Loans and Leases (Narrative) (Details)	6 Months Ended	12 Months Ended
	Jun. 30, 2020 USD ($) loan	Dec. 31, 2019 USD ($) loan	Dec. 31, 2018 USD ($) loan	Mar. 31, 2019 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	$ 33,757,300,000	$ 31,409,600,000
Other U.S. loans and non-U.S. loans, short duration advances	1,400,000,000	1,100,000,000
Demand deposits	12,700,000	90,400,000
Financing receivable, nonaccrual troubled debt restructuring	58,600,000	54,900,000
Financing receivable, recorded investment	24,600,000	27,700,000	$ 4,600,000	$ 4,600,000
Financing receivable, troubled debt restructuring, commitment to lend	10,400,000	8,200,000
Foreclosed real estate properties, carrying value	900,000	3,200,000
Loans in process of foreclosure	11,800,000
Paycheck Protection Program
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	213,800,000
Loan processing fee	$ 2,500,000
Number of loans approved for forgiveness | loan	0
Lease Agreements
Accounts, Notes, Loans and Financing Receivable [Line Items]
Held for sale	$ 39,500,000	53,600,000
Mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Held for sale	0	$ 0
Residential Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, troubled debt restructuring, subsequent default, number of contracts | loan		0	2
Personal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	$ 17,987,500,000	$ 17,408,300,000
Personal | Residential Real Estate
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	80.00%
Loans and leases	$ 5,942,500,000	6,095,000,000.0
Personal | Home Equity Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Draw period for credit line products	10 years
Loans and leases	$ 384,700,000	$ 448,500,000
Percentage of total equity credit lines	97.00%	97.00%
COMMERCIAL
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	$ 15,769,800,000	$ 14,001,300,000
COMMERCIAL | Commercial and Institutional
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	10,745,800,000	$ 9,091,100,000
COMMERCIAL | Commercial and Institutional | Paycheck Protection Program
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	$ 213,800,000
Number of contracts | loan	1,081,000,000
Financing receivable, average balance per loan	$ 200,000