Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
ASSETS
Operating (including $264,821 and $264,506 of consolidated variable interest entities, respectively)	$ 4,550,534	$ 4,490,960
Construction-in-progress	401,385	288,714
Real Estate Investment Property, At Cost, Total	4,951,919	4,779,674
Less accumulated depreciation and amortization (including $15,579 and $12,024 of consolidated variable interest entities, respectively)	(1,286,923)	(1,224,295)
Net real estate	3,664,996	3,555,379
Cash and cash equivalents	108,366	36,988
Accounts and notes receivable, net	84,103	73,861
Mortgage notes receivable, net	55,494	55,648
Investment in real estate partnership	33,029	33,169
Prepaid expenses and other assets	125,804	132,659
Debt issuance costs, net of accumulated amortization of $10,488 and $10,140, respectively	13,411	10,861
TOTAL ASSETS	4,085,203	3,898,565
Liabilities
Mortgages payable (including $204,055 and $205,299 of consolidated variable interest entities, respectively)	724,984	760,789
Capital lease obligations	71,682	71,693
Notes payable	299,979	299,575
Senior notes and debentures	1,213,333	1,076,545
Accounts payable and accrued expenses	138,932	120,929
Dividends payable	48,296	47,685
Security deposits payable	12,758	12,957
Other liabilities and deferred credits	97,302	103,379
Total liabilities	2,607,266	2,493,552
Commitments and contingencies (Note 7)
Redeemable noncontrolling interests	94,150	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, 65,687,234 and 64,815,446 shares issued and outstanding, respectively	657	648
Additional paid-in capital	1,963,000	1,875,525
Accumulated dividends in excess of net income	(610,569)	(586,970)
Accumulated other comprehensive loss	(2,368)	(12,388)
Total shareholders' equity of the Trust	1,360,717	1,286,812
Noncontrolling interests	23,070	23,781
Total shareholders' equity	1,383,787	1,310,593
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	$ 4,085,203	$ 3,898,565