Loans and Leases - Troubled Debt Restructurings (Detail) - Lease Financing, net $ in Millions	12 Months Ended
Dec. 31, 2017 USD ($) Contract	Dec. 31, 2016 USD ($) Contract
Financing Receivable, Modifications [Line Items]
Loans or leases modified in trouble debt restructuring \| Contract	74	89
Troubled debt restructurings, recorded investment	$ 24.5	$ 37.3
Troubled debt restructurings, unpaid principal balance	$ 26.5	$ 43.1
Commercial
Financing Receivable, Modifications [Line Items]
Loans or leases modified in trouble debt restructuring \| Contract	5	14
Troubled debt restructurings, recorded investment	$ 2.2	$ 13.0
Troubled debt restructurings, unpaid principal balance	$ 3.2	$ 17.5
Commercial \| Commercial and Institutional
Financing Receivable, Modifications [Line Items]
Loans or leases modified in trouble debt restructuring \| Contract	3	7
Troubled debt restructurings, recorded investment	$ 0.4	$ 4.3
Troubled debt restructurings, unpaid principal balance	$ 1.4	$ 6.5
Commercial \| Real Estate
Financing Receivable, Modifications [Line Items]
Loans or leases modified in trouble debt restructuring \| Contract	2	7
Troubled debt restructurings, recorded investment	$ 1.8	$ 8.7
Troubled debt restructurings, unpaid principal balance	$ 1.8	$ 11.0
Personal
Financing Receivable, Modifications [Line Items]
Loans or leases modified in trouble debt restructuring \| Contract	69	75
Troubled debt restructurings, recorded investment	$ 22.3	$ 24.3
Troubled debt restructurings, unpaid principal balance	$ 23.3	$ 25.6
Personal \| Real Estate
Financing Receivable, Modifications [Line Items]
Loans or leases modified in trouble debt restructuring \| Contract	66	73
Troubled debt restructurings, recorded investment	$ 22.1	$ 22.2
Troubled debt restructurings, unpaid principal balance	$ 22.8	$ 23.5
Personal \| Private Client
Financing Receivable, Modifications [Line Items]
Loans or leases modified in trouble debt restructuring \| Contract	3	2
Troubled debt restructurings, recorded investment	$ 0.2	$ 2.1
Troubled debt restructurings, unpaid principal balance	$ 0.5	$ 2.1

Financing Receivable, Modifications, Recorded Investment, Modified During Period

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Financing Receivable, Modifications, Unpaid Principal Balance

+ References

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Number of financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953676-111524

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