Nonaccrual Loans by Loan Class (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Financing Receivable, Impaired [Line Items]
Total nonaccrual loans	$ 18,167	$ 12,994
Commercial Loans \| Construction Development And Other Land
Financing Receivable, Impaired [Line Items]
Total nonaccrual loans	39	18
Commercial Loans \| Commercial and Industrial
Financing Receivable, Impaired [Line Items]
Total nonaccrual loans	124	157
Commercial Loans \| Multi-family Residential
Financing Receivable, Impaired [Line Items]
Total nonaccrual loans	346	245
Commercial Loans \| Single-family Non-owner Occupied
Financing Receivable, Impaired [Line Items]
Total nonaccrual loans	634	678
Commercial Loans \| Non-farm, Non-residential
Financing Receivable, Impaired [Line Items]
Total nonaccrual loans	7,624	3,651
Commercial Loans \| Agricultural
Financing Receivable, Impaired [Line Items]
Total nonaccrual loans		4
Commercial Loans \| Farmland Loan
Financing Receivable, Impaired [Line Items]
Total nonaccrual loans	57
Consumer Real Estate \| Home Equity Lines
Financing Receivable, Impaired [Line Items]
Total nonaccrual loans	1,287	996
Consumer Real Estate \| Single Family Owner Occupied
Financing Receivable, Impaired [Line Items]
Total nonaccrual loans	7,819	7,071
Consumer Real Estate \| Owner Occupied Construction
Financing Receivable, Impaired [Line Items]
Total nonaccrual loans	103	106
Consumer and Other \| Consumer Loan
Financing Receivable, Impaired [Line Items]
Total nonaccrual loans	134	68
Non Covered Loans
Financing Receivable, Impaired [Line Items]
Total nonaccrual loans	15,387	10,556
Non Covered Loans \| Commercial Loans \| Commercial and Industrial
Financing Receivable, Impaired [Line Items]
Total nonaccrual loans	124	123
Non Covered Loans \| Commercial Loans \| Multi-family Residential
Financing Receivable, Impaired [Line Items]
Total nonaccrual loans	346	245
Non Covered Loans \| Commercial Loans \| Single-family Non-owner Occupied
Financing Receivable, Impaired [Line Items]
Total nonaccrual loans	557	601
Non Covered Loans \| Commercial Loans \| Non-farm, Non-residential
Financing Receivable, Impaired [Line Items]
Total nonaccrual loans	6,064	2,334
Non Covered Loans \| Commercial Loans \| Agricultural
Financing Receivable, Impaired [Line Items]
Total nonaccrual loans		4
Non Covered Loans \| Commercial Loans \| Farmland Loan
Financing Receivable, Impaired [Line Items]
Total nonaccrual loans	57
Non Covered Loans \| Consumer Real Estate \| Home Equity Lines
Financing Receivable, Impaired [Line Items]
Total nonaccrual loans	794	792
Non Covered Loans \| Consumer Real Estate \| Single Family Owner Occupied
Financing Receivable, Impaired [Line Items]
Total nonaccrual loans	7,311	6,389
Non Covered Loans \| Consumer and Other \| Consumer Loan
Financing Receivable, Impaired [Line Items]
Total nonaccrual loans	134	68
Covered Loans
Financing Receivable, Impaired [Line Items]
Total nonaccrual loans	2,780	2,438
Covered Loans \| Commercial Loans \| Construction Development And Other Land
Financing Receivable, Impaired [Line Items]
Total nonaccrual loans	39	18
Covered Loans \| Commercial Loans \| Commercial and Industrial
Financing Receivable, Impaired [Line Items]
Total nonaccrual loans		34
Covered Loans \| Commercial Loans \| Single-family Non-owner Occupied
Financing Receivable, Impaired [Line Items]
Total nonaccrual loans	77	77
Covered Loans \| Commercial Loans \| Non-farm, Non-residential
Financing Receivable, Impaired [Line Items]
Total nonaccrual loans	1,560	1,317
Covered Loans \| Consumer Real Estate \| Home Equity Lines
Financing Receivable, Impaired [Line Items]
Total nonaccrual loans	493	204
Covered Loans \| Consumer Real Estate \| Single Family Owner Occupied
Financing Receivable, Impaired [Line Items]
Total nonaccrual loans	508	682
Covered Loans \| Consumer Real Estate \| Owner Occupied Construction
Financing Receivable, Impaired [Line Items]
Total nonaccrual loans	$ 103	$ 106

Nonaccrual Loans by Loan Class (Detail) (USD $)
In Thousands, unless otherwise specified

Mar. 31, 2015

Dec. 31, 2014

Financing Receivable, Impaired [Line Items]

Total nonaccrual loans

$ 18,167

$ 12,994

Commercial Loans | Construction Development And Other Land

Financing Receivable, Impaired [Line Items]

Total nonaccrual loans