(Narrative) (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) Loan	Sep. 30, 2014 USD ($)	Mar. 31, 2015 Loan	Dec. 31, 2014 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Collateral required on Residential real estate loan, lower limit	65.00%		65.00%
Collateral required on Residential real estate loan, upper limit	80.00%		80.00%
Draw period for credit line products			10 years
Other U.S. loans and non-U.S. loans, short duration advances	$ 929,200,000		$ 929,200,000			$ 1,500,000,000
Demand deposits	163,200,000		163,200,000			92,100,000
Held for Sale	335,300,000		335,300,000			2,500,000
Interest income that would have been recorded for nonperforming loans	2,000,000	$ 2,200,000	4,100,000	$ 7,100,000
Undrawn loan commitments and standby letters of credit	2,600,000		2,600,000			2,400,000
Total Loans and Leases	33,378,400,000		33,378,400,000			31,640,200,000
Unpaid principal balance	260,000,000		260,000,000			301,000,000
Foreclosed residential real estate properties with carrying value	6,900,000		6,900,000
Consumer loans with carrying value collateralized by residential real estate property	23,700,000		23,700,000
Leveraged leases residual value impairment			$ (17,800,000)
Lower Limit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Days contractually past due for interest and principal and the loan is not well-secured and in the process of collection			90 days
Upper Limit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Limit of individual homogeneous loans collective evaluation for impairment and excluded from impaired loan disclosures	250,000		$ 250,000
Equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Equity credit lines	$ 1,600,000,000		$ 1,600,000,000			1,800,000,000
Percentage of total equity credit lines	0.89		0.89
Nonperforming Financing Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans and Leases	$ 85,400,000		$ 85,400,000			82,700,000
Performing Financing Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans and Leases	36,900,000		$ 36,900,000			$ 68,600,000
Performing Financing Receivable | Lower Limit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Period for which troubled debt restructurings with modified terms is performing before ceasing to be classified as impaired loan			6 months
Troubled debt restructuring loans and leases receivable to Performing status			6 months
Residential Real Estate | Re-Defaulted
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans and Leases | Loan			3		4
Recorded Investment	$ 500,000		$ 500,000
Private Client | Re-Defaulted
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans and Leases | Loan			1