Loans and Allowance for Credit Losses - Troubled Debt Restructurings Identified During Period (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($) Contract	Dec. 31, 2020 USD ($) Contract	Dec. 31, 2019 USD ($) Contract
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts | Contract	30	41	38
Financing Receivable, Troubled Debt Restructuring, Premodification	$ 9,370	$ 14,874	$ 8,302
Financing Receivable, Troubled Debt Restructuring	1,690	13,969	1,928
Financing Receivable Troubled Debt Restructuring Specific Reserve	0	636	0
Contractual Payment Modification [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring, Premodification	8,901	14,098	7,525
Contractual Interest Rate Reduction [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring, Premodification	469	776	760
Extended Maturity [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring, Premodification	$ 0	$ 0	$ 17
Commercial Loan [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts | Contract	6	4	2
Financing Receivable, Troubled Debt Restructuring, Premodification	$ 7,893	$ 2,805	$ 156
Financing Receivable, Troubled Debt Restructuring	288	2,196	154
Financing Receivable Troubled Debt Restructuring Specific Reserve	$ 0	$ 636	0
Commercial Loan [Member] | Time and demand loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts | Contract	6	4
Financing Receivable, Troubled Debt Restructuring, Premodification	$ 7,893	$ 2,805
Financing Receivable, Troubled Debt Restructuring	288	2,196
Financing Receivable Troubled Debt Restructuring Specific Reserve	0	636
Commercial Loan [Member] | Contractual Payment Modification [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring, Premodification	7,893	2,176	156
Commercial Loan [Member] | Contractual Payment Modification [Member] | Time and demand loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring, Premodification	7,893	2,176
Commercial Loan [Member] | Contractual Interest Rate Reduction [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring, Premodification	0	629	0
Commercial Loan [Member] | Contractual Interest Rate Reduction [Member] | Time and demand loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring, Premodification	0	629
Commercial Loan [Member] | Extended Maturity [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring, Premodification	0	0	$ 0
Commercial Loan [Member] | Extended Maturity [Member] | Time and demand loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring, Premodification	$ 0	$ 0
Residential Real Estate [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts | Contract	15	18	20
Financing Receivable, Troubled Debt Restructuring, Premodification	$ 660	$ 950	$ 1,186
Financing Receivable, Troubled Debt Restructuring	624	791	1,059
Financing Receivable Troubled Debt Restructuring Specific Reserve	$ 0	$ 0	0
Residential Real Estate [Member] | Senior Lien
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts | Contract	12	9
Financing Receivable, Troubled Debt Restructuring, Premodification	$ 530	$ 546
Financing Receivable, Troubled Debt Restructuring	502	411
Financing Receivable Troubled Debt Restructuring Specific Reserve	$ 0	$ 0
Residential Real Estate [Member] | Junior Lien
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts | Contract	3	9
Financing Receivable, Troubled Debt Restructuring, Premodification	$ 130	$ 404
Financing Receivable, Troubled Debt Restructuring	122	380
Financing Receivable Troubled Debt Restructuring Specific Reserve	0	0
Residential Real Estate [Member] | Contractual Payment Modification [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring, Premodification	301	917	965
Residential Real Estate [Member] | Contractual Payment Modification [Member] | Senior Lien
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring, Premodification	171	513
Residential Real Estate [Member] | Contractual Payment Modification [Member] | Junior Lien
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring, Premodification	130	404
Residential Real Estate [Member] | Contractual Interest Rate Reduction [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring, Premodification	359	33	204
Residential Real Estate [Member] | Contractual Interest Rate Reduction [Member] | Senior Lien
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring, Premodification	359	33
Residential Real Estate [Member] | Contractual Interest Rate Reduction [Member] | Junior Lien
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring, Premodification	0	0
Residential Real Estate [Member] | Extended Maturity [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring, Premodification	0	0	$ 17
Residential Real Estate [Member] | Extended Maturity [Member] | Senior Lien
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring, Premodification	0	0
Residential Real Estate [Member] | Extended Maturity [Member] | Junior Lien
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring, Premodification	$ 0	$ 0
Commercial Real Estate [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts | Contract	2	5	5
Financing Receivable, Troubled Debt Restructuring, Premodification	$ 644	$ 10,857	$ 6,817
Financing Receivable, Troubled Debt Restructuring	634	10,758	594
Financing Receivable Troubled Debt Restructuring Specific Reserve	$ 0	$ 0	0
Commercial Real Estate [Member] | Nonowner Occupied Commercial Real Estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts | Contract	2	4
Financing Receivable, Troubled Debt Restructuring, Premodification	$ 644	$ 10,289
Financing Receivable, Troubled Debt Restructuring	634	10,263
Financing Receivable Troubled Debt Restructuring Specific Reserve	$ 0	$ 0
Commercial Real Estate [Member] | Owner Occupied Commercial Real Estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts | Contract	0	1
Financing Receivable, Troubled Debt Restructuring, Premodification	$ 0	$ 568
Financing Receivable, Troubled Debt Restructuring	0	495
Financing Receivable Troubled Debt Restructuring Specific Reserve	0	0
Commercial Real Estate [Member] | Contractual Payment Modification [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring, Premodification	644	10,857	6,261
Commercial Real Estate [Member] | Contractual Payment Modification [Member] | Nonowner Occupied Commercial Real Estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring, Premodification	644	10,289
Commercial Real Estate [Member] | Contractual Payment Modification [Member] | Owner Occupied Commercial Real Estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring, Premodification	0	568
Commercial Real Estate [Member] | Contractual Interest Rate Reduction [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring, Premodification	0	0	556
Commercial Real Estate [Member] | Contractual Interest Rate Reduction [Member] | Nonowner Occupied Commercial Real Estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring, Premodification	0	0
Commercial Real Estate [Member] | Contractual Interest Rate Reduction [Member] | Owner Occupied Commercial Real Estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring, Premodification	0	0
Commercial Real Estate [Member] | Extended Maturity [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring, Premodification	0	0	$ 0
Commercial Real Estate [Member] | Extended Maturity [Member] | Nonowner Occupied Commercial Real Estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring, Premodification	0	0
Commercial Real Estate [Member] | Extended Maturity [Member] | Owner Occupied Commercial Real Estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring, Premodification	$ 0	$ 0
Loans To Individuals [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts | Contract	7	14	11
Financing Receivable, Troubled Debt Restructuring, Premodification	$ 173	$ 262	$ 143
Financing Receivable, Troubled Debt Restructuring	144	224	121
Financing Receivable Troubled Debt Restructuring Specific Reserve	$ 0	$ 0	0
Loans To Individuals [Member] | Automobiles
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts | Contract	7	14
Financing Receivable, Troubled Debt Restructuring, Premodification	$ 173	$ 262
Financing Receivable, Troubled Debt Restructuring	144	224
Financing Receivable Troubled Debt Restructuring Specific Reserve	0	0
Loans To Individuals [Member] | Contractual Payment Modification [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring, Premodification	63	148	143
Loans To Individuals [Member] | Contractual Payment Modification [Member] | Automobiles
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring, Premodification	63	148
Loans To Individuals [Member] | Contractual Interest Rate Reduction [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring, Premodification	110	114	0
Loans To Individuals [Member] | Contractual Interest Rate Reduction [Member] | Automobiles
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring, Premodification	110	114
Loans To Individuals [Member] | Extended Maturity [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring, Premodification	0	0	$ 0
Loans To Individuals [Member] | Extended Maturity [Member] | Automobiles
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring, Premodification	$ 0	$ 0