Loans - Summary of Purchased Non-Covered Loans According to Loan Type (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total non-covered loans	$ 22,212	$ 22,377	$ 23,854
Purchased Non-Covered Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total non-covered loans	673,724	448,753
Purchased Non-Covered Loans [Member] | Commercial, Financial and Agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total non-covered loans	38,077	32,141
Purchased Non-Covered Loans [Member] | Real Estate - Construction and Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total non-covered loans	60,262	31,176
Purchased Non-Covered Loans [Member] | Real Estate - Commercial and Farmland [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total non-covered loans	296,790	179,898
Purchased Non-Covered Loans [Member] | Real Estate - Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total non-covered loans	273,347	200,851
Purchased Non-Covered Loans [Member] | Consumer Installment Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total non-covered loans	$ 5,248	$ 4,687