Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
ASSETS
Operating (including $271,468 and $78,846 of consolidated variable interest entities, respectively)	$ 4,240,708	$ 3,695,848
Construction-in-progress	193,836	163,200
Assets held for sale/disposal (discontinued operations) (including $0 and $18,311 of consolidated variable interest entities, respectively)	0	36,894
Real Estate Investment Property, At Cost, Total	4,434,544	3,895,942
Less accumulated depreciation and amortization (including $4,991 and $4,431 of consolidated variable interest entities, respectively)	(1,127,588)	(1,035,204)
Net real estate	3,306,956	2,860,738
Cash and cash equivalents	67,806	15,797
Accounts and notes receivable, net	76,152	68,997
Mortgage notes receivable, net	55,967	44,813
Investment in real estate partnerships	34,352	51,606
Prepaid expenses and other assets	106,859	110,686
Debt issuance costs, net of accumulated amortization of $9,098 and $9,075, respectively	11,816	6,916
TOTAL ASSETS	3,659,908	3,159,553
Liabilities
Mortgages payable (including $207,683 and $22,785 of consolidated variable interest entities, respectively)	747,523	529,501
Capital lease obligations	63,093	59,940
Notes payable	295,159	97,881
Senior notes and debentures	1,004,635	1,079,827
Accounts payable and accrued expenses	104,498	102,574
Dividends payable	44,229	41,601
Security deposits payable	12,221	11,751
Other liabilities and deferred credits	62,621	55,348
Total liabilities	2,333,979	1,978,423
Commitments and contingencies (Note 9)
Redeemable Noncontrolling Interest, Equity, Carrying Amount	85,325	65,362
Shareholders' equity
Preferred shares, authorized 15,000,000 shares, $.01 par: 5.417% Series 1 Cumulative Convertible Preferred Shares, (stated at liquidation preference $25 per share), 399,896 shares issued and outstanding	9,997	9,997
Common shares of beneficial interest, $.01 par, 100,000,000 shares authorized, 63,544,150 and 61,526,418 shares issued and outstanding, respectively	636	615
Additional paid-in capital (Note 2)	1,764,940	1,611,706
Accumulated dividends in excess of net income	(555,541)	(527,582)
Accumulated other comprehensive loss	(3,940)	0
Total shareholders' equity of the Trust	1,216,092	1,094,736
Noncontrolling interests (Note 2)	24,512	21,032
Total shareholders' equity	1,240,604	1,115,768
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	$ 3,659,908	$ 3,159,553