BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Details) (USD $)	3 Months Ended
	Jul. 31, 2013	Jul. 31, 2012	Apr. 30, 2013
BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES [Abstract]
Interest in common units in operating partnership (in hundredths)	82.70%		82.40%
Redemption basis	one-for-one
Redemptions by limited partner, maximum	2
Number of units to redeem, minimum (in units)	1,000
Real Estate Properties [Line Items]
Impairment of retail property	$ 1,803,000	$ 0
Compensating Balances [Line Items]
Compensating balances	8,400,000
Decrease in lender holdbacks	1,144,000	624,000
Increase in lender holdbacks	279,000	1,403,000
IDENTIFIED INTANGIBLE ASSETS AND INTANGIBLE LIABILITIES AND GOODWILL [Abstract]
Finite-lived Intangible Assets Acquired	362,000	752,000
Weighted average lives of intangible assets and intangible liabilities	6 months	6 months
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross, Total	61,008,000		68,165,000
Finite-Lived Intangible Assets, Accumulated Amortization	(24,019,000)		(27,708,000)
Finite-Lived Intangible Assets, Net, Total	36,989,000		40,457,000
Indentified intangible liabilities, gross	327,000		391,000
Indentified intangible liabilities, accumulated amortization	(249,000)		(296,000)
Indentified intangible liabilities, net	78,000		95,000
Estimated annual amortization [Abstract]
Goodwill	1,100,000		1,106,000
Goodwill derecognized	7,000
INVOLUNTARY CONVERSION OF ASSETS [Abstract]
Number of 32-unit buildings	2
Insurance proceeds received for business interruption from the flood and fire	966,000
Insurance proceeds received for total business interruption proceeds	966,000
PROCEEDS FROM FINANCING LIABILITY [Abstract]
Proceeds from sale of non-core assisted living property	7,900,000
Amount of deed contract	29,000,000
Variable Interest Entity [Line Items]
Estimated total costs of joint venture project	52,200,000
Percentage of project financed with third-party debt in joint venture (in hundredths)	69.00%
Percentage of project financed with IRET in joint venture (in hudnredths)	7.00%
IRET [Member]
Variable Interest Entity [Line Items]
Percentage of ownership in VIE (in hundredths)	51.00%
Real Estate Development Company [Member]
Variable Interest Entity [Line Items]
Percentage of ownership in VIE (in hundredths)	49.00%
Acquired below-market leases and acquired above-market leases [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization of Intangible Assets	(10,000)	(10,000)
Estimated annual amortization [Abstract]
2015	21,000
2016	17,000
2017	9,000
2018	(5,000)
2019	(5,000)
Other identified intangible assets [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization of Intangible Assets	3,600,000	1,500,000
Estimated annual amortization [Abstract]
2015	4,830,000
2016	4,612,000
2017	4,143,000
2018	3,701,000
2019	3,549,000
Dacotah Bank, Minot, North Dakota [Member]
Compensating Balances [Line Items]
Compensating balances	350,000
United Community Bank, Minot, North Dakota [Member]
Compensating Balances [Line Items]
Compensating balances	275,000
Commerce Bank, A Minnesota Banking Corporation [Member]
Compensating Balances [Line Items]
Compensating balances	250,000
First International Bank, Watford City, North Dakota [Member]
Compensating Balances [Line Items]
Compensating balances	6,100,000
Peoples State Bank of Velva, North Dakota [Member]
Compensating Balances [Line Items]
Compensating balances	225,000
Equity Bank, Minnetonka, Minnesota [Member]
Compensating Balances [Line Items]
Compensating balances	300,000
Associated Bank, Green Bay, Wisconsin [Member]
Compensating Balances [Line Items]
Compensating balances	500,000
American National Bank, Omaha, Nebraska [Member]
Compensating Balances [Line Items]
Compensating balances	400,000
United Community Bank and Equity Bank [Member]
Compensating Balances [Line Items]
Compensating balances	640,000
Anoka, Minnesota [Member]
Real Estate Properties [Line Items]
Impairment of retail property	265,000
Bloomington, Minnesota [Member]
Real Estate Properties [Line Items]
Impairment of retail property	329,000
Clive, Iowa [Member]
Real Estate Properties [Line Items]
Impairment of retail property	345,000
St. Louis Park, Minnesota [Member]
Real Estate Properties [Line Items]
Impairment of retail property	$ 864,000