Allowance for Loan Losses and Credit Quality Information - Summary of Balance of TDRs (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Modifications [Line Items]
Balance of TDRs	$ 25,164	$ 29,688
Performing
Financing Receivable, Modifications [Line Items]
Balance of TDRs	14,953	20,061
Nonperforming
Financing Receivable, Modifications [Line Items]
Balance of TDRs	$ 10,211	$ 9,627

The amount of the outstanding recorded investment related to financing receivables that have been modified by troubled debt restructurings.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=82895541&loc=d3e18845-111554

Name:	us-gaap_FinancingReceivableModificationsRecordedInvestment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant