ACQUISITIONS AND DISPOSITIONS (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Jul. 31, 2013	Jul. 31, 2012
Acquisitions and development projects placed in service [Abstract]
Land	$ 466	$ 4,320
Buildings	5,551	47,328
Intangible assets	362	752
Acquisition costs	6,379	52,400
Results of operations from acquired properties [Abstract]
Total revenue	186	1,232
Net income	(108)	(72)
Dispositions [Abstract]
Sales price	21,785	955
Book value and sales cost	19,842	1,028
Gain/(Loss)	1,943	(73)
Commercial Industrial [Member]
Dispositions [Abstract]
Sales price	19,475
Book value and sales cost	17,422
Gain/(Loss)	2,053
Alps Park - Rapid City, SD [Member] | Multi-Family Residential [Member]
Acquisitions and development projects placed in service [Abstract]
Date Acquisition	May 01, 2013
Land	287
Buildings	5,551
Intangible assets	362
Acquisition costs	6,200
Number of apartment units	71
Bodycote - Eden Prairie, MN [Member] | Commercial Industrial [Member]
Dispositions [Abstract]
Date Disposal	May 13, 2013
Sales price	3,150
Book value and sales cost	1,375
Gain/(Loss)	1,775
Area of a real estate property (in square feet)	41,880
Chateau II - Minot, ND [Member] | Unimproved Land [Member]
Acquisitions and development projects placed in service [Abstract]
Date Acquisition	May 21, 2013
Land	179
Buildings	0
Intangible assets	0
Acquisition costs	179
Colony Lincoln, NE [Member] | Multi-Family Residential [Member]
Acquisitions and development projects placed in service [Abstract]
Date Acquisition		Jun. 04, 2012
Land		1,515
Buildings		15,731
Intangible assets		254
Acquisition costs		17,500
Number of apartment units		232
Fargo 1320 45th St. N - Fargo, ND [Member] | Commercial Industrial [Member]
Dispositions [Abstract]
Date Disposal	May 13, 2013
Sales price	4,700
Book value and sales cost	4,100
Gain/(Loss)	600
Area of a real estate property (in square feet)	42,244
Eagan - Eagan, MN [Member] | Commercial Retail [Member]
Dispositions [Abstract]
Date Disposal	May 14, 2013
Sales price	2,310
Book value and sales cost	2,420
Gain/(Loss)	(110)
Area of a real estate property (in square feet)	23,187
Georgetown Square Condominiums 5 and 6 [Member] | Other Disposition [Member]
Dispositions [Abstract]
Date Disposal		Jun. 21, 2012
Sales price		330
Book value and sales cost		336
Gain/(Loss)		(6)
Kentwood Thomasville Kentwood, MI [Member] | Commercial Retail [Member]
Dispositions [Abstract]
Date Disposal		Jun. 20, 2012
Sales price		625
Book value and sales cost		692
Gain/(Loss)		(67)
Area of a real estate property (in square feet)		16,080
Lakeside Village Lincoln, NE [Member] | Multi-Family Residential [Member]
Acquisitions and development projects placed in service [Abstract]
Date Acquisition		Jun. 04, 2012
Land		1,215
Buildings		15,837
Intangible assets		198
Acquisition costs		17,250
Number of apartment units		208
Metal Improvement - New Brighton, MN [Member] | Commercial Industrial [Member]
Dispositions [Abstract]
Date Disposal	May 13, 2013
Sales price	2,350
Book value and sales cost	1,949
Gain/(Loss)	401
Area of a real estate property (in square feet)	49,620
Roseville 2929 Long Lake Road - Roseville, MN [Member] | Commercial Industrial [Member]
Dispositions [Abstract]
Date Disposal	May 13, 2013
Sales price	9,275
Book value and sales cost	9,998
Gain/(Loss)	(723)
Area of a real estate property (in square feet)	172,057
Villa West Topeka, KS [Member] | Multi-Family Residential [Member]
Acquisitions and development projects placed in service [Abstract]
Date Acquisition		May 08, 2012
Land		1,590
Buildings		15,760
Intangible assets		300
Acquisition costs		17,650
Number of apartment units		308
Development Projects Placed in Service [Member]
Acquisitions and development projects placed in service [Abstract]
Land		0
Buildings		7,701
Intangible assets		0
Acquisition costs		7,701
Development Projects Placed in Service [Member] | Quarry Ridge II Rochester, MN [Member] | Multi-Family Residential [Member]
Acquisitions and development projects placed in service [Abstract]
Date Acquisition		Jun. 29, 2012	[1]
Land		0	[1]
Buildings		3,543	[1]
Intangible assets		0	[1]
Acquisition costs		3,543	[1]
Number of apartment units		159	[1]
Development Projects Placed in Service [Member] | Williston Garden Buildings 3 and 4 Williston, ND [Member] | Multi-Family Residential [Member]
Acquisitions and development projects placed in service [Abstract]
Date Acquisition		Jul. 31, 2012	[2]
Land		0	[2]
Buildings		4,158	[2]
Intangible assets		0	[2]
Acquisition costs		$ 4,158	[2]
Number of apartment units		73	[2]

[1] (1) Development property placed in service June 29, 2012. Additional costs paid in fiscal years 2012 and 2011, and land acquired in fiscal year 2007, totaled $13.0 million, for a total project cost at July 31, 2012 of $16.5 million.

[2] (2) Development property placed in service July 31, 2012. Buildings 1 and 2 were placed in service in fiscal year 2012. Additional costs paid in fiscal year 2012 totaled $12.0 million, for a total project cost at July 31, 2012 of $16.2 million.