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, 2023	Dec. 31, 2022
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment (net of unearned interest)	$ 7,472,622	$ 6,943,563
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)	960,868	908,494
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)	1,443,831	1,383,150
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)	575,652	475,236
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)	274,311	303,305
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)	1,216,508	1,117,899
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)	230,397	196,198
Real Estate [Member] | Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment (net of unearned interest)	425,930	408,037
Commercial Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment (net of unearned interest)	1,296,796	1,241,454
Consumer Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment (net of unearned interest)	475,721	446,756
Oil and Gas [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment (net of unearned interest)	$ 572,608	$ 463,034