Summary of Loans, Net of Unearned Income (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment, net of unearned income	$ 1,558,310	$ 1,567,176
Covered under loss share agreements	112,724	122,240
Total Loans held for investment, net of unearned income	1,671,034	1,689,416
Loans held for sale	1,174	1,792
Loans held for investment, net of unearned income, percentage	93.25%	92.76%
Covered loan percentage	6.75%	7.24%
Loans and leases receivable net reported amount covered and not covered percentage	100.00%	100.00%
Commercial Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment, net of unearned income	846,191	862,043
Loans held for investment, net of unearned income, percentage	50.63%	51.02%
Commercial Loans | Construction Development And Other Land
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment, net of unearned income	39,628	41,271
Covered under loss share agreements	10,410	13,100
Loans held for investment, net of unearned income, percentage	2.37%	2.44%
Commercial Loans | Commercial and Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment, net of unearned income	78,482	83,099
Covered under loss share agreements	2,371	2,662
Loans held for investment, net of unearned income, percentage	4.70%	4.92%
Commercial Loans | Multi-family Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment, net of unearned income	97,295	97,480
Covered under loss share agreements	678	1,584
Loans held for investment, net of unearned income, percentage	5.82%	5.77%
Commercial Loans | Single-family Non-owner Occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment, net of unearned income	137,436	135,171
Covered under loss share agreements	4,846	5,918
Loans held for investment, net of unearned income, percentage	8.22%	8.00%
Commercial Loans | Non-farm Non-residential Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment, net of unearned income	463,035	473,906
Covered under loss share agreements	24,672	25,317
Loans held for investment, net of unearned income, percentage	27.71%	28.05%
Commercial Loans | Agricultural
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment, net of unearned income	1,671	1,599
Covered under loss share agreements	42	43
Loans held for investment, net of unearned income, percentage	0.10%	0.09%
Commercial Loans | Farmland Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment, net of unearned income	28,644	29,517
Covered under loss share agreements	697	716
Loans held for investment, net of unearned income, percentage	1.71%	1.75%
Consumer Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment, net of unearned income	635,799	629,231
Loans held for investment, net of unearned income, percentage	38.05%	37.25%
Consumer Real Estate | Home Equity Lines
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment, net of unearned income	109,158	110,957
Covered under loss share agreements	57,415	60,391
Loans held for investment, net of unearned income, percentage	6.53%	6.57%
Consumer Real Estate | Single Family Owner Occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment, net of unearned income	491,317	485,475
Covered under loss share agreements	10,994	11,968
Loans held for investment, net of unearned income, percentage	29.40%	28.74%
Consumer Real Estate | Owner Occupied Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment, net of unearned income	35,324	32,799
Covered under loss share agreements	512	453
Loans held for investment, net of unearned income, percentage	2.12%	1.94%
Consumer and Other Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment, net of unearned income	76,320	75,902
Loans held for investment, net of unearned income, percentage	4.57%	4.49%
Consumer and Other Loans | Consumer Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment, net of unearned income	69,084	69,347
Covered under loss share agreements	87	88
Loans held for investment, net of unearned income, percentage	4.13%	4.10%
Consumer and Other Loans | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment, net of unearned income	$ 7,236	$ 6,555
Loans held for investment, net of unearned income, percentage	0.44%	0.39%