Loans - Summary of Troubled Debt Restructurings by Loan Class (Detail) $ in Thousands	6 Months Ended
	Jun. 30, 2015 USD ($) Contract	Jun. 30, 2014 USD ($) Contract
Financing Receivable Troubled Debt Restructuring [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts | Contract	25	26
Troubled debt restructuring loans	$ 782	$ 1,662
Financing Receivable Troubled Debt Restructuring [Member] | Commercial, Financial & Agricultural [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts | Contract	3	2
Troubled debt restructuring loans	$ 18	$ 16
Financing Receivable Troubled Debt Restructuring [Member] | Real Estate - Construction & Development [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts | Contract	2	4
Troubled debt restructuring loans	$ 16	$ 235
Financing Receivable Troubled Debt Restructuring [Member] | Real Estate - Commercial & Farmland [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts | Contract		3
Troubled debt restructuring loans		$ 1,037
Financing Receivable Troubled Debt Restructuring [Member] | Real Estate - Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts | Contract	15	6
Troubled debt restructuring loans	$ 729	$ 328
Financing Receivable Troubled Debt Restructuring [Member] | Consumer Installment Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts | Contract	5	11
Troubled debt restructuring loans	$ 19	$ 46
Purchased Non-Covered Loans [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructuring loans	$ 1,000
Purchased Non-Covered Loans [Member] | Real Estate - Commercial & Farmland [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts | Contract	5
Troubled debt restructuring loans	$ 1,017
Purchased Non-Covered Loans [Member] | Real Estate - Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts | Contract	1
Troubled debt restructuring loans	$ 5
Purchased Non-Covered Loans [Member] | Consumer Installment Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts | Contract	6
Troubled debt restructuring loans	$ 1,022
Covered Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts | Contract	15	31
Troubled debt restructuring loans	$ 1,212	$ 2,577
Covered Loans [Member] | Commercial, Financial & Agricultural [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts | Contract	1
Troubled debt restructuring loans	$ 1
Covered Loans [Member] | Real Estate - Construction & Development [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts | Contract	2	2
Troubled debt restructuring loans	$ 34	$ 28
Covered Loans [Member] | Real Estate - Commercial & Farmland [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts | Contract	4	5
Troubled debt restructuring loans	$ 796	$ 1,024
Covered Loans [Member] | Real Estate - Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts | Contract	6	24
Troubled debt restructuring loans	$ 376	$ 1,525
Covered Loans [Member] | Consumer Installment Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts | Contract	2
Troubled debt restructuring loans	$ 5