EQUITY (Details) (USD $)	3 Months Ended		9 Months Ended
	Jan. 31, 2015	Jan. 31, 2014	Jan. 31, 2015	Jan. 31, 2014
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Aggregate gross sales price of common shares of beneficial interest allowed to be sold			$ 75,000,000
Units converted to common shares (in shares)	333,000	37,000	6,700,000	197,000
Units converted to common shares	811,000	185,000	38,500,000	1,100,000
2008 Incentive Award Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Shares issued (in shares)			204,000	13,000
Shares issued			1,900,000	112,000
Restricted shares related to 2008 Incentive Award Plan			105,000
Distribution Reinvestment and Share Purchase Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Shares registered under Distribution Reinvestment and Share Purchase Plan (in shares)			10,000,000
Shares issued (in shares)	2,000,000	1,300,000	6,200,000	5,200,000
Shares issued	16,100,000	11,100,000	34,800,000	44,200,000
Average price of shares issued (in dollars per share)	$ 8.06	$ 8.27	$ 8.20	$ 8.43
Distribution Reinvestment Waiver [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Shares issued (in shares)			926,000,000	1,400,000
Shares issued			$ 8,000,000	$ 12,000,000
Average price of shares issued (in dollars per share)			$ 8.64	$ 8.88