Aging of Past Due Loans by Loan Class (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	$ 19,099	$ 24,126
Current Loans	1,671,375	1,665,290
Total loans	1,690,474	1,689,416
Not covered under loss share agreements	1,600,271	1,567,176
Covered under loss share agreements	90,203	122,240
Commercial Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Not covered under loss share agreements	878,176	862,043
Covered under loss share agreements	28,900	49,340
Commercial Loans \| Construction Development And Other Land
Financing Receivable, Recorded Investment, Past Due [Line Items]
Not covered under loss share agreements	45,930	41,271
Covered under loss share agreements	7,573	13,100
Commercial Loans \| Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Not covered under loss share agreements	85,319	83,099
Covered under loss share agreements	1,326	2,662
Commercial Loans \| Multi-family Residential
Financing Receivable, Recorded Investment, Past Due [Line Items]
Not covered under loss share agreements	93,356	97,480
Covered under loss share agreements	699	1,584
Commercial Loans \| Single-family Non-owner Occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Not covered under loss share agreements	144,725	135,171
Covered under loss share agreements	2,899	5,918
Commercial Loans \| Non-farm, Non-residential
Financing Receivable, Recorded Investment, Past Due [Line Items]
Not covered under loss share agreements	479,297	473,906
Covered under loss share agreements	15,712	25,317
Commercial Loans \| Agricultural
Financing Receivable, Recorded Investment, Past Due [Line Items]
Not covered under loss share agreements	2,414	1,599
Covered under loss share agreements	35	43
Commercial Loans \| Farmland Loan
Financing Receivable, Recorded Investment, Past Due [Line Items]
Not covered under loss share agreements	27,135	29,517
Covered under loss share agreements	656	716
Consumer Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Not covered under loss share agreements	639,953	629,231
Covered under loss share agreements	61,219	72,812
Consumer Real Estate \| Home Equity Lines
Financing Receivable, Recorded Investment, Past Due [Line Items]
Not covered under loss share agreements	107,655	110,957
Covered under loss share agreements	51,205	60,391
Consumer Real Estate \| Single Family Owner Occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Not covered under loss share agreements	492,157	485,475
Covered under loss share agreements	9,736	11,968
Consumer Real Estate \| Owner Occupied Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Not covered under loss share agreements	40,141	32,799
Covered under loss share agreements	278	453
Consumer and Other \| Consumer Loan
Financing Receivable, Recorded Investment, Past Due [Line Items]
Not covered under loss share agreements	75,084	69,347
Covered under loss share agreements	84	88
Consumer and Other \| Other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Not covered under loss share agreements	7,058	6,555
Non Covered Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	17,891	20,208
Current Loans	1,582,380	1,546,968
Non Covered Loans \| Commercial Loans \| Construction Development And Other Land
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	152	85
Current Loans	45,778	41,186
Non Covered Loans \| Commercial Loans \| Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	110	394
Current Loans	85,209	82,705
Non Covered Loans \| Commercial Loans \| Multi-family Residential
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	149	191
Current Loans	93,207	97,289
Non Covered Loans \| Commercial Loans \| Single-family Non-owner Occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	1,816	1,852
Current Loans	142,909	133,319
Non Covered Loans \| Commercial Loans \| Non-farm, Non-residential
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	6,315	3,842
Current Loans	472,982	470,064
Non Covered Loans \| Commercial Loans \| Agricultural
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		4
Current Loans	2,414	1,595
Non Covered Loans \| Commercial Loans \| Farmland Loan
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	291	89
Current Loans	26,844	29,428
Non Covered Loans \| Consumer Real Estate \| Home Equity Lines
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	802	1,166
Current Loans	106,853	109,791
Non Covered Loans \| Consumer Real Estate \| Single Family Owner Occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	7,754	11,931
Current Loans	484,403	473,544
Non Covered Loans \| Consumer Real Estate \| Owner Occupied Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current Loans	40,141	32,799
Non Covered Loans \| Consumer and Other \| Consumer Loan
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	502	654
Current Loans	74,582	68,693
Non Covered Loans \| Consumer and Other \| Other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current Loans	7,058	6,555
Covered Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	1,208	3,918
Current Loans	88,995	118,322
Covered Loans \| Commercial Loans \| Construction Development And Other Land
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	137	137
Current Loans	7,436	12,963
Covered Loans \| Commercial Loans \| Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	25	130
Current Loans	1,301	2,532
Covered Loans \| Commercial Loans \| Multi-family Residential
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current Loans	699	1,584
Covered Loans \| Commercial Loans \| Single-family Non-owner Occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	3	199
Current Loans	2,896	5,719
Covered Loans \| Commercial Loans \| Non-farm, Non-residential
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	162	1,522
Current Loans	15,550	23,795
Covered Loans \| Commercial Loans \| Agricultural
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current Loans	35	43
Covered Loans \| Commercial Loans \| Farmland Loan
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		3
Current Loans	656	713
Covered Loans \| Consumer Real Estate \| Home Equity Lines
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	568	1,344
Current Loans	50,637	59,047
Covered Loans \| Consumer Real Estate \| Single Family Owner Occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	107	583
Current Loans	9,629	11,385
Covered Loans \| Consumer Real Estate \| Owner Occupied Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	206
Current Loans	72	453
Covered Loans \| Consumer and Other \| Consumer Loan
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current Loans	84	88
Financing Receivables, 30 to 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	5,586	10,400
Financing Receivables, 30 to 59 Days Past Due \| Non Covered Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	4,838	8,955
Financing Receivables, 30 to 59 Days Past Due \| Non Covered Loans \| Commercial Loans \| Construction Development And Other Land
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	42	39
Financing Receivables, 30 to 59 Days Past Due \| Non Covered Loans \| Commercial Loans \| Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	55	285
Financing Receivables, 30 to 59 Days Past Due \| Non Covered Loans \| Commercial Loans \| Multi-family Residential
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	72	81
Financing Receivables, 30 to 59 Days Past Due \| Non Covered Loans \| Commercial Loans \| Single-family Non-owner Occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	241	914
Financing Receivables, 30 to 59 Days Past Due \| Non Covered Loans \| Commercial Loans \| Non-farm, Non-residential
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	800	1,075
Financing Receivables, 30 to 59 Days Past Due \| Non Covered Loans \| Commercial Loans \| Farmland Loan
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	71	89
Financing Receivables, 30 to 59 Days Past Due \| Non Covered Loans \| Consumer Real Estate \| Home Equity Lines
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	320	492
Financing Receivables, 30 to 59 Days Past Due \| Non Covered Loans \| Consumer Real Estate \| Single Family Owner Occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	2,802	5,436
Financing Receivables, 30 to 59 Days Past Due \| Non Covered Loans \| Consumer and Other \| Consumer Loan
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	435	544
Financing Receivables, 30 to 59 Days Past Due \| Covered Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	748	1,445
Financing Receivables, 30 to 59 Days Past Due \| Covered Loans \| Commercial Loans \| Construction Development And Other Land
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	93	120
Financing Receivables, 30 to 59 Days Past Due \| Covered Loans \| Commercial Loans \| Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		84
Financing Receivables, 30 to 59 Days Past Due \| Covered Loans \| Commercial Loans \| Single-family Non-owner Occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		122
Financing Receivables, 30 to 59 Days Past Due \| Covered Loans \| Commercial Loans \| Non-farm, Non-residential
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	15	124
Financing Receivables, 30 to 59 Days Past Due \| Covered Loans \| Commercial Loans \| Farmland Loan
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		3
Financing Receivables, 30 to 59 Days Past Due \| Covered Loans \| Consumer Real Estate \| Home Equity Lines
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	454	858
Financing Receivables, 30 to 59 Days Past Due \| Covered Loans \| Consumer Real Estate \| Single Family Owner Occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		134
Financing Receivables, 30 to 59 Days Past Due \| Covered Loans \| Consumer Real Estate \| Owner Occupied Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	186
Financing Receivables, 60 to 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	2,790	4,097
Financing Receivables, 60 to 89 Days Past Due \| Non Covered Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	2,449	3,576
Financing Receivables, 60 to 89 Days Past Due \| Non Covered Loans \| Commercial Loans \| Construction Development And Other Land
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	11	46
Financing Receivables, 60 to 89 Days Past Due \| Non Covered Loans \| Commercial Loans \| Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		6
Financing Receivables, 60 to 89 Days Past Due \| Non Covered Loans \| Commercial Loans \| Multi-family Residential
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	77	110
Financing Receivables, 60 to 89 Days Past Due \| Non Covered Loans \| Commercial Loans \| Single-family Non-owner Occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	441	513
Financing Receivables, 60 to 89 Days Past Due \| Non Covered Loans \| Commercial Loans \| Non-farm, Non-residential
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	42	783
Financing Receivables, 60 to 89 Days Past Due \| Non Covered Loans \| Commercial Loans \| Farmland Loan
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	69
Financing Receivables, 60 to 89 Days Past Due \| Non Covered Loans \| Consumer Real Estate \| Home Equity Lines
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	24	103
Financing Receivables, 60 to 89 Days Past Due \| Non Covered Loans \| Consumer Real Estate \| Single Family Owner Occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	1,743	1,931
Financing Receivables, 60 to 89 Days Past Due \| Non Covered Loans \| Consumer and Other \| Consumer Loan
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	42	84
Financing Receivables, 60 to 89 Days Past Due \| Covered Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	341	521
Financing Receivables, 60 to 89 Days Past Due \| Covered Loans \| Commercial Loans \| Construction Development And Other Land
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	2	17
Financing Receivables, 60 to 89 Days Past Due \| Covered Loans \| Commercial Loans \| Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	9	12
Financing Receivables, 60 to 89 Days Past Due \| Covered Loans \| Commercial Loans \| Single-family Non-owner Occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	3
Financing Receivables, 60 to 89 Days Past Due \| Covered Loans \| Commercial Loans \| Non-farm, Non-residential
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	108	140
Financing Receivables, 60 to 89 Days Past Due \| Covered Loans \| Consumer Real Estate \| Home Equity Lines
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	106	318
Financing Receivables, 60 to 89 Days Past Due \| Covered Loans \| Consumer Real Estate \| Single Family Owner Occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	93	34
Financing Receivables, 60 to 89 Days Past Due \| Covered Loans \| Consumer Real Estate \| Owner Occupied Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	20
Financing Receivables, Equal to Greater than 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	10,723	9,629
Financing Receivables, Equal to Greater than 90 Days Past Due \| Non Covered Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	10,604	7,677
Financing Receivables, Equal to Greater than 90 Days Past Due \| Non Covered Loans \| Commercial Loans \| Construction Development And Other Land
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	99
Financing Receivables, Equal to Greater than 90 Days Past Due \| Non Covered Loans \| Commercial Loans \| Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	55	103
Financing Receivables, Equal to Greater than 90 Days Past Due \| Non Covered Loans \| Commercial Loans \| Single-family Non-owner Occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	1,134	425
Financing Receivables, Equal to Greater than 90 Days Past Due \| Non Covered Loans \| Commercial Loans \| Non-farm, Non-residential
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	5,473	1,984
Financing Receivables, Equal to Greater than 90 Days Past Due \| Non Covered Loans \| Commercial Loans \| Agricultural
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		4
Financing Receivables, Equal to Greater than 90 Days Past Due \| Non Covered Loans \| Commercial Loans \| Farmland Loan
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	151
Financing Receivables, Equal to Greater than 90 Days Past Due \| Non Covered Loans \| Consumer Real Estate \| Home Equity Lines
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	458	571
Financing Receivables, Equal to Greater than 90 Days Past Due \| Non Covered Loans \| Consumer Real Estate \| Single Family Owner Occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	3,209	4,564
Financing Receivables, Equal to Greater than 90 Days Past Due \| Non Covered Loans \| Consumer and Other \| Consumer Loan
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	25	26
Financing Receivables, Equal to Greater than 90 Days Past Due \| Covered Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	119	1,952
Financing Receivables, Equal to Greater than 90 Days Past Due \| Covered Loans \| Commercial Loans \| Construction Development And Other Land
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	42
Financing Receivables, Equal to Greater than 90 Days Past Due \| Covered Loans \| Commercial Loans \| Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	16	34
Financing Receivables, Equal to Greater than 90 Days Past Due \| Covered Loans \| Commercial Loans \| Single-family Non-owner Occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		77
Financing Receivables, Equal to Greater than 90 Days Past Due \| Covered Loans \| Commercial Loans \| Non-farm, Non-residential
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	39	1,258
Financing Receivables, Equal to Greater than 90 Days Past Due \| Covered Loans \| Consumer Real Estate \| Home Equity Lines
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	8	168
Financing Receivables, Equal to Greater than 90 Days Past Due \| Covered Loans \| Consumer Real Estate \| Single Family Owner Occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	$ 14	$ 415

Aging of Past Due Loans by Loan Class (Detail) - USD ($)
$ in Thousands

Sep. 30, 2015

Dec. 31, 2014

Financing Receivable, Recorded Investment, Past Due [Line Items]

Past Due

$ 19,099

$ 24,126

Current Loans

1,671,375

1,665,290

Total loans

1,690,474