Number of Loans and Leases Modified in TDRs and Total Recorded Investments and Unpaid Principal Balances (Detail) (Class of Financing Receivable, USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015 Contract	Mar. 31, 2014 Contract
Financing Receivable, Modifications [Line Items]
Number of Loans and Leases	59	36
Recorded Investment	$ 7.9	$ 4.2
Unpaid Principal Balance	11.0	4.5
Commercial
Financing Receivable, Modifications [Line Items]
Number of Loans and Leases	2	1
Recorded Investment	0.8	0.7
Unpaid Principal Balance	0.8	0.7
Commercial \| Commercial and Institutional
Financing Receivable, Modifications [Line Items]
Number of Loans and Leases	1
Recorded Investment	0.1
Unpaid Principal Balance	0.1
Commercial \| Commercial Real Estate Portfolio Segment
Financing Receivable, Modifications [Line Items]
Number of Loans and Leases	1	1
Recorded Investment	0.7	0.7
Unpaid Principal Balance	0.7	0.7
Personal
Financing Receivable, Modifications [Line Items]
Number of Loans and Leases	57	35
Recorded Investment	7.1	3.5
Unpaid Principal Balance	10.2	3.8
Personal \| Residential Real Estate
Financing Receivable, Modifications [Line Items]
Number of Loans and Leases	57	34
Recorded Investment	7.1	3.5
Unpaid Principal Balance	$ 10.2	$ 3.8
Personal \| Private Client
Financing Receivable, Modifications [Line Items]
Number of Loans and Leases		1

Financing receivable, modifications, unpaid principal balance.

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- Definition

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=35738203&loc=SL6953676-111524

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- Definition

The amount of the outstanding recorded investment related to 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 40

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=25495931&loc=d3e18845-111554

+ Details

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