Loans and Allowance for Credit Losses - Troubled Debt Restructurings Identified During Period (Detail) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($) Contract	Sep. 30, 2022 USD ($) Contract	Sep. 30, 2021 USD ($) Contract
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract		15	2	28
Total Pre-Modification Outstanding Recorded Investment	$ 0	$ 1,160	$ 69	$ 8,140
Post- Modification Outstanding Recorded Investment		1,144	68	4,191
Troubled Debt Restructuring [Policy Text Block]		$ 0	$ 0	$ 0
Commercial, financial, agricultural and other [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract		5		6
Total Pre-Modification Outstanding Recorded Investment		$ 206		$ 6,803
Post- Modification Outstanding Recorded Investment		202		2,895
Troubled Debt Restructuring [Policy Text Block]		$ 0		$ 0
Residential real estate [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract		5	2	13
Total Pre-Modification Outstanding Recorded Investment		$ 230	$ 69	$ 520
Post- Modification Outstanding Recorded Investment		221	68	500
Troubled Debt Restructuring [Policy Text Block]		$ 0	$ 0	$ 0
Loans to individuals [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract		3		7
Total Pre-Modification Outstanding Recorded Investment		$ 80		$ 173
Post- Modification Outstanding Recorded Investment		76		151
Troubled Debt Restructuring [Policy Text Block]		$ 0		$ 0
Commercial Real Estate [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract		2		2
Total Pre-Modification Outstanding Recorded Investment		$ 644		$ 644
Post- Modification Outstanding Recorded Investment		645		645
Troubled Debt Restructuring [Policy Text Block]		$ 0		$ 0
Time and Demand Loans | Commercial, financial, agricultural and other [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract		5		6
Total Pre-Modification Outstanding Recorded Investment		$ 206		$ 6,803
Post- Modification Outstanding Recorded Investment		202		2,895
Troubled Debt Restructuring [Policy Text Block]		$ 0		$ 0
Senior Lien | Residential real estate [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract		3	2	10
Total Pre-Modification Outstanding Recorded Investment		$ 113	$ 69	$ 390
Post- Modification Outstanding Recorded Investment		109	68	375
Troubled Debt Restructuring [Policy Text Block]		$ 0	0	$ 0
Junior Lien | Residential real estate [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract		2		3
Total Pre-Modification Outstanding Recorded Investment		$ 117		$ 130
Post- Modification Outstanding Recorded Investment		112		125
Troubled Debt Restructuring [Policy Text Block]		$ 0		$ 0
Automobiles | Loans to individuals [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract		3		7
Total Pre-Modification Outstanding Recorded Investment		$ 80		$ 173
Post- Modification Outstanding Recorded Investment		76		151
Troubled Debt Restructuring [Policy Text Block]		$ 0		$ 0
Nonowner Occupied Commercial Real Estate | Commercial Real Estate [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract		2		2
Total Pre-Modification Outstanding Recorded Investment		$ 644		$ 644
Post- Modification Outstanding Recorded Investment		645		645
Troubled Debt Restructuring [Policy Text Block]		0		0
Extended Maturity [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment		0	0	0
Extended Maturity [Member] | Commercial, financial, agricultural and other [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment		0		0
Extended Maturity [Member] | Residential real estate [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment		0	0	0
Extended Maturity [Member] | Loans to individuals [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment		0		0
Extended Maturity [Member] | Commercial Real Estate [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment		0		0
Extended Maturity [Member] | Time and Demand Loans | Commercial, financial, agricultural and other [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment		0		0
Extended Maturity [Member] | Senior Lien | Residential real estate [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment		0	0	0
Extended Maturity [Member] | Junior Lien | Residential real estate [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment		0		0
Extended Maturity [Member] | Automobiles | Loans to individuals [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment		0		0
Extended Maturity [Member] | Nonowner Occupied Commercial Real Estate | Commercial Real Estate [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment		0		0
Contractual Interest Rate Reduction [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment		130	10	329
Contractual Interest Rate Reduction [Member] | Commercial, financial, agricultural and other [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment		0		0
Contractual Interest Rate Reduction [Member] | Residential real estate [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment		113	10	219
Contractual Interest Rate Reduction [Member] | Loans to individuals [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment		17		110
Contractual Interest Rate Reduction [Member] | Commercial Real Estate [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment		0		0
Contractual Interest Rate Reduction [Member] | Time and Demand Loans | Commercial, financial, agricultural and other [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment		0		0
Contractual Interest Rate Reduction [Member] | Senior Lien | Residential real estate [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment		113	10	219
Contractual Interest Rate Reduction [Member] | Junior Lien | Residential real estate [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment		0		0
Contractual Interest Rate Reduction [Member] | Automobiles | Loans to individuals [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment		17		110
Contractual Interest Rate Reduction [Member] | Nonowner Occupied Commercial Real Estate | Commercial Real Estate [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment		0		0
Contractual Payment Modification [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment		1,030	59	7,811
Contractual Payment Modification [Member] | Commercial, financial, agricultural and other [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment		206		6,803
Contractual Payment Modification [Member] | Residential real estate [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment		117	59	301
Contractual Payment Modification [Member] | Loans to individuals [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment		63		63
Contractual Payment Modification [Member] | Commercial Real Estate [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment		644		644
Contractual Payment Modification [Member] | Time and Demand Loans | Commercial, financial, agricultural and other [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment		206		6,803
Contractual Payment Modification [Member] | Senior Lien | Residential real estate [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment		0	$ 59	171
Contractual Payment Modification [Member] | Junior Lien | Residential real estate [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment		117		130
Contractual Payment Modification [Member] | Automobiles | Loans to individuals [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment		63		63
Contractual Payment Modification [Member] | Nonowner Occupied Commercial Real Estate | Commercial Real Estate [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Pre-Modification Outstanding Recorded Investment		$ 644		$ 644