BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Details) (USD $)	3 Months Ended	6 Months Ended
	Oct. 31, 2014	Oct. 31, 2014 Property Redemption	Oct. 31, 2013	Apr. 30, 2014
BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES [Abstract]
Interest in operating partnership (in hundredths)	89.10%	89.10%		83.80%
Redemption basis		one-for-one
Redemptions by limited partner, maximum		2
Number of units to redeem, minimum (in units)	1,000	1,000
Period to hold the beneficial interest, minimum		1 year
Real Estate Properties [Line Items]
Impairment of retail property		$ 5,565,000	$ 1,860,000
Impairment of retail property attributable to discontinued operations		0
Number of impaired properties		4
Held For Sale [Line Items]
Liabilities related to real estate held for sale	22,100,000	22,100,000
Compensating Balances [Line Items]
Compensating balances	10,700,000	10,700,000
Remaining terms of certificates of deposit	2 months
Decrease in lender holdbacks	4,840,000	4,840,000	1,610,000
Increase in lender holdbacks	621,000	621,000	562,000
Dacotah Bank, Minot, North Dakota [Member]
Compensating Balances [Line Items]
Compensating balances	350,000	350,000
Commerce Bank [Member]
Compensating Balances [Line Items]
Compensating balances	100,000	100,000
United Community Bank, Minot, North Dakota [Member]
Compensating Balances [Line Items]
Compensating balances	275,000	275,000
Bremer Bank [Member]
Compensating Balances [Line Items]
Compensating balances	650,000	650,000
First International Bank, Watford City, North Dakota [Member]
Compensating Balances [Line Items]
Compensating balances	6,100,000	6,100,000
Peoples State Bank of Velva, North Dakota [Member]
Compensating Balances [Line Items]
Compensating balances	225,000	225,000
Associated Bank, Green Bay, Wisconsin [Member]
Compensating Balances [Line Items]
Compensating balances	600,000	600,000
American National Bank, Omaha, Nebraska [Member]
Compensating Balances [Line Items]
Compensating balances	400,000	400,000
Private Bank [Member]
Compensating Balances [Line Items]
Compensating balances	2,000,000	2,000,000
United Community and Dacotah Bank [Member] | Other Investments [Member]
Compensating Balances [Line Items]
Certificates of deposit	329,000	329,000
Anoka, Minnesota [Member]
Real Estate Properties [Line Items]
Impairment of retail property		265,000
Number of impaired properties		1
Minneapolis, Minnesota, office property [Member]
Real Estate Properties [Line Items]
Impairment of retail property		1,800,000
Number of impaired properties		1
Kalispell, Montana, retail property [Member]
Real Estate Properties [Line Items]
Impairment of retail property		2,100,000
Number of impaired properties		1
Golden Valley, Minnesota, office property [Member]
Real Estate Properties [Line Items]
Impairment of retail property		183,000
Number of impaired properties		1
Bloomington, Minnesota [Member]
Real Estate Properties [Line Items]
Impairment of retail property		329,000
Number of impaired properties		1
Boise, Idaho, office property [Member]
Real Estate Properties [Line Items]
Impairment of retail property		1,400,000
Number of impaired properties		1
Clive, Iowa [Member]
Real Estate Properties [Line Items]
Impairment of retail property		402,000
Number of impaired properties		1
St. Louis Park, Minnesota [Member]
Real Estate Properties [Line Items]
Impairment of retail property		$ 864,000
Number of impaired properties		1