Loans - Summary of Recorded Investments in TDRs by Class of Loan, Subsequently Defaulted (Detail) $ in Millions	12 Months Ended
Dec. 31, 2019 USD ($) contract	Dec. 31, 2018 USD ($) contract
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	27	38
Recorded Investment \| $	$ 10.9	$ 12.5
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	10	18
Recorded Investment \| $	$ 7.7	$ 10.2
Commercial [Member] \| Commercial Real Estate Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	0	0
Recorded Investment \| $	$ 0.0	$ 0.0
Commercial [Member] \| Commercial and Industrial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	2	12
Recorded Investment \| $	$ 2.4	$ 6.7
Commercial [Member] \| Equipment Financing [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	8	6
Recorded Investment \| $	$ 5.3	$ 3.5
Retail Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	17	20
Recorded Investment \| $	$ 3.2	$ 2.3
Retail Loans [Member] \| Residential Mortgage Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	5	7
Recorded Investment \| $	$ 2.2	$ 1.6
Retail Loans [Member] \| Home Equity Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	12	13
Recorded Investment \| $	$ 1.0	$ 0.7
Retail Loans [Member] \| Other Consumer [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	0	0
Recorded Investment \| $	$ 0.0	$ 0.0

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- Definition

Number of financing receivable contracts modified as troubled debt restructuring within previous 12 months, with subsequent payment default.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953682-111524

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- Definition

Amount of financing receivable modified as troubled debt restructuring within previous 12 months, with subsequent payment default.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953682-111524

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