Fair Value - Schedule of Balances of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Available-for-sale securities:
Available-for-sale securities	$ 82,232	$ 77,153
Mortgage servicing rights	977	999
Corporate Bonds
Available-for-sale securities:
Available-for-sale securities	12,133	6,717
US Government Agencies Agencies and Mortgage Backed Securities
Available-for-sale securities:
Available-for-sale securities	49,882	49,283
State and Municipal Obligations
Available-for-sale securities:
Available-for-sale securities	20,217	21,153
Fair Value, Measurements, Recurring
Available-for-sale securities:
Available-for-sale securities	82,232	77,153
Mortgage servicing rights	977	999
Rabbi trust assets	972	926
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 1
Available-for-sale securities:
Rabbi trust assets	972	926
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 2
Available-for-sale securities:
Available-for-sale securities	78,561	75,653
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 3
Available-for-sale securities:
Available-for-sale securities	3,671	1,500
Mortgage servicing rights	977	999
Fair Value, Measurements, Recurring \| Corporate Bonds
Available-for-sale securities:
Available-for-sale securities	12,133	6,717
Fair Value, Measurements, Recurring \| Corporate Bonds \| Fair Value, Inputs, Level 2
Available-for-sale securities:
Available-for-sale securities	8,462	5,217
Fair Value, Measurements, Recurring \| Corporate Bonds \| Fair Value, Inputs, Level 3
Available-for-sale securities:
Available-for-sale securities	3,671	1,500
Fair Value, Measurements, Recurring \| US Government Agencies Agencies and Mortgage Backed Securities
Available-for-sale securities:
Available-for-sale securities	49,882	49,283
Fair Value, Measurements, Recurring \| US Government Agencies Agencies and Mortgage Backed Securities \| Fair Value, Inputs, Level 2
Available-for-sale securities:
Available-for-sale securities	49,882	49,283
Fair Value, Measurements, Recurring \| State and Municipal Obligations
Available-for-sale securities:
Available-for-sale securities	20,217	21,153
Fair Value, Measurements, Recurring \| State and Municipal Obligations \| Fair Value, Inputs, Level 2
Available-for-sale securities:
Available-for-sale securities	$ 20,217	$ 21,153

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

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- References

No definition available.

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- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109979856&loc=d3e26610-111562

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

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- Definition

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
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6469459&loc=d3e122501-111745

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=68078379&loc=d3e122625-111746

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