CONSOLIDATED STATEMENTS OF EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Preferred Shares	Common Shares	Additional Paid-in Capital	Accumulated Distributions in Excess of Net Income	Deferred Compensation Obligation	Accumulated Other Comprehensive Loss	Treasury Stock at Cost	Non-Controlling Interests
Beginning 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
Beginning Balance, shares at Dec. 31, 2014			360,711
Issuance of common shares related to stock plans	7,388	0	$ 44	7,214	0	0	0	130	0
Issuance of common shares related to stock plans, shares			435
Stock-based compensation, net	2,979	0	$ 6	4,123	0	(1,072)	0	(78)	0
Stock-based compensation, net, shares			60
Issuance of common stock in settlement of conversion feature	(144)	0	$ 304	(1,726)	0	0	0	1,278	0
Issuance of common stock in settlement of conversion feature, shares			3,043
Redemption of OP Units	$ (30)	$ 0	$ 104	$ 18,122	$ 0	$ 0	$ 0	$ 0	$ (18,256)
Redemption of OP Units, shares	0	0	1,043	0	0	0	0	0	0
Distributions to non-controlling interests	$ (1,817)	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ (1,817)
Dividends declared- common shares	(250,038)	0	0	0	(250,038)	0	0	0	0
Dividends declared- preferred shares	(22,375)	0	0	0	(22,375)	0	0	0	0
Comprehensive (loss) income	(70,022)	0	0	0	(72,168)	0	1,069	0	1,077
Ending Balance at Dec. 31, 2015	3,463,469	350,000	$ 36,529	5,466,511	(2,391,793)	15,537	(6,283)	(15,316)	8,284
Ending Balance, shares at Dec. 31, 2015			365,292
Issuance of common shares related to stock plans	16,440	0	$ 101	14,747	0	0	0	1,592	0
Issuance of common shares related to stock plans, shares			1,006
Stock-based compensation, net	4,333	0	$ 0	5,954	0	(388)	0	(1,233)	0
Stock-based compensation, net, shares			0
Distributions to non-controlling interests	(1,093)	0	$ 0	0	0	0	0	0	(1,093)
Dividends declared- common shares	(278,171)	0	0	0	(278,171)	0	0	0	0
Dividends declared- preferred shares	(22,375)	0	0	0	(22,375)	0	0	0	0
Comprehensive (loss) income	63,409	0	0	0	60,012	0	2,091	0	1,306
Ending Balance at Dec. 31, 2016	3,246,012	350,000	$ 36,630	5,487,212	(2,632,327)	15,149	(4,192)	(14,957)	8,497
Ending Balance, shares at Dec. 31, 2016			366,298
Issuance of common shares related to stock plans	30,145	0	$ 221	23,620	0	0	0	6,304	0
Issuance of common shares related to stock plans, shares			2,214
Issuance of preferred shares	168,870	175,000	$ 0	(6,130)	0	0	0	0	0
Stock-based compensation, net	2,123	0	$ 0	8,495	0	(6,372)	0	0	0
Stock-based compensation, net, shares			0
Distributions to non-controlling interests	(835)	0	$ 0	0	0	0	0	0	(835)
Dividends declared- common shares	(279,930)	0	0	0	(279,930)	0	0	0	0
Dividends declared- preferred shares	(29,192)	0	0	0	(29,192)	0	0	0	0
Comprehensive (loss) income	(239,755)	0	0	0	(241,685)	0	3,086	0	(1,156)
Ending Balance at Dec. 31, 2017	$ 2,897,438	$ 525,000	$ 36,851	$ 5,513,197	$ (3,183,134)	$ 8,777	$ (1,106)	$ (8,653)	$ 6,506
Ending Balance, shares at Dec. 31, 2017			368,512