CONDENSED CONSOLIDATED BALANCE SHEETS (unaudited) (Parenthetical) - USD ($)	Apr. 30, 2017	Apr. 30, 2016
Other assets
Intangible assets, accumulated amortization	$ 5,444,000	$ 6,230,000
Property and equipment, accumulated depreciation	1,199,000	1,058,000
Deferred charges and leasing costs, accumulated amortization	4,275,000	3,719,000
LIABILITIES
Mortgages payable, loan costs	$ 3,480,000	$ 4,931,000
EQUITY
Common Shares of Beneficial Interest, no par value (in dollars per share)	$ 0	$ 0
Common Shares of Beneficial Interest, shares issued (in shares)	121,199,299	121,091,249
Common Shares of Beneficial Interest, shares outstanding (in shares)	121,199,299	121,091,249
Noncontrolling interests - Operating Partnership (in shares)	15,617,216	16,285,239
Receivable Arising from Straight-Lining of Rents [Member]
Other assets
Accounts receivable, allowance	$ 340,000	$ 333,000
Accounts Receivable [Member]
Other assets
Accounts receivable, allowance	$ 210,000	$ 97,000
Series A Preferred Stock [Member]
EQUITY
Preferred Shares of Beneficial Interest, par value (in dollars per share)	$ 0	$ 0
Preferred Shares of Beneficial Interest, shares issued (in shares)	0	1,150,000
Preferred Shares of Beneficial Interest, shares outstanding (in shares)	0	1,150,000
Preferred shares liquidation preference	$ 28,750,000	$ 28,750,000
Series B Preferred Stock [Member]
EQUITY
Preferred Shares of Beneficial Interest, 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 liquidation preference	$ 115,000,000	$ 115,000,000