Loans and Leases - Impaired Loans (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Financing Receivable, Impaired [Line Items]
Impaired loans with no related allowance, Recorded Investment	$ 57,747	$ 44,508
Impaired loans with no related allowance, Unpaid Principal Balance	72,007	54,497
Impaired loans with an allowance recorded, Recorded Investment	9,057	676
Impaired loans with an allowance recorded, Unpaid Principal Balance	9,140	717
Total impaired loans, Recorded Investment	66,804	45,184
Total impaired loans, Unpaid Principal Balance	81,147	55,214
Total impaired loans, Related Allowance	3,096	208
Commercial, financial and agricultural [Member]
Financing Receivable, Impaired [Line Items]
Impaired loans with no related allowance, Recorded Investment	8,037	2,646
Impaired loans with no related allowance, Unpaid Principal Balance	9,961	4,504
Impaired loans with an allowance recorded, Recorded Investment	5,992	676
Impaired loans with an allowance recorded, Unpaid Principal Balance	6,075	717
Total impaired loans, Recorded Investment	14,029	3,322
Total impaired loans, Unpaid Principal Balance	16,036	5,221
Total impaired loans, Related Allowance	2,210	208
Real estate-commercial real estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired loans with no related allowance, Recorded Investment	36,500	24,863
Impaired loans with no related allowance, Unpaid Principal Balance	46,604	30,991
Impaired loans with an allowance recorded, Recorded Investment	1,515
Impaired loans with an allowance recorded, Unpaid Principal Balance	1,515
Total impaired loans, Recorded Investment	38,015	24,863
Total impaired loans, Unpaid Principal Balance	48,119	30,991
Total impaired loans, Related Allowance	111
Real estate-construction [Member]
Financing Receivable, Impaired [Line Items]
Impaired loans with no related allowance, Recorded Investment	12,227	15,985
Impaired loans with no related allowance, Unpaid Principal Balance	14,410	17,959
Total impaired loans, Recorded Investment	12,227	15,985
Total impaired loans, Unpaid Principal Balance	14,410	17,959
Total impaired loans, Related Allowance
Real estate-residential secured for business purpose [Member]
Financing Receivable, Impaired [Line Items]
Impaired loans with no related allowance, Recorded Investment	226	172
Impaired loans with no related allowance, Unpaid Principal Balance	238	184
Impaired loans with an allowance recorded, Recorded Investment	1,550
Impaired loans with an allowance recorded, Unpaid Principal Balance	1,550
Total impaired loans, Recorded Investment	1,776	172
Total impaired loans, Unpaid Principal Balance	1,788	184
Total impaired loans, Related Allowance	775
Real estate-residential secured for personal purpose [Member]
Financing Receivable, Impaired [Line Items]
Impaired loans with no related allowance, Recorded Investment	720	804
Impaired loans with no related allowance, Unpaid Principal Balance	739	804
Total impaired loans, Recorded Investment	720	804
Total impaired loans, Unpaid Principal Balance	739	804
Total impaired loans, Related Allowance
Loans to individuals [Member]
Financing Receivable, Impaired [Line Items]
Impaired loans with no related allowance, Recorded Investment	37	38
Impaired loans with no related allowance, Unpaid Principal Balance	55	55
Total impaired loans, Recorded Investment	37	38
Total impaired loans, Unpaid Principal Balance	55	55
Total impaired loans, Related Allowance