EQUITY (Details) (USD $)	3 Months Ended
	Jul. 31, 2012	Jul. 31, 2011	Jan. 20, 2012
Class of Stock [Line Items]
Aggregate public offering price, maximum	$ 150,000,000
Aggregate gross sales price of common shares of beneficial interest, maximum			100,000,000
Proceeds from Issuance of Common Stock	2,168,000	106,000
Common shares issued under 2008 Incentive Plan Award (in shares)	53,000	53,000
Value of common shares issued under 2008 Incentive Plan Award	398,000	443,000
Units converted to common shares (in shares)	89,000	109,000
Units converted to common shares	337,000	999,000
Shares issued	2,566,000	549,000
Continuous equity offering program [Member]
Class of Stock [Line Items]
Shares issued, shares (in shares)	300,000	0
Proceeds from Issuance of Common Stock	2,100,000
401(k) plan [Member]
Class of Stock [Line Items]
Shares issued, shares (in shares)	5,000	13,000
Shares issued	40,000	106,000
Distribution Reinvestment and Share Purchase Plan [Member]
Class of Stock [Line Items]
Shares issued, shares (in shares)	1,900,000	562,000
Shares issued	$ 14,500,000	$ 4,500,000