Selected Financial Data - Summary of Selected 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	$ 38,779	$ 38,581	$ 38,553	$ 37,843	$ 38,920	$ 38,820	$ 39,370	$ 39,140	$ 139,193	$ 135,227	$ 137,346
Interest expense	3,125	3,307	3,957	4,174	4,629	5,025	5,551	5,819	14,563	21,024	27,733
Provision for loan losses	1,562	3,419	1,023	2,307	4,215	2,305	7,023	9,272	8,311	22,815	15,609
Net Interest Income After Provision for Loan Losses	34,092	31,855	33,573	31,362	30,076	31,490	26,796	24,049	130,882	112,412	121,737
Security gains, net		3		2		2,170	6	840
Noninterest income	11,312	12,539	12,867	14,804	11,565	12,576	12,525	12,229	51,527	51,912	44,057
Noninterest expense	29,447	27,943	28,386	31,616	29,717	31,018	29,344	32,783	117,392	122,863	103,908
Income before taxes	15,957	16,454	18,054	14,552	11,924	15,218	9,983	4,335
Provision for income taxes	4,098	4,207	3,951	2,222	2,400	2,623	1,383	855	14,478	7,261	14,622
Net Income Allocated to Common Shareholders	$ 11,859	$ 12,247	$ 14,103	$ 12,330	$ 9,524	$ 12,595	$ 8,600	$ 3,480	$ 50,392	$ 34,074	$ 39,523
Common earnings per share-diluted	$ 0.40	$ 0.41	$ 0.47	$ 0.41	$ 0.32	$ 0.43	$ 0.30	$ 0.12	$ 1.70	$ 1.18	$ 1.41
Dividends declared per common share	$ 0.16	$ 0.15	$ 0.15	$ 0.15	$ 0.15	$ 0.15	$ 0.15	$ 0.15	$ 0.61	$ 0.60	$ 0.60
Common book value	$ 19.21	$ 18.68	$ 18.39	$ 18.32	$ 18.08	$ 17.97	$ 17.65	$ 17.47