Earnings per Common Share - Computation of Basic and Diluted Earnings per Common Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Basic
Net income	$ 6,989	$ 4,635
Preferred stock dividends	303	319
Net income available to common shareholders	$ 6,686	$ 4,316
Weighted average common shares outstanding for basic earnings per common share	10,213,264	9,100,330
Basic earnings per common share	$ 0.65	$ 0.47
Diluted
Net income available to common shareholders—basic	$ 6,686	$ 4,316
Preferred stock dividends	303	319
Net income available to common shareholders—diluted	$ 6,989	$ 4,635
Weighted average common shares outstanding for basic earnings per common share	10,213,264	9,100,330
Add: Dilutive effects of convertible preferred shares	2,384,130	2,508,003
Average shares and dilutive potential common shares outstanding—diluted	12,597,394	11,608,333
Diluted earnings per common share	$ 0.55	$ 0.40