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Real Estate and Accumulated Depreciation (Details)
12 Months Ended
Dec. 31, 2015
USD ($)
Dec. 31, 2014
USD ($)
Dec. 31, 2013
USD ($)
Dec. 31, 2012
USD ($)
Real Estate and Accumulated Depreciation [Line Items]        
Furniture, fixtures and equipment $ 1,207,098,000 $ 1,365,276,000    
Land And Depreciable Property Net 17,000,000,000 16,700,000,000    
Real Estates And Accumulated Depreciation Abstract        
Accumulated Depreciation $ (6,084,616,000) $ (5,432,805,000) $ (4,807,709,000) $ (4,912,221,000)
Partially Owned Properties 394      
Number of Units in Real Estate Property 109,652      
Partially Owned Unconsolidated Units 1,281      
Military Housing Properties 2      
Military Housing Units 5,139      
100 K Street [Member]        
Real Estates 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 3,409,415      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2015, Land 15,600,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 3,409,415      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 19,009,415      
Accumulated Depreciation 0      
Investment in Real Estate Net 19,009,415      
Encumbrances $ 0      
170 Amsterdam [Member]        
Real Estates 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 111,609,104      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,648      
Gross Amount Carried at close of period 12/31/2015, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 111,612,752      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 111,612,752      
Accumulated Depreciation (2,550,383)      
Investment in Real Estate Net 109,062,369      
Encumbrances $ 0      
175 Kent [Member]        
Real Estates 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 1,187,580      
Gross Amount Carried at close of period 12/31/2015, Land 22,037,831      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 55,149,749      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 77,187,580      
Accumulated Depreciation (10,449,629)      
Investment in Real Estate Net 66,737,951      
Encumbrances $ 0      
180 Montague (fka Brooklyn Heights) [Member]        
Real Estates 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 1,964,453      
Gross Amount Carried at close of period 12/31/2015, Land 32,400,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 94,639,681      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 127,039,681      
Accumulated Depreciation (13,281,633)      
Investment in Real Estate Net 113,758,048      
Encumbrances $ 0      
1111 Belle Pre (fka The Madison) [Member]        
Real Estates 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 92,822,313      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 109,202      
Gross Amount Carried at close of period 12/31/2015, Land 18,937,702      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 92,931,515      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 111,869,217      
Accumulated Depreciation (8,083,006)      
Investment in Real Estate Net 103,786,211      
Encumbrances $ 0      
1210 Mass [Member]        
Real Estates 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 $ 9,213,512      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 36,559,189      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,158,827      
Gross Amount Carried at close of period 12/31/2015, Land 9,213,512      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 37,718,016      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 46,931,528      
Accumulated Depreciation (14,010,670)      
Investment in Real Estate Net 32,920,858      
Encumbrances $ 0      
1401 E Madison [Member]        
Real Estates 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 $ 10,394,673      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 2,735,646      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2015, Land 10,394,673      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 2,735,646      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 13,130,319      
Accumulated Depreciation 0      
Investment in Real Estate Net 13,130,319      
Encumbrances $ 0      
1500 Mass Ave [Member]        
Real Estates 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 13,920,874      
Gross Amount Carried at close of period 12/31/2015, Land 54,638,298      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 54,282,576      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 108,920,874      
Accumulated Depreciation (18,412,591)      
Investment in Real Estate Net 90,508,283      
Encumbrances $ 0      
1800 Oak (fka Rosslyn) [Member]        
Real Estates 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 2,461,258      
Gross Amount Carried at close of period 12/31/2015, Land 31,400,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 111,466,992      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 142,866,992      
Accumulated Depreciation (15,629,471)      
Investment in Real Estate Net 127,237,521      
Encumbrances $ 0      
200 N Lemon Street [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Anaheim, CA      
Real Estate And Accumulated Depreciation Units 0      
Initial Cost to Company, Land $ 5,865,235      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 3,722,655      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2015, Land 5,865,235      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 3,722,655      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 9,587,890      
Accumulated Depreciation 0      
Investment in Real Estate Net 9,587,890      
Encumbrances $ 0      
204-206 Pine Street/1610 2nd Avenue [Member]        
Real Estates 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 $ 22,323,720      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 73,357,643      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2015, Land 22,323,720      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 73,357,643      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 95,681,363      
Accumulated Depreciation 0      
Investment in Real Estate Net 95,681,363      
Encumbrances $ 0      
2201 Pershing Drive [Member]        
Real Estates 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 2,036,904      
Gross Amount Carried at close of period 12/31/2015, Land 11,321,198      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 51,711,079      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 63,032,277      
Accumulated Depreciation (7,033,954)      
Investment in Real Estate Net 55,998,323      
Encumbrances $ 0      
2201 Wilson [Member]        
Real Estates 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 1,495,753      
Gross Amount Carried at close of period 12/31/2015, Land 21,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 80,220,416      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 102,120,416      
Accumulated Depreciation (11,064,780)      
Investment in Real Estate Net 91,055,636      
Encumbrances $ 0      
2400 M St [Member]        
Real Estates 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 3,650,345      
Gross Amount Carried at close of period 12/31/2015, Land 30,006,593      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 117,664,130      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 147,670,723      
Accumulated Depreciation (41,374,875)      
Investment in Real Estate Net 106,295,848      
Encumbrances $ 0      
315 on A [Member]        
Real Estates 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 169,215      
Gross Amount Carried at close of period 12/31/2015, Land 14,450,070      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 115,994,145      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 130,444,215      
Accumulated Depreciation (6,171,735)      
Investment in Real Estate Net 124,272,480      
Encumbrances $ 0      
340 Fremont [Member]        
Real Estates 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 $ 42,000,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 176,850,680      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2015, Land 42,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 176,850,680      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 218,850,680      
Accumulated Depreciation 0      
Investment in Real Estate Net 218,850,680      
Encumbrances $ 0      
45 Worthington [Member]        
Real Estates 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 1,648,869      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2015, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 1,648,869      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 1,648,869      
Accumulated Depreciation 0      
Investment in Real Estate Net 1,648,869      
Encumbrances $ 0      
Four Hundred And Twenty East Eightieth Street [Member]        
Real Estates 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 4,002,776      
Gross Amount Carried at close of period 12/31/2015, Land 39,277,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 27,029,760      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 66,306,760      
Accumulated Depreciation (11,554,868)      
Investment in Real Estate Net 54,751,892      
Encumbrances $ 0      
425 Mass [Member]        
Real Estates 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 3,574,977      
Gross Amount Carried at close of period 12/31/2015, Land 28,150,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 142,174,977      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 170,324,977      
Accumulated Depreciation (34,957,838)      
Investment in Real Estate Net 135,367,139      
Encumbrances $ 0      
455 I Street [Member]        
Real Estates 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 16,214,611      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2015, Land 12,762,857      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 16,214,611      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 28,977,468      
Accumulated Depreciation 0      
Investment in Real Estate Net 28,977,468      
Encumbrances $ 0      
4885 Edgemoor Lane [Member]        
Real Estates 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 875,185      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2015, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 875,185      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 875,185      
Accumulated Depreciation 0      
Investment in Real Estate Net 875,185      
Encumbrances $ 0      
4th and Hill [Member]        
Real Estates 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 5,642,930      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2015, Land 13,131,456      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 5,642,930      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 18,774,386      
Accumulated Depreciation 0      
Investment in Real Estate Net 18,774,386      
Encumbrances $ 0      
600 Washington [Member]        
Real Estates 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 580,906      
Gross Amount Carried at close of period 12/31/2015, Land 32,852,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 43,721,457      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 76,573,457      
Accumulated Depreciation (16,469,799)      
Investment in Real Estate Net 60,103,658      
Encumbrances $ 0      
660 Washington [Member]        
Real Estates 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 1,378,724      
Gross Amount Carried at close of period 12/31/2015, Land 106,100,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 167,690,403      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 273,790,403      
Accumulated Depreciation (23,978,444)      
Investment in Real Estate Net 249,811,959      
Encumbrances $ 0      
70 Greene [Member]        
Real Estates 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 838,875      
Gross Amount Carried at close of period 12/31/2015, Land 28,108,899      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 237,602,428      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 265,711,327      
Accumulated Depreciation (50,058,634)      
Investment in Real Estate Net 215,652,693      
Encumbrances $ 0      
71 Broadway [Member]        
Real Estates 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 12,183,139      
Gross Amount Carried at close of period 12/31/2015, Land 22,611,600      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 89,675,310      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 112,286,910      
Accumulated Depreciation (35,917,280)      
Investment in Real Estate Net 76,369,630      
Encumbrances $ 0      
77 Bluxome [Member]        
Real Estates 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 175,686      
Gross Amount Carried at close of period 12/31/2015, Land 5,249,124      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 18,785,562      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 24,034,686      
Accumulated Depreciation (3,551,433)      
Investment in Real Estate Net 20,483,253      
Encumbrances $ 0      
777 Sixth [Member]        
Real Estates 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 1,708,867      
Gross Amount Carried at close of period 12/31/2015, Land 65,352,706      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 67,456,161      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 132,808,867      
Accumulated Depreciation (22,000,130)      
Investment in Real Estate Net 110,808,737      
Encumbrances $ 0      
88 Hillside [Member]        
Real Estates 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 1,740,889      
Gross Amount Carried at close of period 12/31/2015, Land 7,786,800      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 33,328,214      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 41,115,014      
Accumulated Depreciation (5,965,778)      
Investment in Real Estate Net 35,149,236      
Encumbrances $ 0      
855 Brannan [Member]        
Real Estates 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 59,118,300      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2015, Land 41,363,921      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 59,118,300      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 100,482,221      
Accumulated Depreciation 0      
Investment in Real Estate Net 100,482,221      
Encumbrances $ 0      
Abington Glen [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Abington, MA      
Real Estate And Accumulated Depreciation Units 90      
Initial Cost to Company, Land $ 553,105      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 3,697,396      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,707,619      
Gross Amount Carried at close of period 12/31/2015, Land 553,105      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 6,405,015      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 6,958,120      
Accumulated Depreciation (4,378,376)      
Investment in Real Estate Net 2,579,744      
Encumbrances $ 0      
Alban Towers [Member]        
Real Estates 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 646,083      
Gross Amount Carried at close of period 12/31/2015, Land 18,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 90,440,284      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 109,340,284      
Accumulated Depreciation (12,554,736)      
Investment in Real Estate Net 96,785,548      
Encumbrances $ 0      
Altitude [Member]        
Real Estates 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 $ 43,783,485      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 110,209,151      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2015, Land 43,783,485      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 110,209,151      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 153,992,636      
Accumulated Depreciation 0      
Investment in Real Estate Net 153,992,636      
Encumbrances $ 0      
Alton, The [Member]        
Real Estates 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 64,366,946      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2015, Land 11,049,027      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 64,366,946      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 75,415,973      
Accumulated Depreciation 0      
Investment in Real Estate Net 75,415,973      
Encumbrances $ 0      
Arbor Terrace [Member]        
Real Estates 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 2,639,125      
Gross Amount Carried at close of period 12/31/2015, Land 9,057,300      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 21,122,767      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 30,180,067      
Accumulated Depreciation (13,158,508)      
Investment in Real Estate Net 17,021,559      
Encumbrances $ 0      
Arboretum (MA) [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Canton, MA      
Real Estate And Accumulated Depreciation Units 156      
Initial Cost to Company, Land $ 4,685,900      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 10,992,751      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,207,099      
Gross Amount Carried at close of period 12/31/2015, Land 4,685,900      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 15,199,850      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 19,885,750      
Accumulated Depreciation (8,869,308)      
Investment in Real Estate Net 11,016,442      
Encumbrances $ 0      
Artisan on Second [Member]        
Real Estates 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 469,032      
Gross Amount Carried at close of period 12/31/2015, Land 8,000,400      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 36,543,632      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 44,544,032      
Accumulated Depreciation (7,896,054)      
Investment in Real Estate Net 36,647,978      
Encumbrances $ 0      
Artistry Emeryville (fka Emeryville) [Member]        
Real Estates 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 1,771,039      
Gross Amount Carried at close of period 12/31/2015, Land 12,300,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 63,237,306      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 75,537,306      
Accumulated Depreciation (9,620,717)      
Investment in Real Estate Net 65,916,589      
Encumbrances $ 0      
Avenue Two [Member]        
Real Estates 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 1,647,581      
Gross Amount Carried at close of period 12/31/2015, Land 7,995,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 19,652,581      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 27,647,581      
Accumulated Depreciation (4,179,196)      
Investment in Real Estate Net 23,468,385      
Encumbrances $ 0      
Azure [Member]        
Real Estates 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 150,600,329      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 629      
Gross Amount Carried at close of period 12/31/2015, Land 32,855,115      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 150,600,958      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 183,456,073      
Accumulated Depreciation (2,077,524)      
Investment in Real Estate Net 181,378,549      
Encumbrances $ 0      
Bay Hill [Member]        
Real Estates 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 1,934,347      
Gross Amount Carried at close of period 12/31/2015, Land 7,600,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 29,371,586      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 36,971,586      
Accumulated Depreciation (11,990,933)      
Investment in Real Estate Net 24,980,653      
Encumbrances $ 0      
Beatrice, The [Member]        
Real Estates 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 676,595      
Gross Amount Carried at close of period 12/31/2015, Land 114,351,405      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 166,325,190      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 280,676,595      
Accumulated Depreciation (29,116,223)      
Investment in Real Estate Net 251,560,372      
Encumbrances $ 0      
Belle Arts Condominium Homes, LLC [Member]        
Real Estates 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 248,929      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures (5,320)      
Gross Amount Carried at close of period 12/31/2015, Land 63,158      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 243,609      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 306,767      
Accumulated Depreciation 0      
Investment in Real Estate Net 306,767      
Encumbrances $ 0      
Bella Fontaine [Member]        
Real Estates 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 473,126      
Gross Amount Carried at close of period 12/31/2015, Land 9,098,808      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 29,174,318      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 38,273,126      
Accumulated Depreciation (5,588,486)      
Investment in Real Estate Net 32,684,640      
Encumbrances $ 0      
Berkeley Land [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Berkeley, CA      
Real Estate And Accumulated Depreciation Units 0      
Initial Cost to Company, Land $ 14,108,910      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 11,357,375      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2015, Land 14,108,910      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 11,357,375      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 25,466,285      
Accumulated Depreciation 0      
Investment in Real Estate Net 25,466,285      
Encumbrances $ 0      
Bradford Apartments [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Newington, CT      
Real Estate And Accumulated Depreciation Units 64      
Initial Cost to Company, Land $ 401,091      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 2,681,210      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 961,845      
Gross Amount Carried at close of period 12/31/2015, Land 401,091      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 3,643,055      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 4,044,146      
Accumulated Depreciation (2,066,615)      
Investment in Real Estate Net 1,977,531      
Encumbrances $ 0      
Breakwater at Marina Del Rey [Member]        
Real Estates 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 649,866      
Gross Amount Carried at close of period 12/31/2015, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 73,839,128      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 73,839,128      
Accumulated Depreciation (11,205,489)      
Investment in Real Estate Net 62,633,639      
Encumbrances $ 0      
Briar Knoll Apts [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Vernon, CT      
Real Estate And Accumulated Depreciation Units 150      
Initial Cost to Company, Land $ 928,972      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 6,209,988      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,633,266      
Gross Amount Carried at close of period 12/31/2015, Land 928,972      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 8,843,254      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 9,772,226      
Accumulated Depreciation (4,794,357)      
Investment in Real Estate Net 4,977,869      
Encumbrances $ 0      
Briarwood (CA) [Member]        
Real Estates 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 3,514,394      
Gross Amount Carried at close of period 12/31/2015, Land 9,991,500      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 25,761,672      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 35,753,172      
Accumulated Depreciation (14,944,409)      
Investment in Real Estate Net 20,808,763      
Encumbrances $ 0      
Bridford Lakes II [Member]        
Real Estates 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 12/31/2015, 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      
Encumbrances $ 0      
Brooklyner (fka 111 Lawrence) [Member]        
Real Estates 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 1,387,079      
Gross Amount Carried at close of period 12/31/2015, Land 40,099,922      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 222,825,710      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 262,925,632      
Accumulated Depreciation (38,804,697)      
Investment in Real Estate Net 224,120,935      
Encumbrances $ 0      
Cambridge Park [Member]        
Real Estates 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 2,123,216      
Gross Amount Carried at close of period 12/31/2015, Land 31,200,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 108,171,803      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 139,371,803      
Accumulated Depreciation (15,523,923)      
Investment in Real Estate Net 123,847,880      
Encumbrances $ 0      
Carlyle Mill [Member]        
Real Estates 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 7,134,848      
Gross Amount Carried at close of period 12/31/2015, Land 10,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 58,502,761      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 68,502,761      
Accumulated Depreciation (26,086,693)      
Investment in Real Estate Net 42,416,068      
Encumbrances $ 0      
Cascade [Domain]        
Real Estates 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 43,951,916      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2015, Land 23,751,564      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 43,951,916      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 67,703,480      
Accumulated Depreciation 0      
Investment in Real Estate Net 67,703,480      
Encumbrances $ 0      
Centennial (fka Centennial Court & Centennial Tower) [Member]        
Real Estates 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 8,150,667      
Gross Amount Carried at close of period 12/31/2015, Land 9,700,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 78,231,045      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 87,931,045      
Accumulated Depreciation (30,555,738)      
Investment in Real Estate Net 57,375,307      
Encumbrances $ 0      
Centre Club Combined [Member]        
Real Estates 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 6,071,471      
Gross Amount Carried at close of period 12/31/2015, Land 7,436,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 39,086,260      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 46,522,260      
Accumulated Depreciation (20,011,745)      
Investment in Real Estate Net 26,510,515      
Encumbrances $ 0      
Church Corner [Member]        
Real Estates 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 2,021,207      
Gross Amount Carried at close of period 12/31/2015, Land 5,220,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 18,765,850      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 23,985,850      
Accumulated Depreciation (7,784,093)      
Investment in Real Estate Net 16,201,757      
Encumbrances $ 0      
City Gate at Cupertino (fka Cupertino) [Member]        
Real Estates 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 3,164,548      
Gross Amount Carried at close of period 12/31/2015, Land 40,400,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 99,101,594      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 139,501,594      
Accumulated Depreciation (13,831,042)      
Investment in Real Estate Net 125,670,552      
Encumbrances $ 0      
City Pointe [Member]        
Real Estates 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 799,333      
Gross Amount Carried at close of period 12/31/2015, Land 6,863,792      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 37,275,541      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 44,139,333      
Accumulated Depreciation (10,525,198)      
Investment in Real Estate Net 33,614,135      
Encumbrances $ 0      
City Square Bellevue (fka Bellevue) [Member]        
Real Estates 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 2,633,430      
Gross Amount Carried at close of period 12/31/2015, Land 15,100,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 44,509,687      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 59,609,687      
Accumulated Depreciation (6,132,286)      
Investment in Real Estate Net 53,477,401      
Encumbrances $ 0      
Clarendon, The [Member]        
Real Estates 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 2,066,458      
Gross Amount Carried at close of period 12/31/2015, Land 30,400,340      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 105,891,118      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 136,291,458      
Accumulated Depreciation (22,819,650)      
Investment in Real Estate Net 113,471,808      
Encumbrances $ 0      
Cleo, The [Member]        
Real Estates 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 3,799,207      
Gross Amount Carried at close of period 12/31/2015, Land 6,615,467      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 18,628,542      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 25,244,009      
Accumulated Depreciation (7,638,498)      
Investment in Real Estate Net 17,605,511      
Encumbrances $ 0      
Corcoran House at DuPont Circle (fka DuPont Circle) [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Washington, D.C.      
Real Estate And Accumulated Depreciation Units 137      
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 1,352,210      
Gross Amount Carried at close of period 12/31/2015, Land 13,500,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 28,265,323      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 41,765,323      
Accumulated Depreciation (4,701,324)      
Investment in Real Estate Net 37,063,999      
Encumbrances $ 0      
Courthouse Plaza [Member]        
Real Estates 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 3,941,196      
Gross Amount Carried at close of period 12/31/2015, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 91,327,220      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 91,327,220      
Accumulated Depreciation (14,489,207)      
Investment in Real Estate Net 76,838,013      
Encumbrances $ 0      
Creekside (San Mateo) [Member]        
Real Estates 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 21,193,232      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,681,274      
Gross Amount Carried at close of period 12/31/2015, Land 9,606,600      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 24,874,506      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 34,481,106      
Accumulated Depreciation (14,783,421)      
Investment in Real Estate Net 19,697,685      
Encumbrances $ 0      
Cronins Landing [Member]        
Real Estates 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 3,008,274      
Gross Amount Carried at close of period 12/31/2015, Land 32,300,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 88,127,598      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 120,427,598      
Accumulated Depreciation (12,711,972)      
Investment in Real Estate Net 107,715,626      
Encumbrances $ 0      
Crystal Place [Member]        
Real Estates 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 2,609,270      
Gross Amount Carried at close of period 12/31/2015, Land 17,200,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 50,528,245      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 67,728,245      
Accumulated Depreciation (7,196,001)      
Investment in Real Estate Net 60,532,244      
Encumbrances $ 0      
Dean Estates [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Taunton, MA      
Real Estate And Accumulated Depreciation Units 58      
Initial Cost to Company, Land $ 498,080      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 3,329,560      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 840,538      
Gross Amount Carried at close of period 12/31/2015, Land 498,080      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 4,170,098      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 4,668,178      
Accumulated Depreciation (2,431,087)      
Investment in Real Estate Net 2,237,091      
Encumbrances $ 0      
Eagle Canyon [Member]        
Real Estates 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 8,358,167      
Gross Amount Carried at close of period 12/31/2015, Land 1,808,900      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 24,632,528      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 26,441,428      
Accumulated Depreciation (16,229,794)      
Investment in Real Estate Net 10,211,634      
Encumbrances $ 0      
Edgemont at Bethesda Metro [Member]        
Real Estates 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 947,391      
Gross Amount Carried at close of period 12/31/2015, Land 13,092,552      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 44,854,839      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 57,947,391      
Accumulated Depreciation (8,612,518)      
Investment in Real Estate Net 49,334,873      
Encumbrances $ 0      
Elevé [Member]        
Real Estates 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 186,855      
Gross Amount Carried at close of period 12/31/2015, Land 14,080,560      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 56,606,295      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 70,686,855      
Accumulated Depreciation (5,258,108)      
Investment in Real Estate Net 65,428,747      
Encumbrances $ 0      
Emerson Place [Member]        
Real Estates 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 18,997,536      
Gross Amount Carried at close of period 12/31/2015, Land 14,855,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 76,564,172      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 91,419,172      
Accumulated Depreciation (49,539,039)      
Investment in Real Estate Net 41,880,133      
Encumbrances $ 0      
Encinitas Heights (fka Encinitas) [Member]        
Real Estates 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 294,376      
Gross Amount Carried at close of period 12/31/2015, Land 12,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 29,501,873      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 41,501,873      
Accumulated Depreciation (4,700,031)      
Investment in Real Estate Net 36,801,842      
Encumbrances $ 0      
Encore at Sherman Oaks, The [Member]        
Real Estates 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 1,110,902      
Gross Amount Carried at close of period 12/31/2015, Land 8,700,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 26,556,905      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 35,256,905      
Accumulated Depreciation (6,547,074)      
Investment in Real Estate Net 28,709,831      
Encumbrances $ 0      
Fountains at Emerald Park (fka Emerald Park) [Member]        
Real Estates 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 742,760      
Gross Amount Carried at close of period 12/31/2015, Land 25,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 84,728,977      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 110,628,977      
Accumulated Depreciation (12,566,319)      
Investment in Real Estate Net 98,062,658      
Encumbrances $ 0      
Fox Hill Apartments [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Enfield, CT      
Real Estate And Accumulated Depreciation Units 168      
Initial Cost to Company, Land $ 1,129,018      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 7,547,256      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,297,171      
Gross Amount Carried at close of period 12/31/2015, Land 1,129,018      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 9,844,427      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 10,973,445      
Accumulated Depreciation (5,478,777)      
Investment in Real Estate Net 5,494,668      
Encumbrances $ 0      
Fremont Center [Member]        
Real Estates 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 1,392,624      
Gross Amount Carried at close of period 12/31/2015, Land 25,800,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 80,145,738      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 105,945,738      
Accumulated Depreciation (11,547,488)      
Investment in Real Estate Net 94,398,250      
Encumbrances $ 0      
Gallery, The [Member]        
Real Estates 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 2,495,809      
Gross Amount Carried at close of period 12/31/2015, Land 18,144,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 49,063,750      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 67,207,750      
Accumulated Depreciation (18,185,915)      
Investment in Real Estate Net 49,021,835      
Encumbrances $ 0      
Gateway at Malden Center [Member]        
Real Estates 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 13,139,391      
Gross Amount Carried at close of period 12/31/2015, Land 9,209,780      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 38,862,057      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 48,071,837      
Accumulated Depreciation (19,457,428)      
Investment in Real Estate Net 28,614,409      
Encumbrances $ 0      
Geary Court Yard [Member]        
Real Estates 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 4,137,461      
Gross Amount Carried at close of period 12/31/2015, Land 1,722,400      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 19,608,890      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 21,331,290      
Accumulated Depreciation (11,745,089)      
Investment in Real Estate Net 9,586,201      
Encumbrances $ 0      
Glen Meadow [Member]        
Real Estates 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 $ 2,339,330      
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 4,187,941      
Gross Amount Carried at close of period 12/31/2015, Land 2,339,330      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 20,321,529      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 22,660,859      
Accumulated Depreciation (12,098,366)      
Investment in Real Estate Net 10,562,493      
Encumbrances $ 0      
Greenfield Village [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Rocky Hill , CT      
Real Estate And Accumulated Depreciation Units 151      
Initial Cost to Company, Land $ 911,534      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 6,093,418      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 827,545      
Gross Amount Carried at close of period 12/31/2015, Land 911,534      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 6,920,963      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 7,832,497      
Accumulated Depreciation (3,865,157)      
Investment in Real Estate Net 3,967,340      
Encumbrances $ 0      
Hampshire Place [Member]        
Real Estates 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 3,646,785      
Gross Amount Carried at close of period 12/31/2015, Land 10,806,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 33,982,115      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 44,788,115      
Accumulated Depreciation (14,251,207)      
Investment in Real Estate Net 30,536,908      
Encumbrances $ 0      
Harbor Steps [Member]        
Real Estates 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 15,887,513      
Gross Amount Carried at close of period 12/31/2015, Land 59,387,158      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 174,716,945      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 234,104,103      
Accumulated Depreciation (66,524,689)      
Investment in Real Estate Net 167,579,414      
Encumbrances $ 0      
Heritage at Stone Ridge [Member]        
Real Estates 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 1,471,640      
Gross Amount Carried at close of period 12/31/2015, Land 10,800,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 33,279,975      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 44,079,975      
Accumulated Depreciation (12,980,415)      
Investment in Real Estate Net 31,099,560      
Encumbrances $ 0      
Heritage Ridge [Member]        
Real Estates 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 1,006,685      
Gross Amount Carried at close of period 12/31/2015, Land 6,895,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 19,990,282      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 26,885,282      
Accumulated Depreciation (8,656,120)      
Investment in Real Estate Net 18,229,162      
Encumbrances $ 0      
Heron Pointe [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Boynton Beach, FL      
Real Estate And Accumulated Depreciation Units 192      
Initial Cost to Company, Land $ 1,546,700      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 7,774,676      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,626,877      
Gross Amount Carried at close of period 12/31/2015, Land 1,546,700      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 10,401,553      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 11,948,253      
Accumulated Depreciation (7,058,305)      
Investment in Real Estate Net 4,889,948      
Encumbrances $ 0      
Hesby [Member]        
Real Estates 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 203,388      
Gross Amount Carried at close of period 12/31/2015, Land 23,299,892      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 102,903,496      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 126,203,388      
Accumulated Depreciation (9,214,042)      
Investment in Real Estate Net 116,989,346      
Encumbrances $ 0      
High Meadow [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Ellington, CT      
Real Estate And Accumulated Depreciation Units 100      
Initial Cost to Company, Land $ 583,679      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 3,901,774      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,342,073      
Gross Amount Carried at close of period 12/31/2015, Land 583,679      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 5,243,847      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 5,827,526      
Accumulated Depreciation (2,886,630)      
Investment in Real Estate Net 2,940,896      
Encumbrances $ 0      
Highland Glen [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Westwood, MA      
Real Estate And Accumulated Depreciation Units 180      
Initial Cost to Company, Land $ 2,229,095      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 16,828,153      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,895,346      
Gross Amount Carried at close of period 12/31/2015, Land 2,229,095      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 19,723,499      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 21,952,594      
Accumulated Depreciation (10,982,160)      
Investment in Real Estate Net 10,970,434      
Encumbrances $ 0      
Highland Glen II [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Westwood, MA      
Real Estate And Accumulated Depreciation Units 102      
Initial Cost to Company, Land $ 0      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 19,875,857      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 203,172      
Gross Amount Carried at close of period 12/31/2015, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 20,079,029      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 20,079,029      
Accumulated Depreciation (6,387,155)      
Investment in Real Estate Net 13,691,874      
Encumbrances $ 0      
Highlands at Cherry Hill [Member]        
Real Estates 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 1,058,592      
Gross Amount Carried at close of period 12/31/2015, Land 6,800,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 22,517,700      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 29,317,700      
Accumulated Depreciation (8,801,180)      
Investment in Real Estate Net 20,516,520      
Encumbrances $ 0      
Highlands At South Plainfield [Member]        
Real Estates 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 1,313,527      
Gross Amount Carried at close of period 12/31/2015, Land 10,080,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 38,840,439      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 48,920,439      
Accumulated Depreciation (14,496,059)      
Investment in Real Estate Net 34,424,380      
Encumbrances $ 0      
Hikari [Member]        
Real Estates 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 494,697      
Gross Amount Carried at close of period 12/31/2015, Land 9,435,760      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 33,058,937      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 42,494,697      
Accumulated Depreciation (6,882,542)      
Investment in Real Estate Net 35,612,155      
Encumbrances $ 0      
Hudson Crossing [Member]        
Real Estates 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 2,026,803      
Gross Amount Carried at close of period 12/31/2015, Land 23,420,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 72,004,502      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 95,424,502      
Accumulated Depreciation (28,426,002)      
Investment in Real Estate Net 66,998,500      
Encumbrances $ 0      
Hudson Crossing II [Member]        
Real Estates 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 $ 10,599,286      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 2,025,249      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2015, Land 10,599,286      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 2,025,249      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 12,624,535      
Accumulated Depreciation 0      
Investment in Real Estate Net 12,624,535      
Encumbrances $ 0      
Hudson Pointe [Member]        
Real Estates 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 3,378,496      
Gross Amount Carried at close of period 12/31/2015, Land 5,350,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 44,492,570      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 49,842,570      
Accumulated Depreciation (18,501,842)      
Investment in Real Estate Net 31,340,728      
Encumbrances $ 0      
Hunt Club II [Member]        
Real Estates 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 12/31/2015, 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      
Encumbrances $ 0      
Ivory Wood [Member]        
Real Estates 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 874,464      
Gross Amount Carried at close of period 12/31/2015, Land 2,732,800      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 14,762,746      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 17,495,546      
Accumulated Depreciation (6,352,195)      
Investment in Real Estate Net 11,143,351      
Encumbrances $ 0      
Jia [Member]        
Real Estates 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 76,010,218      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 115,966      
Gross Amount Carried at close of period 12/31/2015, Land 14,791,831      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 76,126,184      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 90,918,015      
Accumulated Depreciation (7,438,023)      
Investment in Real Estate Net 83,479,992      
Encumbrances $ 0      
Junction 47 (fka West Seattle) [Member]        
Real Estates 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 54,388,245      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 45      
Gross Amount Carried at close of period 12/31/2015, Land 11,726,305      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 54,388,290      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 66,114,595      
Accumulated Depreciation (684,861)      
Investment in Real Estate Net 65,429,734      
Encumbrances $ 0      
Kelvin, The [Member]        
Real Estates 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 10,657      
Gross Amount Carried at close of period 12/31/2015, Land 15,521,552      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 64,864,105      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 80,385,657      
Accumulated Depreciation (1,340,371)      
Investment in Real Estate Net 79,045,286      
Encumbrances $ 0      
Kendall Square II [Member]        
Real Estates 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 1,105,465      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2015, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 1,105,465      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 1,105,465      
Accumulated Depreciation 0      
Investment in Real Estate Net 1,105,465      
Encumbrances $ 0      
Landings at Port Imperial [Member]        
Real Estates 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 7,917,500      
Gross Amount Carried at close of period 12/31/2015, Land 27,246,045      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 45,658,550      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 72,904,595      
Accumulated Depreciation (25,157,567)      
Investment in Real Estate Net 47,747,028      
Encumbrances $ 0      
Lincoln Heights [Member]        
Real Estates 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 12,316,194      
Gross Amount Carried at close of period 12/31/2015, Land 5,928,400      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 45,911,456      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 51,839,856      
Accumulated Depreciation (29,948,038)      
Investment in Real Estate Net 21,891,818      
Encumbrances $ 0      
Lindley Apartments [Member]        
Real Estates 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 797,056      
Gross Amount Carried at close of period 12/31/2015, Land 5,805,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 26,502,056      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 32,307,056      
Accumulated Depreciation (6,457,391)      
Investment in Real Estate Net 25,849,665      
Encumbrances $ 0      
Loft 590 [Member]        
Real Estates 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 291,850      
Gross Amount Carried at close of period 12/31/2015, Land 20,100,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 68,200,873      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 88,300,873      
Accumulated Depreciation (9,179,835)      
Investment in Real Estate Net 79,121,038      
Encumbrances $ 0      
Lofts at Kendall Square (fka Kendall Square) [Member]        
Real Estates 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 4,174,184      
Gross Amount Carried at close of period 12/31/2015, Land 23,300,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 82,619,841      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 105,919,841      
Accumulated Depreciation (11,149,971)      
Investment in Real Estate Net 94,769,870      
Encumbrances $ 0      
Longacre House [Member]        
Real Estates 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 1,449,025      
Gross Amount Carried at close of period 12/31/2015, Land 73,170,045      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 55,411,535      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 128,581,580      
Accumulated Depreciation (19,189,340)      
Investment in Real Estate Net 109,392,240      
Encumbrances $ 0      
Longfellow Place [Member]        
Real Estates 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 153,899,994      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 73,147,489      
Gross Amount Carried at close of period 12/31/2015, Land 47,096,917      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 227,047,483      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 274,144,400      
Accumulated Depreciation (129,782,488)      
Investment in Real Estate Net 144,361,912      
Encumbrances $ 0      
Mantena [Member]        
Real Estates 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 492,732      
Gross Amount Carried at close of period 12/31/2015, Land 22,346,513      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 61,993,890      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 84,340,403      
Accumulated Depreciation (9,234,987)      
Investment in Real Estate Net 75,105,416      
Encumbrances $ 0      
Marina 41 (fka Marina Del Rey) [Member]        
Real Estates 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 4,909,098      
Gross Amount Carried at close of period 12/31/2015, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 173,751,540      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 173,751,540      
Accumulated Depreciation (27,415,993)      
Investment in Real Estate Net 146,335,547      
Encumbrances $ 0      
Mariposa at Playa Del Rey (fka Playa Del Rey) [Member]        
Real Estates 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 4,016,502      
Gross Amount Carried at close of period 12/31/2015, Land 60,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 93,327,984      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 154,227,984      
Accumulated Depreciation (13,774,366)      
Investment in Real Estate Net 140,453,618      
Encumbrances $ 0      
Milano Lofts [Member]        
Real Estates 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 381,581      
Gross Amount Carried at close of period 12/31/2015, Land 8,125,216      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 27,760,365      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 35,885,581      
Accumulated Depreciation (4,712,661)      
Investment in Real Estate Net 31,172,920      
Encumbrances $ 0      
Monte Viejo [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Phoenix, AZ      
Real Estate And Accumulated Depreciation Units 480      
Initial Cost to Company, Land $ 12,700,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 45,926,784      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,757,827      
Gross Amount Carried at close of period 12/31/2015, Land 12,700,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 47,684,611      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 60,384,611      
Accumulated Depreciation (19,906,193)      
Investment in Real Estate Net 40,478,418      
Encumbrances $ 0      
Mountain View Redevelopment [Member]        
Real Estates 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 6,539      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2015, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 6,539      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 6,539      
Accumulated Depreciation 0      
Investment in Real Estate Net 6,539      
Encumbrances $ 0      
Mozaic at Union Station [Member]        
Real Estates 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 1,554,378      
Gross Amount Carried at close of period 12/31/2015, Land 8,500,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 54,083,824      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 62,583,824      
Accumulated Depreciation (18,494,933)      
Investment in Real Estate Net 44,088,891      
Encumbrances $ 0      
Murray Hill Tower (fka Murray Hill) [Member]        
Real Estates 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 3,764,623      
Gross Amount Carried at close of period 12/31/2015, Land 75,800,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 106,470,024      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 182,270,024      
Accumulated Depreciation (17,676,937)      
Investment in Real Estate Net 164,593,087      
Encumbrances $ 0      
Northglen [Member]        
Real Estates 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 2,259,421      
Gross Amount Carried at close of period 12/31/2015, Land 9,360,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 23,037,974      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 32,397,974      
Accumulated Depreciation (12,381,522)      
Investment in Real Estate Net 20,016,452      
Encumbrances $ 0      
Northpark [Member]        
Real Estates 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 11,916,802      
Gross Amount Carried at close of period 12/31/2015, Land 38,607,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 89,389,019      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 127,996,019      
Accumulated Depreciation (25,399,200)      
Investment in Real Estate Net 102,596,819      
Encumbrances $ 0      
Northridge [Member]        
Real Estates 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 $ 5,527,800      
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 10,416,100      
Gross Amount Carried at close of period 12/31/2015, Land 5,527,800      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 25,107,805      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 30,635,605      
Accumulated Depreciation (16,166,627)      
Investment in Real Estate Net 14,468,978      
Encumbrances $ 0      
Oak Park Combined [Member]        
Real Estates 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 9,019,341      
Gross Amount Carried at close of period 12/31/2015, Land 3,390,700      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 39,536,615      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 42,927,315      
Accumulated Depreciation (27,064,200)      
Investment in Real Estate Net 15,863,115      
Encumbrances $ 0      
Oakwood Boston [Member]        
Real Estates 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 1,262,957      
Gross Amount Carried at close of period 12/31/2015, Land 22,200,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 29,935,936      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 52,135,936      
Accumulated Depreciation (4,761,170)      
Investment in Real Estate Net 47,374,766      
Encumbrances $ 0      
Oakwood Crystal City [Member]        
Real Estates 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 747,540      
Gross Amount Carried at close of period 12/31/2015, Land 15,400,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 36,221,876      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 51,621,876      
Accumulated Depreciation (5,451,482)      
Investment in Real Estate Net 46,170,394      
Encumbrances $ 0      
Oakwood Marina Del Rey [Member]        
Real Estates 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 2,191,084      
Gross Amount Carried at close of period 12/31/2015, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 122,986,443      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 122,986,443      
Accumulated Depreciation (19,217,166)      
Investment in Real Estate Net 103,769,277      
Encumbrances $ 0      
Ocean Crest [Member]        
Real Estates 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 3,243,097      
Gross Amount Carried at close of period 12/31/2015, Land 5,111,200      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 15,153,535      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 20,264,735      
Accumulated Depreciation (9,238,961)      
Investment in Real Estate Net 11,025,774      
Encumbrances $ 0      
Odin (fka Tallman) [Member]        
Real Estates 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 63,101,811      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 241      
Gross Amount Carried at close of period 12/31/2015, Land 16,807,519      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 63,102,052      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 79,909,571      
Accumulated Depreciation (623,866)      
Investment in Real Estate Net 79,285,705      
Encumbrances $ 0      
Old Town Lofts [Member]        
Real Estates 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 159,751      
Gross Amount Carried at close of period 12/31/2015, Land 7,740,467      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 44,305,932      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 52,046,399      
Accumulated Depreciation (734,373)      
Investment in Real Estate Net 51,312,026      
Encumbrances $ 0      
One Henry Adams [Member]        
Real Estates 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 $ 30,224,393      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 59,682,378      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2015, Land 30,224,393      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 59,682,378      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 89,906,771      
Accumulated Depreciation 0      
Investment in Real Estate Net 89,906,771      
Encumbrances $ 0      
Pacific Place [Member]        
Real Estates 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 989,768      
Gross Amount Carried at close of period 12/31/2015, Land 32,250,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 111,739,768      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 143,989,768      
Accumulated Depreciation (13,998,683)      
Investment in Real Estate Net 129,991,085      
Encumbrances $ 0      
Parc 77 [Member]        
Real Estates 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 5,558,590      
Gross Amount Carried at close of period 12/31/2015, Land 40,504,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 23,584,269      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 64,088,269      
Accumulated Depreciation (10,342,724)      
Investment in Real Estate Net 53,745,545      
Encumbrances $ 0      
Parc Cameron [Member]        
Real Estates 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 6,604,055      
Gross Amount Carried at close of period 12/31/2015, Land 37,600,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 16,459,652      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 54,059,652      
Accumulated Depreciation (8,709,483)      
Investment in Real Estate Net 45,350,169      
Encumbrances $ 0      
Parc Coliseum [Member]        
Real Estates 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 8,549,855      
Gross Amount Carried at close of period 12/31/2015, Land 52,654,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 31,595,606      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 84,249,606      
Accumulated Depreciation (14,193,545)      
Investment in Real Estate Net 70,056,061      
Encumbrances $ 0      
Parc East Towers [Member]        
Real Estates 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 8,398,427      
Gross Amount Carried at close of period 12/31/2015, Land 102,163,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 117,387,829      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 219,550,829      
Accumulated Depreciation (40,021,695)      
Investment in Real Estate Net 179,529,134      
Encumbrances $ 0      
Parc on Powell (fka Parkside at Emeryville) [Member]        
Real Estates 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 66,308,322      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,993      
Gross Amount Carried at close of period 12/31/2015, Land 16,667,059      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 66,313,315      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 82,980,374      
Accumulated Depreciation (1,386,523)      
Investment in Real Estate Net 81,593,851      
Encumbrances $ 0      
Park at Pentagon Row (fka Pentagon City) [Member]        
Real Estates 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 700,661      
Gross Amount Carried at close of period 12/31/2015, Land 28,300,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 79,538,845      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 107,838,845      
Accumulated Depreciation (11,504,796)      
Investment in Real Estate Net 96,334,049      
Encumbrances $ 0      
Park Connecticut [Member]        
Real Estates 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 757,785      
Gross Amount Carried at close of period 12/31/2015, Land 13,700,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 59,845,304      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 73,545,304      
Accumulated Depreciation (8,000,115)      
Investment in Real Estate Net 65,545,189      
Encumbrances $ 0      
Park Hacienda (fka Hacienda) [Member]        
Real Estates 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 774,074      
Gross Amount Carried at close of period 12/31/2015, Land 43,200,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 129,527,433      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 172,727,433      
Accumulated Depreciation (19,900,917)      
Investment in Real Estate Net 152,826,516      
Encumbrances $ 0      
Park West (CA) [Member]        
Real Estates 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 9,419,065      
Gross Amount Carried at close of period 12/31/2015, Land 3,033,500      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 36,721,448      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 39,754,948      
Accumulated Depreciation (24,776,986)      
Investment in Real Estate Net 14,977,962      
Encumbrances $ 0      
Parkside [Member]        
Real Estates 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 3,981,119      
Gross Amount Carried at close of period 12/31/2015, Land 6,246,700      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 15,808,572      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 22,055,272      
Accumulated Depreciation (10,527,862)      
Investment in Real Estate Net 11,527,410      
Encumbrances $ 0      
Pearl, The [Member]        
Real Estates 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 0      
Gross Amount Carried at close of period 12/31/2015, Land 6,972,585      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 26,527,415      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 33,500,000      
Accumulated Depreciation 0      
Investment in Real Estate Net 33,500,000      
Encumbrances $ 0      
Pegasus [Member]        
Real Estates 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 2,764,585      
Gross Amount Carried at close of period 12/31/2015, Land 18,094,052      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 84,670,533      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 102,764,585      
Accumulated Depreciation (19,826,265)      
Investment in Real Estate Net 82,938,320      
Encumbrances $ 0      
Phillips Park [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Wellesley, MA      
Real Estate And Accumulated Depreciation Units 49      
Initial Cost to Company, Land $ 816,922      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 5,460,955      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,157,352      
Gross Amount Carried at close of period 12/31/2015, Land 816,922      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 6,618,307      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 7,435,229      
Accumulated Depreciation (3,766,443)      
Investment in Real Estate Net 3,668,786      
Encumbrances $ 0      
Playa Pacifica [Member]        
Real Estates 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 12,699,944      
Gross Amount Carried at close of period 12/31/2015, Land 35,100,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 46,173,766      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 81,273,766      
Accumulated Depreciation (19,897,231)      
Investment in Real Estate Net 61,376,535      
Encumbrances $ 0      
Portofino [Member]        
Real Estates 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 3,510,897      
Gross Amount Carried at close of period 12/31/2015, Land 3,572,400      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 18,171,891      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 21,744,291      
Accumulated Depreciation (11,352,508)      
Investment in Real Estate Net 10,391,783      
Encumbrances $ 0      
Portofino (Val) [Member]        
Real Estates 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 3,296,844      
Gross Amount Carried at close of period 12/31/2015, Land 8,640,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 24,783,970      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 33,423,970      
Accumulated Depreciation (13,318,844)      
Investment in Real Estate Net 20,105,126      
Encumbrances $ 0      
Portside Towers [Member]        
Real Estates 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 19,873,490      
Gross Amount Carried at close of period 12/31/2015, Land 22,487,006      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 116,716,403      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 139,203,409      
Accumulated Depreciation (71,088,414)      
Investment in Real Estate Net 68,114,995      
Encumbrances $ 0      
Potrero 1010 [Member]        
Real Estates 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 $ 40,830,011      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 133,910,937      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2015, Land 40,830,011      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 133,910,937      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 174,740,948      
Accumulated Depreciation 0      
Investment in Real Estate Net 174,740,948      
Encumbrances $ 0      
Prado (fka Glendale) [Member]        
Real Estates 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 2,061,951      
Gross Amount Carried at close of period 12/31/2015, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 70,039,264      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 70,039,264      
Accumulated Depreciation (9,953,439)      
Investment in Real Estate Net 60,085,825      
Encumbrances $ 0      
Prime, The [Member]        
Real Estates 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 1,301,267      
Gross Amount Carried at close of period 12/31/2015, Land 32,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 65,737,806      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 97,737,806      
Accumulated Depreciation (23,364,019)      
Investment in Real Estate Net 74,373,787      
Encumbrances $ 0      
Prism at Park Avenue South (fka 400 Park Aveue South (EQR)) [Member]        
Real Estates 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 163,700,126      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2015, Land 76,292,169      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 163,700,126      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 239,992,295      
Accumulated Depreciation (5,492,140)      
Investment in Real Estate Net 234,500,155      
Encumbrances $ 0      
Promenade at Town Center I & II [Member]        
Real Estates 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 5,471,517      
Gross Amount Carried at close of period 12/31/2015, Land 28,200,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 75,267,432      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 103,467,432      
Accumulated Depreciation (33,050,350)      
Investment in Real Estate Net 70,417,082      
Encumbrances $ 0      
Quarry Hills [Member]        
Real Estates 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 813,007      
Gross Amount Carried at close of period 12/31/2015, Land 26,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 85,224,169      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 112,124,169      
Accumulated Depreciation (12,835,782)      
Investment in Real Estate Net 99,288,387      
Encumbrances $ 0      
Red 160 (fka Redmond Way) [Member]        
Real Estates 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 872,804      
Gross Amount Carried at close of period 12/31/2015, Land 15,546,376      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 66,192,814      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 81,739,190      
Accumulated Depreciation (11,437,349)      
Investment in Real Estate Net 70,301,841      
Encumbrances $ 0      
Redmond Court [Member]        
Real Estates 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 722,527      
Gross Amount Carried at close of period 12/31/2015, Land 10,300,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 34,211,272      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 44,511,272      
Accumulated Depreciation (5,429,653)      
Investment in Real Estate Net 39,081,619      
Encumbrances $ 0      
Regency Palms [Member]        
Real Estates 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 5,591,340      
Gross Amount Carried at close of period 12/31/2015, Land 1,857,400      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 22,304,594      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 24,161,994      
Accumulated Depreciation (15,853,559)      
Investment in Real Estate Net 8,308,435      
Encumbrances $ 0      
Renaissance Villas [Member]        
Real Estates 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 148,126      
Gross Amount Carried at close of period 12/31/2015, Land 2,458,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 4,690,126      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 7,148,126      
Accumulated Depreciation (1,571,899)      
Investment in Real Estate Net 5,576,227      
Encumbrances $ 0      
Reserve at Mountain View (fka Mountain View) [Member]        
Real Estates 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 2,601,273      
Gross Amount Carried at close of period 12/31/2015, Land 27,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 35,630,878      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 62,630,878      
Accumulated Depreciation (5,569,705)      
Investment in Real Estate Net 57,061,173      
Encumbrances $ 0      
Reserve at Potomac Yard [Member]        
Real Estates 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 7,339,599      
Gross Amount Carried at close of period 12/31/2015, Land 11,918,917      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 76,202,240      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 88,121,157      
Accumulated Depreciation (31,804,125)      
Investment in Real Estate Net 56,317,032      
Encumbrances $ 0      
Reserve at Town Center I-III (WA) [Member]        
Real Estates 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 2,678,501      
Gross Amount Carried at close of period 12/31/2015, Land 16,769,205      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 80,190,024      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 96,959,229      
Accumulated Depreciation (24,170,095)      
Investment in Real Estate Net 72,789,134      
Encumbrances $ 0      
Residences at Westgate I (fka Westage II) [Member]        
Real Estates 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 107,725,435      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 37,183      
Gross Amount Carried at close of period 12/31/2015, Land 17,859,785      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 107,762,618      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 125,622,403      
Accumulated Depreciation (6,461,296)      
Investment in Real Estate Net 119,161,107      
Encumbrances $ 0      
Residences at Westgate II (fka Westgage III) [Member]        
Real Estates 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 $ 12,118,061      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 39,965,098      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,415      
Gross Amount Carried at close of period 12/31/2015, Land 12,118,061      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 39,968,513      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 52,086,574      
Accumulated Depreciation (1,103,584)      
Investment in Real Estate Net 50,982,990      
Encumbrances $ 0      
Rianna I [Member]        
Real Estates 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 500,196      
Gross Amount Carried at close of period 12/31/2015, Land 2,268,160      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 15,364,678      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 17,632,838      
Accumulated Depreciation (4,413,092)      
Investment in Real Estate Net 13,219,746      
Encumbrances $ 0      
Ridgewood Village I&II [Member]        
Real Estates 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 5,222,765      
Gross Amount Carried at close of period 12/31/2015, Land 11,809,500      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 39,226,813      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 51,036,313      
Accumulated Depreciation (21,544,992)      
Investment in Real Estate Net 29,491,321      
Encumbrances $ 0      
Riva Terra I (fka Redwood Shores) [Member]        
Real Estates 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 1,065,313      
Gross Amount Carried at close of period 12/31/2015, Land 34,963,355      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 85,652,971      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 120,616,326      
Accumulated Depreciation (13,337,511)      
Investment in Real Estate Net 107,278,815      
Encumbrances $ 0      
Riva Terra II (fka Harborside) [Member]        
Real Estates 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 1,657,715      
Gross Amount Carried at close of period 12/31/2015, Land 17,136,645      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 42,194,246      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 59,330,891      
Accumulated Depreciation (6,014,126)      
Investment in Real Estate Net 53,316,765      
Encumbrances $ 0      
River Tower [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location New York, NY      
Real Estate And Accumulated Depreciation Units 323      
Initial Cost to Company, Land $ 118,669,441      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 98,880,559      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 6,922,776      
Gross Amount Carried at close of period 12/31/2015, Land 118,669,441      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 105,803,335      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 224,472,776      
Accumulated Depreciation (31,766,311)      
Investment in Real Estate Net 192,706,465      
Encumbrances $ 0      
Riverpark [Member]        
Real Estates 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 852,454      
Gross Amount Carried at close of period 12/31/2015, Land 14,355,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 81,746,503      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 96,101,503      
Accumulated Depreciation (15,145,119)      
Investment in Real Estate Net 80,956,384      
Encumbrances $ 0      
Rivers Bend (CT) [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Windsor, CT      
Real Estate And Accumulated Depreciation Units 373      
Initial Cost to Company, Land $ 3,325,517      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 22,573,826      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,383,538      
Gross Amount Carried at close of period 12/31/2015, Land 3,325,517      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 25,957,364      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 29,282,881      
Accumulated Depreciation (14,452,521)      
Investment in Real Estate Net 14,830,360      
Encumbrances $ 0      
Riverview Condominiums [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Norwalk, CT      
Real Estate And Accumulated Depreciation Units 92      
Initial Cost to Company, Land $ 2,300,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 7,406,730      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,560,055      
Gross Amount Carried at close of period 12/31/2015, Land 2,300,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 9,966,785      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 12,266,785      
Accumulated Depreciation (5,911,876)      
Investment in Real Estate Net 6,354,909      
Encumbrances $ 0      
Rolling Green (Milford) [Member]        
Real Estates 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 6,536,428      
Gross Amount Carried at close of period 12/31/2015, Land 2,012,350      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 19,988,578      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 22,000,928      
Accumulated Depreciation (11,602,104)      
Investment in Real Estate Net 10,398,824      
Encumbrances $ 0      
Rosecliff II [Member]        
Real Estates 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 668,021      
Gross Amount Carried at close of period 12/31/2015, Land 4,922,840      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 30,870,181      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 35,793,021      
Accumulated Depreciation (6,606,758)      
Investment in Real Estate Net 29,186,263      
Encumbrances $ 0      
Sakura Crossing [Member]        
Real Estates 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 516,747      
Gross Amount Carried at close of period 12/31/2015, Land 14,641,990      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 43,374,757      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 58,016,747      
Accumulated Depreciation (10,000,868)      
Investment in Real Estate Net 48,015,879      
Encumbrances $ 0      
Seventh & James [Member]        
Real Estates 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 3,738,122      
Gross Amount Carried at close of period 12/31/2015, Land 663,800      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 9,712,925      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 10,376,725      
Accumulated Depreciation (6,665,425)      
Investment in Real Estate Net 3,711,300      
Encumbrances $ 0      
Sheffield Court [Member]        
Real Estates 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 13,786,422      
Gross Amount Carried at close of period 12/31/2015, Land 3,342,381      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 45,123,754      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 48,466,135      
Accumulated Depreciation (31,901,556)      
Investment in Real Estate Net 16,564,579      
Encumbrances $ 0      
Skycrest [Member]        
Real Estates 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 2,534,401      
Gross Amount Carried at close of period 12/31/2015, Land 10,560,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 28,108,858      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 38,668,858      
Accumulated Depreciation (15,040,496)      
Investment in Real Estate Net 23,628,362      
Encumbrances $ 0      
Skylark [Member]        
Real Estates 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 3,437,547      
Gross Amount Carried at close of period 12/31/2015, Land 1,781,600      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 20,169,463      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 21,951,063      
Accumulated Depreciation (11,666,506)      
Investment in Real Estate Net 10,284,557      
Encumbrances $ 0      
Skyline Terrace [Member]        
Real Estates 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 4,411,395      
Gross Amount Carried at close of period 12/31/2015, Land 16,836,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 39,825,395      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 56,661,395      
Accumulated Depreciation (10,031,613)      
Investment in Real Estate Net 46,629,782      
Encumbrances $ 0      
Skyline Towers [Member]        
Real Estates 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 35,113,125      
Gross Amount Carried at close of period 12/31/2015, Land 78,278,200      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 126,598,716      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 204,876,916      
Accumulated Depreciation (60,654,648)      
Investment in Real Estate Net 144,222,268      
Encumbrances $ 0      
SoMa II [Member]        
Real Estates 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 $ 29,406,496      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 1,512,966      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2015, Land 29,406,496      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 1,512,966      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 30,919,462      
Accumulated Depreciation 0      
Investment in Real Estate Net 30,919,462      
Encumbrances $ 0      
Sonterra at Foothill Ranch [Member]        
Real Estates 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 4,091,719      
Gross Amount Carried at close of period 12/31/2015, Land 7,503,400      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 28,140,226      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 35,643,626      
Accumulated Depreciation (16,219,354)      
Investment in Real Estate Net 19,424,272      
Encumbrances $ 0      
South City Station (fka South San Francisco) [Member]        
Real Estates 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 2,029,236      
Gross Amount Carried at close of period 12/31/2015, Land 68,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 81,506,097      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 150,406,097      
Accumulated Depreciation (12,682,198)      
Investment in Real Estate Net 137,723,899      
Encumbrances $ 0      
South Winds [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Fall River, MA      
Real Estate And Accumulated Depreciation Units 404      
Initial Cost to Company, Land $ 2,481,821      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 16,780,359      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 5,786,341      
Gross Amount Carried at close of period 12/31/2015, Land 2,481,821      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 22,566,700      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 25,048,521      
Accumulated Depreciation (12,988,103)      
Investment in Real Estate Net 12,060,418      
Encumbrances $ 0      
Southwood [Member]        
Real Estates 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 3,133,285      
Gross Amount Carried at close of period 12/31/2015, Land 6,936,600      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 17,457,354      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 24,393,954      
Accumulated Depreciation (10,724,438)      
Investment in Real Estate Net 13,669,516      
Encumbrances $ 0      
Springbrook Estates [Member]        
Real Estates 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 12/31/2015, 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      
Encumbrances $ 0      
Square One [Member]        
Real Estates 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 11,820      
Gross Amount Carried at close of period 12/31/2015, Land 7,222,544      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 26,289,276      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 33,511,820      
Accumulated Depreciation (2,132,808)      
Investment in Real Estate Net 31,379,012      
Encumbrances $ 0      
Summerset Village II [Member]        
Real Estates 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 12/31/2015, 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      
Encumbrances $ 0      
Summit And Birch Hill [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Farmington, CT      
Real Estate And Accumulated Depreciation Units 186      
Initial Cost to Company, Land $ 1,757,438      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 11,748,112      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,699,790      
Gross Amount Carried at close of period 12/31/2015, Land 1,757,438      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 15,447,902      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 17,205,340      
Accumulated Depreciation (9,010,282)      
Investment in Real Estate Net 8,195,058      
Encumbrances $ 0      
Summit at Sausalito (fka Sausalito) [Member]        
Real Estates 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 3,038,378      
Gross Amount Carried at close of period 12/31/2015, Land 26,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 31,473,402      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 57,473,402      
Accumulated Depreciation (5,983,695)      
Investment in Real Estate Net 51,489,707      
Encumbrances $ 0      
Ten23 (fka 500 West 23rd Street) [Member]        
Real Estates 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 58,881,773      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 145,689      
Gross Amount Carried at close of period 12/31/2015, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 59,027,462      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 59,027,462      
Accumulated Depreciation (8,159,767)      
Investment in Real Estate Net 50,867,695      
Encumbrances $ 0      
Terraces, The [Member]        
Real Estates 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 792,092      
Gross Amount Carried at close of period 12/31/2015, Land 14,087,610      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 17,106,243      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 31,193,853      
Accumulated Depreciation (4,289,162)      
Investment in Real Estate Net 26,904,691      
Encumbrances $ 0      
Third Square [Member]        
Real Estates 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 3,752,897      
Gross Amount Carried at close of period 12/31/2015, Land 26,767,171      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 222,575,625      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 249,342,796      
Accumulated Depreciation (54,468,452)      
Investment in Real Estate Net 194,874,344      
Encumbrances $ 0      
Three20 [Member]        
Real Estates 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 620,352      
Gross Amount Carried at close of period 12/31/2015, Land 7,030,766      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 29,626,114      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 36,656,880      
Accumulated Depreciation (2,968,086)      
Investment in Real Estate Net 33,688,794      
Encumbrances $ 0      
Town Center South Commercial Tract [Member]        
Real Estates 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 12/31/2015, 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      
Encumbrances $ 0      
Town Square at Mark Center II [Member]        
Real Estates 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 891,715      
Gross Amount Carried at close of period 12/31/2015, Land 15,568,464      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 55,921,322      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 71,489,786      
Accumulated Depreciation (15,215,629)      
Investment in Real Estate Net 56,274,157      
Encumbrances $ 0      
Trump Place, 140 Riverside [Member]        
Real Estates 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 5,016,383      
Gross Amount Carried at close of period 12/31/2015, Land 103,539,100      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 99,099,108      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 202,638,208      
Accumulated Depreciation (37,252,860)      
Investment in Real Estate Net 165,385,348      
Encumbrances $ 0      
Trump Place, 160 Riverside [Member]        
Real Estates 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 11,256,618      
Gross Amount Carried at close of period 12/31/2015, Land 139,933,500      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 202,221,363      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 342,154,863      
Accumulated Depreciation (74,504,178)      
Investment in Real Estate Net 267,650,685      
Encumbrances $ 0      
Trump Place, 180 Riverside [Member]        
Real Estates 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 9,992,673      
Gross Amount Carried at close of period 12/31/2015, Land 144,968,250      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 148,339,354      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 293,307,604      
Accumulated Depreciation (56,241,522)      
Investment in Real Estate Net 237,066,082      
Encumbrances $ 0      
Urbana (fka Market Street Landing) [Member]        
Real Estates 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 74,480,619      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 269,601      
Gross Amount Carried at close of period 12/31/2015, Land 12,542,418      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 74,750,220      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 87,292,638      
Accumulated Depreciation (6,439,418)      
Investment in Real Estate Net 80,853,220      
Encumbrances $ 0      
Uwajimaya Village [Member]        
Real Estates 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 528,472      
Gross Amount Carried at close of period 12/31/2015, Land 8,800,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 22,716,760      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 31,516,760      
Accumulated Depreciation (9,395,695)      
Investment in Real Estate Net 22,121,065      
Encumbrances $ 0      
Vantage Pointe [Member]        
Real Estates 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 7,589,101      
Gross Amount Carried at close of period 12/31/2015, Land 9,403,960      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 198,185,141      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 207,589,101      
Accumulated Depreciation (45,420,591)      
Investment in Real Estate Net 162,168,510      
Encumbrances $ 0      
Veloce [Member]        
Real Estates 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 451,368      
Gross Amount Carried at close of period 12/31/2015, Land 15,322,724      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 76,627,962      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 91,950,686      
Accumulated Depreciation (11,158,120)      
Investment in Real Estate Net 80,792,566      
Encumbrances $ 0      
Verde Condominium Homes (fka Mission Verde, LLC) [Member]        
Real Estates 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 4,136,146      
Gross Amount Carried at close of period 12/31/2015, Land 5,190,700      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 13,815,255      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 19,005,955      
Accumulated Depreciation (8,802,858)      
Investment in Real Estate Net 10,203,097      
Encumbrances $ 0      
Veridian (fka Silver Spring) [Member]        
Real Estates 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 1,610,778      
Gross Amount Carried at close of period 12/31/2015, Land 18,539,817      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 132,018,143      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 150,557,960      
Accumulated Depreciation (29,933,549)      
Investment in Real Estate Net 120,624,411      
Encumbrances $ 0      
Villa Solana [Member]        
Real Estates 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 9,240,278      
Gross Amount Carried at close of period 12/31/2015, Land 1,665,100      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 24,225,956      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 25,891,056      
Accumulated Depreciation (17,544,510)      
Investment in Real Estate Net 8,346,546      
Encumbrances $ 0      
Village at Del Mar Heights, The (fka Del Mar Heights) [Member]        
Real Estates 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 452,196      
Gross Amount Carried at close of period 12/31/2015, Land 15,100,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 41,311,592      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 56,411,592      
Accumulated Depreciation (6,269,124)      
Investment in Real Estate Net 50,142,468      
Encumbrances $ 0      
Virginia Square [Member]        
Real Estates 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 2,314,664      
Gross Amount Carried at close of period 12/31/2015, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 88,254,667      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 88,254,667      
Accumulated Depreciation (12,224,720)      
Investment in Real Estate Net 76,029,947      
Encumbrances $ 0      
Vista 99 (fka Tasman) [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location San Jose, CA      
Real Estate And Accumulated Depreciation Units 0      
Initial Cost to Company, Land $ 27,709,329      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 163,443,672      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2015, Land 27,709,329      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 163,443,672      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 191,153,001      
Accumulated Depreciation 0      
Investment in Real Estate Net 191,153,001      
Encumbrances $ 0      
Vista Del Lago [Member]        
Real Estates 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 15,916,279      
Gross Amount Carried at close of period 12/31/2015, Land 4,525,800      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 56,652,572      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 61,178,372      
Accumulated Depreciation (41,596,423)      
Investment in Real Estate Net 19,581,949      
Encumbrances $ 0      
Vista on Courthouse [Member]        
Real Estates 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 1,252,472      
Gross Amount Carried at close of period 12/31/2015, Land 15,550,260      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 70,702,212      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 86,252,472      
Accumulated Depreciation (18,744,668)      
Investment in Real Estate Net 67,507,804      
Encumbrances $ 0      
Walden Park [Member]        
Real Estates 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 3,777,135      
Gross Amount Carried at close of period 12/31/2015, Land 12,448,888      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 55,821,583      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 68,270,471      
Accumulated Depreciation (12,955,477)      
Investment in Real Estate Net 55,314,994      
Encumbrances $ 0      
Watertown Square [Member]        
Real Estates 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 492,605      
Gross Amount Carried at close of period 12/31/2015, Land 16,800,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 34,566,661      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 51,366,661      
Accumulated Depreciation (5,057,515)      
Investment in Real Estate Net 46,309,146      
Encumbrances $ 0      
Webster Green [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Needham, MA      
Real Estate And Accumulated Depreciation Units 77      
Initial Cost to Company, Land $ 1,418,893      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 9,485,006      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,325,106      
Gross Amount Carried at close of period 12/31/2015, Land 1,418,893      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 10,810,112      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 12,229,005      
Accumulated Depreciation (5,911,293)      
Investment in Real Estate Net 6,317,712      
Encumbrances $ 0      
West 96th [Member]        
Real Estates 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 2,339,801      
Gross Amount Carried at close of period 12/31/2015, Land 84,800,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 69,395,303      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 154,195,303      
Accumulated Depreciation (12,819,335)      
Investment in Real Estate Net 141,375,968      
Encumbrances $ 0      
West End Apartments (fka Emerson Place/ CRP II) [Member]        
Real Estates 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 2,000,511      
Gross Amount Carried at close of period 12/31/2015, Land 469,546      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 165,123,533      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 165,593,079      
Accumulated Depreciation (44,450,837)      
Investment in Real Estate Net 121,142,242      
Encumbrances $ 0      
Westchester at Rockville [Member]        
Real Estates 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 361,408      
Gross Amount Carried at close of period 12/31/2015, Land 10,600,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 44,496,615      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 55,096,615      
Accumulated Depreciation (6,548,905)      
Investment in Real Estate Net 48,547,710      
Encumbrances $ 0      
Westmont [Member]        
Real Estates 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 1,305,267      
Gross Amount Carried at close of period 12/31/2015, Land 64,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 62,448,526      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 127,348,526      
Accumulated Depreciation (10,006,114)      
Investment in Real Estate Net 117,342,412      
Encumbrances $ 0      
Westside [Member]        
Real Estates 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 2,192,331      
Gross Amount Carried at close of period 12/31/2015, Land 34,200,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 59,154,961      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 93,354,961      
Accumulated Depreciation (8,309,849)      
Investment in Real Estate Net 85,045,112      
Encumbrances $ 0      
Westside Barrington (fka Westside Villas III) [Member]        
Real Estates 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 597,629      
Gross Amount Carried at close of period 12/31/2015, Land 3,060,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 6,136,500      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 9,196,500      
Accumulated Depreciation (3,105,675)      
Investment in Real Estate Net 6,090,825      
Encumbrances $ 0      
Westside Barry (fka Westside Villas VI) [Member]        
Real Estates 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 402,842      
Gross Amount Carried at close of period 12/31/2015, Land 1,530,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 3,426,365      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 4,956,365      
Accumulated Depreciation (1,787,554)      
Investment in Real Estate Net 3,168,811      
Encumbrances $ 0      
Westside Beloit (fka Westside Villas I) [Member]        
Real Estates 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 513,625      
Gross Amount Carried at close of period 12/31/2015, Land 1,785,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 3,746,879      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 5,531,879      
Accumulated Depreciation (1,945,537)      
Investment in Real Estate Net 3,586,342      
Encumbrances $ 0      
Westside Bundy (fka Westside Villas II) [Member]        
Real Estates 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 424,651      
Gross Amount Carried at close of period 12/31/2015, Land 1,955,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 3,966,086      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 5,921,086      
Accumulated Depreciation (1,996,405)      
Investment in Real Estate Net 3,924,681      
Encumbrances $ 0      
Westside Butler (fka Westside Villas IV) [Member]        
Real Estates 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 596,890      
Gross Amount Carried at close of period 12/31/2015, Land 3,060,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 6,136,280      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 9,196,280      
Accumulated Depreciation (3,111,743)      
Investment in Real Estate Net 6,084,537      
Encumbrances $ 0      
Westside Villas (fka Westside Villas V & VII) [Member]        
Real Estates 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 1,877,050      
Gross Amount Carried at close of period 12/31/2015, Land 9,605,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 21,860,435      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 31,465,435      
Accumulated Depreciation (10,577,308)      
Investment in Real Estate Net 20,888,127      
Encumbrances $ 0      
Westwood Glen [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Westwood, MA      
Real Estate And Accumulated Depreciation Units 156      
Initial Cost to Company, Land $ 1,616,505      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 10,806,004      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,400,201      
Gross Amount Carried at close of period 12/31/2015, Land 1,616,505      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 13,206,205      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 14,822,710      
Accumulated Depreciation (7,265,245)      
Investment in Real Estate Net 7,557,465      
Encumbrances $ 0      
Windridge (CA) [Member]        
Real Estates 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 9,301,611      
Gross Amount Carried at close of period 12/31/2015, Land 2,662,900      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 33,287,108      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 35,950,008      
Accumulated Depreciation (23,042,811)      
Investment in Real Estate Net 12,907,197      
Encumbrances $ 0      
Wood Creek I [Member]        
Real Estates 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 6,723,042      
Gross Amount Carried at close of period 12/31/2015, Land 9,729,900      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 29,732,810      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 39,462,710      
Accumulated Depreciation (19,191,248)      
Investment in Real Estate Net 20,271,462      
Encumbrances $ 0      
Woodbridge (CT) [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Newington, CT      
Real Estate And Accumulated Depreciation Units 73      
Initial Cost to Company, Land $ 498,377      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 3,331,548      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,316,602      
Gross Amount Carried at close of period 12/31/2015, Land 498,377      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 4,648,150      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 5,146,527      
Accumulated Depreciation (2,687,633)      
Investment in Real Estate Net 2,458,894      
Encumbrances $ 0      
Woodland Park [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location East Palo Alto, CA      
Real Estate And Accumulated Depreciation Units 1,811      
Initial Cost to Company, Land $ 74,900,178      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 61,407,965      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 10,172,148      
Gross Amount Carried at close of period 12/31/2015, Land 74,900,178      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 71,580,113      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 146,480,291      
Accumulated Depreciation (29,503,957)      
Investment in Real Estate Net 116,976,334      
Encumbrances $ 0      
Management Business [Member]        
Real Estates 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 107,367,022      
Gross Amount Carried at close of period 12/31/2015, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 107,367,022      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 107,367,022      
Accumulated Depreciation (84,488,405)      
Investment in Real Estate Net 22,878,617      
Encumbrances $ 0      
Operating Partnership [Member]        
Real Estates 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 10,060,473      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2015, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 10,060,473      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 10,060,473      
Accumulated Depreciation 0      
Investment in Real Estate Net 10,060,473      
Encumbrances $ 0      
Investment in Real Estate - Wholly Owned Unencumbered [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Units 52,513      
Initial Cost to Company, Land $ 4,495,508,075      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 12,087,293,175      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 855,011,332      
Gross Amount Carried at close of period 12/31/2015, Land 4,495,508,075      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 12,942,304,507      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 17,437,812,582      
Accumulated Depreciation (3,224,397,212)      
Investment in Real Estate Net 14,213,415,370      
Encumbrances $ 0      
101 West End [Member]        
Real Estates 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 2,576,456      
Gross Amount Carried at close of period 12/31/2015, Land 190,600,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 133,951,164      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 324,551,164      
Accumulated Depreciation (24,450,561)      
Investment in Real Estate Net 300,100,603      
Encumbrances $ 106,080,734      
1401 Joyce On Pentagon Row [Member]        
Real Estates 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 2,229,551      
Gross Amount Carried at close of period 12/31/2015, Land 9,780,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 91,897,716      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 101,677,716      
Accumulated Depreciation (25,254,785)      
Investment in Real Estate Net 76,422,931      
Encumbrances $ 57,428,472      
2501 Porter [Member]        
Real Estates 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 2,533,202      
Gross Amount Carried at close of period 12/31/2015, Land 13,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 77,804,381      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 90,804,381      
Accumulated Depreciation (10,706,382)      
Investment in Real Estate Net $ 80,097,999      
Real Estate And Accumulated Depreciation, Encumbrances Reference [1] (L)      
300 East 39th (fka East 39th) [Member]        
Real Estates 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 1,477,085      
Gross Amount Carried at close of period 12/31/2015, Land 48,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 97,651,724      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 146,551,724      
Accumulated Depreciation (14,652,321)      
Investment in Real Estate Net 131,899,403      
Encumbrances $ 60,075,893      
303 East 83rd (fka Camargue) [Member]        
Real Estates 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 1,412,483      
Gross Amount Carried at close of period 12/31/2015, Land 79,400,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 80,535,107      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 159,935,107      
Accumulated Depreciation (13,348,028)      
Investment in Real Estate Net $ 146,587,079      
Real Estate And Accumulated Depreciation, Encumbrances Reference [1] (L)      
3003 Van Ness (fka Van Ness) [Member]        
Real Estates 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 2,859,298      
Gross Amount Carried at close of period 12/31/2015, Land 56,300,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 144,050,878      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 200,350,878      
Accumulated Depreciation (22,215,124)      
Investment in Real Estate Net $ 178,135,754      
Real Estate And Accumulated Depreciation, Encumbrances Reference [1] (K)      
425 Broadway [Member]        
Real Estates 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 1,594,856      
Gross Amount Carried at close of period 12/31/2015, Land 12,600,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 35,989,628      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 48,589,628      
Accumulated Depreciation (4,950,823)      
Investment in Real Estate Net $ 43,638,805      
Real Estate And Accumulated Depreciation, Encumbrances Reference [1] (L)      
4701 Willard [Member]        
Real Estates 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 27,665,480      
Gross Amount Carried at close of period 12/31/2015, Land 76,921,130      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 181,613,162      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 258,534,292      
Accumulated Depreciation (32,880,043)      
Investment in Real Estate Net 225,654,249      
Encumbrances $ 95,363,077      
55 West Fifth I & II (fka Townhouse Plaza and Gardens) [Member]        
Real Estates 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 10,143,724      
Gross Amount Carried at close of period 12/31/2015, Land 21,041,710      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 82,075,047      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 103,116,757      
Accumulated Depreciation (13,529,391)      
Investment in Real Estate Net 89,587,366      
Encumbrances $ 28,269,109      
77 Park Avenue (fka Hoboken) [Member]        
Real Estates 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 3,529,188      
Gross Amount Carried at close of period 12/31/2015, Land 27,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 172,521,628      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 200,421,628      
Accumulated Depreciation (22,319,468)      
Investment in Real Estate Net $ 178,102,160      
Real Estate And Accumulated Depreciation, Encumbrances Reference [1] (K)      
800 Sixth Ave (fka Chelsea) [Member]        
Real Estates 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 503,998      
Gross Amount Carried at close of period 12/31/2015, Land 59,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 156,365,603      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 216,265,603      
Accumulated Depreciation (21,941,504)      
Investment in Real Estate Net 194,324,099      
Encumbrances $ 77,542,253      
929 Mass (fka 929 House) [Member]        
Real Estates 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 6,057,741      
Gross Amount Carried at close of period 12/31/2015, Land 3,252,993      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 27,803,336      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 31,056,329      
Accumulated Depreciation (14,907,606)      
Investment in Real Estate Net 16,148,723      
Encumbrances $ 1,408,857      
Academy Village [Member]        
Real Estates 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 7,547,018      
Gross Amount Carried at close of period 12/31/2015, Land 25,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 31,140,212      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 56,140,212      
Accumulated Depreciation (15,489,771)      
Investment in Real Estate Net 40,650,441      
Encumbrances $ 20,000,000      
Acappella [Member]        
Real Estates 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 1,386,963      
Gross Amount Carried at close of period 12/31/2015, Land 5,839,548      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 30,747,415      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 36,586,963      
Accumulated Depreciation (7,867,305)      
Investment in Real Estate Net 28,719,658      
Encumbrances $ 19,548,601      
Acton Courtyard [Member]        
Real Estates 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 179,627      
Gross Amount Carried at close of period 12/31/2015, Land 5,550,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 15,965,136      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 21,515,136      
Accumulated Depreciation (5,574,135)      
Investment in Real Estate Net 15,941,001      
Encumbrances $ 9,920,000      
Alborada [Member]        
Real Estates 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 4,613,227      
Gross Amount Carried at close of period 12/31/2015, Land 24,310,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 63,827,356      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 88,137,356      
Accumulated Depreciation (34,004,610)      
Investment in Real Estate Net $ 54,132,746      
Real Estate And Accumulated Depreciation, Encumbrances Reference [1] (I)      
Alcyone [Member]        
Real Estates 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 312,223      
Gross Amount Carried at close of period 12/31/2015, Land 11,379,497      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 49,672,726      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 61,052,223      
Accumulated Depreciation (3,589,789)      
Investment in Real Estate Net 57,462,434      
Encumbrances $ 28,936,250      
Arches, The [Member]        
Real Estates 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 1,070,248      
Gross Amount Carried at close of period 12/31/2015, Land 26,650,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 63,920,248      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 90,570,248      
Accumulated Depreciation (15,872,496)      
Investment in Real Estate Net $ 74,697,752      
Real Estate And Accumulated Depreciation, Encumbrances Reference [1] (J)      
Artech Building [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Berkeley, CA      
Real Estate And Accumulated Depreciation Units 21      
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 307,744      
Gross Amount Carried at close of period 12/31/2015, Land 1,642,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 9,460,262      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 11,102,262      
Accumulated Depreciation (3,049,419)      
Investment in Real Estate Net 8,052,843      
Encumbrances $ 3,200,000      
Artisan Square [Member]        
Real Estates 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 1,156,962      
Gross Amount Carried at close of period 12/31/2015, Land 7,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 21,694,321      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 28,694,321      
Accumulated Depreciation (9,975,656)      
Investment in Real Estate Net 18,718,665      
Encumbrances $ 22,779,715      
Avanti [Member]        
Real Estates 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 1,948,417      
Gross Amount Carried at close of period 12/31/2015, Land 12,960,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 20,446,099      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 33,406,099      
Accumulated Depreciation (7,861,843)      
Investment in Real Estate Net 25,544,256      
Encumbrances $ 18,169,458      
Avenir [Member]        
Real Estates 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 114,321,619      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 853,000      
Gross Amount Carried at close of period 12/31/2015, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 115,174,619      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 115,174,619      
Accumulated Depreciation (16,129,562)      
Investment in Real Estate Net 99,045,057      
Encumbrances $ 92,869,154      
Bachenheimer Building [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Berkeley, CA      
Real Estate And Accumulated Depreciation Units 44      
Initial Cost to Company, Land $ 3,439,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 13,866,379      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 136,057      
Gross Amount Carried at close of period 12/31/2015, Land 3,439,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 14,002,436      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 17,441,436      
Accumulated Depreciation (4,681,558)      
Investment in Real Estate Net 12,759,878      
Encumbrances $ 8,585,000      
Bella Vista I, II, III Combined [Member]        
Real Estates 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 3,202,259      
Gross Amount Carried at close of period 12/31/2015, Land 31,682,754      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 124,298,045      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 155,980,799      
Accumulated Depreciation (45,159,303)      
Investment in Real Estate Net 110,821,496      
Encumbrances $ 58,055,099      
Berkeleyan [Member]        
Real Estates 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 351,018      
Gross Amount Carried at close of period 12/31/2015, Land 4,377,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 16,373,128      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 20,750,128      
Accumulated Depreciation (5,615,136)      
Investment in Real Estate Net 15,134,992      
Encumbrances $ 8,290,000      
Calvert Woodley [Member]        
Real Estates 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 1,351,455      
Gross Amount Carried at close of period 12/31/2015, Land 12,600,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 44,878,834      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 57,478,834      
Accumulated Depreciation (6,634,781)      
Investment in Real Estate Net $ 50,844,053      
Real Estate And Accumulated Depreciation, Encumbrances Reference [1] (L)      
Carmel Terrace [Member]        
Real Estates 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 10,947,605      
Gross Amount Carried at close of period 12/31/2015, Land 2,288,300      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 31,543,886      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 33,832,186      
Accumulated Depreciation (24,139,928)      
Investment in Real Estate Net $ 9,692,258      
Real Estate And Accumulated Depreciation, Encumbrances Reference [1] (J)      
Chelsea Square [Member]        
Real Estates 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 1,938,442      
Gross Amount Carried at close of period 12/31/2015, Land 3,397,100      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 11,227,516      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 14,624,616      
Accumulated Depreciation (6,785,484)      
Investment in Real Estate Net 7,839,132      
Encumbrances $ 9,270,000      
Citrus Suites [Member]        
Real Estates 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 498,789      
Gross Amount Carried at close of period 12/31/2015, Land 9,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 17,449,115      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 26,449,115      
Accumulated Depreciation (2,511,650)      
Investment in Real Estate Net $ 23,937,465      
Real Estate And Accumulated Depreciation, Encumbrances Reference [1] (L)      
CityView at Longwood [Member]        
Real Estates 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 9,909,279      
Gross Amount Carried at close of period 12/31/2015, Land 14,704,898      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 89,104,381      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 103,809,279      
Accumulated Depreciation (22,102,861)      
Investment in Real Estate Net 81,706,418      
Encumbrances $ 22,813,347      
Cleveland House [Member]        
Real Estates 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 2,268,181      
Gross Amount Carried at close of period 12/31/2015, Land 18,300,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 68,660,595      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 86,960,595      
Accumulated Depreciation (9,841,260)      
Investment in Real Estate Net $ 77,119,335      
Real Estate And Accumulated Depreciation, Encumbrances Reference [1] (L)      
Columbia Crossing [Member]        
Real Estates 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 2,133,914      
Gross Amount Carried at close of period 12/31/2015, Land 23,500,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 55,178,987      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 78,678,987      
Accumulated Depreciation (8,468,042)      
Investment in Real Estate Net $ 70,210,945      
Real Estate And Accumulated Depreciation, Encumbrances Reference [1] (L)      
Connecticut Heights [Member]        
Real Estates 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 2,233,880      
Gross Amount Carried at close of period 12/31/2015, Land 27,600,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 116,236,175      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 143,836,175      
Accumulated Depreciation (15,994,030)      
Investment in Real Estate Net $ 127,842,145      
Real Estate And Accumulated Depreciation, Encumbrances Reference [1] (K)      
Deerwood (SD) [Member]        
Real Estates 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 14,281,345      
Gross Amount Carried at close of period 12/31/2015, Land 2,082,095      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 33,021,160      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 35,103,255      
Accumulated Depreciation (25,264,071)      
Investment in Real Estate Net $ 9,839,184      
Real Estate And Accumulated Depreciation, Encumbrances Reference [1] (J)      
Del Mar Ridge [Member]        
Real Estates 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 3,200,550      
Gross Amount Carried at close of period 12/31/2015, Land 7,801,824      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 40,148,726      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 47,950,550      
Accumulated Depreciation (11,807,817)      
Investment in Real Estate Net 36,142,733      
Encumbrances $ 23,789,381      
Estancia at Santa Clara (fka Santa Clara) [Member]        
Real Estates 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 712,699      
Gross Amount Carried at close of period 12/31/2015, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 124,472,503      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 124,472,503      
Accumulated Depreciation (18,177,935)      
Investment in Real Estate Net $ 106,294,568      
Real Estate And Accumulated Depreciation, Encumbrances Reference [1] (L)      
Fairchase [Member]        
Real Estates 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 486,155      
Gross Amount Carried at close of period 12/31/2015, Land 23,500,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 88,208,476      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 111,708,476      
Accumulated Depreciation (12,420,764)      
Investment in Real Estate Net $ 99,287,712      
Real Estate And Accumulated Depreciation, Encumbrances Reference [1] (L)      
Fairfield [Member]        
Real Estates 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 6,807,773      
Gross Amount Carried at close of period 12/31/2015, Land 6,510,200      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 46,497,893      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 53,008,093      
Accumulated Depreciation (29,297,448)      
Investment in Real Estate Net 23,710,645      
Encumbrances $ 34,595,000      
Fine Arts Building [Member]        
Real Estates 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 322,852      
Gross Amount Carried at close of period 12/31/2015, Land 7,817,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 26,785,624      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 34,602,624      
Accumulated Depreciation (9,099,586)      
Investment in Real Estate Net 25,503,038      
Encumbrances $ 16,215,000      
Flats at DuPont Circle [Member]        
Real Estates 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 604,622      
Gross Amount Carried at close of period 12/31/2015, Land 35,200,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 109,372,820      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 144,572,820      
Accumulated Depreciation (14,855,770)      
Investment in Real Estate Net $ 129,717,050      
Real Estate And Accumulated Depreciation, Encumbrances Reference [1] (L)      
Gaia Building [Member]        
Real Estates 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 234,336      
Gross Amount Carried at close of period 12/31/2015, Land 7,113,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 25,858,162      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 32,971,162      
Accumulated Depreciation (8,785,368)      
Investment in Real Estate Net 24,185,794      
Encumbrances $ 14,630,000      
Gaithersburg Station [Member]        
Real Estates 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 395,060      
Gross Amount Carried at close of period 12/31/2015, Land 17,500,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 75,073,977      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 92,573,977      
Accumulated Depreciation (9,661,514)      
Investment in Real Estate Net 82,912,463      
Encumbrances $ 97,790,236      
Glo [Member]        
Real Estates 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 $ 16,047,023      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 48,650,963      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 808,007      
Gross Amount Carried at close of period 12/31/2015, Land 16,047,023      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 49,458,970      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 65,505,993      
Accumulated Depreciation (10,096,648)      
Investment in Real Estate Net 55,409,345      
Encumbrances $ 32,088,033      
Hathaway [Member]        
Real Estates 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 8,120,060      
Gross Amount Carried at close of period 12/31/2015, Land 2,512,500      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 30,731,972      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 33,244,472      
Accumulated Depreciation (21,884,752)      
Investment in Real Estate Net 11,359,720      
Encumbrances $ 46,517,800      
Heights on Capitol Hill [Member]        
Real Estates 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 295,592      
Gross Amount Carried at close of period 12/31/2015, Land 5,425,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 21,433,620      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 26,858,620      
Accumulated Depreciation (7,621,120)      
Investment in Real Estate Net 19,237,500      
Encumbrances $ 28,180,585      
Kelvin Court (fka Alta Pacific) [Member]        
Real Estates 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 387,734      
Gross Amount Carried at close of period 12/31/2015, Land 10,752,145      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 35,015,849      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 45,767,994      
Accumulated Depreciation (9,542,049)      
Investment in Real Estate Net 36,225,945      
Encumbrances $ 26,495,000      
Kenwood Mews [Member]        
Real Estates 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 3,351,321      
Gross Amount Carried at close of period 12/31/2015, Land 14,100,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 28,014,204      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 42,114,204      
Accumulated Depreciation (10,515,075)      
Investment in Real Estate Net $ 31,599,129      
Real Estate And Accumulated Depreciation, Encumbrances Reference [1] (J)      
La Terrazza at Colma Station [Member]        
Real Estates 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 701,808      
Gross Amount Carried at close of period 12/31/2015, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 41,952,852      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 41,952,852      
Accumulated Depreciation (14,153,248)      
Investment in Real Estate Net 27,799,604      
Encumbrances $ 25,175,000      
Laguna Clara [Member]        
Real Estates 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 4,533,141      
Gross Amount Carried at close of period 12/31/2015, Land 13,642,420      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 34,240,616      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 47,883,036      
Accumulated Depreciation (15,885,790)      
Investment in Real Estate Net $ 31,997,246      
Real Estate And Accumulated Depreciation, Encumbrances Reference [1] (J)      
Liberty Park [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Brain Tree, 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 5,245,483      
Gross Amount Carried at close of period 12/31/2015, Land 5,977,504      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 31,994,594      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 37,972,098      
Accumulated Depreciation (14,287,477)      
Investment in Real Estate Net 23,684,621      
Encumbrances $ 24,980,280      
Liberty Tower [Member]        
Real Estates 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 1,351,073      
Gross Amount Carried at close of period 12/31/2015, Land 16,382,822      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 85,168,151      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 101,550,973      
Accumulated Depreciation (20,623,905)      
Investment in Real Estate Net 80,927,068      
Encumbrances $ 45,909,078      
Longview Place [Member]        
Real Estates 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 3,935,492      
Gross Amount Carried at close of period 12/31/2015, Land 20,880,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 94,191,001      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 115,071,001      
Accumulated Depreciation (35,006,528)      
Investment in Real Estate Net 80,064,473      
Encumbrances $ 60,073,423      
Market Street Village [Member]        
Real Estates 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 1,855,488      
Gross Amount Carried at close of period 12/31/2015, Land 13,740,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 42,612,789      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 56,352,789      
Accumulated Depreciation (15,053,939)      
Investment in Real Estate Net $ 41,298,850      
Real Estate And Accumulated Depreciation, Encumbrances Reference [1] (J)      
Metro on First [Member]        
Real Estates 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 764,124      
Gross Amount Carried at close of period 12/31/2015, Land 8,540,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 12,974,105      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 21,514,105      
Accumulated Depreciation (4,929,664)      
Investment in Real Estate Net 16,584,441      
Encumbrances $ 22,843,410      
Mill Creek [Member]        
Real Estates 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 7,621,842      
Gross Amount Carried at close of period 12/31/2015, Land 12,858,693      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 64,790,345      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 77,649,038      
Accumulated Depreciation (28,371,508)      
Investment in Real Estate Net 49,277,530      
Encumbrances $ 69,312,259      
Moda [Member]        
Real Estates 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 801,043      
Gross Amount Carried at close of period 12/31/2015, Land 12,649,228      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 37,643,055      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 50,292,283      
Accumulated Depreciation (9,806,747)      
Investment in Real Estate Net $ 40,485,536      
Real Estate And Accumulated Depreciation, Encumbrances Reference [1] (M)      
Montierra (CA) [Member]        
Real Estates 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 7,505,606      
Gross Amount Carried at close of period 12/31/2015, Land 8,160,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 36,866,544      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 45,026,544      
Accumulated Depreciation (21,688,065)      
Investment in Real Estate Net $ 23,338,479      
Real Estate And Accumulated Depreciation, Encumbrances Reference [1] (J)      
Mosaic at Metro [Member]        
Real Estates 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 587,443      
Gross Amount Carried at close of period 12/31/2015, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 60,168,341      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 60,168,341      
Accumulated Depreciation (15,416,225)      
Investment in Real Estate Net 44,752,116      
Encumbrances $ 42,865,814      
North Pier at Harborside [Member]        
Real Estates 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 2,769,431      
Gross Amount Carried at close of period 12/31/2015, Land 4,000,159      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 97,060,021      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 101,060,180      
Accumulated Depreciation (39,300,172)      
Investment in Real Estate Net $ 61,760,008      
Real Estate And Accumulated Depreciation, Encumbrances Reference [1] (I)      
Oaks [Member]        
Real Estates 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 4,561,180      
Gross Amount Carried at close of period 12/31/2015, Land 23,400,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 65,581,618      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 88,981,618      
Accumulated Depreciation (29,469,941)      
Investment in Real Estate Net 59,511,677      
Encumbrances $ 35,967,006      
Olympus Towers [Member]        
Real Estates 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 7,047,844      
Gross Amount Carried at close of period 12/31/2015, Land 14,752,034      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 80,383,269      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 95,135,303      
Accumulated Depreciation (33,557,234)      
Investment in Real Estate Net 61,578,069      
Encumbrances $ 49,875,780      
Park Place at San Mateo (fka San Mateo) [Member]        
Real Estates 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 6,896,968      
Gross Amount Carried at close of period 12/31/2015, Land 71,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 218,804,109      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 290,704,109      
Accumulated Depreciation (30,601,516)      
Investment in Real Estate Net $ 260,102,593      
Real Estate And Accumulated Depreciation, Encumbrances Reference [1] (L)      
Providence [Member]        
Real Estates 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 1,082,155      
Gross Amount Carried at close of period 12/31/2015, Land 3,573,621      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 20,137,660      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 23,711,281      
Accumulated Depreciation (8,760,511)      
Investment in Real Estate Net $ 14,950,770      
Real Estate And Accumulated Depreciation, Encumbrances Reference [1] (I)      
Reserve at Clarendon Centre, The [Member]        
Real Estates 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 4,001,480      
Gross Amount Carried at close of period 12/31/2015, Land 10,500,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 56,814,415      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 67,314,415      
Accumulated Depreciation (24,499,908)      
Investment in Real Estate Net $ 42,814,507      
Real Estate And Accumulated Depreciation, Encumbrances Reference [1] (J)      
Reserve at Eisenhower, The [Member]        
Real Estates 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 1,518,215      
Gross Amount Carried at close of period 12/31/2015, Land 6,500,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 36,103,275      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 42,603,275      
Accumulated Depreciation (16,514,637)      
Investment in Real Estate Net $ 26,088,638      
Real Estate And Accumulated Depreciation, Encumbrances Reference [1] (J)      
Reserve at Empire Lakes [Member]        
Real Estates 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 2,428,206      
Gross Amount Carried at close of period 12/31/2015, Land 16,345,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 75,508,876      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 91,853,876      
Accumulated Depreciation (28,451,308)      
Investment in Real Estate Net $ 63,402,568      
Real Estate And Accumulated Depreciation, Encumbrances Reference [1] (I)      
Reserve at Fairfax Corners [Member]        
Real Estates 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 63,129,050      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 9,196,688      
Gross Amount Carried at close of period 12/31/2015, Land 15,804,057      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 72,325,738      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 88,129,795      
Accumulated Depreciation (32,718,387)      
Investment in Real Estate Net 55,411,408      
Encumbrances $ 84,778,876      
Rianna II [Member]        
Real Estates 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 317,548      
Gross Amount Carried at close of period 12/31/2015, Land 2,161,840      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 14,751,162      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 16,913,002      
Accumulated Depreciation (4,197,329)      
Investment in Real Estate Net 12,715,673      
Encumbrances $ 9,428,447      
Rockingham Glen [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location West Roxbury, MA      
Real Estate And Accumulated Depreciation Units 143      
Initial Cost to Company, Land $ 1,124,217      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 7,515,160      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,290,553      
Gross Amount Carried at close of period 12/31/2015, Land 1,124,217      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 9,805,713      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 10,929,930      
Accumulated Depreciation (5,551,551)      
Investment in Real Estate Net 5,378,379      
Encumbrances $ 523,346      
Siena Terrace [Member]        
Real Estates 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 6,763,521      
Gross Amount Carried at close of period 12/31/2015, Land 8,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 30,846,545      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 39,746,545      
Accumulated Depreciation (17,527,179)      
Investment in Real Estate Net 22,219,366      
Encumbrances $ 38,440,808      
Skyview [Member]        
Real Estates 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 4,360,171      
Gross Amount Carried at close of period 12/31/2015, Land 3,380,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 26,313,034      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 29,693,034      
Accumulated Depreciation (14,316,970)      
Investment in Real Estate Net 15,376,064      
Encumbrances $ 30,889,928      
SoMa Square Apartments (fka South Market) [Member]        
Real Estates 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 4,252,808      
Gross Amount Carried at close of period 12/31/2015, Land 79,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 181,569,785      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 261,469,785      
Accumulated Depreciation (25,190,244)      
Investment in Real Estate Net $ 236,279,541      
Real Estate And Accumulated Depreciation, Encumbrances Reference [1] (L)      
Summerset Village [Member]        
Real Estates 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 7,129,137      
Gross Amount Carried at close of period 12/31/2015, Land 2,629,804      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 30,800,026      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 33,429,830      
Accumulated Depreciation (19,917,548)      
Investment in Real Estate Net 13,512,282      
Encumbrances $ 38,039,912      
Talleyrand [Member]        
Real Estates 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 4,916,190      
Gross Amount Carried at close of period 12/31/2015, Land 12,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 54,754,350      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 66,754,350      
Accumulated Depreciation (27,823,399)      
Investment in Real Estate Net 38,930,951      
Encumbrances $ 35,000,000      
Teresina [Member]        
Real Estates 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 2,749,599      
Gross Amount Carried at close of period 12/31/2015, Land 28,600,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 64,666,269      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 93,266,269      
Accumulated Depreciation (25,093,215)      
Investment in Real Estate Net 68,173,054      
Encumbrances $ 40,302,570      
Toscana [Member]        
Real Estates 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 9,924,622      
Gross Amount Carried at close of period 12/31/2015, Land 39,410,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 60,730,694      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 100,140,694      
Accumulated Depreciation (32,579,537)      
Investment in Real Estate Net 67,561,157      
Encumbrances $ 71,243,194      
Touriel Building [Member]        
Real Estates 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 175,855      
Gross Amount Carried at close of period 12/31/2015, Land 2,736,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 7,985,882      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 10,721,882      
Accumulated Depreciation (2,797,420)      
Investment in Real Estate Net 7,924,462      
Encumbrances $ 5,050,000      
Town Square at Mark Center I (fka Millbrook I) [Member]        
Real Estates 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 3,521,624      
Gross Amount Carried at close of period 12/31/2015, Land 24,360,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 89,700,338      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 114,060,338      
Accumulated Depreciation (34,753,726)      
Investment in Real Estate Net 79,306,612      
Encumbrances $ 77,353,222      
Versailles [Member]        
Real Estates 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 5,804,577      
Gross Amount Carried at close of period 12/31/2015, Land 12,650,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 39,460,869      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 52,110,869      
Accumulated Depreciation (18,318,859)      
Investment in Real Estate Net 33,792,010      
Encumbrances $ 30,372,953      
Versailles (K-Town) [Member]        
Real Estates 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 1,300,111      
Gross Amount Carried at close of period 12/31/2015, Land 10,590,975      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 45,709,136      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 56,300,111      
Accumulated Depreciation (12,641,215)      
Investment in Real Estate Net 43,658,896      
Encumbrances $ 29,826,475      
Victor on Venice [Member]        
Real Estates 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 535,196      
Gross Amount Carried at close of period 12/31/2015, Land 10,350,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 35,968,633      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 46,318,633      
Accumulated Depreciation (12,337,193)      
Investment in Real Estate Net $ 33,981,440      
Real Estate And Accumulated Depreciation, Encumbrances Reference [1] (J)      
Vintage [Member]        
Real Estates 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 808,672      
Gross Amount Carried at close of period 12/31/2015, Land 7,059,230      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 48,486,434      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 55,545,664      
Accumulated Depreciation (17,191,840)      
Investment in Real Estate Net 38,353,824      
Encumbrances $ 33,000,000      
Vintage at 425 Broadway (fka Promenade) [Member]        
Real Estates 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 539,897      
Gross Amount Carried at close of period 12/31/2015, Land 9,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 14,501,420      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 23,501,420      
Accumulated Depreciation (2,424,132)      
Investment in Real Estate Net $ 21,077,288      
Real Estate And Accumulated Depreciation, Encumbrances Reference [1] (L)      
Water Park Towers [Member]        
Real Estates 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 4,832,524      
Gross Amount Carried at close of period 12/31/2015, Land 34,400,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 113,318,383      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 147,718,383      
Accumulated Depreciation (16,327,687)      
Investment in Real Estate Net $ 131,390,696      
Real Estate And Accumulated Depreciation, Encumbrances Reference [1] (K)      
West 54th [Member]        
Real Estates 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 605,010      
Gross Amount Carried at close of period 12/31/2015, Land 60,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 48,798,847      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 109,698,847      
Accumulated Depreciation (9,079,353)      
Investment in Real Estate Net 100,619,494      
Encumbrances $ 47,327,897      
Westgate (fka Westgate I) [Member]        
Real Estates 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 808,874      
Gross Amount Carried at close of period 12/31/2015, Land 22,898,848      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 134,368,447      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 157,267,295      
Accumulated Depreciation (23,243,923)      
Investment in Real Estate Net 134,023,372      
Encumbrances $ 96,935,000      
Woodleaf [Member]        
Real Estates 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 4,380,543      
Gross Amount Carried at close of period 12/31/2015, Land 8,550,600      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 21,368,726      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 29,919,326      
Accumulated Depreciation (12,368,124)      
Investment in Real Estate Net 17,551,202      
Encumbrances $ 17,858,854      
Investment in Real Estate - Wholly Owned Encumbered [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Units 23,686      
Initial Cost to Company, Land $ 1,688,383,769      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 5,069,221,671      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 297,359,218      
Gross Amount Carried at close of period 12/31/2015, Land 1,688,383,769      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 5,366,580,889      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 7,054,964,658      
Accumulated Depreciation (1,464,311,726)      
Investment in Real Estate Net 5,590,652,932      
Encumbrances $ 4,220,456,586      
2300 Elliott [Member]        
Real Estates 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 6,320,524      
Gross Amount Carried at close of period 12/31/2015, Land 796,800      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 13,494,249      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 14,291,049      
Accumulated Depreciation (10,068,231)      
Investment in Real Estate Net 4,222,818      
Encumbrances $ 0      
Canyon Ridge [Member]        
Real Estates 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 3,497,193      
Gross Amount Carried at close of period 12/31/2015, Land 4,869,448      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 15,452,257      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 20,321,705      
Accumulated Depreciation (9,266,022)      
Investment in Real Estate Net 11,055,683      
Encumbrances $ 0      
Country Oaks [Member]        
Real Estates 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 5,290,585      
Gross Amount Carried at close of period 12/31/2015, Land 6,105,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 34,852,450      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 40,957,450      
Accumulated Depreciation (16,944,551)      
Investment in Real Estate Net 24,012,899      
Encumbrances $ 0      
Fox Ridge [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Englewood, CO      
Real Estate And Accumulated Depreciation Units 300      
Initial Cost to Company, Land $ 2,490,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 17,522,114      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,823,697      
Gross Amount Carried at close of period 12/31/2015, Land 2,490,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 22,345,811      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 24,835,811      
Accumulated Depreciation (12,642,142)      
Investment in Real Estate Net 12,193,669      
Encumbrances $ 0      
Monterra in Mill Creek [Member]        
Real Estates 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 787,359      
Gross Amount Carried at close of period 12/31/2015, Land 2,800,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 14,042,482      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 16,842,482      
Accumulated Depreciation (5,598,815)      
Investment in Real Estate Net 11,243,667      
Encumbrances $ 0      
Rosecliff [Member]        
Real Estates 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 2,934,091      
Gross Amount Carried at close of period 12/31/2015, Land 5,460,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 18,655,661      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 24,115,661      
Accumulated Depreciation (10,612,838)      
Investment in Real Estate Net 13,502,823      
Encumbrances $ 0      
Strayhorse at Arrowhead Ranch [Member]        
Real Estates 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 627,934      
Gross Amount Carried at close of period 12/31/2015, Land 4,400,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 13,595,936      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 17,995,936      
Accumulated Depreciation (5,287,150)      
Investment in Real Estate Net 12,708,786      
Encumbrances $ 0      
Via Ventura (CA) (fka Ventura) [Member]        
Real Estates 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 542,226      
Gross Amount Carried at close of period 12/31/2015, Land 8,600,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 44,850,428      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 53,450,428      
Accumulated Depreciation (7,114,728)      
Investment in Real Estate Net 46,335,700      
Encumbrances $ 0      
Wood Creek II (fka Willow Brook (CA))        
Real Estates 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 5,892,178      
Gross Amount Carried at close of period 12/31/2015, Land 5,055,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 44,280,850      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 49,335,850      
Accumulated Depreciation (18,496,598)      
Investment in Real Estate Net 30,839,252      
Encumbrances $ 0      
Investment in Real Estate - Partially Owned Unencumbered [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Units 1,661      
Initial Cost to Company, Land $ 40,576,248      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 190,854,337      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 30,715,787      
Gross Amount Carried at close of period 12/31/2015, Land 40,576,248      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 221,570,124      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 262,146,372      
Accumulated Depreciation (96,031,075)      
Investment in Real Estate Net 166,115,297      
Encumbrances $ 0      
Bellevue Meadows [Member]        
Real Estates 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 4,683,238      
Gross Amount Carried at close of period 12/31/2015, Land 4,507,100      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 17,258,052      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 21,765,152      
Accumulated Depreciation (11,286,126)      
Investment in Real Estate Net 10,479,026      
Encumbrances $ 16,538,000      
Canyon Creek (CA) [Member]        
Real Estates 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 18,812,121      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 6,531,309      
Gross Amount Carried at close of period 12/31/2015, Land 5,425,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 25,343,430      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 30,768,430      
Accumulated Depreciation (13,863,495)      
Investment in Real Estate Net 16,904,935      
Encumbrances $ 28,200,000      
Harrison Square (fka Elliot Bay) [Domain]        
Real Estates 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 4,610,519      
Gross Amount Carried at close of period 12/31/2015, Land 7,600,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 40,454,864      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 48,054,864      
Accumulated Depreciation (5,597,458)      
Investment in Real Estate Net $ 42,457,406      
Real Estate And Accumulated Depreciation, Encumbrances Reference [1] (K)      
Isle at Arrowhead Ranch [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Glendale, AZ      
Real Estate And Accumulated Depreciation Units 256      
Initial Cost to Company, Land $ 1,650,237      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 19,593,123      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,399,270      
Gross Amount Carried at close of period 12/31/2015, Land 1,650,237      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 21,992,393      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 23,642,630      
Accumulated Depreciation (13,781,305)      
Investment in Real Estate Net 9,861,325      
Encumbrances $ 17,700,000      
Lantern Cove [Member]        
Real Estates 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 5,882,314      
Gross Amount Carried at close of period 12/31/2015, Land 6,945,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 28,947,290      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 35,892,290      
Accumulated Depreciation (14,983,809)      
Investment in Real Estate Net 20,908,481      
Encumbrances $ 36,455,000      
Schooner Bay I [Member]        
Real Estates 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 4,890,277      
Gross Amount Carried at close of period 12/31/2015, Land 5,345,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 25,280,895      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 30,625,895      
Accumulated Depreciation (13,022,386)      
Investment in Real Estate Net 17,603,509      
Encumbrances $ 28,870,000      
Schooner Bay II [Member]        
Real Estates 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 4,365,840      
Gross Amount Carried at close of period 12/31/2015, Land 4,550,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 22,430,604      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 26,980,604      
Accumulated Depreciation (11,706,487)      
Investment in Real Estate Net 15,274,117      
Encumbrances $ 26,175,000      
Surrey Downs [Member]        
Real Estates 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 2,498,023      
Gross Amount Carried at close of period 12/31/2015, Land 3,057,100      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 10,346,641      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 13,403,741      
Accumulated Depreciation (6,441,879)      
Investment in Real Estate Net 6,961,862      
Encumbrances $ 9,829,000      
Virgil Square [Member]        
Real Estates 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 2,643,870      
Gross Amount Carried at close of period 12/31/2015, Land 5,500,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 17,860,483      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 23,360,483      
Accumulated Depreciation (7,233,630)      
Investment in Real Estate Net 16,126,853      
Encumbrances $ 9,900,000      
Wisconsin Place [Domain]        
Real Estates 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 844,523      
Gross Amount Carried at close of period 12/31/2015, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 172,933,878      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 172,933,878      
Accumulated Depreciation (22,749,424)      
Investment in Real Estate Net 150,184,454      
Encumbrances 145,538,053      
Portfolio Entity Encumbrances [Member]        
Real Estates And Accumulated Depreciation Abstract        
Encumbrances $ 2,112,400,525      
Investment in Real Estate - Partially Owned Encumbered [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Units 2,110      
Initial Cost to Company, Land $ 44,579,437      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 343,499,347      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 39,349,183      
Gross Amount Carried at close of period 12/31/2015, Land 44,579,437      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 382,848,530      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 427,427,967      
Accumulated Depreciation (120,665,999)      
Investment in Real Estate Net 306,761,968      
Encumbrances $ 343,428,578      
Total Consolidated Investment in Real Estate [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Units 79,970      
Initial Cost to Company, Land $ 6,269,047,529      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 17,690,868,530      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,222,435,520      
Gross Amount Carried at close of period 12/31/2015, Land 6,269,047,529      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 18,913,304,050      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 25,182,351,579      
Accumulated Depreciation (4,905,406,012)      
Investment in Real Estate Net 20,276,945,567      
Encumbrances $ 4,563,885,164      
Ashton, The [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Corona Hills, CA      
Real Estate And Accumulated Depreciation Units 492      
Initial Cost to Company, Land $ 2,594,264      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 33,042,397      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 7,170,917      
Gross Amount Carried at close of period 12/31/2015, Land 2,594,264      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 40,213,314      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 42,807,578      
Accumulated Depreciation (26,113,974)      
Investment in Real Estate Net 16,693,604      
Encumbrances $ 0      
Ball Park Lofts [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Denver, CO      
Real Estate And Accumulated Depreciation Units 354      
Initial Cost to Company, Land $ 5,481,556      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 51,658,741      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,998,907      
Gross Amount Carried at close of period 12/31/2015, Land 5,481,556      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 56,657,648      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 62,139,204      
Accumulated Depreciation (23,327,439)      
Investment in Real Estate Net 38,811,765      
Encumbrances $ 0      
Belle Terra [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Mukilteo, WA      
Real Estate And Accumulated Depreciation Units 235      
Initial Cost to Company, Land $ 5,686,861      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 26,070,540      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,295,675      
Gross Amount Carried at close of period 12/31/2015, Land 5,686,861      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 27,366,215      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 33,053,076      
Accumulated Depreciation (11,731,682)      
Investment in Real Estate Net 21,321,394      
Encumbrances $ 0      
Brookside (CO) [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Boulder, CO      
Real Estate And Accumulated Depreciation Units 144      
Initial Cost to Company, Land $ 3,600,400      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 10,211,159      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,816,110      
Gross Amount Carried at close of period 12/31/2015, Land 3,600,400      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 13,027,269      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 16,627,669      
Accumulated Depreciation (7,756,394)      
Investment in Real Estate Net 8,871,275      
Encumbrances $ 0      
Canterbury [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Germantown, MD      
Real Estate And Accumulated Depreciation Units 544      
Initial Cost to Company, Land $ 2,781,300      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 32,942,531      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 15,962,268      
Gross Amount Carried at close of period 12/31/2015, Land 2,781,300      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 48,904,799      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 51,686,099      
Accumulated Depreciation (35,090,051)      
Investment in Real Estate Net 16,596,048      
Encumbrances $ 0      
Cierra Crest [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Denver, CO      
Real Estate And Accumulated Depreciation Units 480      
Initial Cost to Company, Land $ 4,803,100      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 34,894,898      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 6,013,381      
Gross Amount Carried at close of period 12/31/2015, Land 4,803,100      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 40,908,279      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 45,711,379      
Accumulated Depreciation (25,673,488)      
Investment in Real Estate Net 20,037,891      
Encumbrances $ 0      
Coconut Palm Club [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Coconut Creek, FL      
Real Estate And Accumulated Depreciation Units 301      
Initial Cost to Company, Land $ 3,001,700      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 17,678,928      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,535,698      
Gross Amount Carried at close of period 12/31/2015, Land 3,001,700      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 22,214,626      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 25,216,326      
Accumulated Depreciation (13,648,954)      
Investment in Real Estate Net 11,567,372      
Encumbrances $ 0      
Colorado Pointe [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Denver, CO      
Real Estate And Accumulated Depreciation Units 193      
Initial Cost to Company, Land $ 5,790,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 28,815,607      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 841,854      
Gross Amount Carried at close of period 12/31/2015, Land 5,790,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 29,657,461      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 35,447,461      
Accumulated Depreciation (11,304,894)      
Investment in Real Estate Net 24,142,567      
Encumbrances $ 0      
Copper Canyon [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Highlands Ranch, CO      
Real Estate And Accumulated Depreciation Units 222      
Initial Cost to Company, Land $ 1,442,212      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 16,251,114      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,889,129      
Gross Amount Carried at close of period 12/31/2015, Land 1,442,212      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 18,140,243      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 19,582,455      
Accumulated Depreciation (10,551,851)      
Investment in Real Estate Net 9,030,604      
Encumbrances $ 0      
Cove at Boynton Beach I [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Boynton Beach, FL      
Real Estate And Accumulated Depreciation Units 252      
Initial Cost to Company, Land $ 12,600,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 31,469,651      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 5,894,856      
Gross Amount Carried at close of period 12/31/2015, Land 12,600,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 37,364,507      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 49,964,507      
Accumulated Depreciation (16,614,767)      
Investment in Real Estate Net 33,349,740      
Encumbrances $ 0      
Cove at Boynton Beach II [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Boynton Beach, FL      
Real Estate And Accumulated Depreciation Units 296      
Initial Cost to Company, Land $ 14,800,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 37,874,719      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 0      
Gross Amount Carried at close of period 12/31/2015, Land 14,800,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 37,874,719      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 52,674,719      
Accumulated Depreciation (15,535,094)      
Investment in Real Estate Net 37,139,625      
Encumbrances $ 0      
Dartmouth Woods [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Lakewood, CO      
Real Estate And Accumulated Depreciation Units 201      
Initial Cost to Company, Land $ 1,609,800      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 10,832,754      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,604,325      
Gross Amount Carried at close of period 12/31/2015, Land 1,609,800      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 13,437,079      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 15,046,879      
Accumulated Depreciation (8,898,931)      
Investment in Real Estate Net 6,147,948      
Encumbrances $ 0      
Deerwood (Corona) [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Corona, CA      
Real Estate And Accumulated Depreciation Units 316      
Initial Cost to Company, Land $ 4,742,200      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 20,272,892      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,574,232      
Gross Amount Carried at close of period 12/31/2015, Land 4,742,200      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 24,847,124      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 29,589,324      
Accumulated Depreciation (16,204,547)      
Investment in Real Estate Net 13,384,777      
Encumbrances $ 0      
Enclave at Waterways [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Deerfield Beach, FL      
Real Estate And Accumulated Depreciation Units 300      
Initial Cost to Company, Land $ 15,000,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 33,194,576      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,148,558      
Gross Amount Carried at close of period 12/31/2015, Land 15,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 35,343,134      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 50,343,134      
Accumulated Depreciation (14,572,103)      
Investment in Real Estate Net 35,771,031      
Encumbrances $ 0      
Enclave at Winston Park [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Coconut Creek, FL      
Real Estate And Accumulated Depreciation Units 278      
Initial Cost to Company, Land $ 5,560,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 19,939,324      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 5,738,870      
Gross Amount Carried at close of period 12/31/2015, Land 5,560,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 25,678,194      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 31,238,194      
Accumulated Depreciation (12,419,692)      
Investment in Real Estate Net 18,818,502      
Encumbrances $ 0      
Estates at Tanglewood [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Westminster, CO      
Real Estate And Accumulated Depreciation Units 504      
Initial Cost to Company, Land $ 7,560,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 51,256,538      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,230,043      
Gross Amount Carried at close of period 12/31/2015, Land 7,560,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 54,486,581      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 62,046,581      
Accumulated Depreciation (21,626,401)      
Investment in Real Estate Net 40,420,180      
Encumbrances $ 0      
Estates at Wellington Green [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Wellington, FL      
Real Estate And Accumulated Depreciation Units 400      
Initial Cost to Company, Land $ 20,000,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 64,790,850      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,718,719      
Gross Amount Carried at close of period 12/31/2015, Land 20,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 67,509,569      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 87,509,569      
Accumulated Depreciation (26,657,478)      
Investment in Real Estate Net 60,852,091      
Encumbrances $ 0      
Gables Grand Plaza [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Coral Gables, FL      
Real Estate And Accumulated Depreciation Units 195      
Initial Cost to Company, Land $ 0      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 44,601,000      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 7,472,911      
Gross Amount Carried at close of period 12/31/2015, Land 0      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 52,073,911      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 52,073,911      
Accumulated Depreciation (22,657,292)      
Investment in Real Estate Net 29,416,619      
Encumbrances $ 0      
Gatehouse at Pine Lake [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Pembroke Pines, FL      
Real Estate And Accumulated Depreciation Units 296      
Initial Cost to Company, Land $ 1,896,600      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 17,070,795      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 7,166,800      
Gross Amount Carried at close of period 12/31/2015, Land 1,896,600      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 24,237,595      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 26,134,195      
Accumulated Depreciation (15,313,088)      
Investment in Real Estate Net 10,821,107      
Encumbrances $ 0      
Gatehouse on the Green [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Plantation, FL      
Real Estate And Accumulated Depreciation Units 312      
Initial Cost to Company, Land $ 2,228,200      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 20,056,270      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 8,683,372      
Gross Amount Carried at close of period 12/31/2015, Land 2,228,200      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 28,739,642      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 30,967,842      
Accumulated Depreciation (18,755,567)      
Investment in Real Estate Net 12,212,275      
Encumbrances $ 0      
Governors Green [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Bowie, MD      
Real Estate And Accumulated Depreciation Units 478      
Initial Cost to Company, Land $ 19,845,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 73,335,916      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,718,594      
Gross Amount Carried at close of period 12/31/2015, Land 19,845,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 75,054,510      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 94,899,510      
Accumulated Depreciation (25,022,239)      
Investment in Real Estate Net 69,877,271      
Encumbrances $ 0      
Greenwood Park [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Centennial, CO      
Real Estate And Accumulated Depreciation Units 291      
Initial Cost to Company, Land $ 4,365,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 38,372,440      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,824,526      
Gross Amount Carried at close of period 12/31/2015, Land 4,365,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 43,196,966      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 47,561,966      
Accumulated Depreciation (14,493,439)      
Investment in Real Estate Net 33,068,527      
Encumbrances $ 0      
Greenwood Plaza [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Centennial, CO      
Real Estate And Accumulated Depreciation Units 266      
Initial Cost to Company, Land $ 3,990,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 35,846,708      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,827,653      
Gross Amount Carried at close of period 12/31/2015, Land 3,990,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 39,674,361      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 43,664,361      
Accumulated Depreciation (13,920,511)      
Investment in Real Estate Net 29,743,850      
Encumbrances $ 0      
Hammocks Place [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Miami, FL      
Real Estate And Accumulated Depreciation Units 296      
Initial Cost to Company, Land $ 319,180      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 12,513,467      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 6,386,783      
Gross Amount Carried at close of period 12/31/2015, Land 319,180      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 18,900,250      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 19,219,430      
Accumulated Depreciation (13,303,869)      
Investment in Real Estate Net 5,915,561      
Encumbrances $ 0      
Heronfield [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Kirkland, WA      
Real Estate And Accumulated Depreciation Units 202      
Initial Cost to Company, Land $ 9,245,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 27,017,749      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,960,441      
Gross Amount Carried at close of period 12/31/2015, Land 9,245,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 30,978,190      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 40,223,190      
Accumulated Depreciation (10,665,598)      
Investment in Real Estate Net 29,557,592      
Encumbrances $ 0      
Huntington Park [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Everett, WA      
Real Estate And Accumulated Depreciation Units 381      
Initial Cost to Company, Land $ 1,597,500      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 14,367,864      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 5,651,504      
Gross Amount Carried at close of period 12/31/2015, Land 1,597,500      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 20,019,368      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 21,616,868      
Accumulated Depreciation (14,833,511)      
Investment in Real Estate Net 6,783,357      
Encumbrances $ 0      
Kings Colony (FL) [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Miami, FL      
Real Estate And Accumulated Depreciation Units 480      
Initial Cost to Company, Land $ 19,200,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 48,379,586      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 7,396,307      
Gross Amount Carried at close of period 12/31/2015, Land 19,200,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 55,775,893      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 74,975,893      
Accumulated Depreciation (21,996,506)      
Investment in Real Estate Net 52,979,387      
Encumbrances $ 0      
Landings at Pembroke Lakes [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Pembroke Pines, FL      
Real Estate And Accumulated Depreciation Units 358      
Initial Cost to Company, Land $ 17,900,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 24,460,989      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 5,536,019      
Gross Amount Carried at close of period 12/31/2015, Land 17,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 29,997,008      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 47,897,008      
Accumulated Depreciation (14,056,557)      
Investment in Real Estate Net 33,840,451      
Encumbrances $ 0      
Legacy at Highlands Ranch [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Highlands Ranch, CO      
Real Estate And Accumulated Depreciation Units 422      
Initial Cost to Company, Land $ 6,330,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 37,557,013      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,837,915      
Gross Amount Carried at close of period 12/31/2015, Land 6,330,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 40,394,928      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 46,724,928      
Accumulated Depreciation (16,768,231)      
Investment in Real Estate Net 29,956,697      
Encumbrances $ 0      
Marquessa [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Corona Hills, CA      
Real Estate And Accumulated Depreciation Units 336      
Initial Cost to Company, Land $ 6,888,500      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 21,604,584      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,578,245      
Gross Amount Carried at close of period 12/31/2015, Land 6,888,500      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 25,182,829      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 32,071,329      
Accumulated Depreciation (16,010,773)      
Investment in Real Estate Net 16,060,556      
Encumbrances $ 0      
Martine, The [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Bellevue, WA      
Real Estate And Accumulated Depreciation Units 67      
Initial Cost to Company, Land $ 3,200,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 9,616,264      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,314,595      
Gross Amount Carried at close of period 12/31/2015, Land 3,200,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 12,930,859      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 16,130,859      
Accumulated Depreciation (5,125,452)      
Investment in Real Estate Net 11,005,407      
Encumbrances $ 0      
Midtown 24 [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Plantation, FL      
Real Estate And Accumulated Depreciation Units 248      
Initial Cost to Company, Land $ 10,129,900      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 58,770,100      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,836,209      
Gross Amount Carried at close of period 12/31/2015, Land 10,129,900      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 60,606,309      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 70,736,209      
Accumulated Depreciation (13,083,451)      
Investment in Real Estate Net 57,652,758      
Encumbrances $ 0      
Miramar Lakes [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Miramar, FL      
Real Estate And Accumulated Depreciation Units 344      
Initial Cost to Company, Land $ 17,200,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 51,487,235      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,701,577      
Gross Amount Carried at close of period 12/31/2015, Land 17,200,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 54,188,812      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 71,388,812      
Accumulated Depreciation (20,915,774)      
Investment in Real Estate Net 50,473,038      
Encumbrances $ 0      
Mosaic at Largo Station [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Hyattsville, MD      
Real Estate And Accumulated Depreciation Units 242      
Initial Cost to Company, Land $ 4,120,800      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 42,477,297      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 733,047      
Gross Amount Carried at close of period 12/31/2015, Land 4,120,800      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 43,210,344      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 47,331,144      
Accumulated Depreciation (12,991,703)      
Investment in Real Estate Net 34,339,441      
Encumbrances $ 0      
New River Cove [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Davie, FL      
Real Estate And Accumulated Depreciation Units 316      
Initial Cost to Company, Land $ 15,800,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 46,142,895      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,122,060      
Gross Amount Carried at close of period 12/31/2015, Land 15,800,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 50,264,955      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 66,064,955      
Accumulated Depreciation (18,729,270)      
Investment in Real Estate Net 47,335,685      
Encumbrances $ 0      
Northlake (MD) [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Germantown, MD      
Real Estate And Accumulated Depreciation Units 304      
Initial Cost to Company, Land $ 15,000,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 23,142,302      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 10,395,369      
Gross Amount Carried at close of period 12/31/2015, Land 15,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 33,537,671      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 48,537,671      
Accumulated Depreciation (17,973,600)      
Investment in Real Estate Net 30,564,071      
Encumbrances $ 0      
Oak Mill One [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Germantown, MD      
Real Estate And Accumulated Depreciation Units 208      
Initial Cost to Company, Land $ 10,000,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 13,155,522      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 7,759,098      
Gross Amount Carried at close of period 12/31/2015, Land 10,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 20,914,620      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 30,914,620      
Accumulated Depreciation (11,568,469)      
Investment in Real Estate Net 19,346,151      
Encumbrances $ 0      
Oaks at Falls Church [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Falls Church, VA      
Real Estate And Accumulated Depreciation Units 176      
Initial Cost to Company, Land $ 20,240,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 20,152,616      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 4,074,265      
Gross Amount Carried at close of period 12/31/2015, Land 20,240,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 24,226,881      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 44,466,881      
Accumulated Depreciation (10,342,378)      
Investment in Real Estate Net 34,124,503      
Encumbrances $ 0      
Oasis at Delray Beach I [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Delray Beach, FL      
Real Estate And Accumulated Depreciation Units 196      
Initial Cost to Company, Land $ 5,900,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 25,150,766      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,433,675      
Gross Amount Carried at close of period 12/31/2015, Land 5,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 26,584,441      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 32,484,441      
Accumulated Depreciation (4,654,230)      
Investment in Real Estate Net 27,830,211      
Encumbrances $ 0      
Oasis at Delray Beach II [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Delray Beach, FL      
Real Estate And Accumulated Depreciation Units 128      
Initial Cost to Company, Land $ 3,840,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 18,144,955      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 20,701      
Gross Amount Carried at close of period 12/31/2015, Land 3,840,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 18,165,656      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 22,005,656      
Accumulated Depreciation (1,983,415)      
Investment in Real Estate Net 20,022,241      
Encumbrances $ 0      
Orchard Ridge [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Lynnwood, WA      
Real Estate And Accumulated Depreciation Units 104      
Initial Cost to Company, Land $ 480,600      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 4,372,033      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,713,611      
Gross Amount Carried at close of period 12/31/2015, Land 480,600      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 6,085,644      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 6,566,244      
Accumulated Depreciation (4,401,110)      
Investment in Real Estate Net 2,165,134      
Encumbrances $ 0      
Palm Trace Landings [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Davie, FL      
Real Estate And Accumulated Depreciation Units 768      
Initial Cost to Company, Land $ 38,400,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 105,693,432      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 5,925,125      
Gross Amount Carried at close of period 12/31/2015, Land 38,400,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 111,618,557      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 150,018,557      
Accumulated Depreciation (42,732,227)      
Investment in Real Estate Net 107,286,330      
Encumbrances $ 0      
Park Aire [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Wellington, FL      
Real Estate And Accumulated Depreciation Units 268      
Initial Cost to Company, Land $ 8,000,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 40,908,756      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 30,706      
Gross Amount Carried at close of period 12/31/2015, Land 8,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 40,939,462      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 48,939,462      
Accumulated Depreciation (3,974,911)      
Investment in Real Estate Net 44,964,551      
Encumbrances $ 0      
Park at Turtle Run The [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Coral Springs, FL      
Real Estate And Accumulated Depreciation Units 257      
Initial Cost to Company, Land $ 15,420,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 36,064,629      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,581,233      
Gross Amount Carried at close of period 12/31/2015, Land 15,420,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 37,645,862      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 53,065,862      
Accumulated Depreciation (15,394,768)      
Investment in Real Estate Net 37,671,094      
Encumbrances $ 0      
Parkfield [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Denver, CO      
Real Estate And Accumulated Depreciation Units 476      
Initial Cost to Company, Land $ 8,330,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 28,667,618      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,516,386      
Gross Amount Carried at close of period 12/31/2015, Land 8,330,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 32,184,004      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 40,514,004      
Accumulated Depreciation (17,050,355)      
Investment in Real Estate Net 23,463,649      
Encumbrances $ 0      
Preserve at Deer Creek [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Deerfield Beach, FL      
Real Estate And Accumulated Depreciation Units 540      
Initial Cost to Company, Land $ 13,500,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 60,011,208      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 11,825,179      
Gross Amount Carried at close of period 12/31/2015, Land 13,500,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 71,836,387      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 85,336,387      
Accumulated Depreciation (30,159,581)      
Investment in Real Estate Net 55,176,806      
Encumbrances $ 0      
Promenade at Aventura [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Aventura, FL      
Real Estate And Accumulated Depreciation Units 296      
Initial Cost to Company, Land $ 13,320,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 30,353,748      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 7,204,516      
Gross Amount Carried at close of period 12/31/2015, Land 13,320,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 37,558,264      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 50,878,264      
Accumulated Depreciation (19,909,831)      
Investment in Real Estate Net 30,968,433      
Encumbrances $ 0      
Promenade at Wyndham Lakes [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Coral Springs, FL      
Real Estate And Accumulated Depreciation Units 332      
Initial Cost to Company, Land $ 6,640,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 26,743,760      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 5,473,840      
Gross Amount Carried at close of period 12/31/2015, Land 6,640,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 32,217,600      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 38,857,600      
Accumulated Depreciation (17,398,951)      
Investment in Real Estate Net 21,458,649      
Encumbrances $ 0      
Red Road Commons [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Miami, FL      
Real Estate And Accumulated Depreciation Units 404      
Initial Cost to Company, Land $ 27,383,547      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 99,656,440      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,428,548      
Gross Amount Carried at close of period 12/31/2015, Land 27,383,547      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 102,084,988      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 129,468,535      
Accumulated Depreciation (21,124,597)      
Investment in Real Estate Net 108,343,938      
Encumbrances $ 0      
Reserve at Ashley Lake [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Boynton Beach, FL      
Real Estate And Accumulated Depreciation Units 440      
Initial Cost to Company, Land $ 3,520,400      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 23,332,494      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 7,187,407      
Gross Amount Carried at close of period 12/31/2015, Land 3,520,400      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 30,519,901      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 34,040,301      
Accumulated Depreciation (19,863,102)      
Investment in Real Estate Net 14,177,199      
Encumbrances $ 0      
Residences at Bayview [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Pompano Beach, FL      
Real Estate And Accumulated Depreciation Units 225      
Initial Cost to Company, Land $ 5,783,545      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 39,334,455      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,505,813      
Gross Amount Carried at close of period 12/31/2015, Land 5,783,545      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 41,840,268      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 47,623,813      
Accumulated Depreciation (10,722,402)      
Investment in Real Estate Net 36,901,411      
Encumbrances $ 0      
Reunion at Redmond Ridge [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Redmond, WA      
Real Estate And Accumulated Depreciation Units 321      
Initial Cost to Company, Land $ 6,975,705      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 46,175,001      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 433,219      
Gross Amount Carried at close of period 12/31/2015, Land 6,975,705      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 46,608,220      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 53,583,925      
Accumulated Depreciation (12,707,487)      
Investment in Real Estate Net 40,876,438      
Encumbrances $ 0      
Sabal Pointe [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Coral Springs, FL      
Real Estate And Accumulated Depreciation Units 276      
Initial Cost to Company, Land $ 1,951,600      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 17,570,508      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 7,530,196      
Gross Amount Carried at close of period 12/31/2015, Land 1,951,600      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 25,100,704      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 27,052,304      
Accumulated Depreciation (16,637,960)      
Investment in Real Estate Net 10,414,344      
Encumbrances $ 0      
Sage [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Everett, WA      
Real Estate And Accumulated Depreciation Units 123      
Initial Cost to Company, Land $ 2,500,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 12,021,256      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 765,735      
Gross Amount Carried at close of period 12/31/2015, Land 2,500,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 12,786,991      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 15,286,991      
Accumulated Depreciation (5,027,121)      
Investment in Real Estate Net 10,259,870      
Encumbrances $ 0      
Savoy at Dayton Station Combined [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Aurora, CO      
Real Estate And Accumulated Depreciation Units 612      
Initial Cost to Company, Land $ 6,109,460      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 60,039,972      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,773,037      
Gross Amount Carried at close of period 12/31/2015, Land 6,109,460      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 63,813,009      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 69,922,469      
Accumulated Depreciation (22,049,623)      
Investment in Real Estate Net 47,872,846      
Encumbrances $ 0      
Scarborough Square [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Rockville, MD      
Real Estate And Accumulated Depreciation Units 121      
Initial Cost to Company, Land $ 1,815,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 7,608,126      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,166,139      
Gross Amount Carried at close of period 12/31/2015, Land 1,815,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 10,774,265      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 12,589,265      
Accumulated Depreciation (6,919,778)      
Investment in Real Estate Net 5,669,487      
Encumbrances $ 0      
Sheridan Lake Club [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Dania Beach, FL      
Real Estate And Accumulated Depreciation Units 240      
Initial Cost to Company, Land $ 12,000,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 23,170,580      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,068,143      
Gross Amount Carried at close of period 12/31/2015, Land 12,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 25,238,723      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 37,238,723      
Accumulated Depreciation (10,173,850)      
Investment in Real Estate Net 27,064,873      
Encumbrances $ 0      
Sheridan Ocean Club Combined [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Dania Beach, FL      
Real Estate And Accumulated Depreciation Units 648      
Initial Cost to Company, Land $ 18,313,414      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 47,091,594      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 17,913,370      
Gross Amount Carried at close of period 12/31/2015, Land 18,313,414      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 65,004,964      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 83,318,378      
Accumulated Depreciation (35,303,699)      
Investment in Real Estate Net 48,014,679      
Encumbrances $ 0      
St. Andrews at Winston Park [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Coconut Creek, FL      
Real Estate And Accumulated Depreciation Units 284      
Initial Cost to Company, Land $ 5,680,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 19,812,090      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 5,781,847      
Gross Amount Carried at close of period 12/31/2015, Land 5,680,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 25,593,937      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 31,273,937      
Accumulated Depreciation (12,410,235)      
Investment in Real Estate Net 18,863,702      
Encumbrances $ 0      
Stonegate C O [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Broomfield, CO      
Real Estate And Accumulated Depreciation Units 350      
Initial Cost to Company, Land $ 8,750,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 32,950,375      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,317,249      
Gross Amount Carried at close of period 12/31/2015, Land 8,750,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 36,267,624      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 45,017,624      
Accumulated Depreciation (14,957,918)      
Investment in Real Estate Net 30,059,706      
Encumbrances $ 0      
Village at Bear Creek [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Lakewood, CO      
Real Estate And Accumulated Depreciation Units 472      
Initial Cost to Company, Land $ 4,519,700      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 40,676,390      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 5,983,533      
Gross Amount Carried at close of period 12/31/2015, Land 4,519,700      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 46,659,923      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 51,179,623      
Accumulated Depreciation (29,814,286)      
Investment in Real Estate Net 21,365,337      
Encumbrances $ 0      
Waterford Place C O [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Thornton, CO      
Real Estate And Accumulated Depreciation Units 336      
Initial Cost to Company, Land $ 5,040,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 29,946,419      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 2,288,680      
Gross Amount Carried at close of period 12/31/2015, Land 5,040,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 32,235,099      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 37,275,099      
Accumulated Depreciation (14,679,394)      
Investment in Real Estate Net 22,595,705      
Encumbrances $ 0      
Welleby Lake Club [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Sunrise, FL      
Real Estate And Accumulated Depreciation Units 304      
Initial Cost to Company, Land $ 3,648,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 17,620,879      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 6,103,581      
Gross Amount Carried at close of period 12/31/2015, Land 3,648,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 23,724,460      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 27,372,460      
Accumulated Depreciation (14,461,774)      
Investment in Real Estate Net 12,910,686      
Encumbrances $ 0      
Westchester at Pavilions [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Waldorf, MD      
Real Estate And Accumulated Depreciation Units 491      
Initial Cost to Company, Land $ 11,900,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 89,612,465      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 674,086      
Gross Amount Carried at close of period 12/31/2015, Land 11,900,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 90,286,551      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 102,186,551      
Accumulated Depreciation (11,937,856)      
Investment in Real Estate Net 90,248,695      
Encumbrances $ 0      
Winston F L [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Pembroke Pines, FL      
Real Estate And Accumulated Depreciation Units 464      
Initial Cost to Company, Land $ 18,561,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 49,527,569      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 3,675,757      
Gross Amount Carried at close of period 12/31/2015, Land 18,561,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 53,203,326      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 71,764,326      
Accumulated Depreciation (19,941,539)      
Investment in Real Estate Net 51,822,787      
Encumbrances $ 0      
Woodlake WA [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Kirkland, WA      
Real Estate And Accumulated Depreciation Units 288      
Initial Cost to Company, Land $ 6,631,400      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 16,735,484      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 6,286,086      
Gross Amount Carried at close of period 12/31/2015, Land 6,631,400      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 23,021,570      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 29,652,970      
Accumulated Depreciation (12,784,626)      
Investment in Real Estate Net 16,868,344      
Encumbrances $ 0      
Real Estate Held For Sale - Wholly Owned Unencumbered [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Units 21,494      
Initial Cost to Company, Land $ 571,462,444      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 2,250,318,833      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 297,018,230      
Gross Amount Carried at close of period 12/31/2015, Land 571,462,444      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 2,547,337,063      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 3,118,799,507      
Accumulated Depreciation (1,075,431,644)      
Investment in Real Estate Net 2,043,367,863      
Encumbrances $ 0      
Marks [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Englewood, CO      
Real Estate And Accumulated Depreciation Units 616      
Initial Cost to Company, Land $ 4,928,500      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 44,622,314      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 11,819,156      
Gross Amount Carried at close of period 12/31/2015, Land 4,928,500      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 56,441,470      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 61,369,970      
Accumulated Depreciation (36,125,982)      
Investment in Real Estate Net 25,243,988      
Encumbrances $ 19,195,000      
Oak Mill Two [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Germantown, MD      
Real Estate And Accumulated Depreciation Units 192      
Initial Cost to Company, Land $ 854,133      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 10,233,947      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 6,696,831      
Gross Amount Carried at close of period 12/31/2015, Land 854,133      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 16,930,778      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 17,784,911      
Accumulated Depreciation (12,269,574)      
Investment in Real Estate Net 5,515,337      
Encumbrances $ 9,600,000      
Stoney Ridge [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Dale City, VA      
Real Estate And Accumulated Depreciation Units 264      
Initial Cost to Company, Land $ 8,000,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 24,147,091      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 5,964,620      
Gross Amount Carried at close of period 12/31/2015, Land 8,000,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 30,111,711      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 38,111,711      
Accumulated Depreciation (14,096,604)      
Investment in Real Estate Net 24,015,107      
Encumbrances $ 13,000,000      
Uptown Square [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Description Of Location Denver, CO      
Real Estate And Accumulated Depreciation Units 696      
Initial Cost to Company, Land $ 17,492,000      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 100,696,541      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 6,090,227      
Gross Amount Carried at close of period 12/31/2015, Land 17,492,000      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 106,786,768      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 124,278,768      
Accumulated Depreciation (41,286,496)      
Investment in Real Estate Net 82,992,272      
Encumbrances $ 99,190,116      
Real Estate Held For Sale - Wholly Owned Encumbered [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Units 1,768      
Initial Cost to Company, Land $ 31,274,633      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 179,699,893      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 30,570,834      
Gross Amount Carried at close of period 12/31/2015, Land 31,274,633      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 210,270,727      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 241,545,360      
Accumulated Depreciation (103,778,656)      
Investment in Real Estate Net 137,766,704      
Encumbrances $ 140,985,116      
Total Real Estate Held For Sale [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Units 23,262      
Initial Cost to Company, Land $ 602,737,077      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 2,430,018,726      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 327,589,064      
Gross Amount Carried at close of period 12/31/2015, Land 602,737,077      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 2,757,607,790      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 3,360,344,867      
Accumulated Depreciation (1,179,210,300)      
Investment in Real Estate Net 2,181,134,567      
Encumbrances $ 140,985,116      
Total Investment in Real Estate and Real Estate Held For Sale [Member]        
Real Estates And Accumulated Depreciation Abstract        
Real Estate And Accumulated Depreciation Units 103,232      
Initial Cost to Company, Land $ 6,871,784,606      
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements 20,120,887,256      
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures 1,550,024,584      
Gross Amount Carried at close of period 12/31/2015, Land 6,871,784,606      
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures 21,670,911,840      
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures 28,542,696,446      
Accumulated Depreciation (6,084,616,312)      
Investment in Real Estate Net 22,458,080,134      
Encumbrances $ 4,704,870,280      
Unconsolidated Properties [Member]        
Real Estates And Accumulated Depreciation Abstract        
Partially Owned Properties 3      
Number of Units in Real Estate Property 1,281      
Number Of Unconsolidated Projects 2      
Depreciable Property [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Furniture, fixtures and equipment $ 1,542,662,923      
Building [Member]        
Real Estates And Accumulated Depreciation Abstract        
Property, Plant and Equipment, Estimated Useful Lives 30      
Renovations and Improvements Minimum [Member]        
Real Estates And Accumulated Depreciation Abstract        
Property, Plant and Equipment, Estimated Useful Lives 5      
Renovations and Improvements Maximum [Member]        
Real Estates And Accumulated Depreciation Abstract        
Property, Plant and Equipment, Estimated Useful Lives 15      
Replacements Minimum [Member]        
Real Estates And Accumulated Depreciation Abstract        
Property, Plant and Equipment, Estimated Useful Lives 5      
Replacements Maximum [Member]        
Real Estates And Accumulated Depreciation Abstract        
Property, Plant and Equipment, Estimated Useful Lives 10      
Management Business Renovations and Improvements Minimum [Member] [Member]        
Real Estates And Accumulated Depreciation Abstract        
Property, Plant and Equipment, Estimated Useful Lives 3      
Management Business Renovations and Improvements Maximum [Member] [Member]        
Real Estates And Accumulated Depreciation Abstract        
Property, Plant and Equipment, Estimated Useful Lives 7      
Wholly Owned Encumbered [Member] | Portfolio Entity Encumbrances [Member]        
Real Estates And Accumulated Depreciation Abstract        
Encumbrances $ 2,088,177,000      
Wholly Owned Encumbered [Member] | Total Consolidated Investment in Real Estate [Member]        
Real Estates And Accumulated Depreciation Abstract        
Encumbrances 4,220,456,586      
Wholly Owned Encumbered [Member] | Total Investment in Real Estate and Real Estate Held For Sale [Member]        
Real Estates And Accumulated Depreciation Abstract        
Encumbrances 4,361,441,702      
Partially Owned Encumbered [Member] | Portfolio Entity Encumbrances [Member]        
Real Estates And Accumulated Depreciation Abstract        
Encumbrances 24,223,525      
Partially Owned Encumbered [Member] | Total Consolidated Investment in Real Estate [Member]        
Real Estates And Accumulated Depreciation Abstract        
Encumbrances 343,428,578      
Partially Owned Encumbered [Member] | Total Investment in Real Estate and Real Estate Held For Sale [Member]        
Real Estates And Accumulated Depreciation Abstract        
Encumbrances $ 343,428,578      
[1] (I)through (L) See Encumbrances Reconciliation schedule.