Loans Held for Investment and Allowance for Credit Losses on Loans - Summary of Loans Held for Investment by Portfolio Segment (Detail) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment (net of unearned interest)	$ 6,827,772	$ 6,169,442
Real Estate [Member] | Commercial Real Estate Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment (net of unearned interest)	896,202	775,554
Real Estate [Member] | Commercial Real Estate Non-Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment (net of unearned interest)	1,230,074	1,095,324
Real Estate [Member] | Construction and Development Less than 60 Months [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment (net of unearned interest)	473,631	415,466
Real Estate [Member] | Construction Residential Real Estate Less than 60 Months [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment (net of unearned interest)	311,168	254,524
Real Estate [Member] | Residential Real Estate First Lien [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment (net of unearned interest)	1,097,710	937,006
Real Estate [Member] | Residential Real Estate All Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment (net of unearned interest)	188,508	161,018
Real Estate [Member] | Farmland [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment (net of unearned interest)	256,821	272,179
Commercial and Agricultural Non-Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment (net of unearned interest)	1,429,401	1,416,093
Consumer Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment (net of unearned interest)	431,913	413,370
Oil and Gas [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment (net of unearned interest)	$ 512,344	$ 428,908