Consolidated Balance Sheets (Parentheticals) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
ASSETS
Accounts receivable, allowance for doubtful accounts	$ 34,607	$ 37,674
Receivable arising from the straight-lining of rents, allowance	3,678	3,165
Deferred leasing and financing costs, accumulated amortization	233,769	224,509
Identified intangible assets (included in other assets): Accumulated amortization	$ 363,211	$ 350,162
LIABILITIES, REDEEMABLE NONCONTROLLING INTERESTS AND EQUITY
Preferred shares of beneficial interest: authorized shares	110,000,000	110,000,000
Preferred shares of beneficial interest: issued shares	52,684,609	51,184,609
Preferred shares of beneficial interest: outstanding shares	52,684,609	51,184,609
Common shares of beneficial interest: par value per share	$ 0.04	$ 0.04
Common shares of beneficial interest: authorized shares	250,000,000	250,000,000
Common shares of beneficial interest: issued shares	186,935,027	186,734,711
Common shares of beneficial interest: outstanding shares	186,935,027	186,734,711
Common Class A [Member]
LIABILITIES, REDEEMABLE NONCONTROLLING INTERESTS AND EQUITY
Outstanding Partnership Units held by Third Parties	11,347,226	11,215,682
Cumulative Redeemable Preferred Unit [Member]
LIABILITIES, REDEEMABLE NONCONTROLLING INTERESTS AND EQUITY
Outstanding Partnership Units held by Third Parties	1,800,001	1,800,001