Loans and Leases - Concessions granted on accruing and nonaccrual loans restructured (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013 Loans	Jun. 30, 2012 Loans	Jun. 30, 2013 Loans	Jun. 30, 2012 Loans
Accruing Troubled Debt Restructured Loans [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	1	2	1	14
Amount	$ 1,000	$ 310	$ 1,000	$ 4,011
Accruing Troubled Debt Restructured Loans [Member] | Commercial, financial and agricultural [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	1	1	1	8
Amount	1,000	135	1,000	1,672
Accruing Troubled Debt Restructured Loans [Member] | Real estate-commercial real estate [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans		1		4
Amount		175		1,009
Accruing Troubled Debt Restructured Loans [Member] | Real estate-construction [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans				2
Amount				1,330
Nonaccrual Troubled Debt Restructured Loans [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans				3
Amount				572
Nonaccrual Troubled Debt Restructured Loans [Member] | Commercial, financial and agricultural [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans				2
Amount				448
Nonaccrual Troubled Debt Restructured Loans [Member] | Real estate-commercial real estate [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans				1
Amount				124
Interest Only Term Extension [Member] | Accruing Troubled Debt Restructured Loans [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	1		1	8
Amount	1,000		1,000	3,293
Interest Only Term Extension [Member] | Accruing Troubled Debt Restructured Loans [Member] | Commercial, financial and agricultural [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	1		1	4
Amount	1,000		1,000	1,316
Interest Only Term Extension [Member] | Accruing Troubled Debt Restructured Loans [Member] | Real estate-commercial real estate [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans				2
Amount				647
Interest Only Term Extension [Member] | Accruing Troubled Debt Restructured Loans [Member] | Real estate-construction [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans				2
Amount				1,330
Interest Only Term Extension [Member] | Nonaccrual Troubled Debt Restructured Loans [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans
Amount
Interest Only Term Extension [Member] | Nonaccrual Troubled Debt Restructured Loans [Member] | Commercial, financial and agricultural [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans
Amount
Interest Only Term Extension [Member] | Nonaccrual Troubled Debt Restructured Loans [Member] | Real estate-commercial real estate [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans
Amount
Temporary Payment Reduction [Member] | Accruing Troubled Debt Restructured Loans [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans				4
Amount				408
Temporary Payment Reduction [Member] | Accruing Troubled Debt Restructured Loans [Member] | Commercial, financial and agricultural [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans				3
Amount				221
Temporary Payment Reduction [Member] | Accruing Troubled Debt Restructured Loans [Member] | Real estate-commercial real estate [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans				1
Amount				187
Temporary Payment Reduction [Member] | Accruing Troubled Debt Restructured Loans [Member] | Real estate-construction [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans
Amount
Temporary Payment Reduction [Member] | Nonaccrual Troubled Debt Restructured Loans [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans
Amount
Temporary Payment Reduction [Member] | Nonaccrual Troubled Debt Restructured Loans [Member] | Commercial, financial and agricultural [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans
Amount
Temporary Payment Reduction [Member] | Nonaccrual Troubled Debt Restructured Loans [Member] | Real estate-commercial real estate [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans
Amount
Temporary Payment Suspension [Member] | Accruing Troubled Debt Restructured Loans [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans
Amount
Temporary Payment Suspension [Member] | Accruing Troubled Debt Restructured Loans [Member] | Commercial, financial and agricultural [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans
Amount
Temporary Payment Suspension [Member] | Accruing Troubled Debt Restructured Loans [Member] | Real estate-commercial real estate [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans
Amount
Temporary Payment Suspension [Member] | Accruing Troubled Debt Restructured Loans [Member] | Real estate-construction [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans
Amount
Temporary Payment Suspension [Member] | Nonaccrual Troubled Debt Restructured Loans [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans				3
Amount				572
Temporary Payment Suspension [Member] | Nonaccrual Troubled Debt Restructured Loans [Member] | Commercial, financial and agricultural [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans				2
Amount				448
Temporary Payment Suspension [Member] | Nonaccrual Troubled Debt Restructured Loans [Member] | Real estate-commercial real estate [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans				1
Amount				124
Maturity Date Extension [Member] | Accruing Troubled Debt Restructured Loans [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans		2		2
Amount		310		310
Maturity Date Extension [Member] | Accruing Troubled Debt Restructured Loans [Member] | Commercial, financial and agricultural [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans		1		1
Amount		135		135
Maturity Date Extension [Member] | Accruing Troubled Debt Restructured Loans [Member] | Real estate-commercial real estate [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans		1		1
Amount		175		175
Maturity Date Extension [Member] | Accruing Troubled Debt Restructured Loans [Member] | Real estate-construction [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans
Amount
Maturity Date Extension [Member] | Nonaccrual Troubled Debt Restructured Loans [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans
Amount
Maturity Date Extension [Member] | Nonaccrual Troubled Debt Restructured Loans [Member] | Commercial, financial and agricultural [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans
Amount
Maturity Date Extension [Member] | Nonaccrual Troubled Debt Restructured Loans [Member] | Real estate-commercial real estate [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans
Amount