Loans - Summary of Troubled Debt Restructuring by Loan Class, Defaulted under Restructured Terms (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015 Contract	Dec. 31, 2014	Mar. 31, 2014 Contract
Financing Receivable, Modifications [Line Items]
Number of contracts	14		10
Troubled debt restructuring loans	$ 1,519	$ 1,212	$ 2,241
Commercial, Financial & Agricultural [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	1
Troubled debt restructuring loans	5
Real Estate - Construction & Development [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts			2
Troubled debt restructuring loans			40
Commercial And Farmland [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	3		4
Troubled debt restructuring loans	746		1,897
Real Estate - Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	6		3
Troubled debt restructuring loans	748		280
Consumer Installment Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	4		1
Troubled debt restructuring loans	$ 20		$ 24