Mortgage Servicing Rights - Fair Value of Mortgage Servicing Rights (Detail) $ in Thousands	12 Months Ended
Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Servicing Assets at Fair Value [Line Items]
Contractually specified servicing fees, late fees and ancillary fees earned	$ 1,855	$ 1,917	$ 2,038
Mortgage servicing rights
Servicing Assets at Fair Value [Line Items]
Balance at beginning of period	6,200	7,098	6,687
Additions	1,526	913	557
Change in fair value	(2,634)	(1,811)	(146)
Balance at end of period	$ 5,092	$ 6,200	$ 7,098
Constant prepayment rate
Servicing Assets at Fair Value [Line Items]
Fair value of mortgage servicing rights, weighted average	0.045	0.062	0.076
Discount rate
Servicing Assets at Fair Value [Line Items]
Fair value of mortgage servicing rights, weighted average	0.120	0.120	0.120
Loans
Servicing Assets at Fair Value [Line Items]
Balance at beginning of period	$ 767,662	$ 785,138	$ 811,065
Balance at end of period	$ 779,530	$ 767,662	$ 785,138

Amount of contractually specified servicing fee, late fee, and ancillary fee recognized as income for servicing asset and servicing liability.

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The value of new servicing assets, subsequently measured at fair value, acquired or created during the current period through purchases or from transfers of financial assets.

+ References

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Fair value of an asset representing net future revenue from contractually specified servicing fees, late charges, and other ancillary revenues, in excess of future costs related to servicing arrangements.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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The increase (decrease) in the fair value of servicing assets that are subsequently measured at fair value.

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Value of input used to measure servicing asset.

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