Loan and Lease Segment and Class Balances Segregated by Borrower Ratings into "1 to 3", "4 to 5" and "6 to 9" (Watch List) Categories (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	$ 29,542.7	$ 29,063.9
Commercial
Financing Receivable, Recorded Investment [Line Items]
Commercial and Institutional	7,316.5	6,918.7
Commercial Real Estate	3,002.4	2,981.7
Lease Financing, net	1,011.6	978.8
Non-U.S.	1,038.1	1,057.5
Other	631.0	417.6
Total Loans and Leases	12,999.6	12,354.3
Personal
Financing Receivable, Recorded Investment [Line Items]
Residential Real Estate	10,435.3	10,708.9
Private Client	5,751.4	5,651.4
Other	356.4	349.3
Total Loans and Leases	16,543.1	16,709.6
1 to 3 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	13,192.4	12,567.0
1 to 3 Category \| Commercial
Financing Receivable, Recorded Investment [Line Items]
Commercial and Institutional	4,154.8	3,681.8
Commercial Real Estate	970.4	1,247.1
Lease Financing, net	703.1	547.7
Non-U.S.	629.9	519.0
Other	273.3	241.4
Total Loans and Leases	6,731.5	6,237.0
1 to 3 Category \| Personal
Financing Receivable, Recorded Investment [Line Items]
Residential Real Estate	2,984.0	2,777.1
Private Client	3,309.0	3,390.6
Other	167.9	162.3
Total Loans and Leases	6,460.9	6,330.0
4 to 5 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	15,436.4	15,556.0
4 to 5 Category \| Commercial
Financing Receivable, Recorded Investment [Line Items]
Commercial and Institutional	2,959.6	3,029.1
Commercial Real Estate	1,766.0	1,467.2
Lease Financing, net	302.3	422.3
Non-U.S.	405.3	527.3
Other	357.7	176.2
Total Loans and Leases	5,790.9	5,622.1
4 to 5 Category \| Personal
Financing Receivable, Recorded Investment [Line Items]
Residential Real Estate	7,037.7	7,501.0
Private Client	2,419.3	2,245.9
Other	188.5	187.0
Total Loans and Leases	9,645.5	9,933.9
6 to 9 Category (Watch List)
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	913.9	940.9
6 to 9 Category (Watch List) \| Commercial
Financing Receivable, Recorded Investment [Line Items]
Commercial and Institutional	202.1	207.8
Commercial Real Estate	266.0	267.4
Lease Financing, net	6.2	8.8
Non-U.S.	2.9	11.2
Total Loans and Leases	477.2	495.2
6 to 9 Category (Watch List) \| Personal
Financing Receivable, Recorded Investment [Line Items]
Residential Real Estate	413.6	430.8
Private Client	23.1	14.9
Total Loans and Leases	$ 436.7	$ 445.7

Amount before allowance of commercial leases and leveraged lease transactions where the entity is long-term creditor. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes leases covered under loss sharing agreements.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 13

-Paragraph 6

-Subparagraph b(iii)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Statement of Position (SOP)

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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-Publisher AICPA

-Name Audit and Accounting Guide (AAG)

-Number AAG-DEP

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 7

-Subparagraph a, b

-Article 9

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Leveraged Lease

-URI http://asc.fasb.org/extlink&oid=6516780

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 13

-Paragraph 42

-Subparagraph b, c

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

- Definition

Reflects the net carrying amount of foreign loans and leases held in portfolio, after deducting deferred income, but before deducting the allowance for losses on foreign loans and leases.

+ References+ Details

- Definition

Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

+ References+ Details

- Definition

Amount before allowance of other loans and leases not otherwise specified in the taxonomy. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

+ References+ Details

- Definition

Amount before allowance of loans issued to agricultural, commercial and industrial, and financial institutions. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans covered under loss sharing agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-Publisher SEC

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

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Reference 5: http://www.xbrl.org/2003/role/presentationRef

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Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher OTS

-Name Federal Regulation (FR)

-Number Title 12

-Section 563c.102

-Paragraph 8

-Subparagraph b(iv)

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-Subsection I

-LegacyDoc This is a non-GAAP reference that was included in the 2009 taxonomy. It will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher OTS

-Name Federal Regulation (FR)

-Number Title 12

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-Paragraph 8

-Subparagraph c(iv)

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-Subsection I

-LegacyDoc This is a non-GAAP reference that was included in the 2009 taxonomy. It will be removed from future versions of this taxonomy.

+ Details

- Definition

Amount before allowance of commercial loans issued to businesses to acquire, develop, construct, improve, or refinance land or building. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans covered under loss sharing agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

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-Article 9

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-Name Accounting Standards Codification

-Topic 944

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-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.1(c))

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Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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Reference 7: http://www.xbrl.org/2003/role/presentationRef

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details