CONSLIDATED STATEMENTS OF EQUITY - USD ($) $ in Thousands	Total	Series D Preferred Shares	Common Shares	Additional Paid in Capital	Cumulative Net Income	Cumulative Other Comprehensive Loss	Cumulative Common Distributions	Cumulative Preferred Distributions	Noncontrolling Interest
Beginning balance (in shares) at Dec. 31, 2017		4,915,196	124,217,616
Beginning balance at Dec. 31, 2017	$ 3,300,495	$ 119,263	$ 1,242	$ 4,380,313	$ 2,596,259	$ (95)	$ (3,111,868)	$ (685,748)	$ 1,129
Comprehensive income:
Net income	272,908				272,813				95
Unrealized gain on derivative instrument	456					456
Unrealized gain on marketable securities	1,199					1,199
Total comprehensive income	274,563
Reclassification pursuant to change in accounting principle					1,902	(1,902)
Repurchase of shares (in shares)			(2,970,209)
Repurchase of shares	(88,255)		$ (29)	(88,226)
Surrender of shares for tax withholding (in shares)			(193,521)
Surrender of shares for tax withholding	(5,721)		$ (2)	(5,719)
Share-based compensation (in shares)			518,269
Share-based compensation	19,697		$ 5	18,371					1,321
Contributions	1								1
Distributions	(316,782)						(308,680)	(7,988)	(114)
Adjustment for noncontrolling interest				1,235					(1,235)
Ending balance (in shares) at Dec. 31, 2018		4,915,196	121,572,155
Ending balance at Dec. 31, 2018	3,183,998	$ 119,263	$ 1,216	4,305,974	2,870,974	(342)	(3,420,548)	(693,736)	1,197
Comprehensive income:
Net income	492,866				492,680				186
Unrealized gain on marketable securities	342					342
Total comprehensive income	493,208
Surrender of shares for tax withholding (in shares)			(168,327)
Surrender of shares for tax withholding	(5,487)		$ (2)	(5,485)
Share-based compensation (in shares)			520,371
Share-based compensation	14,426		$ 5	13,095					1,326
Distributions	(440,273)						(431,118)	(7,988)	(1,167)
Adjustment for noncontrolling interest				247					(247)
Ending balance (in shares) at Dec. 31, 2019		4,915,196	121,924,199
Ending balance at Dec. 31, 2019	3,245,872	$ 119,263	$ 1,219	4,313,831	3,363,654	0	(3,851,666)	(701,724)	1,295
Comprehensive income:
Net income	452,093				451,294				799
Unrealized gain on marketable securities	0
Total comprehensive income	452,093
Repurchase of shares (in shares)			(711,000)
Repurchase of shares	(20,869)		$ (7)	(20,862)
Surrender of shares for tax withholding (in shares)			(184,068)
Surrender of shares for tax withholding	(6,028)		$ (2)	(6,026)
Share-based compensation (in shares)			493,424
Share-based compensation	13,215		$ 5	11,679					1,531
Contributions	1								1
Distributions	(441,089)						(432,002)	(7,988)	(1,099)
Redemption of noncontrolling interest	(31)								(31)
Adjustment for noncontrolling interest				(3,990)					3,990
Ending balance (in shares) at Dec. 31, 2020		4,915,196	121,522,555
Ending balance at Dec. 31, 2020	$ 3,243,164	$ 119,263	$ 1,215	$ 4,294,632	$ 3,814,948	$ 0	$ (4,283,668)	$ (709,712)	$ 6,486