MORTGAGES PAYABLE AND LINE OF CREDIT (Details) (USD $)	6 Months Ended
	Oct. 31, 2012	Apr. 30, 2012
MORTGAGES PAYABLE AND LINE OF CREDIT [Abstract]
Interest rates on mortgages payable range, minimum (in hundredths)	3.32%
Interest rates on mortgages payable range, maximum (in hundredths)	8.25%
Mortgages maturity date range, end	Jul. 01, 2036
Fixed rate mortgages	$ 1,000,000,000	$ 1,000,000,000
Variable rate mortgages	23,500,000	16,200,000
Weighted average rate of interest on mortgage debt (in hundredths)	566.00%	578.00%
Aggregate amount of required future principal payments on mortgages payable [Abstract]
2013 (remainder)	25,851,000
2014	65,375,000
2015	112,475,000
2016	91,788,000
2017	197,488,000
Thereafter	552,220,000
Total payments	1,045,197,000	1,048,689,000
Lending commitments	60,000,000
Number of properties securing line of credit	23
Line of credit, current interest rate (in hundredths)	515.00%
Line of credit, minimum outstanding principal balance	10,000,000
Minimum depository accounts	6,000,000
Non-interest bearing account	$ 1,500,000