Consolidated Statements of Changes In Equity - 9 months ended Sep. 30, 2015 - 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, 2014	$ 979,027	$ 838	$ 1,029,601	$ 136,144	$ (254,209)	$ 67,034	$ (381)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of Common OP Units to Common stock	0	0	220	0	0	(220)	0
Issuance of Common Stock through exercise of options	3,816	2	3,814	0	0	0	0
Issuance of Common Stock through employee stock purchase plan	882	0	882	0	0	0	0
Compensation expenses related to restricted stock	6,268	0	6,268	0	0	0	0
Stock Repurchased During Period, Value	(73)	0	(73)	0	0	0	0
Adjustment for Common OP Unitholders in the Operating Partnership	0	0	(469)	0	0	469	0
Adjustment for fair market value of swap	(1,231)	0	0	0	0	0	(1,231)
Net income	110,745	0	0	6,910	95,644	8,191	0
Distributions	(109,834)	0	0	(6,910)	(94,805)	(8,119)	0
Adjustments to Additional Paid in Capital, Other		3			(26)
Other	(424)		(401)	0		0	0
Balance at Sep. 30, 2015	$ 989,176	$ 843	$ 1,039,842	$ 136,144	$ (253,396)	$ 67,355	$ (1,612)