Earnings per Common Share - Computation of Basic and Diluted Earnings per Common Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Basic
Net income	$ 3,014	$ 3,596	$ 10,003	$ 8,231
Preferred stock dividends	299	308	602	627
Net income available to common shareholders	$ 2,715	$ 3,288	$ 9,401	$ 7,604
Weighted average common shares outstanding for basic earnings per common share	10,470,839	10,162,528	10,342,763	9,634,363
Basic earnings per common share	$ 0.26	$ 0.32	$ 0.91	$ 0.79
Diluted
Net income available to common shareholders—basic	$ 2,715	$ 3,288	$ 9,401	$ 7,604
Preferred stock dividends	299	308	602	627
Net income available to common shareholders—diluted	$ 3,014	$ 3,596	$ 10,003	$ 8,231
Weighted average common shares outstanding for basic earnings per common share	10,470,839	10,162,528	10,342,763	9,634,363
Add: Dilutive effects of convertible preferred shares	2,144,497	2,431,349	2,263,652	2,469,465
Average shares and dilutive potential common shares outstanding—diluted	12,615,336	12,593,877	12,606,415	12,103,828
Diluted earnings per common share	$ 0.24	$ 0.29	$ 0.79	$ 0.68