Loans and Leases - Troubled debt restructured loans (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]
Financing Receivable, Modifications [Line Items]
Number of Loans	1	2	1	14
Pre-Restructuring Outstanding Recorded Investment	$ 1,000	$ 310	$ 1,000	$ 4,011
Post-Restructuring Outstanding Recorded Investment	1,000	310	1,000	4,011
Related Allowance
Accruing Troubled Debt Restructured Loans [Member] | Commercial, financial and agricultural [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	1	1	1	8
Pre-Restructuring Outstanding Recorded Investment	1,000	135	1,000	1,672
Post-Restructuring Outstanding Recorded Investment	1,000	135	1,000	1,672
Related Allowance
Accruing Troubled Debt Restructured Loans [Member] | Real estate-commercial real estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans		1		4
Pre-Restructuring Outstanding Recorded Investment		175		1,009
Post-Restructuring Outstanding Recorded Investment		175		1,009
Related Allowance
Accruing Troubled Debt Restructured Loans [Member] | Real estate-construction [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans				2
Pre-Restructuring Outstanding Recorded Investment				1,330
Post-Restructuring Outstanding Recorded Investment				1,330
Related Allowance
Nonaccrual Troubled Debt Restructured Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans				3
Pre-Restructuring Outstanding Recorded Investment				572
Post-Restructuring Outstanding Recorded Investment				572
Related Allowance
Nonaccrual Troubled Debt Restructured Loans [Member] | Commercial, financial and agricultural [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans				2
Pre-Restructuring Outstanding Recorded Investment				448
Post-Restructuring Outstanding Recorded Investment				448
Related Allowance
Nonaccrual Troubled Debt Restructured Loans [Member] | Real estate-commercial real estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans				1
Pre-Restructuring Outstanding Recorded Investment				124
Post-Restructuring Outstanding Recorded Investment				124
Related Allowance