Earnings per Common Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Numerator:
Net income (loss) attributable to common shareholders	$ 4,836	$ 11,315	$ 8,730	$ (4,916)	$ 2,632	$ 7,462	$ 5,407	$ (7,247)	$ 19,965	$ 8,254	$ 4,443
Less: dividends paid on unvested share-based compensation									(328)	(310)	(398)
Undistributed earnings attributable to share-based compensation									0	0	0
Net income (loss) available to common shareholders									$ 19,637	$ 7,944	$ 4,045
Denominator:
Weighted-average number of common shares-basic									61,498,389	55,806,543	47,921,200
Effect of dilutive share-based compensation									338,352	148,954	45,107
Weighted-average number of common shares-diluted									61,836,741	55,955,497	47,966,307
Net income (loss) per share available to common shareholders-basic									$ 0.32	$ 0.14	$ 0.08
Net income (loss) per share available to common shareholders-diluted									$ 0.32	$ 0.14	$ 0.08