CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) - USD ($)	Jul. 31, 2015	Apr. 30, 2015
Other assets
Intangible assets, accumulated amortization	$ 20,643,000	$ 19,610,000
Property and equipment, accumulated depreciation	1,482,000	1,464,000
Deferred charges and leasing costs, accumulated amortization	$ 8,301,000	$ 8,077,000
EQUITY
Common Shares of Beneficial Interest, no par value (in dollars per share)	$ 0	$ 0
Common Shares of Beneficial Interest, shares issued (in shares)	125,519,557	124,455,624
Common Shares of Beneficial Interest, shares outstanding (in shares)	125,519,557	124,455,624
Noncontrolling interests - Operating Partnership (in shares)	13,921,386	13,999,725
Receivable Arising from Straight-Lining of Rents [Member]
Other assets
Accounts receivable, allowance	$ 689,000	$ 718,000
Accounts Receivable [Member]
Other assets
Accounts receivable, allowance	$ 135,000	$ 438,000
Preferred Series A [Member]
EQUITY
Preferred Shares of Beneficial Interest, no par value (in dollars per share)	$ 0	$ 0
Preferred Shares of Beneficial Interest, shares issued (in shares)	1,150,000	1,150,000
Preferred Shares of Beneficial Interest, shares outstanding (in shares)	1,150,000	1,150,000
Preferred Shares of Beneficial Interest, aggregate liquidation preference	$ 28,750,000	$ 28,750,000
Preferred Series B [Member]
EQUITY
Preferred Shares of Beneficial Interest, no par value (in dollars per share)	$ 0	$ 0
Preferred Shares of Beneficial Interest, shares issued (in shares)	4,600,000	4,600,000
Preferred Shares of Beneficial Interest, shares outstanding (in shares)	4,600,000	4,600,000
Preferred Shares of Beneficial Interest, aggregate liquidation preference	$ 115,000,000	$ 115,000,000