Non accrual Loans Presented by Loan Class (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Impaired [Line Items]
Total	$ 28,246
Acquired impaired loans	8
Total nonaccrual loans	28,254
Non Covered Loans
Financing Receivable, Impaired [Line Items]
Total	23,923	23,836
Acquired impaired loans	8	651
Total nonaccrual loans	23,931	24,487
Covered Loans
Financing Receivable, Impaired [Line Items]
Total	4,323
Total nonaccrual loans	4,323
Commercial Loans \| Construction Development And Other Land
Financing Receivable, Impaired [Line Items]
Total	2,395
Commercial Loans \| Commercial and Industrial
Financing Receivable, Impaired [Line Items]
Total	3,947
Commercial Loans \| Multi-family Residential
Financing Receivable, Impaired [Line Items]
Total	378
Commercial Loans \| Single-family Non-owner Occupied
Financing Receivable, Impaired [Line Items]
Total	7,092
Commercial Loans \| Non-farm, Non-residential
Financing Receivable, Impaired [Line Items]
Total	6,889
Commercial Loans \| Agricultural
Financing Receivable, Impaired [Line Items]
Total	2
Commercial Loans \| Non Covered Loans \| Construction Development And Other Land
Financing Receivable, Impaired [Line Items]
Total	405	793
Commercial Loans \| Non Covered Loans \| Commercial and Industrial
Financing Receivable, Impaired [Line Items]
Total	3,912	3,905
Commercial Loans \| Non Covered Loans \| Multi-family Residential
Financing Receivable, Impaired [Line Items]
Total	378	341
Commercial Loans \| Non Covered Loans \| Single-family Non-owner Occupied
Financing Receivable, Impaired [Line Items]
Total	7,071	1,639
Commercial Loans \| Non Covered Loans \| Non-farm, Non-residential
Financing Receivable, Impaired [Line Items]
Total	5,938	8,063
Commercial Loans \| Non Covered Loans \| Agricultural
Financing Receivable, Impaired [Line Items]
Total	2
Commercial Loans \| Non Covered Loans \| Farmland Loan
Financing Receivable, Impaired [Line Items]
Total		271
Commercial Loans \| Covered Loans \| Construction Development And Other Land
Financing Receivable, Impaired [Line Items]
Total	1,990
Commercial Loans \| Covered Loans \| Commercial and Industrial
Financing Receivable, Impaired [Line Items]
Total	35
Commercial Loans \| Covered Loans \| Single-family Non-owner Occupied
Financing Receivable, Impaired [Line Items]
Total	21
Commercial Loans \| Covered Loans \| Non-farm, Non-residential
Financing Receivable, Impaired [Line Items]
Total	951
Consumer Real Estate \| Home Equity Lines
Financing Receivable, Impaired [Line Items]
Total	1,308
Consumer Real Estate \| Single Family Owner Occupied
Financing Receivable, Impaired [Line Items]
Total	6,050
Consumer Real Estate \| Owner occupied construction
Financing Receivable, Impaired [Line Items]
Total	59
Consumer Real Estate \| Non Covered Loans \| Home Equity Lines
Financing Receivable, Impaired [Line Items]
Total	872	516
Consumer Real Estate \| Non Covered Loans \| Single Family Owner Occupied
Financing Receivable, Impaired [Line Items]
Total	5,219	8,255
Consumer Real Estate \| Non Covered Loans \| Owner occupied construction
Financing Receivable, Impaired [Line Items]
Total		1
Consumer Real Estate \| Covered Loans \| Home Equity Lines
Financing Receivable, Impaired [Line Items]
Total	436
Consumer Real Estate \| Covered Loans \| Single Family Owner Occupied
Financing Receivable, Impaired [Line Items]
Total	831
Consumer Real Estate \| Covered Loans \| Owner occupied construction
Financing Receivable, Impaired [Line Items]
Total	59
Consumer and Other \| Consumer Loan
Financing Receivable, Impaired [Line Items]
Total	126
Consumer and Other \| Non Covered Loans \| Consumer Loan
Financing Receivable, Impaired [Line Items]
Total	$ 126	$ 52