CONDENSED CONSOLIDATED BALANCE SHEETS (unaudited) (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Jan. 31, 2012	Apr. 30, 2011
Real estate investments
Mortgage loans receivable, net of allowance (in dollars)	$ 0	$ 3
Other assets
Receivable arising from straight-lining of rents, net of allowance (in dollars)	1,156	996
Accounts receivable, net of allowance (in dollars)	185	317
Intangible assets, net of accumulated amortization (in dollars)	46,674	42,154
Property and equipment, net of accumulated depreciation (in dollars)	1,499	1,231
Deferred charges and leasing costs, net of accumulated amortization (in dollars)	16,622	13,675
EQUITY
Preferred Shares of Beneficial Interest, no par value (in dollars per share)	$ 0.0000	$ 0.0000
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)	$ 0.0000	$ 0.0000
Common Shares of Beneficial Interest, shares issued (in shares)	85,743,308	80,523,265
Common Shares of Beneficial Interest, shares outstanding (in shares)	85,743,308	80,523,265
Noncontrolling interests - Operating Partnership (in shares)	19,596,222	20,067,350