Disclosures About Fair Value of Financial Instruments - Narrative (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held for sale, average life from purchase to sale		30 days
Significant Unobservable Inputs (Level 3) \| Interest-only GNMA securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Settlements	$ (900)	$ (1,900)

Amount of settlement of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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 (c)(2)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration