Earnings per Common Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Numerator:
Net income (loss) attributable to common shareholders	$ 8,730	$ 5,407	$ 3,814	$ (1,840)
Less: dividends paid on unvested share-based compensation	(81)	(83)	(161)	(166)
Undistributed earnings attributable to share-based compensation	0	0	0	0
Net income (loss) available to common shareholders	$ 8,649	$ 5,324	$ 3,653	$ (2,006)
Denominator:
Weighted-average number of common shares-basic	61,082,770	52,908,195	61,039,721	51,959,049
Effect of dilutive share-based compensation	113,626	19,667	155,313	0
Weighted-average number of common shares-diluted	61,196,396	52,927,862	61,195,034	51,959,049
Net income (loss) per share attributable to common shareholders-basic	$ 0.14	$ 0.10	$ 0.06	$ (0.04)
Net income (loss) per share attributable to common shareholders-diluted	$ 0.14	$ 0.10	$ 0.06	$ (0.04)