Mortgage Servicing Rights - Fair Value of Mortgage Servicing Rights (Detail) $ in Thousands	12 Months Ended
Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Servicing Assets at Fair Value [Line Items]
Contractually specified servicing fees, late fees and ancillary fees earned	$ 2,038	$ 2,076	$ 2,065
Mortgage Servicing Rights [Member]
Servicing Assets at Fair Value [Line Items]
Balance at beginning of period	6,687	6,595	7,618
Additions	557	810	1,161
Change in fair value	(146)	(718)	(2,184)
Balance at end of period	$ 7,098	$ 6,687	$ 6,595
Measurement Input, Constant Prepayment Rate [Member]
Servicing Assets at Fair Value [Line Items]
Fair Value Of Mortgage Servicing Rights Weighted Average	0.076	0.089	0.088
Measurement Input, Discount Rate [Member]
Servicing Assets at Fair Value [Line Items]
Fair Value Of Mortgage Servicing Rights Weighted Average	0.120	0.130	0.140
Loans [Member]
Servicing Assets at Fair Value [Line Items]
Balance at beginning of period	$ 811,065	$ 816,623	$ 817,917
Balance at end of period	$ 785,138	$ 811,065	$ 816,623

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

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-Publisher FASB
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-Subparagraph (c)
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- Definition

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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-Publisher FASB
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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
-Publisher FASB
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-Topic 860
-SubTopic 50
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-URI http://asc.fasb.org/extlink&oid=6469459&loc=d3e122501-111745

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
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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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