Condensed Consolidated Statements of Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Shares of Beneficial Interest	Paid-in Capital	Accumulated Deficit and Distributions in Excess of Net Earnings	Accumulated Other Comprehensive Loss
Beginning balance (in shares) at Dec. 31, 2018		148,234,959
Beginning balance at Dec. 31, 2018	$ 706,755	$ 1,482	$ 1,356,133	$ (638,345)	$ (12,515)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(4,629)			(4,629)
Other comprehensive loss	(969)				(969)
Distributions on common shares	(30,235)			(30,235)
Share-based compensation expense	2,625		2,625
Share-based compensation expense (modification of Restricted Stock Units)	3,044		3,044
Common share issuance related to share-based payment plans, net of shares withheld for employee taxes (in shares)		897,849
Common share issuance related to share-based payment plans, net of shares withheld for employee taxes	3,974	$ 9	3,965
Other	(88)			(88)
Ending balance (in shares) at Mar. 31, 2019		149,132,808
Ending balance at Mar. 31, 2019	$ 680,477	$ 1,491	1,365,767	(673,297)	(13,484)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Distributions declared per common share of beneficial interest (in USD per share)	$ 0.20
Beginning balance (in shares) at Dec. 31, 2019		191,799,909
Beginning balance at Dec. 31, 2019	$ 1,833,018	$ 1,918	2,582,087	(736,861)	(14,126)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	23,511			23,511
Other comprehensive loss	(29,172)				(29,172)
Distributions on common shares	(42,568)			(42,568)
Share-based compensation expense	4,298		4,298
Common share issuance related to share-based payment plans, net of shares withheld for employee taxes (in shares)		216,056
Common share issuance related to share-based payment plans, net of shares withheld for employee taxes	(1,506)	$ 2	(1,508)
Issuance of common shares	233,595	$ 83	233,512
Issuance of common shares (in shares)		8,250,000
Ending balance (in shares) at Mar. 31, 2020		200,265,965
Ending balance at Mar. 31, 2020	$ 2,020,676	$ 2,003	$ 2,818,389	$ (756,418)	$ (43,298)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Distributions declared per common share of beneficial interest (in USD per share)	$ 0.21