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, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Basic
Net income	$ 7,682	$ 7,708	$ 22,019	$ 26,038
Preferred stock dividends		162	0	490
Net income available to common shareholders	$ 7,682	$ 7,546	$ 22,019	$ 25,548
Weighted average common shares outstanding for basic earnings per common share	16,045,544	15,577,371	16,201,898	15,604,410
Basic earnings per common share	$ 0.48	$ 0.48	$ 1.36	$ 1.64
Diluted
Net income available to common shareholders—basic	$ 7,682	$ 7,546	$ 22,019	$ 25,548
Preferred stock dividends		162	0	490
Net income available to common shareholders—diluted	$ 7,682	$ 7,708	$ 22,019	$ 26,038
Weighted average common shares outstanding for basic earnings per common share	16,045,544	15,577,371	16,201,898	15,604,410
Add: Dilutive effects of convertible preferred shares		1,272,516		1,286,876
Average shares and dilutive potential common shares outstanding—diluted	16,045,544	16,849,887	16,201,898	16,891,286
Diluted earnings per common share	$ 0.48	$ 0.46	$ 1.36	$ 1.54