ACQUISITIONS AND DISPOSITIONS (Details) (USD $)	6 Months Ended
	Oct. 31, 2012		Oct. 31, 2011
Significant Acquisitions and Disposals [Line Items]
Transaction costs expensed during the period	$ 97,000,000		$ 426,000,000
Acquisitions and development projects placed in service [Abstract]
Land	5,985,000		5,666,000
Buildings	51,892,000		43,211,000
Intangible assets	813,000		3,744,000
Acquisition costs	58,690,000		52,621,000
Results of operations from acquired properties [Abstract]
Total revenue	2,929,000		933,000
Net income	(135,000)		117,000
Dispositions [Abstract]
Sales price	8,223,000
Book value and sales cost	5,543,000
Gain/(Loss)	2,680,000
Multi-Family Residential [Member]
Acquisitions and development projects placed in service [Abstract]
Land	4,715,000		2,069,000
Buildings	51,892,000		15,831,000
Intangible assets	813,000		0
Acquisition costs	57,420,000		17,900,000
Number of apartment units	4,580
Dispositions [Abstract]
Sales price	6,900,000
Book value and sales cost	4,094,000
Gain/(Loss)	2,806,000
Commercial Retail [Member]
Dispositions [Abstract]
Sales price			2,175,000
Book value and sales cost			1,586,000
Gain/(Loss)			589,000
Commercial Medical [Member]
Acquisitions and development projects placed in service [Abstract]
Land			3,181,000
Buildings			27,380,000
Intangible assets			3,744,000
Acquisition costs			34,305,000
Unimproved Land [Member]
Acquisitions and development projects placed in service [Abstract]
Land	1,270,000
Buildings	0
Intangible assets	0
Acquisition costs	1,270,000
Other Disposition [Member]
Dispositions [Abstract]
Sales price	698,000
Book value and sales cost	757,000
Gain/(Loss)	(59,000)
Villa West - Topeka, KS [Member]
Significant Acquisitions and Disposals [Line Items]
Area of land (in acres)	18.3
Cash paid for acquisition of property	5,200,000
Assumed debt	12,500,000
Villa West - Topeka, KS [Member] | Multi-Family Residential [Member]
Acquisitions and development projects placed in service [Abstract]
Date acquired	May 08, 2012
Land	1,590,000
Buildings	15,760,000
Intangible assets	300,000
Acquisition costs	17,650,000
Number of apartment units	308
Colony - Lincoln, NE [Member]
Significant Acquisitions and Disposals [Line Items]
Area of land (in acres)	14.7
Cash paid for acquisition of property	14,200,000
Noncontrolling Interest in Operating Partnerships	3,300,000
Colony - Lincoln, NE [Member] | Multi-Family Residential [Member]
Acquisitions and development projects placed in service [Abstract]
Date acquired	Jun. 04, 2012
Land	1,515,000
Buildings	15,731,000
Intangible assets	254,000
Acquisition costs	17,500,000
Number of apartment units	232
Lakeside Village - Lincoln, NE [Member]
Significant Acquisitions and Disposals [Line Items]
Area of land (in acres)	11.5
Cash paid for acquisition of property	13,800,000
Noncontrolling Interest in Operating Partnerships	3,500,000
Lakeside Village - Lincoln, NE [Member] | Multi-Family Residential [Member]
Acquisitions and development projects placed in service [Abstract]
Date acquired	Jun. 04, 2012
Land	1,215,000
Buildings	15,837,000
Intangible assets	198,000
Acquisition costs	17,250,000
Number of apartment units	208
The Ponds at Heritage Place - Sartell, MN [Member]
Significant Acquisitions and Disposals [Line Items]
Area of land (in acres)	6.5
Cash paid for acquisition of property	3,300,000
Noncontrolling Interest in Operating Partnerships	1,700,000
The Ponds at Heritage Place - Sartell, MN [Member] | Multi-Family Residential [Member]
Acquisitions and development projects placed in service [Abstract]
Date acquired	Oct. 10, 2012
Land	395,000
Buildings	4,564,000
Intangible assets	61,000
Acquisition costs	5,020,000
Number of apartment units	58
University Commons - Williston, ND [Member] | Unimproved Land [Member]
Acquisitions and development projects placed in service [Abstract]
Date acquired	Aug. 01, 2012
Land	823,000
Buildings	0
Intangible assets	0
Acquisition costs	823,000
Cypress Court - St. Cloud, MN [Member]
Significant Acquisitions and Disposals [Line Items]
Area of land (in acres)	3.8
Cash paid for acquisition of property	447,000
Cypress Court - St. Cloud, MN [Member] | Unimproved Land [Member]
Acquisitions and development projects placed in service [Abstract]
Date acquired	Aug. 10, 2012
Land	447,000
Buildings	0
Intangible assets	0
Acquisition costs	447,000
Williston Garden Buildings 3 and 4 - Williston, ND [Member]
Significant Acquisitions and Disposals [Line Items]
Area of land (in acres)	2.6
Cash paid for acquisition of property	822,500
Interest in joint venture (in hundredths)	60.00%
Number of buildings	4
Kentwood Thomasville - Kentwood, MI [Member] | Commercial Retail [Member]
Acquisitions and development projects placed in service [Abstract]
Area of a real estate property (in square feet)	16,080
Dispositions [Abstract]
Sales price	625,000
Book value and sales cost	692,000
Gain/(Loss)	(67,000)
Area of a real estate property (in square feet)	16,080
Regency Park Estates - St. Cloud, MN [Member] | Multi-Family Residential [Member]
Acquisitions and development projects placed in service [Abstract]
Date acquired			Aug. 01, 2012
Land			702,000
Buildings			10,198,000
Intangible assets			0
Acquisition costs			10,900,000
Number of apartment units			147
Cottage West Twin Homes - Sioux Falls, SD [Member] | Multi-Family Residential [Member]
Acquisitions and development projects placed in service [Abstract]
Date acquired			Oct. 12, 2012
Land			1,005,000
Buildings			3,725,000
Intangible assets			0
Acquisition costs			4,730,000
Number of apartment units			50
Gables Townhomes - Sioux Falls, SD [Member] | Multi-Family Residential [Member]
Acquisitions and development projects placed in service [Abstract]
Date acquired			Oct. 12, 2011
Land			362,000
Buildings			1,908,000
Intangible assets			0
Acquisition costs			2,270,000
Number of apartment units			24
Spring Creek American Falls - American Falls, ID [Member] | Commercial Medical [Member]
Acquisitions and development projects placed in service [Abstract]
Date acquired			Sep. 01, 2011
Land			137,000
Buildings			3,409,000
Intangible assets			524,000
Acquisition costs			4,070,000
Area of a real estate property (in square feet)			17,273
Dispositions [Abstract]
Area of a real estate property (in square feet)			17,273
Spring Creek Soda Springs - Soda Springs, ID [Member] | Commercial Medical [Member]
Acquisitions and development projects placed in service [Abstract]
Date acquired			Sep. 01, 2012
Land			66,000
Buildings			2,122,000
Intangible assets			42,000
Acquisition costs			2,230,000
Area of a real estate property (in square feet)			15,571
Dispositions [Abstract]
Area of a real estate property (in square feet)			15,571
Spring Creek Eagle - Eagle, ID [Member] | Commercial Medical [Member]
Acquisitions and development projects placed in service [Abstract]
Date acquired			Sep. 01, 2011
Land			250,000
Buildings			3,191,000
Intangible assets			659,000
Acquisition costs			4,100,000
Area of a real estate property (in square feet)			15,559
Dispositions [Abstract]
Area of a real estate property (in square feet)			15,559
Spring Creek Meridian - Meridian, ID [Member] | Commercial Medical [Member]
Acquisitions and development projects placed in service [Abstract]
Date acquired			Sep. 01, 2011
Land			428,000
Buildings			5,499,000
Intangible assets			1,323,000
Acquisition costs			7,250,000
Area of a real estate property (in square feet)			31,820
Dispositions [Abstract]
Area of a real estate property (in square feet)			31,820
Spring Creek Overland - Boise, ID [Member] | Commercial Medical [Member]
Acquisitions and development projects placed in service [Abstract]
Date acquired			Sep. 01, 2011
Land			656,000
Buildings			5,001,000
Intangible assets			1,068,000
Acquisition costs			6,725,000
Area of a real estate property (in square feet)			26,605
Dispositions [Abstract]
Area of a real estate property (in square feet)			26,605
Spring Creek Boise - Boise, ID [Member] | Commercial Medical [Member]
Acquisitions and development projects placed in service [Abstract]
Date acquired			Sep. 01, 2011
Land			711,000
Buildings			4,236,000
Intangible assets			128,000
Acquisition costs			5,075,000
Area of a real estate property (in square feet)			16,311
Dispositions [Abstract]
Area of a real estate property (in square feet)			16,311
Spring Creek Ustick - Meridian, ID [Member] | Commercial Medical [Member]
Acquisitions and development projects placed in service [Abstract]
Date acquired			Sep. 01, 2011
Land			467,000
Buildings			3,833,000
Intangible assets			0
Acquisition costs			4,300,000
Area of a real estate property (in square feet)			26,605
Dispositions [Abstract]
Area of a real estate property (in square feet)			26,605
Edina 6525 Drew Ave S - Edina, MN [Member] | Commercial Medical [Member]
Acquisitions and development projects placed in service [Abstract]
Date acquired			Oct. 13, 2011
Land			416,000
Buildings			89,000
Intangible assets			0
Acquisition costs			505,000
Area of a real estate property (in square feet)			3,431
Dispositions [Abstract]
Area of a real estate property (in square feet)			3,431
Industrial-Office Build-to-Suit - Minot, ND [Member] | Unimproved Land [Member]
Acquisitions and development projects placed in service [Abstract]
Date acquired			Sep. 07, 2011
Land			416,000
Buildings			0
Intangible assets			0
Acquisition costs			416,000
Terrace on the Green - Fargo, ND [Member] | Multi-Family Residential [Member]
Acquisitions and development projects placed in service [Abstract]
Number of apartment units	116
Dispositions [Abstract]
Sales price	3,450,000
Book value and sales cost	1,248,000
Gain/(Loss)	2,202,000
Prairiewood Meadows - Fargo, ND [Member] | Multi-Family Residential [Member]
Acquisitions and development projects placed in service [Abstract]
Number of apartment units	85
Dispositions [Abstract]
Sales price	3,450,000
Book value and sales cost	2,846,000
Gain/(Loss)	604,000
Meadow Wind Land - Casper, WY [Member] | Commercial Medical [Member]
Acquisitions and development projects placed in service [Abstract]
Date acquired			Sep. 01, 2011
Land			50,000
Buildings			0
Intangible assets			0
Acquisition costs			50,000
Georgetown Square Condominiums 5 and 6 [Member] | Other Disposition [Member]
Dispositions [Abstract]
Sales price			330,000
Book value and sales cost			336,000
Gain/(Loss)			(6,000)
Georgetown Square Condominiums 3 and 4 [Member] | Other Disposition [Member]
Dispositions [Abstract]
Sales price	368,000
Book value and sales cost	421,000
Gain/(Loss)	(53,000)
Livingstone Pamida - Livingston, MT [Member]
Dispositions [Abstract]
Sale proceeds applied to pay off the outstanding mortgage loan	1,200,000
Sales price	2,200,000
Livingstone Pamida - Livingston, MT [Member] | Commercial Retail [Member]
Acquisitions and development projects placed in service [Abstract]
Area of a real estate property (in square feet)			41,200
Dispositions [Abstract]
Sales price			2,175,000
Book value and sales cost			1,586,000
Gain/(Loss)			589,000
Area of a real estate property (in square feet)			41,200
Sioux Falls, South Dakota [Member]
Significant Acquisitions and Disposals [Line Items]
Number of property acquired	2
Housing projects in Boise, Idaho and towns surrounding Boise [Member]
Significant Acquisitions and Disposals [Line Items]
Number of property acquired	7
Minot, North Dakota and Casper, Wyoming [Member]
Significant Acquisitions and Disposals [Line Items]
Number of property acquired	2
Medical clinic in Minot, North Dakota [Member]
Significant Acquisitions and Disposals [Line Items]
Area of property acquired (in square foot)	25,000
Buffalo Mall property in Jamestown, North Dakota [Member]
Significant Acquisitions and Disposals [Line Items]
Number of screen movie theater constructed	6
Acquisitions and development projects placed in service [Abstract]
Acquisition costs	2,200,000
Condominium Units [Member]
Dispositions [Abstract]
Number of properties sold	2
Multi-family Residential Properties [Member]
Dispositions [Abstract]
Number of properties sold	2
Number of properties, debt assumed by the buyer	2
Debt assumed by Buyer	4,600,000
Development Projects Placed in Service [Member]
Acquisitions and development projects placed in service [Abstract]
Land	0		0
Buildings	11,477,000		5,660,000
Intangible assets	0		0
Acquisition costs	11,477,000		5,660,000
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 acquired	Jun. 29, 2012
Land	0
Buildings	4,591,000
Intangible assets	0
Acquisition costs	4,591,000
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 acquired	Jul. 31, 2012
Land	0
Buildings	6,886,000
Intangible assets	0
Acquisition costs	6,886,000
Number of apartment units	73	[2]
Development Projects Placed in Service [Member] | Jamestown Buffalo Mall - Jamestown, ND [Member] | Commercial Retail [Member]
Acquisitions and development projects placed in service [Abstract]
Date acquired			Jun. 15, 2011
Land			0
Buildings			781,000
Intangible assets			0
Acquisition costs			781,000
Area of a real estate property (in square feet)			19,037	[3]
Dispositions [Abstract]
Area of a real estate property (in square feet)			19,037	[3]
Development Projects Placed in Service [Member] | Trinity at Plaza 16 - Minot, ND( [Member] | Commercial Medical [Member]
Acquisitions and development projects placed in service [Abstract]
Date acquired			Sep. 23, 2011
Land			0
Buildings			4,879,000
Intangible assets			0
Acquisition costs			$ 4,879,000
Area of a real estate property (in square feet)			24,795	[4]
Dispositions [Abstract]
Area of a real estate property (in square feet)			24,795	[4]

[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 October 31, 2012 of $17.6 million.

[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 October 31, 2012 of $18.9 million.

[3] Construction project placed in service June 15, 2011. Additional costs paid in fiscal year 2011 totaled $1.4 million, for a total project cost at October 31, 2011 of $2.2 million.

[4] Development property placed in service September 23, 2011. Additional costs paid in fiscal year 2011 totaled $3.3 million, for a total project cost at October 31, 2011 of $8.2 million.