Earnings Per Share - Components of Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Earnings Per Share [Abstract]
Net income available to common shareholders	$ 14,309	$ 11,662	$ 39,310	$ 30,036
Weighted-average number of common shares outstanding - basic (shares)	26,872,787	26,730,347	26,830,341	26,713,953
Share-based compensation plans (shares)	1,538,436	1,001,966	1,453,378	949,584
Warrants (shares)	329,906	252,527	315,276	252,043
Weighted-average number of common shares - diluted (shares)	28,741,129	27,984,840	28,598,995	27,915,580
Basic earnings per common share (usd per share)	$ 0.53	$ 0.44	$ 1.47	$ 1.12
Diluted earnings per common share (usd per share)	$ 0.50	$ 0.42	$ 1.37	$ 1.08