Summary of Quarterly Earnings (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
Schedule Of Quarterly Financial Information [Line Items]
Interest income	$ 27,364	$ 26,696	$ 27,412	$ 28,004	$ 31,256	$ 31,536	$ 24,182	$ 22,682	$ 109,476	$ 109,656	$ 94,176
Interest expense	4,272	4,370	4,550	4,642	5,120	5,077	4,698	4,705	17,834	19,600	22,147
Net interest income	23,092	22,326	22,862	23,362	26,136	26,459	19,484	17,977	91,642	90,056	72,029
Provision for loan losses	1,528	2,333	3,205	1,142	1,220	1,916	1,620	922	8,208	5,678	9,047
Net interest income after provision for loan losses	21,564	19,993	19,657	22,220	24,916	24,543	17,864	17,055	83,434	84,378	62,982
Other income	6,743	8,150	6,735	7,744	9,000	10,935	8,352	7,940	5,235	6,742	3,888
Net gain (loss) on sale of securities	208	(39)	113	117	213	228	(9)	51	399	483	5,264
Other expenses	20,755	20,153	18,533	19,544	21,733	20,325	20,132	16,193	23,249	21,190	20,305
Income before income taxes	7,760	7,951	7,972	10,537	12,396	15,381	6,075	8,853	34,220	42,705	29,601
Income tax	2,436	2,539	2,537	3,396	3,957	5,322	1,997	2,852	10,908	14,128	9,573
Net income	5,324	5,412	5,435	7,141	8,439	10,059	4,078	6,001	23,312	28,577	20,028
Dividends on preferred stock	252	261	253	258	272	220	283	283	1,024	1,058	703
Net income available to common shareholders	$ 5,072	$ 5,151	$ 5,182	$ 6,883	$ 8,167	$ 9,839	$ 3,795	$ 5,718	$ 22,288	$ 27,519	$ 19,325
Basic earnings per common share	$ 0.27	$ 0.26	$ 0.26	$ 0.34	$ 0.41	$ 0.49	$ 0.20	$ 0.32	$ 1.13	$ 1.44	$ 1.08
Diluted earnings per common share	$ 0.26	$ 0.26	$ 0.26	$ 0.34	$ 0.40	$ 0.47	$ 0.21	$ 0.31	$ 1.11	$ 1.40	$ 1.07
Dividend per common share	$ 0.12	$ 0.12	$ 0.12	$ 0.12	$ 0.11	$ 0.11	$ 0.11	$ 0.10	$ 0.48	$ 0.43	$ 0.40
Weighted average basic shares outstanding	19,136,317	20,008,861	19,997,991	20,032,694	20,063,873	20,013,264	18,561,714	17,849,376	19,792,099	19,127,065	17,877,421
Weighted average diluted shares outstanding	20,233,737	21,123,788	21,205,078	21,258,490	21,314,023	21,329,612	19,872,106	19,158,179	20,961,800	20,419,569	18,687,521