Loans and Leases (Narrative) (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2017 USD ($) payment_period	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) payment_period Loan	Sep. 30, 2016 USD ($) Loan	Dec. 31, 2016 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	$ 1,300,000,000		$ 1,300,000,000		$ 1,400,000,000
Demand deposits	154,500,000		154,500,000		88,100,000
Loans classified as held for sale	0		0		13,400,000
Leases classified as held for sale	32,600,000		32,600,000		43,000,000
Interest income that would have been recorded for nonperforming loans	2,200,000	$ 2,100,000	7,000,000	$ 6,300,000
Undrawn loan commitments and standby letters of credit	4,600,000		4,600,000		2,300,000
Total loans and leases	33,336,100,000		$ 33,336,100,000		33,822,100,000
Performing status, minimum period of time			6 months
Unpaid principal balance	168,600,000		$ 168,600,000		199,800,000
Foreclosed residential real estate properties with carrying value	7,900,000		7,900,000
Consumer loans with carrying value collateralized by residential real estate property	16,600,000		16,600,000
Nonperforming Financing Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	74,500,000		74,500,000		85,200,000
Performing Financing Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	26,900,000		$ 26,900,000		42,400,000
Re-Defaulted | Residential Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans and Leases | Loan			1	1
Recorded investment	$ 100,000	$ 100,000	$ 100,000	$ 100,000
Unpaid principal balance			$ 200,000
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
Lower Limit | Performing Financing Receivable
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
Upper Limit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of payment periods | payment_period	6		6
Limit of individual homogeneous loans collective evaluation for impairment and excluded from impaired loan disclosures (less than)	$ 1,000,000		$ 1,000,000
Equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Equity credit lines	$ 1,000,000,000		$ 1,000,000,000		$ 1,200,000,000
Percentage of total equity credit lines	92.00%		92.00%		91.00%