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, 2022	Dec. 31, 2021	Dec. 31, 2020
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	$ 83,936	$ 91,366
Initial allowance on loans purchased with credit deterioration	71	8,299
Charge- offs	(2,781)	(7,845)
Recoveries	1,426	806
Net charge-offs	(1,355)	(7,039)
Provision for credit losses on loans	10,076	(8,690)	$ 62,648
Balance at end of period	92,728	83,936	91,366
Real Estate [Member] | Commercial Real Estate Owner Occupied [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	7,568	8,470
Initial allowance on loans purchased with credit deterioration		1,080
Charge- offs	(20)	(38)
Recoveries	507	74
Net charge-offs	487	36
Provision for credit losses on loans	(1,643)	(2,018)
Balance at end of period	6,412	7,568	8,470
Real Estate [Member] | Commercial Real Estate Non-Owner Occupied [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	16,987	12,318
Initial allowance on loans purchased with credit deterioration		824
Charge- offs		(803)
Recoveries		67
Net charge-offs		(736)
Provision for credit losses on loans	13,205	4,581
Balance at end of period	30,192	16,987	12,318
Real Estate [Member] | Construction and Development Less than 60 Months [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	3,490	2,723
Initial allowance on loans purchased with credit deterioration		173
Charge- offs	(93)
Recoveries	12	12
Net charge-offs	(81)	12
Provision for credit losses on loans	369	582
Balance at end of period	3,778	3,490	2,723
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	1,092	726
Provision for credit losses on loans	2,184	366
Balance at end of period	3,276	1,092	726
Real Estate [Member] | Residential Real Estate First Lien [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	3,076	2,822
Initial allowance on loans purchased with credit deterioration	2	126
Charge- offs	(106)	(87)
Recoveries	87	55
Net charge-offs	(19)	(32)
Provision for credit losses on loans	1,039	160
Balance at end of period	4,098	3,076	2,822
Real Estate [Member] | Residential Real Estate All Other [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	2,104	2,236
Charge- offs	(38)	(521)
Recoveries	405	52
Net charge-offs	367	(469)
Provision for credit losses on loans	(626)	337
Balance at end of period	1,845	2,104	2,236
Commercial and Agricultural Non-Real Estate [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	28,085	34,643
Initial allowance on loans purchased with credit deterioration	44	5,663
Charge- offs	(1,756)	(4,643)
Recoveries	222	219
Net charge-offs	(1,534)	(4,424)
Provision for credit losses on loans	716	(7,797)
Balance at end of period	27,311	28,085	34,643
Consumer Non-real Estate [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	3,734	3,542
Initial allowance on loans purchased with credit deterioration	25	38
Charge- offs	(768)	(864)
Recoveries	193	326
Net charge-offs	(575)	(538)
Provision for credit losses on loans	951	692
Balance at end of period	4,135	3,734	3,542
Oil and Gas [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	12,978	20,733
Provision for credit losses on loans	(4,807)	(7,755)
Balance at end of period	8,171	12,978	20,733
Farmland [Member] | Real Estate [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	4,822	3,153
Initial allowance on loans purchased with credit deterioration		395
Charge- offs		(889)
Recoveries		1
Net charge-offs		(888)
Provision for credit losses on loans	(1,312)	2,162
Balance at end of period	$ 3,510	$ 4,822	$ 3,153