Loans Held for Investment and Allowance for Loan Losses - Schedule of Past Due Loans (Detail) - USD ($) $ in Thousands		Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		$ 5,566,000	$ 5,389,000	$ 5,323,000
Total Loans		5,566,169	5,388,972	5,322,562
Total 90 Days Past Due Still Accruing		11	8	2
C&I [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		838,000	837,000	1,179,000
Total Loans		838,049	837,075	1,178,126
Municipal [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		192,000	178,000	177,000
Total Loans		191,799	177,905	176,949
Construction & Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		806,000	750,000	588,000
Total Loans		806,211	749,793	587,928
Farm [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		226,000	217,000	162,000
Total Loans		225,942	217,220	162,046
Non-Owner Occupied CRE [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		636,000	624,000	650,000
Total Loans		636,160	623,434	650,144
Owner Occupied CRE [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		881,000	822,000	760,000
Total Loans		881,181	821,653	759,906
Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		1,352,000	1,334,000	1,255,000
Total Loans		1,352,162	1,334,419	1,254,727
Auto [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		420,000	405,000	370,000
Total Loans		419,818	405,416	370,027
Non-Auto [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		132,000	124,000	92,000
Total Loans		131,964	123,968	92,343
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans		1,029,848	1,014,980	1,355,075
Total 90 Days Past Due Still Accruing			5	1
Commercial [Member] | C&I [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans		838,049	837,075	1,178,126
Total 90 Days Past Due Still Accruing			5	1
Commercial [Member] | Municipal [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans		191,799	177,905	176,949
Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans		82,883	98,089	90,366
Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans		3,901,656	3,746,519	3,414,751
Total 90 Days Past Due Still Accruing				1
Real Estate [Member] | Construction & Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans		806,211	749,793	587,928
Real Estate [Member] | Farm [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans		225,942	217,220	162,046
Real Estate [Member] | Non-Owner Occupied CRE [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans		636,160	623,434	650,144
Real Estate [Member] | Owner Occupied CRE [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans		881,181	821,653	759,906
Total 90 Days Past Due Still Accruing				1
Real Estate [Member] | Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans		1,352,162	1,334,419	1,254,727
Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans		551,782	529,384	462,370
Total 90 Days Past Due Still Accruing		11	3
Consumer [Member] | Auto [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans		419,818	405,416	370,027
Consumer [Member] | Non-Auto [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans		131,964	123,968	92,343
Total 90 Days Past Due Still Accruing		3	3
15-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	[1]	32,578	14,005	17,965
15-59 Days Past Due [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	[1]	9,124	3,701	3,488
15-59 Days Past Due [Member] | Commercial [Member] | C&I [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	[1]	8,971	3,638	3,469
15-59 Days Past Due [Member] | Commercial [Member] | Municipal [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	[1]	153	63	19
15-59 Days Past Due [Member] | Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	[1]	4,846	181	2,535
15-59 Days Past Due [Member] | Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	[1]	18,181	9,585	11,343
15-59 Days Past Due [Member] | Real Estate [Member] | Construction & Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	[1]	3,562	2,953	1,810
15-59 Days Past Due [Member] | Real Estate [Member] | Farm [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	[1]	7	600	71
15-59 Days Past Due [Member] | Real Estate [Member] | Non-Owner Occupied CRE [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	[1]	5,066	235	695
15-59 Days Past Due [Member] | Real Estate [Member] | Owner Occupied CRE [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	[1]	2,789	813	1,847
15-59 Days Past Due [Member] | Real Estate [Member] | Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	[1]	6,757	4,984	6,920
15-59 Days Past Due [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	[1]	427	538	599
15-59 Days Past Due [Member] | Consumer [Member] | Auto [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	[1]	302	393	470
15-59 Days Past Due [Member] | Consumer [Member] | Non-Auto [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	[1]	125	145	129
60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		1,445	665	433
60-89 Days Past Due [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		36	34	283
60-89 Days Past Due [Member] | Commercial [Member] | C&I [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		36	34	283
60-89 Days Past Due [Member] | Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		1,360	581	108
60-89 Days Past Due [Member] | Real Estate [Member] | Construction & Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due			39	41
60-89 Days Past Due [Member] | Real Estate [Member] | Farm [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due			215
60-89 Days Past Due [Member] | Real Estate [Member] | Non-Owner Occupied CRE [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		108
60-89 Days Past Due [Member] | Real Estate [Member] | Owner Occupied CRE [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		1,028	0
60-89 Days Past Due [Member] | Real Estate [Member] | Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		224	327	67
60-89 Days Past Due [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		49	50	42
60-89 Days Past Due [Member] | Consumer [Member] | Auto [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		49	26	31
60-89 Days Past Due [Member] | Consumer [Member] | Non-Auto [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due			24	11
Greater than 90 Days [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		2,938	915	379
Greater than 90 Days [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		1,658	222	303
Greater than 90 Days [Member] | Commercial [Member] | C&I [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		1,658	222	303
Greater than 90 Days [Member] | Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		1,257	690	66
Greater than 90 Days [Member] | Real Estate [Member] | Construction & Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		37		66
Greater than 90 Days [Member] | Real Estate [Member] | Farm [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		445
Greater than 90 Days [Member] | Real Estate [Member] | Owner Occupied CRE [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		525	280
Greater than 90 Days [Member] | Real Estate [Member] | Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		250	410
Greater than 90 Days [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		23	3	10
Greater than 90 Days [Member] | Consumer [Member] | Auto [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		20		10
Greater than 90 Days [Member] | Consumer [Member] | Non-Auto [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		3	3
Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		36,961	15,585	18,777
Total Past Due [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		10,818	3,957	4,074
Total Past Due [Member] | Commercial [Member] | C&I [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		10,665	3,894	4,055
Total Past Due [Member] | Commercial [Member] | Municipal [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		153	63	19
Total Past Due [Member] | Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		4,846	181	2,535
Total Past Due [Member] | Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		20,798	10,856	11,517
Total Past Due [Member] | Real Estate [Member] | Construction & Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		3,599	2,992	1,917
Total Past Due [Member] | Real Estate [Member] | Farm [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		452	815	71
Total Past Due [Member] | Real Estate [Member] | Non-Owner Occupied CRE [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		5,174	235	695
Total Past Due [Member] | Real Estate [Member] | Owner Occupied CRE [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		4,342	1,093	1,847
Total Past Due [Member] | Real Estate [Member] | Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		7,231	5,721	6,987
Total Past Due [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		499	591	651
Total Past Due [Member] | Consumer [Member] | Auto [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		371	419	511
Total Past Due [Member] | Consumer [Member] | Non-Auto [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		128	172	140
Current [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		5,529,208	5,373,387	5,303,785
Current [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		1,019,030	1,011,023	1,351,001
Current [Member] | Commercial [Member] | C&I [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		827,384	833,181	1,174,071
Current [Member] | Commercial [Member] | Municipal [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		191,646	177,842	176,930
Current [Member] | Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		78,037	97,908	87,831
Current [Member] | Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		3,880,858	3,735,663	3,403,234
Current [Member] | Real Estate [Member] | Construction & Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		802,612	746,801	586,011
Current [Member] | Real Estate [Member] | Farm [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		225,490	216,405	161,975
Current [Member] | Real Estate [Member] | Non-Owner Occupied CRE [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		630,986	623,199	649,449
Current [Member] | Real Estate [Member] | Owner Occupied CRE [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		876,839	820,560	758,059
Current [Member] | Real Estate [Member] | Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		1,344,931	1,328,698	1,247,740
Current [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		551,283	528,793	461,719
Current [Member] | Consumer [Member] | Auto [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		419,447	404,997	369,516
Current [Member] | Consumer [Member] | Non-Auto [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		$ 131,836	$ 123,796	$ 92,203

[1] The Company monitors commercial, agricultural and real estate loans after such loans are 15 days past due. Consumer loans are monitored after such loans are 30 days past due.