Loans Held for Investment and Allowance for Credit Losses on Loans - Activity in Allowance for Credit Losses on Loans (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	$ 96,800	$ 92,728
Charge- offs	(3,691)	(432)
Recoveries	143	142
Net charge-offs	(3,548)	(290)
Provision for/(benefit from) credit losses	4,015	2,322
Balance at end of period	97,267	94,760
Real Estate [Member] | Commercial Real Estate Owner Occupied [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	7,483	6,416
Charge- offs	(15)	(48)
Recoveries	20	49
Net charge-offs	5	1
Provision for/(benefit from) credit losses	(20)	130
Balance at end of period	7,468	6,547
Real Estate [Member] | Commercial Real Estate Non-Owner Occupied [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	33,080	30,190
Charge- offs	(13)	(3)
Net charge-offs	(13)	(3)
Provision for/(benefit from) credit losses	113	1,933
Balance at end of period	33,180	32,120
Real Estate [Member] | Construction and Development Less than 60 Months [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	3,950	3,778
Charge- offs		(2)
Recoveries		3
Net charge-offs		1
Provision for/(benefit from) credit losses	2,646	(171)
Balance at end of period	6,596	3,608
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	3,414	3,275
Charge- offs	(3)
Net charge-offs	(3)
Provision for/(benefit from) credit losses	53	(49)
Balance at end of period	3,464	3,226
Real Estate [Member] | Residential Real Estate First Lien [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	4,914	4,092
Charge- offs	(23)	(2)
Recoveries	4	3
Net charge-offs	(19)	1
Provision for/(benefit from) credit losses	28	361
Balance at end of period	4,923	4,454
Real Estate [Member] | Residential Real Estate All Other [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	1,646	1,418
Charge- offs	(29)	(26)
Recoveries	5	2
Net charge-offs	(24)	(24)
Provision for/(benefit from) credit losses	30	50
Balance at end of period	1,652	1,444
Commercial Non-real Estate [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	22,745	25,106
Charge- offs	(3,054)	(176)
Recoveries	33	22
Net charge-offs	(3,021)	(154)
Provision for/(benefit from) credit losses	758	127
Balance at end of period	20,482	25,079
Consumer Non-real Estate [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	4,401	4,132
Charge- offs	(431)	(140)
Recoveries	69	57
Net charge-offs	(362)	(83)
Provision for/(benefit from) credit losses	296	183
Balance at end of period	4,335	4,232
Oil and Gas [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	9,030	8,104
Charge- offs	(92)
Net charge-offs	(92)
Provision for/(benefit from) credit losses	92	(322)
Balance at end of period	9,030	7,782
Agriculture [Member] | Real Estate [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	6,137	6,217
Charge- offs	(31)	(35)
Recoveries	12	6
Net charge-offs	(19)	(29)
Provision for/(benefit from) credit losses	19	80
Balance at end of period	$ 6,137	$ 6,268