Revenue from Contracts with Clients (Revenue Disaggregated by Major Source) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Trust, Investment and Other Servicing Fees	$ 3,852.1	$ 3,753.7	$ 3,434.3
Foreign Exchange Trading Income	250.9	307.2	209.9
Treasury Management Fees	44.5	51.8	56.4
Security Commissions and Trading Income	103.6	98.3	89.6
Other Operating Income	145.5	127.5	157.5
Investment Security Gains (Losses), net	(1.4)	(1.0)	(1.6)
Total Other Noninterest Income	543.1	583.8
Total Noninterest Income	4,395.2	4,337.5	$ 3,946.1
Custody and Fund Administration
Disaggregation of Revenue [Line Items]
Trust, Investment and Other Servicing Fees	1,636.4	1,589.1
Investment Management and Advisory
Disaggregation of Revenue [Line Items]
Trust, Investment and Other Servicing Fees	1,930.6	1,862.6
Securities Lending
Disaggregation of Revenue [Line Items]
Trust, Investment and Other Servicing Fees	87.7	102.8
Other
Disaggregation of Revenue [Line Items]
Trust, Investment and Other Servicing Fees	$ 197.4	$ 199.2

Other Noninterest Income

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Revenues earned for buying and selling securities on behalf of clients and other fees including fees earned for transitioning assets between investment firms, fees earned for buying and selling interest rate protection products, and other fees.

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Fees earned from treasury management activities including disbursements and receivables management, funds transfer, and online reporting.

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Amount before tax of foreign currency transaction realized and unrealized gain (loss) recognized in the income statement.

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Amount of unrealized and realized gain (loss) on investment in marketable security, including other-than-temporary impairment (OTTI).

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The total amount of noninterest income which may be derived from: (1) fees and commissions; (2) premiums earned; (3) insurance policy charges; (4) the sale or disposal of assets; and (5) other sources not otherwise specified.

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Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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