SCHEDULE III - REAL ESTATE AND ACCUMULATED DEPRECIATION (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2017	Apr. 30, 2016	Apr. 30, 2015	Apr. 30, 2017	Apr. 30, 2016	Apr. 30, 2015
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				$ 665,338
Initial Cost to Company [Abstract]
Land				131,815
Buildings & Improvements				1,307,790
Costs capitalized subsequent to acquisition				256,331
Gross amount at which carried at close of period [Abstract]
Land				154,820
Buildings & Improvements				1,541,116
Total	$ 1,695,936			1,695,936
Accumulated Depreciation	(312,889)	$ (279,417)	$ (273,934)	(340,417)	$ (312,889)	$ (279,417)
Reconciliations of total real estate carrying value [Abstract]
Write down of asset and accumulated depreciation on impaired assets	(7,144)		(881)
Balance at close of year	1,695,936
Reconciliations of accumulated depreciation/amortization [Abstract]
Balance at beginning of year	312,889	279,417	273,934
Additions during year [Abstract]
Provisions for depreciation	52,786	47,064	40,078
Deductions during year [Abstract]
Accumulated depreciation on real estate sold	(14,687)	(9,957)	(29,463)
Write down of asset and accumulated depreciation on impaired assets	(7,144)		(881)
Other	(3,427)	(3,635)	(4,251)
Balance at close of year	340,417	312,889	279,417
Total real estate investments				1,355,519	1,441,202
Net basis of real estate investments for federal income tax purposes				1,400	1,600	1,700
Discontinued Operations [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				21,802
Initial Cost to Company [Abstract]
Land				2,959
Buildings & Improvements				34,572
Costs capitalized subsequent to acquisition				14,528
Gross amount at which carried at close of period [Abstract]
Land				3,915
Buildings & Improvements				48,144
Total	52,059			52,059
Accumulated Depreciation	(16,744)			(16,744)
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	52,059
Deductions during year [Abstract]
Balance at close of year	16,744
Discontinued Operations [Member] | 1st Avenue Building - Minot, ND [Member]
Initial Cost to Company [Abstract]
Land				30
Buildings & Improvements				337
Gross amount at which carried at close of period [Abstract]
Land				30
Buildings & Improvements				337
Total	367			367
Accumulated Depreciation	$ (54)			(54)
Date of Construction or Acquisition	1981
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 367
Deductions during year [Abstract]
Balance at close of year	$ 54
Discontinued Operations [Member] | 1st Avenue Building - Minot, ND [Member] | Minimum [Member]
Gross amount at which carried at close of period [Abstract]
Life on which depreciation in latest income statement is computed	33 years
Discontinued Operations [Member] | 1st Avenue Building - Minot, ND [Member] | Maximum [Member]
Gross amount at which carried at close of period [Abstract]
Life on which depreciation in latest income statement is computed	40 years
Discontinued Operations [Member] | 4th Street 4 Plex - Minot, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				90
Initial Cost to Company [Abstract]
Land				15
Buildings & Improvements				74
Costs capitalized subsequent to acquisition				41
Gross amount at which carried at close of period [Abstract]
Land				26
Buildings & Improvements				104
Total	$ 130			130
Accumulated Depreciation	$ (26)			(26)
Date of Construction or Acquisition	2008
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 130
Deductions during year [Abstract]
Balance at close of year	26
Discontinued Operations [Member] | 11th Street 3 Plex - Minot, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				77
Initial Cost to Company [Abstract]
Land				11
Buildings & Improvements				53
Costs capitalized subsequent to acquisition				26
Gross amount at which carried at close of period [Abstract]
Land				20
Buildings & Improvements				70
Total	90			90
Accumulated Depreciation	$ (16)			(16)
Date of Construction or Acquisition	2008
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 90
Deductions during year [Abstract]
Balance at close of year	16
Discontinued Operations [Member] | 17 South Main - Minot, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				69
Initial Cost to Company [Abstract]
Land				15
Buildings & Improvements				75
Costs capitalized subsequent to acquisition				197
Gross amount at which carried at close of period [Abstract]
Land				17
Buildings & Improvements				270
Total	287			287
Accumulated Depreciation	$ (206)			(206)
Date of Construction or Acquisition	2000
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 287
Deductions during year [Abstract]
Balance at close of year	206
Discontinued Operations [Member] | Apartments on Main - Minot, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				590
Initial Cost to Company [Abstract]
Land				158
Buildings & Improvements				1,123
Costs capitalized subsequent to acquisition				71
Gross amount at which carried at close of period [Abstract]
Land				195
Buildings & Improvements				1,157
Total	1,352			1,352
Accumulated Depreciation	$ (292)			(292)
Date of Construction or Acquisition	1987
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 1,352
Deductions during year [Abstract]
Balance at close of year	$ 292
Discontinued Operations [Member] | Apartments on Main - Minot, ND [Member] | Minimum [Member]
Gross amount at which carried at close of period [Abstract]
Life on which depreciation in latest income statement is computed	24 years
Discontinued Operations [Member] | Apartments on Main - Minot, ND [Member] | Maximum [Member]
Gross amount at which carried at close of period [Abstract]
Life on which depreciation in latest income statement is computed	40 years
Discontinued Operations [Member] | Brooklyn Heights - Minot, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				573
Initial Cost to Company [Abstract]
Land				145
Buildings & Improvements				1,450
Costs capitalized subsequent to acquisition				1,051
Gross amount at which carried at close of period [Abstract]
Land				235
Buildings & Improvements				2,411
Total	$ 2,646			2,646
Accumulated Depreciation	$ (1,035)			(1,035)
Date of Construction or Acquisition	1997
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 2,646
Deductions during year [Abstract]
Balance at close of year	$ 1,035
Discontinued Operations [Member] | Brooklyn Heights - Minot, ND [Member] | Minimum [Member]
Gross amount at which carried at close of period [Abstract]
Life on which depreciation in latest income statement is computed	12 years
Discontinued Operations [Member] | Brooklyn Heights - Minot, ND [Member] | Maximum [Member]
Gross amount at which carried at close of period [Abstract]
Life on which depreciation in latest income statement is computed	40 years
Discontinued Operations [Member] | Colton Heights - Minot, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				323
Initial Cost to Company [Abstract]
Land				80
Buildings & Improvements				672
Costs capitalized subsequent to acquisition				470
Gross amount at which carried at close of period [Abstract]
Land				123
Buildings & Improvements				1,099
Total	$ 1,222			1,222
Accumulated Depreciation	$ (825)			(825)
Date of Construction or Acquisition	1984
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 1,222
Deductions during year [Abstract]
Balance at close of year	825
Discontinued Operations [Member] | Edgewood Vista - Hermantown I, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				16,233
Initial Cost to Company [Abstract]
Land				288
Buildings & Improvements				9,871
Costs capitalized subsequent to acquisition				10,094
Gross amount at which carried at close of period [Abstract]
Land				288
Buildings & Improvements				19,965
Total	20,253			20,253
Accumulated Depreciation	$ (7,931)			(7,931)
Date of Construction or Acquisition	2000
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 20,253
Deductions during year [Abstract]
Balance at close of year	7,931
Discontinued Operations [Member] | Edgewood Vista - Hermantown II, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				0
Initial Cost to Company [Abstract]
Land				719
Buildings & Improvements				10,517
Costs capitalized subsequent to acquisition				942
Gross amount at which carried at close of period [Abstract]
Land				719
Buildings & Improvements				11,459
Total	12,178			12,178
Accumulated Depreciation	$ (3,168)			(3,168)
Date of Construction or Acquisition	2005
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 12,178
Deductions during year [Abstract]
Balance at close of year	3,168
Discontinued Operations [Member] | Fairmont - Minot, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				305
Initial Cost to Company [Abstract]
Land				28
Buildings & Improvements				337
Costs capitalized subsequent to acquisition				132
Gross amount at which carried at close of period [Abstract]
Land				56
Buildings & Improvements				441
Total	497			497
Accumulated Depreciation	$ (101)			(101)
Date of Construction or Acquisition	2008
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 497
Deductions during year [Abstract]
Balance at close of year	101
Discontinued Operations [Member] | First Avenue - Minot ND [Member]
Initial Cost to Company [Abstract]
Buildings & Improvements				3,045
Costs capitalized subsequent to acquisition				24
Gross amount at which carried at close of period [Abstract]
Buildings & Improvements				3,069
Total	3,069			3,069
Accumulated Depreciation	$ (273)			(273)
Date of Construction or Acquisition	2013
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 3,069
Deductions during year [Abstract]
Balance at close of year	273
Discontinued Operations [Member] | Minot Southgate Wells Fargo Bank - Minot, ND [Member]
Initial Cost to Company [Abstract]
Land				992
Buildings & Improvements				2,237
Gross amount at which carried at close of period [Abstract]
Land				992
Buildings & Improvements				2,237
Total	3,229			3,229
Accumulated Depreciation	$ (139)			(139)
Date of Construction or Acquisition	2014
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 3,229
Deductions during year [Abstract]
Balance at close of year	139
Discontinued Operations [Member] | Pines - Minot, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				92
Initial Cost to Company [Abstract]
Land				35
Buildings & Improvements				215
Costs capitalized subsequent to acquisition				270
Gross amount at which carried at close of period [Abstract]
Land				49
Buildings & Improvements				471
Total	520			520
Accumulated Depreciation	$ (151)			(151)
Date of Construction or Acquisition	1997
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 520
Deductions during year [Abstract]
Balance at close of year	151
Discontinued Operations [Member] | Southview - Minot, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				978
Initial Cost to Company [Abstract]
Land				185
Buildings & Improvements				469
Costs capitalized subsequent to acquisition				525
Gross amount at which carried at close of period [Abstract]
Land				251
Buildings & Improvements				928
Total	1,179			1,179
Accumulated Depreciation	$ (407)			(407)
Date of Construction or Acquisition	1994
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 1,179
Deductions during year [Abstract]
Balance at close of year	407
Discontinued Operations [Member] | Summit Park - Minot, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				795
Initial Cost to Company [Abstract]
Land				161
Buildings & Improvements				1,898
Costs capitalized subsequent to acquisition				(126)
Gross amount at which carried at close of period [Abstract]
Land				795
Buildings & Improvements				1,138
Total	1,933			1,933
Accumulated Depreciation	$ (1,382)			(1,382)
Date of Construction or Acquisition	1997
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 1,933
Deductions during year [Abstract]
Balance at close of year	$ 1,382
Discontinued Operations [Member] | Summit Park - Minot, ND [Member] | Minimum [Member]
Gross amount at which carried at close of period [Abstract]
Life on which depreciation in latest income statement is computed	24 years
Discontinued Operations [Member] | Summit Park - Minot, ND [Member] | Maximum [Member]
Gross amount at which carried at close of period [Abstract]
Life on which depreciation in latest income statement is computed	40 years
Discontinued Operations [Member] | Temple - Minot, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				69
Initial Cost to Company [Abstract]
Costs capitalized subsequent to acquisition				226
Gross amount at which carried at close of period [Abstract]
Buildings & Improvements				226
Total	$ 226			226
Accumulated Depreciation	$ (57)			(57)
Date of Construction or Acquisition	2006
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 226
Deductions during year [Abstract]
Balance at close of year	57
Discontinued Operations [Member] | Terrace Heights - Minot, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				133
Initial Cost to Company [Abstract]
Land				29
Buildings & Improvements				312
Costs capitalized subsequent to acquisition				206
Gross amount at which carried at close of period [Abstract]
Land				40
Buildings & Improvements				507
Total	547			547
Accumulated Depreciation	$ (187)			(187)
Date of Construction or Acquisition	2006
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 547
Deductions during year [Abstract]
Balance at close of year	187
Discontinued Operations [Member] | Westridge - Minot, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				1,475
Initial Cost to Company [Abstract]
Land				68
Buildings & Improvements				1,887
Costs capitalized subsequent to acquisition				379
Gross amount at which carried at close of period [Abstract]
Land				79
Buildings & Improvements				2,255
Total	2,334			2,334
Accumulated Depreciation	$ (494)			(494)
Date of Construction or Acquisition	2008
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 2,334
Deductions during year [Abstract]
Balance at close of year	494
Wholly Owned Properties [Member]
Gross amount at which carried at close of period [Abstract]
Total	1,681,471	1,335,687	1,241,195	1,677,481	1,681,471	1,335,687
Reconciliations of total real estate carrying value [Abstract]
Balance at beginning of year	1,681,471	1,335,687	1,241,195
Transfers	(24,156)	(32,438)	(97,824)
Improvements and Other	42,291	34,619	21,006
Total Additions	1,785,327	1,718,991	1,457,538
Cost of real estate sold	(21,718)	(1,305)	(17,904)
Impairment charge	(51,401)		(1,566)
Write down of asset and accumulated depreciation on impaired assets	(7,144)		(881)
Other	(3,427)	(3,777)	(3,676)
Balance at close of year	1,677,481	1,681,471	1,335,687
Deductions during year [Abstract]
Write down of asset and accumulated depreciation on impaired assets	(7,144)		(881)
Development in Progress [Member]
Gross amount at which carried at close of period [Abstract]
Total	51,681	153,994	104,609		51,681	153,994
Reconciliations of total real estate carrying value [Abstract]
Balance at beginning of year	51,681	153,994	104,609
Acquisitions			12,647
Transfers		1,734	7,015
Improvements and Other	7,893	96,753	189,306
Development placed in service	(59,574)	(200,800)	(159,578)
Other			(5)
Balance at close of year		51,681	153,994
Unimproved Land [Member]
Initial Cost to Company [Abstract]
Land				16,671
Costs capitalized subsequent to acquisition				1,784
Gross amount at which carried at close of period [Abstract]
Land				18,455
Total	20,939	25,827	22,864	18,455	20,939	25,827
Reconciliations of total real estate carrying value [Abstract]
Balance at beginning of year	20,939	25,827	22,864
Acquisitions			10,487
Transfers		(1,632)	(79)
Improvements and Other	1,024	205	1,533
Cost of real estate sold		(442)	(670)
Impairment charge	(3,508)	(1,285)	(1,293)
Development placed in service		(1,734)	(7,015)
Balance at close of year	18,455	20,939	25,827
Deductions during year [Abstract]
Total real estate investments				1,355,519	$ 1,441,202	$ 1,236,091
Unimproved Land [Member] | Renaissance Heights - Williston, ND [Member]
Initial Cost to Company [Abstract]
Land				1,178
Gross amount at which carried at close of period [Abstract]
Land				1,178
Total	$ 1,178			1,178
Date of Construction or Acquisition	2012
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 1,178
Unimproved Land [Member] | Badger Hills - Rochester, MN [Member]
Initial Cost to Company [Abstract]
Land				1,050
Costs capitalized subsequent to acquisition				339
Gross amount at which carried at close of period [Abstract]
Land				1,389
Total	$ 1,389			1,389
Date of Construction or Acquisition	2012
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 1,389
Unimproved Land [Member] | Bismarck 4916 - Bismarck, ND [Member]
Initial Cost to Company [Abstract]
Land				3,250
Costs capitalized subsequent to acquisition				45
Gross amount at which carried at close of period [Abstract]
Land				3,295
Total	$ 3,295			3,295
Date of Construction or Acquisition	2013
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 3,295
Unimproved Land [Member] | Bismarck 700 E Main - Bismarck, ND [Member]
Initial Cost to Company [Abstract]
Land				314
Costs capitalized subsequent to acquisition				571
Gross amount at which carried at close of period [Abstract]
Land				885
Total	$ 885			885
Date of Construction or Acquisition	2008
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 885
Unimproved Land [Member] | Creekside Crossing - Bismarck, ND [Member]
Initial Cost to Company [Abstract]
Land				4,286
Costs capitalized subsequent to acquisition				719
Gross amount at which carried at close of period [Abstract]
Land				5,005
Total	$ 5,005			5,005
Date of Construction or Acquisition	2015
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 5,005
Unimproved Land [Member] | Grand Forks Grand Forks, ND [Member]
Initial Cost to Company [Abstract]
Land				4,278
Costs capitalized subsequent to acquisition				2
Gross amount at which carried at close of period [Abstract]
Land				4,280
Total	$ 4,280			4,280
Date of Construction or Acquisition	2012
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 4,280
Unimproved Land [Member] | Isanti Unimproved - Isanti, MN [Member]
Initial Cost to Company [Abstract]
Land				58
Gross amount at which carried at close of period [Abstract]
Land				58
Total	$ 58			58
Date of Construction or Acquisition	2014
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 58
Unimproved Land [Member] | Minot 1525 24th Ave SW - Minot, ND [Member]
Initial Cost to Company [Abstract]
Land				506
Gross amount at which carried at close of period [Abstract]
Land				506
Total	$ 506			506
Date of Construction or Acquisition	2015
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 506
Unimproved Land [Member] | Rapid City Unimproved- Rapid City, SD [Member]
Initial Cost to Company [Abstract]
Land				1,376
Gross amount at which carried at close of period [Abstract]
Land				1,376
Total	$ 1,376			1,376
Date of Construction or Acquisition	2014
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 1,376
Unimproved Land [Member] | Urbandale - Urbandale, IA [Member]
Initial Cost to Company [Abstract]
Land				5
Costs capitalized subsequent to acquisition				108
Gross amount at which carried at close of period [Abstract]
Land				113
Total	$ 113			113
Date of Construction or Acquisition	2009
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 113
Unimproved Land [Member] | Weston - Weston, WI [Member]
Initial Cost to Company [Abstract]
Land				370
Gross amount at which carried at close of period [Abstract]
Land				370
Total	$ 370			370
Date of Construction or Acquisition	2006
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 370
Multi-Family Residential [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				548,401
Initial Cost to Company [Abstract]
Land				82,121
Buildings & Improvements				1,004,096
Costs capitalized subsequent to acquisition				174,324
Gross amount at which carried at close of period [Abstract]
Land				101,227
Buildings & Improvements				1,159,314
Total	1,260,541			1,260,541
Accumulated Depreciation	(232,592)			(232,592)
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	1,260,541
Deductions during year [Abstract]
Balance at close of year	232,592
Multi-Family Residential [Member] | 71 France - Edina, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				56,000
Initial Cost to Company [Abstract]
Land				4,721
Buildings & Improvements				67,641
Costs capitalized subsequent to acquisition				119
Gross amount at which carried at close of period [Abstract]
Land				4,721
Buildings & Improvements				67,760
Total	72,481			72,481
Accumulated Depreciation	$ (2,685)			(2,685)
Date of Construction or Acquisition	2016
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 72,481
Deductions during year [Abstract]
Balance at close of year	2,685
Multi-Family Residential [Member] | Alps Park - Rapid City, SD [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				3,728
Initial Cost to Company [Abstract]
Land				287
Buildings & Improvements				5,551
Costs capitalized subsequent to acquisition				313
Gross amount at which carried at close of period [Abstract]
Land				333
Buildings & Improvements				5,818
Total	6,151			6,151
Accumulated Depreciation	$ (640)			(640)
Date of Construction or Acquisition	2013
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 6,151
Deductions during year [Abstract]
Balance at close of year	640
Multi-Family Residential [Member] | Arbors - S Sioux City, NE [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				3,660
Initial Cost to Company [Abstract]
Land				350
Buildings & Improvements				6,625
Costs capitalized subsequent to acquisition				2,198
Gross amount at which carried at close of period [Abstract]
Land				1,021
Buildings & Improvements				8,152
Total	9,173			9,173
Accumulated Depreciation	$ (2,501)			(2,501)
Date of Construction or Acquisition	2006
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 9,173
Deductions during year [Abstract]
Balance at close of year	2,501
Multi-Family Residential [Member] | Arcata - Golden Valley, MN [Member]
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				94
Gross amount at which carried at close of period [Abstract]
Land				2,089
Buildings & Improvements				31,129
Total	33,218			33,218
Accumulated Depreciation	$ (2,524)			(2,524)
Date of Construction or Acquisition	2015
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 33,218
Deductions during year [Abstract]
Balance at close of year	2,524
Multi-Family Residential [Member] | Ashland - Grand Forks, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				5,306
Initial Cost to Company [Abstract]
Land				741
Buildings & Improvements				7,569
Costs capitalized subsequent to acquisition				244
Gross amount at which carried at close of period [Abstract]
Land				791
Buildings & Improvements				7,763
Total	8,554			8,554
Accumulated Depreciation	$ (1,130)			(1,130)
Date of Construction or Acquisition	2012
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 8,554
Deductions during year [Abstract]
Balance at close of year	1,130
Multi-Family Residential [Member] | 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				178
Gross amount at which carried at close of period [Abstract]
Land				1,618
Buildings & Improvements				34,250
Total	35,868			35,868
Accumulated Depreciation	$ (1,057)			(1,057)
Date of Construction or Acquisition	2016
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 35,868
Deductions during year [Abstract]
Balance at close of year	1,057
Multi-Family Residential [Member] | Boulder Court - Eagan, MN [Member]
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				3,005
Gross amount at which carried at close of period [Abstract]
Land				1,393
Buildings & Improvements				8,177
Total	9,570			9,570
Accumulated Depreciation	$ (2,882)			(2,882)
Date of Construction or Acquisition	2003
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 9,570
Deductions during year [Abstract]
Balance at close of year	2,882
Multi-Family Residential [Member] | Brookfield Village - Topeka, KS [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				5,025
Initial Cost to Company [Abstract]
Land				509
Buildings & Improvements				6,698
Costs capitalized subsequent to acquisition				1,773
Gross amount at which carried at close of period [Abstract]
Land				828
Buildings & Improvements				8,152
Total	8,980			8,980
Accumulated Depreciation	$ (2,743)			(2,743)
Date of Construction or Acquisition	2003
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 8,980
Deductions during year [Abstract]
Balance at close of year	2,743
Multi-Family Residential [Member] | Canyon Lake - Rapid City, SD [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				2,735
Initial Cost to Company [Abstract]
Land				305
Buildings & Improvements				3,958
Costs capitalized subsequent to acquisition				1,929
Gross amount at which carried at close of period [Abstract]
Land				397
Buildings & Improvements				5,795
Total	6,192			6,192
Accumulated Depreciation	$ (2,159)			(2,159)
Date of Construction or Acquisition	2001
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 6,192
Deductions during year [Abstract]
Balance at close of year	2,159
Multi-Family Residential [Member] | Cardinal Point - Grand Forks, ND
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				0
Initial Cost to Company [Abstract]
Land				1,600
Buildings & Improvements				49,606
Costs capitalized subsequent to acquisition				995
Gross amount at which carried at close of period [Abstract]
Land				1,604
Buildings & Improvements				50,597
Total	52,201			52,201
Accumulated Depreciation	$ (2,235)			(2,235)
Date of Construction or Acquisition	2013
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 52,201
Deductions during year [Abstract]
Balance at close of year	2,235
Multi-Family Residential [Member] | 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				47
Gross amount at which carried at close of period [Abstract]
Land				1,586
Buildings & Improvements				16,756
Total	18,342			18,342
Accumulated Depreciation	$ (540)			(540)
Date of Construction or Acquisition	2016
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 18,342
Deductions during year [Abstract]
Balance at close of year	540
Multi-Family Residential [Member] | Castlerock - Billings, MT [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				6,347
Initial Cost to Company [Abstract]
Land				736
Buildings & Improvements				4,864
Costs capitalized subsequent to acquisition				2,370
Gross amount at which carried at close of period [Abstract]
Land				1,022
Buildings & Improvements				6,948
Total	7,970			7,970
Accumulated Depreciation	$ (3,199)			(3,199)
Date of Construction or Acquisition	1998
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 7,970
Deductions during year [Abstract]
Balance at close of year	3,199
Multi-Family Residential [Member] | Chateau I & II - 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				833
Gross amount at which carried at close of period [Abstract]
Land				317
Buildings & Improvements				20,875
Total	21,192			21,192
Accumulated Depreciation	$ (2,081)			(2,081)
Date of Construction or Acquisition	2013
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 21,192
Deductions during year [Abstract]
Balance at close of year	2,081
Multi-Family Residential [Member] | Cimarron Hills - Omaha, NE [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				4,562
Initial Cost to Company [Abstract]
Land				706
Buildings & Improvements				9,588
Costs capitalized subsequent to acquisition				4,588
Gross amount at which carried at close of period [Abstract]
Land				1,417
Buildings & Improvements				13,465
Total	14,882			14,882
Accumulated Depreciation	$ (5,492)			(5,492)
Date of Construction or Acquisition	2001
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 14,882
Deductions during year [Abstract]
Balance at close of year	5,492
Multi-Family Residential [Member] | Colonial Villa - Burnsville, MN [Member]
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				9,039
Gross amount at which carried at close of period [Abstract]
Land				2,880
Buildings & Improvements				20,075
Total	22,955			22,955
Accumulated Depreciation	$ (6,746)			(6,746)
Date of Construction or Acquisition	2003
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 22,955
Deductions during year [Abstract]
Balance at close of year	6,746
Multi-Family Residential [Member] | Colony - Lincoln, NE [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				12,748
Initial Cost to Company [Abstract]
Land				1,515
Buildings & Improvements				15,730
Costs capitalized subsequent to acquisition				1,220
Gross amount at which carried at close of period [Abstract]
Land				1,652
Buildings & Improvements				16,813
Total	18,465			18,465
Accumulated Depreciation	$ (2,361)			(2,361)
Date of Construction or Acquisition	2012
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 18,465
Deductions during year [Abstract]
Balance at close of year	2,361
Multi-Family Residential [Member] | Commons at Southgate - Minot, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				26,751
Initial Cost to Company [Abstract]
Land				5,945
Buildings & Improvements				47,512
Costs capitalized subsequent to acquisition				825
Gross amount at which carried at close of period [Abstract]
Land				6,194
Buildings & Improvements				48,088
Total	54,282			54,282
Accumulated Depreciation	$ (4,490)			(4,490)
Date of Construction or Acquisition	2015
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 54,282
Deductions during year [Abstract]
Balance at close of year	4,490
Multi-Family Residential [Member] | Cottage West Twin Homes - Sioux Falls, SD [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				3,457
Initial Cost to Company [Abstract]
Land				968
Buildings & Improvements				3,762
Costs capitalized subsequent to acquisition				555
Gross amount at which carried at close of period [Abstract]
Land				1,056
Buildings & Improvements				4,229
Total	5,285			5,285
Accumulated Depreciation	$ (619)			(619)
Date of Construction or Acquisition	2011
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 5,285
Deductions during year [Abstract]
Balance at close of year	619
Multi-Family Residential [Member] | Cottonwood - Bismarck, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				15,111
Initial Cost to Company [Abstract]
Land				1,056
Buildings & Improvements				17,372
Costs capitalized subsequent to acquisition				5,231
Gross amount at which carried at close of period [Abstract]
Land				1,504
Buildings & Improvements				22,155
Total	23,659			23,659
Accumulated Depreciation	$ (8,130)			(8,130)
Date of Construction or Acquisition	1997
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 23,659
Deductions during year [Abstract]
Balance at close of year	8,130
Multi-Family Residential [Member] | Country Meadows - Billings, MT [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				6,303
Initial Cost to Company [Abstract]
Land				491
Buildings & Improvements				7,809
Costs capitalized subsequent to acquisition				1,726
Gross amount at which carried at close of period [Abstract]
Land				567
Buildings & Improvements				9,459
Total	10,026			10,026
Accumulated Depreciation	$ (4,378)			(4,378)
Date of Construction or Acquisition	1995
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 10,026
Deductions during year [Abstract]
Balance at close of year	$ 4,378
Multi-Family Residential [Member] | Country Meadows - Billings, MT [Member] | Minimum [Member]
Gross amount at which carried at close of period [Abstract]
Life on which depreciation in latest income statement is computed	33 years
Multi-Family Residential [Member] | Country Meadows - Billings, MT [Member] | Maximum [Member]
Gross amount at which carried at close of period [Abstract]
Life on which depreciation in latest income statement is computed	40 years
Multi-Family Residential [Member] | Crestview - Bismarck, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				3,670
Initial Cost to Company [Abstract]
Land				235
Buildings & Improvements				4,290
Costs capitalized subsequent to acquisition				2,069
Gross amount at which carried at close of period [Abstract]
Land				557
Buildings & Improvements				6,037
Total	$ 6,594			6,594
Accumulated Depreciation	$ (3,266)			(3,266)
Date of Construction or Acquisition	1994
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 6,594
Deductions during year [Abstract]
Balance at close of year	$ 3,266
Multi-Family Residential [Member] | Crestview - Bismarck, ND [Member] | Minimum [Member]
Gross amount at which carried at close of period [Abstract]
Life on which depreciation in latest income statement is computed	24 years
Multi-Family Residential [Member] | Crestview - Bismarck, ND [Member] | Maximum [Member]
Gross amount at which carried at close of period [Abstract]
Life on which depreciation in latest income statement is computed	40 years
Multi-Family Residential [Member] | Crown - Rochester, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				2,443
Initial Cost to Company [Abstract]
Land				261
Buildings & Improvements				3,289
Costs capitalized subsequent to acquisition				577
Gross amount at which carried at close of period [Abstract]
Land				269
Buildings & Improvements				3,858
Total	$ 4,127			4,127
Accumulated Depreciation	$ (699)			(699)
Date of Construction or Acquisition	2010
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 4,127
Deductions during year [Abstract]
Balance at close of year	699
Multi-Family Residential [Member] | Crown Colony - Topeka, KS [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				7,780
Initial Cost to Company [Abstract]
Land				620
Buildings & Improvements				9,956
Costs capitalized subsequent to acquisition				3,574
Gross amount at which carried at close of period [Abstract]
Land				1,042
Buildings & Improvements				13,108
Total	14,150			14,150
Accumulated Depreciation	$ (5,248)			(5,248)
Date of Construction or Acquisition	1999
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 14,150
Deductions during year [Abstract]
Balance at close of year	5,248
Multi-Family Residential [Member] | 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				68
Gross amount at which carried at close of period [Abstract]
Land				436
Buildings & Improvements				11,490
Total	11,926			11,926
Accumulated Depreciation	$ (347)			(347)
Date of Construction or Acquisition	2016
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 11,926
Deductions during year [Abstract]
Balance at close of year	347
Multi-Family Residential [Member] | Cypress Court - St. Cloud, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				12,666
Initial Cost to Company [Abstract]
Land				1,583
Buildings & Improvements				18,879
Costs capitalized subsequent to acquisition				194
Gross amount at which carried at close of period [Abstract]
Land				1,599
Buildings & Improvements				19,057
Total	20,656			20,656
Accumulated Depreciation	$ (1,909)			(1,909)
Date of Construction or Acquisition	2012
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 20,656
Deductions during year [Abstract]
Balance at close of year	1,909
Multi-Family Residential [Member] | Dakota Commons - Williston, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				0
Initial Cost to Company [Abstract]
Land				823
Buildings & Improvements				3,210
Costs capitalized subsequent to acquisition				17
Gross amount at which carried at close of period [Abstract]
Land				823
Buildings & Improvements				3,227
Total	4,050			4,050
Accumulated Depreciation	$ (58)			(58)
Date of Construction or Acquisition	2015
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 4,050
Deductions during year [Abstract]
Balance at close of year	58
Multi-Family Residential [Member] | Deer Ridge - Jamestown, ND
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				11,490
Initial Cost to Company [Abstract]
Land				711
Buildings & Improvements				24,129
Costs capitalized subsequent to acquisition				123
Gross amount at which carried at close of period [Abstract]
Land				723
Buildings & Improvements				24,240
Total	24,963			24,963
Accumulated Depreciation	$ (1,312)			(1,312)
Date of Construction or Acquisition	2013
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 24,963
Deductions during year [Abstract]
Balance at close of year	1,312
Multi-Family Residential [Member] | Evergreen - Isanti, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				3,885
Initial Cost to Company [Abstract]
Land				1,071
Buildings & Improvements				5,524
Costs capitalized subsequent to acquisition				339
Gross amount at which carried at close of period [Abstract]
Land				1,083
Buildings & Improvements				5,851
Total	6,934			6,934
Accumulated Depreciation	$ (1,084)			(1,084)
Date of Construction or Acquisition	2008
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 6,934
Deductions during year [Abstract]
Balance at close of year	1,084
Multi-Family Residential [Member] | Forest Park - Grand Forks, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				7,275
Initial Cost to Company [Abstract]
Land				810
Buildings & Improvements				5,579
Costs capitalized subsequent to acquisition				8,068
Gross amount at which carried at close of period [Abstract]
Land				1,450
Buildings & Improvements				13,007
Total	14,457			14,457
Accumulated Depreciation	$ (6,232)			(6,232)
Date of Construction or Acquisition	1993
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 14,457
Deductions during year [Abstract]
Balance at close of year	$ 6,232
Multi-Family Residential [Member] | Forest Park - Grand Forks, ND [Member] | Minimum [Member]
Gross amount at which carried at close of period [Abstract]
Life on which depreciation in latest income statement is computed	24 years
Multi-Family Residential [Member] | Forest Park - Grand Forks, ND [Member] | Maximum [Member]
Gross amount at which carried at close of period [Abstract]
Life on which depreciation in latest income statement is computed	40 years
Multi-Family Residential [Member] | 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				19
Gross amount at which carried at close of period [Abstract]
Land				207
Buildings & Improvements				4,748
Total	$ 4,955			4,955
Accumulated Depreciation	$ (139)			(139)
Date of Construction or Acquisition	2016
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 4,955
Deductions during year [Abstract]
Balance at close of year	139
Multi-Family Residential [Member] | Gables Townhomes - Sioux Falls, SD [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				1,399
Initial Cost to Company [Abstract]
Land				349
Buildings & Improvements				1,921
Costs capitalized subsequent to acquisition				214
Gross amount at which carried at close of period [Abstract]
Land				383
Buildings & Improvements				2,101
Total	2,484			2,484
Accumulated Depreciation	$ (306)			(306)
Date of Construction or Acquisition	2011
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 2,484
Deductions during year [Abstract]
Balance at close of year	306
Multi-Family Residential [Member] | Gardens - Grand Forks, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				0
Initial Cost to Company [Abstract]
Land				518
Buildings & Improvements				8,702
Costs capitalized subsequent to acquisition				96
Gross amount at which carried at close of period [Abstract]
Land				528
Buildings & Improvements				8,788
Total	9,316			9,316
Accumulated Depreciation	$ (403)			(403)
Date of Construction or Acquisition	2015
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 9,316
Deductions during year [Abstract]
Balance at close of year	403
Multi-Family Residential [Member] | Grand Gateway - St. Cloud, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				0
Initial Cost to Company [Abstract]
Land				814
Buildings & Improvements				7,086
Costs capitalized subsequent to acquisition				1,823
Gross amount at which carried at close of period [Abstract]
Land				936
Buildings & Improvements				8,787
Total	9,723			9,723
Accumulated Depreciation	$ (1,362)			(1,362)
Date of Construction or Acquisition	2012
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 9,723
Deductions during year [Abstract]
Balance at close of year	1,362
Multi-Family Residential [Member] | 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				1,305
Gross amount at which carried at close of period [Abstract]
Land				5,044
Buildings & Improvements				51,627
Total	56,671			56,671
Accumulated Depreciation	$ (2,181)			(2,181)
Date of Construction or Acquisition	2015
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 56,671
Deductions during year [Abstract]
Balance at close of year	2,181
Multi-Family Residential [Member] | Greenfield - Omaha, NE [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				3,451
Initial Cost to Company [Abstract]
Land				578
Buildings & Improvements				4,122
Costs capitalized subsequent to acquisition				1,206
Gross amount at which carried at close of period [Abstract]
Land				843
Buildings & Improvements				5,063
Total	5,906			5,906
Accumulated Depreciation	$ (1,274)			(1,274)
Date of Construction or Acquisition	2007
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 5,906
Deductions during year [Abstract]
Balance at close of year	1,274
Multi-Family Residential [Member] | Heritage Manor - Rochester, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				3,558
Initial Cost to Company [Abstract]
Land				403
Buildings & Improvements				6,968
Costs capitalized subsequent to acquisition				3,093
Gross amount at which carried at close of period [Abstract]
Land				605
Buildings & Improvements				9,859
Total	10,464			10,464
Accumulated Depreciation	$ (4,345)			(4,345)
Date of Construction or Acquisition	1998
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 10,464
Deductions during year [Abstract]
Balance at close of year	4,345
Multi-Family Residential [Member] | Homestead Garden - Rapid City, SD [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				3,024
Initial Cost to Company [Abstract]
Land				655
Buildings & Improvements				14,139
Costs capitalized subsequent to acquisition				448
Gross amount at which carried at close of period [Abstract]
Land				713
Buildings & Improvements				14,529
Total	15,242			15,242
Accumulated Depreciation	$ (1,158)			(1,158)
Date of Construction or Acquisition	2015
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 15,242
Deductions during year [Abstract]
Balance at close of year	1,158
Multi-Family Residential [Member] | Indian Hills - Sioux City, IA [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				0
Initial Cost to Company [Abstract]
Land				294
Buildings & Improvements				2,921
Costs capitalized subsequent to acquisition				4,281
Gross amount at which carried at close of period [Abstract]
Land				444
Buildings & Improvements				7,052
Total	7,496			7,496
Accumulated Depreciation	$ (1,803)			(1,803)
Date of Construction or Acquisition	2007
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 7,496
Deductions during year [Abstract]
Balance at close of year	1,803
Multi-Family Residential [Member] | Kirkwood Manor - Bismarck, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				3,145
Initial Cost to Company [Abstract]
Land				449
Buildings & Improvements				2,725
Costs capitalized subsequent to acquisition				1,825
Gross amount at which carried at close of period [Abstract]
Land				598
Buildings & Improvements				4,401
Total	4,999			4,999
Accumulated Depreciation	$ (2,039)			(2,039)
Date of Construction or Acquisition	1997
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 4,999
Deductions during year [Abstract]
Balance at close of year	$ 2,039
Multi-Family Residential [Member] | Kirkwood Manor - Bismarck, ND [Member] | Minimum [Member]
Gross amount at which carried at close of period [Abstract]
Life on which depreciation in latest income statement is computed	12 years
Multi-Family Residential [Member] | Kirkwood Manor - Bismarck, ND [Member] | Maximum [Member]
Gross amount at which carried at close of period [Abstract]
Life on which depreciation in latest income statement is computed	40 years
Multi-Family Residential [Member] | Lakeside Village Lincoln, NE [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				12,593
Initial Cost to Company [Abstract]
Land				1,215
Buildings & Improvements				15,837
Costs capitalized subsequent to acquisition				859
Gross amount at which carried at close of period [Abstract]
Land				1,302
Buildings & Improvements				16,609
Total	$ 17,911			17,911
Accumulated Depreciation	$ (2,294)			(2,294)
Date of Construction or Acquisition	2012
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 17,911
Deductions during year [Abstract]
Balance at close of year	2,294
Multi-Family Residential [Member] | Landmark - Grand Forks, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				0
Initial Cost to Company [Abstract]
Land				184
Buildings & Improvements				1,514
Costs capitalized subsequent to acquisition				1,188
Gross amount at which carried at close of period [Abstract]
Land				355
Buildings & Improvements				2,531
Total	2,886			2,886
Accumulated Depreciation	$ (1,217)			(1,217)
Date of Construction or Acquisition	1997
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 2,886
Deductions during year [Abstract]
Balance at close of year	1,217
Multi-Family Residential [Member] | Legacy - Grand Forks, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				14,751
Initial Cost to Company [Abstract]
Land				1,362
Buildings & Improvements				21,727
Costs capitalized subsequent to acquisition				10,275
Gross amount at which carried at close of period [Abstract]
Land				2,252
Buildings & Improvements				31,112
Total	33,364			33,364
Accumulated Depreciation	(11,970)			(11,970)
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	33,364
Deductions during year [Abstract]
Balance at close of year	$ 11,970
Multi-Family Residential [Member] | Legacy - Grand Forks, ND [Member] | Minimum [Member]
Gross amount at which carried at close of period [Abstract]
Date of Construction or Acquisition	1995
Life on which depreciation in latest income statement is computed	24 years
Multi-Family Residential [Member] | Legacy - Grand Forks, ND [Member] | Maximum [Member]
Gross amount at which carried at close of period [Abstract]
Date of Construction or Acquisition	2005
Life on which depreciation in latest income statement is computed	40 years
Multi-Family Residential [Member] | Legacy Heights - Bismarck, ND [Member]
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				327
Gross amount at which carried at close of period [Abstract]
Land				1,265
Buildings & Improvements				14,011
Total	$ 15,276			15,276
Accumulated Depreciation	$ (757)			(757)
Date of Construction or Acquisition	2015
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 15,276
Deductions during year [Abstract]
Balance at close of year	757
Multi-Family Residential [Member] | Mariposa - Topeka, KS [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				2,816
Initial Cost to Company [Abstract]
Land				399
Buildings & Improvements				5,110
Costs capitalized subsequent to acquisition				826
Gross amount at which carried at close of period [Abstract]
Land				434
Buildings & Improvements				5,901
Total	6,335			6,335
Accumulated Depreciation	$ (1,777)			(1,777)
Date of Construction or Acquisition	2004
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 6,335
Deductions during year [Abstract]
Balance at close of year	1,777
Multi-Family Residential [Member] | Meadows - Jamestown, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				0
Initial Cost to Company [Abstract]
Land				590
Buildings & Improvements				4,519
Costs capitalized subsequent to acquisition				1,840
Gross amount at which carried at close of period [Abstract]
Land				685
Buildings & Improvements				6,264
Total	6,949			6,949
Accumulated Depreciation	$ (2,486)			(2,486)
Date of Construction or Acquisition	1998
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 6,949
Deductions during year [Abstract]
Balance at close of year	2,486
Multi-Family Residential [Member] | Monticello Crossings - Monticello, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				0
Initial Cost to Company [Abstract]
Land				1,734
Buildings & Improvements				28,151
Costs capitalized subsequent to acquisition				641
Gross amount at which carried at close of period [Abstract]
Land				1,734
Buildings & Improvements				28,792
Total	30,526			30,526
Accumulated Depreciation	$ (402)			(402)
Date of Construction or Acquisition	2017
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 30,526
Deductions during year [Abstract]
Balance at close of year	402
Multi-Family Residential [Member] | Monticello Village - Monticello, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				2,853
Initial Cost to Company [Abstract]
Land				490
Buildings & Improvements				3,756
Costs capitalized subsequent to acquisition				960
Gross amount at which carried at close of period [Abstract]
Land				631
Buildings & Improvements				4,575
Total	5,206			5,206
Accumulated Depreciation	$ (1,489)			(1,489)
Date of Construction or Acquisition	2004
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 5,206
Deductions during year [Abstract]
Balance at close of year	1,489
Multi-Family Residential [Member] | Northern Valley - Rochester, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				0
Initial Cost to Company [Abstract]
Land				110
Buildings & Improvements				610
Costs capitalized subsequent to acquisition				153
Gross amount at which carried at close of period [Abstract]
Land				122
Buildings & Improvements				751
Total	873			873
Accumulated Depreciation	$ (152)			(152)
Date of Construction or Acquisition	2010
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 873
Deductions during year [Abstract]
Balance at close of year	152
Multi-Family Residential [Member] | North Pointe - Bismarck, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				3,274
Initial Cost to Company [Abstract]
Land				303
Buildings & Improvements				3,957
Costs capitalized subsequent to acquisition				1,249
Gross amount at which carried at close of period [Abstract]
Land				361
Buildings & Improvements				5,148
Total	5,509			5,509
Accumulated Depreciation	(1,733)			(1,733)
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	5,509
Deductions during year [Abstract]
Balance at close of year	$ 1,733
Multi-Family Residential [Member] | North Pointe - Bismarck, ND [Member] | Minimum [Member]
Gross amount at which carried at close of period [Abstract]
Date of Construction or Acquisition	1995
Life on which depreciation in latest income statement is computed	24 years
Multi-Family Residential [Member] | North Pointe - Bismarck, ND [Member] | Maximum [Member]
Gross amount at which carried at close of period [Abstract]
Date of Construction or Acquisition	2011
Life on which depreciation in latest income statement is computed	40 years
Multi-Family Residential [Member] | Northridge - Bismarck, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				5,986
Initial Cost to Company [Abstract]
Land				884
Buildings & Improvements				7,515
Costs capitalized subsequent to acquisition				132
Gross amount at which carried at close of period [Abstract]
Land				959
Buildings & Improvements				7,572
Total	$ 8,531			8,531
Accumulated Depreciation	$ (544)			(544)
Date of Construction or Acquisition	2015
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 8,531
Deductions during year [Abstract]
Balance at close of year	544
Multi-Family Residential [Member] | Oakmont Estates - Sioux Falls, SD [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				2,300
Initial Cost to Company [Abstract]
Land				422
Buildings & Improvements				4,838
Costs capitalized subsequent to acquisition				1,162
Gross amount at which carried at close of period [Abstract]
Land				697
Buildings & Improvements				5,725
Total	6,422			6,422
Accumulated Depreciation	$ (2,096)			(2,096)
Date of Construction or Acquisition	2002
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 6,422
Deductions during year [Abstract]
Balance at close of year	2,096
Multi-Family Residential [Member] | Oakwood Estates - Sioux Falls, SD [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				3,749
Initial Cost to Company [Abstract]
Land				543
Buildings & Improvements				2,784
Costs capitalized subsequent to acquisition				4,646
Gross amount at which carried at close of period [Abstract]
Land				860
Buildings & Improvements				7,113
Total	7,973			7,973
Accumulated Depreciation	$ (3,640)			(3,640)
Date of Construction or Acquisition	1993
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 7,973
Deductions during year [Abstract]
Balance at close of year	3,640
Multi-Family Residential [Member] | Olympic Village - Billings, MT [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				10,158
Initial Cost to Company [Abstract]
Land				1,164
Buildings & Improvements				10,441
Costs capitalized subsequent to acquisition				3,734
Gross amount at which carried at close of period [Abstract]
Land				1,810
Buildings & Improvements				13,529
Total	15,339			15,339
Accumulated Depreciation	$ (5,662)			(5,662)
Date of Construction or Acquisition	2000
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 15,339
Deductions during year [Abstract]
Balance at close of year	5,662
Multi-Family Residential [Member] | Olympik Village - Rochester, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				4,128
Initial Cost to Company [Abstract]
Land				1,034
Buildings & Improvements				6,109
Costs capitalized subsequent to acquisition				2,449
Gross amount at which carried at close of period [Abstract]
Land				1,239
Buildings & Improvements				8,353
Total	9,592			9,592
Accumulated Depreciation	$ (2,579)			(2,579)
Date of Construction or Acquisition	2005
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 9,592
Deductions during year [Abstract]
Balance at close of year	2,579
Multi-Family Residential [Member] | Oxbow Park - Sioux Falls, SD [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				3,661
Initial Cost to Company [Abstract]
Land				404
Buildings & Improvements				3,152
Costs capitalized subsequent to acquisition				3,654
Gross amount at which carried at close of period [Abstract]
Land				972
Buildings & Improvements				6,238
Total	7,210			7,210
Accumulated Depreciation	$ (3,191)			(3,191)
Date of Construction or Acquisition	1994
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 7,210
Deductions during year [Abstract]
Balance at close of year	$ 3,191
Multi-Family Residential [Member] | Oxbow Park - Sioux Falls, SD [Member] | Minimum [Member]
Gross amount at which carried at close of period [Abstract]
Life on which depreciation in latest income statement is computed	24 years
Multi-Family Residential [Member] | Oxbow Park - Sioux Falls, SD [Member] | Maximum [Member]
Gross amount at which carried at close of period [Abstract]
Life on which depreciation in latest income statement is computed	40 years
Multi-Family Residential [Member] | Park Meadows - Waite Park, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				8,195
Initial Cost to Company [Abstract]
Land				1,143
Buildings & Improvements				9,099
Costs capitalized subsequent to acquisition				9,373
Gross amount at which carried at close of period [Abstract]
Land				1,892
Buildings & Improvements				17,723
Total	$ 19,615			19,615
Accumulated Depreciation	$ (7,153)			(7,153)
Date of Construction or Acquisition	1997
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 19,615
Deductions during year [Abstract]
Balance at close of year	7,153
Multi-Family Residential [Member] | Pebble Springs - Bismarck, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				716
Initial Cost to Company [Abstract]
Land				7
Buildings & Improvements				748
Costs capitalized subsequent to acquisition				207
Gross amount at which carried at close of period [Abstract]
Land				57
Buildings & Improvements				905
Total	962			962
Accumulated Depreciation	$ (401)			(401)
Date of Construction or Acquisition	1999
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 962
Deductions during year [Abstract]
Balance at close of year	401
Multi-Family Residential [Member] | Pinehurst - Billings, MT [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				121
Initial Cost to Company [Abstract]
Land				72
Buildings & Improvements				687
Costs capitalized subsequent to acquisition				418
Gross amount at which carried at close of period [Abstract]
Land				168
Buildings & Improvements				1,009
Total	1,177			1,177
Accumulated Depreciation	$ (358)			(358)
Date of Construction or Acquisition	2002
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 1,177
Deductions during year [Abstract]
Balance at close of year	358
Multi-Family Residential [Member] | Plaza - Minot, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				5,068
Initial Cost to Company [Abstract]
Land				867
Buildings & Improvements				12,784
Costs capitalized subsequent to acquisition				2,774
Gross amount at which carried at close of period [Abstract]
Land				998
Buildings & Improvements				15,427
Total	16,425			16,425
Accumulated Depreciation	$ (3,285)			(3,285)
Date of Construction or Acquisition	2009
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 16,425
Deductions during year [Abstract]
Balance at close of year	3,285
Multi-Family Residential [Member] | Pointe West - Rapid City, SD [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				2,504
Initial Cost to Company [Abstract]
Land				240
Buildings & Improvements				3,538
Costs capitalized subsequent to acquisition				1,917
Gross amount at which carried at close of period [Abstract]
Land				406
Buildings & Improvements				5,289
Total	5,695			5,695
Accumulated Depreciation	$ (2,684)			(2,684)
Date of Construction or Acquisition	1994
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 5,695
Deductions during year [Abstract]
Balance at close of year	$ 2,684
Multi-Family Residential [Member] | Pointe West - Rapid City, SD [Member] | Minimum [Member]
Gross amount at which carried at close of period [Abstract]
Life on which depreciation in latest income statement is computed	24 years
Multi-Family Residential [Member] | Pointe West - Rapid City, SD [Member] | Maximum [Member]
Gross amount at which carried at close of period [Abstract]
Life on which depreciation in latest income statement is computed	40 years
Multi-Family Residential [Member] | Ponds at Heritage Place - Sartell, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				3,641
Initial Cost to Company [Abstract]
Land				395
Buildings & Improvements				4,564
Costs capitalized subsequent to acquisition				425
Gross amount at which carried at close of period [Abstract]
Land				410
Buildings & Improvements				4,974
Total	$ 5,384			5,384
Accumulated Depreciation	$ (676)			(676)
Date of Construction or Acquisition	2012
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 5,384
Deductions during year [Abstract]
Balance at close of year	676
Multi-Family Residential [Member] | Prairie Winds - Sioux Falls, SD [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				1,349
Initial Cost to Company [Abstract]
Land				144
Buildings & Improvements				1,816
Costs capitalized subsequent to acquisition				646
Gross amount at which carried at close of period [Abstract]
Land				304
Buildings & Improvements				2,302
Total	2,606			2,606
Accumulated Depreciation	$ (1,357)			(1,357)
Date of Construction or Acquisition	1993
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 2,606
Deductions during year [Abstract]
Balance at close of year	$ 1,357
Multi-Family Residential [Member] | Prairie Winds - Sioux Falls, SD [Member] | Minimum [Member]
Gross amount at which carried at close of period [Abstract]
Life on which depreciation in latest income statement is computed	24 years
Multi-Family Residential [Member] | Prairie Winds - Sioux Falls, SD [Member] | Maximum [Member]
Gross amount at which carried at close of period [Abstract]
Life on which depreciation in latest income statement is computed	40 years
Multi-Family Residential [Member] | Quarry Ridge - Rochester, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				26,219
Initial Cost to Company [Abstract]
Land				2,254
Buildings & Improvements				30,024
Costs capitalized subsequent to acquisition				1,990
Gross amount at which carried at close of period [Abstract]
Land				2,401
Buildings & Improvements				31,867
Total	$ 34,268			34,268
Accumulated Depreciation	$ (6,378)			(6,378)
Date of Construction or Acquisition	2006
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 34,268
Deductions during year [Abstract]
Balance at close of year	6,378
Multi-Family Residential [Member] | RED 20 - Minneapolis, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				22,953
Initial Cost to Company [Abstract]
Land				1,900
Buildings & Improvements				26,641
Costs capitalized subsequent to acquisition				333
Gross amount at which carried at close of period [Abstract]
Land				1,900
Buildings & Improvements				26,974
Total	28,874			28,874
Accumulated Depreciation	$ (2,271)			(2,271)
Date of Construction or Acquisition	2015
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 28,874
Deductions during year [Abstract]
Balance at close of year	2,271
Multi-Family Residential [Member] | Regency Park Estates - St. Cloud, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				8,176
Initial Cost to Company [Abstract]
Land				702
Buildings & Improvements				10,198
Costs capitalized subsequent to acquisition				2,168
Gross amount at which carried at close of period [Abstract]
Land				949
Buildings & Improvements				12,119
Total	13,068			13,068
Accumulated Depreciation	$ (1,945)			(1,945)
Date of Construction or Acquisition	2011
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 13,068
Deductions during year [Abstract]
Balance at close of year	1,945
Multi-Family Residential [Member] | Renaissance Heights - Williston, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				23,439
Initial Cost to Company [Abstract]
Land				3,080
Buildings & Improvements				15,389
Costs capitalized subsequent to acquisition				133
Gross amount at which carried at close of period [Abstract]
Land				3,086
Buildings & Improvements				15,516
Total	18,602			18,602
Accumulated Depreciation	$ (279)			(279)
Date of Construction or Acquisition	2013
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 18,602
Deductions during year [Abstract]
Balance at close of year	279
Multi-Family Residential [Member] | Ridge Oaks - Sioux City, IA [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				3,240
Initial Cost to Company [Abstract]
Land				178
Buildings & Improvements				4,073
Costs capitalized subsequent to acquisition				2,851
Gross amount at which carried at close of period [Abstract]
Land				307
Buildings & Improvements				6,795
Total	7,102			7,102
Accumulated Depreciation	$ (2,584)			(2,584)
Date of Construction or Acquisition	2001
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 7,102
Deductions during year [Abstract]
Balance at close of year	2,584
Multi-Family Residential [Member] | Rimrock West - Billings, MT [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				3,160
Initial Cost to Company [Abstract]
Land				330
Buildings & Improvements				3,489
Costs capitalized subsequent to acquisition				1,966
Gross amount at which carried at close of period [Abstract]
Land				476
Buildings & Improvements				5,309
Total	5,785			5,785
Accumulated Depreciation	$ (2,066)			(2,066)
Date of Construction or Acquisition	1999
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 5,785
Deductions during year [Abstract]
Balance at close of year	2,066
Multi-Family Residential [Member] | River Ridge - Bismarck, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				0
Initial Cost to Company [Abstract]
Land				576
Buildings & Improvements				24,670
Costs capitalized subsequent to acquisition				804
Gross amount at which carried at close of period [Abstract]
Land				763
Buildings & Improvements				25,287
Total	26,050			26,050
Accumulated Depreciation	$ (3,072)			(3,072)
Date of Construction or Acquisition	2008
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 26,050
Deductions during year [Abstract]
Balance at close of year	3,072
Multi-Family Residential [Member] | Rocky Meadows - Billings, MT [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				4,899
Initial Cost to Company [Abstract]
Land				656
Buildings & Improvements				5,726
Costs capitalized subsequent to acquisition				1,469
Gross amount at which carried at close of period [Abstract]
Land				792
Buildings & Improvements				7,059
Total	7,851			7,851
Accumulated Depreciation	$ (3,495)			(3,495)
Date of Construction or Acquisition	1995
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 7,851
Deductions during year [Abstract]
Balance at close of year	3,495
Multi-Family Residential [Member] | Rum River - Isanti, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				3,380
Initial Cost to Company [Abstract]
Land				843
Buildings & Improvements				4,823
Costs capitalized subsequent to acquisition				348
Gross amount at which carried at close of period [Abstract]
Land				864
Buildings & Improvements				5,150
Total	6,014			6,014
Accumulated Depreciation	$ (1,314)			(1,314)
Date of Construction or Acquisition	2007
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 6,014
Deductions during year [Abstract]
Balance at close of year	1,314
Multi-Family Residential [Member] | Sherwood - Topeka, KS [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				11,686
Initial Cost to Company [Abstract]
Land				1,142
Buildings & Improvements				14,684
Costs capitalized subsequent to acquisition				4,795
Gross amount at which carried at close of period [Abstract]
Land				1,838
Buildings & Improvements				18,783
Total	20,621			20,621
Accumulated Depreciation	$ (7,637)			(7,637)
Date of Construction or Acquisition	1999
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 20,621
Deductions during year [Abstract]
Balance at close of year	7,637
Multi-Family Residential [Member] | Sierra Vista - Sioux Falls, SD [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				1,323
Initial Cost to Company [Abstract]
Land				241
Buildings & Improvements				2,097
Costs capitalized subsequent to acquisition				520
Gross amount at which carried at close of period [Abstract]
Land				276
Buildings & Improvements				2,582
Total	2,858			2,858
Accumulated Depreciation	$ (432)			(432)
Date of Construction or Acquisition	2011
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 2,858
Deductions during year [Abstract]
Balance at close of year	432
Multi-Family Residential [Member] | Silver Springs - Rapid City, SD [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				2,156
Initial Cost to Company [Abstract]
Land				215
Buildings & Improvements				3,007
Costs capitalized subsequent to acquisition				583
Gross amount at which carried at close of period [Abstract]
Land				237
Buildings & Improvements				3,568
Total	3,805			3,805
Accumulated Depreciation	$ (271)			(271)
Date of Construction or Acquisition	2015
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 3,805
Deductions during year [Abstract]
Balance at close of year	271
Multi-Family Residential [Member] | South Pointe - Minot, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				8,229
Initial Cost to Company [Abstract]
Land				550
Buildings & Improvements				9,548
Costs capitalized subsequent to acquisition				4,908
Gross amount at which carried at close of period [Abstract]
Land				1,370
Buildings & Improvements				13,636
Total	15,006			15,006
Accumulated Depreciation	$ (6,351)			(6,351)
Date of Construction or Acquisition	1995
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 15,006
Deductions during year [Abstract]
Balance at close of year	$ 6,351
Multi-Family Residential [Member] | South Pointe - Minot, ND [Member] | Minimum [Member]
Gross amount at which carried at close of period [Abstract]
Life on which depreciation in latest income statement is computed	24 years
Multi-Family Residential [Member] | South Pointe - Minot, ND [Member] | Maximum [Member]
Gross amount at which carried at close of period [Abstract]
Life on which depreciation in latest income statement is computed	40 years
Multi-Family Residential [Member] | Southpoint - Grand Forks, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				0
Initial Cost to Company [Abstract]
Land				576
Buildings & Improvements				9,893
Costs capitalized subsequent to acquisition				147
Gross amount at which carried at close of period [Abstract]
Land				622
Buildings & Improvements				9,994
Total	$ 10,616			10,616
Accumulated Depreciation	$ (934)			(934)
Date of Construction or Acquisition	2013
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 10,616
Deductions during year [Abstract]
Balance at close of year	934
Multi-Family Residential [Member] | Southwind - Grand Forks, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				5,259
Initial Cost to Company [Abstract]
Land				400
Buildings & Improvements				5,034
Costs capitalized subsequent to acquisition				3,482
Gross amount at which carried at close of period [Abstract]
Land				812
Buildings & Improvements				8,104
Total	8,916			8,916
Accumulated Depreciation	$ (4,029)			(4,029)
Date of Construction or Acquisition	1995
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 8,916
Deductions during year [Abstract]
Balance at close of year	$ 4,029
Multi-Family Residential [Member] | Southwind - Grand Forks, ND [Member] | Minimum [Member]
Gross amount at which carried at close of period [Abstract]
Life on which depreciation in latest income statement is computed	24 years
Multi-Family Residential [Member] | Southwind - Grand Forks, ND [Member] | Maximum [Member]
Gross amount at which carried at close of period [Abstract]
Life on which depreciation in latest income statement is computed	40 years
Multi-Family Residential [Member] | Sunset Trail - Rochester, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				7,732
Initial Cost to Company [Abstract]
Land				336
Buildings & Improvements				12,814
Costs capitalized subsequent to acquisition				3,217
Gross amount at which carried at close of period [Abstract]
Land				687
Buildings & Improvements				15,680
Total	$ 16,367			16,367
Accumulated Depreciation	$ (6,374)			(6,374)
Date of Construction or Acquisition	1999
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 16,367
Deductions during year [Abstract]
Balance at close of year	6,374
Multi-Family Residential [Member] | Thomasbrook - Lincoln, NE [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				5,687
Initial Cost to Company [Abstract]
Land				600
Buildings & Improvements				10,306
Costs capitalized subsequent to acquisition				4,944
Gross amount at which carried at close of period [Abstract]
Land				1,430
Buildings & Improvements				14,420
Total	15,850			15,850
Accumulated Depreciation	$ (5,322)			(5,322)
Date of Construction or Acquisition	1999
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 15,850
Deductions during year [Abstract]
Balance at close of year	5,322
Multi-Family Residential [Member] | Valley Park - Grand Forks, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				3,683
Initial Cost to Company [Abstract]
Land				294
Buildings & Improvements				4,137
Costs capitalized subsequent to acquisition				3,840
Gross amount at which carried at close of period [Abstract]
Land				1,186
Buildings & Improvements				7,085
Total	8,271			8,271
Accumulated Depreciation	$ (3,107)			(3,107)
Date of Construction or Acquisition	1999
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 8,271
Deductions during year [Abstract]
Balance at close of year	3,107
Multi-Family Residential [Member] | Villa West - Topeka, KS [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				11,729
Initial Cost to Company [Abstract]
Land				1,590
Buildings & Improvements				15,760
Costs capitalized subsequent to acquisition				1,424
Gross amount at which carried at close of period [Abstract]
Land				2,084
Buildings & Improvements				16,690
Total	18,774			18,774
Accumulated Depreciation	$ (2,367)			(2,367)
Date of Construction or Acquisition	2012
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 18,774
Deductions during year [Abstract]
Balance at close of year	2,367
Multi-Family Residential [Member] | Village Green - Rochester, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				0
Initial Cost to Company [Abstract]
Land				234
Buildings & Improvements				2,296
Costs capitalized subsequent to acquisition				1,073
Gross amount at which carried at close of period [Abstract]
Land				359
Buildings & Improvements				3,244
Total	3,603			3,603
Accumulated Depreciation	$ (1,106)			(1,106)
Date of Construction or Acquisition	2003
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 3,603
Deductions during year [Abstract]
Balance at close of year	1,106
Multi-Family Residential [Member] | West Stonehill - Waite Park, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				8,072
Initial Cost to Company [Abstract]
Land				939
Buildings & Improvements				10,167
Costs capitalized subsequent to acquisition				7,618
Gross amount at which carried at close of period [Abstract]
Land				1,715
Buildings & Improvements				17,009
Total	18,724			18,724
Accumulated Depreciation	$ (7,807)			(7,807)
Date of Construction or Acquisition	1995
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 18,724
Deductions during year [Abstract]
Balance at close of year	7,807
Multi-Family Residential [Member] | Westwood Park - Bismarck, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				1,879
Initial Cost to Company [Abstract]
Land				116
Buildings & Improvements				1,909
Costs capitalized subsequent to acquisition				2,023
Gross amount at which carried at close of period [Abstract]
Land				287
Buildings & Improvements				3,761
Total	4,048			4,048
Accumulated Depreciation	$ (1,681)			(1,681)
Date of Construction or Acquisition	1998
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 4,048
Deductions during year [Abstract]
Balance at close of year	1,681
Multi-Family Residential [Member] | Whispering Ridge - Omaha, NE [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				21,257
Initial Cost to Company [Abstract]
Land				2,139
Buildings & Improvements				25,424
Costs capitalized subsequent to acquisition				1,365
Gross amount at which carried at close of period [Abstract]
Land				2,403
Buildings & Improvements				26,525
Total	28,928			28,928
Accumulated Depreciation	$ (3,161)			(3,161)
Date of Construction or Acquisition	2012
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 28,928
Deductions during year [Abstract]
Balance at close of year	3,161
Multi-Family Residential [Member] | Williston Garden - Williston, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				7,541
Initial Cost to Company [Abstract]
Land				1,400
Buildings & Improvements				10,200
Costs capitalized subsequent to acquisition				211
Gross amount at which carried at close of period [Abstract]
Land				1,412
Buildings & Improvements				10,399
Total	11,811			11,811
Accumulated Depreciation	$ (190)			(190)
Date of Construction or Acquisition	2012
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 11,811
Deductions during year [Abstract]
Balance at close of year	190
Multi-Family Residential [Member] | Winchester - Rochester, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				0
Initial Cost to Company [Abstract]
Land				748
Buildings & Improvements				5,622
Costs capitalized subsequent to acquisition				2,512
Gross amount at which carried at close of period [Abstract]
Land				1,044
Buildings & Improvements				7,838
Total	8,882			8,882
Accumulated Depreciation	$ (2,672)			(2,672)
Date of Construction or Acquisition	2003
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 8,882
Deductions during year [Abstract]
Balance at close of year	2,672
Multi-Family Residential [Member] | Woodridge - Rochester, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				5,920
Initial Cost to Company [Abstract]
Land				370
Buildings & Improvements				6,028
Costs capitalized subsequent to acquisition				3,124
Gross amount at which carried at close of period [Abstract]
Land				741
Buildings & Improvements				8,781
Total	9,522			9,522
Accumulated Depreciation	$ (4,087)			(4,087)
Date of Construction or Acquisition	1997
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 9,522
Deductions during year [Abstract]
Balance at close of year	4,087
Multi-Family Residential [Member] | Wholly Owned Properties [Member]
Reconciliations of total real estate carrying value [Abstract]
Additions	61,565	282,457	183,114
Commercial Healthcare [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				96,408
Initial Cost to Company [Abstract]
Land				21,240
Buildings & Improvements				246,477
Costs capitalized subsequent to acquisition				55,431
Gross amount at which carried at close of period [Abstract]
Land				22,446
Buildings & Improvements				300,702
Total	323,148			323,148
Accumulated Depreciation	(86,139)			(86,139)
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	323,148
Deductions during year [Abstract]
Balance at close of year	86,139
Commercial Healthcare [Member] | 2800 Medical Building - Minneapolis, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				7,358
Initial Cost to Company [Abstract]
Land				204
Buildings & Improvements				7,135
Costs capitalized subsequent to acquisition				2,663
Gross amount at which carried at close of period [Abstract]
Land				229
Buildings & Improvements				9,773
Total	10,002			10,002
Accumulated Depreciation	$ (3,715)			(3,715)
Date of Construction or Acquisition	2005
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 10,002
Deductions during year [Abstract]
Balance at close of year	3,715
Commercial Healthcare [Member] | 2828 Chicago Avenue - Minneapolis, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				11,508
Initial Cost to Company [Abstract]
Land				726
Buildings & Improvements				11,319
Costs capitalized subsequent to acquisition				5,380
Gross amount at which carried at close of period [Abstract]
Land				729
Buildings & Improvements				16,696
Total	17,425			17,425
Accumulated Depreciation	$ (5,203)			(5,203)
Date of Construction or Acquisition	2007
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 17,425
Deductions during year [Abstract]
Balance at close of year	5,203
Commercial Healthcare [Member] | Airport Medical - Bloomington, MN [Member]
Initial Cost to Company [Abstract]
Buildings & Improvements				4,678
Costs capitalized subsequent to acquisition				51
Gross amount at which carried at close of period [Abstract]
Land				11
Buildings & Improvements				4,718
Total	4,729			4,729
Accumulated Depreciation	$ (1,967)			(1,967)
Date of Construction or Acquisition	2002
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 4,729
Deductions during year [Abstract]
Balance at close of year	1,967
Commercial Healthcare [Member] | Billings 2300 Grant Road - Billings, MT [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				0
Initial Cost to Company [Abstract]
Land				649
Buildings & Improvements				1,216
Gross amount at which carried at close of period [Abstract]
Land				649
Buildings & Improvements				1,216
Total	1,865			1,865
Accumulated Depreciation	$ (207)			(207)
Date of Construction or Acquisition	2010
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 1,865
Deductions during year [Abstract]
Balance at close of year	207
Commercial Healthcare [Member] | Burnsville 303 Nicollet Medical (Ridgeview) - Burnsville, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				7,705
Initial Cost to Company [Abstract]
Land				1,071
Buildings & Improvements				6,842
Costs capitalized subsequent to acquisition				2,393
Gross amount at which carried at close of period [Abstract]
Land				1,201
Buildings & Improvements				9,105
Total	10,306			10,306
Accumulated Depreciation	$ (2,240)			(2,240)
Date of Construction or Acquisition	2008
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 10,306
Deductions during year [Abstract]
Balance at close of year	2,240
Commercial Healthcare [Member] | Burnsville 305 Nicollet Medical (Ridgeview South) - Burnsville, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				4,823
Initial Cost to Company [Abstract]
Land				189
Buildings & Improvements				5,127
Costs capitalized subsequent to acquisition				1,764
Gross amount at which carried at close of period [Abstract]
Land				276
Buildings & Improvements				6,804
Total	7,080			7,080
Accumulated Depreciation	$ (1,486)			(1,486)
Date of Construction or Acquisition	2008
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 7,080
Deductions during year [Abstract]
Balance at close of year	1,486
Commercial Healthcare [Member] | Denfeld Clinic - Duluth, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				1,180
Initial Cost to Company [Abstract]
Land				501
Buildings & Improvements				2,597
Costs capitalized subsequent to acquisition				1
Gross amount at which carried at close of period [Abstract]
Land				501
Buildings & Improvements				2,598
Total	3,099			3,099
Accumulated Depreciation	$ (847)			(847)
Date of Construction or Acquisition	2004
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 3,099
Deductions during year [Abstract]
Balance at close of year	847
Commercial Healthcare [Member] | Eagan 1440 Duckwood Medical - Eagan, MN [Member]
Initial Cost to Company [Abstract]
Land				521
Buildings & Improvements				1,547
Costs capitalized subsequent to acquisition				556
Gross amount at which carried at close of period [Abstract]
Land				521
Buildings & Improvements				2,103
Total	2,624			2,624
Accumulated Depreciation	$ (825)			(825)
Date of Construction or Acquisition	2008
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 2,624
Deductions during year [Abstract]
Balance at close of year	825
Commercial Healthcare [Member] | Edina 6363 France Medical - Edina, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				0
Initial Cost to Company [Abstract]
Buildings & Improvements				12,675
Costs capitalized subsequent to acquisition				3,386
Gross amount at which carried at close of period [Abstract]
Buildings & Improvements				16,061
Total	16,061			16,061
Accumulated Depreciation	$ (5,179)			(5,179)
Date of Construction or Acquisition	2008
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 16,061
Deductions during year [Abstract]
Balance at close of year	5,179
Commercial Healthcare [Member] | Edina 6405 France Medical - Edina, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				0
Initial Cost to Company [Abstract]
Buildings & Improvements				12,201
Costs capitalized subsequent to acquisition				367
Gross amount at which carried at close of period [Abstract]
Buildings & Improvements				12,568
Total	12,568			12,568
Accumulated Depreciation	$ (3,863)			(3,863)
Date of Construction or Acquisition	2008
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 12,568
Deductions during year [Abstract]
Balance at close of year	3,863
Commercial Healthcare [Member] | Edina 6517 Drew Avenue - Edina, MN [Member]
Initial Cost to Company [Abstract]
Land				741
Buildings & Improvements				660
Costs capitalized subsequent to acquisition				1,035
Gross amount at which carried at close of period [Abstract]
Land				959
Buildings & Improvements				1,477
Total	2,436			2,436
Accumulated Depreciation	$ (277)			(277)
Date of Construction or Acquisition	2002
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 2,436
Deductions during year [Abstract]
Balance at close of year	277
Commercial Healthcare [Member] | Edina 6525 France SMC II - Edina, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				9,394
Initial Cost to Company [Abstract]
Land				755
Buildings & Improvements				8,054
Costs capitalized subsequent to acquisition				6,859
Gross amount at which carried at close of period [Abstract]
Land				1,040
Buildings & Improvements				14,628
Total	15,668			15,668
Accumulated Depreciation	$ (6,817)			(6,817)
Date of Construction or Acquisition	2003
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 15,668
Deductions during year [Abstract]
Balance at close of year	6,817
Commercial Healthcare [Member] | Edina 6545 France SMC I - Edina MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				28,331
Initial Cost to Company [Abstract]
Land				3,480
Buildings & Improvements				63,275
Costs capitalized subsequent to acquisition				18,446
Gross amount at which carried at close of period [Abstract]
Land				3,480
Buildings & Improvements				81,721
Total	85,201			85,201
Accumulated Depreciation	$ (21,746)			(21,746)
Date of Construction or Acquisition	2001
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 85,201
Deductions during year [Abstract]
Balance at close of year	21,746
Commercial Healthcare [Member] | Fresenius - Duluth, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				0
Initial Cost to Company [Abstract]
Land				50
Buildings & Improvements				1,520
Costs capitalized subsequent to acquisition				2
Gross amount at which carried at close of period [Abstract]
Land				50
Buildings & Improvements				1,522
Total	1,572			1,572
Accumulated Depreciation	$ (496)			(496)
Date of Construction or Acquisition	2004
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 1,572
Deductions during year [Abstract]
Balance at close of year	496
Commercial Healthcare [Member] | Garden View - St. Paul, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				0
Initial Cost to Company [Abstract]
Buildings & Improvements				7,408
Costs capitalized subsequent to acquisition				1,175
Gross amount at which carried at close of period [Abstract]
Land				26
Buildings & Improvements				8,557
Total	8,583			8,583
Accumulated Depreciation	$ (3,298)			(3,298)
Date of Construction or Acquisition	2002
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 8,583
Deductions during year [Abstract]
Balance at close of year	3,298
Commercial Healthcare [Member] | Gateway Clinic - Sandstone, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				683
Initial Cost to Company [Abstract]
Land				77
Buildings & Improvements				1,699
Gross amount at which carried at close of period [Abstract]
Land				77
Buildings & Improvements				1,699
Total	1,776			1,776
Accumulated Depreciation	$ (554)			(554)
Date of Construction or Acquisition	2004
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 1,776
Deductions during year [Abstract]
Balance at close of year	554
Commercial Healthcare [Member] | High Pointe Health Campus - Lake Elmo, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				7,278
Initial Cost to Company [Abstract]
Land				1,305
Buildings & Improvements				10,528
Costs capitalized subsequent to acquisition				2,300
Gross amount at which carried at close of period [Abstract]
Land				1,506
Buildings & Improvements				12,627
Total	14,133			14,133
Accumulated Depreciation	$ (4,692)			(4,692)
Date of Construction or Acquisition	2004
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 14,133
Deductions during year [Abstract]
Balance at close of year	4,692
Commercial Healthcare [Member] | Lakeside Medical Plaza - Omaha, NE [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				0
Initial Cost to Company [Abstract]
Land				903
Buildings & Improvements				5,210
Gross amount at which carried at close of period [Abstract]
Land				903
Buildings & Improvements				5,210
Total	6,113			6,113
Accumulated Depreciation	$ (227)			(227)
Date of Construction or Acquisition	2015
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 6,113
Deductions during year [Abstract]
Balance at close of year	227
Commercial Healthcare [Member] | Mariner Clinic - Superior, WI [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				1,494
Initial Cost to Company [Abstract]
Buildings & Improvements				3,781
Costs capitalized subsequent to acquisition				323
Gross amount at which carried at close of period [Abstract]
Land				46
Buildings & Improvements				4,058
Total	4,104			4,104
Accumulated Depreciation	$ (1,294)			(1,294)
Date of Construction or Acquisition	2004
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 4,104
Deductions during year [Abstract]
Balance at close of year	1,294
Commercial Healthcare [Member] | Minneapolis 701 25th Avenue Medical - Minneapolis, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				0
Initial Cost to Company [Abstract]
Buildings & Improvements				7,873
Costs capitalized subsequent to acquisition				1,626
Gross amount at which carried at close of period [Abstract]
Buildings & Improvements				9,499
Total	9,499			9,499
Accumulated Depreciation	$ (2,561)			(2,561)
Date of Construction or Acquisition	2008
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 9,499
Deductions during year [Abstract]
Balance at close of year	2,561
Commercial Healthcare [Member] | Missoula 3050 Great Northern - Missoula, MT [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				0
Initial Cost to Company [Abstract]
Land				640
Buildings & Improvements				1,331
Gross amount at which carried at close of period [Abstract]
Land				640
Buildings & Improvements				1,331
Total	1,971			1,971
Accumulated Depreciation	$ (226)			(226)
Date of Construction or Acquisition	2010
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 1,971
Deductions during year [Abstract]
Balance at close of year	226
Commercial Healthcare [Member] | Park Dental - Brooklyn Center, MN [Member]
Initial Cost to Company [Abstract]
Land				185
Buildings & Improvements				2,767
Costs capitalized subsequent to acquisition				15
Gross amount at which carried at close of period [Abstract]
Land				200
Buildings & Improvements				2,767
Total	2,967			2,967
Accumulated Depreciation	$ (1,013)			(1,013)
Date of Construction or Acquisition	2002
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 2,967
Deductions during year [Abstract]
Balance at close of year	1,013
Commercial Healthcare [Member] | Pavilion I - Duluth, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				3,937
Initial Cost to Company [Abstract]
Land				1,245
Buildings & Improvements				8,898
Costs capitalized subsequent to acquisition				391
Gross amount at which carried at close of period [Abstract]
Land				1,245
Buildings & Improvements				9,289
Total	10,534			10,534
Accumulated Depreciation	$ (2,915)			(2,915)
Date of Construction or Acquisition	2004
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 10,534
Deductions during year [Abstract]
Balance at close of year	2,915
Commercial Healthcare [Member] | Pavilion II - Duluth, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				7,245
Initial Cost to Company [Abstract]
Land				2,715
Buildings & Improvements				14,673
Costs capitalized subsequent to acquisition				1,937
Gross amount at which carried at close of period [Abstract]
Land				2,715
Buildings & Improvements				16,610
Total	19,325			19,325
Accumulated Depreciation	$ (6,676)			(6,676)
Date of Construction or Acquisition	2004
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 19,325
Deductions during year [Abstract]
Balance at close of year	6,676
Commercial Healthcare [Member] | PrairieCare Medical - Brooklyn Park, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				0
Initial Cost to Company [Abstract]
Land				2,610
Buildings & Improvements				21,847
Gross amount at which carried at close of period [Abstract]
Land				2,610
Buildings & Improvements				21,847
Total	24,457			24,457
Accumulated Depreciation	$ (1,104)			(1,104)
Date of Construction or Acquisition	2015
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 24,457
Deductions during year [Abstract]
Balance at close of year	1,104
Commercial Healthcare [Member] | Ritchie Medical Plaza - St Paul, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				0
Initial Cost to Company [Abstract]
Land				1,615
Buildings & Improvements				7,851
Costs capitalized subsequent to acquisition				4,447
Gross amount at which carried at close of period [Abstract]
Land				1,647
Buildings & Improvements				12,266
Total	13,913			13,913
Accumulated Depreciation	$ (3,982)			(3,982)
Date of Construction or Acquisition	2005
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 13,913
Deductions during year [Abstract]
Balance at close of year	3,982
Commercial Healthcare [Member] | St Michael Clinic - St Michael, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				0
Initial Cost to Company [Abstract]
Land				328
Buildings & Improvements				2,259
Costs capitalized subsequent to acquisition				296
Gross amount at which carried at close of period [Abstract]
Land				349
Buildings & Improvements				2,534
Total	2,883			2,883
Accumulated Depreciation	$ (637)			(637)
Date of Construction or Acquisition	2007
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 2,883
Deductions during year [Abstract]
Balance at close of year	637
Commercial Healthcare [Member] | Trinity at Plaza 16 - Minot, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				4,430
Initial Cost to Company [Abstract]
Land				568
Buildings & Improvements				9,009
Costs capitalized subsequent to acquisition				16
Gross amount at which carried at close of period [Abstract]
Land				674
Buildings & Improvements				8,919
Total	9,593			9,593
Accumulated Depreciation	$ (1,278)			(1,278)
Date of Construction or Acquisition	2011
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 9,593
Deductions during year [Abstract]
Balance at close of year	1,278
Commercial Healthcare [Member] | Wells Clinic - Hibbing, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				1,042
Initial Cost to Company [Abstract]
Land				162
Buildings & Improvements				2,497
Costs capitalized subsequent to acquisition				2
Gross amount at which carried at close of period [Abstract]
Land				162
Buildings & Improvements				2,499
Total	2,661			2,661
Accumulated Depreciation	$ (814)			(814)
Date of Construction or Acquisition	2004
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 2,661
Deductions during year [Abstract]
Balance at close of year	814
Commercial Healthcare [Member] | Wholly Owned Properties [Member]
Reconciliations of total real estate carrying value [Abstract]
Additions		63,605
All Other [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				20,529
Initial Cost to Company [Abstract]
Land				11,783
Buildings & Improvements				57,217
Costs capitalized subsequent to acquisition				24,792
Gross amount at which carried at close of period [Abstract]
Land				12,692
Buildings & Improvements				81,100
Total	93,792			93,792
Accumulated Depreciation	(21,686)			(21,686)
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	93,792
Deductions during year [Abstract]
Balance at close of year	21,686
All Other [Member] | Bismarck 715 East Broadway - Bismarck, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				1,974
Initial Cost to Company [Abstract]
Land				389
Buildings & Improvements				1,283
Costs capitalized subsequent to acquisition				1,134
Gross amount at which carried at close of period [Abstract]
Land				443
Buildings & Improvements				2,363
Total	2,806			2,806
Accumulated Depreciation	$ (630)			(630)
Date of Construction or Acquisition	2008
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 2,806
Deductions during year [Abstract]
Balance at close of year	630
All Other [Member] | Bloomington 2000 W 94th Street - Bloomington, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				0
Initial Cost to Company [Abstract]
Land				2,133
Buildings & Improvements				4,097
Costs capitalized subsequent to acquisition				1,322
Gross amount at which carried at close of period [Abstract]
Land				2,241
Buildings & Improvements				5,311
Total	7,552			7,552
Accumulated Depreciation	$ (1,878)			(1,878)
Date of Construction or Acquisition	2006
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 7,552
Deductions during year [Abstract]
Balance at close of year	1,878
All Other [Member] | Dakota West Plaza - Minot , ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				328
Initial Cost to Company [Abstract]
Land				92
Buildings & Improvements				493
Costs capitalized subsequent to acquisition				30
Gross amount at which carried at close of period [Abstract]
Land				106
Buildings & Improvements				509
Total	615			615
Accumulated Depreciation	$ (149)			(149)
Date of Construction or Acquisition	2006
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 615
Deductions during year [Abstract]
Balance at close of year	149
All Other [Member] | Lexington Commerce Center - Eagan, MN [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				1,399
Initial Cost to Company [Abstract]
Land				453
Buildings & Improvements				4,352
Costs capitalized subsequent to acquisition				2,101
Gross amount at which carried at close of period [Abstract]
Land				512
Buildings & Improvements				6,394
Total	6,906			6,906
Accumulated Depreciation	$ (3,209)			(3,209)
Date of Construction or Acquisition	1999
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 6,906
Deductions during year [Abstract]
Balance at close of year	3,209
All Other [Member] | Minot 1400 31st Ave - Minot, ND [Member]
Initial Cost to Company [Abstract]
Land				1,026
Buildings & Improvements				6,143
Costs capitalized subsequent to acquisition				4,404
Gross amount at which carried at close of period [Abstract]
Land				1,038
Buildings & Improvements				10,535
Total	11,573			11,573
Accumulated Depreciation	$ (3,521)			(3,521)
Date of Construction or Acquisition	2010
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 11,573
Deductions during year [Abstract]
Balance at close of year	3,521
All Other [Member] | Minot 2505 16th Street SW - Minot, ND [Member]
Initial Cost to Company [Abstract]
Land				298
Buildings & Improvements				1,724
Costs capitalized subsequent to acquisition				296
Gross amount at which carried at close of period [Abstract]
Land				298
Buildings & Improvements				2,020
Total	2,318			2,318
Accumulated Depreciation	$ (427)			(427)
Date of Construction or Acquisition	2009
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 2,318
Deductions during year [Abstract]
Balance at close of year	427
All Other [Member] | Minot Arrowhead - Minot, ND [Member]
Initial Cost to Company [Abstract]
Land				100
Buildings & Improvements				3,216
Costs capitalized subsequent to acquisition				5,583
Gross amount at which carried at close of period [Abstract]
Land				176
Buildings & Improvements				8,723
Total	8,899			8,899
Accumulated Depreciation	$ (2,740)			(2,740)
Date of Construction or Acquisition	1973
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 8,899
Deductions during year [Abstract]
Balance at close of year	2,740
All Other [Member] | Minot IPS - Minot, ND [Member]
Initial Cost to Company [Abstract]
Land				416
Buildings & Improvements				5,952
Gross amount at which carried at close of period [Abstract]
Land				416
Buildings & Improvements				5,952
Total	6,368			6,368
Accumulated Depreciation	$ (699)			(699)
Date of Construction or Acquisition	2012
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 6,368
Deductions during year [Abstract]
Balance at close of year	699
All Other [Member] | Minot Southgate Retail - Minot, ND [Member]
Initial Cost to Company [Abstract]
Land				889
Buildings & Improvements				1,748
Costs capitalized subsequent to acquisition				68
Gross amount at which carried at close of period [Abstract]
Land				889
Buildings & Improvements				1,816
Total	2,705			2,705
Accumulated Depreciation	$ (74)			(74)
Date of Construction or Acquisition	2015
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 2,705
Deductions during year [Abstract]
Balance at close of year	74
All Other [Member] | Plaza 16 - Minot, ND [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				6,726
Initial Cost to Company [Abstract]
Land				389
Buildings & Improvements				5,444
Costs capitalized subsequent to acquisition				3,764
Gross amount at which carried at close of period [Abstract]
Land				598
Buildings & Improvements				8,999
Total	9,597			9,597
Accumulated Depreciation	$ (2,675)			(2,675)
Date of Construction or Acquisition	2009
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 9,597
Deductions during year [Abstract]
Balance at close of year	2,675
All Other [Member] | Roseville 3075 Long Lake Road - Roseville, MN [Member]
Initial Cost to Company [Abstract]
Land				810
Buildings & Improvements				10,244
Costs capitalized subsequent to acquisition				2,045
Gross amount at which carried at close of period [Abstract]
Land				810
Buildings & Improvements				12,289
Total	13,099			13,099
Accumulated Depreciation	$ (1,043)			(1,043)
Date of Construction or Acquisition	2001
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 13,099
Deductions during year [Abstract]
Balance at close of year	1,043
All Other [Member] | Urbandale 3900 106th Street - Urbandale, IA [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				10,102
Initial Cost to Company [Abstract]
Land				3,680
Buildings & Improvements				9,893
Costs capitalized subsequent to acquisition				1,982
Gross amount at which carried at close of period [Abstract]
Land				3,863
Buildings & Improvements				11,692
Total	15,555			15,555
Accumulated Depreciation	$ (3,347)			(3,347)
Date of Construction or Acquisition	2007
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 15,555
Deductions during year [Abstract]
Balance at close of year	3,347
All Other [Member] | Woodbury 1865 Woodlane - Woodbury, MN [Member]
Initial Cost to Company [Abstract]
Land				1,108
Buildings & Improvements				2,628
Costs capitalized subsequent to acquisition				2,063
Gross amount at which carried at close of period [Abstract]
Land				1,302
Buildings & Improvements				4,497
Total	5,799			5,799
Accumulated Depreciation	$ (1,294)			(1,294)
Date of Construction or Acquisition	2007
Life on which depreciation in latest income statement is computed	40 years
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	$ 5,799
Deductions during year [Abstract]
Balance at close of year	1,294
All Other [Member] | Wholly Owned Properties [Member]
Reconciliations of total real estate carrying value [Abstract]
Additions		$ 2,623	$ 12,223
Subtotal [Member]
Real Estate And Accumulated Depreciation [Abstract]
Encumbrances				665,338
Initial Cost to Company [Abstract]
Land				115,144
Buildings & Improvements				1,307,790
Costs capitalized subsequent to acquisition				254,547
Gross amount at which carried at close of period [Abstract]
Land				136,365
Buildings & Improvements				1,541,116
Total	1,677,481			1,677,481
Accumulated Depreciation	(340,417)			$ (340,417)
Reconciliations of total real estate carrying value [Abstract]
Balance at close of year	1,677,481
Deductions during year [Abstract]
Balance at close of year	$ 340,417