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SCHEDULE III - REAL ESTATE AND ACCUMULATED DEPRECIATION (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2020
Dec. 31, 2019
Gross amount at which carries at close of period [Abstract]        
Accumulated Depreciation $ (399,249) $ (353,871) $ (399,249) $ (349,122)
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Total real estate investments     1,437,969 1,311,472
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Accumulated Depreciation [Roll Forward]        
Balance at beginning of year 349,122 353,871    
Additions during year [Abstract]        
Provisions for depreciation 72,051 71,787    
Deductions during year [Abstract]        
Accumulated depreciation on real estate sold or classified as held for sale (21,440) (72,758)    
Write down of asset and accumulated depreciation on impaired assets 0 0    
Other (484) (3,778)    
Balance at close of year 399,249 349,122    
Net basis of real estate investments for federal income tax purposes     1,400,000 1,300,000
Unimproved Land        
Gross amount at which carries at close of period [Abstract]        
Total 1,376 1,376 0 1,376
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at beginning of year 1,376 5,301    
Cost of real estate sold (1,376) (3,925)    
Balance at close of year 0 1,376    
Total real estate investments     1,413,308 1,295,332
Wholly Owned Properties        
Gross amount at which carries at close of period [Abstract]        
Total 1,643,078 1,643,078 1,812,557 $ 1,643,078
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at beginning of year 1,643,078 1,627,636    
Improvements and Other 27,460 21,868    
Total Additions 1,852,309 1,818,008    
Cost of real estate sold (38,111) (171,112)    
Other (1,641) (3,818)    
Balance at close of year 1,812,557 1,643,078    
MultiFamily Same-Store        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     276,770  
Initial Cost to Company [Abstract]        
Land     119,580  
Buildings & Improvements     1,143,758  
Costs capitalized subsequent to acquisition     160,871  
Gross amount at which carries at close of period [Abstract]        
Land     137,250  
Buildings & Improvements     1,286,959  
Total 1,424,209   1,424,209  
Accumulated Depreciation (375,942)   (375,942)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 1,424,209      
Deductions during year [Abstract]        
Balance at close of year 375,942      
MultiFamily Same-Store | 71 France - Edina, MN        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     53,324  
Initial Cost to Company [Abstract]        
Land     4,721  
Buildings & Improvements     61,762  
Costs capitalized subsequent to acquisition     446  
Gross amount at which carries at close of period [Abstract]        
Land     4,801  
Buildings & Improvements     62,128  
Total 66,929   66,929  
Accumulated Depreciation (14,312)   (14,312)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 66,929      
Deductions during year [Abstract]        
Balance at close of year 14,312      
MultiFamily Same-Store | Alps Park - Rapid City, SD        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     287  
Buildings & Improvements     5,551  
Costs capitalized subsequent to acquisition     425  
Gross amount at which carries at close of period [Abstract]        
Land     336  
Buildings & Improvements     5,927  
Total 6,263   6,263  
Accumulated Depreciation (1,589)   (1,589)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 6,263      
Deductions during year [Abstract]        
Balance at close of year 1,589      
MultiFamily Same-Store | Arcata - Golden Valley, MN        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     2,088  
Buildings & Improvements     31,036  
Costs capitalized subsequent to acquisition     356  
Gross amount at which carries at close of period [Abstract]        
Land     2,128  
Buildings & Improvements     31,352  
Total 33,480   33,480  
Accumulated Depreciation (8,600)   (8,600)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 33,480      
Deductions during year [Abstract]        
Balance at close of year 8,600      
MultiFamily Same-Store | Ashland - Grand Forks, ND        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     4,866  
Initial Cost to Company [Abstract]        
Land     741  
Buildings & Improvements     7,569  
Costs capitalized subsequent to acquisition     346  
Gross amount at which carries at close of period [Abstract]        
Land     823  
Buildings & Improvements     7,833  
Total 8,656   8,656  
Accumulated Depreciation (2,323)   (2,323)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 8,656      
Deductions during year [Abstract]        
Balance at close of year 2,323      
MultiFamily Same-Store | Avalon Cove - Rochester, MN        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     1,616  
Buildings & Improvements     34,074  
Costs capitalized subsequent to acquisition     646  
Gross amount at which carries at close of period [Abstract]        
Land     1,808  
Buildings & Improvements     34,528  
Total 36,336   36,336  
Accumulated Depreciation (5,927)   (5,927)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 36,336      
Deductions during year [Abstract]        
Balance at close of year 5,927      
MultiFamily Same-Store | Boulder Court - Eagan, MN        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     1,067  
Buildings & Improvements     5,498  
Costs capitalized subsequent to acquisition     3,305  
Gross amount at which carries at close of period [Abstract]        
Land     1,576  
Buildings & Improvements     8,294  
Total 9,870   9,870  
Accumulated Depreciation (4,429)   (4,429)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 9,870      
Deductions during year [Abstract]        
Balance at close of year 4,429      
MultiFamily Same-Store | Canyon Lake - Rapid City, SD        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     2,508  
Initial Cost to Company [Abstract]        
Land     305  
Buildings & Improvements     3,958  
Costs capitalized subsequent to acquisition     2,266  
Gross amount at which carries at close of period [Abstract]        
Land     420  
Buildings & Improvements     6,109  
Total 6,529   6,529  
Accumulated Depreciation (3,208)   (3,208)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 6,529      
Deductions during year [Abstract]        
Balance at close of year 3,208      
MultiFamily Same-Store | Cardinal Point - Grand Forks, ND        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     1,600  
Buildings & Improvements     33,400  
Costs capitalized subsequent to acquisition     288  
Gross amount at which carries at close of period [Abstract]        
Land     1,727  
Buildings & Improvements     33,561  
Total 35,288   35,288  
Accumulated Depreciation (2,971)   (2,971)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 35,288      
Deductions during year [Abstract]        
Balance at close of year 2,971      
MultiFamily Same-Store | Cascade Shores - Rochester, MN        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     11,400  
Initial Cost to Company [Abstract]        
Land     1,585  
Buildings & Improvements     16,710  
Costs capitalized subsequent to acquisition     149  
Gross amount at which carries at close of period [Abstract]        
Land     1,587  
Buildings & Improvements     16,857  
Total 18,444   18,444  
Accumulated Depreciation (2,967)   (2,967)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 18,444      
Deductions during year [Abstract]        
Balance at close of year 2,967      
MultiFamily Same-Store | Castlerock - Billings, MT        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     736  
Buildings & Improvements     4,864  
Costs capitalized subsequent to acquisition     2,538  
Gross amount at which carries at close of period [Abstract]        
Land     1,045  
Buildings & Improvements     7,093  
Total 8,138   8,138  
Accumulated Depreciation (4,549)   (4,549)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 8,138      
Deductions during year [Abstract]        
Balance at close of year 4,549      
MultiFamily Same-Store | Chateau - Minot, ND        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     301  
Buildings & Improvements     20,058  
Costs capitalized subsequent to acquisition     1,094  
Gross amount at which carries at close of period [Abstract]        
Land     326  
Buildings & Improvements     21,127  
Total 21,453   21,453  
Accumulated Depreciation (6,119)   (6,119)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 21,453      
Deductions during year [Abstract]        
Balance at close of year 6,119      
MultiFamily Same-Store | Cimarron Hills - Omaha, NE        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     8,700  
Initial Cost to Company [Abstract]        
Land     706  
Buildings & Improvements     9,588  
Costs capitalized subsequent to acquisition     5,214  
Gross amount at which carries at close of period [Abstract]        
Land     1,639  
Buildings & Improvements     13,869  
Total 15,508   15,508  
Accumulated Depreciation (7,858)   (7,858)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 15,508      
Deductions during year [Abstract]        
Balance at close of year 7,858      
MultiFamily Same-Store | Colonial Villa - Burnsville, MN        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     2,401  
Buildings & Improvements     11,515  
Costs capitalized subsequent to acquisition     15,595  
Gross amount at which carries at close of period [Abstract]        
Land     3,206  
Buildings & Improvements     26,305  
Total 29,511   29,511  
Accumulated Depreciation (12,940)   (12,940)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 29,511      
Deductions during year [Abstract]        
Balance at close of year 12,940      
MultiFamily Same-Store | Colony - Lincoln, NE        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     11,610  
Initial Cost to Company [Abstract]        
Land     1,515  
Buildings & Improvements     15,730  
Costs capitalized subsequent to acquisition     3,131  
Gross amount at which carries at close of period [Abstract]        
Land     1,817  
Buildings & Improvements     18,559  
Total 20,376   20,376  
Accumulated Depreciation (5,412)   (5,412)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 20,376      
Deductions during year [Abstract]        
Balance at close of year 5,412      
MultiFamily Same-Store | Commons at Southgate - Minot, ND        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     5,945  
Buildings & Improvements     47,512  
Costs capitalized subsequent to acquisition     2,059  
Gross amount at which carries at close of period [Abstract]        
Land     6,424  
Buildings & Improvements     49,092  
Total 55,516   55,516  
Accumulated Depreciation (14,012)   (14,012)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 55,516      
Deductions during year [Abstract]        
Balance at close of year 14,012      
MultiFamily Same-Store | Cottonwood - Bismarck, ND        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     1,056  
Buildings & Improvements     17,372  
Costs capitalized subsequent to acquisition     6,053  
Gross amount at which carries at close of period [Abstract]        
Land     1,962  
Buildings & Improvements     22,519  
Total 24,481   24,481  
Accumulated Depreciation (12,455)   (12,455)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 24,481      
Deductions during year [Abstract]        
Balance at close of year 12,455      
MultiFamily Same-Store | Country Meadows - Billings, MT        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     491  
Buildings & Improvements     7,809  
Costs capitalized subsequent to acquisition     1,845  
Gross amount at which carries at close of period [Abstract]        
Land     599  
Buildings & Improvements     9,546  
Total 10,145   10,145  
Accumulated Depreciation (5,858)   (5,858)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 10,145      
Deductions during year [Abstract]        
Balance at close of year 5,858      
MultiFamily Same-Store | Crystal Bay - Rochester, MN        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     433  
Buildings & Improvements     11,425  
Costs capitalized subsequent to acquisition     360  
Gross amount at which carries at close of period [Abstract]        
Land     479  
Buildings & Improvements     11,739  
Total 12,218   12,218  
Accumulated Depreciation (1,984)   (1,984)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 12,218      
Deductions during year [Abstract]        
Balance at close of year 1,984      
MultiFamily Same-Store | Cypress Court - St. Cloud, MN        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     11,641  
Initial Cost to Company [Abstract]        
Land     1,583  
Buildings & Improvements     18,879  
Costs capitalized subsequent to acquisition     474  
Gross amount at which carries at close of period [Abstract]        
Land     1,625  
Buildings & Improvements     19,311  
Total 20,936   20,936  
Accumulated Depreciation (5,409)   (5,409)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 20,936      
Deductions during year [Abstract]        
Balance at close of year 5,409      
MultiFamily Same-Store | Deer Ridge - Jamestown, ND        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     711  
Buildings & Improvements     24,129  
Costs capitalized subsequent to acquisition     322  
Gross amount at which carries at close of period [Abstract]        
Land     785  
Buildings & Improvements     24,377  
Total 25,162   25,162  
Accumulated Depreciation (6,224)   (6,224)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 25,162      
Deductions during year [Abstract]        
Balance at close of year 6,224      
MultiFamily Same-Store | Dylan - Denver Co        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     12,155  
Buildings & Improvements     77,215  
Costs capitalized subsequent to acquisition     1,030  
Gross amount at which carries at close of period [Abstract]        
Land     12,241  
Buildings & Improvements     78,159  
Total 90,400   90,400  
Accumulated Depreciation $ (8,205)   (8,205)  
Life on which depreciation in latest income statement is computed 30 years      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year $ 90,400      
Deductions during year [Abstract]        
Balance at close of year 8,205      
MultiFamily Same-Store | Evergreen - Isanti, MN        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     1,129  
Buildings & Improvements     5,524  
Costs capitalized subsequent to acquisition     569  
Gross amount at which carries at close of period [Abstract]        
Land     1,159  
Buildings & Improvements     6,063  
Total 7,222   7,222  
Accumulated Depreciation (2,041)   (2,041)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 7,222      
Deductions during year [Abstract]        
Balance at close of year 2,041      
MultiFamily Same-Store | French Creek - Rochester, MN        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     201  
Buildings & Improvements     4,735  
Costs capitalized subsequent to acquisition     256  
Gross amount at which carries at close of period [Abstract]        
Land     212  
Buildings & Improvements     4,980  
Total 5,192   5,192  
Accumulated Depreciation (809)   (809)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 5,192      
Deductions during year [Abstract]        
Balance at close of year 809      
MultiFamily Same-Store | Gardens - Grand Forks, ND        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     518  
Buildings & Improvements     8,702  
Costs capitalized subsequent to acquisition     132  
Gross amount at which carries at close of period [Abstract]        
Land     535  
Buildings & Improvements     8,817  
Total 9,352   9,352  
Accumulated Depreciation (1,759)   (1,759)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 9,352      
Deductions during year [Abstract]        
Balance at close of year 1,759      
MultiFamily Same-Store | Grand Gateway - St. Cloud, MN        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     814  
Buildings & Improvements     7,086  
Costs capitalized subsequent to acquisition     2,064  
Gross amount at which carries at close of period [Abstract]        
Land     970  
Buildings & Improvements     8,994  
Total 9,964   9,964  
Accumulated Depreciation (3,480)   (3,480)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 9,964      
Deductions during year [Abstract]        
Balance at close of year 3,480      
MultiFamily Same-Store | GrandeVille at Cascade Lake - Rochester, MN        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     36,000  
Initial Cost to Company [Abstract]        
Land     5,003  
Buildings & Improvements     50,363  
Costs capitalized subsequent to acquisition     2,089  
Gross amount at which carries at close of period [Abstract]        
Land     5,188  
Buildings & Improvements     52,267  
Total 57,455   57,455  
Accumulated Depreciation (10,304)   (10,304)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 57,455      
Deductions during year [Abstract]        
Balance at close of year 10,304      
MultiFamily Same-Store | Greenfield - Omaha, NE        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     578  
Buildings & Improvements     4,122  
Costs capitalized subsequent to acquisition     2,652  
Gross amount at which carries at close of period [Abstract]        
Land     876  
Buildings & Improvements     6,476  
Total 7,352   7,352  
Accumulated Depreciation (2,425)   (2,425)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 7,352      
Deductions during year [Abstract]        
Balance at close of year 2,425      
MultiFamily Same-Store | Heritage Manor - Rochester, MN        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     403  
Buildings & Improvements     6,968  
Costs capitalized subsequent to acquisition     3,741  
Gross amount at which carries at close of period [Abstract]        
Land     790  
Buildings & Improvements     10,322  
Total 11,112   11,112  
Accumulated Depreciation (6,243)   (6,243)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 11,112      
Deductions during year [Abstract]        
Balance at close of year 6,243      
MultiFamily Same-Store | Homestead Garden - Rapid City, SD        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     655  
Buildings & Improvements     14,139  
Costs capitalized subsequent to acquisition     540  
Gross amount at which carries at close of period [Abstract]        
Land     792  
Buildings & Improvements     14,542  
Total 15,334   15,334  
Accumulated Depreciation (3,427)   (3,427)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 15,334      
Deductions during year [Abstract]        
Balance at close of year 3,427      
MultiFamily Same-Store | Lakeside Village Lincoln, NE        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     11,489  
Initial Cost to Company [Abstract]        
Land     1,215  
Buildings & Improvements     15,837  
Costs capitalized subsequent to acquisition     1,850  
Gross amount at which carries at close of period [Abstract]        
Land     1,476  
Buildings & Improvements     17,426  
Total 18,902   18,902  
Accumulated Depreciation (5,230)   (5,230)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 18,902      
Deductions during year [Abstract]        
Balance at close of year 5,230      
MultiFamily Same-Store | Legacy - Grand Forks, ND        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     13,072  
Initial Cost to Company [Abstract]        
Land     1,362  
Buildings & Improvements     21,727  
Costs capitalized subsequent to acquisition     11,044  
Gross amount at which carries at close of period [Abstract]        
Land     2,474  
Buildings & Improvements     31,659  
Total 34,133   34,133  
Accumulated Depreciation (18,730)   (18,730)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 34,133      
Deductions during year [Abstract]        
Balance at close of year 18,730      
MultiFamily Same-Store | Legacy Heights - Bismarck, ND        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     1,207  
Buildings & Improvements     13,742  
Costs capitalized subsequent to acquisition     257  
Gross amount at which carries at close of period [Abstract]        
Land     1,142  
Buildings & Improvements     14,064  
Total 15,206   15,206  
Accumulated Depreciation (2,604)   (2,604)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 15,206      
Deductions during year [Abstract]        
Balance at close of year 2,604      
MultiFamily Same-Store | Meadows - Jamestown, ND        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     590  
Buildings & Improvements     4,519  
Costs capitalized subsequent to acquisition     2,087  
Gross amount at which carries at close of period [Abstract]        
Land     730  
Buildings & Improvements     6,466  
Total 7,196   7,196  
Accumulated Depreciation (3,788)   (3,788)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 7,196      
Deductions during year [Abstract]        
Balance at close of year 3,788      
MultiFamily Same-Store | Monticello Crossings - Monticello, MN        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     1,734  
Buildings & Improvements     30,136  
Costs capitalized subsequent to acquisition     376  
Gross amount at which carries at close of period [Abstract]        
Land     1,951  
Buildings & Improvements     30,295  
Total 32,246   32,246  
Accumulated Depreciation (5,407)   (5,407)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 32,246      
Deductions during year [Abstract]        
Balance at close of year 5,407      
MultiFamily Same-Store | Monticello Village - Monticello, MN        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     490  
Buildings & Improvements     3,756  
Costs capitalized subsequent to acquisition     1,234  
Gross amount at which carries at close of period [Abstract]        
Land     655  
Buildings & Improvements     4,825  
Total 5,480   5,480  
Accumulated Depreciation (2,434)   (2,434)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 5,480      
Deductions during year [Abstract]        
Balance at close of year 2,434      
MultiFamily Same-Store | Northridge - Bismarck, ND        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     884  
Buildings & Improvements     7,515  
Costs capitalized subsequent to acquisition     278  
Gross amount at which carries at close of period [Abstract]        
Land     1,048  
Buildings & Improvements     7,629  
Total 8,677   8,677  
Accumulated Depreciation (1,641)   (1,641)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 8,677      
Deductions during year [Abstract]        
Balance at close of year 1,641      
MultiFamily Same-Store | Olympic Village - Billings, MT        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     1,164  
Buildings & Improvements     10,441  
Costs capitalized subsequent to acquisition     4,175  
Gross amount at which carries at close of period [Abstract]        
Land     1,885  
Buildings & Improvements     13,895  
Total 15,780   15,780  
Accumulated Depreciation (8,287)   (8,287)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 15,780      
Deductions during year [Abstract]        
Balance at close of year 8,287      
MultiFamily Same-Store | Olympik Village - Rochester, MN        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     1,034  
Buildings & Improvements     6,109  
Costs capitalized subsequent to acquisition     3,459  
Gross amount at which carries at close of period [Abstract]        
Land     1,450  
Buildings & Improvements     9,152  
Total 10,602   10,602  
Accumulated Depreciation (4,136)   (4,136)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 10,602      
Deductions during year [Abstract]        
Balance at close of year 4,136      
MultiFamily Same-Store | Oxbo - St Paul, MN        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     5,809  
Buildings & Improvements     51,586  
Costs capitalized subsequent to acquisition     214  
Gross amount at which carries at close of period [Abstract]        
Land     5,822  
Buildings & Improvements     51,787  
Total 57,609   57,609  
Accumulated Depreciation $ (7,107)   (7,107)  
Life on which depreciation in latest income statement is computed 30 years      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year $ 57,609      
Deductions during year [Abstract]        
Balance at close of year 7,107      
MultiFamily Same-Store | Park Meadows - Waite Park, MN        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     1,143  
Buildings & Improvements     9,099  
Costs capitalized subsequent to acquisition     10,277  
Gross amount at which carries at close of period [Abstract]        
Land     2,140  
Buildings & Improvements     18,379  
Total 20,519   20,519  
Accumulated Depreciation (12,605)   (12,605)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 20,519      
Deductions during year [Abstract]        
Balance at close of year 12,605      
MultiFamily Same-Store | Park Place - Plymouth, MN        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     10,609  
Buildings & Improvements     80,781  
Costs capitalized subsequent to acquisition     10,433  
Gross amount at which carries at close of period [Abstract]        
Land     10,819  
Buildings & Improvements     91,004  
Total 101,823   101,823  
Accumulated Depreciation $ (11,303)   (11,303)  
Life on which depreciation in latest income statement is computed 30 years      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year $ 101,823      
Deductions during year [Abstract]        
Balance at close of year 11,303      
MultiFamily Same-Store | Plaza - Minot, ND        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     867  
Buildings & Improvements     12,784  
Costs capitalized subsequent to acquisition     3,128  
Gross amount at which carries at close of period [Abstract]        
Land     1,011  
Buildings & Improvements     15,768  
Total 16,779   16,779  
Accumulated Depreciation (5,734)   (5,734)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 16,779      
Deductions during year [Abstract]        
Balance at close of year 5,734      
MultiFamily Same-Store | Pointe West - Rapid City, SD        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     240  
Buildings & Improvements     3,538  
Costs capitalized subsequent to acquisition     2,185  
Gross amount at which carries at close of period [Abstract]        
Land     463  
Buildings & Improvements     5,500  
Total 5,963   5,963  
Accumulated Depreciation (3,865)   (3,865)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 5,963      
Deductions during year [Abstract]        
Balance at close of year 3,865      
MultiFamily Same-Store | Ponds at Heritage Place - Sartell, MN        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     395  
Buildings & Improvements     4,564  
Costs capitalized subsequent to acquisition     510  
Gross amount at which carries at close of period [Abstract]        
Land     419  
Buildings & Improvements     5,050  
Total 5,469   5,469  
Accumulated Depreciation (1,539)   (1,539)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 5,469      
Deductions during year [Abstract]        
Balance at close of year 1,539      
MultiFamily Same-Store | Quarry Ridge - Rochester, MN        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     24,057  
Initial Cost to Company [Abstract]        
Land     2,254  
Buildings & Improvements     30,024  
Costs capitalized subsequent to acquisition     2,356  
Gross amount at which carries at close of period [Abstract]        
Land     2,412  
Buildings & Improvements     32,222  
Total 34,634   34,634  
Accumulated Depreciation (10,969)   (10,969)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 34,634      
Deductions during year [Abstract]        
Balance at close of year 10,969      
MultiFamily Same-Store | Red 20 - Minneapolis, MN        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     21,274  
Initial Cost to Company [Abstract]        
Land     1,900  
Buildings & Improvements     24,116  
Costs capitalized subsequent to acquisition     397  
Gross amount at which carries at close of period [Abstract]        
Land     1,908  
Buildings & Improvements     24,505  
Total 26,413   26,413  
Accumulated Depreciation (6,829)   (6,829)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 26,413      
Deductions during year [Abstract]        
Balance at close of year 6,829      
MultiFamily Same-Store | Regency Park Estates - St. Cloud, MN        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     7,400  
Initial Cost to Company [Abstract]        
Land     702  
Buildings & Improvements     10,198  
Costs capitalized subsequent to acquisition     3,337  
Gross amount at which carries at close of period [Abstract]        
Land     1,179  
Buildings & Improvements     13,058  
Total 14,237   14,237  
Accumulated Depreciation (4,394)   (4,394)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 14,237      
Deductions during year [Abstract]        
Balance at close of year 4,394      
MultiFamily Same-Store | Rimrock West - Billings, MT        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     330  
Buildings & Improvements     3,489  
Costs capitalized subsequent to acquisition     2,157  
Gross amount at which carries at close of period [Abstract]        
Land     568  
Buildings & Improvements     5,408  
Total 5,976   5,976  
Accumulated Depreciation (3,250)   (3,250)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 5,976      
Deductions during year [Abstract]        
Balance at close of year 3,250      
MultiFamily Same-Store | River Ridge - Bismarck, ND        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     576  
Buildings & Improvements     24,670  
Costs capitalized subsequent to acquisition     1,092  
Gross amount at which carries at close of period [Abstract]        
Land     922  
Buildings & Improvements     25,416  
Total 26,338   26,338  
Accumulated Depreciation (8,025)   (8,025)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 26,338      
Deductions during year [Abstract]        
Balance at close of year 8,025      
MultiFamily Same-Store | Rocky Meadows - Billings, MT        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     656  
Buildings & Improvements     5,726  
Costs capitalized subsequent to acquisition     1,745  
Gross amount at which carries at close of period [Abstract]        
Land     840  
Buildings & Improvements     7,287  
Total 8,127   8,127  
Accumulated Depreciation (4,687)   (4,687)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 8,127      
Deductions during year [Abstract]        
Balance at close of year 4,687      
MultiFamily Same-Store | Rum River - Isanti, MN        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     3,041  
Initial Cost to Company [Abstract]        
Land     843  
Buildings & Improvements     4,823  
Costs capitalized subsequent to acquisition     544  
Gross amount at which carries at close of period [Abstract]        
Land     870  
Buildings & Improvements     5,340  
Total 6,210   6,210  
Accumulated Depreciation (2,162)   (2,162)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 6,210      
Deductions during year [Abstract]        
Balance at close of year 2,162      
MultiFamily Same-Store | Silver Springs - Rapid City, SD        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     1,997  
Initial Cost to Company [Abstract]        
Land     215  
Buildings & Improvements     3,007  
Costs capitalized subsequent to acquisition     890  
Gross amount at which carries at close of period [Abstract]        
Land     273  
Buildings & Improvements     3,839  
Total 4,112   4,112  
Accumulated Depreciation (958)   (958)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 4,112      
Deductions during year [Abstract]        
Balance at close of year 958      
MultiFamily Same-Store | South Pointe - Minot, ND        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     550  
Buildings & Improvements     9,548  
Costs capitalized subsequent to acquisition     5,990  
Gross amount at which carries at close of period [Abstract]        
Land     1,489  
Buildings & Improvements     14,599  
Total 16,088   16,088  
Accumulated Depreciation (10,311)   (10,311)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 16,088      
Deductions during year [Abstract]        
Balance at close of year 10,311      
MultiFamily Same-Store | Southpoint - Grand Forks, ND        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     576  
Buildings & Improvements     9,893  
Costs capitalized subsequent to acquisition     236  
Gross amount at which carries at close of period [Abstract]        
Land     663  
Buildings & Improvements     10,042  
Total 10,705   10,705  
Accumulated Depreciation (2,293)   (2,293)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 10,705      
Deductions during year [Abstract]        
Balance at close of year 2,293      
MultiFamily Same-Store | Sunset Trail - Rochester, MN        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     336  
Buildings & Improvements     12,814  
Costs capitalized subsequent to acquisition     3,560  
Gross amount at which carries at close of period [Abstract]        
Land     826  
Buildings & Improvements     15,884  
Total 16,710   16,710  
Accumulated Depreciation (9,024)   (9,024)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 16,710      
Deductions during year [Abstract]        
Balance at close of year 9,024      
MultiFamily Same-Store | Thomasbrook - Lincoln, NE        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     13,100  
Initial Cost to Company [Abstract]        
Land     600  
Buildings & Improvements     10,306  
Costs capitalized subsequent to acquisition     5,686  
Gross amount at which carries at close of period [Abstract]        
Land     1,710  
Buildings & Improvements     14,882  
Total 16,592   16,592  
Accumulated Depreciation (8,563)   (8,563)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 16,592      
Deductions during year [Abstract]        
Balance at close of year 8,563      
MultiFamily Same-Store | Village Green - Rochester, MN        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     234  
Buildings & Improvements     2,296  
Costs capitalized subsequent to acquisition     1,083  
Gross amount at which carries at close of period [Abstract]        
Land     361  
Buildings & Improvements     3,252  
Total 3,613   3,613  
Accumulated Depreciation (1,682)   (1,682)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 3,613      
Deductions during year [Abstract]        
Balance at close of year 1,682      
MultiFamily Same-Store | West Stonehill - Waite Park, MN        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     16,425  
Initial Cost to Company [Abstract]        
Land     939  
Buildings & Improvements     10,167  
Costs capitalized subsequent to acquisition     8,171  
Gross amount at which carries at close of period [Abstract]        
Land     1,912  
Buildings & Improvements     17,365  
Total 19,277   19,277  
Accumulated Depreciation (12,060)   (12,060)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 19,277      
Deductions during year [Abstract]        
Balance at close of year 12,060      
MultiFamily Same-Store | Westend - Denver CO        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     25,525  
Buildings & Improvements     102,180  
Costs capitalized subsequent to acquisition     605  
Gross amount at which carries at close of period [Abstract]        
Land     25,532  
Buildings & Improvements     102,778  
Total 128,310   128,310  
Accumulated Depreciation $ (9,952)   (9,952)  
Life on which depreciation in latest income statement is computed 30 years      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year $ 128,310      
Deductions during year [Abstract]        
Balance at close of year 9,952      
MultiFamily Same-Store | Whispering Ridge - Omaha, NE        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     19,664  
Initial Cost to Company [Abstract]        
Land     2,139  
Buildings & Improvements     25,424  
Costs capitalized subsequent to acquisition     2,992  
Gross amount at which carries at close of period [Abstract]        
Land     2,551  
Buildings & Improvements     28,004  
Total 30,555   30,555  
Accumulated Depreciation (7,850)   (7,850)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 30,555      
Deductions during year [Abstract]        
Balance at close of year 7,850      
MultiFamily Same-Store | Winchester - Rochester, MN        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     748  
Buildings & Improvements     5,622  
Costs capitalized subsequent to acquisition     3,040  
Gross amount at which carries at close of period [Abstract]        
Land     1,112  
Buildings & Improvements     8,298  
Total 9,410   9,410  
Accumulated Depreciation (4,418)   (4,418)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 9,410      
Deductions during year [Abstract]        
Balance at close of year 4,418      
MultiFamily Same-Store | Woodridge - Rochester, MN        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     5,202  
Initial Cost to Company [Abstract]        
Land     370  
Buildings & Improvements     6,028  
Costs capitalized subsequent to acquisition     5,498  
Gross amount at which carries at close of period [Abstract]        
Land     761  
Buildings & Improvements     11,135  
Total 11,896   11,896  
Accumulated Depreciation (6,266)   (6,266)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 11,896      
Deductions during year [Abstract]        
Balance at close of year $ 6,266      
MultiFamily Same-Store | Minimum | 71 France - Edina, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Alps Park - Rapid City, SD        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Ashland - Grand Forks, ND        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Avalon Cove - Rochester, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Boulder Court - Eagan, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Canyon Lake - Rapid City, SD        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Cardinal Point - Grand Forks, ND        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Cascade Shores - Rochester, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Castlerock - Billings, MT        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Chateau - Minot, ND        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Cimarron Hills - Omaha, NE        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Colonial Villa - Burnsville, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Colony - Lincoln, NE        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Commons at Southgate - Minot, ND        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Cottonwood - Bismarck, ND        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Country Meadows - Billings, MT        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Crystal Bay - Rochester, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Cypress Court - St. Cloud, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Deer Ridge - Jamestown, ND        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Evergreen - Isanti, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | French Creek - Rochester, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Gardens - Grand Forks, ND        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Grand Gateway - St. Cloud, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | GrandeVille at Cascade Lake - Rochester, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Greenfield - Omaha, NE        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Heritage Manor - Rochester, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Homestead Garden - Rapid City, SD        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Lakeside Village Lincoln, NE        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Legacy - Grand Forks, ND        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Legacy Heights - Bismarck, ND        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Meadows - Jamestown, ND        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Monticello Crossings - Monticello, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Monticello Village - Monticello, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Northridge - Bismarck, ND        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Olympic Village - Billings, MT        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Olympik Village - Rochester, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Park Meadows - Waite Park, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Plaza - Minot, ND        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Pointe West - Rapid City, SD        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Ponds at Heritage Place - Sartell, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Quarry Ridge - Rochester, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Red 20 - Minneapolis, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Regency Park Estates - St. Cloud, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Rimrock West - Billings, MT        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | River Ridge - Bismarck, ND        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Rocky Meadows - Billings, MT        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Rum River - Isanti, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Silver Springs - Rapid City, SD        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | South Pointe - Minot, ND        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Southpoint - Grand Forks, ND        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Sunset Trail - Rochester, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Thomasbrook - Lincoln, NE        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Village Green - Rochester, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | West Stonehill - Waite Park, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Whispering Ridge - Omaha, NE        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Winchester - Rochester, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Minimum | Woodridge - Rochester, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
MultiFamily Same-Store | Maximum | 71 France - Edina, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Alps Park - Rapid City, SD        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Ashland - Grand Forks, ND        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Avalon Cove - Rochester, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Boulder Court - Eagan, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Canyon Lake - Rapid City, SD        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Cardinal Point - Grand Forks, ND        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Cascade Shores - Rochester, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Castlerock - Billings, MT        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Chateau - Minot, ND        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Cimarron Hills - Omaha, NE        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Colonial Villa - Burnsville, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Colony - Lincoln, NE        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Commons at Southgate - Minot, ND        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Cottonwood - Bismarck, ND        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Country Meadows - Billings, MT        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Crystal Bay - Rochester, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Cypress Court - St. Cloud, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Deer Ridge - Jamestown, ND        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Evergreen - Isanti, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | French Creek - Rochester, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Gardens - Grand Forks, ND        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Grand Gateway - St. Cloud, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | GrandeVille at Cascade Lake - Rochester, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Greenfield - Omaha, NE        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Heritage Manor - Rochester, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Homestead Garden - Rapid City, SD        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Lakeside Village Lincoln, NE        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Legacy - Grand Forks, ND        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Legacy Heights - Bismarck, ND        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Meadows - Jamestown, ND        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Monticello Crossings - Monticello, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Monticello Village - Monticello, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Northridge - Bismarck, ND        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Olympic Village - Billings, MT        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Olympik Village - Rochester, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Park Meadows - Waite Park, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Plaza - Minot, ND        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Pointe West - Rapid City, SD        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Ponds at Heritage Place - Sartell, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Quarry Ridge - Rochester, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Red 20 - Minneapolis, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Regency Park Estates - St. Cloud, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Rimrock West - Billings, MT        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | River Ridge - Bismarck, ND        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Rocky Meadows - Billings, MT        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Rum River - Isanti, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Silver Springs - Rapid City, SD        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | South Pointe - Minot, ND        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Southpoint - Grand Forks, ND        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Sunset Trail - Rochester, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Thomasbrook - Lincoln, NE        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Village Green - Rochester, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | West Stonehill - Waite Park, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Whispering Ridge - Omaha, NE        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Winchester - Rochester, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Maximum | Woodridge - Rochester, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
MultiFamily Same-Store | Wholly Owned Properties        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Multifamily and Other $ 181,771 $ 168,504    
MultiFamily Non-Same-Store        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     21,675  
Initial Cost to Company [Abstract]        
Land     25,709  
Buildings & Improvements     320,514  
Costs capitalized subsequent to acquisition     8,946  
Gross amount at which carries at close of period [Abstract]        
Land     25,808  
Buildings & Improvements     329,361  
Total 355,169   355,169  
Accumulated Depreciation (12,048)   (12,048)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 355,169      
Deductions during year [Abstract]        
Balance at close of year 12,048      
MultiFamily Non-Same-Store | FreightYard Townhomes & Flats - Minneapolis, MN        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     1,889  
Buildings & Improvements     23,616  
Costs capitalized subsequent to acquisition     877  
Gross amount at which carries at close of period [Abstract]        
Land     1,895  
Buildings & Improvements     24,487  
Total 26,382   26,382  
Accumulated Depreciation $ (1,171)   (1,171)  
Life on which depreciation in latest income statement is computed 30 years      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year $ 26,382      
Deductions during year [Abstract]        
Balance at close of year 1,171      
MultiFamily Non-Same-Store | Ironwood - Minneapolis, MN        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     2,165  
Buildings & Improvements     36,874  
Costs capitalized subsequent to acquisition     84  
Gross amount at which carries at close of period [Abstract]        
Land     2,167  
Buildings & Improvements     36,956  
Total 39,123   39,123  
Accumulated Depreciation $ (1,187)   (1,187)  
Life on which depreciation in latest income statement is computed 30 years      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year $ 39,123      
Deductions during year [Abstract]        
Balance at close of year 1,187      
MultiFamily Non-Same-Store | Lugano at Cherry Creek - Denver, CO        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     7,679  
Buildings & Improvements     87,766  
Costs capitalized subsequent to acquisition     635  
Gross amount at which carries at close of period [Abstract]        
Land     7,679  
Buildings & Improvements     88,401  
Total 96,080   96,080  
Accumulated Depreciation $ (4,330)   (4,330)  
Life on which depreciation in latest income statement is computed 30 years      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year $ 96,080      
Deductions during year [Abstract]        
Balance at close of year 4,330      
MultiFamily Non-Same-Store | Parkhouse - Thornton, CO        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     10,474  
Buildings & Improvements     132,105  
Costs capitalized subsequent to acquisition     228  
Gross amount at which carries at close of period [Abstract]        
Land     10,484  
Buildings & Improvements     132,323  
Total 142,807   142,807  
Accumulated Depreciation $ (1,722)   (1,722)  
Life on which depreciation in latest income statement is computed 30 years      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year $ 142,807      
Deductions during year [Abstract]        
Balance at close of year 1,722      
MultiFamily Non-Same-Store | SouthFork Townhomes        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     21,675  
Initial Cost to Company [Abstract]        
Land     3,502  
Buildings & Improvements     40,153  
Costs capitalized subsequent to acquisition     7,122  
Gross amount at which carries at close of period [Abstract]        
Land     3,583  
Buildings & Improvements     47,194  
Total 50,777   50,777  
Accumulated Depreciation $ (3,638)   (3,638)  
Life on which depreciation in latest income statement is computed 30 years      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year $ 50,777      
Deductions during year [Abstract]        
Balance at close of year 3,638      
Total Multifamily        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     298,445  
Initial Cost to Company [Abstract]        
Land     145,289  
Buildings & Improvements     1,464,272  
Costs capitalized subsequent to acquisition     169,817  
Gross amount at which carries at close of period [Abstract]        
Land     163,058  
Buildings & Improvements     1,616,320  
Total 1,779,378   1,779,378  
Accumulated Depreciation (387,990)   (387,990)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 1,779,378      
Deductions during year [Abstract]        
Balance at close of year 387,990      
Other - Mixed Use        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     389  
Buildings & Improvements     18,920  
Costs capitalized subsequent to acquisition     5,391  
Gross amount at which carries at close of period [Abstract]        
Land     607  
Buildings & Improvements     24,093  
Total 24,700   24,700  
Accumulated Depreciation (6,647)   (6,647)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 24,700      
Deductions during year [Abstract]        
Balance at close of year 6,647      
Other - Mixed Use | 71 France - Edina, MN        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     0  
Buildings & Improvements     5,879  
Costs capitalized subsequent to acquisition     867  
Gross amount at which carries at close of period [Abstract]        
Land     0  
Buildings & Improvements     6,746  
Total 6,746   6,746  
Accumulated Depreciation (1,151)   (1,151)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 6,746      
Deductions during year [Abstract]        
Balance at close of year 1,151      
Other - Mixed Use | Oxbo - St Paul, MN        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     0  
Buildings & Improvements     3,472  
Costs capitalized subsequent to acquisition     54  
Gross amount at which carries at close of period [Abstract]        
Land     0  
Buildings & Improvements     3,526  
Total 3,526   3,526  
Accumulated Depreciation $ (436)   (436)  
Life on which depreciation in latest income statement is computed 30 years      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year $ 3,526      
Deductions during year [Abstract]        
Balance at close of year 436      
Other - Mixed Use | Plaza - Minot, ND        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     389  
Buildings & Improvements     5,444  
Costs capitalized subsequent to acquisition     3,845  
Gross amount at which carries at close of period [Abstract]        
Land     607  
Buildings & Improvements     9,071  
Total 9,678   9,678  
Accumulated Depreciation (4,305)   (4,305)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 9,678      
Deductions during year [Abstract]        
Balance at close of year 4,305      
Other - Mixed Use | Red 20 - Minneapolis, MN        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     0  
Buildings & Improvements     2,525  
Costs capitalized subsequent to acquisition     419  
Gross amount at which carries at close of period [Abstract]        
Land     0  
Buildings & Improvements     2,944  
Total 2,944   2,944  
Accumulated Depreciation (683)   (683)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 2,944      
Deductions during year [Abstract]        
Balance at close of year 683      
Other - Mixed Use | Lugano at Cherry Creek - Denver, CO        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     0  
Buildings & Improvements     1,600  
Costs capitalized subsequent to acquisition     206  
Gross amount at which carries at close of period [Abstract]        
Land     0  
Buildings & Improvements     1,806  
Total 1,806   1,806  
Accumulated Depreciation $ (72)   (72)  
Life on which depreciation in latest income statement is computed 30 years      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year $ 1,806      
Deductions during year [Abstract]        
Balance at close of year $ 72      
Other - Mixed Use | Minimum | 71 France - Edina, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
Other - Mixed Use | Minimum | Plaza - Minot, ND        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
Other - Mixed Use | Minimum | Red 20 - Minneapolis, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
Other - Mixed Use | Maximum | 71 France - Edina, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
Other - Mixed Use | Maximum | Plaza - Minot, ND        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
Other - Mixed Use | Maximum | Red 20 - Minneapolis, MN        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
Other - Commercial        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     662  
Buildings & Improvements     7,818  
Costs capitalized subsequent to acquisition     (1)  
Gross amount at which carries at close of period [Abstract]        
Land     662  
Buildings & Improvements     7,817  
Total $ 8,479   8,479  
Accumulated Depreciation (4,612)   (4,612)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 8,479      
Deductions during year [Abstract]        
Balance at close of year 4,612      
Other - Commercial | 3100 10th St SW - Minot, ND        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     246  
Buildings & Improvements     1,866  
Costs capitalized subsequent to acquisition     (1)  
Gross amount at which carries at close of period [Abstract]        
Land     246  
Buildings & Improvements     1,865  
Total 2,111   2,111  
Accumulated Depreciation (103)   (103)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 2,111      
Deductions during year [Abstract]        
Balance at close of year 103      
Other - Commercial | Minot IPS - Minot, ND        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     0  
Initial Cost to Company [Abstract]        
Land     416  
Buildings & Improvements     5,952  
Costs capitalized subsequent to acquisition     0  
Gross amount at which carries at close of period [Abstract]        
Land     416  
Buildings & Improvements     5,952  
Total 6,368   6,368  
Accumulated Depreciation (4,509)   (4,509)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 6,368      
Deductions during year [Abstract]        
Balance at close of year $ 4,509      
Other - Commercial | Minimum | Minot IPS - Minot, ND        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
Other - Commercial | Maximum | 3100 10th St SW - Minot, ND        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 30 years      
Other - Commercial | Maximum | Minot IPS - Minot, ND        
Gross amount at which carries at close of period [Abstract]        
Life on which depreciation in latest income statement is computed 37 years      
Total        
Real Estate And Accumulated Depreciation [Abstract]        
Encumbrances     298,445  
Initial Cost to Company [Abstract]        
Land     146,340  
Buildings & Improvements     1,491,010  
Costs capitalized subsequent to acquisition     175,207  
Gross amount at which carries at close of period [Abstract]        
Land     164,327  
Buildings & Improvements     1,648,230  
Total $ 1,812,557   1,812,557  
Accumulated Depreciation (399,249)   $ (399,249)  
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]        
Balance at close of year 1,812,557      
Deductions during year [Abstract]        
Balance at close of year $ 399,249