BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Details) (USD $)	9 Months Ended			3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended												9 Months Ended
	Jan. 31, 2013	Jan. 31, 2012	Apr. 30, 2012	Jan. 31, 2013 Acquired below-market leases and acquired above-market leases [Member]	Jan. 31, 2012 Acquired below-market leases and acquired above-market leases [Member]	Jan. 31, 2013 Acquired below-market leases and acquired above-market leases [Member]	Jan. 31, 2012 Acquired below-market leases and acquired above-market leases [Member]	Jan. 31, 2013 Other identified intangible assets [Member]	Jan. 31, 2012 Other identified intangible assets [Member]	Jan. 31, 2013 Other identified intangible assets [Member]	Jan. 31, 2012 Other identified intangible assets [Member]	Jan. 31, 2013 Dacotah Bank, Minot, North Dakota [Member]	Jan. 31, 2013 United Community Bank, Minot, North Dakota [Member]	Jan. 31, 2013 Commerce Bank, A Minnesota Banking Corporation [Member]	Jan. 31, 2013 First International Bank, Watford City, North Dakota [Member]	Jan. 31, 2013 Peoples State Bank of Velva, North Dakota [Member]	Jan. 31, 2013 Equity Bank, Minnetonka, Minnesota [Member]	Jan. 31, 2013 Associated Bank, Green Bay, Wisconsin [Member]	Jan. 31, 2013 Venture Bank, Eagan, Minnesota [Member]	Jan. 31, 2013 American National Bank, Omaha, Nebraska [Member]	Jan. 31, 2013 United Community Bank and Equity Bank [Member]	Jan. 31, 2013 Kentwood property [Member]	Jan. 31, 2012 Kentwood property [Member]
BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES [Abstract]
Interest in common units in operating partnership (in hundredths)	81.50%		81.50%
Redemption basis	one-for-one
Redemptions by limited partner, maximum	2
Number of units to redeem, minimum (in units)	1,000
Period to hold the beneficial interest, minimum	1 year
Real Estate Properties [Line Items]
Impairment of retail property	$ 0	$ 135,000																					$ 128,000
Goodwill impairment																						7,000
Compensating Balances [Line Items]
Compensating balances	8,900,000											350,000	275,000	250,000	6,100,000	225,000	300,000	500,000	500,000	400,000	638,000
Decrease in lender holdbacks	1,514,000	5,056,000
Increase in lender holdbacks	1,962,000	315,000
IDENTIFIED INTANGIBLE ASSETS AND INTANGIBLE LIABILITIES AND GOODWILL [Abstract]
Finite-lived Intangible Assets Acquired	813,000	416,000
Weighted average lives of intangible assets and intangible liabilities	6 months	10 years
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross, Total	67,608,000		92,401,000
Finite-Lived Intangible Assets, Accumulated Amortization	(26,599,000)		(47,813,000)
Finite-Lived Intangible Assets, Net, Total	41,009,000		44,588,000
Indentified intangible liabilities, gross	391,000		1,104,000
Indentified intangible liabilities, accumulated amortization	(288,000)		(967,000)
Indentified intangible liabilities, net	103,000		137,000
Amortization of Intangible Assets				(7,000)	(8,000)	(21,000)	(40,000)	1,200,000	1,200,000	4,300,000	4,400,000
Estimated annual amortization [Abstract]
2014				37,000		37,000		4,146,000		4,146,000
2015				18,000		18,000		3,825,000		3,825,000
2016				14,000		14,000		3,608,000		3,608,000
2017				6,000		6,000		3,139,000		3,139,000
2018				(5,000)		(5,000)		2,652,000		2,652,000
Goodwill	1,106,000		1,120,000
Goodwill impairment																						7,000
Goodwill derecognized	14,000
RECLASSIFICATIONS [Abstract]
Number of multi-family residential properties sold	2
INVOLUNTARY CONVERSION OF ASSETS [Abstract]
Number of 32-unit buildings	2
Expensed flood and fire insurance deductibles	400,000
Deductible amount for losses to be covered under insurance policy		200,000
Insurance proceeds received for flood clean up costs and redevelopment			5,700,000
Estimated gain on involuntary conversion	2,300,000	274,000
Insurance proceeds received for redevelopment	2,900,000
Insurance proceeds received for business interruption from the flood and fire	409,000
Insurance proceeds received for total business interruption proceeds	666,000
Insurance claim on total business interruption	$ 1,100,000