Quarterly Financial Data - Schedule of Quarterly Financial Data (Detail) (USD $) In Thousands, except Per 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	$ 19,172	$ 19,457	$ 19,461	$ 19,489	$ 19,988	$ 19,977	$ 20,258	$ 20,431	$ 77,579	$ 80,654	$ 85,468
Interest expense	1,080	1,138	1,353	1,546	1,838	1,958	2,111	2,267	5,117	8,174	10,728
Net interest income	18,092	18,319	18,108	17,943	18,150	18,019	18,147	18,164	72,462	72,480	74,740
Provision for loan and lease losses	1,614	4,094	3,446	2,074	2,382	2,210	1,343	4,100	11,228	10,035	17,479
Net interest income after provision for loan and lease losses	16,478	14,225	14,662	15,869	15,768	15,809	16,804	14,064	61,234	62,445	57,261
Noninterest income	11,116	13,202	10,991	11,475	10,378	10,861	8,000	11,021	46,784	40,260	34,407
Noninterest expense	21,623	19,988	19,286	20,236	19,712	19,058	18,636	18,876	81,133	76,282	68,010
Income before income taxes	5,971	7,439	6,367	7,108	6,434	7,612	6,168	6,209	26,885	26,423	23,658
Income taxes	1,049	1,400	1,537	1,710	1,358	1,842	1,405	946	5,696	5,551	4,776
Net income	$ 4,922	$ 6,039	$ 4,830	$ 5,398	$ 5,076	$ 5,770	$ 4,763	$ 5,263	$ 21,189	$ 20,872	$ 18,882
Net income per share data:
Basic	$ 0.30	$ 0.36	$ 0.29	$ 0.32	$ 0.30	$ 0.34	$ 0.28	$ 0.31	$ 1.28	$ 1.25	$ 1.13
Diluted	$ 0.30	$ 0.36	$ 0.29	$ 0.32	$ 0.30	$ 0.34	$ 0.28	$ 0.31	$ 1.27	$ 1.24	$ 1.13
Dividends declared	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.80	$ 0.80	$ 0.80