Quarterly Financial Information - Summary of Quarterly Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Interest income	$ 24,849	$ 24,048	$ 23,553	$ 21,060	$ 18,495	$ 17,815	$ 17,399	$ 17,020	$ 93,510	$ 70,729	$ 65,635
Interest expenses	3,969	3,545	3,059	2,584	2,161	2,055	2,065	2,147	13,157	8,428	9,113
Net interest income	20,880	20,503	20,494	18,476	16,334	15,760	15,334	14,873	80,353	62,301	56,522
Provision (recovery) for loan losses	1,215	721	842	1,475	1,493	1,344	395	2,155	4,253	5,387	2,135
Net interest income after provision for loan losses	19,665	19,782	19,652	17,001	14,841	14,416	14,939	12,718	76,100	56,914	54,387
Non-interest income	6,460	6,305	7,090	5,384	5,635	6,003	5,780	4,658	25,239	22,076	19,717
Non-interest expenses	17,329	15,464	15,176	20,290	13,717	12,978	12,860	12,464	68,259	52,019	49,929
Income before income taxes	8,796	10,623	11,566	2,095	6,759	7,441	7,859	4,912	33,080	26,971	24,175
Income tax expense (benefit)	4,294	3,067	3,377	557	1,734	2,288	2,529	1,592	11,295	8,143	7,893
Net income	$ 4,502	$ 7,556	$ 8,189	$ 1,538	$ 5,025	$ 5,153	$ 5,330	$ 3,320	$ 21,785	$ 18,828	$ 16,282
Earnings per share:
Basic earnings	$ 0.09	$ 0.15	$ 0.16	$ 0.03	$ 0.11	$ 0.11	$ 0.11	$ 0.07	$ 0.44	$ 0.40	$ 0.34
Diluted earnings	$ 0.09	$ 0.15	$ 0.16	$ 0.03	$ 0.11	$ 0.11	$ 0.11	$ 0.07	$ 0.44	$ 0.40	$ 0.34