Earnings Per Share - Schedule of Calculation of Basic and Diluted Earnings Per Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Earnings Per Share, Basic And Diluted, By Common Class, Including Two Class Method [Line Items]
Income available to common shareholders	$ 22,395	$ 717
Distributed earnings (capital) to common shareholders - basic	21,992	703
Distributed and undistributed earnings to common shareholders - diluted	21,990	697
Weighted average shares outstanding - basic	29,813,609	29,502,711
Weighted average shares outstanding - diluted	29,417,290	28,979,168
Earnings per common share - Basic	$ 0.75	$ 0.02
Earnings per common share - Diluted	$ 0.75	$ 0.02
Unvested Restricted Stock [Member]
Earnings Per Share, Basic And Diluted, By Common Class, Including Two Class Method [Line Items]
Distributed earnings (capital) to unvested restricted stock	(403)	(14)
Undistributed earnings reallocated to unvested restricted stock	$ (2)	$ (6)
Earnings per common share - Basic	$ 0.74	$ 0.03
Earnings per common share - Diluted	$ 0.74	$ 0.04