Loans Held-for-Investment and Allowance for Loan Losses - Schedule of Company's Internal Ratings of its Loans Held-for-Investment, Including The Year of Origination, by Portfolio Segments (Detail) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022
Financing Receivable, Credit Quality Indicator [Line Items]
2023	$ 582,000	$ 3,094,000	$ 711,000
2022	2,858,000	1,449,000	2,363,000
2021	1,324,000	650,000	885,000
2020	620,000	312,000	427,000
2019	293,000	220,000	319,000
Prior	751,000	567,000	743,000
Revolving Loans Amortized Cost Basis	148,000	150,000	118,000
Total	6,576,000	6,442,000	5,566,000
C&I [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	157,000	644,000	166,000
2022	557,000	163,000	449,000
2021	137,000	56,000	124,000
2020	52,000	24,000	47,000
2019	21,000	17,000	26,000
Prior	31,000	13,000	26,000
Total	955,000	917,000	838,000
Municipal [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	3,000	79,000	25,000
2022	82,000	19,000	33,000
2021	19,000	15,000	15,000
2020	15,000	4,000	5,000
2019	3,000	20,000	21,000
Prior	99,000	84,000	93,000
Total	221,000	221,000	192,000
Agriculture [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	16,000	60,000	20,000
2022	52,000	10,000	51,000
2021	5,000	3,000	6,000
2020	2,000	2,000	4,000
2019	1,000	1,000	1,000
Prior	1,000	1,000	1,000
Total	77,000	77,000	83,000
Construction & Development [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	116,000	643,000	119,000
2022	599,000	219,000	532,000
2021	125,000	70,000	107,000
2020	56,000	13,000	22,000
2019	12,000	8,000	13,000
Prior	13,000	7,000	13,000
Total	921,000	960,000	806,000
Farm [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	12,000	148,000	25,000
2022	144,000	85,000	110,000
2021	82,000	32,000	40,000
2020	31,000	11,000	13,000
2019	11,000	8,000	9,000
Prior	28,000	22,000	29,000
Total	308,000	306,000	226,000
Non-Owner Occupied CRE [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	36,000	266,000	52,000
2022	246,000	193,000	211,000
2021	195,000	102,000	129,000
2020	97,000	62,000	76,000
2019	60,000	22,000	54,000
Prior	103,000	87,000	114,000
Revolving Loans Amortized Cost Basis	0
Total	737,000	732,000	636,000
Owner Occupied CRE [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	74,000	318,000	102,000
2022	322,000	226,000	263,000
2021	250,000	130,000	140,000
2020	127,000	84,000	101,000
2019	83,000	72,000	97,000
Prior	187,000	124,000	178,000
Revolving Loans Amortized Cost Basis	0
Total	1,043,000	954,000	881,000
Residential [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	96,000	520,000	108,000
2022	485,000	361,000	448,000
2021	360,000	177,000	215,000
2020	186,000	84,000	108,000
2019	80,000	65,000	81,000
Prior	281,000	226,000	281,000
Revolving Loans Amortized Cost Basis	141,000	143,000	111,000
Total	1,629,000	1,576,000	1,352,000
Auto [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	51,000	331,000	68,000
2022	297,000	131,000	197,000
2021	116,000	56,000	90,000
2020	47,000	25,000	45,000
2019	20,000	6,000	14,000
Prior	6,000	2,000	6,000
Revolving Loans Amortized Cost Basis	0
Total	537,000	551,000	420,000
Non-Auto [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	21,000	85,000	26,000
2022	74,000	42,000	69,000
2021	35,000	9,000	19,000
2020	7,000	3,000	6,000
2019	2,000	1,000	3,000
Prior	2,000	1,000	2,000
Revolving Loans Amortized Cost Basis	7,000	7,000	7,000
Total	148,000	148,000	132,000
Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	573,000	3,054,000	704,000
2022	2,818,000	1,430,000	2,327,000
2021	1,306,000	637,000	862,000
2020	606,000	285,000	400,000
2019	266,000	208,000	302,000
Prior	706,000	531,000	702,000
Revolving Loans Amortized Cost Basis	144,000	146,000	116,000
Total	6,419,000	6,291,000	5,413,000
Pass [Member] | C&I [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	155,000	627,000	163,000
2022	548,000	157,000	438,000
2021	132,000	52,000	121,000
2020	48,000	22,000	42,000
2019	19,000	16,000	24,000
Prior	28,000	13,000	26,000
Total	930,000	887,000	814,000
Pass [Member] | Municipal [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	3,000	79,000	25,000
2022	82,000	19,000	33,000
2021	19,000	15,000	15,000
2020	15,000	4,000	5,000
2019	2,000	20,000	21,000
Prior	99,000	84,000	93,000
Total	220,000	221,000	192,000
Pass [Member] | Agriculture [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	16,000	60,000	20,000
2022	51,000	9,000	47,000
2021	5,000	3,000	6,000
2020	2,000	2,000	4,000
2019	1,000	1,000	1,000
Prior	1,000	1,000	1,000
Total	76,000	76,000	79,000
Pass [Member] | Construction & Development [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	111,000	638,000	118,000
2022	586,000	218,000	524,000
2021	124,000	70,000	106,000
2020	56,000	13,000	21,000
2019	12,000	8,000	13,000
Prior	13,000	7,000	13,000
Total	902,000	954,000	795,000
Pass [Member] | Farm [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	12,000	147,000	25,000
2022	142,000	85,000	110,000
2021	82,000	32,000	39,000
2020	31,000	11,000	13,000
2019	11,000	8,000	8,000
Prior	28,000	21,000	28,000
Total	306,000	304,000	223,000
Pass [Member] | Non-Owner Occupied CRE [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	36,000	258,000	52,000
2022	244,000	191,000	211,000
2021	192,000	100,000	123,000
2020	96,000	49,000	62,000
2019	47,000	21,000	52,000
Prior	91,000	75,000	101,000
Revolving Loans Amortized Cost Basis	0
Total	706,000	694,000	601,000
Pass [Member] | Owner Occupied CRE [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	73,000	316,000	100,000
2022	316,000	224,000	258,000
2021	247,000	128,000	136,000
2020	124,000	74,000	97,000
2019	74,000	63,000	88,000
Prior	170,000	113,000	166,000
Revolving Loans Amortized Cost Basis	0
Total	1,004,000	918,000	845,000
Pass [Member] | Residential [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	95,000	513,000	107,000
2022	479,000	355,000	441,000
2021	355,000	173,000	208,000
2020	181,000	82,000	106,000
2019	78,000	64,000	78,000
Prior	268,000	214,000	266,000
Revolving Loans Amortized Cost Basis	137,000	139,000	109,000
Total	1,593,000	1,540,000	1,315,000
Pass [Member] | Auto [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	51,000	331,000	68,000
2022	296,000	131,000	197,000
2021	116,000	55,000	89,000
2020	46,000	25,000	44,000
2019	20,000	6,000	14,000
Prior	6,000	2,000	6,000
Revolving Loans Amortized Cost Basis	0
Total	535,000	550,000	418,000
Pass [Member] | Non-Auto [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	21,000	85,000	26,000
2022	74,000	41,000	68,000
2021	34,000	9,000	19,000
2020	7,000	3,000	6,000
2019	2,000	1,000	3,000
Prior	2,000	1,000	2,000
Revolving Loans Amortized Cost Basis	7,000	7,000	7,000
Total	147,000	147,000	131,000
Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	4,000	7,000	0
2022	17,000	5,000	10,000
2021	6,000	6,000	7,000
2020	6,000	20,000	15,000
2019	19,000	0	2,000
Prior	11,000	11,000	13,000
Revolving Loans Amortized Cost Basis	1,000	1,000
Total	64,000	50,000	48,000
Special Mention [Member] | C&I [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	1,000	4,000
2022	3,000	1,000	4,000
2021	1,000	2,000
2020	2,000	1,000	3,000
2019	1,000
Total	8,000	8,000	7,000
Special Mention [Member] | Municipal [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2019	1,000
Total	1,000
Special Mention [Member] | Agriculture [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2022	1,000
Total	1,000
Special Mention [Member] | Construction & Development [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	3,000	1,000
2022	9,000		2,000
Total	12,000	1,000	2,000
Special Mention [Member] | Non-Owner Occupied CRE [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0	1,000
2021	1,000	1,000	1,000
2020	0	11,000	11,000
2019	11,000		1,000
Prior	6,000	7,000	8,000
Revolving Loans Amortized Cost Basis	0
Total	18,000	20,000	21,000
Special Mention [Member] | Owner Occupied CRE [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023		1,000
2022	3,000	0	1,000
2021	1,000	1,000	2,000
2020	2,000	8,000	1,000
2019	6,000
Prior	1,000	1,000	1,000
Revolving Loans Amortized Cost Basis	0
Total	13,000	11,000	5,000
Special Mention [Member] | Residential [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023		1,000
2022	1,000	3,000	3,000
2021	3,000	2,000	4,000
2020	2,000
2019	0	0	1,000
Prior	4,000	3,000	4,000
Revolving Loans Amortized Cost Basis	1,000	1,000	1
Total	11,000	10,000	13,000
Special Mention [Member] | Auto [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0
2022	0
2021	0
2019	0
Prior	0
Revolving Loans Amortized Cost Basis	0
Total	0
Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	5,000	33,000	7,000
2022	23,000	14,000	26,000
2021	12,000	7,000	16,000
2020	8,000	7,000	12,000
2019	8,000	12,000	15,000
Prior	34,000	25,000	28,000
Revolving Loans Amortized Cost Basis	3,000	3,000	1,000
Total	93,000	101,000	105,000
Substandard [Member] | C&I [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	1,000	13,000	3,000
2022	6,000	5,000	7,000
2021	4,000	2,000	3,000
2020	2,000	1,000	2,000
2019	1,000	1,000	2,000
Prior	3,000
Total	17,000	22,000	17,000
Substandard [Member] | Agriculture [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2022		1,000	4,000
Total		1,000	4,000
Substandard [Member] | Construction & Development [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	2,000	4,000	1,000
2022	4,000	1,000	6,000
2021	1,000		1,000
2020			1,000
Total	7,000	5,000	9,000
Substandard [Member] | Farm [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023		1,000
2022	2,000		0
2021			1,000
2019			1,000
Prior		1	1,000
Total	2,000	2,000	3,000
Substandard [Member] | Non-Owner Occupied CRE [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023		8,000
2022	2,000	1,000
2021	2,000	1,000	5,000
2020	1,000	2,000	3,000
2019	2,000	1,000	1,000
Prior	6,000	5,000	5,000
Revolving Loans Amortized Cost Basis	0
Total	13,000	18,000	14,000
Substandard [Member] | Owner Occupied CRE [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	1,000	1,000	2,000
2022	3,000	2,000	4,000
2021	2,000	1,000	2,000
2020	1,000	2,000	3,000
2019	3,000	9,000	9,000
Prior	16,000	10,000	11,000
Revolving Loans Amortized Cost Basis	0
Total	26,000	25,000	31,000
Substandard [Member] | Residential [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	1,000	6,000	1,000
2022	5,000	3,000	4,000
2021	2,000	2,000	3,000
2020	3,000	2,000	2,000
2019	2,000	1,000	2,000
Prior	9,000	9,000	11,000
Revolving Loans Amortized Cost Basis	3,000	3,000	1,000
Total	25,000	26,000	24,000
Substandard [Member] | Auto [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0
2022	1,000
2021	0	1,000	1,000
2020	1,000		1,000
2019	0
Prior	0
Revolving Loans Amortized Cost Basis	0
Total	2,000	1,000	2,000
Substandard [Member] | Non-Auto [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2022		1,000	1,000
2021	1,000
Total	$ 1,000	$ 1,000	$ 1,000