Non accrual Loans Presented by Loan Class (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Financing Receivable, Impaired [Line Items]
Total	$ 33,014	$ 28,246
Acquired impaired loans		8
Total nonaccrual loans	33,014	28,254
Commercial Loans \| Construction Development And Other Land
Financing Receivable, Impaired [Line Items]
Total	6,642	2,395
Commercial Loans \| Commercial and Industrial
Financing Receivable, Impaired [Line Items]
Total	5,525	3,947
Commercial Loans \| Multi-family Residential
Financing Receivable, Impaired [Line Items]
Total	20	378
Commercial Loans \| Single-family Non-owner Occupied
Financing Receivable, Impaired [Line Items]
Total	3,404	7,092
Commercial Loans \| Non-farm, Non-residential
Financing Receivable, Impaired [Line Items]
Total	7,704	6,889
Commercial Loans \| Agricultural
Financing Receivable, Impaired [Line Items]
Total		2
Commercial Loans \| Farmland Loan
Financing Receivable, Impaired [Line Items]
Total	444
Consumer Real Estate \| Home Equity Lines
Financing Receivable, Impaired [Line Items]
Total	1,848	1,308
Consumer Real Estate \| Single Family Owner Occupied
Financing Receivable, Impaired [Line Items]
Total	7,171	6,050
Consumer Real Estate \| Owner occupied construction
Financing Receivable, Impaired [Line Items]
Total	170	59
Consumer and Other \| Consumer Loan
Financing Receivable, Impaired [Line Items]
Total	86	126
Non Covered Loans
Financing Receivable, Impaired [Line Items]
Total	29,125	23,923
Acquired impaired loans		8
Total nonaccrual loans	29,125	23,931
Non Covered Loans \| Commercial Loans \| Construction Development And Other Land
Financing Receivable, Impaired [Line Items]
Total	5,240	405
Non Covered Loans \| Commercial Loans \| Commercial and Industrial
Financing Receivable, Impaired [Line Items]
Total	5,453	3,912
Non Covered Loans \| Commercial Loans \| Multi-family Residential
Financing Receivable, Impaired [Line Items]
Total	20	378
Non Covered Loans \| Commercial Loans \| Single-family Non-owner Occupied
Financing Receivable, Impaired [Line Items]
Total	3,378	7,071
Non Covered Loans \| Commercial Loans \| Non-farm, Non-residential
Financing Receivable, Impaired [Line Items]
Total	7,039	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	444
Non Covered Loans \| Consumer Real Estate \| Home Equity Lines
Financing Receivable, Impaired [Line Items]
Total	1,305	872
Non Covered Loans \| Consumer Real Estate \| Single Family Owner Occupied
Financing Receivable, Impaired [Line Items]
Total	6,160	5,219
Non Covered Loans \| Consumer and Other \| Consumer Loan
Financing Receivable, Impaired [Line Items]
Total	86	126
Covered Loans
Financing Receivable, Impaired [Line Items]
Total	3,889	4,323
Total nonaccrual loans	3,889	4,323
Covered Loans \| Commercial Loans \| Construction Development And Other Land
Financing Receivable, Impaired [Line Items]
Total	1,402	1,990
Covered Loans \| Commercial Loans \| Commercial and Industrial
Financing Receivable, Impaired [Line Items]
Total	72	35
Covered Loans \| Commercial Loans \| Single-family Non-owner Occupied
Financing Receivable, Impaired [Line Items]
Total	26	21
Covered Loans \| Commercial Loans \| Non-farm, Non-residential
Financing Receivable, Impaired [Line Items]
Total	665	951
Covered Loans \| Consumer Real Estate \| Home Equity Lines
Financing Receivable, Impaired [Line Items]
Total	543	436
Covered Loans \| Consumer Real Estate \| Single Family Owner Occupied
Financing Receivable, Impaired [Line Items]
Total	1,011	831
Covered Loans \| Consumer Real Estate \| Owner occupied construction
Financing Receivable, Impaired [Line Items]
Total	$ 170	$ 59