Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
ASSETS
Operating (including $278,826 and $263,570 of consolidated variable interest entities, respectively)	$ 4,490,960	$ 4,232,608
Construction-in-progress	288,714	193,836
Real Estate Investment Property, At Cost, Total	4,779,674	4,426,444
Less accumulated depreciation and amortization (including $12,024 and $4,991 of consolidated variable interest entities, respectively)	(1,224,295)	(1,127,588)
Net real estate	3,555,379	3,298,856
Cash and cash equivalents	36,988	67,806
Accounts and notes receivable, net	73,861	75,921
Mortgage notes receivable, net	55,648	55,967
Investment in real estate partnership	33,169	34,352
Prepaid expenses and other assets	132,659	121,492
Debt issuance costs, net of accumulated amortization of $10,140 and $9,098, respectively	10,861	11,816
TOTAL ASSETS	3,898,565	3,666,210
Liabilities
Mortgages payable (including $205,299 and $207,683 of consolidated variable interest entities, respectively)	760,789	747,523
Capital lease obligations	71,693	63,093
Notes payable	299,575	295,159
Senior notes and debentures	1,076,545	1,004,635
Accounts payable and accrued expenses	120,929	104,660
Dividends payable	47,685	44,229
Security deposits payable	12,957	12,221
Other liabilities and deferred credits	103,379	68,761
Total liabilities	2,493,552	2,340,281
Commitments and contingencies (Note 9)
Redeemable Noncontrolling Interests	94,420	85,325
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, 64,815,446 and 63,544,150 shares issued and outstanding, respectively	648	636
Additional paid-in capital	1,875,525	1,764,940
Accumulated dividends in excess of net income	(586,970)	(555,541)
Accumulated other comprehensive loss	(12,388)	(3,940)
Total shareholders' equity of the Trust	1,286,812	1,216,092
Noncontrolling interests	23,781	24,512
Total shareholders' equity	1,310,593	1,240,604
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	$ 3,898,565	$ 3,666,210