Aging of Past Due Loans by Loan Class (Detail) - USD ($)
$ in Thousands
Sep. 30, 2016
Dec. 31, 2015
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due $ 22,779 $ 25,079
Current Loans 1,813,605 1,681,462
Total loans 1,836,384 1,706,541
Not covered under loss share agreements 1,774,547 1,623,506
Covered under loss share agreements 61,837 83,035
Commercial Loans    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Not covered under loss share agreements 1,045,427 898,087
Covered under loss share agreements 15,761 25,529
Commercial Loans | Construction Development And Other Land    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Not covered under loss share agreements 49,799 48,896
Covered under loss share agreements 4,699 6,303
Commercial Loans | Commercial and Industrial Loans    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Not covered under loss share agreements 90,362 88,903
Covered under loss share agreements 941 1,170
Commercial Loans | Multi-family Residential    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Not covered under loss share agreements 127,468 95,026
Covered under loss share agreements 43 640
Commercial Loans | Single-family Non-owner Occupied    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Not covered under loss share agreements 144,023 149,351
Covered under loss share agreements 1,328 2,674
Commercial Loans | Non-farm, Non-residential    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Not covered under loss share agreements 596,015 485,460
Covered under loss share agreements 8,312 14,065
Commercial Loans | Agricultural    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Not covered under loss share agreements 5,786 2,911
Covered under loss share agreements 26 34
Commercial Loans | Farmland Loan    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Not covered under loss share agreements 31,974 27,540
Covered under loss share agreements 412 643
Consumer Real Estate    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Not covered under loss share agreements 649,728 646,081
Covered under loss share agreements 45,996 57,422
Consumer Real Estate | Home Equity Lines    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Not covered under loss share agreements 108,108 107,367
Covered under loss share agreements 38,737 48,565
Consumer Real Estate | Single Family Owner Occupied    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Not covered under loss share agreements 497,695 495,209
Covered under loss share agreements 7,058 8,595
Consumer Real Estate | Owner Occupied Construction    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Not covered under loss share agreements 43,925 43,505
Covered under loss share agreements 201 262
Consumer and Other | Consumer Loan    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Not covered under loss share agreements 76,363 72,000
Covered under loss share agreements 80 84
Consumer and Other | Other Loans    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Not covered under loss share agreements 3,029 7,338
Covered Loans    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due 919 2,682
Current Loans 60,918 80,353
Covered Loans | Commercial Loans | Construction Development And Other Land    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due 144 138
Current Loans 4,555 6,165
Covered Loans | Commercial Loans | Commercial and Industrial Loans    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due   16
Current Loans 941 1,154
Covered Loans | Commercial Loans | Multi-family Residential    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Current Loans 43 640
Covered Loans | Commercial Loans | Single-family Non-owner Occupied    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due 25 1,422
Current Loans 1,303 1,252
Covered Loans | Commercial Loans | Non-farm, Non-residential    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due   39
Current Loans 8,312 14,026
Covered Loans | Commercial Loans | Agricultural    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Current Loans 26 34
Covered Loans | Commercial Loans | Farmland Loan    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Current Loans 412 643
Covered Loans | Consumer Real Estate | Home Equity Lines    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due 400 751
Current Loans 38,337 47,814
Covered Loans | Consumer Real Estate | Single Family Owner Occupied    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due 350 316
Current Loans 6,708 8,279
Covered Loans | Consumer Real Estate | Owner Occupied Construction    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Current Loans 201 262
Covered Loans | Consumer and Other | Consumer Loan    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Current Loans 80 84
Non Covered Loans    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due 21,860 22,397
Current Loans 1,752,687 1,601,109
Non Covered Loans | Commercial Loans | Construction Development And Other Land    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due 122 39
Current Loans 49,677 48,857
Non Covered Loans | Commercial Loans | Commercial and Industrial Loans    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due 323 347
Current Loans 90,039 88,556
Non Covered Loans | Commercial Loans | Multi-family Residential    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due 660 462
Current Loans 126,808 94,564
Non Covered Loans | Commercial Loans | Single-family Non-owner Occupied    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due 1,195 1,797
Current Loans 142,828 147,554
Non Covered Loans | Commercial Loans | Non-farm, Non-residential    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due 7,454 5,963
Current Loans 588,561 479,497
Non Covered Loans | Commercial Loans | Agricultural    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due 255  
Current Loans 5,531 2,911
Non Covered Loans | Commercial Loans | Farmland Loan    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due 648 830
Current Loans 31,326 26,710
Non Covered Loans | Consumer Real Estate | Home Equity Lines    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due 940 1,331
Current Loans 107,168 106,036
Non Covered Loans | Consumer Real Estate | Single Family Owner Occupied    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due 8,948 11,256
Current Loans 488,747 483,953
Non Covered Loans | Consumer Real Estate | Owner Occupied Construction    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due 593  
Current Loans 43,332 43,505
Non Covered Loans | Consumer and Other | Consumer Loan    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due 722 372
Current Loans 75,641 71,628
Non Covered Loans | Consumer and Other | Other Loans    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Current Loans 3,029 7,338
Financing Receivables, 30 to 59 Days Past Due    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due 11,594 11,612
Financing Receivables, 30 to 59 Days Past Due | Covered Loans    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due 695 2,281
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 105 96
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 25 1,422
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 333 489
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 232 274
Financing Receivables, 30 to 59 Days Past Due | Non Covered Loans    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due 10,899 9,331
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 5  
Financing Receivables, 30 to 59 Days Past Due | Non Covered Loans | Commercial Loans | Commercial and Industrial Loans    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due 121 281
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 283 302
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 110 748
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 4,726 347
Financing Receivables, 30 to 59 Days Past Due | Non Covered Loans | Commercial Loans | Agricultural    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due 255  
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 72 585
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 377 668
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 4,123 6,122
Financing Receivables, 30 to 59 Days Past Due | Non Covered Loans | Consumer Real Estate | Owner Occupied Construction    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due 251  
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 576 278
Financing Receivables, 60 to 89 Days Past Due    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due 3,551 3,195
Financing Receivables, 60 to 89 Days Past Due | Covered Loans    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due 69 37
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 43 37
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 26  
Financing Receivables, 60 to 89 Days Past Due | Non Covered Loans    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due 3,482 3,158
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 64  
Financing Receivables, 60 to 89 Days Past Due | Non Covered Loans | Commercial Loans | Commercial and Industrial Loans    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due 31 66
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 71 76
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 305 120
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 277 676
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 576 11
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 169 195
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 1,875 1,943
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 114 71
Financing Receivables, Equal to Greater than 90 Days Past Due    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due 7,634 10,272
Financing Receivables, Equal to Greater than 90 Days Past Due | Covered Loans    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due 155 364
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 39 42
Financing Receivables, Equal to Greater than 90 Days Past Due | Covered Loans | Commercial Loans | Commercial and Industrial Loans    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due   16
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
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 24 225
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 92 42
Financing Receivables, Equal to Greater than 90 Days Past Due | Non Covered Loans    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due 7,479 9,908
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 53 39
Financing Receivables, Equal to Greater than 90 Days Past Due | Non Covered Loans | Commercial Loans | Commercial and Industrial Loans    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due 171  
Financing Receivables, Equal to Greater than 90 Days Past Due | Non Covered Loans | Commercial Loans | Multi-family Residential    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due 306 84
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 780 929
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 2,451 4,940
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   234
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 394 468
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 2,950 3,191
Financing Receivables, Equal to Greater than 90 Days Past Due | Non Covered Loans | Consumer Real Estate | Owner Occupied Construction    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Past Due 342  
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 $ 32 $ 23