Earnings Per Share - Components of Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Net income available to common shareholders	$ 23,911	$ 23,451	$ 5,681	$ 11,825	$ 14,247	$ 2,414	$ 20,048	$ 20,527	$ 64,868	$ 57,236	$ 64,378
Weighted-average number of common shares outstanding – basic (shares)									31,183,841	31,570,118	30,659,320
Share-based compensation plans (shares)									462,375	658,739	1,917,451
Warrants (shares)									0	4,241	19,906
Weighted-average number of common shares – diluted (shares)									31,646,216	32,233,098	32,596,677
Basic earnings per common share (usd per share)	$ 0.76	$ 0.75	$ 0.18	$ 0.38	$ 0.45	$ 0.08	$ 0.64	$ 0.65	$ 2.08	$ 1.81	$ 2.10
Diluted earnings per share (usd per share)	$ 0.75	$ 0.74	$ 0.18	$ 0.38	$ 0.44	$ 0.07	$ 0.62	$ 0.64	$ 2.05	$ 1.78	$ 1.97