Non accrual Loans Presented by Loan Class (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Financing Receivable, Impaired [Line Items]
Total	$ 34,635	$ 28,246
Acquired impaired loans	8	8
Total nonaccrual loans	34,643	28,254
Non Covered Loans
Financing Receivable, Impaired [Line Items]
Total	30,068	23,923
Acquired impaired loans	8	8
Total nonaccrual loans	30,076	23,931
Covered Loans
Financing Receivable, Impaired [Line Items]
Total	4,567	4,323
Total nonaccrual loans	4,567	4,323
Commercial Loans \| Construction Development And Other Land
Financing Receivable, Impaired [Line Items]
Total	8,955	2,395
Commercial Loans \| Commercial and Industrial
Financing Receivable, Impaired [Line Items]
Total	5,423	3,947
Commercial Loans \| Multi-family Residential
Financing Receivable, Impaired [Line Items]
Total	445	378
Commercial Loans \| Single-family Non-owner Occupied
Financing Receivable, Impaired [Line Items]
Total	4,629	7,092
Commercial Loans \| Non-farm, Non-residential
Financing Receivable, Impaired [Line Items]
Total	6,206	6,889
Commercial Loans \| Agricultural
Financing Receivable, Impaired [Line Items]
Total	17	2
Commercial Loans \| Farmland Loan
Financing Receivable, Impaired [Line Items]
Total	177
Commercial Loans \| Non Covered Loans \| Construction Development And Other Land
Financing Receivable, Impaired [Line Items]
Total	6,842	405
Commercial Loans \| Non Covered Loans \| Commercial and Industrial
Financing Receivable, Impaired [Line Items]
Total	5,375	3,912
Commercial Loans \| Non Covered Loans \| Multi-family Residential
Financing Receivable, Impaired [Line Items]
Total	445	378
Commercial Loans \| Non Covered Loans \| Single-family Non-owner Occupied
Financing Receivable, Impaired [Line Items]
Total	4,600	7,071
Commercial Loans \| Non Covered Loans \| Non-farm, Non-residential
Financing Receivable, Impaired [Line Items]
Total	5,644	5,938
Commercial Loans \| Non Covered Loans \| Agricultural
Financing Receivable, Impaired [Line Items]
Total	17	2
Commercial Loans \| Non Covered Loans \| Farmland Loan
Financing Receivable, Impaired [Line Items]
Total	177
Commercial Loans \| Covered Loans \| Construction Development And Other Land
Financing Receivable, Impaired [Line Items]
Total	2,113	1,990
Commercial Loans \| Covered Loans \| Commercial and Industrial
Financing Receivable, Impaired [Line Items]
Total	48	35
Commercial Loans \| Covered Loans \| Single-family Non-owner Occupied
Financing Receivable, Impaired [Line Items]
Total	29	21
Commercial Loans \| Covered Loans \| Non-farm, Non-residential
Financing Receivable, Impaired [Line Items]
Total	562	951
Consumer Real Estate \| Home Equity Lines
Financing Receivable, Impaired [Line Items]
Total	1,463	1,308
Consumer Real Estate \| Single Family Owner Occupied
Financing Receivable, Impaired [Line Items]
Total	7,092	6,050
Consumer Real Estate \| Owner occupied construction
Financing Receivable, Impaired [Line Items]
Total	59	59
Consumer Real Estate \| Non Covered Loans \| Home Equity Lines
Financing Receivable, Impaired [Line Items]
Total	925	872
Consumer Real Estate \| Non Covered Loans \| Single Family Owner Occupied
Financing Receivable, Impaired [Line Items]
Total	5,874	5,219
Consumer Real Estate \| Covered Loans \| Home Equity Lines
Financing Receivable, Impaired [Line Items]
Total	538	436
Consumer Real Estate \| Covered Loans \| Single Family Owner Occupied
Financing Receivable, Impaired [Line Items]
Total	1,218	831
Consumer Real Estate \| Covered Loans \| Owner occupied construction
Financing Receivable, Impaired [Line Items]
Total	59	59
Consumer and Other \| Consumer Loan
Financing Receivable, Impaired [Line Items]
Total	169	126
Consumer and Other \| Non Covered Loans \| Consumer Loan
Financing Receivable, Impaired [Line Items]
Total	$ 169	$ 126