Loans - Summary of Financial Receivable Nonaccrual Basis (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013
Excluding Purchased Non-Covered and Covered Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 22,810,000	$ 29,203,000	$ 31,720,000
Excluding Purchased Non-Covered and Covered Loans [Member] | Commercial, Financial and Agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	2,695,000	4,103,000	4,198,000
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Construction and Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	3,037,000	3,971,000	4,229,000
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Commercial and Farmland [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	8,983,000	8,566,000	9,548,000
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	7,608,000	12,152,000	13,303,000
Excluding Purchased Non-Covered and Covered Loans [Member] | Consumer Installment Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	487,000	411,000	442,000
Purchased Non-Covered Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	17,007,000	6,659,000
Purchased Non-Covered Loans [Member] | Commercial, Financial and Agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	54,000	11,000
Purchased Non-Covered Loans [Member] | Real Estate - Construction and Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	1,969,000	325,000
Purchased Non-Covered Loans [Member] | Real Estate - Commercial and Farmland [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	8,776,000	1,653,000
Purchased Non-Covered Loans [Member] | Real Estate - Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	6,132,000	4,658,000
Purchased Non-Covered Loans [Member] | Consumer Installment Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	76,000	12,000
Covered Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	39,283,000	69,152,000	74,911,000
Covered Loans [Member] | Commercial, Financial and Agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	8,441,000	7,257,000	7,872,000
Covered Loans [Member] | Real Estate - Construction and Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	8,896,000	14,781,000	16,582,000
Covered Loans [Member] | Real Estate - Commercial and Farmland [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	14,617,000	33,495,000	37,079,000
Covered Loans [Member] | Real Estate - Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	7,227,000	13,278,000	13,028,000
Covered Loans [Member] | Consumer Installment Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 102,000	$ 341,000	$ 350,000