Loans Held for Investment and Allowance for Credit Losses on Loans - Activity in Allowance for Credit Losses on Loans (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	$ 92,728	$ 83,936
Initial allowance on loans purchased with credit deterioration		71
Charge- offs	(4,240)	(2,781)
Recoveries	854	1,426
Net charge-offs	(3,386)	(1,355)
Provision for/(benefit from) credit losses	7,458	10,076	$ (8,690)
Balance at end of period	96,800	92,728	83,936
Real Estate [Member] | Commercial Real Estate Owner Occupied [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	6,416	7,550
Charge- offs	(922)	(20)
Recoveries	68	507
Net charge-offs	(854)	487
Provision for/(benefit from) credit losses	1,921	(1,621)
Balance at end of period	7,483	6,416	7,550
Real Estate [Member] | Commercial Real Estate Non-Owner Occupied [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	30,190	16,807
Charge- offs	(3)
Net charge-offs	(3)
Provision for/(benefit from) credit losses	2,893	13,383
Balance at end of period	33,080	30,190	16,807
Real Estate [Member] | Construction and Development Less than 60 Months [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	3,778	3,454
Charge- offs	(6)	(93)
Recoveries	11	12
Net charge-offs	5	(81)
Provision for/(benefit from) credit losses	167	405
Balance at end of period	3,950	3,778	3,454
Real Estate [Member] | Construction Residential Real Estate Less than 60 Months [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	3,275	1,051
Charge- offs	(94)
Net charge-offs	(94)
Provision for/(benefit from) credit losses	233	2,224
Balance at end of period	3,414	3,275	1,051
Real Estate [Member] | Residential Real Estate First Lien [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	4,092	3,048
Initial allowance on loans purchased with credit deterioration		2
Charge- offs	(165)	(106)
Recoveries	15	87
Net charge-offs	(150)	(19)
Provision for/(benefit from) credit losses	972	1,061
Balance at end of period	4,914	4,092	3,048
Real Estate [Member] | Residential Real Estate All Other [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	1,418	1,567
Charge- offs	(60)	(38)
Recoveries	5	405
Net charge-offs	(55)	367
Provision for/(benefit from) credit losses	283	(516)
Balance at end of period	1,646	1,418	1,567
Commercial Non-real Estate [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	25,106	25,565
Initial allowance on loans purchased with credit deterioration		44
Charge- offs	(1,085)	(1,551)
Recoveries	446	209
Net charge-offs	(639)	(1,342)
Provision for/(benefit from) credit losses	(1,722)	839
Balance at end of period	22,745	25,106	25,565
Consumer Non-real Estate [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	4,132	3,694
Initial allowance on loans purchased with credit deterioration		25
Charge- offs	(1,350)	(768)
Recoveries	182	193
Net charge-offs	(1,168)	(575)
Provision for/(benefit from) credit losses	1,437	988
Balance at end of period	4,401	4,132	3,694
Oil and Gas [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	8,104	12,808
Charge- offs	(59)
Net charge-offs	(59)
Provision for/(benefit from) credit losses	985	(4,704)
Balance at end of period	9,030	8,104	12,808
Agriculture [Member] | Real Estate [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	6,217	8,392
Charge- offs	(496)	(205)
Recoveries	127	13
Net charge-offs	(369)	(192)
Provision for/(benefit from) credit losses	289	(1,983)
Balance at end of period	$ 6,137	$ 6,217	$ 8,392