CONDENSED CONSOLIDATED STATEMENTS OF EQUITY - USD ($) $ in Thousands	Total	Cumulative Preferred Distributions	Common Shares	Cumulative Common Distributions	Additional Paid in Capital	Cumulative Net Income	Cumulative Other Comprehensive Loss	Noncontrolling Interest	Series D
Increase (Decrease) in Stockholders' Equity
Reclassification pursuant to change in accounting principle | Accounting Standards Update 2016-01						$ 1,902	$ (1,902)
Balance as of beginning of period (in shares) at Dec. 31, 2017									4,915,196
Balance as of beginning of period at Dec. 31, 2017	$ 3,300,495	$ (685,748)	$ 1,242	$ (3,111,868)	$ 4,380,313	2,596,259	(95)	$ 1,129	$ 119,263
Balance as of beginning of period (in shares) at Dec. 31, 2017	124,217,616		124,217,616
Increase (Decrease) in Stockholders' Equity
Net income	$ 257,486					257,396		90
Unrealized gain on derivative instruments	456						456
Unrealized gain on marketable securities	535						535
Repurchase of shares (in shares)			(3,027,557)
Repurchase of shares	(89,910)		$ (30)		(89,880)
Share-based compensation (in shares)			292,614
Share-based compensation	15,677		$ 3		14,686			988
Contributions	1							1
Distributions	(315,229)	(7,988)		(307,127)				(114)
Adjustment for noncontrolling interest					901			(901)
Balance as of end of period (in shares) at Sep. 30, 2018									4,915,196
Balance as of end of period at Sep. 30, 2018	$ 3,169,511	(693,736)	$ 1,215	(3,418,995)	4,306,020	2,855,557	(1,006)	1,193	$ 119,263
Balance as of end of period (in shares) at Sep. 30, 2018	121,482,673		121,482,673
Increase (Decrease) in Stockholders' Equity
Net income	$ 32,777
Unrealized gain on derivative instruments	0
Unrealized gain on marketable securities	463
Balance as of end of period (in shares) at Sep. 30, 2018									4,915,196
Balance as of end of period at Sep. 30, 2018	$ 3,169,511	$ (693,736)	$ 1,215	$ (3,418,995)	$ 4,306,020	$ 2,855,557	$ (1,006)	$ 1,193	$ 119,263
Balance as of end of period (in shares) at Sep. 30, 2018	121,482,673		121,482,673