Loans and Leases - Tables for Impaired Loans (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	$ 55,761	$ 48,241	$ 43,242
Interest Income Recognized	1,863	1,156	552
Additional Interest Income That Would Have Been Recognized Under Original Terms	1,164	1,652	2,161
Commercial, Financial and Agricultural [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	15,334	6,412	5,189
Interest Income Recognized	540	172	82
Additional Interest Income That Would Have Been Recognized Under Original Terms	258	200	288
Real Estate-Commercial [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	26,662	25,728	20,756
Interest Income Recognized	1,143	837	348
Additional Interest Income That Would Have Been Recognized Under Original Terms	323	717	1,086
Real Estate-Construction [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	10,412	14,621	16,207
Interest Income Recognized	103	124	117
Additional Interest Income That Would Have Been Recognized Under Original Terms	463	680	763
Real Estate-Residential Secured for Business Purpose [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	2,524	672	156
Interest Income Recognized	77	19	0
Additional Interest Income That Would Have Been Recognized Under Original Terms	61	10	7
Real Estate-Residential Secured for Personal Purpose [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	719	760	293
Interest Income Recognized	0	0	0
Additional Interest Income That Would Have Been Recognized Under Original Terms	49	45	17
Real Estate-Home Equity Secured for Personal Purpose [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	106	8	2
Interest Income Recognized	0	0	0
Additional Interest Income That Would Have Been Recognized Under Original Terms	10	0	0
Loans to Individuals [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	4	40	47
Interest Income Recognized	0	4	5
Additional Interest Income That Would Have Been Recognized Under Original Terms	$ 0	$ 0	$ 0