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Loans and Allowance for Credit Losses - Additional Information (Details)	12 Months Ended
	Dec. 31, 2024 USD ($) Asset	Dec. 31, 2023 USD ($) Asset	Dec. 31, 2022 USD ($) Asset	Mar. 31, 2023 USD ($)
Accounts Notes And Loans Receivable [Line Items]
Loan purchase discounts	$ 35,200,000
Loans held for sale	10,700,000
Loans	$ 21,797,404,000	$ 20,848,176,000
Percentage of Loans Related to Single Industry on Loans	10.00%	10.00%
Percentage of real estate loans aggregating to company loan portfolio, excluding Warehouse Purchase Program loans	81.30%	83.00%
Loans and Leases Receivable, Related Parties	$ 266,000	$ 292,000	$ 547,000
Loans held for investment	$ 21,057,616,000	$ 20,352,559,000
Financing Receivable Ratio of Nonperforming Loans to All Loans and Other Real Estate	0.37%	0.34%	0.15%
Nonperforming assets, number of credits or other real estate properties \| Asset	368
Loans and leases receivable, nonaccrual loans	$ 73,600,000	$ 68,700,000	$ 19,600,000
Financing Receivable, Allowance for Credit Losses on Loans	$ 351,800,000	$ 332,400,000
Allowance for Credit Losses as Percentage of Loans	1.59%	1.57%
Increase in allowance for credit losses for loans	$ 19,400,000
Increase in allowance for credit losses for loans, percentage	5.80%
Provision for credit losses	$ 9,066,000	$ 18,540,000	0
Net charge-offs	14,558,000	37,991,000	4,804,000
General reserve	15,400,000
Allowance for credit losses on off-balance sheet credit exposures	37,646,000	36,503,000	29,947,000
Commitments expected to fund	1,720,000,000
Nonaccrual loans	73,647,000	68,688,000
First Bancshares of Texas, Inc. [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans				$ 1,650,000,000
Provision for credit losses		12,000,000
Merger [Member]
Accounts Notes And Loans Receivable [Line Items]
Net charge-offs	26,100,000
LSSB Merger [Member]
Accounts Notes And Loans Receivable [Line Items]
Provision for credit losses	7,900,000
Troubled Debt Restructuring [Member]
Accounts Notes And Loans Receivable [Line Items]
Allowance for credit losses on off-balance sheet credit exposures	37,600,000	36,500,000
Troubled Debt Restructuring [Member] \| First Bancshares of Texas, Inc. [Member]
Accounts Notes And Loans Receivable [Line Items]
Provision for credit losses		6,500,000
Troubled Debt Restructuring [Member] \| LSSB Merger [Member]
Accounts Notes And Loans Receivable [Line Items]
Provision for credit losses	1,200,000
PCD Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Net charge-offs	3,400,000
Nonperforming Financial Instruments [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	$ 81,500,000	$ 72,700,000	$ 27,500,000
Nonperforming assets, number of credits or other real estate properties \| Asset		292	170
Warehouse Purchase Program [Member]
Accounts Notes And Loans Receivable [Line Items]
Participation interest in mortgage loans acquired percentage	100.00%
Loans	$ 1,080,000.00
Loans held for investment	$ 1,080,903,000	$ 822,245,000
Real Estate [Member] \| 1-4 Family Residential (Includes Home Equity) [Member]
Accounts Notes And Loans Receivable [Line Items]
Loan collateralized	89.00%
Real Estate [Member] \| Commercial Real Estate (Includes Multi-Family Residential) [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	$ 5,800,985,000	5,662,948,000
Net charge-offs	222,000	17,116,000	$ 860,000
Nonaccrual loans	$ 18,455,000	$ 18,662,000
Real Estate [Member] \| FHA and VA Loans [Member] \| 1-4 Family Residential (Includes Home Equity) [Member]
Accounts Notes And Loans Receivable [Line Items]
Debt instrument, term	30 years
Minimum [Member]
Accounts Notes And Loans Receivable [Line Items]
Loan evaluation by loan concurrence officers	$ 1,000,000
Minimum [Member] \| Consumer Portfolio Segment [Member]
Accounts Notes And Loans Receivable [Line Items]
Debt instrument, term	12 months
Minimum [Member] \| Real Estate [Member] \| 1-4 Family Residential (Includes Home Equity) [Member]
Accounts Notes And Loans Receivable [Line Items]
Debt instrument, term	5 years
Minimum [Member] \| Real Estate [Member] \| Commercial Real Estate (Includes Multi-Family Residential) [Member]
Accounts Notes And Loans Receivable [Line Items]
Debt instrument, term	15 years
Maximum [Member]
Accounts Notes And Loans Receivable [Line Items]
Loan evaluation by loan concurrence officers	$ 5,000,000
Maximum [Member] \| Consumer Portfolio Segment [Member]
Accounts Notes And Loans Receivable [Line Items]
Debt instrument, term	180 months
Maximum [Member] \| Real Estate [Member] \| 1-4 Family Residential (Includes Home Equity) [Member]
Accounts Notes And Loans Receivable [Line Items]
Debt instrument, term	30 years
Maximum [Member] \| Real Estate [Member] \| Commercial Real Estate (Includes Multi-Family Residential) [Member]
Accounts Notes And Loans Receivable [Line Items]
Period of fixed interest	5 years
Debt instrument, term	25 years