CONSOLIDATED STATEMENTS OF EQUITY (USD $) In Thousands	Total	Preferred Shares	Common Shares	Paid-in Capital	Accumulated Distributions in Excess of Net Income	Deferred Compensation Obligation	Accumulated Other Comprehensive Loss	Treasury Stock at Cost	Non-Controlling Interests
Balance at Dec. 31, 2011	$ 3,077,892	$ 375,000	$ 27,711	$ 4,138,812	$ (1,493,353)	$ 13,934	$ (1,403)	$ (15,017)	$ 32,208
Balance, shares at Dec. 31, 2011			277,115
Issuance of common shares related to stock plans	3,035	0	32	2,741	0	0	0	262	0
Issuance of common shares related to stock plans, shares			322
Issuance of common shares for cash offering	492,129	0	3,634	485,752	0	0	0	2,743	0
Issuance of common shares for cash offering, shares	36,500		36,335
Issuance of preferred shares	192,855	200,000	0	(7,145)	0	0	0	0	0
Issuance of restricted stock	749	0	147	(2,334)	0	910	0	2,026	0
Issuance of restricted stock, shares			1,467
Vesting of restricted stock	(2,936)	0	0	2,818	0	712	0	(6,466)	0
Stock-based compensation	2,809	0	0	2,809	0	0	0	0	0
Contributions from non-controlling interests	492	0	0	0	0	0	0	0	492
Distributions to non-controlling interests	(9,145)	0	0	0	0	0	0	0	(9,145)
Redemption of preferred shares	(170,000)	(170,000)	0	5,804	(5,804)	0	0	0	0
Dividends declared-common shares	(141,152)	0	0	0	(141,152)	0	0	0	0
Dividends declared-preferred shares	(28,691)	0	0	0	(28,691)	0	0	0	0
Comprehensive income (loss)	(51,577)	0	0	0	(25,822)	0	(26,522)	0	767
Balance at Dec. 31, 2012	3,366,460	405,000	31,524	4,629,257	(1,694,822)	15,556	(27,925)	(16,452)	24,322
Balance, shares at Dec. 31, 2012			315,239
Issuance of common shares related to stock plans	1,622	0	12	1,235	0	0	0	375	0
Issuance of common shares related to stock plans, shares			120
Issuance of common shares for cash offering	788,045	0	4,402	782,406	0	0	0	1,237	0
Issuance of common shares for cash offering, shares	44,100		44,020
Issuance of preferred shares	144,863	150,000	0	(5,137)	0	0	0	0	0
Issuance of restricted stock	0	0	0	(3,118)	0	1,272	0	1,846	0
Vesting of restricted stock	(2,201)	0	0	3,142	0	(126)	0	(5,217)	0
Stock-based compensation	4,332	0	0	4,332	0	0	0	0	0
Issuance of OP Units	0
Contributions from non-controlling interests	374	0	0	0	0	0	0	0	374
Distributions to non-controlling interests	(1,571)	0	0	0	0	0	0	0	(1,571)
Redemption of preferred shares	(150,000)	(150,000)	0	5,246	(5,246)	0	0	0	0
Dividends declared-common shares	(177,709)	0	0	0	(177,709)	0	0	0	0
Dividends declared-preferred shares	(27,686)	0	0	0	(27,686)	0	0	0	0
Comprehensive income (loss)	(18,650)	0	0	0	(10,175)	0	(8,568)	0	93
Balance at Dec. 31, 2013	3,927,879	405,000	35,938	5,417,363	(1,915,638)	16,702	(36,493)	(18,211)	23,218
Balance, shares at Dec. 31, 2013			359,379
Issuance of common shares related to stock plans	6,930	0	40	6,066	0	0	0	824	0
Issuance of common shares related to stock plans, shares			397
Issuance of common shares for cash offering	11,634	0	66	11,568	0	0	0	0	0
Issuance of common shares for cash offering, shares	700		664
Issuance of restricted stock	0		23	(7,337)	0	1,029	0	6,285	0
Issuance of restricted stock, shares			227
Vesting of restricted stock	(1,828)	0	4	4,834	0	(1,122)	0	(5,544)	0
Vesting of restricted stock, shares			44
Stock-based compensation	4,367	0	0	4,367	0	0	0	0	0
Issuance of OP Units	18,256	0	0	0	0	0	0	0	18,256
Contributions from non-controlling interests	93	0	0	0	0	0	0	0	93
Distributions to non-controlling interests	(14,184)	0	0	0	0	0	0	0	(14,184)
Redemption of preferred shares	(55,026)	(55,000)	0	1,917	(1,943)	0	0	0	0
Dividends declared-common shares	(223,016)	0	0	0	(223,016)	0	0	0	0
Dividends declared-preferred shares	(23,897)	0	0	0	(23,897)	0	0	0	0
Comprehensive income (loss)	146,320	0	0	0	117,282	0	29,141	0	(103)
Balance at Dec. 31, 2014	$ 3,797,528	$ 350,000	$ 36,071	$ 5,438,778	$ (2,047,212)	$ 16,609	$ (7,352)	$ (16,646)	$ 27,280
Balance, shares at Dec. 31, 2014			360,711