CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($)	Apr. 30, 2016	Apr. 30, 2015
Other assets
Intangible assets, accumulated amortization	$ 6,230,000	$ 6,112,000
Property and equipment, accumulated depreciation	1,058,000	1,374,000
Deferred charges and leasing costs, accumulated amortization	$ 8,716,000	$ 7,524,000
EQUITY
Common Shares of Beneficial Interest, no par value (in dollars per share)	$ 0	$ 0
Common Shares of Beneficial Interest, shares issued (in shares)	121,091,249	124,455,624
Common Shares of Beneficial Interest, shares outstanding (in shares)	121,091,249	124,455,624
Noncontrolling interests - Operating Partnership (in shares)	16,285,239	13,999,725
Receivable Arising from Straight-Lining of Rents [Member]
Other assets
Accounts receivable, allowance	$ 333,000	$ 222,000
Accounts Receivable [Member]
Other assets
Accounts receivable, allowance	$ 97,000	$ 439,000
Preferred Class 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 Class 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