Earnings Per Share - Components of Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Abstract]
Net income available to common shareholders	$ 16,780	$ 14,309	$ 11,049	$ 13,952	$ 13,178	$ 11,662	$ 10,233	$ 8,136	$ 56,090	$ 43,214	$ 32,694
Weighted-average number of common shares outstanding – basic (shares)									26,844,545	26,719,626	24,485,078
Share-based compensation plans (shares)									1,516,297	968,671	464,054
Warrants (shares)									324,097	250,707	198,520
Weighted-average number of common shares – diluted (shares)									28,684,939	27,939,004	25,147,652
Basic earnings per share (usd per share)	$ 0.62	$ 0.53	$ 0.41	$ 0.52	$ 0.49	$ 0.44	$ 0.38	$ 0.30	$ 2.09	$ 1.62	$ 1.34
Diluted earnings per share (usd per share)	$ 0.58	$ 0.50	$ 0.39	$ 0.49	$ 0.47	$ 0.42	$ 0.37	$ 0.29	$ 1.96	$ 1.55	$ 1.30