Loans Held for Investment and Allowance for Loan Losses - Loans Held-for-Investment by Class of Financing Receivables (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Sep. 30, 2023	Mar. 31, 2023	Dec. 31, 2022
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	$ 7,229,410	$ 7,148,791		$ 6,576,215
Total Real Estate	36,157	33,609		24,171
Less: Allowance for credit losses	(89,562)	(88,734)	$ (89,562)	(80,818)	$ (75,834)
Net loans held for investment	7,139,848	7,060,057		6,495,397
C&I [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	1,191,516	1,164,811		954,686
Less: Allowance for credit losses	(16,106)	(15,698)		(16,083)	(16,129)
Municipal [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	211,013	214,850		221,379
Less: Allowance for credit losses	(195)	(195)		(1,067)	(1,026)
Construction & Development [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	921,773	963,158		921,190
Less: Allowance for credit losses	(24,811)	(28,553)		(28,627)	(26,443)
Farm [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	311,002	344,954		307,706
Less: Allowance for credit losses	(2,517)	(2,914)		(1,937)	(1,957)
Non-Owner Occupied CRE [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	853,721	827,969		737,117
Less: Allowance for credit losses	(14,968)	(13,425)	(14,968)	(9,051)	(9,075)
Owner Occupied CRE [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	1,032,845	1,037,281		1,043,018
Less: Allowance for credit losses	(12,756)	(13,813)	(12,756)	(11,948)	(9,928)
Residential [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	1,918,573	1,834,593		1,628,841
Less: Allowance for credit losses	(13,565)	(11,654)	(13,565)	(9,702)	(9,075)
Auto [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	549,837	521,859		537,410
Less: Allowance for credit losses	(907)	(810)	(907)	(857)	(845)
Non-Auto [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	151,248	154,426		147,851
Less: Allowance for credit losses	(494)	(391)	$ (494)	(332)	(315)
Commercial [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	1,402,529	1,379,661		1,176,065
Commercial [Member] | C&I [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	1,191,516	1,164,811		954,686
Commercial [Member] | Municipal [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	211,013	214,850		221,379
Agriculture [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	87,882	84,890		77,017
Less: Allowance for credit losses	(3,243)	(1,281)		(1,214)	$ (1,041)
Real Estate [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	5,037,914	5,007,955		4,637,872
Real Estate [Member] | Construction & Development [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	921,773	963,158		921,190
Real Estate [Member] | Farm [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	311,002	344,954		307,706
Real Estate [Member] | Non-Owner Occupied CRE [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	853,721	827,969		737,117
Real Estate [Member] | Owner Occupied CRE [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	1,032,845	1,037,281		1,043,018
Real Estate [Member] | Residential [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	1,918,573	1,834,593		1,628,841
Consumer [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	701,085	676,285		685,261
Consumer [Member] | Auto [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	549,837	521,859		537,410
Consumer [Member] | Non-Auto [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	$ 151,248	$ 154,426		$ 147,851