Stockholders' 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, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Weighted average Common Shares outstanding
Weighted average Common Shares outstanding	95,220,031	78,204,382	91,665,703	78,042,979
Nonvested shares	(1,777,203)	(1,491,788)	(1,794,606)	(1,508,471)
Weighted average Common Shares—Basic	93,442,828	76,712,594	89,871,097	76,534,508
Dilutive effect of restricted stock	1,278,902	1,157,948	0	1,127,211
Dilutive effect of employee stock purchase plan	114,264	150,429	0	137,572
Weighted average Common Shares outstanding—Diluted	94,835,994	78,020,971	89,871,097	77,799,291
Net Income (Loss)
Income (loss) from continuing operations	$ 4,941	$ 876	$ (21,433)	$ 2,271
Noncontrolling interests’ share in net (income) loss	(18)	(20)	34	(40)
Income (loss) from continuing operations attributable to common stockholders	4,923	856	(21,399)	2,231
Discontinued operations	14,842	4,959	15,960	9,626
NET INCOME (LOSS) ATTRIBUTABLE TO COMMON STOCKHOLDERS	$ 19,765	$ 5,815	$ (5,439)	$ 11,857
Basic Earnings (Loss) Per Common Share
Income (loss) from continuing operations (in dollars per share)	$ 0.05	$ 0.01	$ (0.24)	$ 0.03
Discontinued operations (in dollars per share)	$ 0.16	$ 0.07	$ 0.18	$ 0.12
Net income (loss) attributable to common stockholders (in dollars per share)	$ 0.21	$ 0.08	$ (0.06)	$ 0.15
Diluted Earnings (Loss) Per Common Share
Income (loss) from continuing operations (in dollars per share)	$ 0.05	$ 0.01	$ (0.24)	$ 0.03
Discontinued operations (in dollars per share)	$ 0.16	$ 0.06	$ 0.18	$ 0.12
Net income (loss) attributable to common stockholders (in dollars per share)	$ 0.21	$ 0.07	$ (0.06)	$ 0.15