Loans and Leases (Narrative) (Details)	3 Months Ended		12 Months Ended
	Mar. 31, 2016 USD ($) Loan	Mar. 31, 2015 USD ($)	Dec. 31, 2015 USD ($) Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Collateral required on Residential real estate loan, lower limit	65.00%
Collateral required on Residential real estate loan, upper limit	75.00%
Draw period for credit line products	10 years
Other U.S. loans and non-U.S. loans, short duration advances	$ 1,000,000,000		$ 719,500,000
Demand deposits	58,100,000		75,400,000
Loans classified as held for sale	1,400,000		12,000,000
Leases classified as held for sale	134,200,000		112,300,000
Interest income that would have been recorded for nonperforming loans	2,100,000	$ 2,100,000
Undrawn loan commitments and standby letters of credit	2,400,000		3,100,000
Total Loans and Leases	34,144,900,000		33,180,900,000
Unpaid principal balance	208,000,000		209,800,000
Foreclosed residential real estate properties with carrying value	10,000,000
Consumer loans with carrying value collateralized by residential real estate property	$ 23,800,000
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	$ 1,000,000
Equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Equity credit lines	$ 1,400,000,000		$ 1,500,000,000
Percentage of total equity credit lines	89.00%		89.00%
Nonperforming Financing Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans and Leases	$ 83,400,000		$ 79,200,000
Performing Financing Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans and Leases	$ 40,800,000		$ 37,900,000
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
Residential Real Estate | Re-Defaulted
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans and Leases | Loan	1		4
Recorded Investment	$ 100,000		$ 700,000