ORGANIZATION (Details) ft² in Millions	Apr. 30, 2017 ft² property item
Real Estate Properties [Line Items]
Percentage of ordinary taxable income that must be distributed to shareholders (in hundredths)	90.00%
Multi-family Residential Properties [Member]
Real Estate Properties [Line Items]
Number of real estate properties	87
Number of apartment units | item	12,885
Multi-family Residential Properties [Member] | Discontinued Operations, Held-for-sale [Member]
Real Estate Properties [Line Items]
Number of real estate properties	13
Number of apartment units | item	327
Commercial Properties [Member]
Real Estate Properties [Line Items]
Number of real estate properties	42
Net rentable area (in square feet) | ft²	2.6
Commercial Properties [Member] | Discontinued Operations, Held-for-sale [Member]
Real Estate Properties [Line Items]
Number of real estate properties	4