Merger - Business Acquisition Pro Forma Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Business Combination, Separately Recognized Transactions [Line Items]
Net interest income after provision for loan losses	$ 12,002	$ 10,684	$ 34,031	$ 29,615
Noninterest income	3,076	3,012	11,132	11,016
Net income	$ 3,253	$ 2,306	$ 9,546	$ 7,257
Basic	$ 0.36	$ 0.25	$ 1.07	$ 0.75
Diluted	$ 0.30	$ 0.21	$ 0.87	$ 0.64
Pro Forma [Member]
Business Combination, Separately Recognized Transactions [Line Items]
Net interest income after provision for loan losses	$ 12,974	$ 30,677	$ 36,951	$ 32,799
Noninterest income	3,076	3,093	11,624	11,376
Net income	$ 3,599	$ 2,418	$ 9,645	$ 7,820
Basic	$ 0.41	$ 0.26	$ 1.13	$ 0.88
Diluted	$ 0.33	$ 0.22	$ 0.88	$ 0.69