Quarterly Results of Operations (Unaudited) - Summary of Quarterly Consolidated Results of Operations (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Quarterly Financial Information Disclosure [Abstract]
Interest income	$ 17,436	$ 18,041	$ 19,977	$ 19,429	$ 20,460	$ 18,719	$ 16,523	$ 16,826	$ 74,886	$ 72,528	$ 64,614
Interest expense	3,310	3,372	3,402	3,419	3,457	3,720	3,517	3,628	13,503	14,322	16,501
Net interest income	14,126	14,669	16,575	16,010	17,003	14,999	13,006	13,198	61,383	58,206	48,113
Provision for loan losses	(997)	104	729	2,084	1,715	1,041	209	559	1,920	3,524	5,282
Gain (loss) on sale of securities		6		368		2			374	2	1,777
Net income	4,115	4,785	5,665	5,311	5,170	4,850	4,910	4,613	19,876	19,543	12,797
Net income available to common shareholders	$ 4,052	$ 4,719	$ 5,569	$ 5,165	$ 5,014	$ 4,787	$ 4,804	$ 4,457	$ 19,506	$ 19,062	$ 11,472
Earnings per share:
Basic	$ 0.47	$ 0.55	$ 0.65	$ 0.60	$ 0.58	$ 0.56	$ 0.65	$ 0.60	$ 2.26	$ 2.39	$ 1.55
Diluted	$ 0.45	$ 0.52	$ 0.62	$ 0.58	$ 0.56	$ 0.54	$ 0.62	$ 0.59	$ 2.17	$ 2.30	$ 1.51
Average shares outstanding:
Basic	8,623,360	8,618,969	8,617,466	8,617,466	8,617,466	8,503,475	7,434,537	7,422,860	8,619,330	7,974,241	7,407,258
Diluted	9,020,289	9,019,211	8,974,103	8,980,655	8,964,315	8,838,659	7,728,519	7,598,490	9,000,963	8,271,177	7,588,394