Loans and Allowance for Credit Losses - Troubled Debt Restructuring is 90 Days or More Past Due (Detail) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2021 USD ($) Contract	Sep. 30, 2020 USD ($) Contract	Sep. 30, 2021 USD ($) Contract	Sep. 30, 2020 USD ($) Contract
Financing Receivable, Past Due [Line Items]
Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts \| Contract	0	3	0	4
Financing Receivable, Troubled Debt Restructuring, Subsequent Default \| $	$ 0	$ 190	$ 0	$ 240
Residential real estate [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts \| Contract			0	1
Financing Receivable, Troubled Debt Restructuring, Subsequent Default \| $			$ 0	$ 50
Commercial Real Estate [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts \| Contract	0	1	0	1
Financing Receivable, Troubled Debt Restructuring, Subsequent Default \| $	$ 0	$ 112	$ 0	$ 112
Loans to individuals [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts \| Contract	0	2	0	2
Financing Receivable, Troubled Debt Restructuring, Subsequent Default \| $	$ 0	$ 78	$ 0	$ 78

Number of financing receivable contracts modified as troubled debt restructuring within previous 12 months, with subsequent payment default.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=123577603&loc=SL6953682-111524

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- Definition

Amount of financing receivable modified as troubled debt restructuring within previous 12 months, with subsequent payment default.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=123577603&loc=SL6953682-111524

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+ References

No definition available.

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