Loans and Allowance for Credit Losses - Troubled Debt Restructuring is 90 Days or More Past Due (Detail) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020 USD ($) Contract	Jun. 30, 2019 USD ($) Contract	Jun. 30, 2020 USD ($) Contract	Jun. 30, 2019 USD ($) Contract
Financing Receivable, Past Due [Line Items]
Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts \| Contract	1	1	1	2
Financing Receivable, Troubled Debt Restructuring, Subsequent Default \| $	$ 50	$ 22	$ 50	$ 32
Residential real estate [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts \| Contract	1	1	1	1
Financing Receivable, Troubled Debt Restructuring, Subsequent Default \| $	$ 50	$ 22	$ 50	$ 22
Loans to individuals [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	$ 10

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=121611835&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=121611835&loc=SL6953682-111524

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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