Disclosures about Fair Value of Assets and Liabilities - Additional Information (Detail) - USD ($)	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Reduced in carrying amount of mortgage servicing rights	$ 14,000	$ 6,000

The increase (decrease) in the fair value of servicing assets that are subsequently measured at fair value.

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

Name:	us-gaap_ServicingAssetAtFairValuePeriodIncreaseDecrease
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration