Derivative Instruments and Other Hedging Activities - Effect of Hedging Instruments on Consolidated Financial Statements (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Designated as Hedging Instruments \| Cash Flow Hedging \| Interest rate contracts \| Interest expense
Derivative Instruments and Hedging Activities Disclosures
Amount of Gain (Loss) Recognized	$ (196)	$ (390)	$ 50
Derivative, Included Component, Gain (Loss) Recognized in Earnings	(150)
Amount of Gain (Loss) Recognized in Income on Derivatives (Amount Excluded from Effectiveness Testing)	(46)	0	0
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net	0
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Included Component Net	0
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Excluding Compnonent, Net	0
Not Designated as Hedging Instruments
Derivative Instruments and Hedging Activities Disclosures
Amount of Gain (Loss) Recognized	11,211	(1,299)	6,804
Not Designated as Hedging Instruments \| Interest rate contracts \| Other income
Derivative Instruments and Hedging Activities Disclosures
Amount of Gain (Loss) Recognized	6,962	4,750	8,830
Not Designated as Hedging Instruments \| Foreign exchange contracts \| Other income
Derivative Instruments and Hedging Activities Disclosures
Amount of Gain (Loss) Recognized	29	43	15
Not Designated as Hedging Instruments \| Forward sales contracts \| Mortgage income
Derivative Instruments and Hedging Activities Disclosures
Amount of Gain (Loss) Recognized	4,064	(4,115)	(1,731)
Not Designated as Hedging Instruments \| Written and purchased options \| Mortgage income
Derivative Instruments and Hedging Activities Disclosures
Amount of Gain (Loss) Recognized	180	(2,028)	(327)
Not Designated as Hedging Instruments \| Other contracts \| Other income
Derivative Instruments and Hedging Activities Disclosures
Amount of Gain (Loss) Recognized	(24)	51	17
OCI \| Designated as Hedging Instruments \| Cash Flow Hedging \| Interest rate contracts
Derivative Instruments and Hedging Activities Disclosures
Amount of Gain (Loss) Recognized	4,416	$ (611)	$ (328)
Derivative, Included Component, Gain (Loss) Recognized in Earnings	4,835
Amount of Gain (Loss) Recognized in Income on Derivatives (Amount Excluded from Effectiveness Testing)	$ (419)

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Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Excluding Compnonent, Net

+ References

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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
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109974929&loc=SL110061172-113977

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624171-113959

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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
-Paragraph 4A
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5618551-113959

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The portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments representing (a) the amount of the hedge ineffectiveness and (b) the amount, if any, excluded from the assessment of hedge effectiveness.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Topic 815
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-Section 50
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-URI http://asc.fasb.org/extlink&oid=109977999&loc=d3e76258-113986

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