Derivative Instruments and Other Hedging Activities - Effect of Hedging Instruments on Consolidated Financial Statements (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Derivatives designated as hedging instruments \| Cash Flow Hedging \| Interest rate contracts \| Interest expense
Derivative Instruments and Hedging Activities Disclosures
Amount of gain (loss) recognized	$ (388)	$ (196)	$ (390)
Derivative, included component, gain (loss) recognized in earnings	559	(150)
Amount of gain (loss) recognized in income on derivatives (amount excluded from effectiveness testing)	(947)	(46)	0
Other Comprehensive Income (Loss), Net of Tax	0	0
Gain (Loss) from Components Included in Assessment of Cash Flow Hedge Effectiveness	0	0
Gain (Loss) from Components Excluded from Assessment of Cash Flow Hedge Effectiveness, Net	0	0
Derivatives not designated as hedging instruments
Derivative Instruments and Hedging Activities Disclosures
Amount of gain (loss) recognized	6,763	11,211	(1,299)
Derivatives not designated as hedging instruments \| Interest rate contracts \| Commission income
Derivative Instruments and Hedging Activities Disclosures
Amount of gain (loss) recognized	15,071	6,962	4,750
Derivatives not designated as hedging instruments \| Foreign exchange contracts \| Commission income
Derivative Instruments and Hedging Activities Disclosures
Amount of gain (loss) recognized	15	29	43
Derivatives not designated as hedging instruments \| Forward sales contracts \| Mortgage income
Derivative Instruments and Hedging Activities Disclosures
Amount of gain (loss) recognized	(8,909)	4,064	(4,115)
Derivatives not designated as hedging instruments \| Written and purchased options \| Mortgage income
Derivative Instruments and Hedging Activities Disclosures
Amount of gain (loss) recognized	677	180	(2,028)
Derivatives not designated as hedging instruments \| Other contracts \| Commission income
Derivative Instruments and Hedging Activities Disclosures
Amount of gain (loss) recognized	(91)	(24)	51
OCI \| Derivatives designated as hedging instruments \| Cash Flow Hedging \| Interest rate contracts
Derivative Instruments and Hedging Activities Disclosures
Amount of gain (loss) recognized	1,078	4,416	$ (611)
Derivative, included component, gain (loss) recognized in earnings	2,340	4,835
Amount of gain (loss) recognized in income on derivatives (amount excluded from effectiveness testing)	$ (1,262)	$ (419)

Derivative, Included Component, Gain (Loss) Recognized in Earnings

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Other Comprehensive Income (Loss), Derivative, Included Component, Increase (Decrease), Before Adjustments and Tax

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- Definition

Amount of gain (loss) from excluded component of derivative hedge, recognized in earnings. Excludes recognition under systematic and rational method.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 20
-Section 45
-Paragraph 1A
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Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Amount, after reclassification, of tax expense (benefit) for gain (loss) from derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
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Amount, before adjustments, of tax expense (benefit) for gain (loss) from increase (decrease) in value of excluded component of derivative designated and qualifying as hedge. Adjustments include, but are not limited to, reclassifications for sale and settlement, and amounts recognized under systematic and rational method.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 20
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109974929&loc=SL110061190-113977

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