ACQUISITIONS, DEVELOPMENT PROJECTS PLACED IN SERVICE AND DISPOSITIONS, PROPERTY DISPOSITIONS (Details) $ in Thousands	3 Months Ended
	Jul. 31, 2016 USD ($) ft² property	Jul. 31, 2015 USD ($) ft² property
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale price	$ 13,650	$ 7,000
Book value and sales cost	4,692	7,175
Gain/(Loss)	$ 8,958	$ (175)
Other [Member] | Stone Container - Fargo, ND [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Date disposed	Jul. 25, 2016
Sale price	$ 13,400
Book value and sales cost	4,418
Gain/(Loss)	$ 8,982
Area of real estate property | ft²	195,075
Other [Member] | 117,144 sq ft Thresher Square - Minneapolis, MN [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Date disposed		May 18, 2015
Sale price		$ 7,000
Book value and sales cost		7,175
Gain/(Loss)		$ (175)
Area of real estate property | ft²		117,144
Commercial Properties [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold | property	1	1
Unimproved Land [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold | property	1
Unimproved Land [Member] | Georgetown Square - Grand Chute, WI [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Date disposed	May 06, 2016
Sale price	$ 250
Book value and sales cost	274
Gain/(Loss)	$ (24)