Condensed Consolidated Statements of Shareholders' Equity - 9 months ended Sep. 30, 2015 - USD ($) $ in Thousands	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	17,110		9	17,101
Conversion and redemption of OP unit holders	(1,225)						(1,225)
Conversion of preferred shares	(500)	(7,573)	5	7,568	(500)
Share-based compensation and other expense, net of shares withheld for employee taxes	869		2	867
Dividends declared to common shareholders	(48,033)				(48,033)
Dividends declared to preferred shareholders	(5,162)				(5,162)
Distributions declared to noncontrolling interests	(1,355)						(1,355)
Dividends declared to deferred shares	(247)				(247)
Other comprehensive income adjustment	(1,976)					(1,922)	(54)
Net income	51,839				50,423		1,416
Ending balance at Sep. 30, 2015	$ 909,599	$ 92,427	$ 792	$ 1,155,798	$ (360,234)	$ (3,888)	$ 24,704