Loans and Leases - Concessions Granted on Accruing and Nonaccrual Loans Restructured (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014 Loans	Dec. 31, 2013 Loans
Accrual Troubled Debt Restructuring Loans [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	7	6
Amount	$ 2,824	$ 3,053
Accrual Troubled Debt Restructuring Loans [Member] | Interest Only Term Extension [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	0	1
Amount	0	1,000
Accrual Troubled Debt Restructuring Loans [Member] | Temporary Payment Reduction [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	0	1
Amount	0	756
Accrual Troubled Debt Restructuring Loans [Member] | Interest Rate Reduction [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	0	0
Amount	0	0
Accrual Troubled Debt Restructuring Loans [Member] | Maturity Date Extension [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	6	4
Amount	2,699	1,297
Accrual Troubled Debt Restructuring Loans [Member] | Payments Suspended [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	1	0
Amount	125	0
Nonaccrual Troubled Debt Restructured Loans [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	3	0
Amount	738	0
Nonaccrual Troubled Debt Restructured Loans [Member] | Interest Only Term Extension [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	0	0
Amount	0	0
Nonaccrual Troubled Debt Restructured Loans [Member] | Temporary Payment Reduction [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	0	0
Amount	0	0
Nonaccrual Troubled Debt Restructured Loans [Member] | Interest Rate Reduction [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	2	0
Amount	105	0
Nonaccrual Troubled Debt Restructured Loans [Member] | Maturity Date Extension [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	1	0
Amount	633	0
Nonaccrual Troubled Debt Restructured Loans [Member] | Payments Suspended [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	0	0
Amount	0	0
Commercial, Financial and Agricultural [Member] | Accrual Troubled Debt Restructuring Loans [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	6	2
Amount	1,824	1,025
Commercial, Financial and Agricultural [Member] | Accrual Troubled Debt Restructuring Loans [Member] | Interest Only Term Extension [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	0	1
Amount	0	1,000
Commercial, Financial and Agricultural [Member] | Accrual Troubled Debt Restructuring Loans [Member] | Temporary Payment Reduction [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	0	0
Amount	0	0
Commercial, Financial and Agricultural [Member] | Accrual Troubled Debt Restructuring Loans [Member] | Interest Rate Reduction [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	0	0
Amount	0	0
Commercial, Financial and Agricultural [Member] | Accrual Troubled Debt Restructuring Loans [Member] | Maturity Date Extension [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	5	1
Amount	1,699	25
Commercial, Financial and Agricultural [Member] | Accrual Troubled Debt Restructuring Loans [Member] | Payments Suspended [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	1	0
Amount	125	0
Real Estate-Commercial [Member] | Accrual Troubled Debt Restructuring Loans [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	1	3
Amount	1,000	1,569
Real Estate-Commercial [Member] | Accrual Troubled Debt Restructuring Loans [Member] | Interest Only Term Extension [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	0	0
Amount	0	0
Real Estate-Commercial [Member] | Accrual Troubled Debt Restructuring Loans [Member] | Temporary Payment Reduction [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	0	1
Amount	0	756
Real Estate-Commercial [Member] | Accrual Troubled Debt Restructuring Loans [Member] | Interest Rate Reduction [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	0	0
Amount	0	0
Real Estate-Commercial [Member] | Accrual Troubled Debt Restructuring Loans [Member] | Maturity Date Extension [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	1	2
Amount	1,000	813
Real Estate-Commercial [Member] | Accrual Troubled Debt Restructuring Loans [Member] | Payments Suspended [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	0	0
Amount	0	0
Real Estate-Commercial [Member] | Nonaccrual Troubled Debt Restructured Loans [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	1	0
Amount	50
Real Estate-Commercial [Member] | Nonaccrual Troubled Debt Restructured Loans [Member] | Interest Only Term Extension [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	0
Amount	0
Real Estate-Commercial [Member] | Nonaccrual Troubled Debt Restructured Loans [Member] | Temporary Payment Reduction [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	0
Amount	0
Real Estate-Commercial [Member] | Nonaccrual Troubled Debt Restructured Loans [Member] | Interest Rate Reduction [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	1
Amount	50
Real Estate-Commercial [Member] | Nonaccrual Troubled Debt Restructured Loans [Member] | Maturity Date Extension [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	0
Amount	0
Real Estate-Commercial [Member] | Nonaccrual Troubled Debt Restructured Loans [Member] | Payments Suspended [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	0
Amount	0
Commercial Real Estate Construction Financing Receivable [Member] | Accrual Troubled Debt Restructuring Loans [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	0	1
Amount		459
Commercial Real Estate Construction Financing Receivable [Member] | Accrual Troubled Debt Restructuring Loans [Member] | Interest Only Term Extension [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans		0
Amount		0
Commercial Real Estate Construction Financing Receivable [Member] | Accrual Troubled Debt Restructuring Loans [Member] | Temporary Payment Reduction [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans		0
Amount		0
Commercial Real Estate Construction Financing Receivable [Member] | Accrual Troubled Debt Restructuring Loans [Member] | Interest Rate Reduction [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans		0
Amount		0
Commercial Real Estate Construction Financing Receivable [Member] | Accrual Troubled Debt Restructuring Loans [Member] | Maturity Date Extension [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans		1
Amount		459
Commercial Real Estate Construction Financing Receivable [Member] | Accrual Troubled Debt Restructuring Loans [Member] | Payments Suspended [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans		0
Amount		0
Real Estate-Residential Secured for Business Purpose [Member] | Nonaccrual Troubled Debt Restructured Loans [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	2	0
Amount	688
Real Estate-Residential Secured for Business Purpose [Member] | Nonaccrual Troubled Debt Restructured Loans [Member] | Interest Only Term Extension [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	0
Amount	0
Real Estate-Residential Secured for Business Purpose [Member] | Nonaccrual Troubled Debt Restructured Loans [Member] | Temporary Payment Reduction [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	0
Amount	0
Real Estate-Residential Secured for Business Purpose [Member] | Nonaccrual Troubled Debt Restructured Loans [Member] | Interest Rate Reduction [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	1
Amount	55
Real Estate-Residential Secured for Business Purpose [Member] | Nonaccrual Troubled Debt Restructured Loans [Member] | Maturity Date Extension [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	1
Amount	633
Real Estate-Residential Secured for Business Purpose [Member] | Nonaccrual Troubled Debt Restructured Loans [Member] | Payments Suspended [Member]
Concessions granted on accruing and non-accrual loans restructured
No. of Loans	0
Amount	$ 0