Non accrual Loans Presented by Loan Class (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Financing Receivable, Impaired [Line Items]
Total	$ 29,968	$ 28,246
Acquired impaired loans	8	8
Total nonaccrual loans	29,976	28,254
Commercial Loans \| Construction Development And Other Land
Financing Receivable, Impaired [Line Items]
Total	5,684	2,395
Commercial Loans \| Commercial and Industrial
Financing Receivable, Impaired [Line Items]
Total	5,161	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	2,335	7,092
Commercial Loans \| Non-farm, Non-residential
Financing Receivable, Impaired [Line Items]
Total	5,586	6,889
Commercial Loans \| Agricultural
Financing Receivable, Impaired [Line Items]
Total		2
Commercial Loans \| Farmland Loan
Financing Receivable, Impaired [Line Items]
Total	741
Consumer Real Estate \| Home Equity Lines
Financing Receivable, Impaired [Line Items]
Total	1,693	1,308
Consumer Real Estate \| Single Family Owner Occupied
Financing Receivable, Impaired [Line Items]
Total	8,305	6,050
Consumer Real Estate \| Owner occupied construction
Financing Receivable, Impaired [Line Items]
Total	241	59
Consumer and Other \| Consumer Loan
Financing Receivable, Impaired [Line Items]
Total	222	126
Non Covered Loans
Financing Receivable, Impaired [Line Items]
Total	26,389	23,923
Acquired impaired loans	8	8
Total nonaccrual loans	26,397	23,931
Non Covered Loans \| Commercial Loans \| Construction Development And Other Land
Financing Receivable, Impaired [Line Items]
Total	5,065	405
Non Covered Loans \| Commercial Loans \| Commercial and Industrial
Financing Receivable, Impaired [Line Items]
Total	5,058	3,912
Non Covered Loans \| Commercial Loans \| Multi-family Residential
Financing Receivable, Impaired [Line Items]
Total		378
Non Covered Loans \| Commercial Loans \| Single-family Non-owner Occupied
Financing Receivable, Impaired [Line Items]
Total	2,216	7,071
Non Covered Loans \| Commercial Loans \| Non-farm, Non-residential
Financing Receivable, Impaired [Line Items]
Total	5,268	5,938
Non Covered Loans \| Commercial Loans \| Agricultural
Financing Receivable, Impaired [Line Items]
Total		2
Non Covered Loans \| Commercial Loans \| Farmland Loan
Financing Receivable, Impaired [Line Items]
Total	437
Non Covered Loans \| Consumer Real Estate \| Home Equity Lines
Financing Receivable, Impaired [Line Items]
Total	1,417	872
Non Covered Loans \| Consumer Real Estate \| Single Family Owner Occupied
Financing Receivable, Impaired [Line Items]
Total	6,706	5,219
Non Covered Loans \| Consumer and Other \| Consumer Loan
Financing Receivable, Impaired [Line Items]
Total	222	126
Covered Loans
Financing Receivable, Impaired [Line Items]
Total	3,579	4,323
Total nonaccrual loans	3,579	4,323
Covered Loans \| Commercial Loans \| Construction Development And Other Land
Financing Receivable, Impaired [Line Items]
Total	619	1,990
Covered Loans \| Commercial Loans \| Commercial and Industrial
Financing Receivable, Impaired [Line Items]
Total	103	35
Covered Loans \| Commercial Loans \| Single-family Non-owner Occupied
Financing Receivable, Impaired [Line Items]
Total	119	21
Covered Loans \| Commercial Loans \| Non-farm, Non-residential
Financing Receivable, Impaired [Line Items]
Total	318	951
Covered Loans \| Commercial Loans \| Farmland Loan
Financing Receivable, Impaired [Line Items]
Total	304
Covered Loans \| Consumer Real Estate \| Home Equity Lines
Financing Receivable, Impaired [Line Items]
Total	276	436
Covered Loans \| Consumer Real Estate \| Single Family Owner Occupied
Financing Receivable, Impaired [Line Items]
Total	1,599	831
Covered Loans \| Consumer Real Estate \| Owner occupied construction
Financing Receivable, Impaired [Line Items]
Total	$ 241	$ 59