Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Preferred Shares	Common Shares	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Distributions in Excess of Retained Earnings	Total Shareholders' Equity	Non-Controlling Interests
Preferred stock, beginning balance (in shares) at Dec. 31, 2017		10,000,000
Common stock, beginning balance (in shares) at Dec. 31, 2017			68,812,575
Beginning balance at Dec. 31, 2017	$ 1,503,526	$ 100	$ 688	$ 1,685,437	$ 3,689	$ (191,013)	$ 1,498,901	$ 4,625
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common shares for Board of Trustees compensation (in shares)			17,410
Issuance of common shares for Board of Trustees compensation	662		$ 1	661			662
Repurchase of common shares (in shares)			(69,687)
Repurchase of common shares	(2,507)		$ (1)	(2,506)			(2,507)
Share-based compensation (in shares)			151,887
Share-based compensation	(269)		$ 1	(546)			(545)	276
Distributions on common shares/units	(26,274)					(26,184)	(26,184)	(90)
Distributions on preferred shares	(4,023)					(4,023)	(4,023)
Other comprehensive income (loss):
Unrealized gain (loss) on derivative instruments	5,278				5,278		5,278
Unrealized gain (loss) on marketable securities	(579)				(579)		(579)
Net income (loss)	24,516					24,409	24,409	107
Preferred stock, ending balance (in shares) at Mar. 31, 2018		10,000,000
Common stock, ending balance (in shares) at Mar. 31, 2018			68,912,185
Ending balance at Mar. 31, 2018	$ 1,500,330	$ 100	$ 689	1,683,046	8,936	(197,359)	1,495,412	4,918
Preferred stock, beginning balance (in shares) at Dec. 31, 2018	20,400,000	20,400,000
Common stock, beginning balance (in shares) at Dec. 31, 2018	130,311,289		130,311,289
Beginning balance at Dec. 31, 2018	$ 3,769,930	$ 204	$ 1,303	4,065,804	1,330	(308,806)	3,759,835	10,095
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of shares, net of offering costs	(275)			(275)			(275)
Issuance of common shares for Board of Trustees compensation (in shares)			25,282
Issuance of common shares for Board of Trustees compensation	740		$ 1	739			740
Repurchase of common shares (in shares)			(126,681)
Repurchase of common shares	(4,009)		$ (1)	(4,008)			(4,009)
Share-based compensation (in shares)			275,066
Share-based compensation	1,848		$ 2	1,570			1,572	276
Distributions on common shares/units	(49,912)					(49,771)	(49,771)	(141)
Distributions on preferred shares	(8,139)					(8,139)	(8,139)
Other comprehensive income (loss):
Unrealized gain (loss) on derivative instruments	(9,039)				(9,039)		(9,039)
Unrealized gain (loss) on marketable securities	0
Net income (loss)	$ 5,655					5,635	5,635	20
Preferred stock, ending balance (in shares) at Mar. 31, 2019	20,400,000	20,400,000
Common stock, ending balance (in shares) at Mar. 31, 2019	130,484,956		130,484,956
Ending balance at Mar. 31, 2019	$ 3,706,799	$ 204	$ 1,305	$ 4,063,830	$ (7,709)	$ (361,081)	$ 3,696,549	$ 10,250