Loans - Summary of Risk Category of Loans by Class of Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Risk Category Of Loans [Line Items]
Total	$ 2,816,464	$ 2,674,943
Construction and Land Development
Risk Category Of Loans [Line Items]
Total	591,541	584,440
Commercial Real Estate
Risk Category Of Loans [Line Items]
Total Loans	0
Total	993,912	805,260
Residential Real Estate
Risk Category Of Loans [Line Items]
Total	643,601	682,882
Commercial and Industrial
Risk Category Of Loans [Line Items]
Total	582,641	596,793
Consumer and Other
Risk Category Of Loans [Line Items]
Total	4,769	5,568
Pass
Risk Category Of Loans [Line Items]
Total Loans	2,764,188	2,610,376
Pass | Construction and Land Development
Risk Category Of Loans [Line Items]
Total Loans	591,293	580,468
Pass | Commercial and Industrial
Risk Category Of Loans [Line Items]
Total Loans	539,442	557,589
Pass | Consumer and Other
Risk Category Of Loans [Line Items]
Total Loans	4,769	5,567
Special Mention
Risk Category Of Loans [Line Items]
Total Loans	3,013	25,856
Special Mention | Construction and Land Development
Risk Category Of Loans [Line Items]
Total Loans	248	1,416
Special Mention | Commercial and Industrial
Risk Category Of Loans [Line Items]
Total Loans	943	8,313
Special Mention | Consumer and Other
Risk Category Of Loans [Line Items]
Total Loans	0	1
Substandard
Risk Category Of Loans [Line Items]
Total Loans	49,263	38,711
Substandard | Construction and Land Development
Risk Category Of Loans [Line Items]
Total Loans	0	2,556
Substandard | Commercial and Industrial
Risk Category Of Loans [Line Items]
Total Loans	42,256	30,891
Substandard | Consumer and Other
Risk Category Of Loans [Line Items]
Total Loans	0	0
Nonfarm, nonresidential | Commercial Real Estate
Risk Category Of Loans [Line Items]
Total	944,021	754,243
Nonfarm, nonresidential | Pass | Commercial Real Estate
Risk Category Of Loans [Line Items]
Total Loans	941,260	739,469
Nonfarm, nonresidential | Special Mention | Commercial Real Estate
Risk Category Of Loans [Line Items]
Total Loans	997	14,774
Nonfarm, nonresidential | Substandard | Commercial Real Estate
Risk Category Of Loans [Line Items]
Total Loans	1,764	0
Commercial real estate, other | Commercial Real Estate
Risk Category Of Loans [Line Items]
Total	49,891	51,017
Commercial real estate, other | Pass | Commercial Real Estate
Risk Category Of Loans [Line Items]
Total Loans	49,891	51,017
Commercial real estate, other | Special Mention | Commercial Real Estate
Risk Category Of Loans [Line Items]
Total Loans		0
Commercial real estate, other | Substandard | Commercial Real Estate
Risk Category Of Loans [Line Items]
Total Loans		0
Closed-end 1-4 family | Residential Real Estate
Risk Category Of Loans [Line Items]
Total	455,920	493,065
Closed-end 1-4 family | Pass | Residential Real Estate
Risk Category Of Loans [Line Items]
Total Loans	452,363	489,781
Closed-end 1-4 family | Special Mention | Residential Real Estate
Risk Category Of Loans [Line Items]
Total Loans	825	948
Closed-end 1-4 family | Substandard | Residential Real Estate
Risk Category Of Loans [Line Items]
Total Loans	2,732	2,336
Other | Residential Real Estate
Risk Category Of Loans [Line Items]
Total	187,681	189,817
Other | Pass | Residential Real Estate
Risk Category Of Loans [Line Items]
Total Loans	185,170	186,485
Other | Special Mention | Residential Real Estate
Risk Category Of Loans [Line Items]
Total Loans	0	404
Other | Substandard | Residential Real Estate
Risk Category Of Loans [Line Items]
Total Loans	$ 2,511	$ 2,928