Aging of Past Due Loans by Loan Class (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	$ 10,004	$ 10,400
60 - 89 Days Past Due	6,519	4,097
90+ Days Past Due	9,297	9,629
Total Past Due	25,820	24,126
Current Loans	1,645,214	1,665,290
Total loans	1,671,034	1,689,416
Non Covered Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	9,120	8,955
60 - 89 Days Past Due	6,049	3,576
90+ Days Past Due	7,309	7,677
Total Past Due	22,478	20,208
Current Loans	1,535,832	1,546,968
Total loans	1,558,310	1,567,176
Non Covered Loans \| Commercial Loans \| Construction Development And Other Land
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	21	39
60 - 89 Days Past Due		46
Total Past Due	21	85
Current Loans	39,607	41,186
Total loans	39,628	41,271
Non Covered Loans \| Commercial Loans \| Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	278	285
60 - 89 Days Past Due	192	6
90+ Days Past Due	105	103
Total Past Due	575	394
Current Loans	77,907	82,705
Total loans	78,482	83,099
Non Covered Loans \| Commercial Loans \| Multi-family Residential
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	283	81
60 - 89 Days Past Due		110
90+ Days Past Due	109
Total Past Due	392	191
Current Loans	96,903	97,289
Total loans	97,295	97,480
Non Covered Loans \| Commercial Loans \| Single-family Non-owner Occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	1,204	914
60 - 89 Days Past Due	302	513
90+ Days Past Due	368	425
Total Past Due	1,874	1,852
Current Loans	135,562	133,319
Total loans	137,436	135,171
Non Covered Loans \| Commercial Loans \| Non-farm, Non-residential
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	1,200	1,075
60 - 89 Days Past Due	3,830	783
90+ Days Past Due	2,289	1,984
Total Past Due	7,319	3,842
Current Loans	455,716	470,064
Total loans	463,035	473,906
Non Covered Loans \| Commercial Loans \| Agricultural
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	5
90+ Days Past Due		4
Total Past Due	5	4
Current Loans	1,666	1,595
Total loans	1,671	1,599
Non Covered Loans \| Commercial Loans \| Farmland Loan
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	6	89
90+ Days Past Due	57
Total Past Due	63	89
Current Loans	28,581	29,428
Total loans	28,644	29,517
Non Covered Loans \| Consumer Real Estate \| Home Equity Lines
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	784	492
60 - 89 Days Past Due	28	103
90+ Days Past Due	524	571
Total Past Due	1,336	1,166
Current Loans	107,822	109,791
Total loans	109,158	110,957
Non Covered Loans \| Consumer Real Estate \| Single Family Owner Occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	4,960	5,436
60 - 89 Days Past Due	1,259	1,931
90+ Days Past Due	3,818	4,564
Total Past Due	10,037	11,931
Current Loans	481,280	473,544
Total loans	491,317	485,475
Non Covered Loans \| Consumer Real Estate \| Owner Occupied Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
60 - 89 Days Past Due	353
Total Past Due	353
Current Loans	34,971	32,799
Total loans	35,324	32,799
Non Covered Loans \| Consumer and Other \| Consumer Loan
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	379	544
60 - 89 Days Past Due	85	84
90+ Days Past Due	39	26
Total Past Due	503	654
Current Loans	68,581	68,693
Total loans	69,084	69,347
Non Covered Loans \| Consumer and Other \| Other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current Loans	7,236	6,555
Total loans	7,236	6,555
Covered Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	884	1,445
60 - 89 Days Past Due	470	521
90+ Days Past Due	1,988	1,952
Total Past Due	3,342	3,918
Current Loans	109,382	118,322
Total loans	112,724	122,240
Covered Loans \| Commercial Loans \| Construction Development And Other Land
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	43	120
60 - 89 Days Past Due	18	17
90+ Days Past Due	5
Total Past Due	66	137
Current Loans	10,344	12,963
Total loans	10,410	13,100
Covered Loans \| Commercial Loans \| Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	179	84
60 - 89 Days Past Due	95	12
90+ Days Past Due		34
Total Past Due	274	130
Current Loans	2,097	2,532
Total loans	2,371	2,662
Covered Loans \| Commercial Loans \| Multi-family Residential
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current Loans	678	1,584
Total loans	678	1,584
Covered Loans \| Commercial Loans \| Single-family Non-owner Occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	10	122
90+ Days Past Due	77	77
Total Past Due	87	199
Current Loans	4,759	5,719
Total loans	4,846	5,918
Covered Loans \| Commercial Loans \| Non-farm, Non-residential
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	46	124
60 - 89 Days Past Due	45	140
90+ Days Past Due	1,488	1,258
Total Past Due	1,579	1,522
Current Loans	23,093	23,795
Total loans	24,672	25,317
Covered Loans \| Commercial Loans \| Agricultural
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current Loans	42	43
Total loans	42	43
Covered Loans \| Commercial Loans \| Farmland Loan
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	111	3
Total Past Due	111	3
Current Loans	586	713
Total loans	697	716
Covered Loans \| Consumer Real Estate \| Home Equity Lines
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	317	858
60 - 89 Days Past Due	279	318
90+ Days Past Due	177	168
Total Past Due	773	1,344
Current Loans	56,642	59,047
Total loans	57,415	60,391
Covered Loans \| Consumer Real Estate \| Single Family Owner Occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	178	134
60 - 89 Days Past Due	33	34
90+ Days Past Due	241	415
Total Past Due	452	583
Current Loans	10,542	11,385
Total loans	10,994	11,968
Covered Loans \| Consumer Real Estate \| Owner Occupied Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current Loans	512	453
Total loans	512	453
Covered Loans \| Consumer and Other \| Consumer Loan
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current Loans	87	88
Total loans	$ 87	$ 88

Aging of Past Due Loans by Loan Class (Detail) (USD $)
In Thousands, unless otherwise specified

Mar. 31, 2015

Dec. 31, 2014

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

30 - 59 Days Past Due

$ 10,004

$ 10,400

60 - 89 Days Past Due