Earnings per Common Share - Computation of Basic and Diluted Earnings per Common Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Basic
Net income	$ 3,660	$ 3,680	$ 11,892	$ 13,586
Preferred stock dividends	308	374	935	1,156
Net income available to common shareholders	$ 3,352	$ 3,306	$ 10,957	$ 12,430
Weighted average common shares outstanding for basic earnings per common share	10,170,734	8,042,303	9,815,118	7,922,170
Basic earnings per common share	$ 0.33	$ 0.41	$ 1.12	$ 1.57
Diluted
Net income available to common shareholders—basic	$ 3,352	$ 3,306	$ 10,957	$ 12,430
Preferred stock dividends	308	374	935	1,156
Net income available to common shareholders—diluted	$ 3,660	$ 3,680	$ 11,892	$ 13,586
Weighted average common shares outstanding for basic earnings per common share	10,170,734	8,042,303	9,815,118	7,922,170
Add: Dilutive effects of convertible preferred shares	2,426,565	2,922,609	2,455,008	3,024,712
Average shares and dilutive potential common shares outstanding—diluted	12,597,299	10,964,912	12,270,126	10,946,882
Diluted earnings per common share	$ 0.29	$ 0.34	$ 0.97	$ 1.24