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, 2024	Dec. 31, 2023
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment (net of unearned interest)	$ 7,781,860	$ 7,656,645
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)	962,203	960,944
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)	1,531,185	1,486,420
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)	669,726	642,643
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)	280,686	283,486
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)	1,283,879	1,258,744
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)	252,635	244,696
Real Estate [Member] | Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment (net of unearned interest)	449,812	427,139
Commercial Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment (net of unearned interest)	1,320,840	1,289,452
Consumer Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment (net of unearned interest)	465,166	476,467
Oil and Gas [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment (net of unearned interest)	$ 565,728	$ 586,654