Securities Sold Under Repurchase Agreements - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Securities Sold Under Agreements To Repurchase [Abstract]
Securities sold under repurchase , period	1 day
Securities sold under repurchase agreements	$ 7,975	$ 13,865
Repurchase agreement secured by investment securities, fair value	$ 16,500	$ 20,000
Repurchase agreement, weighted average interest rate	0.37%	0.21%

Amount, after the effects of master netting arrangements, of funds outstanding borrowed in the form of a security repurchase agreement between the entity and another party for the sale and repurchase of identical or substantially the same securities at a date certain for a specified price. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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Name:	us-gaap_SecuritiesSoldUnderAgreementsToRepurchase
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant