Earnings 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
Numerator:
Net income (loss) attributable to common shareholders	$ 11,315	$ 7,462	$ 15,129	$ 5,622
Less: dividends paid on unvested share-based compensation	(81)	(83)	(242)	(249)
Undistributed earnings attributable to share-based compensation	(11)	0	0	0
Net income (loss) available to common shareholders	$ 11,223	$ 7,379	$ 14,887	$ 5,373
Denominator:
Weighted-average number of common shares-basic	61,179,524	58,714,055	61,086,834	54,227,155
Effect of dilutive share-based compensation	168,339	46,279	192,418	87,314
Weighted-average number of common shares-diluted	61,347,863	58,760,334	61,279,252	54,314,469
Net income (loss) per share available to common shareholders-basic	$ 0.18	$ 0.13	$ 0.24	$ 0.10
Net income (loss) per share available to common shareholders-diluted	$ 0.18	$ 0.13	$ 0.24	$ 0.10