Loans and Allowance for Loan Losses - Summary of Financial Receivable Nonaccrual Basis (Detail) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Excluding Purchased Non-Covered and Covered Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 26,729,000	$ 29,203,000	$ 37,476,000
Purchased Non-Covered Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	15,318,000	6,659,000
Covered Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	59,781,000	69,152,000	98,515,000
Commercial, Financial and Agricultural [Member] | Excluding Purchased Non-Covered and Covered Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	3,008,000	4,103,000	3,756,000
Commercial, Financial and Agricultural [Member] | Purchased Non-Covered Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	117,000	11,000
Commercial, Financial and Agricultural [Member] | Covered Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	10,025,000	7,257,000	8,718,000
Real Estate - Construction and Development [Member] | Excluding Purchased Non-Covered and Covered Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	4,080,000	3,971,000	9,390,000
Real Estate - Construction and Development [Member] | Purchased Non-Covered Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	1,131,000	325,000
Real Estate - Construction and Development [Member] | Covered Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	14,780,000	14,781,000	18,956,000
Real Estate - Commercial and Farmland [Member] | Excluding Purchased Non-Covered and Covered Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	8,550,000	8,566,000	9,798,000
Real Estate - Commercial and Farmland [Member] | Purchased Non-Covered Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	6,829,000	1,653,000
Real Estate - Commercial and Farmland [Member] | Covered Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	24,285,000	33,495,000	47,580,000
Real Estate - Residential [Member] | Excluding Purchased Non-Covered and Covered Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	10,631,000	12,152,000	13,840,000
Real Estate - Residential [Member] | Purchased Non-Covered Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	7,208,000	4,658,000
Real Estate - Residential [Member] | Covered Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	10,558,000	13,278,000	23,018,000
Consumer Installment Loans [Member] | Excluding Purchased Non-Covered and Covered Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	460,000	411,000	692,000
Consumer Installment Loans [Member] | Purchased Non-Covered Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	33,000	12,000
Consumer Installment Loans [Member] | Covered Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 133,000	$ 341,000	$ 243,000