Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2015	[1]	Sep. 30, 2015	[2]	Jun. 30, 2015	[3]	Mar. 31, 2015	[4]	Dec. 31, 2014	[5]	Sep. 30, 2014	[6]	Jun. 30, 2014	[7]	Mar. 31, 2014	[8]	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Weighted Average Common Shares
Weighted average Common Shares outstanding																	100,280,059	97,093,960	92,725,112
Non-vested shares																	(1,108,707)	(1,814,734)	(1,784,485)
Weighted average Common Shares - Basic																	99,171,352	95,279,226	90,940,627
Dilutive effect of non-vested shares																	623,212	1,364,236
Dilutive effect of employee stock purchase plan																	85,738	115,948
Weighted average Common Shares - Diluted																	99,880,302	96,759,410	90,940,627
Net Income (loss)
Income (loss) from continuing operations	$ 19,354		$ 16,848		$ 17,586		$ 5,049		$ 9,060		$ 8,437		$ 9,005		$ 7,477		$ 58,836	$ 33,979	$ (13,092)
Noncontrolling interests’ share in earnings	0		0		0		0		0		(162)		(40)		(111)			(313)	(37)
Income (loss) from continuing operations attributable to common stockholders																	58,836	33,666	(13,129)
Discontinued operations	(696)		10,632		330		333		9,013		(4,284)		(2,994)		(3,514)		10,600	(1,779)	20,075
NET INCOME ATTRIBUTABLE TO COMMON STOCKHOLDERS	$ 18,658		$ 27,480		$ 17,916		$ 5,382		$ 18,073		$ 3,991		$ 5,971		$ 3,852		$ 69,436	$ 31,887	$ 6,946
Basic Earnings (loss) Per Common Share
Income (loss) from continuing operations (in dollars per share)																	$ 0.59	$ 0.35	$ (0.14)
Discontinued operations (in dollars per share)																	0.11	(0.02)	0.22
Net income attributable to common stockholders (in dollars per share)	$ 0.19		$ 0.28		$ 0.18		$ 0.05		$ 0.19		$ 0.04		$ 0.06		$ 0.04		0.70	0.33	0.08
Diluted Earnings (loss) Per Common Share
Income (loss) from continuing operations (in dollars per share)																	0.59	0.35	(0.14)
Discontinued operations (in dollars per share)																	0.11	(0.02)	0.22
Net income attributable to common stockholders (in dollars per share)	$ 0.19		$ 0.27		$ 0.18		$ 0.05		$ 0.18		$ 0.04		$ 0.06		$ 0.04		$ 0.70	$ 0.33	$ 0.08

[1] The increases in net income and amounts per share for the fourth quarter of 2015 are primarily attributable to gains on sales of real estate totaling $9.1 million, partially offset by impairment charges of $0.7 million.

[2] The increases in net income and amounts per share for the third quarter of 2015 are primarily attributable to a $10.6 million gain on the sale of one property previously classified as an asset held for sale.

[3] The increases in net income and amounts per share for the second quarter of 2015 are primarily attributable to a $41.5 million gain on the sale of two properties, partially offset by a $28.0 million loss on extinguishment of the Senior Notes due 2017.

[4] The decreases in net income and amounts per share for the first quarter of 2015 are primarily attributable to impairment charges of $3.3 million

[5] The increases in net income and amounts per share for the fourth quarter of 2014 are primarily attributable to gains on sales of real estate totaling $9.3 million, partially offset by impairment charges of $1.0 million.

[6] The decreases in net income and amounts per share for the third quarter of 2014 are primarily attributable to impairment charges of $4.5 million.

[7] The increases in net income and amounts per share for the second quarter of 2014 are primarily attributable to a $1.9 million cash reimbursement received by the Company for certain operating expenses paid by the Company for years 2006 through 2013.

[8] The decreases in net income and amounts per share for the first quarter of 2014 are primarily attributable to impairment charges of $3.4 million.