Nonaccrual Loans by Loan Class (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Financing Receivable, Impaired [Line Items]
Total	$ 12,611	$ 22,506
Purchased impaired loans		8
Total nonaccrual loans	12,611	22,514
Commercial Loans \| Construction Development And Other Land
Financing Receivable, Impaired [Line Items]
Total	90	1,948
Commercial Loans \| Commercial and Industrial
Financing Receivable, Impaired [Line Items]
Total	2,378	5,433
Commercial Loans \| Multi-family Residential
Financing Receivable, Impaired [Line Items]
Total	80
Commercial Loans \| Single-family Non-owner Occupied
Financing Receivable, Impaired [Line Items]
Total	838	2,188
Commercial Loans \| Non-farm, Non-residential
Financing Receivable, Impaired [Line Items]
Total	2,490	2,685
Commercial Loans \| Farmland Loan
Financing Receivable, Impaired [Line Items]
Total		742
Consumer Real Estate \| Home Equity Lines
Financing Receivable, Impaired [Line Items]
Total	384	997
Consumer Real Estate \| Single Family Owner Occupied
Financing Receivable, Impaired [Line Items]
Total	5,968	8,122
Consumer Real Estate \| Owner occupied construction
Financing Receivable, Impaired [Line Items]
Total	341	190
Consumer and Other \| Consumer Loan
Financing Receivable, Impaired [Line Items]
Total	42	201
Non Covered Loans
Financing Receivable, Impaired [Line Items]
Total	11,480	19,153
Purchased impaired loans		8
Total nonaccrual loans	11,480	19,161
Non Covered Loans \| Commercial Loans \| Construction Development And Other Land
Financing Receivable, Impaired [Line Items]
Total		1,187
Non Covered Loans \| Commercial Loans \| Commercial and Industrial
Financing Receivable, Impaired [Line Items]
Total	2,356	5,341
Non Covered Loans \| Commercial Loans \| Multi-family Residential
Financing Receivable, Impaired [Line Items]
Total	80
Non Covered Loans \| Commercial Loans \| Single-family Non-owner Occupied
Financing Receivable, Impaired [Line Items]
Total	761	1,966
Non Covered Loans \| Commercial Loans \| Non-farm, Non-residential
Financing Receivable, Impaired [Line Items]
Total	2,338	2,685
Non Covered Loans \| Commercial Loans \| Farmland Loan
Financing Receivable, Impaired [Line Items]
Total		441
Non Covered Loans \| Consumer Real Estate \| Home Equity Lines
Financing Receivable, Impaired [Line Items]
Total	180	765
Non Covered Loans \| Consumer Real Estate \| Single Family Owner Occupied
Financing Receivable, Impaired [Line Items]
Total	5,497	6,567
Non Covered Loans \| Consumer Real Estate \| Owner occupied construction
Financing Receivable, Impaired [Line Items]
Total	226
Non Covered Loans \| Consumer and Other \| Consumer Loan
Financing Receivable, Impaired [Line Items]
Total	42	201
Covered Loans
Financing Receivable, Impaired [Line Items]
Total	1,131	3,353
Total nonaccrual loans	1,131	3,353
Covered Loans \| Commercial Loans \| Construction Development And Other Land
Financing Receivable, Impaired [Line Items]
Total	90	761
Covered Loans \| Commercial Loans \| Commercial and Industrial
Financing Receivable, Impaired [Line Items]
Total	22	92
Covered Loans \| Commercial Loans \| Single-family Non-owner Occupied
Financing Receivable, Impaired [Line Items]
Total	77	222
Covered Loans \| Commercial Loans \| Non-farm, Non-residential
Financing Receivable, Impaired [Line Items]
Total	152
Covered Loans \| Commercial Loans \| Farmland Loan
Financing Receivable, Impaired [Line Items]
Total		301
Covered Loans \| Consumer Real Estate \| Home Equity Lines
Financing Receivable, Impaired [Line Items]
Total	204	232
Covered Loans \| Consumer Real Estate \| Single Family Owner Occupied
Financing Receivable, Impaired [Line Items]
Total	471	1,555
Covered Loans \| Consumer Real Estate \| Owner occupied construction
Financing Receivable, Impaired [Line Items]
Total	$ 115	$ 190