DISCONTINUED OPERATIONS (Details) (USD $)	3 Months Ended								12 Months Ended
	Apr. 30, 2013	Jan. 31, 2013	Oct. 31, 2012	Jul. 31, 2012	Apr. 30, 2012	Jan. 31, 2012	Oct. 31, 2011	Jul. 31, 2011	Apr. 30, 2013	Apr. 30, 2012	Apr. 30, 2011
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties classified as held for sale	0				8				0	8	0
REVENUE
Real estate rentals									$ 212,969,000	$ 196,149,000	$ 189,245,000
Tenant reimbursement									46,437,000	42,929,000	44,931,000
TOTAL REVENUE	67,011,000	65,976,000	64,689,000	61,730,000	59,932,000	60,291,000	59,946,000	58,909,000	259,406,000	239,078,000	234,176,000
EXPENSES
Depreciation/amortization related to real estate investments									61,996,000	56,426,000	55,080,000
Utilities									19,172,000	17,442,000	18,020,000
Maintenance									29,237,000	26,354,000	28,955,000
Real estate taxes									34,380,000	31,581,000	30,637,000
Insurance									3,927,000	3,502,000	2,256,000
Property management expenses									15,408,000	18,651,000	20,348,000
Other property expenses									1,008,000	(142,000)	665,000
Other expenses									2,173,000	1,898,000	1,747,000
Amortization related to non-real estate investments									3,274,000	3,216,000	2,679,000
Impairment of real estate investments									305,000	428,000	0
TOTAL EXPENSES									179,374,000	166,309,000	167,609,000
Operating income									85,116,000	73,043,000	66,567,000
Interest expense									(62,900,000)	(64,066,000)	(62,735,000)
Interest income									222,000	148,000	259,000
Other income									526,000	638,000	282,000
Gain on sale of discontinued operations									6,885,000	349,000	19,365,000
INCOME (LOSS) FROM DISCONTINUED OPERATIONS									7,008,000	(57,000)	19,978,000
Property Sale Data
Gain on sale of discontinued operations									6,885,000	349,000	19,365,000
Multi-Family Residential [Member]
REVENUE
TOTAL REVENUE									90,759,000	72,500,000	65,229,000
Commercial-Office [Member]
REVENUE
TOTAL REVENUE									77,162,000	74,334,000	77,747,000
Commercial-Healthcare [Member]
REVENUE
TOTAL REVENUE									61,975,000	64,511,000	64,879,000
Commercial-Industrial [Member]
REVENUE
TOTAL REVENUE									14,911,000	14,325,000	13,165,000
Commercial-Retail [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties classified as held for sale					1					1
REVENUE
TOTAL REVENUE									14,599,000	13,408,000	13,156,000
Multi Family Residential -Condominium Units [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties classified as held for sale					8					8
Discontinued Operations [Member]
REVENUE
Real estate rentals									1,818,000	2,852,000	9,056,000
Tenant reimbursement									1,000	62,000	112,000
TOTAL REVENUE									1,819,000	2,914,000	9,168,000
EXPENSES
Depreciation/amortization related to real estate investments									479,000	682,000	1,911,000
Utilities									67,000	225,000	776,000
Maintenance									132,000	246,000	993,000
Real estate taxes									78,000	196,000	853,000
Insurance									25,000	52,000	158,000
Property management expenses									115,000	272,000	1,047,000
Other property expenses									16,000	4,000	72,000
Other expenses									0	67,000	28,000
Amortization related to non-real estate investments									0	0	4,000
Impairment of real estate investments									0	428,000	0
TOTAL EXPENSES									912,000	2,172,000	5,842,000
Operating income									907,000	742,000	3,326,000
Interest expense									(786,000)	(1,164,000)	(2,718,000)
Interest income									0	0	5,000
Other income									2,000	16,000	0
Income (loss) from discontinued operations before gain on sale									123,000	(406,000)	613,000
Gain on sale of discontinued operations									6,885,000	349,000	19,365,000
INCOME (LOSS) FROM DISCONTINUED OPERATIONS									7,008,000	(57,000)	19,978,000
Property Sale Data
Sales price									26,273,000	3,237,000	83,330,000
Net book value and sales costs									(19,388,000)	(2,888,000)	(63,965,000)
Gain on sale of discontinued operations									6,885,000	349,000	19,365,000
Discontinued Operations [Member] | Multi-Family Residential [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold	3								3
EXPENSES
INCOME (LOSS) FROM DISCONTINUED OPERATIONS									3,653,000	161,000	19,268,000
Discontinued Operations [Member] | Commercial-Office [Member]
EXPENSES
INCOME (LOSS) FROM DISCONTINUED OPERATIONS									0	0	0
Discontinued Operations [Member] | Commercial-Healthcare [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold	1								1
EXPENSES
INCOME (LOSS) FROM DISCONTINUED OPERATIONS									3,419,000	(465,000)	(84,000)
Discontinued Operations [Member] | Commercial-Industrial [Member]
EXPENSES
INCOME (LOSS) FROM DISCONTINUED OPERATIONS									0	0	726,000
Discontinued Operations [Member] | Commercial-Retail [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold	1								1
EXPENSES
INCOME (LOSS) FROM DISCONTINUED OPERATIONS									$ (64,000)	$ 247,000	$ 68,000
Discontinued Operations [Member] | Multi Family Residential -Condominium Units [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold	4								4