CONDENSED CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Real estate properties:
Land	$ 748,302	$ 699,135
Buildings and improvements	5,146,617	4,838,030
Total real estate properties, at cost, gross	5,894,919	5,537,165
Accumulated depreciation	(956,057)	(895,059)
Total real estate properties, at cost, net	4,938,862	4,642,106
Properties held for sale		573,531
Acquired real estate leases, net	227,197	255,812
Equity investments	531,862	517,991
Cash and cash equivalents	428,373	222,449
Restricted cash	22,829	22,101
Rents receivable, net of allowance for doubtful accounts of $7,451 and $7,885, respectively	238,033	223,769
Other assets, net	206,204	188,675
Total assets	6,593,360	6,646,434
LIABILITIES AND SHAREHOLDERS' EQUITY
Revolving credit facility	235,000	235,000
Senior unsecured debt, net	1,856,373	1,855,900
Mortgage notes payable, net	895,231	914,510
Liabilities related to properties held for sale		28,734
Accounts payable and accrued expenses	138,412	165,855
Assumed real estate lease obligations, net	31,354	33,935
Rent collected in advance	29,266	27,553
Security deposits	13,852	11,976
Due to related persons	22,984	9,385
Total liabilities	3,222,472	3,282,848
Common shares of beneficial interest, $0.01 par value:
Common shares of beneficial interest, $0.01 par value: 350,000,000 shares authorized; 128,859,923 and 118,386,918 shares issued and outstanding, respectively	1,289	1,184
Additional paid in capital	4,483,653	4,213,474
Cumulative net income	2,235,673	2,209,840
Cumulative other comprehensive loss	(21,205)	(38,331)
Cumulative common distributions	(3,111,868)	(3,082,271)
Cumulative preferred distributions	(601,331)	(573,971)
Total shareholders' equity	3,370,888	3,363,586
Total liabilities and shareholders' equity	6,593,360	6,646,434
Series D
50,000,000 shares authorized;
Preferred shares of beneficial interest, $0.01 par value	119,286	368,270
Series E
50,000,000 shares authorized;
Preferred shares of beneficial interest, $0.01 par value	$ 265,391	$ 265,391