Mortgage Servicing Rights - Additional Information (Detail) - USD ($)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Risks Inherent in Servicing Assets and Servicing Liabilities [Line Items]
Unpaid principal balance of mortgage loans serviced for others	$ 336,722,000	$ 332,515,000
Mortgage servicing rights, valuation allowance	$ 0	$ 0
Minimum [Member]
Risks Inherent in Servicing Assets and Servicing Liabilities [Line Items]
Discount rates used in valuation model	10.00%	10.00%
Prepayment speeds used in valuation model	7.00%	7.00%
Maximum [Member]
Risks Inherent in Servicing Assets and Servicing Liabilities [Line Items]
Discount rates used in valuation model	14.00%	14.00%
Prepayment speeds used in valuation model	45.00%	43.00%

Unpaid Principal Balance of Loans Serviced for Others

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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.

+ Details

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- Definition

Amount of increase (decrease) in the amortized amount from a decrease (increase) in the valuation allowance applied to the servicing asset for a contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 4
-Subparagraph (a)(5)
-URI http://asc.fasb.org/extlink&oid=116651436&loc=d3e122739-111746

+ Details

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- Definition

Discount rate used to estimate the fair value of servicing assets and servicing liabilities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 2
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=116651436&loc=d3e122596-111746

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- Definition

Estimated rate of prepayments of principal on servicing assets and servicing liabilities.

+ References

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