Equity - Computation of basic and diluted earnings (loss) per common share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Weighted average Common Shares outstanding
Weighted average Common Shares outstanding	96,353,818	90,988,589	96,182,753	89,859,083
Nonvested shares	(1,846,253)	(1,784,422)	(1,851,863)	(1,803,451)
Weighted average Common Shares—Basic	94,507,565	89,204,167	94,330,890	88,055,632
Dilutive effect of restricted stock	1,363,174		1,333,199
Dilutive effect of employee stock purchase plan	106,923		123,958
Weighted average Common Shares outstanding—Diluted	95,977,662	89,204,167	95,788,047	88,055,632
Net Income (Loss)
Income from continuing operations	$ 9,344	$ (27,558)	$ 17,119	$ (26,618)
Noncontrolling interests’ share in net (income) loss	(40)	33	(151)	52
Income (loss) from continuing operations attributable to common stockholders	9,304	(27,525)	16,968	(26,566)
Discontinued operations	(3,333)	3,320	(7,145)	1,362
NET INCOME (LOSS) ATTRIBUTABLE TO COMMON STOCKHOLDERS	$ 5,971	$ (24,205)	$ 9,823	$ (25,204)
Basic Earnings (Loss) Per Common Share
Income (loss) from continuing operations (in dollars per share)	$ 0.10	$ (0.31)	$ 0.18	$ (0.30)
Discontinued operations (in dollars per share)	$ (0.04)	$ 0.04	$ (0.08)	$ 0.01
Net income (loss) attributable to common stockholders (in dollars per share)	$ 0.06	$ (0.27)	$ 0.10	$ (0.29)
Diluted Earnings (Loss) Per Common Share
Income (loss) from continuing operations (in dollars per share)	$ 0.10	$ (0.31)	$ 0.18	$ (0.30)
Discontinued operations (in dollars per share)	$ (0.04)	$ 0.04	$ (0.08)	$ 0.01
Net income (loss) attributable to common stockholders (in dollars per share)	$ 0.06	$ (0.27)	$ 0.10	$ (0.29)
Restricted Stock [Member]
Diluted Earnings (Loss) Per Common Share
Antidilutive securities excluded from computation of earnings per share, amount		1,320,412		1,303,441
Employee Stock [Member]
Diluted Earnings (Loss) Per Common Share
Antidilutive securities excluded from computation of earnings per share, amount		158,930		185,281