Loans and Leases - Average Recorded Investment in Impaired Loans and Leases and Analysis of Interest on Impaired Loans (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	$ 56,408	$ 44,651	$ 55,305	$ 43,556
Interest Income Recognized	470	228	1,372	604
Additional Interest Income That Would Have Been Recognized Under Original Terms	293	417	891	1,293
Commercial, Financial and Agricultural [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	16,577	5,971	14,806	3,985
Interest Income Recognized	150	29	401	45
Additional Interest Income That Would Have Been Recognized Under Original Terms	72	70	188	132
Real Estate-Commercial [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	26,531	22,789	25,734	23,138
Interest Income Recognized	281	171	816	473
Additional Interest Income That Would Have Been Recognized Under Original Terms	82	150	248	566
Real Estate-Construction [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	9,982	14,544	11,499	15,291
Interest Income Recognized	20	25	103	81
Additional Interest Income That Would Have Been Recognized Under Original Terms	116	184	363	553
Real Estate-Residential Secured for Business Purpose [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	2,643	585	2,400	341
Interest Income Recognized	19	2	52	2
Additional Interest Income That Would Have Been Recognized Under Original Terms	13	2	48	7
Real Estate-Residential Secured for Personal Purpose [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	590	725	779	758
Interest Income Recognized	0	0	0	0
Additional Interest Income That Would Have Been Recognized Under Original Terms	9	11	41	35
Real Estate-Home Equity Secured for Personal Purpose [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	84	0	82	2
Interest Income Recognized	0	0	0	0
Additional Interest Income That Would Have Been Recognized Under Original Terms	1	0	3	0
Loans to Individuals [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	1	37	5	41
Interest Income Recognized	0	1	0	3
Additional Interest Income That Would Have Been Recognized Under Original Terms	$ 0	$ 0	$ 0	$ 0