Loans and Leases (Loans and Leases) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	$ 31,354.0	$ 32,592.2
Allowance for Credit Losses Assigned to Loans and Leases	(119.6)	(131.2)
Net Loans and Leases	31,234.4	32,461.0
Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	13,874.1	14,558.0
Commercial \| Commercial and Institutional
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	8,695.5	9,042.2
Commercial \| Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	3,288.5	3,482.7
Commercial \| Non-U.S.
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	1,376.0	1,538.5
Commercial \| Lease Financing, net
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	154.8	229.2
Commercial \| Other
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	359.3	265.4
Personal
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	17,479.9	18,034.2
Personal \| Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	6,680.9	7,247.6
Personal \| Private Client
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	10,764.3	10,753.1
Personal \| Other
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	$ 34.7	$ 33.5

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. 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.

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Amount after allowance and 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 and loans held for sale.

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