EQUITY (Details) (USD $)	9 Months Ended
	Jan. 31, 2014	Jan. 31, 2013
Class of Stock [Line Items]
Shares registered under Distribution Reinvestment and Share Purchase Plan (in shares)	10,000,000
Proceeds from sale of common shares, net of issue costs	$ 0	$ 2,448,000
Aggregate gross sales price of common shares of beneficial interest allowed to be sold	75,000,000
Common shares issued under 2008 Incentive Plan Award (in shares)	13,000	53,000
Value of common shares issued under 2008 Incentive Plan Award	112,000	398,000
Units converted to common shares (in shares)	197,000	203,000
Units converted to common shares	1,100,000	846,000
Shares issued	112,000	2,846,000
Continuous equity offering program [Member]
Class of Stock [Line Items]
Shares issued	0
401(k) plan [Member]
Class of Stock [Line Items]
Shares issued, shares (in shares)		43,000
Shares issued		337,000
Distribution Reinvestment and Share Purchase Plan [Member]
Class of Stock [Line Items]
Shares issued, shares (in shares)	5,200,000	4,300,000
Shares issued	$ 44,200,000	$ 34,100,000
Average price of shares issued (in dollars per share)	$ 8.43	$ 7.90