Derivative Instruments and Other Hedging Activities - Effect of Hedging Instruments on Consolidated Financial Statements (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Designated as Hedging Instruments \| Cash Flow Hedging \| Interest rate contracts \| Interest expense
Derivative Instruments and Hedging Activities Disclosures
Amount of gain (loss) recognized	$ (78)	$ (40)	$ (305)	$ (156)
Derivative, included component, gain (loss) recognized in earnings	179	(40)	110	(156)
Amount of gain (loss) recognized in income on derivatives (amount excluded from effectiveness testing)	(257)	0	(415)	0
Derivative instruments, gain (loss) recognized in income, ineffective portion and amount excluded from effectiveness testing, net	0	0	0	0
Derivative instruments, gain (loss) recognized in income, ineffective portion and amount excluded from effectiveness testing, included component net	0	0	0	0
Derivative instruments, gain (loss) recognized in income, ineffective portion and amount excluded from effectiveness testing, excluding component, net	0	0	0	0
Not Designated as Hedging Instruments
Derivative Instruments and Hedging Activities Disclosures
Amount of gain (loss) recognized	1,045	2,206	3,876	7,292
Not Designated as Hedging Instruments \| Interest rate contracts \| Commission income
Derivative Instruments and Hedging Activities Disclosures
Amount of gain (loss) recognized	2,513	1,458	6,694	2,507
Not Designated as Hedging Instruments \| Foreign exchange contracts \| Commission income
Derivative Instruments and Hedging Activities Disclosures
Amount of gain (loss) recognized	1	5	6	10
Not Designated as Hedging Instruments \| Forward sales contracts \| Mortgage income
Derivative Instruments and Hedging Activities Disclosures
Amount of gain (loss) recognized	(3,111)	228	(6,320)	3,615
Not Designated as Hedging Instruments \| Written and purchased options \| Mortgage income
Derivative Instruments and Hedging Activities Disclosures
Amount of gain (loss) recognized	1,660	517	3,523	1,165
Not Designated as Hedging Instruments \| Other contracts \| Commission income
Derivative Instruments and Hedging Activities Disclosures
Amount of gain (loss) recognized	(18)	(2)	(27)	(5)
OCI \| Designated as Hedging Instruments \| Cash Flow Hedging \| Interest rate contracts
Derivative Instruments and Hedging Activities Disclosures
Amount of gain (loss) recognized	4,441	1,395	2,256	3,944
Derivative, included component, gain (loss) recognized in earnings	5,982	1,395	2,884	3,944
Amount of gain (loss) recognized in income on derivatives (amount excluded from effectiveness testing)	$ (1,541)	$ 0	$ (628)	$ 0

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

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

+ References

No definition available.

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

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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
-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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- Definition

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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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

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
-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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-Publisher FASB
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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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