Consolidated Statements of Changes In Equity - 3 months ended Mar. 31, 2016 - USD ($) $ in Thousands	Total	Common Stock	Paid-in Capital	6.75% Series C Cumulative Redeemable Perpetual Preferred Stock	Distributions in Excess of Accumulated Earnings	Non- controlling interests – Common OP Units	Accumulated Other Comprehensive Loss
Balance at Dec. 31, 2015	$ 992,691	$ 843	$ 1,039,140	$ 136,144	$ (250,506)	$ 67,623	$ (553)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Common Stock through exercise of options	5,232	2	5,230
Issuance of Common Stock through employee stock purchase plan	144		144
Compensation expenses related to restricted stock	1,914		1,914
Repurchase of Common Stock or Common OP units	(53)		(53)
Adjustment for Common OP Unitholders in the Operating Partnership	0		(301)			301
Adjustment for fair market value of swap	(608)						(608)
Net income	57,190			2,297	50,583	4,310
Distributions	(41,312)			(2,297)	(35,952)	(3,063)
Other	(41)		(41)
Balance at Mar. 31, 2016	$ 1,015,157	$ 845	$ 1,046,033	$ 136,144	$ (235,875)	$ 69,171	$ (1,161)