Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
ASSETS
Operating (including $265,019 and $264,506 of consolidated variable interest entities, respectively)	$ 4,574,676	$ 4,473,813
Construction-in-progress	452,406	288,714
Assets held for sale (discontinued operations)	0	17,147
Real Estate Investment Property, At Cost, Total	5,027,082	4,779,674
Less accumulated depreciation and amortization (including $17.327 and $12,024 of consolidated variable interest entities, respectively)	(1,316,358)	(1,224,295)
Net real estate	3,710,724	3,555,379
Cash and cash equivalents	127,831	36,988
Accounts and notes receivable, net	87,284	73,861
Mortgage notes receivable, net	55,198	55,648
Investment in real estate partnership	32,971	33,169
Prepaid expenses and other assets	132,831	132,659
Debt issuance costs, net of accumulated amortization of $11,258 and $10,140, respectively	12,637	10,861
TOTAL ASSETS	4,159,476	3,898,565
Liabilities
Mortgages payable (including $203,423 and $205,299 of consolidated variable interest entities, respectively)	721,185	760,789
Capital lease obligations	71,677	71,693
Notes payable	299,828	299,575
Senior notes and debentures	1,213,508	1,076,545
Accounts payable and accrued expenses	160,634	120,929
Dividends payable	51,846	47,685
Security deposits payable	12,596	12,957
Other liabilities and deferred credits	103,272	103,379
Total liabilities	2,634,546	2,493,552
Commitments and contingencies (Note 7)
Redeemable noncontrolling interests	93,820	94,420
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, 66,036,174 and 64,815,446 shares issued and outstanding, respectively	660	648
Additional paid-in capital	2,000,965	1,875,525
Accumulated dividends in excess of net income	(600,091)	(586,970)
Accumulated other comprehensive loss	(3,539)	(12,388)
Total shareholders' equity of the Trust	1,407,992	1,286,812
Noncontrolling interests	23,118	23,781
Total shareholders' equity	1,431,110	1,310,593
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	$ 4,159,476	$ 3,898,565