Quarterly Results of Operations (Unaudited) - Summary of Quarterly Consolidated Results of Operations (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Interest income	$ 23,790	$ 23,578	$ 21,127	$ 20,093	$ 19,765	$ 19,851	$ 20,122	$ 16,467	$ 88,588	$ 76,205	$ 74,886
Interest expense	3,568	3,802	3,277	3,207	3,242	3,451	3,334	3,195	13,854	13,222	13,503
Net interest income	20,222	19,776	17,850	16,886	16,523	16,400	16,788	13,272	74,734	62,983	61,383
Provision for loan losses	342	300	1,906	614	978	1,741	339		3,162	3,058	1,920
Gain on sale of securities	65			124		988			189	988	374
Net income	6,175	4,288	4,728	5,358	4,948	4,958	4,778	3,417	20,549	18,101	19,876
Net income available to common shareholders	$ 6,144	$ 4,257	$ 4,697	$ 5,327	$ 4,917	$ 4,918	$ 4,747	$ 3,386	$ 20,424	$ 17,968	$ 19,506
Earnings per share:
Basic	$ 0.51	$ 0.37	$ 0.51	$ 0.58	$ 0.53	$ 0.53	$ 0.52	$ 0.39	$ 1.94	$ 1.98	$ 2.26
Diluted	$ 0.51	$ 0.36	$ 0.49	$ 0.55	$ 0.51	$ 0.51	$ 0.50	$ 0.38	$ 1.89	$ 1.90	$ 2.17
Average shares outstanding:
Basic	11,937,247	11,605,976	9,240,005	9,216,011	9,212,156	9,208,707	9,182,986	8,630,966	10,510,296	9,060,702	8,619,330
Diluted	12,013,743	11,893,254	9,637,586	9,609,506	9,628,240	9,588,332	9,560,939	9,021,786	10,798,208	9,454,125	9,000,963