CONDENSED CONSOLIDATED BALANCE SHEETS (unaudited) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Real estate properties:
Land	$ 372,714	$ 389,410
Buildings and improvements	3,399,909	3,497,942
Total real estate properties, at cost, gross	3,772,623	3,887,352
Accumulated depreciation	(880,678)	(898,939)
Total real estate properties, at cost, net	2,891,945	2,988,413
Properties held for sale	20,347	0
Acquired real estate leases, net	83,121	88,760
Cash and cash equivalents	1,742,128	1,802,729
Restricted cash	36,190	32,245
Rents receivable, net of allowance for doubtful accounts of $4,193 and $7,715, respectively	176,740	174,676
Other assets, net	152,678	144,341
Total assets	5,103,149	5,231,164
LIABILITIES AND SHAREHOLDERS’ EQUITY
Senior unsecured debt, net	1,312,148	1,450,606
Mortgage notes payable, net	245,691	246,510
Liabilities related to properties held for sale	169	0
Accounts payable and accrued expenses	120,888	123,587
Assumed real estate lease obligations, net	3,624	4,296
Rent collected in advance	23,588	27,340
Security deposits	9,670	10,338
Total liabilities	1,715,778	1,862,677
Preferred shares of beneficial interest, $0.01 par value: 50,000,000 shares authorized;
Common shares of beneficial interest, $0.01 par value: 350,000,000 shares authorized; 125,502,748 and 126,349,914 shares issued and outstanding, respectively	1,255	1,263
Additional paid in capital	4,393,409	4,414,611
Cumulative net income	2,380,111	2,333,709
Cumulative other comprehensive loss	(3,014)	(3,687)
Cumulative common distributions	(3,111,868)	(3,111,868)
Cumulative preferred distributions	(657,176)	(650,195)
Total shareholders’ equity	3,387,371	3,368,487
Total liabilities and shareholders’ equity	5,103,149	5,231,164
Series D
Preferred shares of beneficial interest, $0.01 par value: 50,000,000 shares authorized;
Series D preferred shares; 6 1/2% cumulative convertible; 4,915,196 shares issued and outstanding, aggregate liquidation preference of $122,880	119,263	119,263
Series E
Preferred shares of beneficial interest, $0.01 par value: 50,000,000 shares authorized;
Series E preferred shares; 7 1/4% cumulative redeemable on or after May 15, 2016; 11,000,000 shares issued and outstanding, aggregate liquidation preference $275,000	$ 265,391	$ 265,391