Consolidated Statements of Changes In Equity (USD $) In Thousands, unless otherwise specified	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 OP Units to common stock	0	0	95	0	0	(95)	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	253	0	253	0	0	0	0
Compensation expenses related to stock options and restricted stock	1,716	0	1,716	0	0	0	0
Adjustment for Common OP Unitholders in the Operating Partnership	0	0	(153)	0	0	153	0
Adjustment for fair market value of swap	(857)	0	0	0	0	0	(857)
Net income	31,813	0	0	2,297	27,185	2,331	0
Distributions	(36,597)	0	0	(2,297)	(31,590)	(2,710)	0
Other	(79)	0	(51)	0	(28)	0	0
Balance at Mar. 31, 2015	$ 979,092	$ 840	$ 1,035,275	$ 136,144	$ (258,642)	$ 66,713	$ (1,238)