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		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	$ 97,267	$ 94,760	$ 96,800	$ 92,728
Charge- offs	(1,377)	(850)	(5,068)	(1,282)
Recoveries	378	186	521	328
Net charge-offs	(999)	(664)	(4,547)	(954)
Provision for/(benefit from) credit losses	3,358	2,824	7,373	5,146
Balance at end of period	99,626	96,920	99,626	96,920
Real Estate [Member] | Commercial Real Estate Owner Occupied [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	7,468	6,547	7,483	6,416
Charge- offs			(15)	(48)
Recoveries	11	3	31	52
Net charge-offs	(11)	3	16	4
Provision for/(benefit from) credit losses	(109)	258	(129)	388
Balance at end of period	7,370	6,808	7,370	6,808
Real Estate [Member] | Commercial Real Estate Non-Owner Occupied [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	33,180	32,120	33,080	30,190
Charge- offs	(1)		(14)	(3)
Recoveries
Net charge-offs	(1)		(14)	(3)
Provision for/(benefit from) credit losses	688	1,312	801	3,245
Balance at end of period	33,867	33,432	33,867	33,432
Real Estate [Member] | Construction and Development Less than 60 Months [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	6,596	3,608	3,950	3,778
Charge- offs		(2)		(4)
Recoveries		3		6
Net charge-offs		1		2
Provision for/(benefit from) credit losses	(184)	(169)	2,830	(340)
Balance at end of period	6,780	3,440	6,780	3,440
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	3,464	3,226	3,414	3,275
Charge- offs			(3)
Net charge-offs			(3)
Provision for/(benefit from) credit losses	55	327	108	278
Balance at end of period	3,519	3,553	3,519	3,553
Real Estate [Member] | Residential Real Estate First Lien [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	4,923	4,454	4,914	4,092
Charge- offs	(67)	(42)	(90)	(44)
Recoveries	21	10	25	13
Net charge-offs	(46)	(32)	(65)	(31)
Provision for/(benefit from) credit losses	695	333	723	694
Balance at end of period	5,572	4,755	5,572	4,755
Real Estate [Member] | Residential Real Estate All Other [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	1,652	1,444	1,646	1,418
Charge- offs		(2)	(29)	(28)
Recoveries	3	1	8	3
Net charge-offs	3	(1)	(21)	(25)
Provision for/(benefit from) credit losses	74	218	104	268
Balance at end of period	1,729	1,661	1,729	1,661
Commercial Non-real Estate [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	20,482	25,079	22,745	25,106
Charge- offs	(780)	(102)	(3,834)	(278)
Recoveries	280	127	313	149
Net charge-offs	(500)	25	(3,521)	(129)
Provision for/(benefit from) credit losses	1,493	23	2,251	150
Balance at end of period	21,475	25,127	21,475	25,127
Consumer Non-real Estate [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	4,335	4,232	4,401	4,132
Charge- offs	(510)	(398)	(941)	(538)
Recoveries	58	35	127	92
Net charge-offs	(452)	(363)	(814)	(446)
Provision for/(benefit from) credit losses	500	475	796	658
Balance at end of period	4,383	4,344	4,383	4,344
Oil and Gas [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	9,030	7,782	9,030	8,104
Charge- offs		(2)	(92)	(2)
Net charge-offs		(2)	(92)	(2)
Provision for/(benefit from) credit losses	(16)	(406)	76	(728)
Balance at end of period	9,014	7,374	9,014	7,374
Agriculture [Member] | Real Estate [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	6,137	6,268	6,137	6,217
Charge- offs	(19)	(302)	(50)	(337)
Recoveries	5	7	17	13
Net charge-offs	(14)	(295)	(33)	(324)
Provision for/(benefit from) credit losses	(206)	453	(187)	533
Balance at end of period	$ 5,917	$ 6,426	$ 5,917	$ 6,426