Loans - Summary of Risk Category of Loans by Class of Loans (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Risk Category Of Loans [Line Items]
Total Loans	$ 2,810,905	$ 2,667,943
Construction and Land Development [Member]
Risk Category Of Loans [Line Items]
Total Loans	581,340	584,440
Commercial and Industrial [Member]
Risk Category Of Loans [Line Items]
Total Loans	637,363	592,793
Consumer and Other [Member]
Risk Category Of Loans [Line Items]
Total Loans	4,448	5,568
Pass [Member]
Risk Category Of Loans [Line Items]
Total Loans	2,757,152	2,603,376
Pass [Member] | Construction and Land Development [Member]
Risk Category Of Loans [Line Items]
Total Loans	580,325	580,468
Pass [Member] | Commercial and Industrial [Member]
Risk Category Of Loans [Line Items]
Total Loans	596,529	553,589
Pass [Member] | Consumer and Other [Member]
Risk Category Of Loans [Line Items]
Total Loans	4,448	5,567
Special Mention [Member]
Risk Category Of Loans [Line Items]
Total Loans	16,005	25,856
Special Mention [Member] | Construction and Land Development [Member]
Risk Category Of Loans [Line Items]
Total Loans	432	1,416
Special Mention [Member] | Commercial and Industrial [Member]
Risk Category Of Loans [Line Items]
Total Loans	8,519	8,313
Special Mention [Member] | Consumer and Other [Member]
Risk Category Of Loans [Line Items]
Total Loans		1
Substandard [Member]
Risk Category Of Loans [Line Items]
Total Loans	37,748	38,711
Substandard [Member] | Construction and Land Development [Member]
Risk Category Of Loans [Line Items]
Total Loans	583	2,556
Substandard [Member] | Commercial and Industrial [Member]
Risk Category Of Loans [Line Items]
Total Loans	32,315	30,891
Commercial Real Estate Financing Receivable [Member]
Risk Category Of Loans [Line Items]
Total Loans	852,838	754,243
Commercial Real Estate Financing Receivable [Member] | Pass [Member]
Risk Category Of Loans [Line Items]
Total Loans	848,221	739,469
Commercial Real Estate Financing Receivable [Member] | Special Mention [Member]
Risk Category Of Loans [Line Items]
Total Loans	4,464	14,774
Commercial Real Estate Financing Receivable [Member] | Substandard [Member]
Risk Category Of Loans [Line Items]
Total Loans	153
Commercial Real Estate, Other [Member]
Risk Category Of Loans [Line Items]
Total Loans	40,652	48,017
Commercial Real Estate, Other [Member] | Pass [Member]
Risk Category Of Loans [Line Items]
Total Loans	40,033	48,017
Commercial Real Estate, Other [Member] | Special Mention [Member]
Risk Category Of Loans [Line Items]
Total Loans	619
Real Estate Residential Closed-end 1-4 Family [Member]
Risk Category Of Loans [Line Items]
Total Loans	497,234	493,065
Real Estate Residential Closed-end 1-4 Family [Member] | Pass [Member]
Risk Category Of Loans [Line Items]
Total Loans	492,921	489,781
Real Estate Residential Closed-end 1-4 Family [Member] | Special Mention [Member]
Risk Category Of Loans [Line Items]
Total Loans	1,567	948
Real Estate Residential Closed-end 1-4 Family [Member] | Substandard [Member]
Risk Category Of Loans [Line Items]
Total Loans	2,746	2,336
Residential Real Estate, Other [Member]
Risk Category Of Loans [Line Items]
Total Loans	197,030	189,817
Residential Real Estate, Other [Member] | Pass [Member]
Risk Category Of Loans [Line Items]
Total Loans	194,675	186,485
Residential Real Estate, Other [Member] | Special Mention [Member]
Risk Category Of Loans [Line Items]
Total Loans	404	404
Residential Real Estate, Other [Member] | Substandard [Member]
Risk Category Of Loans [Line Items]
Total Loans	$ 1,951	$ 2,928