COMMON AND PREFERRED SHARES OF BENEFICIAL INTEREST AND EQUITY (Details) (USD $)	12 Months Ended						3 Months Ended	12 Months Ended				12 Months Ended			12 Months Ended
	Apr. 30, 2014		Apr. 30, 2013		Apr. 30, 2012		Apr. 30, 2013 Common Stock [Member]	Apr. 30, 2014 Common Stock [Member]	Apr. 30, 2013 Common Stock [Member]	Apr. 30, 2013 Preferred Class A [Member]	Apr. 30, 2014 Preferred Class A [Member]	Apr. 30, 2013 Preferred Class B [Member]	Apr. 30, 2012 Preferred Class B [Member]	Apr. 30, 2014 Preferred Class B [Member]	Apr. 30, 2014 Distribution Reinvestment and Share Purchase Plan [Member]	Apr. 30, 2013 Distribution Reinvestment and Share Purchase Plan [Member]	Apr. 30, 2014 Distribution Reinvestment and Share Purchase Plan [Member] Voluntary cash contributions [Member]	Apr. 30, 2013 Distribution Reinvestment and Share Purchase Plan [Member] Voluntary cash contributions [Member]	Apr. 30, 2014 Distribution Reinvestment and Share Purchase Plan [Member] Reinvested distributions [Member]	Apr. 30, 2013 Distribution Reinvestment and Share Purchase Plan [Member] Reinvested distributions [Member]
Distribution Reinvestment and Share Purchase Plan [Abstract]
Shares issued (in shares)							6,000,000	0	300,000						6,600,000	5,300,000	4,800,000	3,800,000	1,800,000	1,500,000
Shares issued	$ 112,000	[1]	$ 55,846,000	[1]	$ 24,870,000	[1]									$ 55,800,000	$ 43,100,000	$ 41,200,000	$ 30,700,000	$ 14,600,000	$ 12,400,000
Discount rate on shares (in hundredths)	3.00%
Conversion of Units to Common Shares. [Abstract]
Units converted to common stock (in shares)	903,000		317,000
Units converted to common stock	4,400,000		1,600,000
Issuance of Common Shares [Abstract]
Offering price (in dollars per share)							9.25		7.24
Proceeds from issuance of common shares	0		55,433,000		24,413,000		53,000,000		2,100,000
Series A Cumulative Redeemable Preferred Shares of Beneficial Interest [Abstract]
Preferred shares issued (in shares)										1,150,000	1,150,000	4,600,000		4,600,000
Sale of stock, price per share (in dollars per share)										$ 25.00		$ 25.00
Proceeds from issuance of cumulative redeemable preferred shares										27,300,000		111,200,000
Preferred shares liquidation per annum (in dollars per share)										$ 2.0625		$ 1.9875
Distribution rate percentage (in hundredths)										8.25%		7.95%
Preferred shares liquidation (in dollars per share)										$ 25.00		$ 25.00
Preferred shares liquidation preference												115,000,000
Debt repaid with proceeds from stock issuance													34,500,000
Original outstanding borrowing under line of credit												44,500,000
Line of credit facility, amount outstanding	22,500,000		10,000,000									10,000,000
Unused capacity, line of credit												35,000,000
Aggregate offering price								$ 75,000,000

[1] (as revised)