BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES, GOODWILL AND INTANGIBLES (Details)	3 Months Ended
	Jul. 31, 2015 USD ($) Property	Jul. 31, 2014 USD ($)	Apr. 30, 2015 USD ($)
IDENTIFIED INTANGIBLE ASSETS AND INTANGIBLE LIABILITIES AND GOODWILL [Abstract]
New intangible assets	$ 0	$ 265,000
Addition to intangible liabilities	$ 0	$ 0
Weighted average lives of intangible assets and intangible liabilities		6 months
Identified intangible assets (included in intangible assets) [Abstract]
Gross carrying amount	$ 45,822,000		$ 45,823,000
Accumulated amortization	(20,643,000)		(19,610,000)
Net carrying amount	25,179,000		26,213,000
Identified intangible liabilities (included in other liabilities) [Abstract]
Gross carrying amount	82,000		82,000
Accumulated amortization	(63,000)		(61,000)
Net carrying amount	19,000		21,000
Estimated annual amortization [Abstract]
Goodwill book value	1,718,000		1,718,000
Goodwill recognized	0	$ 852,000
Held-for-Sale Properties [Member]
Estimated annual amortization [Abstract]
Goodwill book value	$ 193,000		193,000
Office Properties [Member]
Real Estate Properties [Line Items]
Number of real estate properties classified as held for sale | Property	48
Number of real estate properties classified as held for sale in discontinued operations | Property	48
Retail Properties [Member]
Real Estate Properties [Line Items]
Number of real estate properties classified as held for sale | Property	17
Number of real estate properties classified as held for sale in discontinued operations | Property	17
Healthcare Properties [Member]
Real Estate Properties [Line Items]
Number of real estate properties classified as held for sale | Property	2
Number of real estate properties classified as held for sale in discontinued operations | Property	1
Acquired below-market leases and acquired above-market leases [Member]
Identified intangible liabilities (included in other liabilities) [Abstract]
Amortization of intangible assets	$ 6,000	6,000
Estimated annual amortization [Abstract]
2017			11,000,000
2018			(3,000,000)
2019			(3,000,000)
2020			(1,000,000)
2021			0
Other identified intangible assets [Member]
Identified intangible liabilities (included in other liabilities) [Abstract]
Amortization of intangible assets	$ 1,000,000	$ 1,200,000
Estimated annual amortization [Abstract]
2017			3,698,000
2018			3,469,000
2019			3,433,000
2020			3,390,000
2021			$ 3,268,000