Loans - Summary of Trouble Debt Restructurings by Loan Class of Purchased Non-Covered Loans (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Financing Receivable Modifications Number Of Contracts [Line Items]
Troubled debt restructuring loans	$ 21,200	$ 20,900	$ 23,300
Purchased Non-Covered Loans [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Troubled debt restructuring loans	5,191	5,938
Purchased Non-Covered Loans [Member] | Accruing Loans [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Number of contracts	22	24
Troubled debt restructuring loans	5,191	5,938
Purchased Non-Covered Loans [Member] | Accruing Loans [Member] | Commercial, Financial and Agricultural [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Number of contracts
Troubled debt restructuring loans
Purchased Non-Covered Loans [Member] | Accruing Loans [Member] | Real Estate - Construction and Development [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Number of contracts	7	10
Troubled debt restructuring loans	2,443	3,364
Purchased Non-Covered Loans [Member] | Accruing Loans [Member] | Real Estate - Commercial and Farmland [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Number of contracts	2	3
Troubled debt restructuring loans	961	1,228
Purchased Non-Covered Loans [Member] | Accruing Loans [Member] | Real Estate - Residential [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Number of contracts	12	8
Troubled debt restructuring loans	1,779	1,321
Purchased Non-Covered Loans [Member] | Accruing Loans [Member] | Consumer Installment Loans [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Number of contracts	1	3
Troubled debt restructuring loans	8	25
Purchased Non-Covered Loans [Member] | Non-Accruing Loans [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Number of contracts	11	10
Troubled debt restructuring loans	1,268	1,212
Purchased Non-Covered Loans [Member] | Non-Accruing Loans [Member] | Commercial, Financial and Agricultural [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Number of contracts	1	1
Troubled debt restructuring loans	6	6
Purchased Non-Covered Loans [Member] | Non-Accruing Loans [Member] | Real Estate - Construction and Development [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Number of contracts	2
Troubled debt restructuring loans	264
Purchased Non-Covered Loans [Member] | Non-Accruing Loans [Member] | Real Estate - Commercial and Farmland [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Number of contracts	2	1
Troubled debt restructuring loans	726	468
Purchased Non-Covered Loans [Member] | Non-Accruing Loans [Member] | Real Estate - Residential [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Number of contracts	4	8
Troubled debt restructuring loans	255	738
Purchased Non-Covered Loans [Member] | Non-Accruing Loans [Member] | Consumer Installment Loans [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Number of contracts	2
Troubled debt restructuring loans	$ 17