CONDENSED CONSOLIDATED BALANCE SHEETS (unaudited) (Parenthetical) (USD $)	Jul. 31, 2012	Apr. 30, 2012
Other assets
Receivable arising from straight-lining of rents, allowance (in dollars)	$ 1,270,000	$ 1,209,000
Accounts receivable, allowance (in dollars)	334,000	154,000
Intangible assets, accumulated amortization (in dollars)	49,357,000	47,813,000
Property and equipment, accumulated depreciation (in dollars)	1,554,000	1,423,000
Deferred charges and leasing costs, accumulated amortization (in dollars)	17,509,000	16,244,000
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 (in dollars)	$ 28,750,000	$ 28,750,000
Common Shares of Beneficial Interest, no par value (in dollars per share)	0	0
Common Shares of Beneficial Interest, shares issued (in shares)	91,811,928	89,473,838
Common Shares of Beneficial Interest, shares outstanding (in shares)	91,811,928	89,473,838
Noncontrolling interests - Operating Partnership (in shares)	21,170,797	20,332,415