Equity - Computation of basic and diluted earnings (loss) per common share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Weighted average Common Shares outstanding
Weighted average Common Shares outstanding	97,651,673	95,220,031	96,677,774	91,665,703
Nonvested shares	(1,793,639)	(1,777,203)	(1,832,242)	(1,794,606)
Weighted average Common Shares—Basic	95,858,034	93,442,828	94,845,532	89,871,097
Dilutive effect of restricted stock	1,369,047	1,278,902	1,346,032
Dilutive effect of employee stock purchase plan	101,963	114,264	118,854
Weighted average Common Shares outstanding—Diluted	97,329,044	94,835,994	96,310,418	89,871,097
Net Income (Loss)
Income from continuing operations	$ 8,537	$ 4,614	$ 25,233	$ (22,372)
Noncontrolling interests’ share in net (income) loss	(162)	(18)	(313)	34
Income (loss) from continuing operations attributable to common stockholders	8,375	4,596	24,920	(22,338)
Discontinued operations	(4,384)	15,169	(11,106)	16,899
NET INCOME (LOSS) ATTRIBUTABLE TO COMMON STOCKHOLDERS	$ 3,991	$ 19,765	$ 13,814	$ (5,439)
Basic Earnings (Loss) Per Common Share
Income (loss) from continuing operations (in dollars per share)	$ 0.09	$ 0.05	$ 0.27	$ (0.25)
Discontinued operations (in dollars per share)	$ (0.05)	$ 0.16	$ (0.12)	$ 0.19
Net income (loss) attributable to common stockholders (in dollars per share)	$ 0.04	$ 0.21	$ 0.15	$ (0.06)
Diluted Earnings (Loss) Per Common Share
Income (loss) from continuing operations (in dollars per share)	$ 0.09	$ 0.05	$ 0.26	$ (0.25)
Discontinued operations (in dollars per share)	$ (0.05)	$ 0.16	$ (0.12)	$ 0.19
Net income (loss) attributable to common stockholders (in dollars per share)	$ 0.04	$ 0.21	$ 0.14	$ (0.06)
Restricted Stock [Member]
Diluted Earnings (Loss) Per Common Share
Antidilutive securities excluded from computation of earnings per share, amount				1,294,953
Employee Stock [Member]
Diluted Earnings (Loss) Per Common Share
Antidilutive securities excluded from computation of earnings per share, amount				164,418