585      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 69,240,585      
Accumulated Depreciation (28,386,923)      
Investment in Real Estate Net 40,853,662      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Cascade [Domain]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Seattle, WA      
Real Estate And Accumulated Depreciation Units 0      
Initial Cost to Company, Land $ 23,751,564      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 99,710,750      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2016, Land 23,751,564      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 99,710,750      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 123,462,314      
Accumulated Depreciation 0      
Investment in Real Estate Net 123,462,314      
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 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 10,056,055      
Gross Amount Carried at close of period 12/31/2016, Land 9,700,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 80,136,433      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 89,836,433      
Accumulated Depreciation (33,705,547)      
Investment in Real Estate Net 56,130,886      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Centre Club [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Ontario, CA      
Real Estate And Accumulated Depreciation Units 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 7,413,964      
Gross Amount Carried at close of period 12/31/2016, Land 7,436,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 40,428,753      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 47,864,753      
Accumulated Depreciation (21,574,006)      
Investment in Real Estate Net 26,290,747      
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 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 2,266,923      
Gross Amount Carried at close of period 12/31/2016, Land 5,220,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 19,011,566      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 24,231,566      
Accumulated Depreciation (8,540,355)      
Investment in Real Estate Net 15,691,211      
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 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 5,626,705      
Gross Amount Carried at close of period 12/31/2016, Land 40,400,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 101,563,751      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 141,963,751      
Accumulated Depreciation (17,548,498)      
Investment in Real Estate Net 124,415,253      
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 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 857,946      
Gross Amount Carried at close of period 12/31/2016, Land 6,863,792      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 37,334,154      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 44,197,946      
Accumulated Depreciation (11,712,818)      
Investment in Real Estate Net 32,485,128      
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 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 3,126,524      
Gross Amount Carried at close of period 12/31/2016, Land 15,100,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 45,002,781      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 60,102,781      
Accumulated Depreciation (7,953,824)      
Investment in Real Estate Net 52,148,957      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
CityView at Longwood [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Boston, MA      
Real Estate And Accumulated Depreciation Units 295      
Initial Cost to Company, Land $ 14,704,898      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 79,195,102      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 10,574,412      
Gross Amount Carried at close of period 12/31/2016, Land 14,704,898      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 89,769,514      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 104,474,412      
Accumulated Depreciation (25,961,856)      
Investment in Real Estate Net 78,512,556      
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 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 2,143,113      
Gross Amount Carried at close of period 12/31/2016, Land 30,400,340      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 105,967,773      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 136,368,113      
Accumulated Depreciation (26,624,877)      
Investment in Real Estate Net 109,743,236      
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 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 3,832,717      
Gross Amount Carried at close of period 12/31/2016, Land 6,615,467      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 18,662,052      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 25,277,519      
Accumulated Depreciation (8,171,402)      
Investment in Real Estate Net 17,106,117      
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 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 4,856,602      
Gross Amount Carried at close of period 12/31/2016, Land 27,600,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 118,858,897      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 146,458,897      
Accumulated Depreciation (20,124,977)      
Investment in Real Estate Net 126,333,920      
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 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 1,796,515      
Gross Amount Carried at close of period 12/31/2016, Land 13,500,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 28,709,628      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 42,209,628      
Accumulated Depreciation (5,801,661)      
Investment in Real Estate Net 36,407,967      
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 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 4,635,703      
Gross Amount Carried at close of period 12/31/2016, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 92,021,727      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 92,021,727      
Accumulated Depreciation (17,966,254)      
Investment in Real Estate Net 74,055,473      
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 192      
Initial Cost to Company, Land $ 9,606,600      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 21,193,231      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,013,129      
Gross Amount Carried at close of period 12/31/2016, Land 9,606,600      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 25,206,360      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 34,812,960      
Accumulated Depreciation (15,771,922)      
Investment in Real Estate Net 19,041,038      
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 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 3,914,279      
Gross Amount Carried at close of period 12/31/2016, Land 32,300,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 89,033,603      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 121,333,603      
Accumulated Depreciation (15,979,321)      
Investment in Real Estate Net 105,354,282      
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 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 3,157,515      
Gross Amount Carried at close of period 12/31/2016, Land 17,200,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 51,076,490      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 68,276,490      
Accumulated Depreciation (9,260,208)      
Investment in Real Estate Net 59,016,282      
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 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 8,800,432      
Gross Amount Carried at close of period 12/31/2016, Land 1,808,900      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 25,074,793      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 26,883,693      
Accumulated Depreciation (17,314,590)      
Investment in Real Estate Net 9,569,103      
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 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 1,125,457      
Gross Amount Carried at close of period 12/31/2016, Land 13,092,552      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 45,032,905      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 58,125,457      
Accumulated Depreciation (10,423,583)      
Investment in Real Estate Net 47,701,874      
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 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 415,204      
Gross Amount Carried at close of period 12/31/2016, Land 14,080,560      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 56,834,644      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 70,915,204      
Accumulated Depreciation (7,584,216)      
Investment in Real Estate Net 63,330,988      
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 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 22,690,975      
Gross Amount Carried at close of period 12/31/2016, Land 14,855,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 80,257,611      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 95,112,611      
Accumulated Depreciation (52,167,424)      
Investment in Real Estate Net 42,945,187      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Encinitas Heights (fka Encinitas) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Encinitas, CA      
Real Estate And Accumulated Depreciation Units 120      
Initial Cost to Company, Land $ 12,000,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 29,207,497      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 617,199      
Gross Amount Carried at close of period 12/31/2016, Land 12,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 29,824,696      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 41,824,696      
Accumulated Depreciation (5,889,783)      
Investment in Real Estate Net 35,934,913      
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 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 1,211,820      
Gross Amount Carried at close of period 12/31/2016, Land 8,700,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 26,657,823      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 35,357,823      
Accumulated Depreciation (7,869,084)      
Investment in Real Estate Net 27,488,739      
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 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 927,144      
Gross Amount Carried at close of period 12/31/2016, Land 25,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 84,913,361      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 110,813,361      
Accumulated Depreciation (15,751,998)      
Investment in Real Estate Net 95,061,363      
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 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 2,733,097      
Gross Amount Carried at close of period 12/31/2016, Land 25,800,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 81,486,211      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 107,286,211      
Accumulated Depreciation (14,742,488)      
Investment in Real Estate Net 92,543,723      
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 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 2,651,435      
Gross Amount Carried at close of period 12/31/2016, Land 18,144,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 49,219,376      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 67,363,376      
Accumulated Depreciation (19,871,531)      
Investment in Real Estate Net 47,491,845      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Garden Garage [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Boston, MA      
Real Estate And Accumulated Depreciation Units 0      
Initial Cost to Company, Land $ 0      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 4,917,373      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2016, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 4,917,373      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 4,917,373      
Accumulated Depreciation 0      
Investment in Real Estate Net 4,917,373      
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 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 13,834,746      
Gross Amount Carried at close of period 12/31/2016, Land 9,209,780      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 39,557,412      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 48,767,192      
Accumulated Depreciation (21,301,983)      
Investment in Real Estate Net 27,465,209      
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 164      
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 4,477,710      
Gross Amount Carried at close of period 12/31/2016, Land 1,722,400      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 19,949,139      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 21,671,539      
Accumulated Depreciation (12,574,169)      
Investment in Real Estate Net 9,097,370      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Glen Meadow [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Franklin, MA      
Real Estate And Accumulated Depreciation Units 288      
Initial Cost to Company, Land $ 2,339,331      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 16,133,588      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,347,422      
Gross Amount Carried at close of period 12/31/2016, Land 2,339,331      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 20,481,010      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 22,820,341      
Accumulated Depreciation (12,813,162)      
Investment in Real Estate Net 10,007,179      
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 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 4,042,761      
Gross Amount Carried at close of period 12/31/2016, Land 10,806,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 34,378,091      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 45,184,091      
Accumulated Depreciation (15,493,262)      
Investment in Real Estate Net 29,690,829      
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 758      
Initial Cost to Company, Land $ 59,387,158      
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 20,957,019      
Gross Amount Carried at close of period 12/31/2016, Land 59,387,158      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 179,786,451      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 239,173,609      
Accumulated Depreciation (73,216,856)      
Investment in Real Estate Net 165,956,753      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Helios/1610 2nd Avenue [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Seattle, WA      
Real Estate And Accumulated Depreciation Units 0      
Initial Cost to Company, Land $ 18,061,674      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 162,443,822      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2016, Land 18,061,674      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 162,443,822      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 180,505,496      
Accumulated Depreciation 0      
Investment in Real Estate Net 180,505,496      
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 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 1,839,852      
Gross Amount Carried at close of period 12/31/2016, Land 10,800,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 33,648,187      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 44,448,187      
Accumulated Depreciation (14,133,220)      
Investment in Real Estate Net 30,314,967      
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 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 1,741,466      
Gross Amount Carried at close of period 12/31/2016, Land 6,895,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 20,725,063      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 27,620,063      
Accumulated Depreciation (9,305,589)      
Investment in Real Estate Net 18,314,474      
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 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 323,337      
Gross Amount Carried at close of period 12/31/2016, Land 23,299,892      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 103,023,445      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 126,323,337      
Accumulated Depreciation (13,208,612)      
Investment in Real Estate Net 113,114,725      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Highlands at Cherry Hill [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Cherry Hills, NJ      
Real Estate And Accumulated Depreciation Units 170      
Initial Cost to Company, Land $ 6,800,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 21,459,108      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,219,837      
Gross Amount Carried at close of period 12/31/2016, Land 6,800,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 22,678,945      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 29,478,945      
Accumulated Depreciation (9,622,596)      
Investment in Real Estate Net 19,856,349      
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 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 1,671,208      
Gross Amount Carried at close of period 12/31/2016, Land 10,080,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 39,198,120      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 49,278,120      
Accumulated Depreciation (15,870,459)      
Investment in Real Estate Net 33,407,661      
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 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 623,527      
Gross Amount Carried at close of period 12/31/2016, Land 9,435,760      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 33,187,767      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 42,623,527      
Accumulated Depreciation (8,254,511)      
Investment in Real Estate Net 34,369,016      
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 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 2,182,860      
Gross Amount Carried at close of period 12/31/2016, Land 23,420,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 72,160,559      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 95,580,559      
Accumulated Depreciation (30,934,660)      
Investment in Real Estate Net 64,645,899      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Hudson Crossing Two [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location New York, NY      
Real Estate And Accumulated Depreciation Units 0      
Initial Cost to Company, Land $ 10,599,287      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 3,293,787      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2016, Land 10,599,287      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 3,293,787      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 13,893,074      
Accumulated Depreciation 0      
Investment in Real Estate Net 13,893,074      
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 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 4,844,133      
Gross Amount Carried at close of period 12/31/2016, Land 5,350,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 45,958,207      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 51,308,207      
Accumulated Depreciation (20,241,451)      
Investment in Real Estate Net 31,066,756      
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 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 12/31/2016, 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      
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 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 992,859      
Gross Amount Carried at close of period 12/31/2016, Land 2,732,800      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 14,881,141      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 17,613,941      
Accumulated Depreciation (6,865,471)      
Investment in Real Estate Net 10,748,470      
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 280      
Initial Cost to Company, Land $ 14,791,831      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 76,417,368      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 160,373      
Gross Amount Carried at close of period 12/31/2016, Land 14,791,831      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 76,577,741      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 91,369,572      
Accumulated Depreciation (11,450,392)      
Investment in Real Estate Net 79,919,180      
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 206      
Initial Cost to Company, Land $ 11,726,305      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 55,592,607      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 10,285      
Gross Amount Carried at close of period 12/31/2016, Land 11,726,305      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 55,602,892      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 67,329,197      
Accumulated Depreciation (2,870,469)      
Investment in Real Estate Net 64,458,728      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Kelvin, The [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Irvine, CA      
Real Estate And Accumulated Depreciation Units 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 140,201      
Gross Amount Carried at close of period 12/31/2016, Land 15,521,552      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 64,993,649      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 80,515,201      
Accumulated Depreciation (5,226,037)      
Investment in Real Estate Net 75,289,164      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Kendall Square II [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Cambridge, MA      
Real Estate And Accumulated Depreciation Units 0      
Initial Cost to Company, Land $ 0      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 2,361,587      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2016, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 2,361,587      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 2,361,587      
Accumulated Depreciation 0      
Investment in Real Estate Net 2,361,587      
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 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 8,727,114      
Gross Amount Carried at close of period 12/31/2016, Land 27,246,045      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 46,468,164      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 73,714,209      
Accumulated Depreciation (27,123,316)      
Investment in Real Estate Net 46,590,893      
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 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 12,900,751      
Gross Amount Carried at close of period 12/31/2016, Land 5,928,400      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 46,496,013      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 52,424,413      
Accumulated Depreciation (32,166,271)      
Investment in Real Estate Net 20,258,142      
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 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 927,140      
Gross Amount Carried at close of period 12/31/2016, Land 5,805,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 26,632,140      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 32,437,140      
Accumulated Depreciation (7,515,112)      
Investment in Real Estate Net 24,922,028      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Loft 590 [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Arlington, VA      
Real Estate And Accumulated Depreciation Units 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 593,626      
Gross Amount Carried at close of period 12/31/2016, Land 20,100,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 68,502,649      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 88,602,649      
Accumulated Depreciation (11,467,543)      
Investment in Real Estate Net 77,135,106      
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 186      
Initial Cost to Company, Land $ 23,300,000      
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 4,430,000      
Gross Amount Carried at close of period 12/31/2016, Land 23,300,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 82,875,657      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 106,175,657      
Accumulated Depreciation (14,293,167)      
Investment in Real Estate Net 91,882,490      
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 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 1,952,072      
Gross Amount Carried at close of period 12/31/2016, Land 73,170,045      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 55,914,582      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 129,084,627      
Accumulated Depreciation (20,862,433)      
Investment in Real Estate Net 108,222,194      
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 710      
Initial Cost to Company, Land $ 47,096,917      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 150,143,916      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 77,175,848      
Gross Amount Carried at close of period 12/31/2016, Land 47,096,917      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 227,319,764      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 274,416,681      
Accumulated Depreciation (140,185,560)      
Investment in Real Estate Net 134,231,121      
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 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 726,983      
Gross Amount Carried at close of period 12/31/2016, Land 22,346,513      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 62,228,141      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 84,574,654      
Accumulated Depreciation (11,547,865)      
Investment in Real Estate Net 73,026,789      
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 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 5,590,178      
Gross Amount Carried at close of period 12/31/2016, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 174,432,620      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 174,432,620      
Accumulated Depreciation (34,075,934)      
Investment in Real Estate Net 140,356,686      
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 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 4,874,252      
Gross Amount Carried at close of period 12/31/2016, Land 60,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 94,185,734      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 155,085,734      
Accumulated Depreciation (17,348,528)      
Investment in Real Estate Net 137,737,206      
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 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 419,390      
Gross Amount Carried at close of period 12/31/2016, Land 8,125,216      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 27,798,174      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 35,923,390      
Accumulated Depreciation (5,879,972)      
Investment in Real Estate Net 30,043,418      
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 0      
Initial Cost to Company, Land $ 0      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 11,539      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2016, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 11,539      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 11,539      
Accumulated Depreciation 0      
Investment in Real Estate Net 11,539      
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 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 1,742,611      
Gross Amount Carried at close of period 12/31/2016, Land 8,500,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 54,272,057      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 62,772,057      
Accumulated Depreciation (20,324,720)      
Investment in Real Estate Net 42,447,337      
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 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 5,632,060      
Gross Amount Carried at close of period 12/31/2016, Land 75,800,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 108,337,461      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 184,137,461      
Accumulated Depreciation (21,534,636)      
Investment in Real Estate Net 162,602,825      
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 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 3,216,250      
Gross Amount Carried at close of period 12/31/2016, Land 9,360,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 23,994,803      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 33,354,803      
Accumulated Depreciation (13,232,302)      
Investment in Real Estate Net 20,122,501      
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 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 12,538,178      
Gross Amount Carried at close of period 12/31/2016, Land 38,607,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 90,010,395      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 128,617,395      
Accumulated Depreciation (29,143,721)      
Investment in Real Estate Net 99,473,674      
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 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 10,511,874      
Gross Amount Carried at close of period 12/31/2016, Land 5,524,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 25,203,579      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 30,727,579      
Accumulated Depreciation (17,391,149)      
Investment in Real Estate Net 13,336,430      
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 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 9,746,651      
Gross Amount Carried at close of period 12/31/2016, Land 3,390,700      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 40,263,925      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 43,654,625      
Accumulated Depreciation (28,656,591)      
Investment in Real Estate Net 14,998,034      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
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 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 1,529,010      
Gross Amount Carried at close of period 12/31/2016, Land 22,200,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 30,201,989      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 52,401,989      
Accumulated Depreciation (5,884,677)      
Investment in Real Estate Net 46,517,312      
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 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 2,425,184      
Gross Amount Carried at close of period 12/31/2016, Land 15,400,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 37,899,520      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 53,299,520      
Accumulated Depreciation (6,786,525)      
Investment in Real Estate Net 46,512,995      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
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 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 2,437,138      
Gross Amount Carried at close of period 12/31/2016, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 123,232,497      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 123,232,497      
Accumulated Depreciation (24,113,286)      
Investment in Real Estate Net 99,119,211      
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 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 5,042,217      
Gross Amount Carried at close of period 12/31/2016, Land 23,400,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 66,062,655      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 89,462,655      
Accumulated Depreciation (31,804,000)      
Investment in Real Estate Net 57,658,655      
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 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 3,961,557      
Gross Amount Carried at close of period 12/31/2016, Land 5,111,200      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 15,871,995      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 20,983,195      
Accumulated Depreciation (9,843,174)      
Investment in Real Estate Net 11,140,021      
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 301      
Initial Cost to Company, Land $ 16,807,519      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 63,703,105      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,853      
Gross Amount Carried at close of period 12/31/2016, Land 16,807,519      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 63,707,958      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 80,515,477      
Accumulated Depreciation (3,220,384)      
Investment in Real Estate Net 77,295,093      
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 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 615,810      
Gross Amount Carried at close of period 12/31/2016, Land 7,740,467      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 44,761,991      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 52,502,458      
Accumulated Depreciation (3,368,591)      
Investment in Real Estate Net 49,133,867      
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 241      
Initial Cost to Company, Land $ 30,224,393      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 132,422,943      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2016, Land 30,224,393      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 132,422,943      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 162,647,336      
Accumulated Depreciation 0      
Investment in Real Estate Net 162,647,336      
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 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 1,114,418      
Gross Amount Carried at close of period 12/31/2016, Land 32,250,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 111,864,418      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 144,114,418      
Accumulated Depreciation (18,609,682)      
Investment in Real Estate Net 125,504,736      
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 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 25,690      
Gross Amount Carried at close of period 12/31/2016, Land 5,911,041      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 19,980,649      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 25,891,690      
Accumulated Depreciation (1,315,590)      
Investment in Real Estate Net 24,576,100      
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 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 5,639,147      
Gross Amount Carried at close of period 12/31/2016, Land 40,504,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 23,664,826      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 64,168,826      
Accumulated Depreciation (11,317,834)      
Investment in Real Estate Net 52,850,992      
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 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 6,917,858      
Gross Amount Carried at close of period 12/31/2016, Land 37,600,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 16,773,455      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 54,373,455      
Accumulated Depreciation (9,519,277)      
Investment in Real Estate Net 44,854,178      
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 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 8,635,413      
Gross Amount Carried at close of period 12/31/2016, Land 52,654,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 31,681,164      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 84,335,164      
Accumulated Depreciation (15,575,683)      
Investment in Real Estate Net 68,759,481      
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 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 8,841,139      
Gross Amount Carried at close of period 12/31/2016, Land 102,163,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 117,830,541      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 219,993,541      
Accumulated Depreciation (44,109,145)      
Investment in Real Estate Net 175,884,396      
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 173      
Initial Cost to Company, Land $ 16,667,059      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 67,690,072      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 48,612      
Gross Amount Carried at close of period 12/31/2016, Land 16,667,059      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 67,738,684      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 84,405,743      
Accumulated Depreciation (4,037,098)      
Investment in Real Estate Net 80,368,645      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Park at Pentagon Row (fka Pentagon City) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Arlington, VA      
Real Estate And Accumulated Depreciation Units 298      
Initial Cost to Company, Land $ 28,300,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 78,838,184      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,353,525      
Gross Amount Carried at close of period 12/31/2016, Land 28,300,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 80,191,709      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 108,491,709      
Accumulated Depreciation (14,341,704)      
Investment in Real Estate Net 94,150,005      
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 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 1,138,671      
Gross Amount Carried at close of period 12/31/2016, Land 13,700,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 60,226,190      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 73,926,190      
Accumulated Depreciation (10,132,810)      
Investment in Real Estate Net 63,793,380      
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 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 1,303,861      
Gross Amount Carried at close of period 12/31/2016, Land 43,200,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 130,057,220      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 173,257,220      
Accumulated Depreciation (24,868,371)      
Investment in Real Estate Net 148,388,849      
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 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 9,833,303      
Gross Amount Carried at close of period 12/31/2016, Land 3,033,500      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 37,135,686      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 40,169,186      
Accumulated Depreciation (26,282,067)      
Investment in Real Estate Net 13,887,119      
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 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 4,057,554      
Gross Amount Carried at close of period 12/31/2016, Land 6,246,700      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 15,885,007      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 22,131,707      
Accumulated Depreciation (11,039,298)      
Investment in Real Estate Net 11,092,409      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Pearl, The [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Seattle, WA      
Real Estate And Accumulated Depreciation Units 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 86,236      
Gross Amount Carried at close of period 12/31/2016, Land 6,972,585      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 26,613,651      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 33,586,236      
Accumulated Depreciation (1,802,018)      
Investment in Real Estate Net 31,784,218      
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 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 4,353,371      
Gross Amount Carried at close of period 12/31/2016, Land 18,094,052      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 86,259,319      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 104,353,371      
Accumulated Depreciation (23,034,817)      
Investment in Real Estate Net 81,318,554      
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 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 21,252,912      
Gross Amount Carried at close of period 12/31/2016, Land 35,100,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 54,726,734      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 89,826,734      
Accumulated Depreciation (22,557,639)      
Investment in Real Estate Net 67,269,095      
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 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 3,619,935      
Gross Amount Carried at close of period 12/31/2016, Land 3,572,400      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 18,280,929      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 21,853,329      
Accumulated Depreciation (12,064,192)      
Investment in Real Estate Net 9,789,137      
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 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 4,531,435      
Gross Amount Carried at close of period 12/31/2016, Land 8,640,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 26,018,561      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 34,658,561      
Accumulated Depreciation (14,294,138)      
Investment in Real Estate Net 20,364,423      
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 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 20,261,246      
Gross Amount Carried at close of period 12/31/2016, Land 22,487,006      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 117,104,159      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 139,591,165      
Accumulated Depreciation (75,662,868)      
Investment in Real Estate Net 63,928,297      
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 453      
Initial Cost to Company, Land $ 40,830,011      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 178,838,375      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,685      
Gross Amount Carried at close of period 12/31/2016, Land 40,830,011      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 178,841,060      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 219,671,071      
Accumulated Depreciation (4,297,727)      
Investment in Real Estate Net 215,373,344      
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 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 2,474,023      
Gross Amount Carried at close of period 12/31/2016, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 70,451,336      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 70,451,336      
Accumulated Depreciation (12,649,164)      
Investment in Real Estate Net 57,802,172      
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 256      
Initial Cost to Company, Land $ 32,000,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 64,436,539      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,366,624      
Gross Amount Carried at close of period 12/31/2016, Land 32,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 65,803,163      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 97,803,163      
Accumulated Depreciation (25,533,405)      
Investment in Real Estate Net 72,269,758      
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 269      
Initial Cost to Company, Land $ 76,292,169      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 171,532,416      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 40,159      
Gross Amount Carried at close of period 12/31/2016, Land 76,292,169      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 171,572,575      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 247,864,744      
Accumulated Depreciation (12,053,844)      
Investment in Real Estate Net 235,810,900      
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 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 6,603,855      
Gross Amount Carried at close of period 12/31/2016, Land 28,200,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 76,399,770      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 104,599,770      
Accumulated Depreciation (35,742,052)      
Investment in Real Estate Net 68,857,718      
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 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 1,276,264      
Gross Amount Carried at close of period 12/31/2016, Land 26,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 85,687,426      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 112,587,426      
Accumulated Depreciation (15,916,309)      
Investment in Real Estate Net 96,671,117      
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 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 1,069,525      
Gross Amount Carried at close of period 12/31/2016, Land 15,546,376      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 66,389,535      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 81,935,911      
Accumulated Depreciation (13,743,779)      
Investment in Real Estate Net 68,192,132      
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 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 828,734      
Gross Amount Carried at close of period 12/31/2016, Land 10,300,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 34,317,479      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 44,617,479      
Accumulated Depreciation (6,900,171)      
Investment in Real Estate Net 37,717,308      
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 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 5,843,205      
Gross Amount Carried at close of period 12/31/2016, Land 1,857,400      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 22,556,459      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 24,413,859      
Accumulated Depreciation (16,685,572)      
Investment in Real Estate Net 7,728,287      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Renaissance Villas [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Berkeley, CA      
Real Estate And Accumulated Depreciation Units 34      
Initial Cost to Company, Land $ 2,458,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 4,542,000      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 157,541      
Gross Amount Carried at close of period 12/31/2016, Land 2,458,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 4,699,541      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 7,157,541      
Accumulated Depreciation (1,716,722)      
Investment in Real Estate Net 5,440,819      
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 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 3,985,141      
Gross Amount Carried at close of period 12/31/2016, Land 27,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 37,014,746      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 64,014,746      
Accumulated Depreciation (7,098,473)      
Investment in Real Estate Net 56,916,273      
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 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 10,012,055      
Gross Amount Carried at close of period 12/31/2016, Land 11,918,917      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 78,874,696      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 90,793,613      
Accumulated Depreciation (34,843,070)      
Investment in Real Estate Net 55,950,543      
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 584      
Initial Cost to Company, Land $ 16,769,205      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 77,511,523      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,904,720      
Gross Amount Carried at close of period 12/31/2016, Land 16,769,205      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 80,416,243      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 97,185,448      
Accumulated Depreciation (27,282,993)      
Investment in Real Estate Net 69,902,455      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Residences at Westgate I (fka Westage II) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Pasadena, CA      
Real Estate And Accumulated Depreciation Units 252      
Initial Cost to Company, Land $ 17,859,785      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 108,596,287      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 152,142      
Gross Amount Carried at close of period 12/31/2016, Land 17,859,785      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 108,748,429      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 126,608,214      
Accumulated Depreciation (11,706,631)      
Investment in Real Estate Net 114,901,583      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Residences at Westgate II (fka Westgage III) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Pasadena, CA      
Real Estate And Accumulated Depreciation Units 88      
Initial Cost to Company, Land $ 12,118,248      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 40,458,283      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 28,122      
Gross Amount Carried at close of period 12/31/2016, Land 12,118,248      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 40,486,405      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 52,604,653      
Accumulated Depreciation (2,670,021)      
Investment in Real Estate Net 49,934,632      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Rianna I [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Seattle, WA      
Real Estate And Accumulated Depreciation Units 78      
Initial Cost to Company, Land $ 2,268,160      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 14,864,482      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 570,971      
Gross Amount Carried at close of period 12/31/2016, Land 2,268,160      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 15,435,453      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 17,703,613      
Accumulated Depreciation (4,912,805)      
Investment in Real Estate Net 12,790,808      
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 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 5,443,381      
Gross Amount Carried at close of period 12/31/2016, Land 11,809,500      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 39,447,429      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 51,256,929      
Accumulated Depreciation (23,108,949)      
Investment in Real Estate Net 28,147,980      
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 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 1,530,506      
Gross Amount Carried at close of period 12/31/2016, Land 34,963,355      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 86,118,164      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 121,081,519      
Accumulated Depreciation (16,714,984)      
Investment in Real Estate Net 104,366,535      
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 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 1,833,334      
Gross Amount Carried at close of period 12/31/2016, Land 17,136,645      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 42,369,865      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 59,506,510      
Accumulated Depreciation (7,532,830)      
Investment in Real Estate Net 51,973,680      
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 319      
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 1,100,173      
Gross Amount Carried at close of period 12/31/2016, Land 14,355,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 81,994,222      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 96,349,222      
Accumulated Depreciation (18,616,561)      
Investment in Real Estate Net 77,732,661      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Rolling Green (Milford) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Milford, MA      
Real Estate And Accumulated Depreciation Units 304      
Initial Cost to Company, Land $ 2,012,350      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 13,452,150      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 7,325,804      
Gross Amount Carried at close of period 12/31/2016, Land 2,012,350      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 20,777,954      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 22,790,304      
Accumulated Depreciation (12,541,523)      
Investment in Real Estate Net 10,248,781      
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 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 873,630      
Gross Amount Carried at close of period 12/31/2016, Land 4,922,840      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 31,075,790      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 35,998,630      
Accumulated Depreciation (7,963,684)      
Investment in Real Estate Net 28,034,946      
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 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 703,088      
Gross Amount Carried at close of period 12/31/2016, Land 14,641,990      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 43,561,098      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 58,203,088      
Accumulated Depreciation (11,836,842)      
Investment in Real Estate Net 46,366,246      
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 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 3,798,267      
Gross Amount Carried at close of period 12/31/2016, Land 663,800      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 9,773,070      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 10,436,870      
Accumulated Depreciation (7,029,871)      
Investment in Real Estate Net 3,406,999      
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 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 14,316,432      
Gross Amount Carried at close of period 12/31/2016, Land 3,342,381      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 45,653,764      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 48,996,145      
Accumulated Depreciation (33,910,069)      
Investment in Real Estate Net 15,086,076      
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 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 3,079,215      
Gross Amount Carried at close of period 12/31/2016, Land 10,560,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 28,653,672      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 39,213,672      
Accumulated Depreciation (16,045,953)      
Investment in Real Estate Net 23,167,719      
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 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 4,194,009      
Gross Amount Carried at close of period 12/31/2016, Land 1,781,600      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 20,925,925      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 22,707,525      
Accumulated Depreciation (12,497,731)      
Investment in Real Estate Net 10,209,794      
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 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 4,638,329      
Gross Amount Carried at close of period 12/31/2016, Land 16,836,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 40,052,329      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 56,888,329      
Accumulated Depreciation (11,663,739)      
Investment in Real Estate Net 45,224,590      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Skyline Towers [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Falls Church, VA      
Real Estate And Accumulated Depreciation Units 939      
Initial Cost to Company, Land $ 78,278,200      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 91,485,591      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 39,225,721      
Gross Amount Carried at close of period 12/31/2016, Land 78,278,200      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 130,711,312      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 208,989,512      
Accumulated Depreciation (66,807,948)      
Investment in Real Estate Net 142,181,564      
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 0      
Initial Cost to Company, Land $ 29,406,606      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 3,589,891      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2016, Land 29,406,606      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 3,589,891      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 32,996,497      
Accumulated Depreciation 0      
Investment in Real Estate Net 32,996,497      
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 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 4,962,421      
Gross Amount Carried at close of period 12/31/2016, Land 7,503,400      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 29,010,928      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 36,514,328      
Accumulated Depreciation (17,403,278)      
Investment in Real Estate Net 19,111,050      
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 360      
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 2,331,779      
Gross Amount Carried at close of period 12/31/2016, Land 68,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 81,808,640      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 150,708,640      
Accumulated Depreciation (15,596,819)      
Investment in Real Estate Net 135,111,821      
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 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 3,202,676      
Gross Amount Carried at close of period 12/31/2016, Land 6,936,600      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 17,526,745      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 24,463,345      
Accumulated Depreciation (11,356,629)      
Investment in Real Estate Net 13,106,716      
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 0      
Initial Cost to Company, Land $ 18,200,000      
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 12/31/2016, Land 18,200,000      
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 18,200,000      
Accumulated Depreciation 0      
Investment in Real Estate Net 18,200,000      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Summerset Village II [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Chatsworth, CA      
Real Estate And Accumulated Depreciation Units 0      
Initial Cost to Company, Land $ 260,646      
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 12/31/2016, Land 260,646      
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 260,646      
Accumulated Depreciation 0      
Investment in Real Estate Net 260,646      
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 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 3,586,242      
Gross Amount Carried at close of period 12/31/2016, Land 26,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 32,021,266      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 58,021,266      
Accumulated Depreciation (7,628,434)      
Investment in Real Estate Net 50,392,832      
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 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 165,340      
Gross Amount Carried at close of period 12/31/2016, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 59,047,213      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 59,047,213      
Accumulated Depreciation (10,287,817)      
Investment in Real Estate Net 48,759,396      
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 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 982,446      
Gross Amount Carried at close of period 12/31/2016, Land 14,087,610      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 17,296,597      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 31,384,207      
Accumulated Depreciation (5,171,269)      
Investment in Real Estate Net 26,212,938      
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 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 5,396,605      
Gross Amount Carried at close of period 12/31/2016, Land 26,767,171      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 224,219,333      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 250,986,504      
Accumulated Depreciation (62,174,271)      
Investment in Real Estate Net 188,812,233      
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 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 703,110      
Gross Amount Carried at close of period 12/31/2016, Land 7,030,766      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 29,708,872      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 36,739,638      
Accumulated Depreciation (4,264,421)      
Investment in Real Estate Net 32,475,217      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Town Center South Commercial [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location St. Charles, MD      
Real Estate And Accumulated Depreciation Units 0      
Initial Cost to Company, Land $ 1,500,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 9,394      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2016, Land 1,500,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 9,394      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 1,509,394      
Accumulated Depreciation 0      
Investment in Real Estate Net 1,509,394      
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 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 2,117,754      
Gross Amount Carried at close of period 12/31/2016, Land 15,568,464      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 57,147,361      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 72,715,825      
Accumulated Depreciation (17,050,654)      
Investment in Real Estate Net 55,665,171      
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 287      
Initial Cost to Company, Land $ 12,542,418      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 75,766,505      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 283,439      
Gross Amount Carried at close of period 12/31/2016, Land 12,542,418      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 76,049,944      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 88,592,362      
Accumulated Depreciation (10,215,162)      
Investment in Real Estate Net 78,377,200      
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 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 724,720      
Gross Amount Carried at close of period 12/31/2016, Land 8,800,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 22,913,008      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 31,713,008      
Accumulated Depreciation (10,116,792)      
Investment in Real Estate Net 21,596,216      
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 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 8,156,057      
Gross Amount Carried at close of period 12/31/2016, Land 9,403,960      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 198,752,097      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 208,156,057      
Accumulated Depreciation (52,465,809)      
Investment in Real Estate Net 155,690,248      
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 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 750,251      
Gross Amount Carried at close of period 12/31/2016, Land 15,322,724      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 76,926,845      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 92,249,569      
Accumulated Depreciation (14,412,958)      
Investment in Real Estate Net 77,836,611      
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 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 4,206,652      
Gross Amount Carried at close of period 12/31/2016, Land 5,190,700      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 13,885,761      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 19,076,461      
Accumulated Depreciation (9,342,080)      
Investment in Real Estate Net 9,734,381      
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 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 1,921,459      
Gross Amount Carried at close of period 12/31/2016, Land 18,539,817      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 132,328,824      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 150,868,641      
Accumulated Depreciation (34,495,297)      
Investment in Real Estate Net 116,373,344      
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 272      
Initial Cost to Company, Land $ 1,665,100      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 14,985,678      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 9,397,116      
Gross Amount Carried at close of period 12/31/2016, Land 1,665,100      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 24,382,794      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 26,047,894      
Accumulated Depreciation (18,569,428)      
Investment in Real Estate Net 7,478,466      
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 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 814,553      
Gross Amount Carried at close of period 12/31/2016, Land 15,100,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 41,673,949      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 56,773,949      
Accumulated Depreciation (7,931,652)      
Investment in Real Estate Net 48,842,297      
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 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 2,598,732      
Gross Amount Carried at close of period 12/31/2016, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 88,538,735      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 88,538,735      
Accumulated Depreciation (15,463,270)      
Investment in Real Estate Net 73,075,465      
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 554      
Initial Cost to Company, Land $ 27,709,329      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 175,174,600      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 15,853      
Gross Amount Carried at close of period 12/31/2016, Land 27,709,329      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 175,190,453      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 202,899,782      
Accumulated Depreciation (5,630,074)      
Investment in Real Estate Net 197,269,708      
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 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 16,333,057      
Gross Amount Carried at close of period 12/31/2016, Land 4,525,800      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 57,069,350      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 61,595,150      
Accumulated Depreciation (43,829,076)      
Investment in Real Estate Net 17,766,074      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Vista on Courthouse [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Arlington, VA      
Real Estate And Accumulated Depreciation Units 220      
Initial Cost to Company, Land $ 15,550,260      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 69,449,740      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,412,841      
Gross Amount Carried at close of period 12/31/2016, Land 15,550,260      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 70,862,581      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 86,412,841      
Accumulated Depreciation (21,083,205)      
Investment in Real Estate Net 65,329,636      
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 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 4,033,426      
Gross Amount Carried at close of period 12/31/2016, Land 12,448,888      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 56,077,874      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 68,526,762      
Accumulated Depreciation (15,551,486)      
Investment in Real Estate Net 52,975,276      
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 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 6,380,938      
Gross Amount Carried at close of period 12/31/2016, Land 34,400,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 114,866,797      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 149,266,797      
Accumulated Depreciation (20,648,479)      
Investment in Real Estate Net 128,618,318      
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 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 1,145,350      
Gross Amount Carried at close of period 12/31/2016, Land 16,800,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 35,219,406      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 52,019,406      
Accumulated Depreciation (6,303,140)      
Investment in Real Estate Net 45,716,266      
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 207      
Initial Cost to Company, Land $ 84,800,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 67,055,502      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,128,963      
Gross Amount Carried at close of period 12/31/2016, Land 84,800,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 71,184,465      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 155,984,465      
Accumulated Depreciation (15,247,357)      
Investment in Real Estate Net 140,737,108      
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 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 2,430,837      
Gross Amount Carried at close of period 12/31/2016, Land 469,546      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 165,553,859      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 166,023,405      
Accumulated Depreciation (50,041,771)      
Investment in Real Estate Net 115,981,634      
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 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 467,221      
Gross Amount Carried at close of period 12/31/2016, Land 10,600,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 44,602,428      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 55,202,428      
Accumulated Depreciation (8,102,186)      
Investment in Real Estate Net 47,100,242      
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 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 2,222,721      
Gross Amount Carried at close of period 12/31/2016, Land 64,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 63,365,980      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 128,265,980      
Accumulated Depreciation (12,146,404)      
Investment in Real Estate Net 116,119,576      
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 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 2,395,974      
Gross Amount Carried at close of period 12/31/2016, Land 34,200,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 59,358,604      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 93,558,604      
Accumulated Depreciation (10,435,607)      
Investment in Real Estate Net 83,122,997      
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 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 839,038      
Gross Amount Carried at close of period 12/31/2016, Land 3,060,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 6,377,909      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 9,437,909      
Accumulated Depreciation (3,354,957)      
Investment in Real Estate Net 6,082,952      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Westside Barry (fka 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 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 547,484      
Gross Amount Carried at close of period 12/31/2016, Land 1,530,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 3,571,007      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 5,101,007      
Accumulated Depreciation (1,914,301)      
Investment in Real Estate Net 3,186,706      
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 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 589,475      
Gross Amount Carried at close of period 12/31/2016, Land 1,785,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 3,822,729      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 5,607,729      
Accumulated Depreciation (2,090,807)      
Investment in Real Estate Net 3,516,922      
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 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 542,370      
Gross Amount Carried at close of period 12/31/2016, Land 1,955,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 4,083,805      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 6,038,805      
Accumulated Depreciation (2,154,240)      
Investment in Real Estate Net 3,884,565      
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 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 838,212      
Gross Amount Carried at close of period 12/31/2016, Land 3,060,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 6,377,602      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 9,437,602      
Accumulated Depreciation (3,356,464)      
Investment in Real Estate Net 6,081,138      
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 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 2,301,916      
Gross Amount Carried at close of period 12/31/2016, Land 9,605,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 22,285,301      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 31,890,301      
Accumulated Depreciation (11,417,791)      
Investment in Real Estate Net 20,472,510      
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 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 9,609,243      
Gross Amount Carried at close of period 12/31/2016, Land 2,662,900      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 33,594,740      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 36,257,640      
Accumulated Depreciation (24,492,262)      
Investment in Real Estate Net 11,765,378      
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 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 6,948,103      
Gross Amount Carried at close of period 12/31/2016, Land 9,729,900      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 29,957,871      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 39,687,771      
Accumulated Depreciation (20,466,696)      
Investment in Real Estate Net 19,221,075      
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 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 110,281,527      
Gross Amount Carried at close of period 12/31/2016, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 110,281,527      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 110,281,527      
Accumulated Depreciation (86,786,203)      
Investment in Real Estate Net 23,495,324      
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 0      
Initial Cost to Company, Land $ 0      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 25,724      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2016, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 25,724      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 25,724      
Accumulated Depreciation 0      
Investment in Real Estate Net 25,724      
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 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 51,888      
Gross Amount Carried at close of period 12/31/2016, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 51,888      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 51,888      
Accumulated Depreciation (3,279)      
Investment in Real Estate Net 48,609      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Investment in Real Estate - Wholly Owned Unencumbered [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Units 52,102      
Initial Cost to Company, Land $ 4,477,036,244      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 13,029,648,911      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 941,634,623      
Gross Amount Carried at close of period 12/31/2016, Land 4,477,036,244      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 13,971,283,534      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 18,448,319,778      
Accumulated Depreciation (3,651,990,171)      
Investment in Real Estate Net 14,796,329,607      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
101 West End [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location New York, NY      
Real Estate And Accumulated Depreciation Units 506      
Initial Cost to Company, Land $ 190,600,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 131,374,708      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,789,525      
Gross Amount Carried at close of period 12/31/2016, Land 190,600,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 135,164,233      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 325,764,233      
Accumulated Depreciation (29,116,644)      
Investment in Real Estate Net 296,647,589      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 105,541,770      
Joyce On Pentagon Row 1401 [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Arlington, VA      
Real Estate And Accumulated Depreciation Units 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 4,067,409      
Gross Amount Carried at close of period 12/31/2016, Land 9,780,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 93,735,574      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 103,515,574      
Accumulated Depreciation (28,321,732)      
Investment in Real Estate Net 75,193,842      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 57,324,952      
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 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 2,836,196      
Gross Amount Carried at close of period 12/31/2016, Land 13,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 78,107,375      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 91,107,375      
Accumulated Depreciation (13,691,308)      
Investment in Real Estate Net $ 77,416,067      
Real Estate And Accumulated Depreciation, Encumbrances Reference (K)      
300 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 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 2,284,116      
Gross Amount Carried at close of period 12/31/2016, Land 48,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 98,458,755      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 147,358,755      
Accumulated Depreciation (18,157,350)      
Investment in Real Estate Net 129,201,405      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 59,763,098      
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 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 2,200,064      
Gross Amount Carried at close of period 12/31/2016, Land 79,400,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 81,322,688      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 160,722,688      
Accumulated Depreciation (16,079,870)      
Investment in Real Estate Net $ 144,642,818      
Real Estate And Accumulated Depreciation, Encumbrances Reference (K)      
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 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 2,855,350      
Gross Amount Carried at close of period 12/31/2016, Land 12,600,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 37,250,122      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 49,850,122      
Accumulated Depreciation (6,449,425)      
Investment in Real Estate Net $ 43,400,697      
Real Estate And Accumulated Depreciation, Encumbrances Reference (K)      
4701 Willard Ave [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Chevy Chase, MD      
Real Estate And Accumulated Depreciation Units 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 29,256,068      
Gross Amount Carried at close of period 12/31/2016, Land 76,921,130      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 183,203,750      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 260,124,880      
Accumulated Depreciation (41,887,641)      
Investment in Real Estate Net 218,237,239      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 92,377,799      
55 West Fifth I & II [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location San Mateo, CA      
Real Estate And Accumulated Depreciation Units 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 11,437,590      
Gross Amount Carried at close of period 12/31/2016, Land 21,041,710      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 83,368,913      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 104,410,623      
Accumulated Depreciation (17,523,868)      
Investment in Real Estate Net 86,886,755      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 27,229,091      
800 Sixth Ave (fka Chelsea) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location New York, NY      
Real Estate And Accumulated Depreciation Units 266      
Initial Cost to Company, Land $ 59,900,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 155,861,605      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,300,274      
Gross Amount Carried at close of period 12/31/2016, Land 59,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 157,161,879      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 217,061,879      
Accumulated Depreciation (27,296,410)      
Investment in Real Estate Net 189,765,469      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 76,708,911      
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 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 6,246,692      
Gross Amount Carried at close of period 12/31/2016, Land 3,252,993      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 27,992,287      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 31,245,280      
Accumulated Depreciation (16,141,485)      
Investment in Real Estate Net 15,103,795      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 1,007,468      
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 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 8,049,828      
Gross Amount Carried at close of period 12/31/2016, Land 25,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 31,643,022      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 56,643,022      
Accumulated Depreciation (16,858,183)      
Investment in Real Estate Net 39,784,839      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 19,946,425      
Acappella [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Pasadena, CA      
Real Estate And Accumulated Depreciation Units 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 1,816,839      
Gross Amount Carried at close of period 12/31/2016, Land 5,839,548      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 31,177,291      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 37,016,839      
Accumulated Depreciation (8,938,860)      
Investment in Real Estate Net 28,077,979      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 19,213,624      
Alborada [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Fremont, CA      
Real Estate And Accumulated Depreciation Units 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 7,336,822      
Gross Amount Carried at close of period 12/31/2016, Land 24,310,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 66,550,951      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 90,860,951      
Accumulated Depreciation (36,408,710)      
Investment in Real Estate Net $ 54,452,241      
Real Estate And Accumulated Depreciation, Encumbrances Reference (I)      
Alcyone [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Seattle, WA      
Real Estate And Accumulated Depreciation Units 161      
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 560,007      
Gross Amount Carried at close of period 12/31/2016, Land 11,379,497      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 49,920,510      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 61,300,007      
Accumulated Depreciation (5,595,873)      
Investment in Real Estate Net 55,704,134      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 28,675,325      
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 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 1,319,564      
Gross Amount Carried at close of period 12/31/2016, Land 26,650,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 64,169,564      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 90,819,564      
Accumulated Depreciation (18,676,294)      
Investment in Real Estate Net $ 72,143,270      
Real Estate And Accumulated Depreciation, Encumbrances Reference (J)      
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 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 1,314,168      
Gross Amount Carried at close of period 12/31/2016, Land 7,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 21,851,527      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 28,851,527      
Accumulated Depreciation (10,748,443)      
Investment in Real Estate Net 18,103,084      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 22,749,081      
Avanti [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Anaheim, CA      
Real Estate And Accumulated Depreciation Units 162      
Initial Cost to Company, Land $ 12,960,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 18,497,682      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,706,778      
Gross Amount Carried at close of period 12/31/2016, Land 12,960,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 21,204,460      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 34,164,460      
Accumulated Depreciation (8,619,700)      
Investment in Real Estate Net 25,544,760      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 25,005,850      
Avenir [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Boston, MA      
Real Estate And Accumulated Depreciation Units 241      
Initial Cost to Company, Land $ 0      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 114,321,618      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,416,319      
Gross Amount Carried at close of period 12/31/2016, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 115,737,937      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 115,737,937      
Accumulated Depreciation (20,055,604)      
Investment in Real Estate Net 95,682,333      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 90,544,765      
Bella Vista Apartments at Boca Del Mar [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Woodland Hills, CA      
Real Estate And Accumulated Depreciation Units 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 4,165,480      
Gross Amount Carried at close of period 12/31/2016, Land 31,682,754      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 125,261,266      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 156,944,020      
Accumulated Depreciation (49,400,072)      
Investment in Real Estate Net 107,543,948      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 57,848,455      
Berkeleyan [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Berkeley, CA      
Real Estate And Accumulated Depreciation Units 56      
Initial Cost to Company, Land $ 4,377,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 16,022,110      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 360,831      
Gross Amount Carried at close of period 12/31/2016, Land 4,377,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 16,382,941      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 20,759,941      
Accumulated Depreciation (6,147,451)      
Investment in Real Estate Net 14,612,490      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 8,188,077      
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 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 1,869,918      
Gross Amount Carried at close of period 12/31/2016, Land 12,600,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 45,397,297      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 57,997,297      
Accumulated Depreciation (8,314,350)      
Investment in Real Estate Net $ 49,682,947      
Real Estate And Accumulated Depreciation, Encumbrances Reference (K)      
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 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 11,662,759      
Gross Amount Carried at close of period 12/31/2016, Land 2,288,300      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 32,259,040      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 34,547,340      
Accumulated Depreciation (25,490,481)      
Investment in Real Estate Net $ 9,056,859      
Real Estate And Accumulated Depreciation, Encumbrances Reference (J)      
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 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 2,167,212      
Gross Amount Carried at close of period 12/31/2016, Land 3,397,100      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 11,456,286      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 14,853,386      
Accumulated Depreciation (7,244,601)      
Investment in Real Estate Net 7,608,785      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 9,205,288      
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 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 1,623,844      
Gross Amount Carried at close of period 12/31/2016, Land 9,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 18,574,170      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 27,574,170      
Accumulated Depreciation (3,264,484)      
Investment in Real Estate Net $ 24,309,686      
Real Estate And Accumulated Depreciation, Encumbrances Reference (K)      
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 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 3,359,210      
Gross Amount Carried at close of period 12/31/2016, Land 18,300,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 69,751,624      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 88,051,624      
Accumulated Depreciation (12,463,465)      
Investment in Real Estate Net $ 75,588,159      
Real Estate And Accumulated Depreciation, Encumbrances Reference (K)      
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 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 2,467,048      
Gross Amount Carried at close of period 12/31/2016, Land 23,500,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 55,512,121      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 79,012,121      
Accumulated Depreciation (10,603,755)      
Investment in Real Estate Net $ 68,408,366      
Real Estate And Accumulated Depreciation, Encumbrances Reference (K)      
Deerwood (SD) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location San Diego, CA      
Real Estate And Accumulated Depreciation Units 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 14,552,126      
Gross Amount Carried at close of period 12/31/2016, Land 2,082,095      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 33,291,941      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 35,374,036      
Accumulated Depreciation (26,781,646)      
Investment in Real Estate Net $ 8,592,390      
Real Estate And Accumulated Depreciation, Encumbrances Reference (J)      
DelMarRidge [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location San Diego, CA      
Real Estate And Accumulated Depreciation Units 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 3,554,417      
Gross Amount Carried at close of period 12/31/2016, Land 7,801,824      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 40,502,593      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 48,304,417      
Accumulated Depreciation (13,227,515)      
Investment in Real Estate Net 35,076,902      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 39,472,029      
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 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 907,589      
Gross Amount Carried at close of period 12/31/2016, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 124,667,393      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 124,667,393      
Accumulated Depreciation (22,844,872)      
Investment in Real Estate Net $ 101,822,521      
Real Estate And Accumulated Depreciation, Encumbrances Reference (K)      
Fairchase [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Fairfax, VA      
Real Estate And Accumulated Depreciation Units 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 791,751      
Gross Amount Carried at close of period 12/31/2016, Land 23,500,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 88,514,072      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 112,014,072      
Accumulated Depreciation (15,478,802)      
Investment in Real Estate Net $ 96,535,270      
Real Estate And Accumulated Depreciation, Encumbrances Reference (K)      
Fairfield [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Stamford, CT      
Real Estate And Accumulated Depreciation Units 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 7,374,368      
Gross Amount Carried at close of period 12/31/2016, Land 6,510,200      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 47,064,488      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 53,574,688      
Accumulated Depreciation (30,942,121)      
Investment in Real Estate Net 22,632,567      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 31,281,223      
Fine Arts Building [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Berkeley, CA      
Real Estate And Accumulated Depreciation Units 100      
Initial Cost to Company, Land $ 7,817,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 26,462,772      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 335,849      
Gross Amount Carried at close of period 12/31/2016, Land 7,817,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 26,798,621      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 34,615,621      
Accumulated Depreciation (9,960,485)      
Investment in Real Estate Net 24,655,136      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 16,055,441      
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 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 891,807      
Gross Amount Carried at close of period 12/31/2016, Land 35,200,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 109,660,005      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 144,860,005      
Accumulated Depreciation (18,523,867)      
Investment in Real Estate Net $ 126,336,138      
Real Estate And Accumulated Depreciation, Encumbrances Reference (K)      
Gaia Building [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Berkeley, CA      
Real Estate And Accumulated Depreciation Units 91      
Initial Cost to Company, Land $ 7,113,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 25,623,826      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 253,313      
Gross Amount Carried at close of period 12/31/2016, Land 7,113,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 25,877,139      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 32,990,139      
Accumulated Depreciation (9,605,521)      
Investment in Real Estate Net 23,384,618      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 14,492,793      
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 389      
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 580,456      
Gross Amount Carried at close of period 12/31/2016, Land 17,500,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 75,259,373      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 92,759,373      
Accumulated Depreciation (12,410,304)      
Investment in Real Estate Net 80,349,069      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 96,542,458      
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 201      
Initial Cost to Company, Land $ 16,047,022      
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 1,928,600      
Gross Amount Carried at close of period 12/31/2016, Land 16,047,022      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 50,579,563      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 66,626,585      
Accumulated Depreciation (12,285,651)      
Investment in Real Estate Net 54,340,934      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 31,863,038      
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 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 8,822,118      
Gross Amount Carried at close of period 12/31/2016, Land 2,512,500      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 31,434,030      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 33,946,530      
Accumulated Depreciation (23,107,759)      
Investment in Real Estate Net 10,838,771      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 46,464,853      
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 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 561,221      
Gross Amount Carried at close of period 12/31/2016, Land 5,425,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 21,699,249      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 27,124,249      
Accumulated Depreciation (8,325,174)      
Investment in Real Estate Net 18,799,075      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 25,879,145      
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 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 487,960      
Gross Amount Carried at close of period 12/31/2016, Land 10,752,145      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 35,116,075      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 45,868,220      
Accumulated Depreciation (10,739,451)      
Investment in Real Estate Net 35,128,769      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 26,218,004      
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 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 3,432,035      
Gross Amount Carried at close of period 12/31/2016, Land 14,100,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 28,094,918      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 42,194,918      
Accumulated Depreciation (11,624,548)      
Investment in Real Estate Net $ 30,570,370      
Real Estate And Accumulated Depreciation, Encumbrances Reference (J)      
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 153      
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 759,840      
Gross Amount Carried at close of period 12/31/2016, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 42,010,884      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 42,010,884      
Accumulated Depreciation (15,478,760)      
Investment in Real Estate Net 26,532,124      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 24,976,920      
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 264      
Initial Cost to Company, Land $ 13,642,420      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 29,707,475      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,774,728      
Gross Amount Carried at close of period 12/31/2016, Land 13,642,420      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 34,482,203      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 48,124,623      
Accumulated Depreciation (17,151,836)      
Investment in Real Estate Net $ 30,972,787      
Real Estate And Accumulated Depreciation, Encumbrances Reference (J)      
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 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 5,895,100      
Gross Amount Carried at close of period 12/31/2016, Land 5,977,504      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 32,644,211      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 38,621,715      
Accumulated Depreciation (15,657,977)      
Investment in Real Estate Net 22,963,738      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 24,947,516      
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 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 1,647,551      
Gross Amount Carried at close of period 12/31/2016, Land 16,382,822      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 85,464,629      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 101,847,451      
Accumulated Depreciation (23,410,128)      
Investment in Real Estate Net 78,437,323      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 44,696,782      
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 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 4,693,142      
Gross Amount Carried at close of period 12/31/2016, Land 20,880,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 94,948,651      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 115,828,651      
Accumulated Depreciation (38,397,081)      
Investment in Real Estate Net 77,431,570      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 70,777,791      
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 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 1,957,762      
Gross Amount Carried at close of period 12/31/2016, Land 13,740,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 42,715,063      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 56,455,063      
Accumulated Depreciation (16,545,350)      
Investment in Real Estate Net $ 39,909,713      
Real Estate And Accumulated Depreciation, Encumbrances Reference (J)      
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 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 1,040,629      
Gross Amount Carried at close of period 12/31/2016, Land 8,540,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 13,250,610      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 21,790,610      
Accumulated Depreciation (5,406,375)      
Investment in Real Estate Net 16,384,235      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 22,622,379      
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 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 9,258,516      
Gross Amount Carried at close of period 12/31/2016, Land 12,858,693      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 66,427,019      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 79,285,712      
Accumulated Depreciation (30,949,901)      
Investment in Real Estate Net 48,335,811      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 69,242,252      
Moda [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Seattle, WA      
Real Estate And Accumulated Depreciation Units 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 875,933      
Gross Amount Carried at close of period 12/31/2016, Land 12,649,228      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 37,717,945      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 50,367,173      
Accumulated Depreciation (11,291,703)      
Investment in Real Estate Net $ 39,075,470      
Real Estate And Accumulated Depreciation, Encumbrances Reference (L)      
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 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 7,732,818      
Gross Amount Carried at close of period 12/31/2016, Land 8,160,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 37,093,756      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 45,253,756      
Accumulated Depreciation (22,969,702)      
Investment in Real Estate Net $ 22,284,054      
Real Estate And Accumulated Depreciation, Encumbrances Reference (J)      
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 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 813,248      
Gross Amount Carried at close of period 12/31/2016, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 60,394,146      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 60,394,146      
Accumulated Depreciation (17,426,612)      
Investment in Real Estate Net 42,967,534      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 42,327,373      
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 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 3,486,749      
Gross Amount Carried at close of period 12/31/2016, Land 4,000,159      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 97,777,339      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 101,777,498      
Accumulated Depreciation (42,656,500)      
Investment in Real Estate Net $ 59,120,998      
Real Estate And Accumulated Depreciation, Encumbrances Reference (I)      
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 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 8,245,007      
Gross Amount Carried at close of period 12/31/2016, Land 14,752,034      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 81,580,432      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 96,332,466      
Accumulated Depreciation (36,690,596)      
Investment in Real Estate Net 59,641,870      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 49,754,197      
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 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 9,695,764      
Gross Amount Carried at close of period 12/31/2016, Land 71,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 221,602,905      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 293,502,905      
Accumulated Depreciation (39,044,321)      
Investment in Real Estate Net $ 254,458,584      
Real Estate And Accumulated Depreciation, Encumbrances Reference (K)      
Providence [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Bothell, WA      
Real Estate And Accumulated Depreciation Units 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 1,328,617      
Gross Amount Carried at close of period 12/31/2016, Land 3,573,621      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 20,384,122      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 23,957,743      
Accumulated Depreciation (9,481,448)      
Investment in Real Estate Net $ 14,476,295      
Real Estate And Accumulated Depreciation, Encumbrances Reference (I)      
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 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 4,133,203      
Gross Amount Carried at close of period 12/31/2016, Land 10,500,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 56,946,138      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 67,446,138      
Accumulated Depreciation (26,559,665)      
Investment in Real Estate Net $ 40,886,473      
Real Estate And Accumulated Depreciation, Encumbrances Reference (J)      
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 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 2,771,158      
Gross Amount Carried at close of period 12/31/2016, Land 6,500,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 37,356,218      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 43,856,218      
Accumulated Depreciation (17,817,428)      
Investment in Real Estate Net $ 26,038,790      
Real Estate And Accumulated Depreciation, Encumbrances Reference (J)      
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 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 2,674,707      
Gross Amount Carried at close of period 12/31/2016, Land 16,345,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 75,755,377      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 92,100,377      
Accumulated Depreciation (31,075,305)      
Investment in Real Estate Net $ 61,025,072      
Real Estate And Accumulated Depreciation, Encumbrances Reference (I)      
Reserve at Fairfax Corners [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Fairfax, VA      
Real Estate And Accumulated Depreciation Units 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 10,544,380      
Gross Amount Carried at close of period 12/31/2016, Land 15,804,057      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 73,673,431      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 89,477,488      
Accumulated Depreciation (35,713,995)      
Investment in Real Estate Net 53,763,493      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 84,636,440      
Rianna II [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Seattle, WA      
Real Estate And Accumulated Depreciation Units 78      
Initial Cost to Company, Land $ 2,161,840      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 14,433,614      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 335,207      
Gross Amount Carried at close of period 12/31/2016, Land 2,161,840      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 14,768,821      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 16,930,661      
Accumulated Depreciation (4,665,753)      
Investment in Real Estate Net 12,264,908      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 9,179,918      
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 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 6,960,564      
Gross Amount Carried at close of period 12/31/2016, Land 8,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 31,043,588      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 39,943,588      
Accumulated Depreciation (18,827,023)      
Investment in Real Estate Net 21,116,565      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 64,374,172      
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 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 5,142,411      
Gross Amount Carried at close of period 12/31/2016, Land 3,380,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 27,095,274      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 30,475,274      
Accumulated Depreciation (15,457,341)      
Investment in Real Estate Net 15,017,933      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 47,170,890      
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 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 5,784,763      
Gross Amount Carried at close of period 12/31/2016, Land 79,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 183,101,740      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 263,001,740      
Accumulated Depreciation (31,584,442)      
Investment in Real Estate Net $ 231,417,298      
Real Estate And Accumulated Depreciation, Encumbrances Reference (K)      
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 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 18,949      
Gross Amount Carried at close of period 12/31/2016, Land 7,222,544      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 26,296,405      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 33,518,949      
Accumulated Depreciation (3,222,469)      
Investment in Real Estate Net $ 30,296,480      
Real Estate And Accumulated Depreciation, Encumbrances Reference (L)      
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 280      
Initial Cost to Company, Land $ 2,629,804      
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 7,407,026      
Gross Amount Carried at close of period 12/31/2016, Land 2,629,804      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 31,077,915      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 33,707,719      
Accumulated Depreciation (21,189,393)      
Investment in Real Estate Net 12,518,326      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 37,994,251      
Talleyrand [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Tarrytown, NY      
Real Estate And Accumulated Depreciation Units 300      
Initial Cost to Company, Land $ 12,000,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 49,838,160      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 5,280,338      
Gross Amount Carried at close of period 12/31/2016, Land 12,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 55,118,498      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 67,118,498      
Accumulated Depreciation (29,826,719)      
Investment in Real Estate Net 37,291,779      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 34,794,181      
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 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 3,924,692      
Gross Amount Carried at close of period 12/31/2016, Land 28,600,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 65,841,362      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 94,441,362      
Accumulated Depreciation (27,199,505)      
Investment in Real Estate Net 67,241,857      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 39,353,690      
Toscana [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Irvine, CA      
Real Estate And Accumulated Depreciation Units 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 13,015,608      
Gross Amount Carried at close of period 12/31/2016, Land 39,410,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 63,821,680      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 103,231,680      
Accumulated Depreciation (35,049,666)      
Investment in Real Estate Net 68,182,014      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 98,021,589      
Touriel Building [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Berkeley, CA      
Real Estate And Accumulated Depreciation Units 35      
Initial Cost to Company, Land $ 2,736,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 7,810,027      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 178,396      
Gross Amount Carried at close of period 12/31/2016, Land 2,736,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 7,988,423      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 10,724,423      
Accumulated Depreciation (3,056,587)      
Investment in Real Estate Net 7,667,836      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 4,965,054      
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 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 5,090,465      
Gross Amount Carried at close of period 12/31/2016, Land 24,360,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 91,269,179      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 115,629,179      
Accumulated Depreciation (37,802,676)      
Investment in Real Estate Net 77,826,503      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 60,195,391      
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 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 126,527      
Gross Amount Carried at close of period 12/31/2016, Land 42,580,326      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 56,141,201      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 98,721,527      
Accumulated Depreciation (5,287,978)      
Investment in Real Estate Net 93,433,549      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 42,297,038      
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 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 6,676,131      
Gross Amount Carried at close of period 12/31/2016, Land 12,650,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 40,332,423      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 52,982,423      
Accumulated Depreciation (19,770,723)      
Investment in Real Estate Net 33,211,700      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 30,337,321      
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 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 1,443,140      
Gross Amount Carried at close of period 12/31/2016, Land 10,590,975      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 45,852,165      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 56,443,140      
Accumulated Depreciation (14,149,083)      
Investment in Real Estate Net 42,294,057      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 45,950,109      
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 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 651,436      
Gross Amount Carried at close of period 12/31/2016, Land 10,350,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 36,084,873      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 46,434,873      
Accumulated Depreciation (13,516,691)      
Investment in Real Estate Net $ 32,918,182      
Real Estate And Accumulated Depreciation, Encumbrances Reference (J)      
Vintage [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Ontario, CA      
Real Estate And Accumulated Depreciation Units 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 991,090      
Gross Amount Carried at close of period 12/31/2016, Land 7,059,230      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 48,668,852      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 55,728,082      
Accumulated Depreciation (18,740,063)      
Investment in Real Estate Net 36,988,019      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 32,972,257      
Vintage at 425 Broadway (fka Promenade) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Santa Monica, CA      
Real Estate And Accumulated Depreciation Units 58      
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 1,059,233      
Gross Amount Carried at close of period 12/31/2016, Land 9,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 15,020,756      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 24,020,756      
Accumulated Depreciation (2,968,658)      
Investment in Real Estate Net $ 21,052,098      
Real Estate And Accumulated Depreciation, Encumbrances Reference (K)      
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 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 1,803,032      
Gross Amount Carried at close of period 12/31/2016, Land 60,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 49,996,869      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 110,896,869      
Accumulated Depreciation (10,859,764)      
Investment in Real Estate Net 100,037,105      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 47,159,623      
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 480      
Initial Cost to Company, Land $ 22,898,848      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 133,559,573      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,626,531      
Gross Amount Carried at close of period 12/31/2016, Land 22,898,848      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 135,186,104      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 158,084,952      
Accumulated Depreciation (27,829,027)      
Investment in Real Estate Net 130,255,925      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 95,942,439      
Woodleaf [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Campbell, CA      
Real Estate And Accumulated Depreciation Units 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 4,564,556      
Gross Amount Carried at close of period 12/31/2016, Land 8,550,600      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 21,552,739      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 30,103,339      
Accumulated Depreciation (13,279,360)      
Investment in Real Estate Net 16,823,979      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 17,803,590      
Portfolio Entity Encumbrances [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Units      
Initial Cost to Company, Land      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures      
Gross Amount Carried at close of period 12/31/2016, Land      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures      
Accumulated Depreciation      
Investment in Real Estate Net      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 1,645,978,887      
Investment in Real Estate - Wholly Owned Encumbered [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Units 21,196      
Initial Cost to Company, Land $ 1,542,126,523      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 4,432,306,521      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 317,352,468      
Gross Amount Carried at close of period 12/31/2016, Land 1,542,126,523      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 4,749,658,989      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 6,291,785,512      
Accumulated Depreciation (1,497,361,379)      
Investment in Real Estate Net 4,794,424,133      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 3,818,071,013      
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 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 6,364,098      
Gross Amount Carried at close of period 12/31/2016, Land 796,800      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 13,537,823      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 14,334,623      
Accumulated Depreciation (10,501,930)      
Investment in Real Estate Net 3,832,693      
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 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 3,764,545      
Gross Amount Carried at close of period 12/31/2016, Land 4,869,448      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 15,719,609      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 20,589,057      
Accumulated Depreciation (9,906,118)      
Investment in Real Estate Net 10,682,939      
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 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 6,382,976      
Gross Amount Carried at close of period 12/31/2016, Land 6,105,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 35,944,841      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 42,049,841      
Accumulated Depreciation (18,330,095)      
Investment in Real Estate Net 23,719,746      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Harrison Square (fka Elliot Bay) [Domain]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Seattle, WA      
Real Estate And Accumulated Depreciation Units 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 4,889,669      
Gross Amount Carried at close of period 12/31/2016, Land 7,600,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 40,734,014      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 48,334,014      
Accumulated Depreciation (7,462,882)      
Investment in Real Estate Net 40,871,132      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Monterra in Mill Creek [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Mill Creek, WA      
Real Estate And Accumulated Depreciation Units 139      
Initial Cost to Company, Land $ 2,800,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 13,255,123      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 935,693      
Gross Amount Carried at close of period 12/31/2016, Land 2,800,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 14,190,816      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 16,990,816      
Accumulated Depreciation (6,101,965)      
Investment in Real Estate Net 10,888,851      
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 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 3,246,786      
Gross Amount Carried at close of period 12/31/2016, Land 5,460,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 18,968,356      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 24,428,356      
Accumulated Depreciation (11,421,082)      
Investment in Real Estate Net 13,007,274      
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 136      
Initial Cost to Company, Land $ 4,400,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 12,968,002      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 699,374      
Gross Amount Carried at close of period 12/31/2016, Land 4,400,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 13,667,376      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 18,067,376      
Accumulated Depreciation (5,724,191)      
Investment in Real Estate Net 12,343,185      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Via Ventura (CA) (fka Ventura) [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Ventura, CA      
Real Estate And Accumulated Depreciation Units 192      
Initial Cost to Company, Land $ 8,600,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 44,308,202      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 703,519      
Gross Amount Carried at close of period 12/31/2016, Land 8,600,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 45,011,721      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 53,611,721      
Accumulated Depreciation (9,035,652)      
Investment in Real Estate Net 44,576,069      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Wood Creek II (fka Willow Brook (CA))        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Pleasant Hill, CA      
Real Estate And Accumulated Depreciation Units 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 6,380,861      
Gross Amount Carried at close of period 12/31/2016, Land 5,055,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 44,769,533      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 49,824,533      
Accumulated Depreciation (20,343,063)      
Investment in Real Estate Net 29,481,470      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
Investment in Real Estate - Partially Owned Unencumbered [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Units 1,527      
Initial Cost to Company, Land $ 45,686,248      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 209,176,568      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 33,367,521      
Gross Amount Carried at close of period 12/31/2016, Land 45,686,248      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 242,544,089      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 288,230,337      
Accumulated Depreciation (98,826,978)      
Investment in Real Estate Net 189,403,359      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 0      
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 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 5,224,512      
Gross Amount Carried at close of period 12/31/2016, Land 4,507,100      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 17,799,326      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 22,306,426      
Accumulated Depreciation (12,054,134)      
Investment in Real Estate Net 10,252,292      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 16,493,902      
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 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 7,124,649      
Gross Amount Carried at close of period 12/31/2016, Land 5,425,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 25,936,769      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 31,361,769      
Accumulated Depreciation (14,964,999)      
Investment in Real Estate Net 16,396,770      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 28,108,382      
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 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 6,190,412      
Gross Amount Carried at close of period 12/31/2016, Land 6,945,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 29,255,388      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 36,200,388      
Accumulated Depreciation (16,167,257)      
Investment in Real Estate Net 20,033,131      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 36,395,508      
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 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 5,003,636      
Gross Amount Carried at close of period 12/31/2016, Land 5,345,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 25,394,254      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 30,739,254      
Accumulated Depreciation (14,020,421)      
Investment in Real Estate Net 16,718,833      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 28,811,122      
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 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 4,440,120      
Gross Amount Carried at close of period 12/31/2016, Land 4,550,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 22,504,884      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 27,054,884      
Accumulated Depreciation (12,562,453)      
Investment in Real Estate Net 14,492,431      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 26,116,380      
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 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 2,931,955      
Gross Amount Carried at close of period 12/31/2016, Land 3,057,100      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 10,780,573      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 13,837,673      
Accumulated Depreciation (6,893,799)      
Investment in Real Estate Net 6,943,874      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 9,801,248      
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 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 2,761,807      
Gross Amount Carried at close of period 12/31/2016, Land 5,500,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 17,978,420      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 23,478,420      
Accumulated Depreciation (7,925,733)      
Investment in Real Estate Net 15,552,687      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 9,869,581      
Wisconsin Place [Domain]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Chevy Chase, MD      
Real Estate And Accumulated Depreciation Units 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 1,021,679      
Gross Amount Carried at close of period 12/31/2016, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 173,111,034      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 173,111,034      
Accumulated Depreciation (27,622,092)      
Investment in Real Estate Net 145,488,942      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 145,513,689      
Investment in Real Estate - Partially Owned Encumbered [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Units 1,688      
Initial Cost to Company, Land $ 35,329,200      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 288,061,878      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 34,698,770      
Gross Amount Carried at close of period 12/31/2016, Land 35,329,200      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 322,760,648      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 358,089,848      
Accumulated Depreciation (112,210,888)      
Investment in Real Estate Net 245,878,960      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 301,109,812      
Total Consolidated Investment in Real Estate [Member]        
Real Estate And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Units 76,513      
Initial Cost to Company, Land $ 6,100,178,215      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 17,959,193,878      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,327,053,382      
Gross Amount Carried at close of period 12/31/2016, Land 6,100,178,215      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 19,286,247,260      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 25,386,425,475      
Accumulated Depreciation (5,360,389,416)      
Investment in Real Estate Net 20,026,036,059      
SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances $ 4,119,180,825      
Partially Owned Properties – Unconsolidated        
Real Estate And Accumulated Depreciation Abstract        
Partially Owned Properties 2      
Apartment Units 945      
Depreciable Property [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Furniture, fixtures and equipment $ 1,346,300,284      
Building [Member]        
Real Estate And Accumulated Depreciation Abstract        
Property, Plant and Equipment, Estimated Useful Lives 30      
Renovations and Improvements Minimum [Member]        
Real Estate And Accumulated Depreciation Abstract        
Property, Plant and Equipment, Estimated Useful Lives 5      
Renovations and Improvements Maximum [Member]        
Real Estate And Accumulated Depreciation Abstract        
Property, Plant and Equipment, Estimated Useful Lives 15      
Replacements Minimum [Member]        
Real Estate And Accumulated Depreciation Abstract        
Property, Plant and Equipment, Estimated Useful Lives 5      
Replacements Maximum [Member]        
Real Estate And Accumulated Depreciation Abstract        
Property, Plant and Equipment, Estimated Useful Lives 10      
Management Business Renovations and Improvements Minimum [Member] [Member]        
Real Estate And Accumulated Depreciation Abstract        
Property, Plant and Equipment, Estimated Useful Lives 3      
Management Business Renovations and Improvements Maximum [Member] [Member]        
Real Estate And Accumulated Depreciation Abstract        
Property, Plant and Equipment, Estimated Useful Lives 7