Loans and Allowance for Credit Losses - Schedule of Loans by Class Modified as Troubled Debt Restructuring (Detail) $ in Thousands	9 Months Ended
Sep. 30, 2020 USD ($) loan	Sep. 30, 2019 USD ($) loan
Receivables [Abstract]
Number of loans \| loan	1	14
Pre-modification outstanding recorded investment	$ 5,907	$ 21,132
Post-modification outstanding recorded investment	$ 5,907	$ 21,132

Number of financing receivables that have been modified by troubled debt restructurings.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953676-111524

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- Definition

Amount, after troubled debt restructuring, of modified financing receivable.

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- Definition

Amount, before troubled debt restructuring, of financing receivable to be modified.

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