Loans Held for Investment and Allowance for Credit Losses on Loans - Summary of Loans Held for Investment by Portfolio Segment (Detail) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment (net of unearned interest)	$ 7,118,608	$ 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)	920,104	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)	1,396,400	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)	534,847	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)	304,766	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)	1,147,800	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)	206,402	196,198
Real Estate [Member] | Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment (net of unearned interest)	422,488	408,037
Commercial Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment (net of unearned interest)	1,262,737	1,241,454
Consumer Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment (net of unearned interest)	441,497	446,756
Oil and Gas [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment (net of unearned interest)	$ 481,567	$ 463,034