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, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	$ 100,455	$ 97,267	$ 99,497	$ 96,800
Charge- offs	(5,066)	(1,377)	(5,849)	(5,068)
Recoveries	360	378	640	521
Net charge-offs	(4,706)	(999)	(5,209)	(4,547)
Provision for/(benefit from) credit losses	1,239	3,358	2,700	7,373
Balance at end of period	96,988	99,626	96,988	99,626
Real Estate [Member] | Commercial Real Estate Owner Occupied [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	6,991	7,468	6,869	7,483
Charge- offs	(58)		(81)	(15)
Recoveries	2	11	41	31
Net charge-offs	(56)	11	(40)	16
Provision for/(benefit from) credit losses	313	(109)	419	(129)
Balance at end of period	7,248	7,370	7,248	7,370
Real Estate [Member] | Commercial Real Estate Non-Owner Occupied [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	33,753	33,180	33,097	33,080
Charge- offs	(228)	(1)	(228)	(14)
Net charge-offs	(228)	(1)	(228)	(14)
Provision for/(benefit from) credit losses	1,692	688	2,348	801
Balance at end of period	35,217	33,867	35,217	33,867
Real Estate [Member] | Construction and Development Less than 60 Months [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	8,613	6,596	8,671	3,950
Charge- offs	(3,741)		(3,744)
Recoveries	6		6
Net charge-offs	(3,735)		(3,738)
Provision for/(benefit from) credit losses	29	184	(26)	2,830
Balance at end of period	4,907	6,780	4,907	6,780
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	2,282	3,464	2,336	3,414
Charge- offs			(25)	(3)
Recoveries	3		3
Net charge-offs	3		(22)	(3)
Provision for/(benefit from) credit losses	(20)	55	(49)	108
Balance at end of period	2,265	3,519	2,265	3,519
Real Estate [Member] | Residential Real Estate First Lien [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	4,666	4,923	4,568	4,914
Charge- offs	(5)	(67)	(56)	(90)
Recoveries	9	21	12	25
Net charge-offs	4	(46)	(44)	(65)
Provision for/(benefit from) credit losses	(25)	695	121	723
Balance at end of period	4,645	5,572	4,645	5,572
Real Estate [Member] | Residential Real Estate All Other [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	1,790	1,652	1,741	1,646
Charge- offs	(7)		(13)	(29)
Recoveries	0	3	21	8
Net charge-offs	(7)	3	8	(21)
Provision for/(benefit from) credit losses	38	74	72	104
Balance at end of period	1,821	1,729	1,821	1,729
Real Estate [Member] | Agriculture [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	5,776	6,137	5,696	6,137
Charge- offs	(7)	(19)	(34)	(50)
Recoveries	7	5	18	17
Net charge-offs		(14)	(16)	(33)
Provision for/(benefit from) credit losses	(645)	(206)	(549)	(187)
Balance at end of period	5,131	5,917	5,131	5,917
Commercial Non-real Estate [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	23,877	20,482	24,150	22,745
Charge- offs	(526)	(780)	(727)	(3,834)
Recoveries	250	280	375	313
Net charge-offs	(276)	(500)	(352)	(3,521)
Provision for/(benefit from) credit losses	446	1,493	249	2,251
Balance at end of period	24,047	21,475	24,047	21,475
Consumer Non-real Estate [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	4,820	4,335	4,833	4,401
Charge- offs	(494)	(510)	(941)	(941)
Recoveries	83	58	164	127
Net charge-offs	(411)	(452)	(777)	(814)
Provision for/(benefit from) credit losses	428	500	781	796
Balance at end of period	4,837	4,383	4,837	4,383
Oil and Gas [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	7,887	9,030	7,536	9,030
Charge- offs				(92)
Net charge-offs				(92)
Provision for/(benefit from) credit losses	(1,017)	(16)	(666)	76
Balance at end of period	$ 6,870	$ 9,014	$ 6,870	$ 9,014