Condensed Consolidated Statements of Shareholders' Equity (USD $) In Thousands, unless otherwise specified	Total	Preferred Shares	Common Shares	Additional Paid-in Capital	Accumulated Distributions in Excess of Net Income	Accumulated Other Comprehensive Loss	Noncontrolling Interest
Beginning balance at Dec. 31, 2014	$ 898,279	$ 100,000	$ 776	$ 1,130,262	$ (356,715)	$ (1,966)	$ 25,922
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common shares	16,769		9	16,760
Share-based compensation and other expense, net of shares withheld for employee taxes	52		1	51
Dividends declared to common shareholders	(15,578)				(15,578)
Dividends declared to preferred shareholders	(1,812)				(1,812)
Distributions declared to noncontrolling interests	(450)						(450)
Dividends declared to deferred shares	(77)				(77)
Other comprehensive income adjustment	(1,465)					(1,424)	(41)
Net income	9,944				9,667		277
Ending balance at Mar. 31, 2015	$ 905,662	$ 100,000	$ 786	$ 1,147,073	$ (364,515)	$ (3,390)	$ 25,708